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loopnode.cpp 
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/*
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 * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "ci/ciMethodData.hpp"
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#include "compiler/compileLog.hpp"
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#include "gc/shared/barrierSet.hpp"
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#include "gc/shared/c2/barrierSetC2.hpp"
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#include "libadt/vectset.hpp"
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#include "memory/allocation.inline.hpp"
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#include "memory/resourceArea.hpp"
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#include "opto/addnode.hpp"
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#include "opto/arraycopynode.hpp"
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#include "opto/callnode.hpp"
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#include "opto/castnode.hpp"
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#include "opto/connode.hpp"
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#include "opto/convertnode.hpp"
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#include "opto/divnode.hpp"
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#include "opto/idealGraphPrinter.hpp"
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#include "opto/loopnode.hpp"
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#include "opto/movenode.hpp"
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#include "opto/mulnode.hpp"
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#include "opto/opaquenode.hpp"
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#include "opto/predicates.hpp"
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#include "opto/rootnode.hpp"
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#include "opto/runtime.hpp"
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#include "opto/vectorization.hpp"
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#include "runtime/sharedRuntime.hpp"
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#include "utilities/checkedCast.hpp"
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#include "utilities/powerOfTwo.hpp"
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//=============================================================================
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//--------------------------is_cloop_ind_var-----------------------------------
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// Determine if a node is a counted loop induction variable.
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// NOTE: The method is declared in "node.hpp".
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bool Node::is_cloop_ind_var() const {
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  return (is_Phi() &&
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          as_Phi()->region()->is_CountedLoop() &&
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          as_Phi()->region()->as_CountedLoop()->phi() == this);
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}
62

63
//=============================================================================
64
//------------------------------dump_spec--------------------------------------
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// Dump special per-node info
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#ifndef PRODUCT
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void LoopNode::dump_spec(outputStream *st) const {
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  RegionNode::dump_spec(st);
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  if (is_inner_loop()) st->print( "inner " );
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  if (is_partial_peel_loop()) st->print( "partial_peel " );
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  if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
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}
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#endif
74

75
//------------------------------is_valid_counted_loop-------------------------
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bool LoopNode::is_valid_counted_loop(BasicType bt) const {
77
  if (is_BaseCountedLoop() && as_BaseCountedLoop()->bt() == bt) {
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    BaseCountedLoopNode*    l  = as_BaseCountedLoop();
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    BaseCountedLoopEndNode* le = l->loopexit_or_null();
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    if (le != nullptr &&
81
        le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
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      Node* phi  = l->phi();
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      Node* exit = le->proj_out_or_null(0 /* false */);
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      if (exit != nullptr && exit->Opcode() == Op_IfFalse &&
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          phi != nullptr && phi->is_Phi() &&
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          phi->in(LoopNode::LoopBackControl) == l->incr() &&
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          le->loopnode() == l && le->stride_is_con()) {
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        return true;
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      }
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    }
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  }
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  return false;
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}
94

95
//------------------------------get_early_ctrl---------------------------------
96
// Compute earliest legal control
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Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
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  assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
99
  uint i;
100
  Node *early;
101
  if (n->in(0) && !n->is_expensive()) {
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    early = n->in(0);
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    if (!early->is_CFG()) // Might be a non-CFG multi-def
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      early = get_ctrl(early);        // So treat input as a straight data input
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    i = 1;
106
  } else {
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    early = get_ctrl(n->in(1));
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    i = 2;
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  }
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  uint e_d = dom_depth(early);
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  assert( early, "" );
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  for (; i < n->req(); i++) {
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    Node *cin = get_ctrl(n->in(i));
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    assert( cin, "" );
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    // Keep deepest dominator depth
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    uint c_d = dom_depth(cin);
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    if (c_d > e_d) {           // Deeper guy?
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      early = cin;              // Keep deepest found so far
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      e_d = c_d;
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    } else if (c_d == e_d &&    // Same depth?
121
               early != cin) { // If not equal, must use slower algorithm
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      // If same depth but not equal, one _must_ dominate the other
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      // and we want the deeper (i.e., dominated) guy.
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      Node *n1 = early;
125
      Node *n2 = cin;
126
      while (1) {
127
        n1 = idom(n1);          // Walk up until break cycle
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        n2 = idom(n2);
129
        if (n1 == cin ||        // Walked early up to cin
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            dom_depth(n2) < c_d)
131
          break;                // early is deeper; keep him
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        if (n2 == early ||      // Walked cin up to early
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            dom_depth(n1) < c_d) {
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          early = cin;          // cin is deeper; keep him
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          break;
136
        }
137
      }
138
      e_d = dom_depth(early);   // Reset depth register cache
139
    }
140
  }
141

142
  // Return earliest legal location
143
  assert(early == find_non_split_ctrl(early), "unexpected early control");
144

145
  if (n->is_expensive() && !_verify_only && !_verify_me) {
146
    assert(n->in(0), "should have control input");
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    early = get_early_ctrl_for_expensive(n, early);
148
  }
149

150
  return early;
151
}
152

153
//------------------------------get_early_ctrl_for_expensive---------------------------------
154
// Move node up the dominator tree as high as legal while still beneficial
155
Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
156
  assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
157
  assert(OptimizeExpensiveOps, "optimization off?");
158

159
  Node* ctl = n->in(0);
160
  assert(ctl->is_CFG(), "expensive input 0 must be cfg");
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  uint min_dom_depth = dom_depth(earliest);
162
#ifdef ASSERT
163
  if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
164
    dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
165
    assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
166
  }
167
#endif
168
  if (dom_depth(ctl) < min_dom_depth) {
169
    return earliest;
170
  }
171

172
  while (true) {
173
    Node* next = ctl;
174
    // Moving the node out of a loop on the projection of an If
175
    // confuses Loop Predication. So, once we hit a loop in an If branch
176
    // that doesn't branch to an UNC, we stop. The code that process
177
    // expensive nodes will notice the loop and skip over it to try to
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    // move the node further up.
179
    if (ctl->is_CountedLoop() && ctl->in(1) != nullptr && ctl->in(1)->in(0) != nullptr && ctl->in(1)->in(0)->is_If()) {
180
      if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern()) {
181
        break;
182
      }
183
      next = idom(ctl->in(1)->in(0));
184
    } else if (ctl->is_Proj()) {
185
      // We only move it up along a projection if the projection is
186
      // the single control projection for its parent: same code path,
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      // if it's a If with UNC or fallthrough of a call.
188
      Node* parent_ctl = ctl->in(0);
189
      if (parent_ctl == nullptr) {
190
        break;
191
      } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != nullptr) {
192
        next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
193
      } else if (parent_ctl->is_If()) {
194
        if (!ctl->as_Proj()->is_uncommon_trap_if_pattern()) {
195
          break;
196
        }
197
        assert(idom(ctl) == parent_ctl, "strange");
198
        next = idom(parent_ctl);
199
      } else if (ctl->is_CatchProj()) {
200
        if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
201
          break;
202
        }
203
        assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
204
        next = parent_ctl->in(0)->in(0)->in(0);
205
      } else {
206
        // Check if parent control has a single projection (this
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        // control is the only possible successor of the parent
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        // control). If so, we can try to move the node above the
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        // parent control.
210
        int nb_ctl_proj = 0;
211
        for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
212
          Node *p = parent_ctl->fast_out(i);
213
          if (p->is_Proj() && p->is_CFG()) {
214
            nb_ctl_proj++;
215
            if (nb_ctl_proj > 1) {
216
              break;
217
            }
218
          }
219
        }
220

221
        if (nb_ctl_proj > 1) {
222
          break;
223
        }
224
        assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
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               BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
226
        assert(idom(ctl) == parent_ctl, "strange");
227
        next = idom(parent_ctl);
228
      }
229
    } else {
230
      next = idom(ctl);
231
    }
232
    if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
233
      break;
234
    }
235
    ctl = next;
236
  }
237

238
  if (ctl != n->in(0)) {
239
    _igvn.replace_input_of(n, 0, ctl);
240
    _igvn.hash_insert(n);
241
  }
242

243
  return ctl;
244
}
245

246

247
//------------------------------set_early_ctrl---------------------------------
248
// Set earliest legal control
249
void PhaseIdealLoop::set_early_ctrl(Node* n, bool update_body) {
250
  Node *early = get_early_ctrl(n);
251

252
  // Record earliest legal location
253
  set_ctrl(n, early);
254
  IdealLoopTree *loop = get_loop(early);
255
  if (update_body && loop->_child == nullptr) {
256
    loop->_body.push(n);
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  }
258
}
259

260
//------------------------------set_subtree_ctrl-------------------------------
261
// set missing _ctrl entries on new nodes
262
void PhaseIdealLoop::set_subtree_ctrl(Node* n, bool update_body) {
263
  // Already set?  Get out.
264
  if (_loop_or_ctrl[n->_idx]) return;
265
  // Recursively set _loop_or_ctrl array to indicate where the Node goes
266
  uint i;
267
  for (i = 0; i < n->req(); ++i) {
268
    Node *m = n->in(i);
269
    if (m && m != C->root()) {
270
      set_subtree_ctrl(m, update_body);
271
    }
272
  }
273

274
  // Fixup self
275
  set_early_ctrl(n, update_body);
276
}
277

278
IdealLoopTree* PhaseIdealLoop::insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift) {
279
  IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
280
  IdealLoopTree* parent = loop->_parent;
281
  IdealLoopTree* sibling = parent->_child;
282
  if (sibling == loop) {
283
    parent->_child = outer_ilt;
284
  } else {
285
    while (sibling->_next != loop) {
286
      sibling = sibling->_next;
287
    }
288
    sibling->_next = outer_ilt;
289
  }
290
  outer_ilt->_next = loop->_next;
291
  outer_ilt->_parent = parent;
292
  outer_ilt->_child = loop;
293
  outer_ilt->_nest = loop->_nest;
294
  loop->_parent = outer_ilt;
295
  loop->_next = nullptr;
296
  loop->_nest++;
297
  assert(loop->_nest <= SHRT_MAX, "sanity");
298
  return outer_ilt;
299
}
300

301
// Create a skeleton strip mined outer loop: a Loop head before the
302
// inner strip mined loop, a safepoint and an exit condition guarded
303
// by an opaque node after the inner strip mined loop with a backedge
304
// to the loop head. The inner strip mined loop is left as it is. Only
305
// once loop optimizations are over, do we adjust the inner loop exit
306
// condition to limit its number of iterations, set the outer loop
307
// exit condition and add Phis to the outer loop head. Some loop
308
// optimizations that operate on the inner strip mined loop need to be
309
// aware of the outer strip mined loop: loop unswitching needs to
310
// clone the outer loop as well as the inner, unrolling needs to only
311
// clone the inner loop etc. No optimizations need to change the outer
312
// strip mined loop as it is only a skeleton.
313
IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
314
                                                             IdealLoopTree* loop, float cl_prob, float le_fcnt,
315
                                                             Node*& entry_control, Node*& iffalse) {
316
  Node* outer_test = _igvn.intcon(0);
317
  set_ctrl(outer_test, C->root());
318
  Node *orig = iffalse;
319
  iffalse = iffalse->clone();
320
  _igvn.register_new_node_with_optimizer(iffalse);
321
  set_idom(iffalse, idom(orig), dom_depth(orig));
322

323
  IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
324
  Node *outer_ift = new IfTrueNode (outer_le);
325
  Node* outer_iff = orig;
326
  _igvn.replace_input_of(outer_iff, 0, outer_le);
327

328
  LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
329
  entry_control = outer_l;
330

331
  IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_l, outer_ift);
332

333
  set_loop(iffalse, outer_ilt);
334
  // When this code runs, loop bodies have not yet been populated.
335
  const bool body_populated = false;
336
  register_control(outer_le, outer_ilt, iffalse, body_populated);
337
  register_control(outer_ift, outer_ilt, outer_le, body_populated);
338
  set_idom(outer_iff, outer_le, dom_depth(outer_le));
339
  _igvn.register_new_node_with_optimizer(outer_l);
340
  set_loop(outer_l, outer_ilt);
341
  set_idom(outer_l, init_control, dom_depth(init_control)+1);
342

343
  return outer_ilt;
344
}
345

346
void PhaseIdealLoop::insert_loop_limit_check_predicate(ParsePredicateSuccessProj* loop_limit_check_parse_proj,
347
                                                       Node* cmp_limit, Node* bol) {
348
  assert(loop_limit_check_parse_proj->in(0)->is_ParsePredicate(), "must be parse predicate");
349
  Node* new_predicate_proj = create_new_if_for_predicate(loop_limit_check_parse_proj, nullptr,
350
                                                         Deoptimization::Reason_loop_limit_check,
351
                                                         Op_If);
352
  Node* iff = new_predicate_proj->in(0);
353
  cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
354
  bol = _igvn.register_new_node_with_optimizer(bol);
355
  set_subtree_ctrl(bol, false);
356
  _igvn.replace_input_of(iff, 1, bol);
357

358
#ifndef PRODUCT
359
  // report that the loop predication has been actually performed
360
  // for this loop
361
  if (TraceLoopLimitCheck) {
362
    tty->print_cr("Counted Loop Limit Check generated:");
363
    debug_only( bol->dump(2); )
364
  }
365
#endif
366
}
367

368
Node* PhaseIdealLoop::loop_exit_control(Node* x, IdealLoopTree* loop) {
369
  // Counted loop head must be a good RegionNode with only 3 not null
370
  // control input edges: Self, Entry, LoopBack.
371
  if (x->in(LoopNode::Self) == nullptr || x->req() != 3 || loop->_irreducible) {
372
    return nullptr;
373
  }
374
  Node *init_control = x->in(LoopNode::EntryControl);
375
  Node *back_control = x->in(LoopNode::LoopBackControl);
376
  if (init_control == nullptr || back_control == nullptr) {   // Partially dead
377
    return nullptr;
378
  }
379
  // Must also check for TOP when looking for a dead loop
380
  if (init_control->is_top() || back_control->is_top()) {
381
    return nullptr;
382
  }
383

384
  // Allow funny placement of Safepoint
385
  if (back_control->Opcode() == Op_SafePoint) {
386
    back_control = back_control->in(TypeFunc::Control);
387
  }
388

389
  // Controlling test for loop
390
  Node *iftrue = back_control;
391
  uint iftrue_op = iftrue->Opcode();
392
  if (iftrue_op != Op_IfTrue &&
393
      iftrue_op != Op_IfFalse) {
394
    // I have a weird back-control.  Probably the loop-exit test is in
395
    // the middle of the loop and I am looking at some trailing control-flow
396
    // merge point.  To fix this I would have to partially peel the loop.
397
    return nullptr; // Obscure back-control
398
  }
399

400
  // Get boolean guarding loop-back test
401
  Node *iff = iftrue->in(0);
402
  if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) {
403
    return nullptr;
404
  }
405
  return iftrue;
406
}
407

408
Node* PhaseIdealLoop::loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob) {
409
  Node* iftrue = back_control;
410
  uint iftrue_op = iftrue->Opcode();
411
  Node* iff = iftrue->in(0);
412
  BoolNode* test = iff->in(1)->as_Bool();
413
  bt = test->_test._test;
414
  cl_prob = iff->as_If()->_prob;
415
  if (iftrue_op == Op_IfFalse) {
416
    bt = BoolTest(bt).negate();
417
    cl_prob = 1.0 - cl_prob;
418
  }
419
  // Get backedge compare
420
  Node* cmp = test->in(1);
421
  if (!cmp->is_Cmp()) {
422
    return nullptr;
423
  }
424

425
  // Find the trip-counter increment & limit.  Limit must be loop invariant.
426
  incr  = cmp->in(1);
427
  limit = cmp->in(2);
428

429
  // ---------
430
  // need 'loop()' test to tell if limit is loop invariant
431
  // ---------
432

433
  if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
434
    Node* tmp = incr;            // Then reverse order into the CmpI
435
    incr = limit;
436
    limit = tmp;
437
    bt = BoolTest(bt).commute(); // And commute the exit test
438
  }
439
  if (is_member(loop, get_ctrl(limit))) { // Limit must be loop-invariant
440
    return nullptr;
441
  }
442
  if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
443
    return nullptr;
444
  }
445
  return cmp;
446
}
447

448
Node* PhaseIdealLoop::loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr) {
449
  if (incr->is_Phi()) {
450
    if (incr->as_Phi()->region() != x || incr->req() != 3) {
451
      return nullptr; // Not simple trip counter expression
452
    }
453
    phi_incr = incr;
454
    incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
455
    if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
456
      return nullptr;
457
    }
458
  }
459
  return incr;
460
}
461

462
Node* PhaseIdealLoop::loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi) {
463
  assert(incr->Opcode() == Op_AddI || incr->Opcode() == Op_AddL, "caller resp.");
464
  // Get merge point
465
  xphi = incr->in(1);
466
  Node *stride = incr->in(2);
467
  if (!stride->is_Con()) {     // Oops, swap these
468
    if (!xphi->is_Con()) {     // Is the other guy a constant?
469
      return nullptr;          // Nope, unknown stride, bail out
470
    }
471
    Node *tmp = xphi;          // 'incr' is commutative, so ok to swap
472
    xphi = stride;
473
    stride = tmp;
474
  }
475
  return stride;
476
}
477

478
PhiNode* PhaseIdealLoop::loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop) {
479
  if (!xphi->is_Phi()) {
480
    return nullptr; // Too much math on the trip counter
481
  }
482
  if (phi_incr != nullptr && phi_incr != xphi) {
483
    return nullptr;
484
  }
485
  PhiNode *phi = xphi->as_Phi();
486

487
  // Phi must be of loop header; backedge must wrap to increment
488
  if (phi->region() != x) {
489
    return nullptr;
490
  }
491
  return phi;
492
}
493

494
static int check_stride_overflow(jlong final_correction, const TypeInteger* limit_t, BasicType bt) {
495
  if (final_correction > 0) {
496
    if (limit_t->lo_as_long() > (max_signed_integer(bt) - final_correction)) {
497
      return -1;
498
    }
499
    if (limit_t->hi_as_long() > (max_signed_integer(bt) - final_correction)) {
500
      return 1;
501
    }
502
  } else {
503
    if (limit_t->hi_as_long() < (min_signed_integer(bt) - final_correction)) {
504
      return -1;
505
    }
506
    if (limit_t->lo_as_long() < (min_signed_integer(bt) - final_correction)) {
507
      return 1;
508
    }
509
  }
510
  return 0;
511
}
512

513
static bool condition_stride_ok(BoolTest::mask bt, jlong stride_con) {
514
  // If the condition is inverted and we will be rolling
515
  // through MININT to MAXINT, then bail out.
516
  if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
517
      // Odd stride
518
      (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
519
      // Count down loop rolls through MAXINT
520
      ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
521
      // Count up loop rolls through MININT
522
      ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
523
    return false; // Bail out
524
  }
525
  return true;
526
}
527

528
Node* PhaseIdealLoop::loop_nest_replace_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head,
529
                                           BasicType bt) {
530
  Node* iv_as_long;
531
  if (bt == T_LONG) {
532
    iv_as_long = new ConvI2LNode(inner_iv, TypeLong::INT);
533
    register_new_node(iv_as_long, inner_head);
534
  } else {
535
    iv_as_long = inner_iv;
536
  }
537
  Node* iv_replacement = AddNode::make(outer_phi, iv_as_long, bt);
538
  register_new_node(iv_replacement, inner_head);
539
  for (DUIterator_Last imin, i = iv_to_replace->last_outs(imin); i >= imin;) {
540
    Node* u = iv_to_replace->last_out(i);
541
#ifdef ASSERT
542
    if (!is_dominator(inner_head, ctrl_or_self(u))) {
543
      assert(u->is_Phi(), "should be a Phi");
544
      for (uint j = 1; j < u->req(); j++) {
545
        if (u->in(j) == iv_to_replace) {
546
          assert(is_dominator(inner_head, u->in(0)->in(j)), "iv use above loop?");
547
        }
548
      }
549
    }
550
#endif
551
    _igvn.rehash_node_delayed(u);
552
    int nb = u->replace_edge(iv_to_replace, iv_replacement, &_igvn);
553
    i -= nb;
554
  }
555
  return iv_replacement;
556
}
557

558
// Add a Parse Predicate with an uncommon trap on the failing/false path. Normal control will continue on the true path.
559
void PhaseIdealLoop::add_parse_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop,
560
                                         SafePointNode* sfpt) {
561
  if (!C->too_many_traps(reason)) {
562
    ParsePredicateNode* parse_predicate = new ParsePredicateNode(inner_head->in(LoopNode::EntryControl), reason, &_igvn);
563
    register_control(parse_predicate, loop, inner_head->in(LoopNode::EntryControl));
564
    Node* if_false = new IfFalseNode(parse_predicate);
565
    register_control(if_false, _ltree_root, parse_predicate);
566
    Node* if_true = new IfTrueNode(parse_predicate);
567
    register_control(if_true, loop, parse_predicate);
568

569
    int trap_request = Deoptimization::make_trap_request(reason, Deoptimization::Action_maybe_recompile);
570
    address call_addr = SharedRuntime::uncommon_trap_blob()->entry_point();
571
    const TypePtr* no_memory_effects = nullptr;
572
    JVMState* jvms = sfpt->jvms();
573
    CallNode* unc = new CallStaticJavaNode(OptoRuntime::uncommon_trap_Type(), call_addr, "uncommon_trap",
574
                                           no_memory_effects);
575

576
    Node* mem = nullptr;
577
    Node* i_o = nullptr;
578
    if (sfpt->is_Call()) {
579
      mem = sfpt->proj_out(TypeFunc::Memory);
580
      i_o = sfpt->proj_out(TypeFunc::I_O);
581
    } else {
582
      mem = sfpt->memory();
583
      i_o = sfpt->i_o();
584
    }
585

586
    Node *frame = new ParmNode(C->start(), TypeFunc::FramePtr);
587
    register_new_node(frame, C->start());
588
    Node *ret = new ParmNode(C->start(), TypeFunc::ReturnAdr);
589
    register_new_node(ret, C->start());
590

591
    unc->init_req(TypeFunc::Control, if_false);
592
    unc->init_req(TypeFunc::I_O, i_o);
593
    unc->init_req(TypeFunc::Memory, mem); // may gc ptrs
594
    unc->init_req(TypeFunc::FramePtr, frame);
595
    unc->init_req(TypeFunc::ReturnAdr, ret);
596
    unc->init_req(TypeFunc::Parms+0, _igvn.intcon(trap_request));
597
    unc->set_cnt(PROB_UNLIKELY_MAG(4));
598
    unc->copy_call_debug_info(&_igvn, sfpt);
599

600
    for (uint i = TypeFunc::Parms; i < unc->req(); i++) {
601
      set_subtree_ctrl(unc->in(i), false);
602
    }
603
    register_control(unc, _ltree_root, if_false);
604

605
    Node* ctrl = new ProjNode(unc, TypeFunc::Control);
606
    register_control(ctrl, _ltree_root, unc);
607
    Node* halt = new HaltNode(ctrl, frame, "uncommon trap returned which should never happen" PRODUCT_ONLY(COMMA /*reachable*/false));
608
    register_control(halt, _ltree_root, ctrl);
609
    _igvn.add_input_to(C->root(), halt);
610

611
    _igvn.replace_input_of(inner_head, LoopNode::EntryControl, if_true);
612
    set_idom(inner_head, if_true, dom_depth(inner_head));
613
  }
614
}
615

616
// Find a safepoint node that dominates the back edge. We need a
617
// SafePointNode so we can use its jvm state to create empty
618
// predicates.
619
static bool no_side_effect_since_safepoint(Compile* C, Node* x, Node* mem, MergeMemNode* mm, PhaseIdealLoop* phase) {
620
  SafePointNode* safepoint = nullptr;
621
  for (DUIterator_Fast imax, i = x->fast_outs(imax); i < imax; i++) {
622
    Node* u = x->fast_out(i);
623
    if (u->is_memory_phi()) {
624
      Node* m = u->in(LoopNode::LoopBackControl);
625
      if (u->adr_type() == TypePtr::BOTTOM) {
626
        if (m->is_MergeMem() && mem->is_MergeMem()) {
627
          if (m != mem DEBUG_ONLY(|| true)) {
628
            // MergeMemStream can modify m, for example to adjust the length to mem.
629
            // This is unfortunate, and probably unnecessary. But as it is, we need
630
            // to add m to the igvn worklist, else we may have a modified node that
631
            // is not on the igvn worklist.
632
            phase->igvn()._worklist.push(m);
633
            for (MergeMemStream mms(m->as_MergeMem(), mem->as_MergeMem()); mms.next_non_empty2(); ) {
634
              if (!mms.is_empty()) {
635
                if (mms.memory() != mms.memory2()) {
636
                  return false;
637
                }
638
#ifdef ASSERT
639
                if (mms.alias_idx() != Compile::AliasIdxBot) {
640
                  mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
641
                }
642
#endif
643
              }
644
            }
645
          }
646
        } else if (mem->is_MergeMem()) {
647
          if (m != mem->as_MergeMem()->base_memory()) {
648
            return false;
649
          }
650
        } else {
651
          return false;
652
        }
653
      } else {
654
        if (mem->is_MergeMem()) {
655
          if (m != mem->as_MergeMem()->memory_at(C->get_alias_index(u->adr_type()))) {
656
            return false;
657
          }
658
#ifdef ASSERT
659
          mm->set_memory_at(C->get_alias_index(u->adr_type()), mem->as_MergeMem()->base_memory());
660
#endif
661
        } else {
662
          if (m != mem) {
663
            return false;
664
          }
665
        }
666
      }
667
    }
668
  }
669
  return true;
670
}
671

672
SafePointNode* PhaseIdealLoop::find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop) {
673
  IfNode* exit_test = back_control->in(0)->as_If();
674
  SafePointNode* safepoint = nullptr;
675
  if (exit_test->in(0)->is_SafePoint() && exit_test->in(0)->outcnt() == 1) {
676
    safepoint = exit_test->in(0)->as_SafePoint();
677
  } else {
678
    Node* c = back_control;
679
    while (c != x && c->Opcode() != Op_SafePoint) {
680
      c = idom(c);
681
    }
682

683
    if (c->Opcode() == Op_SafePoint) {
684
      safepoint = c->as_SafePoint();
685
    }
686

687
    if (safepoint == nullptr) {
688
      return nullptr;
689
    }
690

691
    Node* mem = safepoint->in(TypeFunc::Memory);
692

693
    // We can only use that safepoint if there's no side effect between the backedge and the safepoint.
694

695
    // mm is used for book keeping
696
    MergeMemNode* mm = nullptr;
697
#ifdef ASSERT
698
    if (mem->is_MergeMem()) {
699
      mm = mem->clone()->as_MergeMem();
700
      _igvn._worklist.push(mm);
701
      for (MergeMemStream mms(mem->as_MergeMem()); mms.next_non_empty(); ) {
702
        if (mms.alias_idx() != Compile::AliasIdxBot && loop != get_loop(ctrl_or_self(mms.memory()))) {
703
          mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
704
        }
705
      }
706
    }
707
#endif
708
    if (!no_side_effect_since_safepoint(C, x, mem, mm, this)) {
709
      safepoint = nullptr;
710
    } else {
711
      assert(mm == nullptr|| _igvn.transform(mm) == mem->as_MergeMem()->base_memory(), "all memory state should have been processed");
712
    }
713
#ifdef ASSERT
714
    if (mm != nullptr) {
715
      _igvn.remove_dead_node(mm);
716
    }
717
#endif
718
  }
719
  return safepoint;
720
}
721

722
// If the loop has the shape of a counted loop but with a long
723
// induction variable, transform the loop in a loop nest: an inner
724
// loop that iterates for at most max int iterations with an integer
725
// induction variable and an outer loop that iterates over the full
726
// range of long values from the initial loop in (at most) max int
727
// steps. That is:
728
//
729
// x: for (long phi = init; phi < limit; phi += stride) {
730
//   // phi := Phi(L, init, incr)
731
//   // incr := AddL(phi, longcon(stride))
732
//   long incr = phi + stride;
733
//   ... use phi and incr ...
734
// }
735
//
736
// OR:
737
//
738
// x: for (long phi = init; (phi += stride) < limit; ) {
739
//   // phi := Phi(L, AddL(init, stride), incr)
740
//   // incr := AddL(phi, longcon(stride))
741
//   long incr = phi + stride;
742
//   ... use phi and (phi + stride) ...
743
// }
744
//
745
// ==transform=>
746
//
747
// const ulong inner_iters_limit = INT_MAX - stride - 1;  //near 0x7FFFFFF0
748
// assert(stride <= inner_iters_limit);  // else abort transform
749
// assert((extralong)limit + stride <= LONG_MAX);  // else deopt
750
// outer_head: for (long outer_phi = init;;) {
751
//   // outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_phi)))
752
//   ulong inner_iters_max = (ulong) MAX(0, ((extralong)limit + stride - outer_phi));
753
//   long inner_iters_actual = MIN(inner_iters_limit, inner_iters_max);
754
//   assert(inner_iters_actual == (int)inner_iters_actual);
755
//   int inner_phi, inner_incr;
756
//   x: for (inner_phi = 0;; inner_phi = inner_incr) {
757
//     // inner_phi := Phi(x, intcon(0), inner_incr)
758
//     // inner_incr := AddI(inner_phi, intcon(stride))
759
//     inner_incr = inner_phi + stride;
760
//     if (inner_incr < inner_iters_actual) {
761
//       ... use phi=>(outer_phi+inner_phi) ...
762
//       continue;
763
//     }
764
//     else break;
765
//   }
766
//   if ((outer_phi+inner_phi) < limit)  //OR (outer_phi+inner_incr) < limit
767
//     continue;
768
//   else break;
769
// }
770
//
771
// The same logic is used to transform an int counted loop that contains long range checks into a loop nest of 2 int
772
// loops with long range checks transformed to int range checks in the inner loop.
773
bool PhaseIdealLoop::create_loop_nest(IdealLoopTree* loop, Node_List &old_new) {
774
  Node* x = loop->_head;
775
  // Only for inner loops
776
  if (loop->_child != nullptr || !x->is_BaseCountedLoop() || x->as_Loop()->is_loop_nest_outer_loop()) {
777
    return false;
778
  }
779

780
  if (x->is_CountedLoop() && !x->as_CountedLoop()->is_main_loop() && !x->as_CountedLoop()->is_normal_loop()) {
781
    return false;
782
  }
783

784
  BaseCountedLoopNode* head = x->as_BaseCountedLoop();
785
  BasicType bt = x->as_BaseCountedLoop()->bt();
786

787
  check_counted_loop_shape(loop, x, bt);
788

789
#ifndef PRODUCT
790
  if (bt == T_LONG) {
791
    Atomic::inc(&_long_loop_candidates);
792
  }
793
#endif
794

795
  jlong stride_con_long = head->stride_con();
796
  assert(stride_con_long != 0, "missed some peephole opt");
797
  // We can't iterate for more than max int at a time.
798
  if (stride_con_long != (jint)stride_con_long || stride_con_long == min_jint) {
799
    assert(bt == T_LONG, "only for long loops");
800
    return false;
801
  }
802
  jint stride_con = checked_cast<jint>(stride_con_long);
803
  // The number of iterations for the integer count loop: guarantee no
804
  // overflow: max_jint - stride_con max. -1 so there's no need for a
805
  // loop limit check if the exit test is <= or >=.
806
  int iters_limit = max_jint - ABS(stride_con) - 1;
807
#ifdef ASSERT
808
  if (bt == T_LONG && StressLongCountedLoop > 0) {
809
    iters_limit = iters_limit / StressLongCountedLoop;
810
  }
811
#endif
812
  // At least 2 iterations so counted loop construction doesn't fail
813
  if (iters_limit/ABS(stride_con) < 2) {
814
    return false;
815
  }
816

817
  PhiNode* phi = head->phi()->as_Phi();
818
  Node* incr = head->incr();
819

820
  Node* back_control = head->in(LoopNode::LoopBackControl);
821

822
  // data nodes on back branch not supported
823
  if (back_control->outcnt() > 1) {
824
    return false;
825
  }
826

827
  Node* limit = head->limit();
828
  // We'll need to use the loop limit before the inner loop is entered
829
  if (!is_dominator(get_ctrl(limit), x)) {
830
    return false;
831
  }
832

833
  IfNode* exit_test = head->loopexit();
834

835
  assert(back_control->Opcode() == Op_IfTrue, "wrong projection for back edge");
836

837
  Node_List range_checks;
838
  iters_limit = extract_long_range_checks(loop, stride_con, iters_limit, phi, range_checks);
839

840
  if (bt == T_INT) {
841
    // The only purpose of creating a loop nest is to handle long range checks. If there are none, do not proceed further.
842
    if (range_checks.size() == 0) {
843
      return false;
844
    }
845
  }
846

847
  // Take what we know about the number of iterations of the long counted loop into account when computing the limit of
848
  // the inner loop.
849
  const Node* init = head->init_trip();
850
  const TypeInteger* lo = _igvn.type(init)->is_integer(bt);
851
  const TypeInteger* hi = _igvn.type(limit)->is_integer(bt);
852
  if (stride_con < 0) {
853
    swap(lo, hi);
854
  }
855
  if (hi->hi_as_long() <= lo->lo_as_long()) {
856
    // not a loop after all
857
    return false;
858
  }
859

860
  if (range_checks.size() > 0) {
861
    // This transformation requires peeling one iteration. Also, if it has range checks and they are eliminated by Loop
862
    // Predication, then 2 Hoisted Check Predicates are added for one range check. Finally, transforming a long range
863
    // check requires extra logic to be executed before the loop is entered and for the outer loop. As a result, the
864
    // transformations can't pay off for a small number of iterations: roughly, if the loop runs for 3 iterations, it's
865
    // going to execute as many range checks once transformed with range checks eliminated (1 peeled iteration with
866
    // range checks + 2 predicates per range checks) as it would have not transformed. It also has to pay for the extra
867
    // logic on loop entry and for the outer loop.
868
    loop->compute_trip_count(this);
869
    if (head->is_CountedLoop() && head->as_CountedLoop()->has_exact_trip_count()) {
870
      if (head->as_CountedLoop()->trip_count() <= 3) {
871
        return false;
872
      }
873
    } else {
874
      loop->compute_profile_trip_cnt(this);
875
      if (!head->is_profile_trip_failed() && head->profile_trip_cnt() <= 3) {
876
        return false;
877
      }
878
    }
879
  }
880

881
  julong orig_iters = (julong)hi->hi_as_long() - lo->lo_as_long();
882
  iters_limit = checked_cast<int>(MIN2((julong)iters_limit, orig_iters));
883

884
  // We need a safepoint to insert Parse Predicates for the inner loop.
885
  SafePointNode* safepoint;
886
  if (bt == T_INT && head->as_CountedLoop()->is_strip_mined()) {
887
    // Loop is strip mined: use the safepoint of the outer strip mined loop
888
    OuterStripMinedLoopNode* outer_loop = head->as_CountedLoop()->outer_loop();
889
    assert(outer_loop != nullptr, "no outer loop");
890
    safepoint = outer_loop->outer_safepoint();
891
    outer_loop->transform_to_counted_loop(&_igvn, this);
892
    exit_test = head->loopexit();
893
  } else {
894
    safepoint = find_safepoint(back_control, x, loop);
895
  }
896

897
  Node* exit_branch = exit_test->proj_out(false);
898
  Node* entry_control = head->in(LoopNode::EntryControl);
899

900
  // Clone the control flow of the loop to build an outer loop
901
  Node* outer_back_branch = back_control->clone();
902
  Node* outer_exit_test = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
903
  Node* inner_exit_branch = exit_branch->clone();
904

905
  LoopNode* outer_head = new LoopNode(entry_control, outer_back_branch);
906
  IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_head, outer_back_branch);
907

908
  const bool body_populated = true;
909
  register_control(outer_head, outer_ilt, entry_control, body_populated);
910

911
  _igvn.register_new_node_with_optimizer(inner_exit_branch);
912
  set_loop(inner_exit_branch, outer_ilt);
913
  set_idom(inner_exit_branch, exit_test, dom_depth(exit_branch));
914

915
  outer_exit_test->set_req(0, inner_exit_branch);
916
  register_control(outer_exit_test, outer_ilt, inner_exit_branch, body_populated);
917

918
  _igvn.replace_input_of(exit_branch, 0, outer_exit_test);
919
  set_idom(exit_branch, outer_exit_test, dom_depth(exit_branch));
920

921
  outer_back_branch->set_req(0, outer_exit_test);
922
  register_control(outer_back_branch, outer_ilt, outer_exit_test, body_populated);
923

924
  _igvn.replace_input_of(x, LoopNode::EntryControl, outer_head);
925
  set_idom(x, outer_head, dom_depth(x));
926

927
  // add an iv phi to the outer loop and use it to compute the inner
928
  // loop iteration limit
929
  Node* outer_phi = phi->clone();
930
  outer_phi->set_req(0, outer_head);
931
  register_new_node(outer_phi, outer_head);
932

933
  Node* inner_iters_max = nullptr;
934
  if (stride_con > 0) {
935
    inner_iters_max = MaxNode::max_diff_with_zero(limit, outer_phi, TypeInteger::bottom(bt), _igvn);
936
  } else {
937
    inner_iters_max = MaxNode::max_diff_with_zero(outer_phi, limit, TypeInteger::bottom(bt), _igvn);
938
  }
939

940
  Node* inner_iters_limit = _igvn.integercon(iters_limit, bt);
941
  // inner_iters_max may not fit in a signed integer (iterating from
942
  // Long.MIN_VALUE to Long.MAX_VALUE for instance). Use an unsigned
943
  // min.
944
  const TypeInteger* inner_iters_actual_range = TypeInteger::make(0, iters_limit, Type::WidenMin, bt);
945
  Node* inner_iters_actual = MaxNode::unsigned_min(inner_iters_max, inner_iters_limit, inner_iters_actual_range, _igvn);
946

947
  Node* inner_iters_actual_int;
948
  if (bt == T_LONG) {
949
    inner_iters_actual_int = new ConvL2INode(inner_iters_actual);
950
    _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
951
    // When the inner loop is transformed to a counted loop, a loop limit check is not expected to be needed because
952
    // the loop limit is less or equal to max_jint - stride - 1 (if stride is positive but a similar argument exists for
953
    // a negative stride). We add a CastII here to guarantee that, when the counted loop is created in a subsequent loop
954
    // opts pass, an accurate range of values for the limits is found.
955
    const TypeInt* inner_iters_actual_int_range = TypeInt::make(0, iters_limit, Type::WidenMin);
956
    inner_iters_actual_int = new CastIINode(outer_head, inner_iters_actual_int, inner_iters_actual_int_range, ConstraintCastNode::UnconditionalDependency);
957
    _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
958
  } else {
959
    inner_iters_actual_int = inner_iters_actual;
960
  }
961

962
  Node* int_zero = _igvn.intcon(0);
963
  set_ctrl(int_zero, C->root());
964
  if (stride_con < 0) {
965
    inner_iters_actual_int = new SubINode(int_zero, inner_iters_actual_int);
966
    _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
967
  }
968

969
  // Clone the iv data nodes as an integer iv
970
  Node* int_stride = _igvn.intcon(stride_con);
971
  set_ctrl(int_stride, C->root());
972
  Node* inner_phi = new PhiNode(x->in(0), TypeInt::INT);
973
  Node* inner_incr = new AddINode(inner_phi, int_stride);
974
  Node* inner_cmp = nullptr;
975
  inner_cmp = new CmpINode(inner_incr, inner_iters_actual_int);
976
  Node* inner_bol = new BoolNode(inner_cmp, exit_test->in(1)->as_Bool()->_test._test);
977
  inner_phi->set_req(LoopNode::EntryControl, int_zero);
978
  inner_phi->set_req(LoopNode::LoopBackControl, inner_incr);
979
  register_new_node(inner_phi, x);
980
  register_new_node(inner_incr, x);
981
  register_new_node(inner_cmp, x);
982
  register_new_node(inner_bol, x);
983

984
  _igvn.replace_input_of(exit_test, 1, inner_bol);
985

986
  // Clone inner loop phis to outer loop
987
  for (uint i = 0; i < head->outcnt(); i++) {
988
    Node* u = head->raw_out(i);
989
    if (u->is_Phi() && u != inner_phi && u != phi) {
990
      assert(u->in(0) == head, "inconsistent");
991
      Node* clone = u->clone();
992
      clone->set_req(0, outer_head);
993
      register_new_node(clone, outer_head);
994
      _igvn.replace_input_of(u, LoopNode::EntryControl, clone);
995
    }
996
  }
997

998
  // Replace inner loop long iv phi as inner loop int iv phi + outer
999
  // loop iv phi
1000
  Node* iv_add = loop_nest_replace_iv(phi, inner_phi, outer_phi, head, bt);
1001

1002
  set_subtree_ctrl(inner_iters_actual_int, body_populated);
1003

1004
  LoopNode* inner_head = create_inner_head(loop, head, exit_test);
1005

1006
  // Summary of steps from initial loop to loop nest:
1007
  //
1008
  // == old IR nodes =>
1009
  //
1010
  // entry_control: {...}
1011
  // x:
1012
  // for (long phi = init;;) {
1013
  //   // phi := Phi(x, init, incr)
1014
  //   // incr := AddL(phi, longcon(stride))
1015
  //   exit_test:
1016
  //   if (phi < limit)
1017
  //     back_control: fallthrough;
1018
  //   else
1019
  //     exit_branch: break;
1020
  //   long incr = phi + stride;
1021
  //   ... use phi and incr ...
1022
  //   phi = incr;
1023
  // }
1024
  //
1025
  // == new IR nodes (just before final peel) =>
1026
  //
1027
  // entry_control: {...}
1028
  // long adjusted_limit = limit + stride;  //because phi_incr != nullptr
1029
  // assert(!limit_check_required || (extralong)limit + stride == adjusted_limit);  // else deopt
1030
  // ulong inner_iters_limit = max_jint - ABS(stride) - 1;  //near 0x7FFFFFF0
1031
  // outer_head:
1032
  // for (long outer_phi = init;;) {
1033
  //   // outer_phi := phi->clone(), in(0):=outer_head, => Phi(outer_head, init, incr)
1034
  //   // REPLACE phi  => AddL(outer_phi, I2L(inner_phi))
1035
  //   // REPLACE incr => AddL(outer_phi, I2L(inner_incr))
1036
  //   // SO THAT outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_incr)))
1037
  //   ulong inner_iters_max = (ulong) MAX(0, ((extralong)adjusted_limit - outer_phi) * SGN(stride));
1038
  //   int inner_iters_actual_int = (int) MIN(inner_iters_limit, inner_iters_max) * SGN(stride);
1039
  //   inner_head: x: //in(1) := outer_head
1040
  //   int inner_phi;
1041
  //   for (inner_phi = 0;;) {
1042
  //     // inner_phi := Phi(x, intcon(0), inner_phi + stride)
1043
  //     int inner_incr = inner_phi + stride;
1044
  //     bool inner_bol = (inner_incr < inner_iters_actual_int);
1045
  //     exit_test: //exit_test->in(1) := inner_bol;
1046
  //     if (inner_bol) // WAS (phi < limit)
1047
  //       back_control: fallthrough;
1048
  //     else
1049
  //       inner_exit_branch: break;  //exit_branch->clone()
1050
  //     ... use phi=>(outer_phi+inner_phi) ...
1051
  //     inner_phi = inner_phi + stride;  // inner_incr
1052
  //   }
1053
  //   outer_exit_test:  //exit_test->clone(), in(0):=inner_exit_branch
1054
  //   if ((outer_phi+inner_phi) < limit)  // WAS (phi < limit)
1055
  //     outer_back_branch: fallthrough;  //back_control->clone(), in(0):=outer_exit_test
1056
  //   else
1057
  //     exit_branch: break;  //in(0) := outer_exit_test
1058
  // }
1059

1060
  if (bt == T_INT) {
1061
    outer_phi = new ConvI2LNode(outer_phi);
1062
    register_new_node(outer_phi, outer_head);
1063
  }
1064

1065
  transform_long_range_checks(stride_con, range_checks, outer_phi, inner_iters_actual_int,
1066
                              inner_phi, iv_add, inner_head);
1067
  // Peel one iteration of the loop and use the safepoint at the end
1068
  // of the peeled iteration to insert Parse Predicates. If no well
1069
  // positioned safepoint peel to guarantee a safepoint in the outer
1070
  // loop.
1071
  if (safepoint != nullptr || !loop->_has_call) {
1072
    old_new.clear();
1073
    do_peeling(loop, old_new);
1074
  } else {
1075
    C->set_major_progress();
1076
  }
1077

1078
  if (safepoint != nullptr) {
1079
    SafePointNode* cloned_sfpt = old_new[safepoint->_idx]->as_SafePoint();
1080

1081
    if (UseLoopPredicate) {
1082
      add_parse_predicate(Deoptimization::Reason_predicate, inner_head, outer_ilt, cloned_sfpt);
1083
    }
1084
    if (UseProfiledLoopPredicate) {
1085
      add_parse_predicate(Deoptimization::Reason_profile_predicate, inner_head, outer_ilt, cloned_sfpt);
1086
    }
1087
    add_parse_predicate(Deoptimization::Reason_loop_limit_check, inner_head, outer_ilt, cloned_sfpt);
1088
  }
1089

1090
#ifndef PRODUCT
1091
  if (bt == T_LONG) {
1092
    Atomic::inc(&_long_loop_nests);
1093
  }
1094
#endif
1095

1096
  inner_head->mark_loop_nest_inner_loop();
1097
  outer_head->mark_loop_nest_outer_loop();
1098

1099
  return true;
1100
}
1101

1102
int PhaseIdealLoop::extract_long_range_checks(const IdealLoopTree* loop, jint stride_con, int iters_limit, PhiNode* phi,
1103
                                              Node_List& range_checks) {
1104
  const jlong min_iters = 2;
1105
  jlong reduced_iters_limit = iters_limit;
1106
  jlong original_iters_limit = iters_limit;
1107
  for (uint i = 0; i < loop->_body.size(); i++) {
1108
    Node* c = loop->_body.at(i);
1109
    if (c->is_IfProj() && c->in(0)->is_RangeCheck()) {
1110
      IfProjNode* if_proj = c->as_IfProj();
1111
      CallStaticJavaNode* call = if_proj->is_uncommon_trap_if_pattern();
1112
      if (call != nullptr) {
1113
        Node* range = nullptr;
1114
        Node* offset = nullptr;
1115
        jlong scale = 0;
1116
        if (loop->is_range_check_if(if_proj, this, T_LONG, phi, range, offset, scale) &&
1117
            loop->is_invariant(range) && loop->is_invariant(offset) &&
1118
            scale != min_jlong &&
1119
            original_iters_limit / ABS(scale) >= min_iters * ABS(stride_con)) {
1120
          assert(scale == (jint)scale, "scale should be an int");
1121
          reduced_iters_limit = MIN2(reduced_iters_limit, original_iters_limit/ABS(scale));
1122
          range_checks.push(c);
1123
        }
1124
      }
1125
    }
1126
  }
1127

1128
  return checked_cast<int>(reduced_iters_limit);
1129
}
1130

1131
// One execution of the inner loop covers a sub-range of the entire iteration range of the loop: [A,Z), aka [A=init,
1132
// Z=limit). If the loop has at least one trip (which is the case here), the iteration variable i always takes A as its
1133
// first value, followed by A+S (S is the stride), next A+2S, etc. The limit is exclusive, so that the final value B of
1134
// i is never Z.  It will be B=Z-1 if S=1, or B=Z+1 if S=-1.
1135

1136
// If |S|>1 the formula for the last value B would require a floor operation, specifically B=floor((Z-sgn(S)-A)/S)*S+A,
1137
// which is B=Z-sgn(S)U for some U in [1,|S|].  So when S>0, i ranges as i:[A,Z) or i:[A,B=Z-U], or else (in reverse)
1138
// as i:(Z,A] or i:[B=Z+U,A].  It will become important to reason about this inclusive range [A,B] or [B,A].
1139

1140
// Within the loop there may be many range checks.  Each such range check (R.C.) is of the form 0 <= i*K+L < R, where K
1141
// is a scale factor applied to the loop iteration variable i, and L is some offset; K, L, and R are loop-invariant.
1142
// Because R is never negative (see below), this check can always be simplified to an unsigned check i*K+L <u R.
1143

1144
// When a long loop over a 64-bit variable i (outer_iv) is decomposed into a series of shorter sub-loops over a 32-bit
1145
// variable j (inner_iv), j ranges over a shorter interval j:[0,B_2] or [0,Z_2) (assuming S > 0), where the limit is
1146
// chosen to prevent various cases of 32-bit overflow (including multiplications j*K below).  In the sub-loop the
1147
// logical value i is offset from j by a 64-bit constant C, so i ranges in i:C+[0,Z_2).
1148

1149
// For S<0, j ranges (in reverse!) through j:[-|B_2|,0] or (-|Z_2|,0].  For either sign of S, we can say i=j+C and j
1150
// ranges through 32-bit ranges [A_2,B_2] or [B_2,A_2] (A_2=0 of course).
1151

1152
// The disjoint union of all the C+[A_2,B_2] ranges from the sub-loops must be identical to the whole range [A,B].
1153
// Assuming S>0, the first C must be A itself, and the next C value is the previous C+B_2, plus S.  If |S|=1, the next
1154
// C value is also the previous C+Z_2.  In each sub-loop, j counts from j=A_2=0 and i counts from C+0 and exits at
1155
// j=B_2 (i=C+B_2), just before it gets to i=C+Z_2.  Both i and j count up (from C and 0) if S>0; otherwise they count
1156
// down (from C and 0 again).
1157

1158
// Returning to range checks, we see that each i*K+L <u R expands to (C+j)*K+L <u R, or j*K+Q <u R, where Q=(C*K+L).
1159
// (Recall that K and L and R are loop-invariant scale, offset and range values for a particular R.C.)  This is still a
1160
// 64-bit comparison, so the range check elimination logic will not apply to it.  (The R.C.E. transforms operate only on
1161
// 32-bit indexes and comparisons, because they use 64-bit temporary values to avoid overflow; see
1162
// PhaseIdealLoop::add_constraint.)
1163

1164
// We must transform this comparison so that it gets the same answer, but by means of a 32-bit R.C. (using j not i) of
1165
// the form j*K+L_2 <u32 R_2.  Note that L_2 and R_2 must be loop-invariant, but only with respect to the sub-loop.  Thus, the
1166
// problem reduces to computing values for L_2 and R_2 (for each R.C. in the loop) in the loop header for the sub-loop.
1167
// Then the standard R.C.E. transforms can take those as inputs and further compute the necessary minimum and maximum
1168
// values for the 32-bit counter j within which the range checks can be eliminated.
1169

1170
// So, given j*K+Q <u R, we need to find some j*K+L_2 <u32 R_2, where L_2 and R_2 fit in 32 bits, and the 32-bit operations do
1171
// not overflow. We also need to cover the cases where i*K+L (= j*K+Q) overflows to a 64-bit negative, since that is
1172
// allowed as an input to the R.C., as long as the R.C. as a whole fails.
1173

1174
// If 32-bit multiplication j*K might overflow, we adjust the sub-loop limit Z_2 closer to zero to reduce j's range.
1175

1176
// For each R.C. j*K+Q <u32 R, the range of mathematical values of j*K+Q in the sub-loop is [Q_min, Q_max], where
1177
// Q_min=Q and Q_max=B_2*K+Q (if S>0 and K>0), Q_min=A_2*K+Q and Q_max=Q (if S<0 and K>0),
1178
// Q_min=B_2*K+Q and Q_max=Q if (S>0 and K<0), Q_min=Q and Q_max=A_2*K+Q (if S<0 and K<0)
1179

1180
// Note that the first R.C. value is always Q=(S*K>0 ? Q_min : Q_max).  Also Q_{min,max} = Q + {min,max}(A_2*K,B_2*K).
1181
// If S*K>0 then, as the loop iterations progress, each R.C. value i*K+L = j*K+Q goes up from Q=Q_min towards Q_max.
1182
// If S*K<0 then j*K+Q starts at Q=Q_max and goes down towards Q_min.
1183

1184
// Case A: Some Negatives (but no overflow).
1185
// Number line:
1186
// |s64_min   .    .    .    0    .    .    .   s64_max|
1187
// |    .  Q_min..Q_max .    0    .    .    .     .    |  s64 negative
1188
// |    .     .    .    .    R=0  R<   R<   R<    R<   |  (against R values)
1189
// |    .     .    .  Q_min..0..Q_max  .    .     .    |  small mixed
1190
// |    .     .    .    .    R    R    R<   R<    R<   |  (against R values)
1191
//
1192
// R values which are out of range (>Q_max+1) are reduced to max(0,Q_max+1).  They are marked on the number line as R<.
1193
//
1194
// So, if Q_min <s64 0, then use this test:
1195
// j*K + s32_trunc(Q_min) <u32 clamp(R, 0, Q_max+1) if S*K>0 (R.C.E. steps upward)
1196
// j*K + s32_trunc(Q_max) <u32 clamp(R, 0, Q_max+1) if S*K<0 (R.C.E. steps downward)
1197
// Both formulas reduce to adding j*K to the 32-bit truncated value of the first R.C. expression value, Q:
1198
// j*K + s32_trunc(Q) <u32 clamp(R, 0, Q_max+1) for all S,K
1199

1200
// If the 32-bit truncation loses information, no harm is done, since certainly the clamp also will return R_2=zero.
1201

1202
// Case B: No Negatives.
1203
// Number line:
1204
// |s64_min   .    .    .    0    .    .    .   s64_max|
1205
// |    .     .    .    .    0 Q_min..Q_max .     .    |  small positive
1206
// |    .     .    .    .    R>   R    R    R<    R<   |  (against R values)
1207
// |    .     .    .    .    0    . Q_min..Q_max  .    |  s64 positive
1208
// |    .     .    .    .    R>   R>   R    R     R<   |  (against R values)
1209
//
1210
// R values which are out of range (<Q_min or >Q_max+1) are reduced as marked: R> up to Q_min, R< down to Q_max+1.
1211
// Then the whole comparison is shifted left by Q_min, so it can take place at zero, which is a nice 32-bit value.
1212
//
1213
// So, if both Q_min, Q_max+1 >=s64 0, then use this test:
1214
// j*K + 0         <u32 clamp(R, Q_min, Q_max+1) - Q_min if S*K>0
1215
// More generally:
1216
// j*K + Q - Q_min <u32 clamp(R, Q_min, Q_max+1) - Q_min for all S,K
1217

1218
// Case C: Overflow in the 64-bit domain
1219
// Number line:
1220
// |..Q_max-2^64   .    .    0    .    .    .   Q_min..|  s64 overflow
1221
// |    .     .    .    .    R>   R>   R>   R>    R    |  (against R values)
1222
//
1223
// In this case, Q_min >s64 Q_max+1, even though the mathematical values of Q_min and Q_max+1 are correctly ordered.
1224
// The formulas from the previous case can be used, except that the bad upper bound Q_max is replaced by max_jlong.
1225
// (In fact, we could use any replacement bound from R to max_jlong inclusive, as the input to the clamp function.)
1226
//
1227
// So if Q_min >=s64 0 but Q_max+1 <s64 0, use this test:
1228
// j*K + 0         <u32 clamp(R, Q_min, max_jlong) - Q_min if S*K>0
1229
// More generally:
1230
// j*K + Q - Q_min <u32 clamp(R, Q_min, max_jlong) - Q_min for all S,K
1231
//
1232
// Dropping the bad bound means only Q_min is used to reduce the range of R:
1233
// j*K + Q - Q_min <u32 max(Q_min, R) - Q_min for all S,K
1234
//
1235
// Here the clamp function is a 64-bit min/max that reduces the dynamic range of its R operand to the required [L,H]:
1236
//     clamp(X, L, H) := max(L, min(X, H))
1237
// When degenerately L > H, it returns L not H.
1238
//
1239
// All of the formulas above can be merged into a single one:
1240
//     L_clamp = Q_min < 0 ? 0 : Q_min        --whether and how far to left-shift
1241
//     H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
1242
//             = Q_max+1 < 0 && Q_min >= 0 ? max_jlong : Q_max+1
1243
//     Q_first = Q = (S*K>0 ? Q_min : Q_max) = (C*K+L)
1244
//     R_clamp = clamp(R, L_clamp, H_clamp)   --reduced dynamic range
1245
//     replacement R.C.:
1246
//       j*K + Q_first - L_clamp <u32 R_clamp - L_clamp
1247
//     or equivalently:
1248
//       j*K + L_2 <u32 R_2
1249
//     where
1250
//       L_2 = Q_first - L_clamp
1251
//       R_2 = R_clamp - L_clamp
1252
//
1253
// Note on why R is never negative:
1254
//
1255
// Various details of this transformation would break badly if R could be negative, so this transformation only
1256
// operates after obtaining hard evidence that R<0 is impossible.  For example, if R comes from a LoadRange node, we
1257
// know R cannot be negative.  For explicit checks (of both int and long) a proof is constructed in
1258
// inline_preconditions_checkIndex, which triggers an uncommon trap if R<0, then wraps R in a ConstraintCastNode with a
1259
// non-negative type.  Later on, when IdealLoopTree::is_range_check_if looks for an optimizable R.C., it checks that
1260
// the type of that R node is non-negative.  Any "wild" R node that could be negative is not treated as an optimizable
1261
// R.C., but R values from a.length and inside checkIndex are good to go.
1262
//
1263
void PhaseIdealLoop::transform_long_range_checks(int stride_con, const Node_List &range_checks, Node* outer_phi,
1264
                                                 Node* inner_iters_actual_int, Node* inner_phi,
1265
                                                 Node* iv_add, LoopNode* inner_head) {
1266
  Node* long_zero = _igvn.longcon(0);
1267
  set_ctrl(long_zero, C->root());
1268
  Node* int_zero = _igvn.intcon(0);
1269
  set_ctrl(int_zero, this->C->root());
1270
  Node* long_one = _igvn.longcon(1);
1271
  set_ctrl(long_one, this->C->root());
1272
  Node* int_stride = _igvn.intcon(checked_cast<int>(stride_con));
1273
  set_ctrl(int_stride, this->C->root());
1274

1275
  for (uint i = 0; i < range_checks.size(); i++) {
1276
    ProjNode* proj = range_checks.at(i)->as_Proj();
1277
    ProjNode* unc_proj = proj->other_if_proj();
1278
    RangeCheckNode* rc = proj->in(0)->as_RangeCheck();
1279
    jlong scale = 0;
1280
    Node* offset = nullptr;
1281
    Node* rc_bol = rc->in(1);
1282
    Node* rc_cmp = rc_bol->in(1);
1283
    if (rc_cmp->Opcode() == Op_CmpU) {
1284
      // could be shared and have already been taken care of
1285
      continue;
1286
    }
1287
    bool short_scale = false;
1288
    bool ok = is_scaled_iv_plus_offset(rc_cmp->in(1), iv_add, T_LONG, &scale, &offset, &short_scale);
1289
    assert(ok, "inconsistent: was tested before");
1290
    Node* range = rc_cmp->in(2);
1291
    Node* c = rc->in(0);
1292
    Node* entry_control = inner_head->in(LoopNode::EntryControl);
1293

1294
    Node* R = range;
1295
    Node* K = _igvn.longcon(scale);
1296
    set_ctrl(K, this->C->root());
1297

1298
    Node* L = offset;
1299

1300
    if (short_scale) {
1301
      // This converts:
1302
      // (int)i*K + L <u64 R
1303
      // with K an int into:
1304
      // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
1305
      // to protect against an overflow of (int)i*K
1306
      //
1307
      // Because if (int)i*K overflows, there are K,L where:
1308
      // (int)i*K + L <u64 R is false because (int)i*K+L overflows to a negative which becomes a huge u64 value.
1309
      // But if i*(long)K + L is >u64 (long)max_jint and still is <u64 R, then
1310
      // i*(long)K + L <u64 R is true.
1311
      //
1312
      // As a consequence simply converting i*K + L <u64 R to i*(long)K + L <u64 R could cause incorrect execution.
1313
      //
1314
      // It's always true that:
1315
      // (int)i*K <u64 (long)max_jint + 1
1316
      // which implies (int)i*K + L <u64 (long)max_jint + 1 + L
1317
      // As a consequence:
1318
      // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
1319
      // is always false in case of overflow of i*K
1320
      //
1321
      // Note, there are also K,L where i*K overflows and
1322
      // i*K + L <u64 R is true, but
1323
      // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R) is false
1324
      // So this transformation could cause spurious deoptimizations and failed range check elimination
1325
      // (but not incorrect execution) for unlikely corner cases with overflow.
1326
      // If this causes problems in practice, we could maybe direct execution to a post-loop, instead of deoptimizing.
1327
      Node* max_jint_plus_one_long = _igvn.longcon((jlong)max_jint + 1);
1328
      set_ctrl(max_jint_plus_one_long, C->root());
1329
      Node* max_range = new AddLNode(max_jint_plus_one_long, L);
1330
      register_new_node(max_range, entry_control);
1331
      R = MaxNode::unsigned_min(R, max_range, TypeLong::POS, _igvn);
1332
      set_subtree_ctrl(R, true);
1333
    }
1334

1335
    Node* C = outer_phi;
1336

1337
    // Start with 64-bit values:
1338
    //   i*K + L <u64 R
1339
    //   (C+j)*K + L <u64 R
1340
    //   j*K + Q <u64 R    where Q = Q_first = C*K+L
1341
    Node* Q_first = new MulLNode(C, K);
1342
    register_new_node(Q_first, entry_control);
1343
    Q_first = new AddLNode(Q_first, L);
1344
    register_new_node(Q_first, entry_control);
1345

1346
    // Compute endpoints of the range of values j*K + Q.
1347
    //  Q_min = (j=0)*K + Q;  Q_max = (j=B_2)*K + Q
1348
    Node* Q_min = Q_first;
1349

1350
    // Compute the exact ending value B_2 (which is really A_2 if S < 0)
1351
    Node* B_2 = new LoopLimitNode(this->C, int_zero, inner_iters_actual_int, int_stride);
1352
    register_new_node(B_2, entry_control);
1353
    B_2 = new SubINode(B_2, int_stride);
1354
    register_new_node(B_2, entry_control);
1355
    B_2 = new ConvI2LNode(B_2);
1356
    register_new_node(B_2, entry_control);
1357

1358
    Node* Q_max = new MulLNode(B_2, K);
1359
    register_new_node(Q_max, entry_control);
1360
    Q_max = new AddLNode(Q_max, Q_first);
1361
    register_new_node(Q_max, entry_control);
1362

1363
    if (scale * stride_con < 0) {
1364
      swap(Q_min, Q_max);
1365
    }
1366
    // Now, mathematically, Q_max > Q_min, and they are close enough so that (Q_max-Q_min) fits in 32 bits.
1367

1368
    // L_clamp = Q_min < 0 ? 0 : Q_min
1369
    Node* Q_min_cmp = new CmpLNode(Q_min, long_zero);
1370
    register_new_node(Q_min_cmp, entry_control);
1371
    Node* Q_min_bool = new BoolNode(Q_min_cmp, BoolTest::lt);
1372
    register_new_node(Q_min_bool, entry_control);
1373
    Node* L_clamp = new CMoveLNode(Q_min_bool, Q_min, long_zero, TypeLong::LONG);
1374
    register_new_node(L_clamp, entry_control);
1375
    // (This could also be coded bitwise as L_clamp = Q_min & ~(Q_min>>63).)
1376

1377
    Node* Q_max_plus_one = new AddLNode(Q_max, long_one);
1378
    register_new_node(Q_max_plus_one, entry_control);
1379

1380
    // H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
1381
    // (Because Q_min and Q_max are close, the overflow check could also be encoded as Q_max+1 < 0 & Q_min >= 0.)
1382
    Node* max_jlong_long = _igvn.longcon(max_jlong);
1383
    set_ctrl(max_jlong_long, this->C->root());
1384
    Node* Q_max_cmp = new CmpLNode(Q_max_plus_one, Q_min);
1385
    register_new_node(Q_max_cmp, entry_control);
1386
    Node* Q_max_bool = new BoolNode(Q_max_cmp, BoolTest::lt);
1387
    register_new_node(Q_max_bool, entry_control);
1388
    Node* H_clamp = new CMoveLNode(Q_max_bool, Q_max_plus_one, max_jlong_long, TypeLong::LONG);
1389
    register_new_node(H_clamp, entry_control);
1390
    // (This could also be coded bitwise as H_clamp = ((Q_max+1)<<1 | M)>>>1 where M = (Q_max+1)>>63 & ~Q_min>>63.)
1391

1392
    // R_2 = clamp(R, L_clamp, H_clamp) - L_clamp
1393
    // that is:  R_2 = clamp(R, L_clamp=0, H_clamp=Q_max)      if Q_min < 0
1394
    // or else:  R_2 = clamp(R, L_clamp,   H_clamp) - Q_min    if Q_min >= 0
1395
    // and also: R_2 = clamp(R, L_clamp,   Q_max+1) - L_clamp  if Q_min < Q_max+1 (no overflow)
1396
    // or else:  R_2 = clamp(R, L_clamp, *no limit*)- L_clamp  if Q_max+1 < Q_min (overflow)
1397
    Node* R_2 = clamp(R, L_clamp, H_clamp);
1398
    R_2 = new SubLNode(R_2, L_clamp);
1399
    register_new_node(R_2, entry_control);
1400
    R_2 = new ConvL2INode(R_2, TypeInt::POS);
1401
    register_new_node(R_2, entry_control);
1402

1403
    // L_2 = Q_first - L_clamp
1404
    // We are subtracting L_clamp from both sides of the <u32 comparison.
1405
    // If S*K>0, then Q_first == 0 and the R.C. expression at -L_clamp and steps upward to Q_max-L_clamp.
1406
    // If S*K<0, then Q_first != 0 and the R.C. expression starts high and steps downward to Q_min-L_clamp.
1407
    Node* L_2 = new SubLNode(Q_first, L_clamp);
1408
    register_new_node(L_2, entry_control);
1409
    L_2 = new ConvL2INode(L_2, TypeInt::INT);
1410
    register_new_node(L_2, entry_control);
1411

1412
    // Transform the range check using the computed values L_2/R_2
1413
    // from:   i*K + L   <u64 R
1414
    // to:     j*K + L_2 <u32 R_2
1415
    // that is:
1416
    //   (j*K + Q_first) - L_clamp <u32 clamp(R, L_clamp, H_clamp) - L_clamp
1417
    K = _igvn.intcon(checked_cast<int>(scale));
1418
    set_ctrl(K, this->C->root());
1419
    Node* scaled_iv = new MulINode(inner_phi, K);
1420
    register_new_node(scaled_iv, c);
1421
    Node* scaled_iv_plus_offset = new AddINode(scaled_iv, L_2);
1422
    register_new_node(scaled_iv_plus_offset, c);
1423

1424
    Node* new_rc_cmp = new CmpUNode(scaled_iv_plus_offset, R_2);
1425
    register_new_node(new_rc_cmp, c);
1426

1427
    _igvn.replace_input_of(rc_bol, 1, new_rc_cmp);
1428
  }
1429
}
1430

1431
Node* PhaseIdealLoop::clamp(Node* R, Node* L, Node* H) {
1432
  Node* min = MaxNode::signed_min(R, H, TypeLong::LONG, _igvn);
1433
  set_subtree_ctrl(min, true);
1434
  Node* max = MaxNode::signed_max(L, min, TypeLong::LONG, _igvn);
1435
  set_subtree_ctrl(max, true);
1436
  return max;
1437
}
1438

1439
LoopNode* PhaseIdealLoop::create_inner_head(IdealLoopTree* loop, BaseCountedLoopNode* head,
1440
                                            IfNode* exit_test) {
1441
  LoopNode* new_inner_head = new LoopNode(head->in(1), head->in(2));
1442
  IfNode* new_inner_exit = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
1443
  _igvn.register_new_node_with_optimizer(new_inner_head);
1444
  _igvn.register_new_node_with_optimizer(new_inner_exit);
1445
  loop->_body.push(new_inner_head);
1446
  loop->_body.push(new_inner_exit);
1447
  loop->_body.yank(head);
1448
  loop->_body.yank(exit_test);
1449
  set_loop(new_inner_head, loop);
1450
  set_loop(new_inner_exit, loop);
1451
  set_idom(new_inner_head, idom(head), dom_depth(head));
1452
  set_idom(new_inner_exit, idom(exit_test), dom_depth(exit_test));
1453
  lazy_replace(head, new_inner_head);
1454
  lazy_replace(exit_test, new_inner_exit);
1455
  loop->_head = new_inner_head;
1456
  return new_inner_head;
1457
}
1458

1459
#ifdef ASSERT
1460
void PhaseIdealLoop::check_counted_loop_shape(IdealLoopTree* loop, Node* x, BasicType bt) {
1461
  Node* back_control = loop_exit_control(x, loop);
1462
  assert(back_control != nullptr, "no back control");
1463

1464
  BoolTest::mask mask = BoolTest::illegal;
1465
  float cl_prob = 0;
1466
  Node* incr = nullptr;
1467
  Node* limit = nullptr;
1468

1469
  Node* cmp = loop_exit_test(back_control, loop, incr, limit, mask, cl_prob);
1470
  assert(cmp != nullptr && cmp->Opcode() == Op_Cmp(bt), "no exit test");
1471

1472
  Node* phi_incr = nullptr;
1473
  incr = loop_iv_incr(incr, x, loop, phi_incr);
1474
  assert(incr != nullptr && incr->Opcode() == Op_Add(bt), "no incr");
1475

1476
  Node* xphi = nullptr;
1477
  Node* stride = loop_iv_stride(incr, loop, xphi);
1478

1479
  assert(stride != nullptr, "no stride");
1480

1481
  PhiNode* phi = loop_iv_phi(xphi, phi_incr, x, loop);
1482

1483
  assert(phi != nullptr && phi->in(LoopNode::LoopBackControl) == incr, "No phi");
1484

1485
  jlong stride_con = stride->get_integer_as_long(bt);
1486

1487
  assert(condition_stride_ok(mask, stride_con), "illegal condition");
1488

1489
  assert(mask != BoolTest::ne, "unexpected condition");
1490
  assert(phi_incr == nullptr, "bad loop shape");
1491
  assert(cmp->in(1) == incr, "bad exit test shape");
1492

1493
  // Safepoint on backedge not supported
1494
  assert(x->in(LoopNode::LoopBackControl)->Opcode() != Op_SafePoint, "no safepoint on backedge");
1495
}
1496
#endif
1497

1498
#ifdef ASSERT
1499
// convert an int counted loop to a long counted to stress handling of
1500
// long counted loops
1501
bool PhaseIdealLoop::convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop) {
1502
  Unique_Node_List iv_nodes;
1503
  Node_List old_new;
1504
  iv_nodes.push(cmp);
1505
  bool failed = false;
1506

1507
  for (uint i = 0; i < iv_nodes.size() && !failed; i++) {
1508
    Node* n = iv_nodes.at(i);
1509
    switch(n->Opcode()) {
1510
      case Op_Phi: {
1511
        Node* clone = new PhiNode(n->in(0), TypeLong::LONG);
1512
        old_new.map(n->_idx, clone);
1513
        break;
1514
      }
1515
      case Op_CmpI: {
1516
        Node* clone = new CmpLNode(nullptr, nullptr);
1517
        old_new.map(n->_idx, clone);
1518
        break;
1519
      }
1520
      case Op_AddI: {
1521
        Node* clone = new AddLNode(nullptr, nullptr);
1522
        old_new.map(n->_idx, clone);
1523
        break;
1524
      }
1525
      case Op_CastII: {
1526
        failed = true;
1527
        break;
1528
      }
1529
      default:
1530
        DEBUG_ONLY(n->dump());
1531
        fatal("unexpected");
1532
    }
1533

1534
    for (uint i = 1; i < n->req(); i++) {
1535
      Node* in = n->in(i);
1536
      if (in == nullptr) {
1537
        continue;
1538
      }
1539
      if (loop->is_member(get_loop(get_ctrl(in)))) {
1540
        iv_nodes.push(in);
1541
      }
1542
    }
1543
  }
1544

1545
  if (failed) {
1546
    for (uint i = 0; i < iv_nodes.size(); i++) {
1547
      Node* n = iv_nodes.at(i);
1548
      Node* clone = old_new[n->_idx];
1549
      if (clone != nullptr) {
1550
        _igvn.remove_dead_node(clone);
1551
      }
1552
    }
1553
    return false;
1554
  }
1555

1556
  for (uint i = 0; i < iv_nodes.size(); i++) {
1557
    Node* n = iv_nodes.at(i);
1558
    Node* clone = old_new[n->_idx];
1559
    for (uint i = 1; i < n->req(); i++) {
1560
      Node* in = n->in(i);
1561
      if (in == nullptr) {
1562
        continue;
1563
      }
1564
      Node* in_clone = old_new[in->_idx];
1565
      if (in_clone == nullptr) {
1566
        assert(_igvn.type(in)->isa_int(), "");
1567
        in_clone = new ConvI2LNode(in);
1568
        _igvn.register_new_node_with_optimizer(in_clone);
1569
        set_subtree_ctrl(in_clone, false);
1570
      }
1571
      if (in_clone->in(0) == nullptr) {
1572
        in_clone->set_req(0, C->top());
1573
        clone->set_req(i, in_clone);
1574
        in_clone->set_req(0, nullptr);
1575
      } else {
1576
        clone->set_req(i, in_clone);
1577
      }
1578
    }
1579
    _igvn.register_new_node_with_optimizer(clone);
1580
  }
1581
  set_ctrl(old_new[phi->_idx], phi->in(0));
1582

1583
  for (uint i = 0; i < iv_nodes.size(); i++) {
1584
    Node* n = iv_nodes.at(i);
1585
    Node* clone = old_new[n->_idx];
1586
    set_subtree_ctrl(clone, false);
1587
    Node* m = n->Opcode() == Op_CmpI ? clone : nullptr;
1588
    for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1589
      Node* u = n->fast_out(i);
1590
      if (iv_nodes.member(u)) {
1591
        continue;
1592
      }
1593
      if (m == nullptr) {
1594
        m = new ConvL2INode(clone);
1595
        _igvn.register_new_node_with_optimizer(m);
1596
        set_subtree_ctrl(m, false);
1597
      }
1598
      _igvn.rehash_node_delayed(u);
1599
      int nb = u->replace_edge(n, m, &_igvn);
1600
      --i, imax -= nb;
1601
    }
1602
  }
1603
  return true;
1604
}
1605
#endif
1606

1607
//------------------------------is_counted_loop--------------------------------
1608
bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt) {
1609
  PhaseGVN *gvn = &_igvn;
1610

1611
  Node* back_control = loop_exit_control(x, loop);
1612
  if (back_control == nullptr) {
1613
    return false;
1614
  }
1615

1616
  BoolTest::mask bt = BoolTest::illegal;
1617
  float cl_prob = 0;
1618
  Node* incr = nullptr;
1619
  Node* limit = nullptr;
1620
  Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
1621
  if (cmp == nullptr || cmp->Opcode() != Op_Cmp(iv_bt)) {
1622
    return false; // Avoid pointer & float & 64-bit compares
1623
  }
1624

1625
  // Trip-counter increment must be commutative & associative.
1626
  if (incr->Opcode() == Op_Cast(iv_bt)) {
1627
    incr = incr->in(1);
1628
  }
1629

1630
  Node* phi_incr = nullptr;
1631
  incr = loop_iv_incr(incr, x, loop, phi_incr);
1632
  if (incr == nullptr) {
1633
    return false;
1634
  }
1635

1636
  Node* trunc1 = nullptr;
1637
  Node* trunc2 = nullptr;
1638
  const TypeInteger* iv_trunc_t = nullptr;
1639
  Node* orig_incr = incr;
1640
  if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t, iv_bt))) {
1641
    return false; // Funny increment opcode
1642
  }
1643
  assert(incr->Opcode() == Op_Add(iv_bt), "wrong increment code");
1644

1645
  Node* xphi = nullptr;
1646
  Node* stride = loop_iv_stride(incr, loop, xphi);
1647

1648
  if (stride == nullptr) {
1649
    return false;
1650
  }
1651

1652
  if (xphi->Opcode() == Op_Cast(iv_bt)) {
1653
    xphi = xphi->in(1);
1654
  }
1655

1656
  // Stride must be constant
1657
  jlong stride_con = stride->get_integer_as_long(iv_bt);
1658
  assert(stride_con != 0, "missed some peephole opt");
1659

1660
  PhiNode* phi = loop_iv_phi(xphi, phi_incr, x, loop);
1661

1662
  if (phi == nullptr ||
1663
      (trunc1 == nullptr && phi->in(LoopNode::LoopBackControl) != incr) ||
1664
      (trunc1 != nullptr && phi->in(LoopNode::LoopBackControl) != trunc1)) {
1665
    return false;
1666
  }
1667

1668
  Node* iftrue = back_control;
1669
  uint iftrue_op = iftrue->Opcode();
1670
  Node* iff = iftrue->in(0);
1671
  BoolNode* test = iff->in(1)->as_Bool();
1672

1673
  const TypeInteger* limit_t = gvn->type(limit)->is_integer(iv_bt);
1674
  if (trunc1 != nullptr) {
1675
    // When there is a truncation, we must be sure that after the truncation
1676
    // the trip counter will end up higher than the limit, otherwise we are looking
1677
    // at an endless loop. Can happen with range checks.
1678

1679
    // Example:
1680
    // int i = 0;
1681
    // while (true)
1682
    //    sum + = array[i];
1683
    //    i++;
1684
    //    i = i && 0x7fff;
1685
    //  }
1686
    //
1687
    // If the array is shorter than 0x8000 this exits through a AIOOB
1688
    //  - Counted loop transformation is ok
1689
    // If the array is longer then this is an endless loop
1690
    //  - No transformation can be done.
1691

1692
    const TypeInteger* incr_t = gvn->type(orig_incr)->is_integer(iv_bt);
1693
    if (limit_t->hi_as_long() > incr_t->hi_as_long()) {
1694
      // if the limit can have a higher value than the increment (before the phi)
1695
      return false;
1696
    }
1697
  }
1698

1699
  Node *init_trip = phi->in(LoopNode::EntryControl);
1700

1701
  // If iv trunc type is smaller than int, check for possible wrap.
1702
  if (!TypeInteger::bottom(iv_bt)->higher_equal(iv_trunc_t)) {
1703
    assert(trunc1 != nullptr, "must have found some truncation");
1704

1705
    // Get a better type for the phi (filtered thru if's)
1706
    const TypeInteger* phi_ft = filtered_type(phi);
1707

1708
    // Can iv take on a value that will wrap?
1709
    //
1710
    // Ensure iv's limit is not within "stride" of the wrap value.
1711
    //
1712
    // Example for "short" type
1713
    //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
1714
    //    If the stride is +10, then the last value of the induction
1715
    //    variable before the increment (phi_ft->_hi) must be
1716
    //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
1717
    //    ensure no truncation occurs after the increment.
1718

1719
    if (stride_con > 0) {
1720
      if (iv_trunc_t->hi_as_long() - phi_ft->hi_as_long() < stride_con ||
1721
          iv_trunc_t->lo_as_long() > phi_ft->lo_as_long()) {
1722
        return false;  // truncation may occur
1723
      }
1724
    } else if (stride_con < 0) {
1725
      if (iv_trunc_t->lo_as_long() - phi_ft->lo_as_long() > stride_con ||
1726
          iv_trunc_t->hi_as_long() < phi_ft->hi_as_long()) {
1727
        return false;  // truncation may occur
1728
      }
1729
    }
1730
    // No possibility of wrap so truncation can be discarded
1731
    // Promote iv type to Int
1732
  } else {
1733
    assert(trunc1 == nullptr && trunc2 == nullptr, "no truncation for int");
1734
  }
1735

1736
  if (!condition_stride_ok(bt, stride_con)) {
1737
    return false;
1738
  }
1739

1740
  const TypeInteger* init_t = gvn->type(init_trip)->is_integer(iv_bt);
1741

1742
  if (stride_con > 0) {
1743
    if (init_t->lo_as_long() > max_signed_integer(iv_bt) - stride_con) {
1744
      return false; // cyclic loop
1745
    }
1746
  } else {
1747
    if (init_t->hi_as_long() < min_signed_integer(iv_bt) - stride_con) {
1748
      return false; // cyclic loop
1749
    }
1750
  }
1751

1752
  if (phi_incr != nullptr && bt != BoolTest::ne) {
1753
    // check if there is a possibility of IV overflowing after the first increment
1754
    if (stride_con > 0) {
1755
      if (init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) {
1756
        return false;
1757
      }
1758
    } else {
1759
      if (init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con) {
1760
        return false;
1761
      }
1762
    }
1763
  }
1764

1765
  // =================================================
1766
  // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
1767
  //
1768

1769
  if (x->Opcode() == Op_Region) {
1770
    // x has not yet been transformed to Loop or LongCountedLoop.
1771
    // This should only happen if we are inside an infinite loop.
1772
    // It happens like this:
1773
    //   build_loop_tree -> do not attach infinite loop and nested loops
1774
    //   beautify_loops  -> does not transform the infinite and nested loops to LoopNode, because not attached yet
1775
    //   build_loop_tree -> find and attach infinite and nested loops
1776
    //   counted_loop    -> nested Regions are not yet transformed to LoopNodes, we land here
1777
    assert(x->as_Region()->is_in_infinite_subgraph(),
1778
           "x can only be a Region and not Loop if inside infinite loop");
1779
    // Come back later when Region is transformed to LoopNode
1780
    return false;
1781
  }
1782

1783
  assert(x->Opcode() == Op_Loop || x->Opcode() == Op_LongCountedLoop, "regular loops only");
1784
  C->print_method(PHASE_BEFORE_CLOOPS, 3, x);
1785

1786
  // ===================================================
1787
  // We can only convert this loop to a counted loop if we can guarantee that the iv phi will never overflow at runtime.
1788
  // This is an implicit assumption taken by some loop optimizations. We therefore must ensure this property at all cost.
1789
  // At this point, we've already excluded some trivial cases where an overflow could have been proven statically.
1790
  // But even though we cannot prove that an overflow will *not* happen, we still want to speculatively convert this loop
1791
  // to a counted loop. This can be achieved by adding additional iv phi overflow checks before the loop. If they fail,
1792
  // we trap and resume execution before the loop without having executed any iteration of the loop, yet.
1793
  //
1794
  // These additional iv phi overflow checks can be inserted as Loop Limit Check Predicates above the Loop Limit Check
1795
  // Parse Predicate which captures a JVM state just before the entry of the loop. If there is no such Parse Predicate,
1796
  // we cannot generate a Loop Limit Check Predicate and thus cannot speculatively convert the loop to a counted loop.
1797
  //
1798
  // In the following, we only focus on int loops with stride > 0 to keep things simple. The argumentation and proof
1799
  // for stride < 0 is analogously. For long loops, we would replace max_int with max_long.
1800
  //
1801
  //
1802
  // The loop to be converted does not always need to have the often used shape:
1803
  //
1804
  //                                                 i = init
1805
  //     i = init                                loop:
1806
  //     do {                                        ...
1807
  //         // ...               equivalent         i+=stride
1808
  //         i+=stride               <==>            if (i < limit)
1809
  //     } while (i < limit);                          goto loop
1810
  //                                             exit:
1811
  //                                                 ...
1812
  //
1813
  // where the loop exit check uses the post-incremented iv phi and a '<'-operator.
1814
  //
1815
  // We could also have '<='-operator (or '>='-operator for negative strides) or use the pre-incremented iv phi value
1816
  // in the loop exit check:
1817
  //
1818
  //         i = init
1819
  //     loop:
1820
  //         ...
1821
  //         if (i <= limit)
1822
  //             i+=stride
1823
  //             goto loop
1824
  //     exit:
1825
  //         ...
1826
  //
1827
  // Let's define the following terms:
1828
  // - iv_pre_i: The pre-incremented iv phi before the i-th iteration.
1829
  // - iv_post_i: The post-incremented iv phi after the i-th iteration.
1830
  //
1831
  // The iv_pre_i and iv_post_i have the following relation:
1832
  //      iv_pre_i + stride = iv_post_i
1833
  //
1834
  // When converting a loop to a counted loop, we want to have a canonicalized loop exit check of the form:
1835
  //     iv_post_i < adjusted_limit
1836
  //
1837
  // If that is not the case, we need to canonicalize the loop exit check by using different values for adjusted_limit:
1838
  // (LE1) iv_post_i < limit: Already canonicalized. We can directly use limit as adjusted_limit.
1839
  //           -> adjusted_limit = limit.
1840
  // (LE2) iv_post_i <= limit:
1841
  //           iv_post_i < limit + 1
1842
  //           -> adjusted limit = limit + 1
1843
  // (LE3) iv_pre_i < limit:
1844
  //           iv_pre_i + stride < limit + stride
1845
  //           iv_post_i < limit + stride
1846
  //           -> adjusted_limit = limit + stride
1847
  // (LE4) iv_pre_i <= limit:
1848
  //           iv_pre_i < limit + 1
1849
  //           iv_pre_i + stride < limit + stride + 1
1850
  //           iv_post_i < limit + stride + 1
1851
  //           -> adjusted_limit = limit + stride + 1
1852
  //
1853
  // Note that:
1854
  //     (AL) limit <= adjusted_limit.
1855
  //
1856
  // The following loop invariant has to hold for counted loops with n iterations (i.e. loop exit check true after n-th
1857
  // loop iteration) and a canonicalized loop exit check to guarantee that no iv_post_i over- or underflows:
1858
  // (INV) For i = 1..n, min_int <= iv_post_i <= max_int
1859
  //
1860
  // To prove (INV), we require the following two conditions/assumptions:
1861
  // (i): adjusted_limit - 1 + stride <= max_int
1862
  // (ii): init < limit
1863
  //
1864
  // If we can prove (INV), we know that there can be no over- or underflow of any iv phi value. We prove (INV) by
1865
  // induction by assuming (i) and (ii).
1866
  //
1867
  // Proof by Induction
1868
  // ------------------
1869
  // > Base case (i = 1): We show that (INV) holds after the first iteration:
1870
  //     min_int <= iv_post_1 = init + stride <= max_int
1871
  // Proof:
1872
  //     First, we note that (ii) implies
1873
  //         (iii) init <= limit - 1
1874
  //     max_int >= adjusted_limit - 1 + stride   [using (i)]
1875
  //             >= limit - 1 + stride            [using (AL)]
1876
  //             >= init + stride                 [using (iii)]
1877
  //             >= min_int                       [using stride > 0, no underflow]
1878
  // Thus, no overflow happens after the first iteration and (INV) holds for i = 1.
1879
  //
1880
  // Note that to prove the base case we need (i) and (ii).
1881
  //
1882
  // > Induction Hypothesis (i = j, j > 1): Assume that (INV) holds after the j-th iteration:
1883
  //     min_int <= iv_post_j <= max_int
1884
  // > Step case (i = j + 1): We show that (INV) also holds after the j+1-th iteration:
1885
  //     min_int <= iv_post_{j+1} = iv_post_j + stride <= max_int
1886
  // Proof:
1887
  // If iv_post_j >= adjusted_limit:
1888
  //     We exit the loop after the j-th iteration, and we don't execute the j+1-th iteration anymore. Thus, there is
1889
  //     also no iv_{j+1}. Since (INV) holds for iv_j, there is nothing left to prove.
1890
  // If iv_post_j < adjusted_limit:
1891
  //     First, we note that:
1892
  //         (iv) iv_post_j <= adjusted_limit - 1
1893
  //     max_int >= adjusted_limit - 1 + stride    [using (i)]
1894
  //             >= iv_post_j + stride             [using (iv)]
1895
  //             >= min_int                        [using stride > 0, no underflow]
1896
  //
1897
  // Note that to prove the step case we only need (i).
1898
  //
1899
  // Thus, by assuming (i) and (ii), we proved (INV).
1900
  //
1901
  //
1902
  // It is therefore enough to add the following two Loop Limit Check Predicates to check assumptions (i) and (ii):
1903
  //
1904
  // (1) Loop Limit Check Predicate for (i):
1905
  //     Using (i): adjusted_limit - 1 + stride <= max_int
1906
  //
1907
  //     This condition is now restated to use limit instead of adjusted_limit:
1908
  //
1909
  //     To prevent an overflow of adjusted_limit -1 + stride itself, we rewrite this check to
1910
  //         max_int - stride + 1 >= adjusted_limit
1911
  //     We can merge the two constants into
1912
  //         canonicalized_correction = stride - 1
1913
  //     which gives us
1914
  //        max_int - canonicalized_correction >= adjusted_limit
1915
  //
1916
  //     To directly use limit instead of adjusted_limit in the predicate condition, we split adjusted_limit into:
1917
  //         adjusted_limit = limit + limit_correction
1918
  //     Since stride > 0 and limit_correction <= stride + 1, we can restate this with no over- or underflow into:
1919
  //         max_int - canonicalized_correction - limit_correction >= limit
1920
  //     Since canonicalized_correction and limit_correction are both constants, we can replace them with a new constant:
1921
  //         final_correction = canonicalized_correction + limit_correction
1922
  //     which gives us:
1923
  //
1924
  //     Final predicate condition:
1925
  //         max_int - final_correction >= limit
1926
  //
1927
  // (2) Loop Limit Check Predicate for (ii):
1928
  //     Using (ii): init < limit
1929
  //
1930
  //     This Loop Limit Check Predicate is not required if we can prove at compile time that either:
1931
  //        (2.1) type(init) < type(limit)
1932
  //             In this case, we know:
1933
  //                 all possible values of init < all possible values of limit
1934
  //             and we can skip the predicate.
1935
  //
1936
  //        (2.2) init < limit is already checked before (i.e. found as a dominating check)
1937
  //            In this case, we do not need to re-check the condition and can skip the predicate.
1938
  //            This is often found for while- and for-loops which have the following shape:
1939
  //
1940
  //                if (init < limit) { // Dominating test. Do not need the Loop Limit Check Predicate below.
1941
  //                    i = init;
1942
  //                    if (init >= limit) { trap(); } // Here we would insert the Loop Limit Check Predicate
1943
  //                    do {
1944
  //                        i += stride;
1945
  //                    } while (i < limit);
1946
  //                }
1947
  //
1948
  //        (2.3) init + stride <= max_int
1949
  //            In this case, there is no overflow of the iv phi after the first loop iteration.
1950
  //            In the proof of the base case above we showed that init + stride <= max_int by using assumption (ii):
1951
  //                init < limit
1952
  //            In the proof of the step case above, we did not need (ii) anymore. Therefore, if we already know at
1953
  //            compile time that init + stride <= max_int then we have trivially proven the base case and that
1954
  //            there is no overflow of the iv phi after the first iteration. In this case, we don't need to check (ii)
1955
  //            again and can skip the predicate.
1956

1957

1958
  // Accounting for (LE3) and (LE4) where we use pre-incremented phis in the loop exit check.
1959
  const jlong limit_correction_for_pre_iv_exit_check = (phi_incr != nullptr) ? stride_con : 0;
1960

1961
  // Accounting for (LE2) and (LE4) where we use <= or >= in the loop exit check.
1962
  const bool includes_limit = (bt == BoolTest::le || bt == BoolTest::ge);
1963
  const jlong limit_correction_for_le_ge_exit_check = (includes_limit ? (stride_con > 0 ? 1 : -1) : 0);
1964

1965
  const jlong limit_correction = limit_correction_for_pre_iv_exit_check + limit_correction_for_le_ge_exit_check;
1966
  const jlong canonicalized_correction = stride_con + (stride_con > 0 ? -1 : 1);
1967
  const jlong final_correction = canonicalized_correction + limit_correction;
1968

1969
  int sov = check_stride_overflow(final_correction, limit_t, iv_bt);
1970
  Node* init_control = x->in(LoopNode::EntryControl);
1971

1972
  // If sov==0, limit's type always satisfies the condition, for
1973
  // example, when it is an array length.
1974
  if (sov != 0) {
1975
    if (sov < 0) {
1976
      return false;  // Bailout: integer overflow is certain.
1977
    }
1978
    // (1) Loop Limit Check Predicate is required because we could not statically prove that
1979
    //     limit + final_correction = adjusted_limit - 1 + stride <= max_int
1980
    assert(!x->as_Loop()->is_loop_nest_inner_loop(), "loop was transformed");
1981
    const Predicates predicates(init_control);
1982
    const PredicateBlock* loop_limit_check_predicate_block = predicates.loop_limit_check_predicate_block();
1983
    if (!loop_limit_check_predicate_block->has_parse_predicate()) {
1984
      // The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
1985
#ifdef ASSERT
1986
      if (TraceLoopLimitCheck) {
1987
        tty->print("Missing Loop Limit Check Parse Predicate:");
1988
        loop->dump_head();
1989
        x->dump(1);
1990
      }
1991
#endif
1992
      return false;
1993
    }
1994

1995
    ParsePredicateNode* loop_limit_check_parse_predicate = loop_limit_check_predicate_block->parse_predicate();
1996
    if (!is_dominator(get_ctrl(limit), loop_limit_check_parse_predicate->in(0))) {
1997
      return false;
1998
    }
1999

2000
    Node* cmp_limit;
2001
    Node* bol;
2002

2003
    if (stride_con > 0) {
2004
      cmp_limit = CmpNode::make(limit, _igvn.integercon(max_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
2005
      bol = new BoolNode(cmp_limit, BoolTest::le);
2006
    } else {
2007
      cmp_limit = CmpNode::make(limit, _igvn.integercon(min_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
2008
      bol = new BoolNode(cmp_limit, BoolTest::ge);
2009
    }
2010

2011
    insert_loop_limit_check_predicate(init_control->as_IfTrue(), cmp_limit, bol);
2012
  }
2013

2014
  // (2.3)
2015
  const bool init_plus_stride_could_overflow =
2016
          (stride_con > 0 && init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) ||
2017
          (stride_con < 0 && init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con);
2018
  // (2.1)
2019
  const bool init_gte_limit = (stride_con > 0 && init_t->hi_as_long() >= limit_t->lo_as_long()) ||
2020
                              (stride_con < 0 && init_t->lo_as_long() <= limit_t->hi_as_long());
2021

2022
  if (init_gte_limit && // (2.1)
2023
     ((bt == BoolTest::ne || init_plus_stride_could_overflow) && // (2.3)
2024
      !has_dominating_loop_limit_check(init_trip, limit, stride_con, iv_bt, init_control))) { // (2.2)
2025
    // (2) Iteration Loop Limit Check Predicate is required because neither (2.1), (2.2), nor (2.3) holds.
2026
    // We use the following condition:
2027
    // - stride > 0: init < limit
2028
    // - stride < 0: init > limit
2029
    //
2030
    // This predicate is always required if we have a non-equal-operator in the loop exit check (where stride = 1 is
2031
    // a requirement). We transform the loop exit check by using a less-than-operator. By doing so, we must always
2032
    // check that init < limit. Otherwise, we could have a different number of iterations at runtime.
2033

2034
    const Predicates predicates(init_control);
2035
    const PredicateBlock* loop_limit_check_predicate_block = predicates.loop_limit_check_predicate_block();
2036
    if (!loop_limit_check_predicate_block->has_parse_predicate()) {
2037
      // The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
2038
#ifdef ASSERT
2039
      if (TraceLoopLimitCheck) {
2040
        tty->print("Missing Loop Limit Check Parse Predicate:");
2041
        loop->dump_head();
2042
        x->dump(1);
2043
      }
2044
#endif
2045
      return false;
2046
    }
2047

2048
    ParsePredicateNode* loop_limit_check_parse_predicate = loop_limit_check_predicate_block->parse_predicate();
2049
    Node* parse_predicate_entry = loop_limit_check_parse_predicate->in(0);
2050
    if (!is_dominator(get_ctrl(limit), parse_predicate_entry) ||
2051
        !is_dominator(get_ctrl(init_trip), parse_predicate_entry)) {
2052
      return false;
2053
    }
2054

2055
    Node* cmp_limit;
2056
    Node* bol;
2057

2058
    if (stride_con > 0) {
2059
      cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
2060
      bol = new BoolNode(cmp_limit, BoolTest::lt);
2061
    } else {
2062
      cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
2063
      bol = new BoolNode(cmp_limit, BoolTest::gt);
2064
    }
2065

2066
    insert_loop_limit_check_predicate(init_control->as_IfTrue(), cmp_limit, bol);
2067
  }
2068

2069
  if (bt == BoolTest::ne) {
2070
    // Now we need to canonicalize the loop condition if it is 'ne'.
2071
    assert(stride_con == 1 || stride_con == -1, "simple increment only - checked before");
2072
    if (stride_con > 0) {
2073
      // 'ne' can be replaced with 'lt' only when init < limit. This is ensured by the inserted predicate above.
2074
      bt = BoolTest::lt;
2075
    } else {
2076
      assert(stride_con < 0, "must be");
2077
      // 'ne' can be replaced with 'gt' only when init > limit. This is ensured by the inserted predicate above.
2078
      bt = BoolTest::gt;
2079
    }
2080
  }
2081

2082
  Node* sfpt = nullptr;
2083
  if (loop->_child == nullptr) {
2084
    sfpt = find_safepoint(back_control, x, loop);
2085
  } else {
2086
    sfpt = iff->in(0);
2087
    if (sfpt->Opcode() != Op_SafePoint) {
2088
      sfpt = nullptr;
2089
    }
2090
  }
2091

2092
  if (x->in(LoopNode::LoopBackControl)->Opcode() == Op_SafePoint) {
2093
    Node* backedge_sfpt = x->in(LoopNode::LoopBackControl);
2094
    if (((iv_bt == T_INT && LoopStripMiningIter != 0) ||
2095
         iv_bt == T_LONG) &&
2096
        sfpt == nullptr) {
2097
      // Leaving the safepoint on the backedge and creating a
2098
      // CountedLoop will confuse optimizations. We can't move the
2099
      // safepoint around because its jvm state wouldn't match a new
2100
      // location. Give up on that loop.
2101
      return false;
2102
    }
2103
    if (is_deleteable_safept(backedge_sfpt)) {
2104
      lazy_replace(backedge_sfpt, iftrue);
2105
      if (loop->_safepts != nullptr) {
2106
        loop->_safepts->yank(backedge_sfpt);
2107
      }
2108
      loop->_tail = iftrue;
2109
    }
2110
  }
2111

2112

2113
#ifdef ASSERT
2114
  if (iv_bt == T_INT &&
2115
      !x->as_Loop()->is_loop_nest_inner_loop() &&
2116
      StressLongCountedLoop > 0 &&
2117
      trunc1 == nullptr &&
2118
      convert_to_long_loop(cmp, phi, loop)) {
2119
    return false;
2120
  }
2121
#endif
2122

2123
  Node* adjusted_limit = limit;
2124
  if (phi_incr != nullptr) {
2125
    // If compare points directly to the phi we need to adjust
2126
    // the compare so that it points to the incr. Limit have
2127
    // to be adjusted to keep trip count the same and we
2128
    // should avoid int overflow.
2129
    //
2130
    //   i = init; do {} while(i++ < limit);
2131
    // is converted to
2132
    //   i = init; do {} while(++i < limit+1);
2133
    //
2134
    adjusted_limit = gvn->transform(AddNode::make(limit, stride, iv_bt));
2135
  }
2136

2137
  if (includes_limit) {
2138
    // The limit check guaranties that 'limit <= (max_jint - stride)' so
2139
    // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
2140
    //
2141
    Node* one = (stride_con > 0) ? gvn->integercon( 1, iv_bt) : gvn->integercon(-1, iv_bt);
2142
    adjusted_limit = gvn->transform(AddNode::make(adjusted_limit, one, iv_bt));
2143
    if (bt == BoolTest::le)
2144
      bt = BoolTest::lt;
2145
    else if (bt == BoolTest::ge)
2146
      bt = BoolTest::gt;
2147
    else
2148
      ShouldNotReachHere();
2149
  }
2150
  set_subtree_ctrl(adjusted_limit, false);
2151

2152
  // Build a canonical trip test.
2153
  // Clone code, as old values may be in use.
2154
  incr = incr->clone();
2155
  incr->set_req(1,phi);
2156
  incr->set_req(2,stride);
2157
  incr = _igvn.register_new_node_with_optimizer(incr);
2158
  set_early_ctrl(incr, false);
2159
  _igvn.rehash_node_delayed(phi);
2160
  phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
2161

2162
  // If phi type is more restrictive than Int, raise to
2163
  // Int to prevent (almost) infinite recursion in igvn
2164
  // which can only handle integer types for constants or minint..maxint.
2165
  if (!TypeInteger::bottom(iv_bt)->higher_equal(phi->bottom_type())) {
2166
    Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInteger::bottom(iv_bt));
2167
    nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
2168
    nphi = _igvn.register_new_node_with_optimizer(nphi);
2169
    set_ctrl(nphi, get_ctrl(phi));
2170
    _igvn.replace_node(phi, nphi);
2171
    phi = nphi->as_Phi();
2172
  }
2173
  cmp = cmp->clone();
2174
  cmp->set_req(1,incr);
2175
  cmp->set_req(2, adjusted_limit);
2176
  cmp = _igvn.register_new_node_with_optimizer(cmp);
2177
  set_ctrl(cmp, iff->in(0));
2178

2179
  test = test->clone()->as_Bool();
2180
  (*(BoolTest*)&test->_test)._test = bt;
2181
  test->set_req(1,cmp);
2182
  _igvn.register_new_node_with_optimizer(test);
2183
  set_ctrl(test, iff->in(0));
2184

2185
  // Replace the old IfNode with a new LoopEndNode
2186
  Node *lex = _igvn.register_new_node_with_optimizer(BaseCountedLoopEndNode::make(iff->in(0), test, cl_prob, iff->as_If()->_fcnt, iv_bt));
2187
  IfNode *le = lex->as_If();
2188
  uint dd = dom_depth(iff);
2189
  set_idom(le, le->in(0), dd); // Update dominance for loop exit
2190
  set_loop(le, loop);
2191

2192
  // Get the loop-exit control
2193
  Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
2194

2195
  // Need to swap loop-exit and loop-back control?
2196
  if (iftrue_op == Op_IfFalse) {
2197
    Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
2198
    Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
2199

2200
    loop->_tail = back_control = ift2;
2201
    set_loop(ift2, loop);
2202
    set_loop(iff2, get_loop(iffalse));
2203

2204
    // Lazy update of 'get_ctrl' mechanism.
2205
    lazy_replace(iffalse, iff2);
2206
    lazy_replace(iftrue,  ift2);
2207

2208
    // Swap names
2209
    iffalse = iff2;
2210
    iftrue  = ift2;
2211
  } else {
2212
    _igvn.rehash_node_delayed(iffalse);
2213
    _igvn.rehash_node_delayed(iftrue);
2214
    iffalse->set_req_X( 0, le, &_igvn );
2215
    iftrue ->set_req_X( 0, le, &_igvn );
2216
  }
2217

2218
  set_idom(iftrue,  le, dd+1);
2219
  set_idom(iffalse, le, dd+1);
2220
  assert(iff->outcnt() == 0, "should be dead now");
2221
  lazy_replace( iff, le ); // fix 'get_ctrl'
2222

2223
  Node* entry_control = init_control;
2224
  bool strip_mine_loop = iv_bt == T_INT &&
2225
                         loop->_child == nullptr &&
2226
                         sfpt != nullptr &&
2227
                         !loop->_has_call &&
2228
                         is_deleteable_safept(sfpt);
2229
  IdealLoopTree* outer_ilt = nullptr;
2230
  if (strip_mine_loop) {
2231
    outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
2232
                                              cl_prob, le->_fcnt, entry_control,
2233
                                              iffalse);
2234
  }
2235

2236
  // Now setup a new CountedLoopNode to replace the existing LoopNode
2237
  BaseCountedLoopNode *l = BaseCountedLoopNode::make(entry_control, back_control, iv_bt);
2238
  l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
2239
  // The following assert is approximately true, and defines the intention
2240
  // of can_be_counted_loop.  It fails, however, because phase->type
2241
  // is not yet initialized for this loop and its parts.
2242
  //assert(l->can_be_counted_loop(this), "sanity");
2243
  _igvn.register_new_node_with_optimizer(l);
2244
  set_loop(l, loop);
2245
  loop->_head = l;
2246
  // Fix all data nodes placed at the old loop head.
2247
  // Uses the lazy-update mechanism of 'get_ctrl'.
2248
  lazy_replace( x, l );
2249
  set_idom(l, entry_control, dom_depth(entry_control) + 1);
2250

2251
  if (iv_bt == T_INT && (LoopStripMiningIter == 0 || strip_mine_loop)) {
2252
    // Check for immediately preceding SafePoint and remove
2253
    if (sfpt != nullptr && (strip_mine_loop || is_deleteable_safept(sfpt))) {
2254
      if (strip_mine_loop) {
2255
        Node* outer_le = outer_ilt->_tail->in(0);
2256
        Node* sfpt_clone = sfpt->clone();
2257
        sfpt_clone->set_req(0, iffalse);
2258
        outer_le->set_req(0, sfpt_clone);
2259

2260
        Node* polladdr = sfpt_clone->in(TypeFunc::Parms);
2261
        if (polladdr != nullptr && polladdr->is_Load()) {
2262
          // Polling load should be pinned outside inner loop.
2263
          Node* new_polladdr = polladdr->clone();
2264
          new_polladdr->set_req(0, iffalse);
2265
          _igvn.register_new_node_with_optimizer(new_polladdr, polladdr);
2266
          set_ctrl(new_polladdr, iffalse);
2267
          sfpt_clone->set_req(TypeFunc::Parms, new_polladdr);
2268
        }
2269
        // When this code runs, loop bodies have not yet been populated.
2270
        const bool body_populated = false;
2271
        register_control(sfpt_clone, outer_ilt, iffalse, body_populated);
2272
        set_idom(outer_le, sfpt_clone, dom_depth(sfpt_clone));
2273
      }
2274
      lazy_replace(sfpt, sfpt->in(TypeFunc::Control));
2275
      if (loop->_safepts != nullptr) {
2276
        loop->_safepts->yank(sfpt);
2277
      }
2278
    }
2279
  }
2280

2281
#ifdef ASSERT
2282
  assert(l->is_valid_counted_loop(iv_bt), "counted loop shape is messed up");
2283
  assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
2284
#endif
2285
#ifndef PRODUCT
2286
  if (TraceLoopOpts) {
2287
    tty->print("Counted      ");
2288
    loop->dump_head();
2289
  }
2290
#endif
2291

2292
  C->print_method(PHASE_AFTER_CLOOPS, 3, l);
2293

2294
  // Capture bounds of the loop in the induction variable Phi before
2295
  // subsequent transformation (iteration splitting) obscures the
2296
  // bounds
2297
  l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
2298

2299
  if (strip_mine_loop) {
2300
    l->mark_strip_mined();
2301
    l->verify_strip_mined(1);
2302
    outer_ilt->_head->as_Loop()->verify_strip_mined(1);
2303
    loop = outer_ilt;
2304
  }
2305

2306
#ifndef PRODUCT
2307
  if (x->as_Loop()->is_loop_nest_inner_loop() && iv_bt == T_LONG) {
2308
    Atomic::inc(&_long_loop_counted_loops);
2309
  }
2310
#endif
2311
  if (iv_bt == T_LONG && x->as_Loop()->is_loop_nest_outer_loop()) {
2312
    l->mark_loop_nest_outer_loop();
2313
  }
2314

2315
  return true;
2316
}
2317

2318
// Check if there is a dominating loop limit check of the form 'init < limit' starting at the loop entry.
2319
// If there is one, then we do not need to create an additional Loop Limit Check Predicate.
2320
bool PhaseIdealLoop::has_dominating_loop_limit_check(Node* init_trip, Node* limit, const jlong stride_con,
2321
                                                     const BasicType iv_bt, Node* loop_entry) {
2322
  // Eagerly call transform() on the Cmp and Bool node to common them up if possible. This is required in order to
2323
  // successfully find a dominated test with the If node below.
2324
  Node* cmp_limit;
2325
  Node* bol;
2326
  if (stride_con > 0) {
2327
    cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
2328
    bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::lt));
2329
  } else {
2330
    cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
2331
    bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::gt));
2332
  }
2333

2334
  // Check if there is already a dominating init < limit check. If so, we do not need a Loop Limit Check Predicate.
2335
  IfNode* iff = new IfNode(loop_entry, bol, PROB_MIN, COUNT_UNKNOWN);
2336
  // Also add fake IfProj nodes in order to call transform() on the newly created IfNode.
2337
  IfFalseNode* if_false = new IfFalseNode(iff);
2338
  IfTrueNode* if_true = new IfTrueNode(iff);
2339
  Node* dominated_iff = _igvn.transform(iff);
2340
  // ConI node? Found dominating test (IfNode::dominated_by() returns a ConI node).
2341
  const bool found_dominating_test = dominated_iff != nullptr && dominated_iff->is_ConI();
2342

2343
  // Kill the If with its projections again in the next IGVN round by cutting it off from the graph.
2344
  _igvn.replace_input_of(iff, 0, C->top());
2345
  _igvn.replace_input_of(iff, 1, C->top());
2346
  return found_dominating_test;
2347
}
2348

2349
//----------------------exact_limit-------------------------------------------
2350
Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
2351
  assert(loop->_head->is_CountedLoop(), "");
2352
  CountedLoopNode *cl = loop->_head->as_CountedLoop();
2353
  assert(cl->is_valid_counted_loop(T_INT), "");
2354

2355
  if (cl->stride_con() == 1 ||
2356
      cl->stride_con() == -1 ||
2357
      cl->limit()->Opcode() == Op_LoopLimit) {
2358
    // Old code has exact limit (it could be incorrect in case of int overflow).
2359
    // Loop limit is exact with stride == 1. And loop may already have exact limit.
2360
    return cl->limit();
2361
  }
2362
  Node *limit = nullptr;
2363
#ifdef ASSERT
2364
  BoolTest::mask bt = cl->loopexit()->test_trip();
2365
  assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
2366
#endif
2367
  if (cl->has_exact_trip_count()) {
2368
    // Simple case: loop has constant boundaries.
2369
    // Use jlongs to avoid integer overflow.
2370
    int stride_con = cl->stride_con();
2371
    jlong  init_con = cl->init_trip()->get_int();
2372
    jlong limit_con = cl->limit()->get_int();
2373
    julong trip_cnt = cl->trip_count();
2374
    jlong final_con = init_con + trip_cnt*stride_con;
2375
    int final_int = (int)final_con;
2376
    // The final value should be in integer range since the loop
2377
    // is counted and the limit was checked for overflow.
2378
    assert(final_con == (jlong)final_int, "final value should be integer");
2379
    limit = _igvn.intcon(final_int);
2380
  } else {
2381
    // Create new LoopLimit node to get exact limit (final iv value).
2382
    limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
2383
    register_new_node(limit, cl->in(LoopNode::EntryControl));
2384
  }
2385
  assert(limit != nullptr, "sanity");
2386
  return limit;
2387
}
2388

2389
//------------------------------Ideal------------------------------------------
2390
// Return a node which is more "ideal" than the current node.
2391
// Attempt to convert into a counted-loop.
2392
Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2393
  if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
2394
    phase->C->set_major_progress();
2395
  }
2396
  return RegionNode::Ideal(phase, can_reshape);
2397
}
2398

2399
#ifdef ASSERT
2400
void LoopNode::verify_strip_mined(int expect_skeleton) const {
2401
  const OuterStripMinedLoopNode* outer = nullptr;
2402
  const CountedLoopNode* inner = nullptr;
2403
  if (is_strip_mined()) {
2404
    if (!is_valid_counted_loop(T_INT)) {
2405
      return; // Skip malformed counted loop
2406
    }
2407
    assert(is_CountedLoop(), "no Loop should be marked strip mined");
2408
    inner = as_CountedLoop();
2409
    outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
2410
  } else if (is_OuterStripMinedLoop()) {
2411
    outer = this->as_OuterStripMinedLoop();
2412
    inner = outer->unique_ctrl_out()->as_CountedLoop();
2413
    assert(inner->is_valid_counted_loop(T_INT) && inner->is_strip_mined(), "OuterStripMinedLoop should have been removed");
2414
    assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
2415
  }
2416
  if (inner != nullptr || outer != nullptr) {
2417
    assert(inner != nullptr && outer != nullptr, "missing loop in strip mined nest");
2418
    Node* outer_tail = outer->in(LoopNode::LoopBackControl);
2419
    Node* outer_le = outer_tail->in(0);
2420
    assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
2421
    Node* sfpt = outer_le->in(0);
2422
    assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
2423
    Node* inner_out = sfpt->in(0);
2424
    CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
2425
    assert(cle == inner->loopexit_or_null(), "mismatch");
2426
    bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
2427
    if (has_skeleton) {
2428
      assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
2429
      assert(outer->outcnt() == 2, "only control nodes");
2430
    } else {
2431
      assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
2432
      uint phis = 0;
2433
      uint be_loads = 0;
2434
      Node* be = inner->in(LoopNode::LoopBackControl);
2435
      for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
2436
        Node* u = inner->fast_out(i);
2437
        if (u->is_Phi()) {
2438
          phis++;
2439
          for (DUIterator_Fast jmax, j = be->fast_outs(jmax); j < jmax; j++) {
2440
            Node* n = be->fast_out(j);
2441
            if (n->is_Load()) {
2442
              assert(n->in(0) == be || n->find_prec_edge(be) > 0, "should be on the backedge");
2443
              do {
2444
                n = n->raw_out(0);
2445
              } while (!n->is_Phi());
2446
              if (n == u) {
2447
                be_loads++;
2448
                break;
2449
              }
2450
            }
2451
          }
2452
        }
2453
      }
2454
      assert(be_loads <= phis, "wrong number phis that depends on a pinned load");
2455
      for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
2456
        Node* u = outer->fast_out(i);
2457
        assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
2458
      }
2459
      uint stores = 0;
2460
      for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
2461
        Node* u = inner_out->fast_out(i);
2462
        if (u->is_Store()) {
2463
          stores++;
2464
        }
2465
      }
2466
      // Late optimization of loads on backedge can cause Phi of outer loop to be eliminated but Phi of inner loop is
2467
      // not guaranteed to be optimized out.
2468
      assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
2469
    }
2470
    assert(sfpt->outcnt() == 1, "no data node");
2471
    assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
2472
  }
2473
}
2474
#endif
2475

2476
//=============================================================================
2477
//------------------------------Ideal------------------------------------------
2478
// Return a node which is more "ideal" than the current node.
2479
// Attempt to convert into a counted-loop.
2480
Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2481
  return RegionNode::Ideal(phase, can_reshape);
2482
}
2483

2484
//------------------------------dump_spec--------------------------------------
2485
// Dump special per-node info
2486
#ifndef PRODUCT
2487
void CountedLoopNode::dump_spec(outputStream *st) const {
2488
  LoopNode::dump_spec(st);
2489
  if (stride_is_con()) {
2490
    st->print("stride: %d ",stride_con());
2491
  }
2492
  if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
2493
  if (is_main_loop()) st->print("main of N%d", _idx);
2494
  if (is_post_loop()) st->print("post of N%d", _main_idx);
2495
  if (is_strip_mined()) st->print(" strip mined");
2496
}
2497
#endif
2498

2499
//=============================================================================
2500
jlong BaseCountedLoopEndNode::stride_con() const {
2501
  return stride()->bottom_type()->is_integer(bt())->get_con_as_long(bt());
2502
}
2503

2504

2505
BaseCountedLoopEndNode* BaseCountedLoopEndNode::make(Node* control, Node* test, float prob, float cnt, BasicType bt) {
2506
  if (bt == T_INT) {
2507
    return new CountedLoopEndNode(control, test, prob, cnt);
2508
  }
2509
  assert(bt == T_LONG, "unsupported");
2510
  return new LongCountedLoopEndNode(control, test, prob, cnt);
2511
}
2512

2513
//=============================================================================
2514
//------------------------------Value-----------------------------------------
2515
const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
2516
  const Type* init_t   = phase->type(in(Init));
2517
  const Type* limit_t  = phase->type(in(Limit));
2518
  const Type* stride_t = phase->type(in(Stride));
2519
  // Either input is TOP ==> the result is TOP
2520
  if (init_t   == Type::TOP) return Type::TOP;
2521
  if (limit_t  == Type::TOP) return Type::TOP;
2522
  if (stride_t == Type::TOP) return Type::TOP;
2523

2524
  int stride_con = stride_t->is_int()->get_con();
2525
  if (stride_con == 1)
2526
    return bottom_type();  // Identity
2527

2528
  if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
2529
    // Use jlongs to avoid integer overflow.
2530
    jlong init_con   =  init_t->is_int()->get_con();
2531
    jlong limit_con  = limit_t->is_int()->get_con();
2532
    int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
2533
    jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
2534
    jlong final_con  = init_con + stride_con*trip_count;
2535
    int final_int = (int)final_con;
2536
    // The final value should be in integer range since the loop
2537
    // is counted and the limit was checked for overflow.
2538
    // Assert checks for overflow only if all input nodes are ConINodes, as during CCP
2539
    // there might be a temporary overflow from PhiNodes see JDK-8309266
2540
    assert((in(Init)->is_ConI() && in(Limit)->is_ConI() && in(Stride)->is_ConI()) ? final_con == (jlong)final_int : true, "final value should be integer");
2541
    if (final_con == (jlong)final_int) {
2542
      return TypeInt::make(final_int);
2543
    } else {
2544
      return bottom_type();
2545
    }
2546
  }
2547

2548
  return bottom_type(); // TypeInt::INT
2549
}
2550

2551
//------------------------------Ideal------------------------------------------
2552
// Return a node which is more "ideal" than the current node.
2553
Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2554
  if (phase->type(in(Init))   == Type::TOP ||
2555
      phase->type(in(Limit))  == Type::TOP ||
2556
      phase->type(in(Stride)) == Type::TOP)
2557
    return nullptr;  // Dead
2558

2559
  int stride_con = phase->type(in(Stride))->is_int()->get_con();
2560
  if (stride_con == 1)
2561
    return nullptr;  // Identity
2562

2563
  if (in(Init)->is_Con() && in(Limit)->is_Con())
2564
    return nullptr;  // Value
2565

2566
  // Delay following optimizations until all loop optimizations
2567
  // done to keep Ideal graph simple.
2568
  if (!can_reshape || !phase->C->post_loop_opts_phase()) {
2569
    return nullptr;
2570
  }
2571

2572
  const TypeInt* init_t  = phase->type(in(Init) )->is_int();
2573
  const TypeInt* limit_t = phase->type(in(Limit))->is_int();
2574
  int stride_p;
2575
  jlong lim, ini;
2576
  julong max;
2577
  if (stride_con > 0) {
2578
    stride_p = stride_con;
2579
    lim = limit_t->_hi;
2580
    ini = init_t->_lo;
2581
    max = (julong)max_jint;
2582
  } else {
2583
    stride_p = -stride_con;
2584
    lim = init_t->_hi;
2585
    ini = limit_t->_lo;
2586
    max = (julong)min_jint;
2587
  }
2588
  julong range = lim - ini + stride_p;
2589
  if (range <= max) {
2590
    // Convert to integer expression if it is not overflow.
2591
    Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
2592
    Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
2593
    Node *bias  = phase->transform(new AddINode(range, stride_m));
2594
    Node *trip  = phase->transform(new DivINode(nullptr, bias, in(Stride)));
2595
    Node *span  = phase->transform(new MulINode(trip, in(Stride)));
2596
    return new AddINode(span, in(Init)); // exact limit
2597
  }
2598

2599
  if (is_power_of_2(stride_p) ||                // divisor is 2^n
2600
      !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
2601
    // Convert to long expression to avoid integer overflow
2602
    // and let igvn optimizer convert this division.
2603
    //
2604
    Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
2605
    Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
2606
    Node* stride   = phase->longcon(stride_con);
2607
    Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
2608

2609
    Node *range = phase->transform(new SubLNode(limit, init));
2610
    Node *bias  = phase->transform(new AddLNode(range, stride_m));
2611
    Node *span;
2612
    if (stride_con > 0 && is_power_of_2(stride_p)) {
2613
      // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
2614
      // and avoid generating rounding for division. Zero trip guard should
2615
      // guarantee that init < limit but sometimes the guard is missing and
2616
      // we can get situation when init > limit. Note, for the empty loop
2617
      // optimization zero trip guard is generated explicitly which leaves
2618
      // only RCE predicate where exact limit is used and the predicate
2619
      // will simply fail forcing recompilation.
2620
      Node* neg_stride   = phase->longcon(-stride_con);
2621
      span = phase->transform(new AndLNode(bias, neg_stride));
2622
    } else {
2623
      Node *trip  = phase->transform(new DivLNode(nullptr, bias, stride));
2624
      span = phase->transform(new MulLNode(trip, stride));
2625
    }
2626
    // Convert back to int
2627
    Node *span_int = phase->transform(new ConvL2INode(span));
2628
    return new AddINode(span_int, in(Init)); // exact limit
2629
  }
2630

2631
  return nullptr;    // No progress
2632
}
2633

2634
//------------------------------Identity---------------------------------------
2635
// If stride == 1 return limit node.
2636
Node* LoopLimitNode::Identity(PhaseGVN* phase) {
2637
  int stride_con = phase->type(in(Stride))->is_int()->get_con();
2638
  if (stride_con == 1 || stride_con == -1)
2639
    return in(Limit);
2640
  return this;
2641
}
2642

2643
//=============================================================================
2644
//----------------------match_incr_with_optional_truncation--------------------
2645
// Match increment with optional truncation:
2646
// CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
2647
// Return null for failure. Success returns the increment node.
2648
Node* CountedLoopNode::match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2,
2649
                                                           const TypeInteger** trunc_type,
2650
                                                           BasicType bt) {
2651
  // Quick cutouts:
2652
  if (expr == nullptr || expr->req() != 3)  return nullptr;
2653

2654
  Node *t1 = nullptr;
2655
  Node *t2 = nullptr;
2656
  Node* n1 = expr;
2657
  int   n1op = n1->Opcode();
2658
  const TypeInteger* trunc_t = TypeInteger::bottom(bt);
2659

2660
  if (bt == T_INT) {
2661
    // Try to strip (n1 & M) or (n1 << N >> N) from n1.
2662
    if (n1op == Op_AndI &&
2663
        n1->in(2)->is_Con() &&
2664
        n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
2665
      // %%% This check should match any mask of 2**K-1.
2666
      t1 = n1;
2667
      n1 = t1->in(1);
2668
      n1op = n1->Opcode();
2669
      trunc_t = TypeInt::CHAR;
2670
    } else if (n1op == Op_RShiftI &&
2671
               n1->in(1) != nullptr &&
2672
               n1->in(1)->Opcode() == Op_LShiftI &&
2673
               n1->in(2) == n1->in(1)->in(2) &&
2674
               n1->in(2)->is_Con()) {
2675
      jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
2676
      // %%% This check should match any shift in [1..31].
2677
      if (shift == 16 || shift == 8) {
2678
        t1 = n1;
2679
        t2 = t1->in(1);
2680
        n1 = t2->in(1);
2681
        n1op = n1->Opcode();
2682
        if (shift == 16) {
2683
          trunc_t = TypeInt::SHORT;
2684
        } else if (shift == 8) {
2685
          trunc_t = TypeInt::BYTE;
2686
        }
2687
      }
2688
    }
2689
  }
2690

2691
  // If (maybe after stripping) it is an AddI, we won:
2692
  if (n1op == Op_Add(bt)) {
2693
    *trunc1 = t1;
2694
    *trunc2 = t2;
2695
    *trunc_type = trunc_t;
2696
    return n1;
2697
  }
2698

2699
  // failed
2700
  return nullptr;
2701
}
2702

2703
LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
2704
  if (is_strip_mined() && in(EntryControl) != nullptr && in(EntryControl)->is_OuterStripMinedLoop()) {
2705
    verify_strip_mined(expect_skeleton);
2706
    return in(EntryControl)->as_Loop();
2707
  }
2708
  return this;
2709
}
2710

2711
OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
2712
  assert(is_strip_mined(), "not a strip mined loop");
2713
  Node* c = in(EntryControl);
2714
  if (c == nullptr || c->is_top() || !c->is_OuterStripMinedLoop()) {
2715
    return nullptr;
2716
  }
2717
  return c->as_OuterStripMinedLoop();
2718
}
2719

2720
IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
2721
  Node* c = in(LoopBackControl);
2722
  if (c == nullptr || c->is_top()) {
2723
    return nullptr;
2724
  }
2725
  return c->as_IfTrue();
2726
}
2727

2728
IfTrueNode* CountedLoopNode::outer_loop_tail() const {
2729
  LoopNode* l = outer_loop();
2730
  if (l == nullptr) {
2731
    return nullptr;
2732
  }
2733
  return l->outer_loop_tail();
2734
}
2735

2736
OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
2737
  IfTrueNode* proj = outer_loop_tail();
2738
  if (proj == nullptr) {
2739
    return nullptr;
2740
  }
2741
  Node* c = proj->in(0);
2742
  if (c == nullptr || c->is_top() || c->outcnt() != 2) {
2743
    return nullptr;
2744
  }
2745
  return c->as_OuterStripMinedLoopEnd();
2746
}
2747

2748
OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
2749
  LoopNode* l = outer_loop();
2750
  if (l == nullptr) {
2751
    return nullptr;
2752
  }
2753
  return l->outer_loop_end();
2754
}
2755

2756
IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
2757
  IfNode* le = outer_loop_end();
2758
  if (le == nullptr) {
2759
    return nullptr;
2760
  }
2761
  Node* c = le->proj_out_or_null(false);
2762
  if (c == nullptr) {
2763
    return nullptr;
2764
  }
2765
  return c->as_IfFalse();
2766
}
2767

2768
IfFalseNode* CountedLoopNode::outer_loop_exit() const {
2769
  LoopNode* l = outer_loop();
2770
  if (l == nullptr) {
2771
    return nullptr;
2772
  }
2773
  return l->outer_loop_exit();
2774
}
2775

2776
SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
2777
  IfNode* le = outer_loop_end();
2778
  if (le == nullptr) {
2779
    return nullptr;
2780
  }
2781
  Node* c = le->in(0);
2782
  if (c == nullptr || c->is_top()) {
2783
    return nullptr;
2784
  }
2785
  assert(c->Opcode() == Op_SafePoint, "broken outer loop");
2786
  return c->as_SafePoint();
2787
}
2788

2789
SafePointNode* CountedLoopNode::outer_safepoint() const {
2790
  LoopNode* l = outer_loop();
2791
  if (l == nullptr) {
2792
    return nullptr;
2793
  }
2794
  return l->outer_safepoint();
2795
}
2796

2797
Node* CountedLoopNode::skip_assertion_predicates_with_halt() {
2798
  Node* ctrl = in(LoopNode::EntryControl);
2799
  if (is_main_loop()) {
2800
    ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
2801
  }
2802
  if (is_main_loop() || is_post_loop()) {
2803
    AssertionPredicatesWithHalt assertion_predicates(ctrl);
2804
    return assertion_predicates.entry();
2805
  }
2806
  return ctrl;
2807
}
2808

2809

2810
int CountedLoopNode::stride_con() const {
2811
  CountedLoopEndNode* cle = loopexit_or_null();
2812
  return cle != nullptr ? cle->stride_con() : 0;
2813
}
2814

2815
BaseCountedLoopNode* BaseCountedLoopNode::make(Node* entry, Node* backedge, BasicType bt) {
2816
  if (bt == T_INT) {
2817
    return new CountedLoopNode(entry, backedge);
2818
  }
2819
  assert(bt == T_LONG, "unsupported");
2820
  return new LongCountedLoopNode(entry, backedge);
2821
}
2822

2823
void OuterStripMinedLoopNode::fix_sunk_stores(CountedLoopEndNode* inner_cle, LoopNode* inner_cl, PhaseIterGVN* igvn,
2824
                                              PhaseIdealLoop* iloop) {
2825
  Node* cle_out = inner_cle->proj_out(false);
2826
  Node* cle_tail = inner_cle->proj_out(true);
2827
  if (cle_out->outcnt() > 1) {
2828
    // Look for chains of stores that were sunk
2829
    // out of the inner loop and are in the outer loop
2830
    for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
2831
      Node* u = cle_out->fast_out(i);
2832
      if (u->is_Store()) {
2833
        int alias_idx = igvn->C->get_alias_index(u->adr_type());
2834
        Node* first = u;
2835
        for (;;) {
2836
          Node* next = first->in(MemNode::Memory);
2837
          if (!next->is_Store() || next->in(0) != cle_out) {
2838
            break;
2839
          }
2840
          assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
2841
          first = next;
2842
        }
2843
        Node* last = u;
2844
        for (;;) {
2845
          Node* next = nullptr;
2846
          for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
2847
            Node* uu = last->fast_out(j);
2848
            if (uu->is_Store() && uu->in(0) == cle_out) {
2849
              assert(next == nullptr, "only one in the outer loop");
2850
              next = uu;
2851
              assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
2852
            }
2853
          }
2854
          if (next == nullptr) {
2855
            break;
2856
          }
2857
          last = next;
2858
        }
2859
        Node* phi = nullptr;
2860
        for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
2861
          Node* uu = inner_cl->fast_out(j);
2862
          if (uu->is_Phi()) {
2863
            Node* be = uu->in(LoopNode::LoopBackControl);
2864
            if (be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)) {
2865
              assert(igvn->C->get_alias_index(uu->adr_type()) != alias_idx && igvn->C->get_alias_index(uu->adr_type()) != Compile::AliasIdxBot, "unexpected store");
2866
            }
2867
            if (be == last || be == first->in(MemNode::Memory)) {
2868
              assert(igvn->C->get_alias_index(uu->adr_type()) == alias_idx || igvn->C->get_alias_index(uu->adr_type()) == Compile::AliasIdxBot, "unexpected alias");
2869
              assert(phi == nullptr, "only one phi");
2870
              phi = uu;
2871
            }
2872
          }
2873
        }
2874
#ifdef ASSERT
2875
        for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
2876
          Node* uu = inner_cl->fast_out(j);
2877
          if (uu->is_memory_phi()) {
2878
            if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
2879
              assert(phi == uu, "what's that phi?");
2880
            } else if (uu->adr_type() == TypePtr::BOTTOM) {
2881
              Node* n = uu->in(LoopNode::LoopBackControl);
2882
              uint limit = igvn->C->live_nodes();
2883
              uint i = 0;
2884
              while (n != uu) {
2885
                i++;
2886
                assert(i < limit, "infinite loop");
2887
                if (n->is_Proj()) {
2888
                  n = n->in(0);
2889
                } else if (n->is_SafePoint() || n->is_MemBar()) {
2890
                  n = n->in(TypeFunc::Memory);
2891
                } else if (n->is_Phi()) {
2892
                  n = n->in(1);
2893
                } else if (n->is_MergeMem()) {
2894
                  n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
2895
                } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
2896
                  n = n->in(MemNode::Memory);
2897
                } else {
2898
                  n->dump();
2899
                  ShouldNotReachHere();
2900
                }
2901
              }
2902
            }
2903
          }
2904
        }
2905
#endif
2906
        if (phi == nullptr) {
2907
          // If an entire chains was sunk, the
2908
          // inner loop has no phi for that memory
2909
          // slice, create one for the outer loop
2910
          phi = PhiNode::make(inner_cl, first->in(MemNode::Memory), Type::MEMORY,
2911
                              igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
2912
          phi->set_req(LoopNode::LoopBackControl, last);
2913
          phi = register_new_node(phi, inner_cl, igvn, iloop);
2914
          igvn->replace_input_of(first, MemNode::Memory, phi);
2915
        } else {
2916
          // Or fix the outer loop fix to include
2917
          // that chain of stores.
2918
          Node* be = phi->in(LoopNode::LoopBackControl);
2919
          assert(!(be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)), "store on the backedge + sunk stores: unsupported");
2920
          if (be == first->in(MemNode::Memory)) {
2921
            if (be == phi->in(LoopNode::LoopBackControl)) {
2922
              igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
2923
            } else {
2924
              igvn->replace_input_of(be, MemNode::Memory, last);
2925
            }
2926
          } else {
2927
#ifdef ASSERT
2928
            if (be == phi->in(LoopNode::LoopBackControl)) {
2929
              assert(phi->in(LoopNode::LoopBackControl) == last, "");
2930
            } else {
2931
              assert(be->in(MemNode::Memory) == last, "");
2932
            }
2933
#endif
2934
          }
2935
        }
2936
      }
2937
    }
2938
  }
2939
}
2940

2941
void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
2942
  // Look for the outer & inner strip mined loop, reduce number of
2943
  // iterations of the inner loop, set exit condition of outer loop,
2944
  // construct required phi nodes for outer loop.
2945
  CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
2946
  assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
2947
  if (LoopStripMiningIter == 0) {
2948
    remove_outer_loop_and_safepoint(igvn);
2949
    return;
2950
  }
2951
  if (LoopStripMiningIter == 1) {
2952
    transform_to_counted_loop(igvn, nullptr);
2953
    return;
2954
  }
2955
  Node* inner_iv_phi = inner_cl->phi();
2956
  if (inner_iv_phi == nullptr) {
2957
    IfNode* outer_le = outer_loop_end();
2958
    Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
2959
    igvn->replace_node(outer_le, iff);
2960
    inner_cl->clear_strip_mined();
2961
    return;
2962
  }
2963
  CountedLoopEndNode* inner_cle = inner_cl->loopexit();
2964

2965
  int stride = inner_cl->stride_con();
2966
  // For a min int stride, LoopStripMiningIter * stride overflows the int range for all values of LoopStripMiningIter
2967
  // except 0 or 1. Those values are handled early on in this method and causes the method to return. So for a min int
2968
  // stride, the method is guaranteed to return at the next check below.
2969
  jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS((jlong)stride);
2970
  int scaled_iters = (int)scaled_iters_long;
2971
  if ((jlong)scaled_iters != scaled_iters_long) {
2972
    // Remove outer loop and safepoint (too few iterations)
2973
    remove_outer_loop_and_safepoint(igvn);
2974
    return;
2975
  }
2976
  jlong short_scaled_iters = LoopStripMiningIterShortLoop * ABS(stride);
2977
  const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
2978
  jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
2979
  assert(iter_estimate > 0, "broken");
2980
  if (iter_estimate <= short_scaled_iters) {
2981
    // Remove outer loop and safepoint: loop executes less than LoopStripMiningIterShortLoop
2982
    remove_outer_loop_and_safepoint(igvn);
2983
    return;
2984
  }
2985
  if (iter_estimate <= scaled_iters_long) {
2986
    // We would only go through one iteration of
2987
    // the outer loop: drop the outer loop but
2988
    // keep the safepoint so we don't run for
2989
    // too long without a safepoint
2990
    IfNode* outer_le = outer_loop_end();
2991
    Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
2992
    igvn->replace_node(outer_le, iff);
2993
    inner_cl->clear_strip_mined();
2994
    return;
2995
  }
2996

2997
  Node* cle_tail = inner_cle->proj_out(true);
2998
  ResourceMark rm;
2999
  Node_List old_new;
3000
  if (cle_tail->outcnt() > 1) {
3001
    // Look for nodes on backedge of inner loop and clone them
3002
    Unique_Node_List backedge_nodes;
3003
    for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
3004
      Node* u = cle_tail->fast_out(i);
3005
      if (u != inner_cl) {
3006
        assert(!u->is_CFG(), "control flow on the backedge?");
3007
        backedge_nodes.push(u);
3008
      }
3009
    }
3010
    uint last = igvn->C->unique();
3011
    for (uint next = 0; next < backedge_nodes.size(); next++) {
3012
      Node* n = backedge_nodes.at(next);
3013
      old_new.map(n->_idx, n->clone());
3014
      for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3015
        Node* u = n->fast_out(i);
3016
        assert(!u->is_CFG(), "broken");
3017
        if (u->_idx >= last) {
3018
          continue;
3019
        }
3020
        if (!u->is_Phi()) {
3021
          backedge_nodes.push(u);
3022
        } else {
3023
          assert(u->in(0) == inner_cl, "strange phi on the backedge");
3024
        }
3025
      }
3026
    }
3027
    // Put the clones on the outer loop backedge
3028
    Node* le_tail = outer_loop_tail();
3029
    for (uint next = 0; next < backedge_nodes.size(); next++) {
3030
      Node *n = old_new[backedge_nodes.at(next)->_idx];
3031
      for (uint i = 1; i < n->req(); i++) {
3032
        if (n->in(i) != nullptr && old_new[n->in(i)->_idx] != nullptr) {
3033
          n->set_req(i, old_new[n->in(i)->_idx]);
3034
        }
3035
      }
3036
      if (n->in(0) != nullptr && n->in(0) == cle_tail) {
3037
        n->set_req(0, le_tail);
3038
      }
3039
      igvn->register_new_node_with_optimizer(n);
3040
    }
3041
  }
3042

3043
  Node* iv_phi = nullptr;
3044
  // Make a clone of each phi in the inner loop
3045
  // for the outer loop
3046
  for (uint i = 0; i < inner_cl->outcnt(); i++) {
3047
    Node* u = inner_cl->raw_out(i);
3048
    if (u->is_Phi()) {
3049
      assert(u->in(0) == inner_cl, "inconsistent");
3050
      Node* phi = u->clone();
3051
      phi->set_req(0, this);
3052
      Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
3053
      if (be != nullptr) {
3054
        phi->set_req(LoopNode::LoopBackControl, be);
3055
      }
3056
      phi = igvn->transform(phi);
3057
      igvn->replace_input_of(u, LoopNode::EntryControl, phi);
3058
      if (u == inner_iv_phi) {
3059
        iv_phi = phi;
3060
      }
3061
    }
3062
  }
3063

3064
  if (iv_phi != nullptr) {
3065
    // Now adjust the inner loop's exit condition
3066
    Node* limit = inner_cl->limit();
3067
    // If limit < init for stride > 0 (or limit > init for stride < 0),
3068
    // the loop body is run only once. Given limit - init (init - limit resp.)
3069
    // would be negative, the unsigned comparison below would cause
3070
    // the loop body to be run for LoopStripMiningIter.
3071
    Node* max = nullptr;
3072
    if (stride > 0) {
3073
      max = MaxNode::max_diff_with_zero(limit, iv_phi, TypeInt::INT, *igvn);
3074
    } else {
3075
      max = MaxNode::max_diff_with_zero(iv_phi, limit, TypeInt::INT, *igvn);
3076
    }
3077
    // sub is positive and can be larger than the max signed int
3078
    // value. Use an unsigned min.
3079
    Node* const_iters = igvn->intcon(scaled_iters);
3080
    Node* min = MaxNode::unsigned_min(max, const_iters, TypeInt::make(0, scaled_iters, Type::WidenMin), *igvn);
3081
    // min is the number of iterations for the next inner loop execution:
3082
    // unsigned_min(max(limit - iv_phi, 0), scaled_iters) if stride > 0
3083
    // unsigned_min(max(iv_phi - limit, 0), scaled_iters) if stride < 0
3084

3085
    Node* new_limit = nullptr;
3086
    if (stride > 0) {
3087
      new_limit = igvn->transform(new AddINode(min, iv_phi));
3088
    } else {
3089
      new_limit = igvn->transform(new SubINode(iv_phi, min));
3090
    }
3091
    Node* inner_cmp = inner_cle->cmp_node();
3092
    Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
3093
    Node* outer_bol = inner_bol;
3094
    // cmp node for inner loop may be shared
3095
    inner_cmp = inner_cmp->clone();
3096
    inner_cmp->set_req(2, new_limit);
3097
    inner_bol = inner_bol->clone();
3098
    inner_bol->set_req(1, igvn->transform(inner_cmp));
3099
    igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
3100
    // Set the outer loop's exit condition too
3101
    igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
3102
  } else {
3103
    assert(false, "should be able to adjust outer loop");
3104
    IfNode* outer_le = outer_loop_end();
3105
    Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
3106
    igvn->replace_node(outer_le, iff);
3107
    inner_cl->clear_strip_mined();
3108
  }
3109
}
3110

3111
void OuterStripMinedLoopNode::transform_to_counted_loop(PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
3112
  CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
3113
  CountedLoopEndNode* cle = inner_cl->loopexit();
3114
  Node* inner_test = cle->in(1);
3115
  IfNode* outer_le = outer_loop_end();
3116
  CountedLoopEndNode* inner_cle = inner_cl->loopexit();
3117
  Node* safepoint = outer_safepoint();
3118

3119
  fix_sunk_stores(inner_cle, inner_cl, igvn, iloop);
3120

3121
  // make counted loop exit test always fail
3122
  ConINode* zero = igvn->intcon(0);
3123
  if (iloop != nullptr) {
3124
    iloop->set_ctrl(zero, igvn->C->root());
3125
  }
3126
  igvn->replace_input_of(cle, 1, zero);
3127
  // replace outer loop end with CountedLoopEndNode with formers' CLE's exit test
3128
  Node* new_end = new CountedLoopEndNode(outer_le->in(0), inner_test, cle->_prob, cle->_fcnt);
3129
  register_control(new_end, inner_cl, outer_le->in(0), igvn, iloop);
3130
  if (iloop == nullptr) {
3131
    igvn->replace_node(outer_le, new_end);
3132
  } else {
3133
    iloop->lazy_replace(outer_le, new_end);
3134
  }
3135
  // the backedge of the inner loop must be rewired to the new loop end
3136
  Node* backedge = cle->proj_out(true);
3137
  igvn->replace_input_of(backedge, 0, new_end);
3138
  if (iloop != nullptr) {
3139
    iloop->set_idom(backedge, new_end, iloop->dom_depth(new_end) + 1);
3140
  }
3141
  // make the outer loop go away
3142
  igvn->replace_input_of(in(LoopBackControl), 0, igvn->C->top());
3143
  igvn->replace_input_of(this, LoopBackControl, igvn->C->top());
3144
  inner_cl->clear_strip_mined();
3145
  if (iloop != nullptr) {
3146
    Unique_Node_List wq;
3147
    wq.push(safepoint);
3148

3149
    IdealLoopTree* outer_loop_ilt = iloop->get_loop(this);
3150
    IdealLoopTree* loop = iloop->get_loop(inner_cl);
3151

3152
    for (uint i = 0; i < wq.size(); i++) {
3153
      Node* n = wq.at(i);
3154
      for (uint j = 0; j < n->req(); ++j) {
3155
        Node* in = n->in(j);
3156
        if (in == nullptr || in->is_CFG()) {
3157
          continue;
3158
        }
3159
        if (iloop->get_loop(iloop->get_ctrl(in)) != outer_loop_ilt) {
3160
          continue;
3161
        }
3162
        assert(!loop->_body.contains(in), "");
3163
        loop->_body.push(in);
3164
        wq.push(in);
3165
      }
3166
    }
3167
    iloop->set_loop(safepoint, loop);
3168
    loop->_body.push(safepoint);
3169
    iloop->set_loop(safepoint->in(0), loop);
3170
    loop->_body.push(safepoint->in(0));
3171
    outer_loop_ilt->_tail = igvn->C->top();
3172
  }
3173
}
3174

3175
void OuterStripMinedLoopNode::remove_outer_loop_and_safepoint(PhaseIterGVN* igvn) const {
3176
  CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
3177
  Node* outer_sfpt = outer_safepoint();
3178
  Node* outer_out = outer_loop_exit();
3179
  igvn->replace_node(outer_out, outer_sfpt->in(0));
3180
  igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
3181
  inner_cl->clear_strip_mined();
3182
}
3183

3184
Node* OuterStripMinedLoopNode::register_new_node(Node* node, LoopNode* ctrl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
3185
  if (iloop == nullptr) {
3186
    return igvn->transform(node);
3187
  }
3188
  iloop->register_new_node(node, ctrl);
3189
  return node;
3190
}
3191

3192
Node* OuterStripMinedLoopNode::register_control(Node* node, Node* loop, Node* idom, PhaseIterGVN* igvn,
3193
                                                PhaseIdealLoop* iloop) {
3194
  if (iloop == nullptr) {
3195
    return igvn->transform(node);
3196
  }
3197
  iloop->register_control(node, iloop->get_loop(loop), idom);
3198
  return node;
3199
}
3200

3201
const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
3202
  if (!in(0)) return Type::TOP;
3203
  if (phase->type(in(0)) == Type::TOP)
3204
    return Type::TOP;
3205

3206
  // Until expansion, the loop end condition is not set so this should not constant fold.
3207
  if (is_expanded(phase)) {
3208
    return IfNode::Value(phase);
3209
  }
3210

3211
  return TypeTuple::IFBOTH;
3212
}
3213

3214
bool OuterStripMinedLoopEndNode::is_expanded(PhaseGVN *phase) const {
3215
  // The outer strip mined loop head only has Phi uses after expansion
3216
  if (phase->is_IterGVN()) {
3217
    Node* backedge = proj_out_or_null(true);
3218
    if (backedge != nullptr) {
3219
      Node* head = backedge->unique_ctrl_out_or_null();
3220
      if (head != nullptr && head->is_OuterStripMinedLoop()) {
3221
        if (head->find_out_with(Op_Phi) != nullptr) {
3222
          return true;
3223
        }
3224
      }
3225
    }
3226
  }
3227
  return false;
3228
}
3229

3230
Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3231
  if (remove_dead_region(phase, can_reshape))  return this;
3232

3233
  return nullptr;
3234
}
3235

3236
//------------------------------filtered_type--------------------------------
3237
// Return a type based on condition control flow
3238
// A successful return will be a type that is restricted due
3239
// to a series of dominating if-tests, such as:
3240
//    if (i < 10) {
3241
//       if (i > 0) {
3242
//          here: "i" type is [1..10)
3243
//       }
3244
//    }
3245
// or a control flow merge
3246
//    if (i < 10) {
3247
//       do {
3248
//          phi( , ) -- at top of loop type is [min_int..10)
3249
//         i = ?
3250
//       } while ( i < 10)
3251
//
3252
const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
3253
  assert(n && n->bottom_type()->is_int(), "must be int");
3254
  const TypeInt* filtered_t = nullptr;
3255
  if (!n->is_Phi()) {
3256
    assert(n_ctrl != nullptr || n_ctrl == C->top(), "valid control");
3257
    filtered_t = filtered_type_from_dominators(n, n_ctrl);
3258

3259
  } else {
3260
    Node* phi    = n->as_Phi();
3261
    Node* region = phi->in(0);
3262
    assert(n_ctrl == nullptr || n_ctrl == region, "ctrl parameter must be region");
3263
    if (region && region != C->top()) {
3264
      for (uint i = 1; i < phi->req(); i++) {
3265
        Node* val   = phi->in(i);
3266
        Node* use_c = region->in(i);
3267
        const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
3268
        if (val_t != nullptr) {
3269
          if (filtered_t == nullptr) {
3270
            filtered_t = val_t;
3271
          } else {
3272
            filtered_t = filtered_t->meet(val_t)->is_int();
3273
          }
3274
        }
3275
      }
3276
    }
3277
  }
3278
  const TypeInt* n_t = _igvn.type(n)->is_int();
3279
  if (filtered_t != nullptr) {
3280
    n_t = n_t->join(filtered_t)->is_int();
3281
  }
3282
  return n_t;
3283
}
3284

3285

3286
//------------------------------filtered_type_from_dominators--------------------------------
3287
// Return a possibly more restrictive type for val based on condition control flow of dominators
3288
const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
3289
  if (val->is_Con()) {
3290
     return val->bottom_type()->is_int();
3291
  }
3292
  uint if_limit = 10; // Max number of dominating if's visited
3293
  const TypeInt* rtn_t = nullptr;
3294

3295
  if (use_ctrl && use_ctrl != C->top()) {
3296
    Node* val_ctrl = get_ctrl(val);
3297
    uint val_dom_depth = dom_depth(val_ctrl);
3298
    Node* pred = use_ctrl;
3299
    uint if_cnt = 0;
3300
    while (if_cnt < if_limit) {
3301
      if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
3302
        if_cnt++;
3303
        const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
3304
        if (if_t != nullptr) {
3305
          if (rtn_t == nullptr) {
3306
            rtn_t = if_t;
3307
          } else {
3308
            rtn_t = rtn_t->join(if_t)->is_int();
3309
          }
3310
        }
3311
      }
3312
      pred = idom(pred);
3313
      if (pred == nullptr || pred == C->top()) {
3314
        break;
3315
      }
3316
      // Stop if going beyond definition block of val
3317
      if (dom_depth(pred) < val_dom_depth) {
3318
        break;
3319
      }
3320
    }
3321
  }
3322
  return rtn_t;
3323
}
3324

3325

3326
//------------------------------dump_spec--------------------------------------
3327
// Dump special per-node info
3328
#ifndef PRODUCT
3329
void CountedLoopEndNode::dump_spec(outputStream *st) const {
3330
  if( in(TestValue) != nullptr && in(TestValue)->is_Bool() ) {
3331
    BoolTest bt( test_trip()); // Added this for g++.
3332

3333
    st->print("[");
3334
    bt.dump_on(st);
3335
    st->print("]");
3336
  }
3337
  st->print(" ");
3338
  IfNode::dump_spec(st);
3339
}
3340
#endif
3341

3342
//=============================================================================
3343
//------------------------------is_member--------------------------------------
3344
// Is 'l' a member of 'this'?
3345
bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
3346
  while( l->_nest > _nest ) l = l->_parent;
3347
  return l == this;
3348
}
3349

3350
//------------------------------set_nest---------------------------------------
3351
// Set loop tree nesting depth.  Accumulate _has_call bits.
3352
int IdealLoopTree::set_nest( uint depth ) {
3353
  assert(depth <= SHRT_MAX, "sanity");
3354
  _nest = depth;
3355
  int bits = _has_call;
3356
  if( _child ) bits |= _child->set_nest(depth+1);
3357
  if( bits ) _has_call = 1;
3358
  if( _next  ) bits |= _next ->set_nest(depth  );
3359
  return bits;
3360
}
3361

3362
//------------------------------split_fall_in----------------------------------
3363
// Split out multiple fall-in edges from the loop header.  Move them to a
3364
// private RegionNode before the loop.  This becomes the loop landing pad.
3365
void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
3366
  PhaseIterGVN &igvn = phase->_igvn;
3367
  uint i;
3368

3369
  // Make a new RegionNode to be the landing pad.
3370
  RegionNode* landing_pad = new RegionNode(fall_in_cnt + 1);
3371
  phase->set_loop(landing_pad,_parent);
3372
  // If _head was irreducible loop entry, landing_pad may now be too
3373
  landing_pad->set_loop_status(_head->as_Region()->loop_status());
3374
  // Gather all the fall-in control paths into the landing pad
3375
  uint icnt = fall_in_cnt;
3376
  uint oreq = _head->req();
3377
  for( i = oreq-1; i>0; i-- )
3378
    if( !phase->is_member( this, _head->in(i) ) )
3379
      landing_pad->set_req(icnt--,_head->in(i));
3380

3381
  // Peel off PhiNode edges as well
3382
  for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3383
    Node *oj = _head->fast_out(j);
3384
    if( oj->is_Phi() ) {
3385
      PhiNode* old_phi = oj->as_Phi();
3386
      assert( old_phi->region() == _head, "" );
3387
      igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
3388
      Node *p = PhiNode::make_blank(landing_pad, old_phi);
3389
      uint icnt = fall_in_cnt;
3390
      for( i = oreq-1; i>0; i-- ) {
3391
        if( !phase->is_member( this, _head->in(i) ) ) {
3392
          p->init_req(icnt--, old_phi->in(i));
3393
          // Go ahead and clean out old edges from old phi
3394
          old_phi->del_req(i);
3395
        }
3396
      }
3397
      // Search for CSE's here, because ZKM.jar does a lot of
3398
      // loop hackery and we need to be a little incremental
3399
      // with the CSE to avoid O(N^2) node blow-up.
3400
      Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
3401
      if( p2 ) {                // Found CSE
3402
        p->destruct(&igvn);     // Recover useless new node
3403
        p = p2;                 // Use old node
3404
      } else {
3405
        igvn.register_new_node_with_optimizer(p, old_phi);
3406
      }
3407
      // Make old Phi refer to new Phi.
3408
      old_phi->add_req(p);
3409
      // Check for the special case of making the old phi useless and
3410
      // disappear it.  In JavaGrande I have a case where this useless
3411
      // Phi is the loop limit and prevents recognizing a CountedLoop
3412
      // which in turn prevents removing an empty loop.
3413
      Node *id_old_phi = old_phi->Identity(&igvn);
3414
      if( id_old_phi != old_phi ) { // Found a simple identity?
3415
        // Note that I cannot call 'replace_node' here, because
3416
        // that will yank the edge from old_phi to the Region and
3417
        // I'm mid-iteration over the Region's uses.
3418
        for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
3419
          Node* use = old_phi->last_out(i);
3420
          igvn.rehash_node_delayed(use);
3421
          uint uses_found = 0;
3422
          for (uint j = 0; j < use->len(); j++) {
3423
            if (use->in(j) == old_phi) {
3424
              if (j < use->req()) use->set_req (j, id_old_phi);
3425
              else                use->set_prec(j, id_old_phi);
3426
              uses_found++;
3427
            }
3428
          }
3429
          i -= uses_found;    // we deleted 1 or more copies of this edge
3430
        }
3431
      }
3432
      igvn._worklist.push(old_phi);
3433
    }
3434
  }
3435
  // Finally clean out the fall-in edges from the RegionNode
3436
  for( i = oreq-1; i>0; i-- ) {
3437
    if( !phase->is_member( this, _head->in(i) ) ) {
3438
      _head->del_req(i);
3439
    }
3440
  }
3441
  igvn.rehash_node_delayed(_head);
3442
  // Transform landing pad
3443
  igvn.register_new_node_with_optimizer(landing_pad, _head);
3444
  // Insert landing pad into the header
3445
  _head->add_req(landing_pad);
3446
}
3447

3448
//------------------------------split_outer_loop-------------------------------
3449
// Split out the outermost loop from this shared header.
3450
void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
3451
  PhaseIterGVN &igvn = phase->_igvn;
3452

3453
  // Find index of outermost loop; it should also be my tail.
3454
  uint outer_idx = 1;
3455
  while( _head->in(outer_idx) != _tail ) outer_idx++;
3456

3457
  // Make a LoopNode for the outermost loop.
3458
  Node *ctl = _head->in(LoopNode::EntryControl);
3459
  Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
3460
  outer = igvn.register_new_node_with_optimizer(outer, _head);
3461
  phase->set_created_loop_node();
3462

3463
  // Outermost loop falls into '_head' loop
3464
  _head->set_req(LoopNode::EntryControl, outer);
3465
  _head->del_req(outer_idx);
3466
  // Split all the Phis up between '_head' loop and 'outer' loop.
3467
  for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3468
    Node *out = _head->fast_out(j);
3469
    if( out->is_Phi() ) {
3470
      PhiNode *old_phi = out->as_Phi();
3471
      assert( old_phi->region() == _head, "" );
3472
      Node *phi = PhiNode::make_blank(outer, old_phi);
3473
      phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
3474
      phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
3475
      phi = igvn.register_new_node_with_optimizer(phi, old_phi);
3476
      // Make old Phi point to new Phi on the fall-in path
3477
      igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
3478
      old_phi->del_req(outer_idx);
3479
    }
3480
  }
3481

3482
  // Use the new loop head instead of the old shared one
3483
  _head = outer;
3484
  phase->set_loop(_head, this);
3485
}
3486

3487
//------------------------------fix_parent-------------------------------------
3488
static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
3489
  loop->_parent = parent;
3490
  if( loop->_child ) fix_parent( loop->_child, loop   );
3491
  if( loop->_next  ) fix_parent( loop->_next , parent );
3492
}
3493

3494
//------------------------------estimate_path_freq-----------------------------
3495
static float estimate_path_freq( Node *n ) {
3496
  // Try to extract some path frequency info
3497
  IfNode *iff;
3498
  for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
3499
    uint nop = n->Opcode();
3500
    if( nop == Op_SafePoint ) {   // Skip any safepoint
3501
      n = n->in(0);
3502
      continue;
3503
    }
3504
    if( nop == Op_CatchProj ) {   // Get count from a prior call
3505
      // Assume call does not always throw exceptions: means the call-site
3506
      // count is also the frequency of the fall-through path.
3507
      assert( n->is_CatchProj(), "" );
3508
      if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
3509
        return 0.0f;            // Assume call exception path is rare
3510
      Node *call = n->in(0)->in(0)->in(0);
3511
      assert( call->is_Call(), "expect a call here" );
3512
      const JVMState *jvms = ((CallNode*)call)->jvms();
3513
      ciMethodData* methodData = jvms->method()->method_data();
3514
      if (!methodData->is_mature())  return 0.0f; // No call-site data
3515
      ciProfileData* data = methodData->bci_to_data(jvms->bci());
3516
      if ((data == nullptr) || !data->is_CounterData()) {
3517
        // no call profile available, try call's control input
3518
        n = n->in(0);
3519
        continue;
3520
      }
3521
      return data->as_CounterData()->count()/FreqCountInvocations;
3522
    }
3523
    // See if there's a gating IF test
3524
    Node *n_c = n->in(0);
3525
    if( !n_c->is_If() ) break;       // No estimate available
3526
    iff = n_c->as_If();
3527
    if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
3528
      // Compute how much count comes on this path
3529
      return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
3530
    // Have no count info.  Skip dull uncommon-trap like branches.
3531
    if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
3532
        (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
3533
      break;
3534
    // Skip through never-taken branch; look for a real loop exit.
3535
    n = iff->in(0);
3536
  }
3537
  return 0.0f;                  // No estimate available
3538
}
3539

3540
//------------------------------merge_many_backedges---------------------------
3541
// Merge all the backedges from the shared header into a private Region.
3542
// Feed that region as the one backedge to this loop.
3543
void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
3544
  uint i;
3545

3546
  // Scan for the top 2 hottest backedges
3547
  float hotcnt = 0.0f;
3548
  float warmcnt = 0.0f;
3549
  uint hot_idx = 0;
3550
  // Loop starts at 2 because slot 1 is the fall-in path
3551
  for( i = 2; i < _head->req(); i++ ) {
3552
    float cnt = estimate_path_freq(_head->in(i));
3553
    if( cnt > hotcnt ) {       // Grab hottest path
3554
      warmcnt = hotcnt;
3555
      hotcnt = cnt;
3556
      hot_idx = i;
3557
    } else if( cnt > warmcnt ) { // And 2nd hottest path
3558
      warmcnt = cnt;
3559
    }
3560
  }
3561

3562
  // See if the hottest backedge is worthy of being an inner loop
3563
  // by being much hotter than the next hottest backedge.
3564
  if( hotcnt <= 0.0001 ||
3565
      hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
3566

3567
  // Peel out the backedges into a private merge point; peel
3568
  // them all except optionally hot_idx.
3569
  PhaseIterGVN &igvn = phase->_igvn;
3570

3571
  Node *hot_tail = nullptr;
3572
  // Make a Region for the merge point
3573
  Node *r = new RegionNode(1);
3574
  for( i = 2; i < _head->req(); i++ ) {
3575
    if( i != hot_idx )
3576
      r->add_req( _head->in(i) );
3577
    else hot_tail = _head->in(i);
3578
  }
3579
  igvn.register_new_node_with_optimizer(r, _head);
3580
  // Plug region into end of loop _head, followed by hot_tail
3581
  while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
3582
  igvn.replace_input_of(_head, 2, r);
3583
  if( hot_idx ) _head->add_req(hot_tail);
3584

3585
  // Split all the Phis up between '_head' loop and the Region 'r'
3586
  for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3587
    Node *out = _head->fast_out(j);
3588
    if( out->is_Phi() ) {
3589
      PhiNode* n = out->as_Phi();
3590
      igvn.hash_delete(n);      // Delete from hash before hacking edges
3591
      Node *hot_phi = nullptr;
3592
      Node *phi = new PhiNode(r, n->type(), n->adr_type());
3593
      // Check all inputs for the ones to peel out
3594
      uint j = 1;
3595
      for( uint i = 2; i < n->req(); i++ ) {
3596
        if( i != hot_idx )
3597
          phi->set_req( j++, n->in(i) );
3598
        else hot_phi = n->in(i);
3599
      }
3600
      // Register the phi but do not transform until whole place transforms
3601
      igvn.register_new_node_with_optimizer(phi, n);
3602
      // Add the merge phi to the old Phi
3603
      while( n->req() > 3 ) n->del_req( n->req()-1 );
3604
      igvn.replace_input_of(n, 2, phi);
3605
      if( hot_idx ) n->add_req(hot_phi);
3606
    }
3607
  }
3608

3609

3610
  // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
3611
  // of self loop tree.  Turn self into a loop headed by _head and with
3612
  // tail being the new merge point.
3613
  IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
3614
  phase->set_loop(_tail,ilt);   // Adjust tail
3615
  _tail = r;                    // Self's tail is new merge point
3616
  phase->set_loop(r,this);
3617
  ilt->_child = _child;         // New guy has my children
3618
  _child = ilt;                 // Self has new guy as only child
3619
  ilt->_parent = this;          // new guy has self for parent
3620
  ilt->_nest = _nest;           // Same nesting depth (for now)
3621

3622
  // Starting with 'ilt', look for child loop trees using the same shared
3623
  // header.  Flatten these out; they will no longer be loops in the end.
3624
  IdealLoopTree **pilt = &_child;
3625
  while( ilt ) {
3626
    if( ilt->_head == _head ) {
3627
      uint i;
3628
      for( i = 2; i < _head->req(); i++ )
3629
        if( _head->in(i) == ilt->_tail )
3630
          break;                // Still a loop
3631
      if( i == _head->req() ) { // No longer a loop
3632
        // Flatten ilt.  Hang ilt's "_next" list from the end of
3633
        // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
3634
        IdealLoopTree **cp = &ilt->_child;
3635
        while( *cp ) cp = &(*cp)->_next;   // Find end of child list
3636
        *cp = ilt->_next;       // Hang next list at end of child list
3637
        *pilt = ilt->_child;    // Move child up to replace ilt
3638
        ilt->_head = nullptr;   // Flag as a loop UNIONED into parent
3639
        ilt = ilt->_child;      // Repeat using new ilt
3640
        continue;               // do not advance over ilt->_child
3641
      }
3642
      assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
3643
      phase->set_loop(_head,ilt);
3644
    }
3645
    pilt = &ilt->_child;        // Advance to next
3646
    ilt = *pilt;
3647
  }
3648

3649
  if( _child ) fix_parent( _child, this );
3650
}
3651

3652
//------------------------------beautify_loops---------------------------------
3653
// Split shared headers and insert loop landing pads.
3654
// Insert a LoopNode to replace the RegionNode.
3655
// Return TRUE if loop tree is structurally changed.
3656
bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
3657
  bool result = false;
3658
  // Cache parts in locals for easy
3659
  PhaseIterGVN &igvn = phase->_igvn;
3660

3661
  igvn.hash_delete(_head);      // Yank from hash before hacking edges
3662

3663
  // Check for multiple fall-in paths.  Peel off a landing pad if need be.
3664
  int fall_in_cnt = 0;
3665
  for( uint i = 1; i < _head->req(); i++ )
3666
    if( !phase->is_member( this, _head->in(i) ) )
3667
      fall_in_cnt++;
3668
  assert( fall_in_cnt, "at least 1 fall-in path" );
3669
  if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
3670
    split_fall_in( phase, fall_in_cnt );
3671

3672
  // Swap inputs to the _head and all Phis to move the fall-in edge to
3673
  // the left.
3674
  fall_in_cnt = 1;
3675
  while( phase->is_member( this, _head->in(fall_in_cnt) ) )
3676
    fall_in_cnt++;
3677
  if( fall_in_cnt > 1 ) {
3678
    // Since I am just swapping inputs I do not need to update def-use info
3679
    Node *tmp = _head->in(1);
3680
    igvn.rehash_node_delayed(_head);
3681
    _head->set_req( 1, _head->in(fall_in_cnt) );
3682
    _head->set_req( fall_in_cnt, tmp );
3683
    // Swap also all Phis
3684
    for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
3685
      Node* phi = _head->fast_out(i);
3686
      if( phi->is_Phi() ) {
3687
        igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
3688
        tmp = phi->in(1);
3689
        phi->set_req( 1, phi->in(fall_in_cnt) );
3690
        phi->set_req( fall_in_cnt, tmp );
3691
      }
3692
    }
3693
  }
3694
  assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
3695
  assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
3696

3697
  // If I am a shared header (multiple backedges), peel off the many
3698
  // backedges into a private merge point and use the merge point as
3699
  // the one true backedge.
3700
  if (_head->req() > 3) {
3701
    // Merge the many backedges into a single backedge but leave
3702
    // the hottest backedge as separate edge for the following peel.
3703
    if (!_irreducible) {
3704
      merge_many_backedges( phase );
3705
    }
3706

3707
    // When recursively beautify my children, split_fall_in can change
3708
    // loop tree structure when I am an irreducible loop. Then the head
3709
    // of my children has a req() not bigger than 3. Here we need to set
3710
    // result to true to catch that case in order to tell the caller to
3711
    // rebuild loop tree. See issue JDK-8244407 for details.
3712
    result = true;
3713
  }
3714

3715
  // If I have one hot backedge, peel off myself loop.
3716
  // I better be the outermost loop.
3717
  if (_head->req() > 3 && !_irreducible) {
3718
    split_outer_loop( phase );
3719
    result = true;
3720

3721
  } else if (!_head->is_Loop() && !_irreducible) {
3722
    // Make a new LoopNode to replace the old loop head
3723
    Node *l = new LoopNode( _head->in(1), _head->in(2) );
3724
    l = igvn.register_new_node_with_optimizer(l, _head);
3725
    phase->set_created_loop_node();
3726
    // Go ahead and replace _head
3727
    phase->_igvn.replace_node( _head, l );
3728
    _head = l;
3729
    phase->set_loop(_head, this);
3730
  }
3731

3732
  // Now recursively beautify nested loops
3733
  if( _child ) result |= _child->beautify_loops( phase );
3734
  if( _next  ) result |= _next ->beautify_loops( phase );
3735
  return result;
3736
}
3737

3738
//------------------------------allpaths_check_safepts----------------------------
3739
// Allpaths backwards scan. Starting at the head, traversing all backedges, and the body. Terminating each path at first
3740
// safepoint encountered.  Helper for check_safepts.
3741
void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
3742
  assert(stack.size() == 0, "empty stack");
3743
  stack.push(_head);
3744
  visited.clear();
3745
  visited.set(_head->_idx);
3746
  while (stack.size() > 0) {
3747
    Node* n = stack.pop();
3748
    if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
3749
      // Terminate this path
3750
    } else if (n->Opcode() == Op_SafePoint) {
3751
      if (_phase->get_loop(n) != this) {
3752
        if (_required_safept == nullptr) _required_safept = new Node_List();
3753
        // save the first we run into on that path: closest to the tail if the head has a single backedge
3754
        _required_safept->push(n);
3755
      }
3756
      // Terminate this path
3757
    } else {
3758
      uint start = n->is_Region() ? 1 : 0;
3759
      uint end   = n->is_Region() && (!n->is_Loop() || n == _head) ? n->req() : start + 1;
3760
      for (uint i = start; i < end; i++) {
3761
        Node* in = n->in(i);
3762
        assert(in->is_CFG(), "must be");
3763
        if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
3764
          stack.push(in);
3765
        }
3766
      }
3767
    }
3768
  }
3769
}
3770

3771
//------------------------------check_safepts----------------------------
3772
// Given dominators, try to find loops with calls that must always be
3773
// executed (call dominates loop tail).  These loops do not need non-call
3774
// safepoints (ncsfpt).
3775
//
3776
// A complication is that a safepoint in a inner loop may be needed
3777
// by an outer loop. In the following, the inner loop sees it has a
3778
// call (block 3) on every path from the head (block 2) to the
3779
// backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
3780
// in block 2, _but_ this leaves the outer loop without a safepoint.
3781
//
3782
//          entry  0
3783
//                 |
3784
//                 v
3785
// outer 1,2    +->1
3786
//              |  |
3787
//              |  v
3788
//              |  2<---+  ncsfpt in 2
3789
//              |_/|\   |
3790
//                 | v  |
3791
// inner 2,3      /  3  |  call in 3
3792
//               /   |  |
3793
//              v    +--+
3794
//        exit  4
3795
//
3796
//
3797
// This method creates a list (_required_safept) of ncsfpt nodes that must
3798
// be protected is created for each loop. When a ncsfpt maybe deleted, it
3799
// is first looked for in the lists for the outer loops of the current loop.
3800
//
3801
// The insights into the problem:
3802
//  A) counted loops are okay
3803
//  B) innermost loops are okay (only an inner loop can delete
3804
//     a ncsfpt needed by an outer loop)
3805
//  C) a loop is immune from an inner loop deleting a safepoint
3806
//     if the loop has a call on the idom-path
3807
//  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
3808
//     idom-path that is not in a nested loop
3809
//  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
3810
//     loop needs to be prevented from deletion by an inner loop
3811
//
3812
// There are two analyses:
3813
//  1) The first, and cheaper one, scans the loop body from
3814
//     tail to head following the idom (immediate dominator)
3815
//     chain, looking for the cases (C,D,E) above.
3816
//     Since inner loops are scanned before outer loops, there is summary
3817
//     information about inner loops.  Inner loops can be skipped over
3818
//     when the tail of an inner loop is encountered.
3819
//
3820
//  2) The second, invoked if the first fails to find a call or ncsfpt on
3821
//     the idom path (which is rare), scans all predecessor control paths
3822
//     from the tail to the head, terminating a path when a call or sfpt
3823
//     is encountered, to find the ncsfpt's that are closest to the tail.
3824
//
3825
void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
3826
  // Bottom up traversal
3827
  IdealLoopTree* ch = _child;
3828
  if (_child) _child->check_safepts(visited, stack);
3829
  if (_next)  _next ->check_safepts(visited, stack);
3830

3831
  if (!_head->is_CountedLoop() && !_has_sfpt && _parent != nullptr) {
3832
    bool  has_call         = false;    // call on dom-path
3833
    bool  has_local_ncsfpt = false;    // ncsfpt on dom-path at this loop depth
3834
    Node* nonlocal_ncsfpt  = nullptr;  // ncsfpt on dom-path at a deeper depth
3835
    if (!_irreducible) {
3836
      // Scan the dom-path nodes from tail to head
3837
      for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
3838
        if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
3839
          has_call = true;
3840
          _has_sfpt = 1;          // Then no need for a safept!
3841
          break;
3842
        } else if (n->Opcode() == Op_SafePoint) {
3843
          if (_phase->get_loop(n) == this) {
3844
            has_local_ncsfpt = true;
3845
            break;
3846
          }
3847
          if (nonlocal_ncsfpt == nullptr) {
3848
            nonlocal_ncsfpt = n; // save the one closest to the tail
3849
          }
3850
        } else {
3851
          IdealLoopTree* nlpt = _phase->get_loop(n);
3852
          if (this != nlpt) {
3853
            // If at an inner loop tail, see if the inner loop has already
3854
            // recorded seeing a call on the dom-path (and stop.)  If not,
3855
            // jump to the head of the inner loop.
3856
            assert(is_member(nlpt), "nested loop");
3857
            Node* tail = nlpt->_tail;
3858
            if (tail->in(0)->is_If()) tail = tail->in(0);
3859
            if (n == tail) {
3860
              // If inner loop has call on dom-path, so does outer loop
3861
              if (nlpt->_has_sfpt) {
3862
                has_call = true;
3863
                _has_sfpt = 1;
3864
                break;
3865
              }
3866
              // Skip to head of inner loop
3867
              assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
3868
              n = nlpt->_head;
3869
              if (_head == n) {
3870
                // this and nlpt (inner loop) have the same loop head. This should not happen because
3871
                // during beautify_loops we call merge_many_backedges. However, infinite loops may not
3872
                // have been attached to the loop-tree during build_loop_tree before beautify_loops,
3873
                // but then attached in the build_loop_tree afterwards, and so still have unmerged
3874
                // backedges. Check if we are indeed in an infinite subgraph, and terminate the scan,
3875
                // since we have reached the loop head of this.
3876
                assert(_head->as_Region()->is_in_infinite_subgraph(),
3877
                       "only expect unmerged backedges in infinite loops");
3878
                break;
3879
              }
3880
            }
3881
          }
3882
        }
3883
      }
3884
    }
3885
    // Record safept's that this loop needs preserved when an
3886
    // inner loop attempts to delete it's safepoints.
3887
    if (_child != nullptr && !has_call && !has_local_ncsfpt) {
3888
      if (nonlocal_ncsfpt != nullptr) {
3889
        if (_required_safept == nullptr) _required_safept = new Node_List();
3890
        _required_safept->push(nonlocal_ncsfpt);
3891
      } else {
3892
        // Failed to find a suitable safept on the dom-path.  Now use
3893
        // an all paths walk from tail to head, looking for safepoints to preserve.
3894
        allpaths_check_safepts(visited, stack);
3895
      }
3896
    }
3897
  }
3898
}
3899

3900
//---------------------------is_deleteable_safept----------------------------
3901
// Is safept not required by an outer loop?
3902
bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
3903
  assert(sfpt->Opcode() == Op_SafePoint, "");
3904
  IdealLoopTree* lp = get_loop(sfpt)->_parent;
3905
  while (lp != nullptr) {
3906
    Node_List* sfpts = lp->_required_safept;
3907
    if (sfpts != nullptr) {
3908
      for (uint i = 0; i < sfpts->size(); i++) {
3909
        if (sfpt == sfpts->at(i))
3910
          return false;
3911
      }
3912
    }
3913
    lp = lp->_parent;
3914
  }
3915
  return true;
3916
}
3917

3918
//---------------------------replace_parallel_iv-------------------------------
3919
// Replace parallel induction variable (parallel to trip counter)
3920
void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
3921
  assert(loop->_head->is_CountedLoop(), "");
3922
  CountedLoopNode *cl = loop->_head->as_CountedLoop();
3923
  if (!cl->is_valid_counted_loop(T_INT)) {
3924
    return;         // skip malformed counted loop
3925
  }
3926
  Node *incr = cl->incr();
3927
  if (incr == nullptr) {
3928
    return;         // Dead loop?
3929
  }
3930
  Node *init = cl->init_trip();
3931
  Node *phi  = cl->phi();
3932
  int stride_con = cl->stride_con();
3933

3934
  // Visit all children, looking for Phis
3935
  for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
3936
    Node *out = cl->out(i);
3937
    // Look for other phis (secondary IVs). Skip dead ones
3938
    if (!out->is_Phi() || out == phi || !has_node(out)) {
3939
      continue;
3940
    }
3941

3942
    PhiNode* phi2 = out->as_Phi();
3943
    Node* incr2 = phi2->in(LoopNode::LoopBackControl);
3944
    // Look for induction variables of the form:  X += constant
3945
    if (phi2->region() != loop->_head ||
3946
        incr2->req() != 3 ||
3947
        incr2->in(1)->uncast() != phi2 ||
3948
        incr2 == incr ||
3949
        incr2->Opcode() != Op_AddI ||
3950
        !incr2->in(2)->is_Con()) {
3951
      continue;
3952
    }
3953

3954
    if (incr2->in(1)->is_ConstraintCast() &&
3955
        !(incr2->in(1)->in(0)->is_IfProj() && incr2->in(1)->in(0)->in(0)->is_RangeCheck())) {
3956
      // Skip AddI->CastII->Phi case if CastII is not controlled by local RangeCheck
3957
      continue;
3958
    }
3959
    // Check for parallel induction variable (parallel to trip counter)
3960
    // via an affine function.  In particular, count-down loops with
3961
    // count-up array indices are common. We only RCE references off
3962
    // the trip-counter, so we need to convert all these to trip-counter
3963
    // expressions.
3964
    Node* init2 = phi2->in(LoopNode::EntryControl);
3965
    int stride_con2 = incr2->in(2)->get_int();
3966

3967
    // The ratio of the two strides cannot be represented as an int
3968
    // if stride_con2 is min_int and stride_con is -1.
3969
    if (stride_con2 == min_jint && stride_con == -1) {
3970
      continue;
3971
    }
3972

3973
    // The general case here gets a little tricky.  We want to find the
3974
    // GCD of all possible parallel IV's and make a new IV using this
3975
    // GCD for the loop.  Then all possible IVs are simple multiples of
3976
    // the GCD.  In practice, this will cover very few extra loops.
3977
    // Instead we require 'stride_con2' to be a multiple of 'stride_con',
3978
    // where +/-1 is the common case, but other integer multiples are
3979
    // also easy to handle.
3980
    int ratio_con = stride_con2/stride_con;
3981

3982
    if ((ratio_con * stride_con) == stride_con2) { // Check for exact
3983
#ifndef PRODUCT
3984
      if (TraceLoopOpts) {
3985
        tty->print("Parallel IV: %d ", phi2->_idx);
3986
        loop->dump_head();
3987
      }
3988
#endif
3989
      // Convert to using the trip counter.  The parallel induction
3990
      // variable differs from the trip counter by a loop-invariant
3991
      // amount, the difference between their respective initial values.
3992
      // It is scaled by the 'ratio_con'.
3993
      Node* ratio = _igvn.intcon(ratio_con);
3994
      set_ctrl(ratio, C->root());
3995
      Node* ratio_init = new MulINode(init, ratio);
3996
      _igvn.register_new_node_with_optimizer(ratio_init, init);
3997
      set_early_ctrl(ratio_init, false);
3998
      Node* diff = new SubINode(init2, ratio_init);
3999
      _igvn.register_new_node_with_optimizer(diff, init2);
4000
      set_early_ctrl(diff, false);
4001
      Node* ratio_idx = new MulINode(phi, ratio);
4002
      _igvn.register_new_node_with_optimizer(ratio_idx, phi);
4003
      set_ctrl(ratio_idx, cl);
4004
      Node* add = new AddINode(ratio_idx, diff);
4005
      _igvn.register_new_node_with_optimizer(add);
4006
      set_ctrl(add, cl);
4007
      _igvn.replace_node( phi2, add );
4008
      // Sometimes an induction variable is unused
4009
      if (add->outcnt() == 0) {
4010
        _igvn.remove_dead_node(add);
4011
      }
4012
      --i; // deleted this phi; rescan starting with next position
4013
      continue;
4014
    }
4015
  }
4016
}
4017

4018
void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
4019
  Node* keep = nullptr;
4020
  if (keep_one) {
4021
    // Look for a safepoint on the idom-path.
4022
    for (Node* i = tail(); i != _head; i = phase->idom(i)) {
4023
      if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
4024
        keep = i;
4025
        break; // Found one
4026
      }
4027
    }
4028
  }
4029

4030
  // Don't remove any safepoints if it is requested to keep a single safepoint and
4031
  // no safepoint was found on idom-path. It is not safe to remove any safepoint
4032
  // in this case since there's no safepoint dominating all paths in the loop body.
4033
  bool prune = !keep_one || keep != nullptr;
4034

4035
  // Delete other safepoints in this loop.
4036
  Node_List* sfpts = _safepts;
4037
  if (prune && sfpts != nullptr) {
4038
    assert(keep == nullptr || keep->Opcode() == Op_SafePoint, "not safepoint");
4039
    for (uint i = 0; i < sfpts->size(); i++) {
4040
      Node* n = sfpts->at(i);
4041
      assert(phase->get_loop(n) == this, "");
4042
      if (n != keep && phase->is_deleteable_safept(n)) {
4043
        phase->lazy_replace(n, n->in(TypeFunc::Control));
4044
      }
4045
    }
4046
  }
4047
}
4048

4049
//------------------------------counted_loop-----------------------------------
4050
// Convert to counted loops where possible
4051
void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
4052

4053
  // For grins, set the inner-loop flag here
4054
  if (!_child) {
4055
    if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
4056
  }
4057

4058
  IdealLoopTree* loop = this;
4059
  if (_head->is_CountedLoop() ||
4060
      phase->is_counted_loop(_head, loop, T_INT)) {
4061

4062
    if (LoopStripMiningIter == 0 || _head->as_CountedLoop()->is_strip_mined()) {
4063
      // Indicate we do not need a safepoint here
4064
      _has_sfpt = 1;
4065
    }
4066

4067
    // Remove safepoints
4068
    bool keep_one_sfpt = !(_has_call || _has_sfpt);
4069
    remove_safepoints(phase, keep_one_sfpt);
4070

4071
    // Look for induction variables
4072
    phase->replace_parallel_iv(this);
4073
  } else if (_head->is_LongCountedLoop() ||
4074
             phase->is_counted_loop(_head, loop, T_LONG)) {
4075
    remove_safepoints(phase, true);
4076
  } else {
4077
    assert(!_head->is_Loop() || !_head->as_Loop()->is_loop_nest_inner_loop(), "transformation to counted loop should not fail");
4078
    if (_parent != nullptr && !_irreducible) {
4079
      // Not a counted loop. Keep one safepoint.
4080
      bool keep_one_sfpt = true;
4081
      remove_safepoints(phase, keep_one_sfpt);
4082
    }
4083
  }
4084

4085
  // Recursively
4086
  assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
4087
  assert(loop->_child != this || (loop->_child->_child == nullptr && loop->_child->_next == nullptr), "would miss some loops");
4088
  if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
4089
  if (loop->_next)  loop->_next ->counted_loop(phase);
4090
}
4091

4092

4093
// The Estimated Loop Clone Size:
4094
//   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
4095
// where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
4096
// respectively, used to ensure that the node usage estimates made are on the
4097
// safe side, for the most part. The FanOutTerm is an attempt to estimate the
4098
// possible additional/excessive nodes generated due to data and control flow
4099
// merging, for edges reaching outside the loop.
4100
uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
4101

4102
  precond(0 < factor && factor < 16);
4103

4104
  uint const bc = 13;
4105
  uint const cc = 17;
4106
  uint const sz = _body.size() + (_body.size() + 7) / 2;
4107
  uint estimate = factor * (sz + bc) + cc;
4108

4109
  assert((estimate - cc) / factor == sz + bc, "overflow");
4110

4111
  return estimate + est_loop_flow_merge_sz();
4112
}
4113

4114
// The Estimated Loop (full-) Unroll Size:
4115
//   UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
4116
// where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
4117
// node usage estimates made are on the safe side, for the most part. This is
4118
// a "light" version of the loop clone size calculation (above), based on the
4119
// assumption that most of the loop-construct overhead will be unraveled when
4120
// (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
4121
// including an overflow check and returning UINT_MAX in case of an overflow.
4122
uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
4123

4124
  precond(factor > 0);
4125

4126
  // Take into account that after unroll conjoined heads and tails will fold.
4127
  uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
4128
  uint const cc = 7;
4129
  uint const sz = b0 + (b0 + 15) / 16;
4130
  uint estimate = factor * sz + cc;
4131

4132
  if ((estimate - cc) / factor != sz) {
4133
    return UINT_MAX;
4134
  }
4135

4136
  return estimate + est_loop_flow_merge_sz();
4137
}
4138

4139
// Estimate the growth effect (in nodes) of merging control and data flow when
4140
// cloning a loop body, based on the amount of  control and data flow reaching
4141
// outside of the (current) loop body.
4142
uint IdealLoopTree::est_loop_flow_merge_sz() const {
4143

4144
  uint ctrl_edge_out_cnt = 0;
4145
  uint data_edge_out_cnt = 0;
4146

4147
  for (uint i = 0; i < _body.size(); i++) {
4148
    Node* node = _body.at(i);
4149
    uint outcnt = node->outcnt();
4150

4151
    for (uint k = 0; k < outcnt; k++) {
4152
      Node* out = node->raw_out(k);
4153
      if (out == nullptr) continue;
4154
      if (out->is_CFG()) {
4155
        if (!is_member(_phase->get_loop(out))) {
4156
          ctrl_edge_out_cnt++;
4157
        }
4158
      } else if (_phase->has_ctrl(out)) {
4159
        Node* ctrl = _phase->get_ctrl(out);
4160
        assert(ctrl != nullptr, "must be");
4161
        assert(ctrl->is_CFG(), "must be");
4162
        if (!is_member(_phase->get_loop(ctrl))) {
4163
          data_edge_out_cnt++;
4164
        }
4165
      }
4166
    }
4167
  }
4168
  // Use data and control count (x2.0) in estimate iff both are > 0. This is
4169
  // a rather pessimistic estimate for the most part, in particular for some
4170
  // complex loops, but still not enough to capture all loops.
4171
  if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
4172
    return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
4173
  }
4174
  return 0;
4175
}
4176

4177
#ifndef PRODUCT
4178
//------------------------------dump_head--------------------------------------
4179
// Dump 1 liner for loop header info
4180
void IdealLoopTree::dump_head() {
4181
  tty->sp(2 * _nest);
4182
  tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
4183
  if (_irreducible) tty->print(" IRREDUCIBLE");
4184
  Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl)
4185
                                 : _head->in(LoopNode::EntryControl);
4186
  const Predicates predicates(entry);
4187
  if (predicates.loop_limit_check_predicate_block()->is_non_empty()) {
4188
    tty->print(" limit_check");
4189
  }
4190
  if (UseProfiledLoopPredicate && predicates.profiled_loop_predicate_block()->is_non_empty()) {
4191
    tty->print(" profile_predicated");
4192
  }
4193
  if (UseLoopPredicate && predicates.loop_predicate_block()->is_non_empty()) {
4194
    tty->print(" predicated");
4195
  }
4196
  if (_head->is_CountedLoop()) {
4197
    CountedLoopNode *cl = _head->as_CountedLoop();
4198
    tty->print(" counted");
4199

4200
    Node* init_n = cl->init_trip();
4201
    if (init_n  != nullptr &&  init_n->is_Con())
4202
      tty->print(" [%d,", cl->init_trip()->get_int());
4203
    else
4204
      tty->print(" [int,");
4205
    Node* limit_n = cl->limit();
4206
    if (limit_n  != nullptr &&  limit_n->is_Con())
4207
      tty->print("%d),", cl->limit()->get_int());
4208
    else
4209
      tty->print("int),");
4210
    int stride_con  = cl->stride_con();
4211
    if (stride_con > 0) tty->print("+");
4212
    tty->print("%d", stride_con);
4213

4214
    tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
4215

4216
    if (cl->is_pre_loop ()) tty->print(" pre" );
4217
    if (cl->is_main_loop()) tty->print(" main");
4218
    if (cl->is_post_loop()) tty->print(" post");
4219
    if (cl->is_vectorized_loop()) tty->print(" vector");
4220
    if (range_checks_present()) tty->print(" rc ");
4221
  }
4222
  if (_has_call) tty->print(" has_call");
4223
  if (_has_sfpt) tty->print(" has_sfpt");
4224
  if (_rce_candidate) tty->print(" rce");
4225
  if (_safepts != nullptr && _safepts->size() > 0) {
4226
    tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
4227
  }
4228
  if (_required_safept != nullptr && _required_safept->size() > 0) {
4229
    tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
4230
  }
4231
  if (Verbose) {
4232
    tty->print(" body={"); _body.dump_simple(); tty->print(" }");
4233
  }
4234
  if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
4235
    tty->print(" strip_mined");
4236
  }
4237
  tty->cr();
4238
}
4239

4240
//------------------------------dump-------------------------------------------
4241
// Dump loops by loop tree
4242
void IdealLoopTree::dump() {
4243
  dump_head();
4244
  if (_child) _child->dump();
4245
  if (_next)  _next ->dump();
4246
}
4247

4248
#endif
4249

4250
static void log_loop_tree_helper(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
4251
  if (loop == root) {
4252
    if (loop->_child != nullptr) {
4253
      log->begin_head("loop_tree");
4254
      log->end_head();
4255
      log_loop_tree_helper(root, loop->_child, log);
4256
      log->tail("loop_tree");
4257
      assert(loop->_next == nullptr, "what?");
4258
    }
4259
  } else if (loop != nullptr) {
4260
    Node* head = loop->_head;
4261
    log->begin_head("loop");
4262
    log->print(" idx='%d' ", head->_idx);
4263
    if (loop->_irreducible) log->print("irreducible='1' ");
4264
    if (head->is_Loop()) {
4265
      if (head->as_Loop()->is_inner_loop())        log->print("inner_loop='1' ");
4266
      if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
4267
    } else if (head->is_CountedLoop()) {
4268
      CountedLoopNode* cl = head->as_CountedLoop();
4269
      if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
4270
      if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
4271
      if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
4272
    }
4273
    log->end_head();
4274
    log_loop_tree_helper(root, loop->_child, log);
4275
    log->tail("loop");
4276
    log_loop_tree_helper(root, loop->_next, log);
4277
  }
4278
}
4279

4280
void PhaseIdealLoop::log_loop_tree() {
4281
  if (C->log() != nullptr) {
4282
    log_loop_tree_helper(_ltree_root, _ltree_root, C->log());
4283
  }
4284
}
4285

4286
// Eliminate all Parse and Template Assertion Predicates that are not associated with a loop anymore. The eliminated
4287
// predicates will be removed during the next round of IGVN.
4288
void PhaseIdealLoop::eliminate_useless_predicates() {
4289
  if (C->parse_predicate_count() == 0 && C->template_assertion_predicate_count() == 0) {
4290
    return; // No predicates left.
4291
  }
4292

4293
  eliminate_useless_parse_predicates();
4294
  eliminate_useless_template_assertion_predicates();
4295
}
4296

4297
// Eliminate all Parse Predicates that do not belong to a loop anymore by marking them useless. These will be removed
4298
// during the next round of IGVN.
4299
void PhaseIdealLoop::eliminate_useless_parse_predicates() {
4300
  mark_all_parse_predicates_useless();
4301
  if (C->has_loops()) {
4302
    mark_loop_associated_parse_predicates_useful();
4303
  }
4304
  add_useless_parse_predicates_to_igvn_worklist();
4305
}
4306

4307
void PhaseIdealLoop::mark_all_parse_predicates_useless() const {
4308
  for (int i = 0; i < C->parse_predicate_count(); i++) {
4309
    C->parse_predicate(i)->mark_useless();
4310
  }
4311
}
4312

4313
void PhaseIdealLoop::mark_loop_associated_parse_predicates_useful() {
4314
  for (LoopTreeIterator iterator(_ltree_root); !iterator.done(); iterator.next()) {
4315
    IdealLoopTree* loop = iterator.current();
4316
    if (loop->can_apply_loop_predication()) {
4317
      mark_useful_parse_predicates_for_loop(loop);
4318
    }
4319
  }
4320
}
4321

4322
void PhaseIdealLoop::mark_useful_parse_predicates_for_loop(IdealLoopTree* loop) {
4323
  Node* entry = loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
4324
  const Predicates predicates(entry);
4325
  ParsePredicateIterator iterator(predicates);
4326
  while (iterator.has_next()) {
4327
    iterator.next()->mark_useful();
4328
  }
4329
}
4330

4331
void PhaseIdealLoop::add_useless_parse_predicates_to_igvn_worklist() {
4332
  for (int i = 0; i < C->parse_predicate_count(); i++) {
4333
    ParsePredicateNode* parse_predicate_node = C->parse_predicate(i);
4334
    if (parse_predicate_node->is_useless()) {
4335
      _igvn._worklist.push(parse_predicate_node);
4336
    }
4337
  }
4338
}
4339

4340

4341
// Eliminate all Template Assertion Predicates that do not belong to their originally associated loop anymore by
4342
// replacing the Opaque4 node of the If node with true. These nodes will be removed during the next round of IGVN.
4343
void PhaseIdealLoop::eliminate_useless_template_assertion_predicates() {
4344
  Unique_Node_List useful_predicates;
4345
  if (C->has_loops()) {
4346
    collect_useful_template_assertion_predicates(useful_predicates);
4347
  }
4348
  eliminate_useless_template_assertion_predicates(useful_predicates);
4349
}
4350

4351
void PhaseIdealLoop::collect_useful_template_assertion_predicates(Unique_Node_List& useful_predicates) {
4352
  for (LoopTreeIterator iterator(_ltree_root); !iterator.done(); iterator.next()) {
4353
    IdealLoopTree* loop = iterator.current();
4354
    if (loop->can_apply_loop_predication()) {
4355
      collect_useful_template_assertion_predicates_for_loop(loop, useful_predicates);
4356
    }
4357
  }
4358
}
4359

4360
void PhaseIdealLoop::collect_useful_template_assertion_predicates_for_loop(IdealLoopTree* loop,
4361
                                                                           Unique_Node_List &useful_predicates) {
4362
  Node* entry = loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
4363
  const Predicates predicates(entry);
4364
  if (UseProfiledLoopPredicate) {
4365
    const PredicateBlock* profiled_loop_predicate_block = predicates.profiled_loop_predicate_block();
4366
    if (profiled_loop_predicate_block->has_parse_predicate()) {
4367
      IfProjNode* parse_predicate_proj = profiled_loop_predicate_block->parse_predicate_success_proj();
4368
      get_assertion_predicates(parse_predicate_proj, useful_predicates, true);
4369
    }
4370
  }
4371

4372
  if (UseLoopPredicate) {
4373
    const PredicateBlock* loop_predicate_block = predicates.loop_predicate_block();
4374
    if (loop_predicate_block->has_parse_predicate()) {
4375
      IfProjNode* parse_predicate_proj = loop_predicate_block->parse_predicate_success_proj();
4376
      get_assertion_predicates(parse_predicate_proj, useful_predicates, true);
4377
    }
4378
  }
4379
}
4380

4381
void PhaseIdealLoop::eliminate_useless_template_assertion_predicates(Unique_Node_List& useful_predicates) {
4382
  for (int i = C->template_assertion_predicate_count(); i > 0; i--) {
4383
    Opaque4Node* opaque4_node = C->template_assertion_predicate_opaq_node(i - 1)->as_Opaque4();
4384
    if (!useful_predicates.member(opaque4_node)) { // not in the useful list
4385
      _igvn.replace_node(opaque4_node, opaque4_node->in(2));
4386
    }
4387
  }
4388
}
4389

4390
// If a post or main loop is removed due to an assert predicate, the opaque that guards the loop is not needed anymore
4391
void PhaseIdealLoop::eliminate_useless_zero_trip_guard() {
4392
  if (_zero_trip_guard_opaque_nodes.size() == 0) {
4393
    return;
4394
  }
4395
  Unique_Node_List useful_zero_trip_guard_opaques_nodes;
4396
  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4397
    IdealLoopTree* lpt = iter.current();
4398
    if (lpt->_child == nullptr && lpt->is_counted()) {
4399
      CountedLoopNode* head = lpt->_head->as_CountedLoop();
4400
      Node* opaque = head->is_canonical_loop_entry();
4401
      if (opaque != nullptr) {
4402
        useful_zero_trip_guard_opaques_nodes.push(opaque);
4403
      }
4404
    }
4405
  }
4406
  for (uint i = 0; i < _zero_trip_guard_opaque_nodes.size(); ++i) {
4407
    OpaqueZeroTripGuardNode* opaque = ((OpaqueZeroTripGuardNode*)_zero_trip_guard_opaque_nodes.at(i));
4408
    DEBUG_ONLY(CountedLoopNode* guarded_loop = opaque->guarded_loop());
4409
    if (!useful_zero_trip_guard_opaques_nodes.member(opaque)) {
4410
      IfNode* iff = opaque->if_node();
4411
      IdealLoopTree* loop = get_loop(iff);
4412
      while (loop != _ltree_root && loop != nullptr) {
4413
        loop = loop->_parent;
4414
      }
4415
      if (loop == nullptr) {
4416
        // unreachable from _ltree_root: zero trip guard is in a newly discovered infinite loop.
4417
        // We can't tell if the opaque node is useful or not
4418
        assert(guarded_loop == nullptr || guarded_loop->is_in_infinite_subgraph(), "");
4419
      } else {
4420
        assert(guarded_loop == nullptr, "");
4421
        this->_igvn.replace_node(opaque, opaque->in(1));
4422
      }
4423
    } else {
4424
      assert(guarded_loop != nullptr, "");
4425
    }
4426
  }
4427
}
4428

4429
//------------------------process_expensive_nodes-----------------------------
4430
// Expensive nodes have their control input set to prevent the GVN
4431
// from commoning them and as a result forcing the resulting node to
4432
// be in a more frequent path. Use CFG information here, to change the
4433
// control inputs so that some expensive nodes can be commoned while
4434
// not executed more frequently.
4435
bool PhaseIdealLoop::process_expensive_nodes() {
4436
  assert(OptimizeExpensiveOps, "optimization off?");
4437

4438
  // Sort nodes to bring similar nodes together
4439
  C->sort_expensive_nodes();
4440

4441
  bool progress = false;
4442

4443
  for (int i = 0; i < C->expensive_count(); ) {
4444
    Node* n = C->expensive_node(i);
4445
    int start = i;
4446
    // Find nodes similar to n
4447
    i++;
4448
    for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
4449
    int end = i;
4450
    // And compare them two by two
4451
    for (int j = start; j < end; j++) {
4452
      Node* n1 = C->expensive_node(j);
4453
      if (is_node_unreachable(n1)) {
4454
        continue;
4455
      }
4456
      for (int k = j+1; k < end; k++) {
4457
        Node* n2 = C->expensive_node(k);
4458
        if (is_node_unreachable(n2)) {
4459
          continue;
4460
        }
4461

4462
        assert(n1 != n2, "should be pair of nodes");
4463

4464
        Node* c1 = n1->in(0);
4465
        Node* c2 = n2->in(0);
4466

4467
        Node* parent_c1 = c1;
4468
        Node* parent_c2 = c2;
4469

4470
        // The call to get_early_ctrl_for_expensive() moves the
4471
        // expensive nodes up but stops at loops that are in a if
4472
        // branch. See whether we can exit the loop and move above the
4473
        // If.
4474
        if (c1->is_Loop()) {
4475
          parent_c1 = c1->in(1);
4476
        }
4477
        if (c2->is_Loop()) {
4478
          parent_c2 = c2->in(1);
4479
        }
4480

4481
        if (parent_c1 == parent_c2) {
4482
          _igvn._worklist.push(n1);
4483
          _igvn._worklist.push(n2);
4484
          continue;
4485
        }
4486

4487
        // Look for identical expensive node up the dominator chain.
4488
        if (is_dominator(c1, c2)) {
4489
          c2 = c1;
4490
        } else if (is_dominator(c2, c1)) {
4491
          c1 = c2;
4492
        } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
4493
                   parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
4494
          // Both branches have the same expensive node so move it up
4495
          // before the if.
4496
          c1 = c2 = idom(parent_c1->in(0));
4497
        }
4498
        // Do the actual moves
4499
        if (n1->in(0) != c1) {
4500
          _igvn.replace_input_of(n1, 0, c1);
4501
          progress = true;
4502
        }
4503
        if (n2->in(0) != c2) {
4504
          _igvn.replace_input_of(n2, 0, c2);
4505
          progress = true;
4506
        }
4507
      }
4508
    }
4509
  }
4510

4511
  return progress;
4512
}
4513

4514
#ifdef ASSERT
4515
// Goes over all children of the root of the loop tree. Check if any of them have a path
4516
// down to Root, that does not go via a NeverBranch exit.
4517
bool PhaseIdealLoop::only_has_infinite_loops() {
4518
  ResourceMark rm;
4519
  Unique_Node_List worklist;
4520
  // start traversal at all loop heads of first-level loops
4521
  for (IdealLoopTree* l = _ltree_root->_child; l != nullptr; l = l->_next) {
4522
    Node* head = l->_head;
4523
    assert(head->is_Region(), "");
4524
    worklist.push(head);
4525
  }
4526
  return RegionNode::are_all_nodes_in_infinite_subgraph(worklist);
4527
}
4528
#endif
4529

4530

4531
//=============================================================================
4532
//----------------------------build_and_optimize-------------------------------
4533
// Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
4534
// its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
4535
void PhaseIdealLoop::build_and_optimize() {
4536
  assert(!C->post_loop_opts_phase(), "no loop opts allowed");
4537

4538
  bool do_split_ifs = (_mode == LoopOptsDefault);
4539
  bool skip_loop_opts = (_mode == LoopOptsNone);
4540
  bool do_max_unroll = (_mode == LoopOptsMaxUnroll);
4541

4542

4543
  int old_progress = C->major_progress();
4544
  uint orig_worklist_size = _igvn._worklist.size();
4545

4546
  // Reset major-progress flag for the driver's heuristics
4547
  C->clear_major_progress();
4548

4549
#ifndef PRODUCT
4550
  // Capture for later assert
4551
  uint unique = C->unique();
4552
  _loop_invokes++;
4553
  _loop_work += unique;
4554
#endif
4555

4556
  // True if the method has at least 1 irreducible loop
4557
  _has_irreducible_loops = false;
4558

4559
  _created_loop_node = false;
4560

4561
  VectorSet visited;
4562
  // Pre-grow the mapping from Nodes to IdealLoopTrees.
4563
  _loop_or_ctrl.map(C->unique(), nullptr);
4564
  memset(_loop_or_ctrl.adr(), 0, wordSize * C->unique());
4565

4566
  // Pre-build the top-level outermost loop tree entry
4567
  _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
4568
  // Do not need a safepoint at the top level
4569
  _ltree_root->_has_sfpt = 1;
4570

4571
  // Initialize Dominators.
4572
  // Checked in clone_loop_predicate() during beautify_loops().
4573
  _idom_size = 0;
4574
  _idom      = nullptr;
4575
  _dom_depth = nullptr;
4576
  _dom_stk   = nullptr;
4577

4578
  // Empty pre-order array
4579
  allocate_preorders();
4580

4581
  // Build a loop tree on the fly.  Build a mapping from CFG nodes to
4582
  // IdealLoopTree entries.  Data nodes are NOT walked.
4583
  build_loop_tree();
4584
  // Check for bailout, and return
4585
  if (C->failing()) {
4586
    return;
4587
  }
4588

4589
  // Verify that the has_loops() flag set at parse time is consistent
4590
  // with the just built loop tree. With infinite loops, it could be
4591
  // that one pass of loop opts only finds infinite loops, clears the
4592
  // has_loops() flag but adds NeverBranch nodes so the next loop opts
4593
  // verification pass finds a non empty loop tree. When the back edge
4594
  // is an exception edge, parsing doesn't set has_loops().
4595
  assert(_ltree_root->_child == nullptr || C->has_loops() || only_has_infinite_loops() || C->has_exception_backedge(), "parsing found no loops but there are some");
4596
  // No loops after all
4597
  if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
4598

4599
  // There should always be an outer loop containing the Root and Return nodes.
4600
  // If not, we have a degenerate empty program.  Bail out in this case.
4601
  if (!has_node(C->root())) {
4602
    if (!_verify_only) {
4603
      C->clear_major_progress();
4604
      assert(false, "empty program detected during loop optimization");
4605
      C->record_method_not_compilable("empty program detected during loop optimization");
4606
    }
4607
    return;
4608
  }
4609

4610
  BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4611
  // Nothing to do, so get out
4612
  bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !do_max_unroll && !_verify_me &&
4613
          !_verify_only && !bs->is_gc_specific_loop_opts_pass(_mode);
4614
  bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
4615
  bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(_mode);
4616
  if (stop_early && !do_expensive_nodes) {
4617
    return;
4618
  }
4619

4620
  // Set loop nesting depth
4621
  _ltree_root->set_nest( 0 );
4622

4623
  // Split shared headers and insert loop landing pads.
4624
  // Do not bother doing this on the Root loop of course.
4625
  if( !_verify_me && !_verify_only && _ltree_root->_child ) {
4626
    C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
4627
    if( _ltree_root->_child->beautify_loops( this ) ) {
4628
      // Re-build loop tree!
4629
      _ltree_root->_child = nullptr;
4630
      _loop_or_ctrl.clear();
4631
      reallocate_preorders();
4632
      build_loop_tree();
4633
      // Check for bailout, and return
4634
      if (C->failing()) {
4635
        return;
4636
      }
4637
      // Reset loop nesting depth
4638
      _ltree_root->set_nest( 0 );
4639

4640
      C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
4641
    }
4642
  }
4643

4644
  // Build Dominators for elision of null checks & loop finding.
4645
  // Since nodes do not have a slot for immediate dominator, make
4646
  // a persistent side array for that info indexed on node->_idx.
4647
  _idom_size = C->unique();
4648
  _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
4649
  _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
4650
  _dom_stk   = nullptr; // Allocated on demand in recompute_dom_depth
4651
  memset( _dom_depth, 0, _idom_size * sizeof(uint) );
4652

4653
  Dominators();
4654

4655
  if (!_verify_only) {
4656
    // As a side effect, Dominators removed any unreachable CFG paths
4657
    // into RegionNodes.  It doesn't do this test against Root, so
4658
    // we do it here.
4659
    for( uint i = 1; i < C->root()->req(); i++ ) {
4660
      if (!_loop_or_ctrl[C->root()->in(i)->_idx]) { // Dead path into Root?
4661
        _igvn.delete_input_of(C->root(), i);
4662
        i--;                      // Rerun same iteration on compressed edges
4663
      }
4664
    }
4665

4666
    // Given dominators, try to find inner loops with calls that must
4667
    // always be executed (call dominates loop tail).  These loops do
4668
    // not need a separate safepoint.
4669
    Node_List cisstack;
4670
    _ltree_root->check_safepts(visited, cisstack);
4671
  }
4672

4673
  // Walk the DATA nodes and place into loops.  Find earliest control
4674
  // node.  For CFG nodes, the _loop_or_ctrl array starts out and remains
4675
  // holding the associated IdealLoopTree pointer.  For DATA nodes, the
4676
  // _loop_or_ctrl array holds the earliest legal controlling CFG node.
4677

4678
  // Allocate stack with enough space to avoid frequent realloc
4679
  int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
4680
  Node_Stack nstack(stack_size);
4681

4682
  visited.clear();
4683
  Node_List worklist;
4684
  // Don't need C->root() on worklist since
4685
  // it will be processed among C->top() inputs
4686
  worklist.push(C->top());
4687
  visited.set(C->top()->_idx); // Set C->top() as visited now
4688
  build_loop_early( visited, worklist, nstack );
4689

4690
  // Given early legal placement, try finding counted loops.  This placement
4691
  // is good enough to discover most loop invariants.
4692
  if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
4693
    _ltree_root->counted_loop( this );
4694
  }
4695

4696
  // Find latest loop placement.  Find ideal loop placement.
4697
  visited.clear();
4698
  init_dom_lca_tags();
4699
  // Need C->root() on worklist when processing outs
4700
  worklist.push(C->root());
4701
  NOT_PRODUCT( C->verify_graph_edges(); )
4702
  worklist.push(C->top());
4703
  build_loop_late( visited, worklist, nstack );
4704
  if (C->failing()) { return; }
4705

4706
  if (_verify_only) {
4707
    C->restore_major_progress(old_progress);
4708
    assert(C->unique() == unique, "verification _mode made Nodes? ? ?");
4709
    assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
4710
    return;
4711
  }
4712

4713
  // clear out the dead code after build_loop_late
4714
  while (_deadlist.size()) {
4715
    _igvn.remove_globally_dead_node(_deadlist.pop());
4716
  }
4717

4718
  eliminate_useless_zero_trip_guard();
4719

4720
  if (stop_early) {
4721
    assert(do_expensive_nodes, "why are we here?");
4722
    if (process_expensive_nodes()) {
4723
      // If we made some progress when processing expensive nodes then
4724
      // the IGVN may modify the graph in a way that will allow us to
4725
      // make some more progress: we need to try processing expensive
4726
      // nodes again.
4727
      C->set_major_progress();
4728
    }
4729
    return;
4730
  }
4731

4732
  // Some parser-inserted loop predicates could never be used by loop
4733
  // predication or they were moved away from loop during some optimizations.
4734
  // For example, peeling. Eliminate them before next loop optimizations.
4735
  eliminate_useless_predicates();
4736

4737
#ifndef PRODUCT
4738
  C->verify_graph_edges();
4739
  if (_verify_me) {             // Nested verify pass?
4740
    // Check to see if the verify _mode is broken
4741
    assert(C->unique() == unique, "non-optimize _mode made Nodes? ? ?");
4742
    return;
4743
  }
4744
  DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
4745
  if (TraceLoopOpts && C->has_loops()) {
4746
    _ltree_root->dump();
4747
  }
4748
#endif
4749

4750
  if (skip_loop_opts) {
4751
    C->restore_major_progress(old_progress);
4752
    return;
4753
  }
4754

4755
  if (do_max_unroll) {
4756
    for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4757
      IdealLoopTree* lpt = iter.current();
4758
      if (lpt->is_innermost() && lpt->_allow_optimizations && !lpt->_has_call && lpt->is_counted()) {
4759
        lpt->compute_trip_count(this);
4760
        if (!lpt->do_one_iteration_loop(this) &&
4761
            !lpt->do_remove_empty_loop(this)) {
4762
          AutoNodeBudget node_budget(this);
4763
          if (lpt->_head->as_CountedLoop()->is_normal_loop() &&
4764
              lpt->policy_maximally_unroll(this)) {
4765
            memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
4766
            do_maximally_unroll(lpt, worklist);
4767
          }
4768
        }
4769
      }
4770
    }
4771

4772
    C->restore_major_progress(old_progress);
4773
    return;
4774
  }
4775

4776
  if (bs->optimize_loops(this, _mode, visited, nstack, worklist)) {
4777
    return;
4778
  }
4779

4780
  if (ReassociateInvariants && !C->major_progress()) {
4781
    // Reassociate invariants and prep for split_thru_phi
4782
    for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4783
      IdealLoopTree* lpt = iter.current();
4784
      if (!lpt->is_loop()) {
4785
        continue;
4786
      }
4787
      Node* head = lpt->_head;
4788
      if (!head->is_BaseCountedLoop() || !lpt->is_innermost()) continue;
4789

4790
      // check for vectorized loops, any reassociation of invariants was already done
4791
      if (head->is_CountedLoop()) {
4792
        if (head->as_CountedLoop()->is_unroll_only()) {
4793
          continue;
4794
        } else {
4795
          AutoNodeBudget node_budget(this);
4796
          lpt->reassociate_invariants(this);
4797
        }
4798
      }
4799
      // Because RCE opportunities can be masked by split_thru_phi,
4800
      // look for RCE candidates and inhibit split_thru_phi
4801
      // on just their loop-phi's for this pass of loop opts
4802
      if (SplitIfBlocks && do_split_ifs &&
4803
          head->as_BaseCountedLoop()->is_valid_counted_loop(head->as_BaseCountedLoop()->bt()) &&
4804
          (lpt->policy_range_check(this, true, T_LONG) ||
4805
           (head->is_CountedLoop() && lpt->policy_range_check(this, true, T_INT)))) {
4806
        lpt->_rce_candidate = 1; // = true
4807
      }
4808
    }
4809
  }
4810

4811
  // Check for aggressive application of split-if and other transforms
4812
  // that require basic-block info (like cloning through Phi's)
4813
  if (!C->major_progress() && SplitIfBlocks && do_split_ifs) {
4814
    visited.clear();
4815
    split_if_with_blocks( visited, nstack);
4816
    DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
4817
  }
4818

4819
  if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
4820
    C->set_major_progress();
4821
  }
4822

4823
  // Perform loop predication before iteration splitting
4824
  if (UseLoopPredicate && C->has_loops() && !C->major_progress() && (C->parse_predicate_count() > 0)) {
4825
    _ltree_root->_child->loop_predication(this);
4826
  }
4827

4828
  if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
4829
    if (do_intrinsify_fill()) {
4830
      C->set_major_progress();
4831
    }
4832
  }
4833

4834
  // Perform iteration-splitting on inner loops.  Split iterations to avoid
4835
  // range checks or one-shot null checks.
4836

4837
  // If split-if's didn't hack the graph too bad (no CFG changes)
4838
  // then do loop opts.
4839
  if (C->has_loops() && !C->major_progress()) {
4840
    memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
4841
    _ltree_root->_child->iteration_split( this, worklist );
4842
    // No verify after peeling!  GCM has hoisted code out of the loop.
4843
    // After peeling, the hoisted code could sink inside the peeled area.
4844
    // The peeling code does not try to recompute the best location for
4845
    // all the code before the peeled area, so the verify pass will always
4846
    // complain about it.
4847
  }
4848

4849
  // Check for bailout, and return
4850
  if (C->failing()) {
4851
    return;
4852
  }
4853

4854
  // Do verify graph edges in any case
4855
  NOT_PRODUCT( C->verify_graph_edges(); );
4856

4857
  if (!do_split_ifs) {
4858
    // We saw major progress in Split-If to get here.  We forced a
4859
    // pass with unrolling and not split-if, however more split-if's
4860
    // might make progress.  If the unrolling didn't make progress
4861
    // then the major-progress flag got cleared and we won't try
4862
    // another round of Split-If.  In particular the ever-common
4863
    // instance-of/check-cast pattern requires at least 2 rounds of
4864
    // Split-If to clear out.
4865
    C->set_major_progress();
4866
  }
4867

4868
  // Repeat loop optimizations if new loops were seen
4869
  if (created_loop_node()) {
4870
    C->set_major_progress();
4871
  }
4872

4873
  // Keep loop predicates and perform optimizations with them
4874
  // until no more loop optimizations could be done.
4875
  // After that switch predicates off and do more loop optimizations.
4876
  if (!C->major_progress() && (C->parse_predicate_count() > 0)) {
4877
    C->mark_parse_predicate_nodes_useless(_igvn);
4878
    assert(C->parse_predicate_count() == 0, "should be zero now");
4879
     if (TraceLoopOpts) {
4880
       tty->print_cr("PredicatesOff");
4881
     }
4882
     C->set_major_progress();
4883
  }
4884

4885
  // Auto-vectorize main-loop
4886
  if (C->do_superword() && C->has_loops() && !C->major_progress()) {
4887
    Compile::TracePhase tp("autoVectorize", &timers[_t_autoVectorize]);
4888

4889
    // Shared data structures for all AutoVectorizations, to reduce allocations
4890
    // of large arrays.
4891
    VSharedData vshared;
4892
    for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4893
      IdealLoopTree* lpt = iter.current();
4894
      AutoVectorizeStatus status = auto_vectorize(lpt, vshared);
4895

4896
      if (status == AutoVectorizeStatus::TriedAndFailed) {
4897
        // We tried vectorization, but failed. From now on only unroll the loop.
4898
        CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4899
        if (cl->has_passed_slp()) {
4900
          C->set_major_progress();
4901
          cl->set_notpassed_slp();
4902
          cl->mark_do_unroll_only();
4903
        }
4904
      }
4905
    }
4906
  }
4907

4908
  // Move UnorderedReduction out of counted loop. Can be introduced by AutoVectorization.
4909
  if (C->has_loops() && !C->major_progress()) {
4910
    for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4911
      IdealLoopTree* lpt = iter.current();
4912
      if (lpt->is_counted() && lpt->is_innermost()) {
4913
        move_unordered_reduction_out_of_loop(lpt);
4914
      }
4915
    }
4916
  }
4917
}
4918

4919
#ifndef PRODUCT
4920
//------------------------------print_statistics-------------------------------
4921
int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
4922
int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
4923
volatile int PhaseIdealLoop::_long_loop_candidates=0; // Number of long loops seen
4924
volatile int PhaseIdealLoop::_long_loop_nests=0; // Number of long loops successfully transformed to a nest
4925
volatile int PhaseIdealLoop::_long_loop_counted_loops=0; // Number of long loops successfully transformed to a counted loop
4926
void PhaseIdealLoop::print_statistics() {
4927
  tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d, long loops=%d/%d/%d", _loop_invokes, _loop_work, _long_loop_counted_loops, _long_loop_nests, _long_loop_candidates);
4928
}
4929
#endif
4930

4931
#ifdef ASSERT
4932
// Build a verify-only PhaseIdealLoop, and see that it agrees with "this".
4933
void PhaseIdealLoop::verify() const {
4934
  ResourceMark rm;
4935
  int old_progress = C->major_progress();
4936
  bool success = true;
4937

4938
  PhaseIdealLoop phase_verify(_igvn, this);
4939
  if (C->failing()) return;
4940

4941
  // Verify ctrl and idom of every node.
4942
  success &= verify_idom_and_nodes(C->root(), &phase_verify);
4943

4944
  // Verify loop-tree.
4945
  success &= _ltree_root->verify_tree(phase_verify._ltree_root);
4946

4947
  assert(success, "VerifyLoopOptimizations failed");
4948

4949
  // Major progress was cleared by creating a verify version of PhaseIdealLoop.
4950
  C->restore_major_progress(old_progress);
4951
}
4952

4953
// Perform a BFS starting at n, through all inputs.
4954
// Call verify_idom and verify_node on all nodes of BFS traversal.
4955
bool PhaseIdealLoop::verify_idom_and_nodes(Node* root, const PhaseIdealLoop* phase_verify) const {
4956
  Unique_Node_List worklist;
4957
  worklist.push(root);
4958
  bool success = true;
4959
  for (uint i = 0; i < worklist.size(); i++) {
4960
    Node* n = worklist.at(i);
4961
    // process node
4962
    success &= verify_idom(n, phase_verify);
4963
    success &= verify_loop_ctrl(n, phase_verify);
4964
    // visit inputs
4965
    for (uint j = 0; j < n->req(); j++) {
4966
      if (n->in(j) != nullptr) {
4967
        worklist.push(n->in(j));
4968
      }
4969
    }
4970
  }
4971
  return success;
4972
}
4973

4974
// Verify dominator structure (IDOM).
4975
bool PhaseIdealLoop::verify_idom(Node* n, const PhaseIdealLoop* phase_verify) const {
4976
  // Verify IDOM for all CFG nodes (except root).
4977
  if (!n->is_CFG() || n->is_Root()) {
4978
    return true; // pass
4979
  }
4980

4981
  if (n->_idx >= _idom_size) {
4982
    tty->print("CFG Node with no idom: ");
4983
    n->dump();
4984
    return false; // fail
4985
  }
4986

4987
  Node* id = idom_no_update(n);
4988
  Node* id_verify = phase_verify->idom_no_update(n);
4989
  if (id != id_verify) {
4990
    tty->print("Mismatching idom for node: ");
4991
    n->dump();
4992
    tty->print("  We have idom: ");
4993
    id->dump();
4994
    tty->print("  Verify has idom: ");
4995
    id_verify->dump();
4996
    tty->cr();
4997
    return false; // fail
4998
  }
4999
  return true; // pass
5000
}
5001

5002
// Verify "_loop_or_ctrl": control and loop membership.
5003
//  (0) _loop_or_ctrl[i] == nullptr -> node not reachable.
5004
//  (1) has_ctrl -> check lowest bit. 1 -> data node. 0 -> ctrl node.
5005
//  (2) has_ctrl true: get_ctrl_no_update returns ctrl of data node.
5006
//  (3) has_ctrl false: get_loop_idx returns IdealLoopTree for ctrl node.
5007
bool PhaseIdealLoop::verify_loop_ctrl(Node* n, const PhaseIdealLoop* phase_verify) const {
5008
  const uint i = n->_idx;
5009
  // The loop-tree was built from def to use (top-down).
5010
  // The verification happens from use to def (bottom-up).
5011
  // We may thus find nodes during verification that are not in the loop-tree.
5012
  if (_loop_or_ctrl[i] == nullptr || phase_verify->_loop_or_ctrl[i] == nullptr) {
5013
    if (_loop_or_ctrl[i] != nullptr || phase_verify->_loop_or_ctrl[i] != nullptr) {
5014
      tty->print_cr("Was reachable in only one. this %d, verify %d.",
5015
                 _loop_or_ctrl[i] != nullptr, phase_verify->_loop_or_ctrl[i] != nullptr);
5016
      n->dump();
5017
      return false; // fail
5018
    }
5019
    // Not reachable for both.
5020
    return true; // pass
5021
  }
5022

5023
  if (n->is_CFG() == has_ctrl(n)) {
5024
    tty->print_cr("Exactly one should be true: %d for is_CFG, %d for has_ctrl.", n->is_CFG(), has_ctrl(n));
5025
    n->dump();
5026
    return false; // fail
5027
  }
5028

5029
  if (has_ctrl(n) != phase_verify->has_ctrl(n)) {
5030
    tty->print_cr("Mismatch has_ctrl: %d for this, %d for verify.", has_ctrl(n), phase_verify->has_ctrl(n));
5031
    n->dump();
5032
    return false; // fail
5033
  } else if (has_ctrl(n)) {
5034
    assert(phase_verify->has_ctrl(n), "sanity");
5035
    // n is a data node.
5036
    // Verify that its ctrl is the same.
5037

5038
    // Broken part of VerifyLoopOptimizations (A)
5039
    // Reason:
5040
    //   BUG, wrong control set for example in
5041
    //   PhaseIdealLoop::split_if_with_blocks
5042
    //   at "set_ctrl(x, new_ctrl);"
5043
    /*
5044
    if( _loop_or_ctrl[i] != loop_verify->_loop_or_ctrl[i] &&
5045
        get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
5046
      tty->print("Mismatched control setting for: ");
5047
      n->dump();
5048
      if( fail++ > 10 ) return;
5049
      Node *c = get_ctrl_no_update(n);
5050
      tty->print("We have it as: ");
5051
      if( c->in(0) ) c->dump();
5052
        else tty->print_cr("N%d",c->_idx);
5053
      tty->print("Verify thinks: ");
5054
      if( loop_verify->has_ctrl(n) )
5055
        loop_verify->get_ctrl_no_update(n)->dump();
5056
      else
5057
        loop_verify->get_loop_idx(n)->dump();
5058
      tty->cr();
5059
    }
5060
    */
5061
    return true; // pass
5062
  } else {
5063
    assert(!phase_verify->has_ctrl(n), "sanity");
5064
    // n is a ctrl node.
5065
    // Verify that not has_ctrl, and that get_loop_idx is the same.
5066

5067
    // Broken part of VerifyLoopOptimizations (B)
5068
    // Reason:
5069
    //   NeverBranch node for example is added to loop outside its scope.
5070
    //   Once we run build_loop_tree again, it is added to the correct loop.
5071
    /*
5072
    if (!C->major_progress()) {
5073
      // Loop selection can be messed up if we did a major progress
5074
      // operation, like split-if.  Do not verify in that case.
5075
      IdealLoopTree *us = get_loop_idx(n);
5076
      IdealLoopTree *them = loop_verify->get_loop_idx(n);
5077
      if( us->_head != them->_head ||  us->_tail != them->_tail ) {
5078
        tty->print("Unequals loops for: ");
5079
        n->dump();
5080
        if( fail++ > 10 ) return;
5081
        tty->print("We have it as: ");
5082
        us->dump();
5083
        tty->print("Verify thinks: ");
5084
        them->dump();
5085
        tty->cr();
5086
      }
5087
    }
5088
    */
5089
    return true; // pass
5090
  }
5091
}
5092

5093
static int compare_tree(IdealLoopTree* const& a, IdealLoopTree* const& b) {
5094
  assert(a != nullptr && b != nullptr, "must be");
5095
  return a->_head->_idx - b->_head->_idx;
5096
}
5097

5098
GrowableArray<IdealLoopTree*> IdealLoopTree::collect_sorted_children() const {
5099
  GrowableArray<IdealLoopTree*> children;
5100
  IdealLoopTree* child = _child;
5101
  while (child != nullptr) {
5102
    assert(child->_parent == this, "all must be children of this");
5103
    children.insert_sorted<compare_tree>(child);
5104
    child = child->_next;
5105
  }
5106
  return children;
5107
}
5108

5109
// Verify that tree structures match. Because the CFG can change, siblings
5110
// within the loop tree can be reordered. We attempt to deal with that by
5111
// reordering the verify's loop tree if possible.
5112
bool IdealLoopTree::verify_tree(IdealLoopTree* loop_verify) const {
5113
  assert(_head == loop_verify->_head, "mismatched loop head");
5114
  assert(this->_parent != nullptr || this->_next == nullptr, "is_root_loop implies has_no_sibling");
5115

5116
  // Collect the children
5117
  GrowableArray<IdealLoopTree*> children = collect_sorted_children();
5118
  GrowableArray<IdealLoopTree*> children_verify = loop_verify->collect_sorted_children();
5119

5120
  bool success = true;
5121

5122
  // Compare the two children lists
5123
  for (int i = 0, j = 0; i < children.length() || j < children_verify.length(); ) {
5124
    IdealLoopTree* child        = nullptr;
5125
    IdealLoopTree* child_verify = nullptr;
5126
    // Read from both lists, if possible.
5127
    if (i < children.length()) {
5128
      child = children.at(i);
5129
    }
5130
    if (j < children_verify.length()) {
5131
      child_verify = children_verify.at(j);
5132
    }
5133
    assert(child != nullptr || child_verify != nullptr, "must find at least one");
5134
    if (child != nullptr && child_verify != nullptr && child->_head != child_verify->_head) {
5135
      // We found two non-equal children. Select the smaller one.
5136
      if (child->_head->_idx < child_verify->_head->_idx) {
5137
        child_verify = nullptr;
5138
      } else {
5139
        child = nullptr;
5140
      }
5141
    }
5142
    // Process the two children, or potentially log the failure if we only found one.
5143
    if (child_verify == nullptr) {
5144
      if (child->_irreducible && Compile::current()->major_progress()) {
5145
        // Irreducible loops can pick a different header (one of its entries).
5146
      } else {
5147
        tty->print_cr("We have a loop that verify does not have");
5148
        child->dump();
5149
        success = false;
5150
      }
5151
      i++; // step for this
5152
    } else if (child == nullptr) {
5153
      if (child_verify->_irreducible && Compile::current()->major_progress()) {
5154
        // Irreducible loops can pick a different header (one of its entries).
5155
      } else if (child_verify->_head->as_Region()->is_in_infinite_subgraph()) {
5156
        // Infinite loops do not get attached to the loop-tree on their first visit.
5157
        // "this" runs before "loop_verify". It is thus possible that we find the
5158
        // infinite loop only for "child_verify". Only finding it with "child" would
5159
        // mean that we lost it, which is not ok.
5160
      } else {
5161
        tty->print_cr("Verify has a loop that we do not have");
5162
        child_verify->dump();
5163
        success = false;
5164
      }
5165
      j++; // step for verify
5166
    } else {
5167
      assert(child->_head == child_verify->_head, "We have both and they are equal");
5168
      success &= child->verify_tree(child_verify); // Recursion
5169
      i++; // step for this
5170
      j++; // step for verify
5171
    }
5172
  }
5173

5174
  // Broken part of VerifyLoopOptimizations (D)
5175
  // Reason:
5176
  //   split_if has to update the _tail, if it is modified. But that is done by
5177
  //   checking to what loop the iff belongs to. That info can be wrong, and then
5178
  //   we do not update the _tail correctly.
5179
  /*
5180
  Node *tail = _tail;           // Inline a non-updating version of
5181
  while( !tail->in(0) )         // the 'tail()' call.
5182
    tail = tail->in(1);
5183
  assert( tail == loop->_tail, "mismatched loop tail" );
5184
  */
5185

5186
  if (_head->is_CountedLoop()) {
5187
    CountedLoopNode *cl = _head->as_CountedLoop();
5188

5189
    Node* ctrl     = cl->init_control();
5190
    Node* back     = cl->back_control();
5191
    assert(ctrl != nullptr && ctrl->is_CFG(), "sane loop in-ctrl");
5192
    assert(back != nullptr && back->is_CFG(), "sane loop backedge");
5193
    cl->loopexit(); // assert implied
5194
  }
5195

5196
  // Broken part of VerifyLoopOptimizations (E)
5197
  // Reason:
5198
  //   PhaseIdealLoop::split_thru_region creates new nodes for loop that are not added
5199
  //   to the loop body. Or maybe they are not added to the correct loop.
5200
  //   at "Node* x = n->clone();"
5201
  /*
5202
  // Innermost loops need to verify loop bodies,
5203
  // but only if no 'major_progress'
5204
  int fail = 0;
5205
  if (!Compile::current()->major_progress() && _child == nullptr) {
5206
    for( uint i = 0; i < _body.size(); i++ ) {
5207
      Node *n = _body.at(i);
5208
      if (n->outcnt() == 0)  continue; // Ignore dead
5209
      uint j;
5210
      for( j = 0; j < loop->_body.size(); j++ )
5211
        if( loop->_body.at(j) == n )
5212
          break;
5213
      if( j == loop->_body.size() ) { // Not found in loop body
5214
        // Last ditch effort to avoid assertion: Its possible that we
5215
        // have some users (so outcnt not zero) but are still dead.
5216
        // Try to find from root.
5217
        if (Compile::current()->root()->find(n->_idx)) {
5218
          fail++;
5219
          tty->print("We have that verify does not: ");
5220
          n->dump();
5221
        }
5222
      }
5223
    }
5224
    for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
5225
      Node *n = loop->_body.at(i2);
5226
      if (n->outcnt() == 0)  continue; // Ignore dead
5227
      uint j;
5228
      for( j = 0; j < _body.size(); j++ )
5229
        if( _body.at(j) == n )
5230
          break;
5231
      if( j == _body.size() ) { // Not found in loop body
5232
        // Last ditch effort to avoid assertion: Its possible that we
5233
        // have some users (so outcnt not zero) but are still dead.
5234
        // Try to find from root.
5235
        if (Compile::current()->root()->find(n->_idx)) {
5236
          fail++;
5237
          tty->print("Verify has that we do not: ");
5238
          n->dump();
5239
        }
5240
      }
5241
    }
5242
    assert( !fail, "loop body mismatch" );
5243
  }
5244
  */
5245
  return success;
5246
}
5247
#endif
5248

5249
//------------------------------set_idom---------------------------------------
5250
void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
5251
  _nesting.check(); // Check if a potential reallocation in the resource arena is safe
5252
  uint idx = d->_idx;
5253
  if (idx >= _idom_size) {
5254
    uint newsize = next_power_of_2(idx);
5255
    _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
5256
    _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
5257
    memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
5258
    _idom_size = newsize;
5259
  }
5260
  _idom[idx] = n;
5261
  _dom_depth[idx] = dom_depth;
5262
}
5263

5264
//------------------------------recompute_dom_depth---------------------------------------
5265
// The dominator tree is constructed with only parent pointers.
5266
// This recomputes the depth in the tree by first tagging all
5267
// nodes as "no depth yet" marker.  The next pass then runs up
5268
// the dom tree from each node marked "no depth yet", and computes
5269
// the depth on the way back down.
5270
void PhaseIdealLoop::recompute_dom_depth() {
5271
  uint no_depth_marker = C->unique();
5272
  uint i;
5273
  // Initialize depth to "no depth yet" and realize all lazy updates
5274
  for (i = 0; i < _idom_size; i++) {
5275
    // Only indices with a _dom_depth has a Node* or null (otherwise uninitialized).
5276
    if (_dom_depth[i] > 0 && _idom[i] != nullptr) {
5277
      _dom_depth[i] = no_depth_marker;
5278

5279
      // heal _idom if it has a fwd mapping in _loop_or_ctrl
5280
      if (_idom[i]->in(0) == nullptr) {
5281
        idom(i);
5282
      }
5283
    }
5284
  }
5285
  if (_dom_stk == nullptr) {
5286
    uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
5287
    if (init_size < 10) init_size = 10;
5288
    _dom_stk = new GrowableArray<uint>(init_size);
5289
  }
5290
  // Compute new depth for each node.
5291
  for (i = 0; i < _idom_size; i++) {
5292
    uint j = i;
5293
    // Run up the dom tree to find a node with a depth
5294
    while (_dom_depth[j] == no_depth_marker) {
5295
      _dom_stk->push(j);
5296
      j = _idom[j]->_idx;
5297
    }
5298
    // Compute the depth on the way back down this tree branch
5299
    uint dd = _dom_depth[j] + 1;
5300
    while (_dom_stk->length() > 0) {
5301
      uint j = _dom_stk->pop();
5302
      _dom_depth[j] = dd;
5303
      dd++;
5304
    }
5305
  }
5306
}
5307

5308
//------------------------------sort-------------------------------------------
5309
// Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
5310
// loop tree, not the root.
5311
IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
5312
  if( !innermost ) return loop; // New innermost loop
5313

5314
  int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
5315
  assert( loop_preorder, "not yet post-walked loop" );
5316
  IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
5317
  IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
5318

5319
  // Insert at start of list
5320
  while( l ) {                  // Insertion sort based on pre-order
5321
    if( l == loop ) return innermost; // Already on list!
5322
    int l_preorder = get_preorder(l->_head); // Cache pre-order number
5323
    assert( l_preorder, "not yet post-walked l" );
5324
    // Check header pre-order number to figure proper nesting
5325
    if( loop_preorder > l_preorder )
5326
      break;                    // End of insertion
5327
    // If headers tie (e.g., shared headers) check tail pre-order numbers.
5328
    // Since I split shared headers, you'd think this could not happen.
5329
    // BUT: I must first do the preorder numbering before I can discover I
5330
    // have shared headers, so the split headers all get the same preorder
5331
    // number as the RegionNode they split from.
5332
    if( loop_preorder == l_preorder &&
5333
        get_preorder(loop->_tail) < get_preorder(l->_tail) )
5334
      break;                    // Also check for shared headers (same pre#)
5335
    pp = &l->_parent;           // Chain up list
5336
    l = *pp;
5337
  }
5338
  // Link into list
5339
  // Point predecessor to me
5340
  *pp = loop;
5341
  // Point me to successor
5342
  IdealLoopTree *p = loop->_parent;
5343
  loop->_parent = l;            // Point me to successor
5344
  if( p ) sort( p, innermost ); // Insert my parents into list as well
5345
  return innermost;
5346
}
5347

5348
//------------------------------build_loop_tree--------------------------------
5349
// I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
5350
// bits.  The _loop_or_ctrl[] array is mapped by Node index and holds a null for
5351
// not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
5352
// tightest enclosing IdealLoopTree for post-walked.
5353
//
5354
// During my forward walk I do a short 1-layer lookahead to see if I can find
5355
// a loop backedge with that doesn't have any work on the backedge.  This
5356
// helps me construct nested loops with shared headers better.
5357
//
5358
// Once I've done the forward recursion, I do the post-work.  For each child
5359
// I check to see if there is a backedge.  Backedges define a loop!  I
5360
// insert an IdealLoopTree at the target of the backedge.
5361
//
5362
// During the post-work I also check to see if I have several children
5363
// belonging to different loops.  If so, then this Node is a decision point
5364
// where control flow can choose to change loop nests.  It is at this
5365
// decision point where I can figure out how loops are nested.  At this
5366
// time I can properly order the different loop nests from my children.
5367
// Note that there may not be any backedges at the decision point!
5368
//
5369
// Since the decision point can be far removed from the backedges, I can't
5370
// order my loops at the time I discover them.  Thus at the decision point
5371
// I need to inspect loop header pre-order numbers to properly nest my
5372
// loops.  This means I need to sort my childrens' loops by pre-order.
5373
// The sort is of size number-of-control-children, which generally limits
5374
// it to size 2 (i.e., I just choose between my 2 target loops).
5375
void PhaseIdealLoop::build_loop_tree() {
5376
  // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
5377
  GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
5378
  Node *n = C->root();
5379
  bltstack.push(n);
5380
  int pre_order = 1;
5381
  int stack_size;
5382

5383
  while ( ( stack_size = bltstack.length() ) != 0 ) {
5384
    n = bltstack.top(); // Leave node on stack
5385
    if ( !is_visited(n) ) {
5386
      // ---- Pre-pass Work ----
5387
      // Pre-walked but not post-walked nodes need a pre_order number.
5388

5389
      set_preorder_visited( n, pre_order ); // set as visited
5390

5391
      // ---- Scan over children ----
5392
      // Scan first over control projections that lead to loop headers.
5393
      // This helps us find inner-to-outer loops with shared headers better.
5394

5395
      // Scan children's children for loop headers.
5396
      for ( int i = n->outcnt() - 1; i >= 0; --i ) {
5397
        Node* m = n->raw_out(i);       // Child
5398
        if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
5399
          // Scan over children's children to find loop
5400
          for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
5401
            Node* l = m->fast_out(j);
5402
            if( is_visited(l) &&       // Been visited?
5403
                !is_postvisited(l) &&  // But not post-visited
5404
                get_preorder(l) < pre_order ) { // And smaller pre-order
5405
              // Found!  Scan the DFS down this path before doing other paths
5406
              bltstack.push(m);
5407
              break;
5408
            }
5409
          }
5410
        }
5411
      }
5412
      pre_order++;
5413
    }
5414
    else if ( !is_postvisited(n) ) {
5415
      // Note: build_loop_tree_impl() adds out edges on rare occasions,
5416
      // such as com.sun.rsasign.am::a.
5417
      // For non-recursive version, first, process current children.
5418
      // On next iteration, check if additional children were added.
5419
      for ( int k = n->outcnt() - 1; k >= 0; --k ) {
5420
        Node* u = n->raw_out(k);
5421
        if ( u->is_CFG() && !is_visited(u) ) {
5422
          bltstack.push(u);
5423
        }
5424
      }
5425
      if ( bltstack.length() == stack_size ) {
5426
        // There were no additional children, post visit node now
5427
        (void)bltstack.pop(); // Remove node from stack
5428
        pre_order = build_loop_tree_impl( n, pre_order );
5429
        // Check for bailout
5430
        if (C->failing()) {
5431
          return;
5432
        }
5433
        // Check to grow _preorders[] array for the case when
5434
        // build_loop_tree_impl() adds new nodes.
5435
        check_grow_preorders();
5436
      }
5437
    }
5438
    else {
5439
      (void)bltstack.pop(); // Remove post-visited node from stack
5440
    }
5441
  }
5442
  DEBUG_ONLY(verify_regions_in_irreducible_loops();)
5443
}
5444

5445
//------------------------------build_loop_tree_impl---------------------------
5446
int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
5447
  // ---- Post-pass Work ----
5448
  // Pre-walked but not post-walked nodes need a pre_order number.
5449

5450
  // Tightest enclosing loop for this Node
5451
  IdealLoopTree *innermost = nullptr;
5452

5453
  // For all children, see if any edge is a backedge.  If so, make a loop
5454
  // for it.  Then find the tightest enclosing loop for the self Node.
5455
  for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
5456
    Node* m = n->fast_out(i);   // Child
5457
    if( n == m ) continue;      // Ignore control self-cycles
5458
    if( !m->is_CFG() ) continue;// Ignore non-CFG edges
5459

5460
    IdealLoopTree *l;           // Child's loop
5461
    if( !is_postvisited(m) ) {  // Child visited but not post-visited?
5462
      // Found a backedge
5463
      assert( get_preorder(m) < pre_order, "should be backedge" );
5464
      // Check for the RootNode, which is already a LoopNode and is allowed
5465
      // to have multiple "backedges".
5466
      if( m == C->root()) {     // Found the root?
5467
        l = _ltree_root;        // Root is the outermost LoopNode
5468
      } else {                  // Else found a nested loop
5469
        // Insert a LoopNode to mark this loop.
5470
        l = new IdealLoopTree(this, m, n);
5471
      } // End of Else found a nested loop
5472
      if( !has_loop(m) )        // If 'm' does not already have a loop set
5473
        set_loop(m, l);         // Set loop header to loop now
5474

5475
    } else {                    // Else not a nested loop
5476
      if (!_loop_or_ctrl[m->_idx]) continue; // Dead code has no loop
5477
      IdealLoopTree* m_loop = get_loop(m);
5478
      l = m_loop;          // Get previously determined loop
5479
      // If successor is header of a loop (nest), move up-loop till it
5480
      // is a member of some outer enclosing loop.  Since there are no
5481
      // shared headers (I've split them already) I only need to go up
5482
      // at most 1 level.
5483
      while( l && l->_head == m ) // Successor heads loop?
5484
        l = l->_parent;         // Move up 1 for me
5485
      // If this loop is not properly parented, then this loop
5486
      // has no exit path out, i.e. its an infinite loop.
5487
      if( !l ) {
5488
        // Make loop "reachable" from root so the CFG is reachable.  Basically
5489
        // insert a bogus loop exit that is never taken.  'm', the loop head,
5490
        // points to 'n', one (of possibly many) fall-in paths.  There may be
5491
        // many backedges as well.
5492

5493
        // Here I set the loop to be the root loop.  I could have, after
5494
        // inserting a bogus loop exit, restarted the recursion and found my
5495
        // new loop exit.  This would make the infinite loop a first-class
5496
        // loop and it would then get properly optimized.  What's the use of
5497
        // optimizing an infinite loop?
5498
        l = _ltree_root;        // Oops, found infinite loop
5499

5500
        if (!_verify_only) {
5501
          // Insert the NeverBranch between 'm' and it's control user.
5502
          NeverBranchNode *iff = new NeverBranchNode( m );
5503
          _igvn.register_new_node_with_optimizer(iff);
5504
          set_loop(iff, m_loop);
5505
          Node *if_t = new CProjNode( iff, 0 );
5506
          _igvn.register_new_node_with_optimizer(if_t);
5507
          set_loop(if_t, m_loop);
5508

5509
          Node* cfg = nullptr;       // Find the One True Control User of m
5510
          for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
5511
            Node* x = m->fast_out(j);
5512
            if (x->is_CFG() && x != m && x != iff)
5513
              { cfg = x; break; }
5514
          }
5515
          assert(cfg != nullptr, "must find the control user of m");
5516
          uint k = 0;             // Probably cfg->in(0)
5517
          while( cfg->in(k) != m ) k++; // But check in case cfg is a Region
5518
          _igvn.replace_input_of(cfg, k, if_t); // Now point to NeverBranch
5519

5520
          // Now create the never-taken loop exit
5521
          Node *if_f = new CProjNode( iff, 1 );
5522
          _igvn.register_new_node_with_optimizer(if_f);
5523
          set_loop(if_f, l);
5524
          // Find frame ptr for Halt.  Relies on the optimizer
5525
          // V-N'ing.  Easier and quicker than searching through
5526
          // the program structure.
5527
          Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
5528
          _igvn.register_new_node_with_optimizer(frame);
5529
          // Halt & Catch Fire
5530
          Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
5531
          _igvn.register_new_node_with_optimizer(halt);
5532
          set_loop(halt, l);
5533
          _igvn.add_input_to(C->root(), halt);
5534
        }
5535
        set_loop(C->root(), _ltree_root);
5536
      }
5537
    }
5538
    if (is_postvisited(l->_head)) {
5539
      // We are currently visiting l, but its head has already been post-visited.
5540
      // l is irreducible: we just found a second entry m.
5541
      _has_irreducible_loops = true;
5542
      RegionNode* secondary_entry = m->as_Region();
5543
      DEBUG_ONLY(secondary_entry->verify_can_be_irreducible_entry();)
5544

5545
      // Walk up the loop-tree, mark all loops that are already post-visited as irreducible
5546
      // Since m is a secondary entry to them all.
5547
      while( is_postvisited(l->_head) ) {
5548
        l->_irreducible = 1; // = true
5549
        RegionNode* head = l->_head->as_Region();
5550
        DEBUG_ONLY(head->verify_can_be_irreducible_entry();)
5551
        l = l->_parent;
5552
        // Check for bad CFG here to prevent crash, and bailout of compile
5553
        if (l == nullptr) {
5554
#ifndef PRODUCT
5555
          if (TraceLoopOpts) {
5556
            tty->print_cr("bailout: unhandled CFG: infinite irreducible loop");
5557
            m->dump();
5558
          }
5559
#endif
5560
          // This is a rare case that we do not want to handle in C2.
5561
          C->record_method_not_compilable("unhandled CFG detected during loop optimization");
5562
          return pre_order;
5563
        }
5564
      }
5565
    }
5566
    if (!_verify_only) {
5567
      C->set_has_irreducible_loop(_has_irreducible_loops);
5568
    }
5569

5570
    // This Node might be a decision point for loops.  It is only if
5571
    // it's children belong to several different loops.  The sort call
5572
    // does a trivial amount of work if there is only 1 child or all
5573
    // children belong to the same loop.  If however, the children
5574
    // belong to different loops, the sort call will properly set the
5575
    // _parent pointers to show how the loops nest.
5576
    //
5577
    // In any case, it returns the tightest enclosing loop.
5578
    innermost = sort( l, innermost );
5579
  }
5580

5581
  // Def-use info will have some dead stuff; dead stuff will have no
5582
  // loop decided on.
5583

5584
  // Am I a loop header?  If so fix up my parent's child and next ptrs.
5585
  if( innermost && innermost->_head == n ) {
5586
    assert( get_loop(n) == innermost, "" );
5587
    IdealLoopTree *p = innermost->_parent;
5588
    IdealLoopTree *l = innermost;
5589
    while( p && l->_head == n ) {
5590
      l->_next = p->_child;     // Put self on parents 'next child'
5591
      p->_child = l;            // Make self as first child of parent
5592
      l = p;                    // Now walk up the parent chain
5593
      p = l->_parent;
5594
    }
5595
  } else {
5596
    // Note that it is possible for a LoopNode to reach here, if the
5597
    // backedge has been made unreachable (hence the LoopNode no longer
5598
    // denotes a Loop, and will eventually be removed).
5599

5600
    // Record tightest enclosing loop for self.  Mark as post-visited.
5601
    set_loop(n, innermost);
5602
    // Also record has_call flag early on
5603
    if( innermost ) {
5604
      if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
5605
        // Do not count uncommon calls
5606
        if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
5607
          Node *iff = n->in(0)->in(0);
5608
          // No any calls for vectorized loops.
5609
          if (C->do_superword() ||
5610
              !iff->is_If() ||
5611
              (n->in(0)->Opcode() == Op_IfFalse && (1.0 - iff->as_If()->_prob) >= 0.01) ||
5612
              iff->as_If()->_prob >= 0.01) {
5613
            innermost->_has_call = 1;
5614
          }
5615
        }
5616
      } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
5617
        // Disable loop optimizations if the loop has a scalar replaceable
5618
        // allocation. This disabling may cause a potential performance lost
5619
        // if the allocation is not eliminated for some reason.
5620
        innermost->_allow_optimizations = false;
5621
        innermost->_has_call = 1; // = true
5622
      } else if (n->Opcode() == Op_SafePoint) {
5623
        // Record all safepoints in this loop.
5624
        if (innermost->_safepts == nullptr) innermost->_safepts = new Node_List();
5625
        innermost->_safepts->push(n);
5626
      }
5627
    }
5628
  }
5629

5630
  // Flag as post-visited now
5631
  set_postvisited(n);
5632
  return pre_order;
5633
}
5634

5635
#ifdef ASSERT
5636
//--------------------------verify_regions_in_irreducible_loops----------------
5637
// Iterate down from Root through CFG, verify for every region:
5638
// if it is in an irreducible loop it must be marked as such
5639
void PhaseIdealLoop::verify_regions_in_irreducible_loops() {
5640
  ResourceMark rm;
5641
  if (!_has_irreducible_loops) {
5642
    // last build_loop_tree has not found any irreducible loops
5643
    // hence no region has to be marked is_in_irreduible_loop
5644
    return;
5645
  }
5646

5647
  RootNode* root = C->root();
5648
  Unique_Node_List worklist; // visit all nodes once
5649
  worklist.push(root);
5650
  bool failure = false;
5651
  for (uint i = 0; i < worklist.size(); i++) {
5652
    Node* n = worklist.at(i);
5653
    if (n->is_Region()) {
5654
      RegionNode* region = n->as_Region();
5655
      if (is_in_irreducible_loop(region) &&
5656
          region->loop_status() == RegionNode::LoopStatus::Reducible) {
5657
        failure = true;
5658
        tty->print("irreducible! ");
5659
        region->dump();
5660
      }
5661
    }
5662
    for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
5663
      Node* use = n->fast_out(j);
5664
      if (use->is_CFG()) {
5665
        worklist.push(use); // push if was not pushed before
5666
      }
5667
    }
5668
  }
5669
  assert(!failure, "region in irreducible loop was marked as reducible");
5670
}
5671

5672
//---------------------------is_in_irreducible_loop-------------------------
5673
// Analogous to ciTypeFlow::Block::is_in_irreducible_loop
5674
bool PhaseIdealLoop::is_in_irreducible_loop(RegionNode* region) {
5675
  if (!_has_irreducible_loops) {
5676
    return false; // no irreducible loop in graph
5677
  }
5678
  IdealLoopTree* l = get_loop(region); // l: innermost loop that contains region
5679
  do {
5680
    if (l->_irreducible) {
5681
      return true; // found it
5682
    }
5683
    if (l == _ltree_root) {
5684
      return false; // reached root, terimnate
5685
    }
5686
    l = l->_parent;
5687
  } while (l != nullptr);
5688
  assert(region->is_in_infinite_subgraph(), "must be in infinite subgraph");
5689
  // We have "l->_parent == nullptr", which happens only for infinite loops,
5690
  // where no parent is attached to the loop. We did not find any irreducible
5691
  // loop from this block out to lp. Thus lp only has one entry, and no exit
5692
  // (it is infinite and reducible). We can always rewrite an infinite loop
5693
  // that is nested inside other loops:
5694
  // while(condition) { infinite_loop; }
5695
  // with an equivalent program where the infinite loop is an outermost loop
5696
  // that is not nested in any loop:
5697
  // while(condition) { break; } infinite_loop;
5698
  // Thus, we can understand lp as an outermost loop, and can terminate and
5699
  // conclude: this block is in no irreducible loop.
5700
  return false;
5701
}
5702
#endif
5703

5704
//------------------------------build_loop_early-------------------------------
5705
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
5706
// First pass computes the earliest controlling node possible.  This is the
5707
// controlling input with the deepest dominating depth.
5708
void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
5709
  while (worklist.size() != 0) {
5710
    // Use local variables nstack_top_n & nstack_top_i to cache values
5711
    // on nstack's top.
5712
    Node *nstack_top_n = worklist.pop();
5713
    uint  nstack_top_i = 0;
5714
//while_nstack_nonempty:
5715
    while (true) {
5716
      // Get parent node and next input's index from stack's top.
5717
      Node  *n = nstack_top_n;
5718
      uint   i = nstack_top_i;
5719
      uint cnt = n->req(); // Count of inputs
5720
      if (i == 0) {        // Pre-process the node.
5721
        if( has_node(n) &&            // Have either loop or control already?
5722
            !has_ctrl(n) ) {          // Have loop picked out already?
5723
          // During "merge_many_backedges" we fold up several nested loops
5724
          // into a single loop.  This makes the members of the original
5725
          // loop bodies pointing to dead loops; they need to move up
5726
          // to the new UNION'd larger loop.  I set the _head field of these
5727
          // dead loops to null and the _parent field points to the owning
5728
          // loop.  Shades of UNION-FIND algorithm.
5729
          IdealLoopTree *ilt;
5730
          while( !(ilt = get_loop(n))->_head ) {
5731
            // Normally I would use a set_loop here.  But in this one special
5732
            // case, it is legal (and expected) to change what loop a Node
5733
            // belongs to.
5734
            _loop_or_ctrl.map(n->_idx, (Node*)(ilt->_parent));
5735
          }
5736
          // Remove safepoints ONLY if I've already seen I don't need one.
5737
          // (the old code here would yank a 2nd safepoint after seeing a
5738
          // first one, even though the 1st did not dominate in the loop body
5739
          // and thus could be avoided indefinitely)
5740
          if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
5741
              is_deleteable_safept(n)) {
5742
            Node *in = n->in(TypeFunc::Control);
5743
            lazy_replace(n,in);       // Pull safepoint now
5744
            if (ilt->_safepts != nullptr) {
5745
              ilt->_safepts->yank(n);
5746
            }
5747
            // Carry on with the recursion "as if" we are walking
5748
            // only the control input
5749
            if( !visited.test_set( in->_idx ) ) {
5750
              worklist.push(in);      // Visit this guy later, using worklist
5751
            }
5752
            // Get next node from nstack:
5753
            // - skip n's inputs processing by setting i > cnt;
5754
            // - we also will not call set_early_ctrl(n) since
5755
            //   has_node(n) == true (see the condition above).
5756
            i = cnt + 1;
5757
          }
5758
        }
5759
      } // if (i == 0)
5760

5761
      // Visit all inputs
5762
      bool done = true;       // Assume all n's inputs will be processed
5763
      while (i < cnt) {
5764
        Node *in = n->in(i);
5765
        ++i;
5766
        if (in == nullptr) continue;
5767
        if (in->pinned() && !in->is_CFG())
5768
          set_ctrl(in, in->in(0));
5769
        int is_visited = visited.test_set( in->_idx );
5770
        if (!has_node(in)) {  // No controlling input yet?
5771
          assert( !in->is_CFG(), "CFG Node with no controlling input?" );
5772
          assert( !is_visited, "visit only once" );
5773
          nstack.push(n, i);  // Save parent node and next input's index.
5774
          nstack_top_n = in;  // Process current input now.
5775
          nstack_top_i = 0;
5776
          done = false;       // Not all n's inputs processed.
5777
          break; // continue while_nstack_nonempty;
5778
        } else if (!is_visited) {
5779
          // This guy has a location picked out for him, but has not yet
5780
          // been visited.  Happens to all CFG nodes, for instance.
5781
          // Visit him using the worklist instead of recursion, to break
5782
          // cycles.  Since he has a location already we do not need to
5783
          // find his location before proceeding with the current Node.
5784
          worklist.push(in);  // Visit this guy later, using worklist
5785
        }
5786
      }
5787
      if (done) {
5788
        // All of n's inputs have been processed, complete post-processing.
5789

5790
        // Compute earliest point this Node can go.
5791
        // CFG, Phi, pinned nodes already know their controlling input.
5792
        if (!has_node(n)) {
5793
          // Record earliest legal location
5794
          set_early_ctrl(n, false);
5795
        }
5796
        if (nstack.is_empty()) {
5797
          // Finished all nodes on stack.
5798
          // Process next node on the worklist.
5799
          break;
5800
        }
5801
        // Get saved parent node and next input's index.
5802
        nstack_top_n = nstack.node();
5803
        nstack_top_i = nstack.index();
5804
        nstack.pop();
5805
      }
5806
    } // while (true)
5807
  }
5808
}
5809

5810
//------------------------------dom_lca_internal--------------------------------
5811
// Pair-wise LCA
5812
Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
5813
  if( !n1 ) return n2;          // Handle null original LCA
5814
  assert( n1->is_CFG(), "" );
5815
  assert( n2->is_CFG(), "" );
5816
  // find LCA of all uses
5817
  uint d1 = dom_depth(n1);
5818
  uint d2 = dom_depth(n2);
5819
  while (n1 != n2) {
5820
    if (d1 > d2) {
5821
      n1 =      idom(n1);
5822
      d1 = dom_depth(n1);
5823
    } else if (d1 < d2) {
5824
      n2 =      idom(n2);
5825
      d2 = dom_depth(n2);
5826
    } else {
5827
      // Here d1 == d2.  Due to edits of the dominator-tree, sections
5828
      // of the tree might have the same depth.  These sections have
5829
      // to be searched more carefully.
5830

5831
      // Scan up all the n1's with equal depth, looking for n2.
5832
      Node *t1 = idom(n1);
5833
      while (dom_depth(t1) == d1) {
5834
        if (t1 == n2)  return n2;
5835
        t1 = idom(t1);
5836
      }
5837
      // Scan up all the n2's with equal depth, looking for n1.
5838
      Node *t2 = idom(n2);
5839
      while (dom_depth(t2) == d2) {
5840
        if (t2 == n1)  return n1;
5841
        t2 = idom(t2);
5842
      }
5843
      // Move up to a new dominator-depth value as well as up the dom-tree.
5844
      n1 = t1;
5845
      n2 = t2;
5846
      d1 = dom_depth(n1);
5847
      d2 = dom_depth(n2);
5848
    }
5849
  }
5850
  return n1;
5851
}
5852

5853
//------------------------------compute_idom-----------------------------------
5854
// Locally compute IDOM using dom_lca call.  Correct only if the incoming
5855
// IDOMs are correct.
5856
Node *PhaseIdealLoop::compute_idom( Node *region ) const {
5857
  assert( region->is_Region(), "" );
5858
  Node *LCA = nullptr;
5859
  for( uint i = 1; i < region->req(); i++ ) {
5860
    if( region->in(i) != C->top() )
5861
      LCA = dom_lca( LCA, region->in(i) );
5862
  }
5863
  return LCA;
5864
}
5865

5866
bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
5867
  bool had_error = false;
5868
#ifdef ASSERT
5869
  if (early != C->root()) {
5870
    // Make sure that there's a dominance path from LCA to early
5871
    Node* d = LCA;
5872
    while (d != early) {
5873
      if (d == C->root()) {
5874
        dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
5875
        tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
5876
        had_error = true;
5877
        break;
5878
      }
5879
      d = idom(d);
5880
    }
5881
  }
5882
#endif
5883
  return had_error;
5884
}
5885

5886

5887
Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
5888
  // Compute LCA over list of uses
5889
  bool had_error = false;
5890
  Node *LCA = nullptr;
5891
  for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
5892
    Node* c = n->fast_out(i);
5893
    if (_loop_or_ctrl[c->_idx] == nullptr)
5894
      continue;                 // Skip the occasional dead node
5895
    if( c->is_Phi() ) {         // For Phis, we must land above on the path
5896
      for( uint j=1; j<c->req(); j++ ) {// For all inputs
5897
        if( c->in(j) == n ) {   // Found matching input?
5898
          Node *use = c->in(0)->in(j);
5899
          if (_verify_only && use->is_top()) continue;
5900
          LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
5901
          if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
5902
        }
5903
      }
5904
    } else {
5905
      // For CFG data-users, use is in the block just prior
5906
      Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
5907
      LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
5908
      if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
5909
    }
5910
  }
5911
  assert(!had_error, "bad dominance");
5912
  return LCA;
5913
}
5914

5915
// Check the shape of the graph at the loop entry. In some cases,
5916
// the shape of the graph does not match the shape outlined below.
5917
// That is caused by the Opaque1 node "protecting" the shape of
5918
// the graph being removed by, for example, the IGVN performed
5919
// in PhaseIdealLoop::build_and_optimize().
5920
//
5921
// After the Opaque1 node has been removed, optimizations (e.g., split-if,
5922
// loop unswitching, and IGVN, or a combination of them) can freely change
5923
// the graph's shape. As a result, the graph shape outlined below cannot
5924
// be guaranteed anymore.
5925
Node* CountedLoopNode::is_canonical_loop_entry() {
5926
  if (!is_main_loop() && !is_post_loop()) {
5927
    return nullptr;
5928
  }
5929
  Node* ctrl = skip_assertion_predicates_with_halt();
5930

5931
  if (ctrl == nullptr || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
5932
    return nullptr;
5933
  }
5934
  Node* iffm = ctrl->in(0);
5935
  if (iffm == nullptr || iffm->Opcode() != Op_If) {
5936
    return nullptr;
5937
  }
5938
  Node* bolzm = iffm->in(1);
5939
  if (bolzm == nullptr || !bolzm->is_Bool()) {
5940
    return nullptr;
5941
  }
5942
  Node* cmpzm = bolzm->in(1);
5943
  if (cmpzm == nullptr || !cmpzm->is_Cmp()) {
5944
    return nullptr;
5945
  }
5946

5947
  uint input = is_main_loop() ? 2 : 1;
5948
  if (input >= cmpzm->req() || cmpzm->in(input) == nullptr) {
5949
    return nullptr;
5950
  }
5951
  bool res = cmpzm->in(input)->Opcode() == Op_OpaqueZeroTripGuard;
5952
#ifdef ASSERT
5953
  bool found_opaque = false;
5954
  for (uint i = 1; i < cmpzm->req(); i++) {
5955
    Node* opnd = cmpzm->in(i);
5956
    if (opnd && opnd->is_Opaque1()) {
5957
      found_opaque = true;
5958
      break;
5959
    }
5960
  }
5961
  assert(found_opaque == res, "wrong pattern");
5962
#endif
5963
  return res ? cmpzm->in(input) : nullptr;
5964
}
5965

5966
// Find pre loop end from main loop. Returns nullptr if none.
5967
CountedLoopEndNode* CountedLoopNode::find_pre_loop_end() {
5968
  assert(is_main_loop(), "Can only find pre-loop from main-loop");
5969
  // The loop cannot be optimized if the graph shape at the loop entry is
5970
  // inappropriate.
5971
  if (is_canonical_loop_entry() == nullptr) {
5972
    return nullptr;
5973
  }
5974

5975
  Node* p_f = skip_assertion_predicates_with_halt()->in(0)->in(0);
5976
  if (!p_f->is_IfFalse() || !p_f->in(0)->is_CountedLoopEnd()) {
5977
    return nullptr;
5978
  }
5979
  CountedLoopEndNode* pre_end = p_f->in(0)->as_CountedLoopEnd();
5980
  CountedLoopNode* loop_node = pre_end->loopnode();
5981
  if (loop_node == nullptr || !loop_node->is_pre_loop()) {
5982
    return nullptr;
5983
  }
5984
  return pre_end;
5985
}
5986

5987
//------------------------------get_late_ctrl----------------------------------
5988
// Compute latest legal control.
5989
Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
5990
  assert(early != nullptr, "early control should not be null");
5991

5992
  Node* LCA = compute_lca_of_uses(n, early);
5993
#ifdef ASSERT
5994
  if (LCA == C->root() && LCA != early) {
5995
    // def doesn't dominate uses so print some useful debugging output
5996
    compute_lca_of_uses(n, early, true);
5997
  }
5998
#endif
5999

6000
  if (n->is_Load() && LCA != early) {
6001
    LCA = get_late_ctrl_with_anti_dep(n->as_Load(), early, LCA);
6002
  }
6003

6004
  assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
6005
  return LCA;
6006
}
6007

6008
// if this is a load, check for anti-dependent stores
6009
// We use a conservative algorithm to identify potential interfering
6010
// instructions and for rescheduling the load.  The users of the memory
6011
// input of this load are examined.  Any use which is not a load and is
6012
// dominated by early is considered a potentially interfering store.
6013
// This can produce false positives.
6014
Node* PhaseIdealLoop::get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA) {
6015
  int load_alias_idx = C->get_alias_index(n->adr_type());
6016
  if (C->alias_type(load_alias_idx)->is_rewritable()) {
6017
    Unique_Node_List worklist;
6018

6019
    Node* mem = n->in(MemNode::Memory);
6020
    for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
6021
      Node* s = mem->fast_out(i);
6022
      worklist.push(s);
6023
    }
6024
    for (uint i = 0; i < worklist.size() && LCA != early; i++) {
6025
      Node* s = worklist.at(i);
6026
      if (s->is_Load() || s->Opcode() == Op_SafePoint ||
6027
          (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0) ||
6028
          s->is_Phi()) {
6029
        continue;
6030
      } else if (s->is_MergeMem()) {
6031
        for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
6032
          Node* s1 = s->fast_out(i);
6033
          worklist.push(s1);
6034
        }
6035
      } else {
6036
        Node* sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
6037
        assert(sctrl != nullptr || !s->is_reachable_from_root(), "must have control");
6038
        if (sctrl != nullptr && !sctrl->is_top() && is_dominator(early, sctrl)) {
6039
          const TypePtr* adr_type = s->adr_type();
6040
          if (s->is_ArrayCopy()) {
6041
            // Copy to known instance needs destination type to test for aliasing
6042
            const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
6043
            if (dest_type != TypeOopPtr::BOTTOM) {
6044
              adr_type = dest_type;
6045
            }
6046
          }
6047
          if (C->can_alias(adr_type, load_alias_idx)) {
6048
            LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
6049
          } else if (s->is_CFG() && s->is_Multi()) {
6050
            // Look for the memory use of s (that is the use of its memory projection)
6051
            for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
6052
              Node* s1 = s->fast_out(i);
6053
              assert(s1->is_Proj(), "projection expected");
6054
              if (_igvn.type(s1) == Type::MEMORY) {
6055
                for (DUIterator_Fast jmax, j = s1->fast_outs(jmax); j < jmax; j++) {
6056
                  Node* s2 = s1->fast_out(j);
6057
                  worklist.push(s2);
6058
                }
6059
              }
6060
            }
6061
          }
6062
        }
6063
      }
6064
    }
6065
    // For Phis only consider Region's inputs that were reached by following the memory edges
6066
    if (LCA != early) {
6067
      for (uint i = 0; i < worklist.size(); i++) {
6068
        Node* s = worklist.at(i);
6069
        if (s->is_Phi() && C->can_alias(s->adr_type(), load_alias_idx)) {
6070
          Node* r = s->in(0);
6071
          for (uint j = 1; j < s->req(); j++) {
6072
            Node* in = s->in(j);
6073
            Node* r_in = r->in(j);
6074
            // We can't reach any node from a Phi because we don't enqueue Phi's uses above
6075
            if (((worklist.member(in) && !in->is_Phi()) || in == mem) && is_dominator(early, r_in)) {
6076
              LCA = dom_lca_for_get_late_ctrl(LCA, r_in, n);
6077
            }
6078
          }
6079
        }
6080
      }
6081
    }
6082
  }
6083
  return LCA;
6084
}
6085

6086
// Is CFG node 'dominator' dominating node 'n'?
6087
bool PhaseIdealLoop::is_dominator(Node* dominator, Node* n) {
6088
  if (dominator == n) {
6089
    return true;
6090
  }
6091
  assert(dominator->is_CFG() && n->is_CFG(), "must have CFG nodes");
6092
  uint dd = dom_depth(dominator);
6093
  while (dom_depth(n) >= dd) {
6094
    if (n == dominator) {
6095
      return true;
6096
    }
6097
    n = idom(n);
6098
  }
6099
  return false;
6100
}
6101

6102
// Is CFG node 'dominator' strictly dominating node 'n'?
6103
bool PhaseIdealLoop::is_strict_dominator(Node* dominator, Node* n) {
6104
  return dominator != n && is_dominator(dominator, n);
6105
}
6106

6107
//------------------------------dom_lca_for_get_late_ctrl_internal-------------
6108
// Pair-wise LCA with tags.
6109
// Tag each index with the node 'tag' currently being processed
6110
// before advancing up the dominator chain using idom().
6111
// Later calls that find a match to 'tag' know that this path has already
6112
// been considered in the current LCA (which is input 'n1' by convention).
6113
// Since get_late_ctrl() is only called once for each node, the tag array
6114
// does not need to be cleared between calls to get_late_ctrl().
6115
// Algorithm trades a larger constant factor for better asymptotic behavior
6116
//
6117
Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal(Node *n1, Node *n2, Node *tag_node) {
6118
  uint d1 = dom_depth(n1);
6119
  uint d2 = dom_depth(n2);
6120
  jlong tag = tag_node->_idx | (((jlong)_dom_lca_tags_round) << 32);
6121

6122
  do {
6123
    if (d1 > d2) {
6124
      // current lca is deeper than n2
6125
      _dom_lca_tags.at_put_grow(n1->_idx, tag);
6126
      n1 =      idom(n1);
6127
      d1 = dom_depth(n1);
6128
    } else if (d1 < d2) {
6129
      // n2 is deeper than current lca
6130
      jlong memo = _dom_lca_tags.at_grow(n2->_idx, 0);
6131
      if (memo == tag) {
6132
        return n1;    // Return the current LCA
6133
      }
6134
      _dom_lca_tags.at_put_grow(n2->_idx, tag);
6135
      n2 =      idom(n2);
6136
      d2 = dom_depth(n2);
6137
    } else {
6138
      // Here d1 == d2.  Due to edits of the dominator-tree, sections
6139
      // of the tree might have the same depth.  These sections have
6140
      // to be searched more carefully.
6141

6142
      // Scan up all the n1's with equal depth, looking for n2.
6143
      _dom_lca_tags.at_put_grow(n1->_idx, tag);
6144
      Node *t1 = idom(n1);
6145
      while (dom_depth(t1) == d1) {
6146
        if (t1 == n2)  return n2;
6147
        _dom_lca_tags.at_put_grow(t1->_idx, tag);
6148
        t1 = idom(t1);
6149
      }
6150
      // Scan up all the n2's with equal depth, looking for n1.
6151
      _dom_lca_tags.at_put_grow(n2->_idx, tag);
6152
      Node *t2 = idom(n2);
6153
      while (dom_depth(t2) == d2) {
6154
        if (t2 == n1)  return n1;
6155
        _dom_lca_tags.at_put_grow(t2->_idx, tag);
6156
        t2 = idom(t2);
6157
      }
6158
      // Move up to a new dominator-depth value as well as up the dom-tree.
6159
      n1 = t1;
6160
      n2 = t2;
6161
      d1 = dom_depth(n1);
6162
      d2 = dom_depth(n2);
6163
    }
6164
  } while (n1 != n2);
6165
  return n1;
6166
}
6167

6168
//------------------------------init_dom_lca_tags------------------------------
6169
// Tag could be a node's integer index, 32bits instead of 64bits in some cases
6170
// Intended use does not involve any growth for the array, so it could
6171
// be of fixed size.
6172
void PhaseIdealLoop::init_dom_lca_tags() {
6173
  uint limit = C->unique() + 1;
6174
  _dom_lca_tags.at_grow(limit, 0);
6175
  _dom_lca_tags_round = 0;
6176
#ifdef ASSERT
6177
  for (uint i = 0; i < limit; ++i) {
6178
    assert(_dom_lca_tags.at(i) == 0, "Must be distinct from each node pointer");
6179
  }
6180
#endif // ASSERT
6181
}
6182

6183
//------------------------------build_loop_late--------------------------------
6184
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
6185
// Second pass finds latest legal placement, and ideal loop placement.
6186
void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
6187
  while (worklist.size() != 0) {
6188
    Node *n = worklist.pop();
6189
    // Only visit once
6190
    if (visited.test_set(n->_idx)) continue;
6191
    uint cnt = n->outcnt();
6192
    uint   i = 0;
6193
    while (true) {
6194
      assert(_loop_or_ctrl[n->_idx], "no dead nodes");
6195
      // Visit all children
6196
      if (i < cnt) {
6197
        Node* use = n->raw_out(i);
6198
        ++i;
6199
        // Check for dead uses.  Aggressively prune such junk.  It might be
6200
        // dead in the global sense, but still have local uses so I cannot
6201
        // easily call 'remove_dead_node'.
6202
        if (_loop_or_ctrl[use->_idx] != nullptr || use->is_top()) { // Not dead?
6203
          // Due to cycles, we might not hit the same fixed point in the verify
6204
          // pass as we do in the regular pass.  Instead, visit such phis as
6205
          // simple uses of the loop head.
6206
          if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
6207
            if( !visited.test(use->_idx) )
6208
              worklist.push(use);
6209
          } else if( !visited.test_set(use->_idx) ) {
6210
            nstack.push(n, i); // Save parent and next use's index.
6211
            n   = use;         // Process all children of current use.
6212
            cnt = use->outcnt();
6213
            i   = 0;
6214
          }
6215
        } else {
6216
          // Do not visit around the backedge of loops via data edges.
6217
          // push dead code onto a worklist
6218
          _deadlist.push(use);
6219
        }
6220
      } else {
6221
        // All of n's children have been processed, complete post-processing.
6222
        build_loop_late_post(n);
6223
        if (C->failing()) { return; }
6224
        if (nstack.is_empty()) {
6225
          // Finished all nodes on stack.
6226
          // Process next node on the worklist.
6227
          break;
6228
        }
6229
        // Get saved parent node and next use's index. Visit the rest of uses.
6230
        n   = nstack.node();
6231
        cnt = n->outcnt();
6232
        i   = nstack.index();
6233
        nstack.pop();
6234
      }
6235
    }
6236
  }
6237
}
6238

6239
// Verify that no data node is scheduled in the outer loop of a strip
6240
// mined loop.
6241
void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
6242
#ifdef ASSERT
6243
  if (get_loop(least)->_nest == 0) {
6244
    return;
6245
  }
6246
  IdealLoopTree* loop = get_loop(least);
6247
  Node* head = loop->_head;
6248
  if (head->is_OuterStripMinedLoop() &&
6249
      // Verification can't be applied to fully built strip mined loops
6250
      head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
6251
    Node* sfpt = head->as_Loop()->outer_safepoint();
6252
    ResourceMark rm;
6253
    Unique_Node_List wq;
6254
    wq.push(sfpt);
6255
    for (uint i = 0; i < wq.size(); i++) {
6256
      Node *m = wq.at(i);
6257
      for (uint i = 1; i < m->req(); i++) {
6258
        Node* nn = m->in(i);
6259
        if (nn == n) {
6260
          return;
6261
        }
6262
        if (nn != nullptr && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
6263
          wq.push(nn);
6264
        }
6265
      }
6266
    }
6267
    ShouldNotReachHere();
6268
  }
6269
#endif
6270
}
6271

6272

6273
//------------------------------build_loop_late_post---------------------------
6274
// Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
6275
// Second pass finds latest legal placement, and ideal loop placement.
6276
void PhaseIdealLoop::build_loop_late_post(Node *n) {
6277
  build_loop_late_post_work(n, true);
6278
}
6279

6280
void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
6281

6282
  if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
6283
    _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
6284
  }
6285

6286
#ifdef ASSERT
6287
  if (_verify_only && !n->is_CFG()) {
6288
    // Check def-use domination.
6289
    compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
6290
  }
6291
#endif
6292

6293
  // CFG and pinned nodes already handled
6294
  if( n->in(0) ) {
6295
    if( n->in(0)->is_top() ) return; // Dead?
6296

6297
    // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
6298
    // _must_ be pinned (they have to observe their control edge of course).
6299
    // Unlike Stores (which modify an unallocable resource, the memory
6300
    // state), Mods/Loads can float around.  So free them up.
6301
    switch( n->Opcode() ) {
6302
    case Op_DivI:
6303
    case Op_DivF:
6304
    case Op_DivD:
6305
    case Op_ModI:
6306
    case Op_ModF:
6307
    case Op_ModD:
6308
    case Op_LoadB:              // Same with Loads; they can sink
6309
    case Op_LoadUB:             // during loop optimizations.
6310
    case Op_LoadUS:
6311
    case Op_LoadD:
6312
    case Op_LoadF:
6313
    case Op_LoadI:
6314
    case Op_LoadKlass:
6315
    case Op_LoadNKlass:
6316
    case Op_LoadL:
6317
    case Op_LoadS:
6318
    case Op_LoadP:
6319
    case Op_LoadN:
6320
    case Op_LoadRange:
6321
    case Op_LoadD_unaligned:
6322
    case Op_LoadL_unaligned:
6323
    case Op_StrComp:            // Does a bunch of load-like effects
6324
    case Op_StrEquals:
6325
    case Op_StrIndexOf:
6326
    case Op_StrIndexOfChar:
6327
    case Op_AryEq:
6328
    case Op_VectorizedHashCode:
6329
    case Op_CountPositives:
6330
      pinned = false;
6331
    }
6332
    if (n->is_CMove() || n->is_ConstraintCast()) {
6333
      pinned = false;
6334
    }
6335
    if( pinned ) {
6336
      IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
6337
      if( !chosen_loop->_child )       // Inner loop?
6338
        chosen_loop->_body.push(n); // Collect inner loops
6339
      return;
6340
    }
6341
  } else {                      // No slot zero
6342
    if( n->is_CFG() ) {         // CFG with no slot 0 is dead
6343
      _loop_or_ctrl.map(n->_idx,nullptr); // No block setting, it's globally dead
6344
      return;
6345
    }
6346
    assert(!n->is_CFG() || n->outcnt() == 0, "");
6347
  }
6348

6349
  // Do I have a "safe range" I can select over?
6350
  Node *early = get_ctrl(n);// Early location already computed
6351

6352
  // Compute latest point this Node can go
6353
  Node *LCA = get_late_ctrl( n, early );
6354
  // LCA is null due to uses being dead
6355
  if( LCA == nullptr ) {
6356
#ifdef ASSERT
6357
    for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
6358
      assert(_loop_or_ctrl[n->out(i1)->_idx] == nullptr, "all uses must also be dead");
6359
    }
6360
#endif
6361
    _loop_or_ctrl.map(n->_idx, nullptr); // This node is useless
6362
    _deadlist.push(n);
6363
    return;
6364
  }
6365
  assert(LCA != nullptr && !LCA->is_top(), "no dead nodes");
6366

6367
  Node *legal = LCA;            // Walk 'legal' up the IDOM chain
6368
  Node *least = legal;          // Best legal position so far
6369
  while( early != legal ) {     // While not at earliest legal
6370
    if (legal->is_Start() && !early->is_Root()) {
6371
#ifdef ASSERT
6372
      // Bad graph. Print idom path and fail.
6373
      dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
6374
      assert(false, "Bad graph detected in build_loop_late");
6375
#endif
6376
      C->record_method_not_compilable("Bad graph detected in build_loop_late");
6377
      return;
6378
    }
6379
    // Find least loop nesting depth
6380
    legal = idom(legal);        // Bump up the IDOM tree
6381
    // Check for lower nesting depth
6382
    if( get_loop(legal)->_nest < get_loop(least)->_nest )
6383
      least = legal;
6384
  }
6385
  assert(early == legal || legal != C->root(), "bad dominance of inputs");
6386

6387
  if (least != early) {
6388
    // Move the node above predicates as far up as possible so a
6389
    // following pass of Loop Predication doesn't hoist a predicate
6390
    // that depends on it above that node.
6391
    PredicateEntryIterator predicate_iterator(least);
6392
    while (predicate_iterator.has_next()) {
6393
      Node* next_predicate_entry = predicate_iterator.next_entry();
6394
      if (is_strict_dominator(next_predicate_entry, early)) {
6395
        break;
6396
      }
6397
      least = next_predicate_entry;
6398
    }
6399
  }
6400
  // Try not to place code on a loop entry projection
6401
  // which can inhibit range check elimination.
6402
  if (least != early && !BarrierSet::barrier_set()->barrier_set_c2()->is_gc_specific_loop_opts_pass(_mode)) {
6403
    Node* ctrl_out = least->unique_ctrl_out_or_null();
6404
    if (ctrl_out != nullptr && ctrl_out->is_Loop() &&
6405
        least == ctrl_out->in(LoopNode::EntryControl) &&
6406
        (ctrl_out->is_CountedLoop() || ctrl_out->is_OuterStripMinedLoop())) {
6407
      Node* least_dom = idom(least);
6408
      if (get_loop(least_dom)->is_member(get_loop(least))) {
6409
        least = least_dom;
6410
      }
6411
    }
6412
  }
6413
  // Don't extend live ranges of raw oops
6414
  if (least != early && n->is_ConstraintCast() && n->in(1)->bottom_type()->isa_rawptr() &&
6415
      !n->bottom_type()->isa_rawptr()) {
6416
    least = early;
6417
  }
6418

6419
#ifdef ASSERT
6420
  // Broken part of VerifyLoopOptimizations (F)
6421
  // Reason:
6422
  //   _verify_me->get_ctrl_no_update(n) seems to return wrong result
6423
  /*
6424
  // If verifying, verify that 'verify_me' has a legal location
6425
  // and choose it as our location.
6426
  if( _verify_me ) {
6427
    Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
6428
    Node *legal = LCA;
6429
    while( early != legal ) {   // While not at earliest legal
6430
      if( legal == v_ctrl ) break;  // Check for prior good location
6431
      legal = idom(legal)      ;// Bump up the IDOM tree
6432
    }
6433
    // Check for prior good location
6434
    if( legal == v_ctrl ) least = legal; // Keep prior if found
6435
  }
6436
  */
6437
#endif
6438

6439
  // Assign discovered "here or above" point
6440
  least = find_non_split_ctrl(least);
6441
  verify_strip_mined_scheduling(n, least);
6442
  set_ctrl(n, least);
6443

6444
  // Collect inner loop bodies
6445
  IdealLoopTree *chosen_loop = get_loop(least);
6446
  if( !chosen_loop->_child )   // Inner loop?
6447
    chosen_loop->_body.push(n);// Collect inner loops
6448

6449
  if (!_verify_only && n->Opcode() == Op_OpaqueZeroTripGuard) {
6450
    _zero_trip_guard_opaque_nodes.push(n);
6451
  }
6452

6453
}
6454

6455
#ifdef ASSERT
6456
void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
6457
  tty->print_cr("%s", msg);
6458
  tty->print("n: "); n->dump();
6459
  tty->print("early(n): "); early->dump();
6460
  if (n->in(0) != nullptr  && !n->in(0)->is_top() &&
6461
      n->in(0) != early && !n->in(0)->is_Root()) {
6462
    tty->print("n->in(0): "); n->in(0)->dump();
6463
  }
6464
  for (uint i = 1; i < n->req(); i++) {
6465
    Node* in1 = n->in(i);
6466
    if (in1 != nullptr && in1 != n && !in1->is_top()) {
6467
      tty->print("n->in(%d): ", i); in1->dump();
6468
      Node* in1_early = get_ctrl(in1);
6469
      tty->print("early(n->in(%d)): ", i); in1_early->dump();
6470
      if (in1->in(0) != nullptr     && !in1->in(0)->is_top() &&
6471
          in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
6472
        tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
6473
      }
6474
      for (uint j = 1; j < in1->req(); j++) {
6475
        Node* in2 = in1->in(j);
6476
        if (in2 != nullptr && in2 != n && in2 != in1 && !in2->is_top()) {
6477
          tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
6478
          Node* in2_early = get_ctrl(in2);
6479
          tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
6480
          if (in2->in(0) != nullptr     && !in2->in(0)->is_top() &&
6481
              in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
6482
            tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
6483
          }
6484
        }
6485
      }
6486
    }
6487
  }
6488
  tty->cr();
6489
  tty->print("LCA(n): "); LCA->dump();
6490
  for (uint i = 0; i < n->outcnt(); i++) {
6491
    Node* u1 = n->raw_out(i);
6492
    if (u1 == n)
6493
      continue;
6494
    tty->print("n->out(%d): ", i); u1->dump();
6495
    if (u1->is_CFG()) {
6496
      for (uint j = 0; j < u1->outcnt(); j++) {
6497
        Node* u2 = u1->raw_out(j);
6498
        if (u2 != u1 && u2 != n && u2->is_CFG()) {
6499
          tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
6500
        }
6501
      }
6502
    } else {
6503
      Node* u1_later = get_ctrl(u1);
6504
      tty->print("later(n->out(%d)): ", i); u1_later->dump();
6505
      if (u1->in(0) != nullptr     && !u1->in(0)->is_top() &&
6506
          u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
6507
        tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
6508
      }
6509
      for (uint j = 0; j < u1->outcnt(); j++) {
6510
        Node* u2 = u1->raw_out(j);
6511
        if (u2 == n || u2 == u1)
6512
          continue;
6513
        tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
6514
        if (!u2->is_CFG()) {
6515
          Node* u2_later = get_ctrl(u2);
6516
          tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
6517
          if (u2->in(0) != nullptr     && !u2->in(0)->is_top() &&
6518
              u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
6519
            tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
6520
          }
6521
        }
6522
      }
6523
    }
6524
  }
6525
  dump_idoms(early, LCA);
6526
  tty->cr();
6527
}
6528

6529
// Class to compute the real LCA given an early node and a wrong LCA in a bad graph.
6530
class RealLCA {
6531
  const PhaseIdealLoop* _phase;
6532
  Node* _early;
6533
  Node* _wrong_lca;
6534
  uint _early_index;
6535
  int _wrong_lca_index;
6536

6537
  // Given idom chains of early and wrong LCA: Walk through idoms starting at StartNode and find the first node which
6538
  // is different: Return the previously visited node which must be the real LCA.
6539
  // The node lists also contain _early and _wrong_lca, respectively.
6540
  Node* find_real_lca(Unique_Node_List& early_with_idoms, Unique_Node_List& wrong_lca_with_idoms) {
6541
    int early_index = early_with_idoms.size() - 1;
6542
    int wrong_lca_index = wrong_lca_with_idoms.size() - 1;
6543
    bool found_difference = false;
6544
    do {
6545
      if (early_with_idoms[early_index] != wrong_lca_with_idoms[wrong_lca_index]) {
6546
        // First time early and wrong LCA idoms differ. Real LCA must be at the previous index.
6547
        found_difference = true;
6548
        break;
6549
      }
6550
      early_index--;
6551
      wrong_lca_index--;
6552
    } while (wrong_lca_index >= 0);
6553

6554
    assert(early_index >= 0, "must always find an LCA - cannot be early");
6555
    _early_index = early_index;
6556
    _wrong_lca_index = wrong_lca_index;
6557
    Node* real_lca = early_with_idoms[_early_index + 1]; // Plus one to skip _early.
6558
    assert(found_difference || real_lca == _wrong_lca, "wrong LCA dominates early and is therefore the real LCA");
6559
    return real_lca;
6560
  }
6561

6562
  void dump(Node* real_lca) {
6563
    tty->cr();
6564
    tty->print_cr("idoms of early \"%d %s\":", _early->_idx, _early->Name());
6565
    _phase->dump_idom(_early, _early_index + 1);
6566

6567
    tty->cr();
6568
    tty->print_cr("idoms of (wrong) LCA \"%d %s\":", _wrong_lca->_idx, _wrong_lca->Name());
6569
    _phase->dump_idom(_wrong_lca, _wrong_lca_index + 1);
6570

6571
    tty->cr();
6572
    tty->print("Real LCA of early \"%d %s\" (idom[%d]) and wrong LCA \"%d %s\"",
6573
               _early->_idx, _early->Name(), _early_index, _wrong_lca->_idx, _wrong_lca->Name());
6574
    if (_wrong_lca_index >= 0) {
6575
      tty->print(" (idom[%d])", _wrong_lca_index);
6576
    }
6577
    tty->print_cr(":");
6578
    real_lca->dump();
6579
  }
6580

6581
 public:
6582
  RealLCA(const PhaseIdealLoop* phase, Node* early, Node* wrong_lca)
6583
      : _phase(phase), _early(early), _wrong_lca(wrong_lca), _early_index(0), _wrong_lca_index(0) {
6584
    assert(!wrong_lca->is_Start(), "StartNode is always a common dominator");
6585
  }
6586

6587
  void compute_and_dump() {
6588
    ResourceMark rm;
6589
    Unique_Node_List early_with_idoms;
6590
    Unique_Node_List wrong_lca_with_idoms;
6591
    early_with_idoms.push(_early);
6592
    wrong_lca_with_idoms.push(_wrong_lca);
6593
    _phase->get_idoms(_early, 10000, early_with_idoms);
6594
    _phase->get_idoms(_wrong_lca, 10000, wrong_lca_with_idoms);
6595
    Node* real_lca = find_real_lca(early_with_idoms, wrong_lca_with_idoms);
6596
    dump(real_lca);
6597
  }
6598
};
6599

6600
// Dump the idom chain of early, of the wrong LCA and dump the real LCA of early and wrong LCA.
6601
void PhaseIdealLoop::dump_idoms(Node* early, Node* wrong_lca) {
6602
  assert(!is_dominator(early, wrong_lca), "sanity check that early does not dominate wrong lca");
6603
  assert(!has_ctrl(early) && !has_ctrl(wrong_lca), "sanity check, no data nodes");
6604

6605
  RealLCA real_lca(this, early, wrong_lca);
6606
  real_lca.compute_and_dump();
6607
}
6608
#endif // ASSERT
6609

6610
#ifndef PRODUCT
6611
//------------------------------dump-------------------------------------------
6612
void PhaseIdealLoop::dump() const {
6613
  ResourceMark rm;
6614
  Node_Stack stack(C->live_nodes() >> 2);
6615
  Node_List rpo_list;
6616
  VectorSet visited;
6617
  visited.set(C->top()->_idx);
6618
  rpo(C->root(), stack, visited, rpo_list);
6619
  // Dump root loop indexed by last element in PO order
6620
  dump(_ltree_root, rpo_list.size(), rpo_list);
6621
}
6622

6623
void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
6624
  loop->dump_head();
6625

6626
  // Now scan for CFG nodes in the same loop
6627
  for (uint j = idx; j > 0; j--) {
6628
    Node* n = rpo_list[j-1];
6629
    if (!_loop_or_ctrl[n->_idx])      // Skip dead nodes
6630
      continue;
6631

6632
    if (get_loop(n) != loop) { // Wrong loop nest
6633
      if (get_loop(n)->_head == n &&    // Found nested loop?
6634
          get_loop(n)->_parent == loop)
6635
        dump(get_loop(n), rpo_list.size(), rpo_list);     // Print it nested-ly
6636
      continue;
6637
    }
6638

6639
    // Dump controlling node
6640
    tty->sp(2 * loop->_nest);
6641
    tty->print("C");
6642
    if (n == C->root()) {
6643
      n->dump();
6644
    } else {
6645
      Node* cached_idom   = idom_no_update(n);
6646
      Node* computed_idom = n->in(0);
6647
      if (n->is_Region()) {
6648
        computed_idom = compute_idom(n);
6649
        // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
6650
        // any MultiBranch ctrl node), so apply a similar transform to
6651
        // the cached idom returned from idom_no_update.
6652
        cached_idom = find_non_split_ctrl(cached_idom);
6653
      }
6654
      tty->print(" ID:%d", computed_idom->_idx);
6655
      n->dump();
6656
      if (cached_idom != computed_idom) {
6657
        tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
6658
                      computed_idom->_idx, cached_idom->_idx);
6659
      }
6660
    }
6661
    // Dump nodes it controls
6662
    for (uint k = 0; k < _loop_or_ctrl.max(); k++) {
6663
      // (k < C->unique() && get_ctrl(find(k)) == n)
6664
      if (k < C->unique() && _loop_or_ctrl[k] == (Node*)((intptr_t)n + 1)) {
6665
        Node* m = C->root()->find(k);
6666
        if (m && m->outcnt() > 0) {
6667
          if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
6668
            tty->print_cr("*** BROKEN CTRL ACCESSOR!  _loop_or_ctrl[k] is %p, ctrl is %p",
6669
                          _loop_or_ctrl[k], has_ctrl(m) ? get_ctrl_no_update(m) : nullptr);
6670
          }
6671
          tty->sp(2 * loop->_nest + 1);
6672
          m->dump();
6673
        }
6674
      }
6675
    }
6676
  }
6677
}
6678

6679
void PhaseIdealLoop::dump_idom(Node* n, const uint count) const {
6680
  if (has_ctrl(n)) {
6681
    tty->print_cr("No idom for data nodes");
6682
  } else {
6683
    ResourceMark rm;
6684
    Unique_Node_List idoms;
6685
    get_idoms(n, count, idoms);
6686
    dump_idoms_in_reverse(n, idoms);
6687
  }
6688
}
6689

6690
void PhaseIdealLoop::get_idoms(Node* n, const uint count, Unique_Node_List& idoms) const {
6691
  Node* next = n;
6692
  for (uint i = 0; !next->is_Start() && i < count; i++) {
6693
    next = idom(next);
6694
    assert(!idoms.member(next), "duplicated idom is not possible");
6695
    idoms.push(next);
6696
  }
6697
}
6698

6699
void PhaseIdealLoop::dump_idoms_in_reverse(const Node* n, const Node_List& idom_list) const {
6700
  Node* next;
6701
  uint padding = 3;
6702
  uint node_index_padding_width = static_cast<int>(log10(static_cast<double>(C->unique()))) + 1;
6703
  for (int i = idom_list.size() - 1; i >= 0; i--) {
6704
    if (i == 9 || i == 99) {
6705
      padding++;
6706
    }
6707
    next = idom_list[i];
6708
    tty->print_cr("idom[%d]:%*c%*d  %s", i, padding, ' ', node_index_padding_width, next->_idx, next->Name());
6709
  }
6710
  tty->print_cr("n:      %*c%*d  %s", padding, ' ', node_index_padding_width, n->_idx, n->Name());
6711
}
6712
#endif // NOT PRODUCT
6713

6714
// Collect a R-P-O for the whole CFG.
6715
// Result list is in post-order (scan backwards for RPO)
6716
void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
6717
  stk.push(start, 0);
6718
  visited.set(start->_idx);
6719

6720
  while (stk.is_nonempty()) {
6721
    Node* m   = stk.node();
6722
    uint  idx = stk.index();
6723
    if (idx < m->outcnt()) {
6724
      stk.set_index(idx + 1);
6725
      Node* n = m->raw_out(idx);
6726
      if (n->is_CFG() && !visited.test_set(n->_idx)) {
6727
        stk.push(n, 0);
6728
      }
6729
    } else {
6730
      rpo_list.push(m);
6731
      stk.pop();
6732
    }
6733
  }
6734
}
6735

6736

6737
//=============================================================================
6738
//------------------------------LoopTreeIterator-------------------------------
6739

6740
// Advance to next loop tree using a preorder, left-to-right traversal.
6741
void LoopTreeIterator::next() {
6742
  assert(!done(), "must not be done.");
6743
  if (_curnt->_child != nullptr) {
6744
    _curnt = _curnt->_child;
6745
  } else if (_curnt->_next != nullptr) {
6746
    _curnt = _curnt->_next;
6747
  } else {
6748
    while (_curnt != _root && _curnt->_next == nullptr) {
6749
      _curnt = _curnt->_parent;
6750
    }
6751
    if (_curnt == _root) {
6752
      _curnt = nullptr;
6753
      assert(done(), "must be done.");
6754
    } else {
6755
      assert(_curnt->_next != nullptr, "must be more to do");
6756
      _curnt = _curnt->_next;
6757
    }
6758
  }
6759
}
6760

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