jdk

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/*
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 * Copyright (c) 1997, 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 "interpreter/bytecodeStream.hpp"
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#include "interpreter/oopMapCache.hpp"
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#include "logging/log.hpp"
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#include "logging/logStream.hpp"
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#include "memory/allocation.inline.hpp"
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#include "memory/resourceArea.hpp"
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#include "oops/generateOopMap.hpp"
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#include "oops/oop.inline.hpp"
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#include "runtime/atomic.hpp"
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#include "runtime/handles.inline.hpp"
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#include "runtime/safepoint.hpp"
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#include "runtime/signature.hpp"
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#include "utilities/globalCounter.inline.hpp"
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class OopMapCacheEntry: private InterpreterOopMap {
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  friend class InterpreterOopMap;
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  friend class OopMapForCacheEntry;
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  friend class OopMapCache;
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  friend class VerifyClosure;
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 private:
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  OopMapCacheEntry* _next;
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 protected:
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  // Initialization
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  void fill(const methodHandle& method, int bci);
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  // fills the bit mask for native calls
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  void fill_for_native(const methodHandle& method);
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  void set_mask(CellTypeState* vars, CellTypeState* stack, int stack_top);
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  // Deallocate bit masks and initialize fields
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  void flush();
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  static void deallocate(OopMapCacheEntry* const entry);
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 private:
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  void allocate_bit_mask();   // allocates the bit mask on C heap f necessary
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  void deallocate_bit_mask(); // allocates the bit mask on C heap f necessary
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  bool verify_mask(CellTypeState *vars, CellTypeState *stack, int max_locals, int stack_top);
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 public:
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  OopMapCacheEntry() : InterpreterOopMap() {
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    _next = nullptr;
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  }
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};
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// Implementation of OopMapForCacheEntry
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// (subclass of GenerateOopMap, initializes an OopMapCacheEntry for a given method and bci)
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class OopMapForCacheEntry: public GenerateOopMap {
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  OopMapCacheEntry *_entry;
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  int               _bci;
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  int               _stack_top;
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  virtual bool report_results() const     { return false; }
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  virtual bool possible_gc_point          (BytecodeStream *bcs);
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  virtual void fill_stackmap_prolog       (int nof_gc_points);
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  virtual void fill_stackmap_epilog       ();
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  virtual void fill_stackmap_for_opcodes  (BytecodeStream *bcs,
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                                           CellTypeState* vars,
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                                           CellTypeState* stack,
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                                           int stack_top);
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  virtual void fill_init_vars             (GrowableArray<intptr_t> *init_vars);
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 public:
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  OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry *entry);
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  // Computes stack map for (method,bci) and initialize entry
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  bool compute_map(Thread* current);
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  int  size();
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};
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OopMapForCacheEntry::OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry* entry) : GenerateOopMap(method) {
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  _bci       = bci;
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  _entry     = entry;
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  _stack_top = -1;
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}
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bool OopMapForCacheEntry::compute_map(Thread* current) {
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  assert(!method()->is_native(), "cannot compute oop map for native methods");
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  // First check if it is a method where the stackmap is always empty
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  if (method()->code_size() == 0 || method()->max_locals() + method()->max_stack() == 0) {
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    _entry->set_mask_size(0);
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  } else {
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    ResourceMark rm;
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    if (!GenerateOopMap::compute_map(current)) {
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      fatal("Unrecoverable verification or out-of-memory error");
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      return false;
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    }
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    result_for_basicblock(_bci);
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  }
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  return true;
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}
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bool OopMapForCacheEntry::possible_gc_point(BytecodeStream *bcs) {
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  return false; // We are not reporting any result. We call result_for_basicblock directly
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}
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void OopMapForCacheEntry::fill_stackmap_prolog(int nof_gc_points) {
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  // Do nothing
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}
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void OopMapForCacheEntry::fill_stackmap_epilog() {
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  // Do nothing
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}
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void OopMapForCacheEntry::fill_init_vars(GrowableArray<intptr_t> *init_vars) {
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  // Do nothing
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}
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void OopMapForCacheEntry::fill_stackmap_for_opcodes(BytecodeStream *bcs,
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                                                    CellTypeState* vars,
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                                                    CellTypeState* stack,
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                                                    int stack_top) {
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  // Only interested in one specific bci
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  if (bcs->bci() == _bci) {
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    _entry->set_mask(vars, stack, stack_top);
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    _stack_top = stack_top;
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  }
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}
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int OopMapForCacheEntry::size() {
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  assert(_stack_top != -1, "compute_map must be called first");
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  return ((method()->is_static()) ? 0 : 1) + method()->max_locals() + _stack_top;
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}
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// Implementation of InterpreterOopMap and OopMapCacheEntry
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class VerifyClosure : public OffsetClosure {
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 private:
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  OopMapCacheEntry* _entry;
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  bool              _failed;
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 public:
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  VerifyClosure(OopMapCacheEntry* entry)         { _entry = entry; _failed = false; }
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  void offset_do(int offset)                     { if (!_entry->is_oop(offset)) _failed = true; }
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  bool failed() const                            { return _failed; }
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};
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InterpreterOopMap::InterpreterOopMap() {
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  initialize();
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}
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InterpreterOopMap::~InterpreterOopMap() {
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  if (has_valid_mask() && mask_size() > small_mask_limit) {
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    assert(_bit_mask[0] != 0, "should have pointer to C heap");
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    FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
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  }
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}
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bool InterpreterOopMap::is_empty() const {
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  bool result = _method == nullptr;
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  assert(_method != nullptr || (_bci == 0 &&
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    (_mask_size == 0 || _mask_size == USHRT_MAX) &&
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    _bit_mask[0] == 0), "Should be completely empty");
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  return result;
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}
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void InterpreterOopMap::initialize() {
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  _method    = nullptr;
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  _mask_size = USHRT_MAX;  // This value should cause a failure quickly
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  _bci       = 0;
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  _expression_stack_size = 0;
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  _num_oops  = 0;
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  for (int i = 0; i < N; i++) _bit_mask[i] = 0;
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}
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void InterpreterOopMap::iterate_oop(OffsetClosure* oop_closure) const {
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  int n = number_of_entries();
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  int word_index = 0;
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  uintptr_t value = 0;
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  uintptr_t mask = 0;
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  // iterate over entries
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  for (int i = 0; i < n; i++, mask <<= bits_per_entry) {
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    // get current word
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    if (mask == 0) {
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      value = bit_mask()[word_index++];
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      mask = 1;
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    }
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    // test for oop
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    if ((value & (mask << oop_bit_number)) != 0) oop_closure->offset_do(i);
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  }
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}
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void InterpreterOopMap::print() const {
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  int n = number_of_entries();
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  tty->print("oop map for ");
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  method()->print_value();
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  tty->print(" @ %d = [%d] { ", bci(), n);
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  for (int i = 0; i < n; i++) {
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    if (is_dead(i)) tty->print("%d+ ", i);
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    else
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    if (is_oop(i)) tty->print("%d ", i);
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  }
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  tty->print_cr("}");
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}
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class MaskFillerForNative: public NativeSignatureIterator {
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 private:
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  uintptr_t * _mask;                             // the bit mask to be filled
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  int         _size;                             // the mask size in bits
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  void set_one(int i) {
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    i *= InterpreterOopMap::bits_per_entry;
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    assert(0 <= i && i < _size, "offset out of bounds");
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    _mask[i / BitsPerWord] |= (((uintptr_t) 1 << InterpreterOopMap::oop_bit_number) << (i % BitsPerWord));
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  }
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 public:
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  void pass_byte()                               { /* ignore */ }
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  void pass_short()                              { /* ignore */ }
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  void pass_int()                                { /* ignore */ }
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  void pass_long()                               { /* ignore */ }
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  void pass_float()                              { /* ignore */ }
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  void pass_double()                             { /* ignore */ }
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  void pass_object()                             { set_one(offset()); }
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  MaskFillerForNative(const methodHandle& method, uintptr_t* mask, int size) : NativeSignatureIterator(method) {
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    _mask   = mask;
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    _size   = size;
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    // initialize with 0
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    int i = (size + BitsPerWord - 1) / BitsPerWord;
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    while (i-- > 0) _mask[i] = 0;
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  }
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  void generate() {
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    iterate();
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  }
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};
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bool OopMapCacheEntry::verify_mask(CellTypeState* vars, CellTypeState* stack, int max_locals, int stack_top) {
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  // Check mask includes map
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  VerifyClosure blk(this);
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  iterate_oop(&blk);
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  if (blk.failed()) return false;
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  // Check if map is generated correctly
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  // (Use ?: operator to make sure all 'true' & 'false' are represented exactly the same so we can use == afterwards)
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  const bool log = log_is_enabled(Trace, interpreter, oopmap);
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  LogStream st(Log(interpreter, oopmap)::trace());
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  if (log) st.print("Locals (%d): ", max_locals);
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  for(int i = 0; i < max_locals; i++) {
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    bool v1 = is_oop(i)               ? true : false;
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    bool v2 = vars[i].is_reference()  ? true : false;
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    assert(v1 == v2, "locals oop mask generation error");
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    if (log) st.print("%d", v1 ? 1 : 0);
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  }
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  if (log) st.cr();
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  if (log) st.print("Stack (%d): ", stack_top);
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  for(int j = 0; j < stack_top; j++) {
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    bool v1 = is_oop(max_locals + j)  ? true : false;
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    bool v2 = stack[j].is_reference() ? true : false;
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    assert(v1 == v2, "stack oop mask generation error");
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    if (log) st.print("%d", v1 ? 1 : 0);
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  }
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  if (log) st.cr();
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  return true;
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}
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void OopMapCacheEntry::allocate_bit_mask() {
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  if (mask_size() > small_mask_limit) {
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    assert(_bit_mask[0] == 0, "bit mask should be new or just flushed");
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    _bit_mask[0] = (intptr_t)
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      NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
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  }
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}
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void OopMapCacheEntry::deallocate_bit_mask() {
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  if (mask_size() > small_mask_limit && _bit_mask[0] != 0) {
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    assert(!Thread::current()->resource_area()->contains((void*)_bit_mask[0]),
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      "This bit mask should not be in the resource area");
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    FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
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    debug_only(_bit_mask[0] = 0;)
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  }
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}
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314

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void OopMapCacheEntry::fill_for_native(const methodHandle& mh) {
316
  assert(mh->is_native(), "method must be native method");
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  set_mask_size(mh->size_of_parameters() * bits_per_entry);
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  allocate_bit_mask();
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  // fill mask for parameters
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  MaskFillerForNative mf(mh, bit_mask(), mask_size());
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  mf.generate();
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}
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void OopMapCacheEntry::fill(const methodHandle& method, int bci) {
326
  // Flush entry to deallocate an existing entry
327
  flush();
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  set_method(method());
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  set_bci(checked_cast<unsigned short>(bci));  // bci is always u2
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  if (method->is_native()) {
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    // Native method activations have oops only among the parameters and one
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    // extra oop following the parameters (the mirror for static native methods).
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    fill_for_native(method);
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  } else {
335
    OopMapForCacheEntry gen(method, bci, this);
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    if (!gen.compute_map(Thread::current())) {
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      fatal("Unrecoverable verification or out-of-memory error");
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    }
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  }
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}
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342

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void OopMapCacheEntry::set_mask(CellTypeState *vars, CellTypeState *stack, int stack_top) {
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  // compute bit mask size
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  int max_locals = method()->max_locals();
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  int n_entries = max_locals + stack_top;
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  set_mask_size(n_entries * bits_per_entry);
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  allocate_bit_mask();
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  set_expression_stack_size(stack_top);
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  // compute bits
352
  int word_index = 0;
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  uintptr_t value = 0;
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  uintptr_t mask = 1;
355

356
  _num_oops = 0;
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  CellTypeState* cell = vars;
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  for (int entry_index = 0; entry_index < n_entries; entry_index++, mask <<= bits_per_entry, cell++) {
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    // store last word
360
    if (mask == 0) {
361
      bit_mask()[word_index++] = value;
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      value = 0;
363
      mask = 1;
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    }
365

366
    // switch to stack when done with locals
367
    if (entry_index == max_locals) {
368
      cell = stack;
369
    }
370

371
    // set oop bit
372
    if ( cell->is_reference()) {
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      value |= (mask << oop_bit_number );
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      _num_oops++;
375
    }
376

377
    // set dead bit
378
    if (!cell->is_live()) {
379
      value |= (mask << dead_bit_number);
380
      assert(!cell->is_reference(), "dead value marked as oop");
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    }
382
  }
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384
  // make sure last word is stored
385
  bit_mask()[word_index] = value;
386

387
  // verify bit mask
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  assert(verify_mask(vars, stack, max_locals, stack_top), "mask could not be verified");
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}
390

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void OopMapCacheEntry::flush() {
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  deallocate_bit_mask();
393
  initialize();
394
}
395

396
void OopMapCacheEntry::deallocate(OopMapCacheEntry* const entry) {
397
  entry->flush();
398
  FREE_C_HEAP_OBJ(entry);
399
}
400

401
// Implementation of OopMapCache
402

403
void InterpreterOopMap::copy_from(const OopMapCacheEntry* src) {
404
  // The expectation is that this InterpreterOopMap is recently created
405
  // and empty. It is used to get a copy of a cached entry.
406
  assert(!has_valid_mask(), "InterpreterOopMap object can only be filled once");
407
  assert(src->has_valid_mask(), "Cannot copy entry with an invalid mask");
408

409
  set_method(src->method());
410
  set_bci(src->bci());
411
  set_mask_size(src->mask_size());
412
  set_expression_stack_size(src->expression_stack_size());
413
  _num_oops = src->num_oops();
414

415
  // Is the bit mask contained in the entry?
416
  if (src->mask_size() <= small_mask_limit) {
417
    memcpy(_bit_mask, src->_bit_mask, mask_word_size() * BytesPerWord);
418
  } else {
419
    _bit_mask[0] = (uintptr_t) NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
420
    memcpy((void*) _bit_mask[0], (void*) src->_bit_mask[0], mask_word_size() * BytesPerWord);
421
  }
422
}
423

424
inline unsigned int OopMapCache::hash_value_for(const methodHandle& method, int bci) const {
425
  // We use method->code_size() rather than method->identity_hash() below since
426
  // the mark may not be present if a pointer to the method is already reversed.
427
  return   ((unsigned int) bci)
428
         ^ ((unsigned int) method->max_locals()         << 2)
429
         ^ ((unsigned int) method->code_size()          << 4)
430
         ^ ((unsigned int) method->size_of_parameters() << 6);
431
}
432

433
OopMapCacheEntry* volatile OopMapCache::_old_entries = nullptr;
434

435
OopMapCache::OopMapCache() {
436
  for(int i = 0; i < size; i++) _array[i] = nullptr;
437
}
438

439

440
OopMapCache::~OopMapCache() {
441
  // Deallocate oop maps that are allocated out-of-line
442
  flush();
443
}
444

445
OopMapCacheEntry* OopMapCache::entry_at(int i) const {
446
  return Atomic::load_acquire(&(_array[i % size]));
447
}
448

449
bool OopMapCache::put_at(int i, OopMapCacheEntry* entry, OopMapCacheEntry* old) {
450
  return Atomic::cmpxchg(&_array[i % size], old, entry) == old;
451
}
452

453
void OopMapCache::flush() {
454
  for (int i = 0; i < size; i++) {
455
    OopMapCacheEntry* entry = _array[i];
456
    if (entry != nullptr) {
457
      _array[i] = nullptr;  // no barrier, only called in OopMapCache destructor
458
      OopMapCacheEntry::deallocate(entry);
459
    }
460
  }
461
}
462

463
void OopMapCache::flush_obsolete_entries() {
464
  assert(SafepointSynchronize::is_at_safepoint(), "called by RedefineClasses in a safepoint");
465
  for (int i = 0; i < size; i++) {
466
    OopMapCacheEntry* entry = _array[i];
467
    if (entry != nullptr && !entry->is_empty() && entry->method()->is_old()) {
468
      // Cache entry is occupied by an old redefined method and we don't want
469
      // to pin it down so flush the entry.
470
      if (log_is_enabled(Debug, redefine, class, oopmap)) {
471
        ResourceMark rm;
472
        log_debug(redefine, class, interpreter, oopmap)
473
          ("flush: %s(%s): cached entry @%d",
474
           entry->method()->name()->as_C_string(), entry->method()->signature()->as_C_string(), i);
475
      }
476
      _array[i] = nullptr;
477
      OopMapCacheEntry::deallocate(entry);
478
    }
479
  }
480
}
481

482
// Lookup or compute/cache the entry.
483
void OopMapCache::lookup(const methodHandle& method,
484
                         int bci,
485
                         InterpreterOopMap* entry_for) {
486
  int probe = hash_value_for(method, bci);
487

488
  if (log_is_enabled(Debug, interpreter, oopmap)) {
489
    static int count = 0;
490
    ResourceMark rm;
491
    log_debug(interpreter, oopmap)
492
          ("%d - Computing oopmap at bci %d for %s at hash %d", ++count, bci,
493
           method()->name_and_sig_as_C_string(), probe);
494
  }
495

496
  // Search hashtable for match.
497
  // Need a critical section to avoid race against concurrent reclamation.
498
  {
499
    GlobalCounter::CriticalSection cs(Thread::current());
500
    for (int i = 0; i < probe_depth; i++) {
501
      OopMapCacheEntry *entry = entry_at(probe + i);
502
      if (entry != nullptr && !entry->is_empty() && entry->match(method, bci)) {
503
        entry_for->copy_from(entry);
504
        assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
505
        log_debug(interpreter, oopmap)("- found at hash %d", probe + i);
506
        return;
507
      }
508
    }
509
  }
510

511
  // Entry is not in hashtable.
512
  // Compute entry
513

514
  OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
515
  tmp->initialize();
516
  tmp->fill(method, bci);
517
  entry_for->copy_from(tmp);
518

519
  if (method->should_not_be_cached()) {
520
    // It is either not safe or not a good idea to cache this Method*
521
    // at this time. We give the caller of lookup() a copy of the
522
    // interesting info via parameter entry_for, but we don't add it to
523
    // the cache. See the gory details in Method*.cpp.
524
    OopMapCacheEntry::deallocate(tmp);
525
    return;
526
  }
527

528
  // First search for an empty slot
529
  for (int i = 0; i < probe_depth; i++) {
530
    OopMapCacheEntry* entry = entry_at(probe + i);
531
    if (entry == nullptr) {
532
      if (put_at(probe + i, tmp, nullptr)) {
533
        assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
534
        return;
535
      }
536
    }
537
  }
538

539
  log_debug(interpreter, oopmap)("*** collision in oopmap cache - flushing item ***");
540

541
  // No empty slot (uncommon case). Use (some approximation of a) LRU algorithm
542
  // where the first entry in the collision array is replaced with the new one.
543
  OopMapCacheEntry* old = entry_at(probe + 0);
544
  if (put_at(probe + 0, tmp, old)) {
545
    // Cannot deallocate old entry on the spot: it can still be used by readers
546
    // that got a reference to it before we were able to replace it in the map.
547
    // Instead of synchronizing on GlobalCounter here and incurring heavy thread
548
    // walk, we do this clean up out of band.
549
    enqueue_for_cleanup(old);
550
  } else {
551
    OopMapCacheEntry::deallocate(tmp);
552
  }
553

554
  assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
555
  return;
556
}
557

558
void OopMapCache::enqueue_for_cleanup(OopMapCacheEntry* entry) {
559
  while (true) {
560
    OopMapCacheEntry* head = Atomic::load(&_old_entries);
561
    entry->_next = head;
562
    if (Atomic::cmpxchg(&_old_entries, head, entry) == head) {
563
      // Enqueued successfully.
564
      break;
565
    }
566
  }
567

568
  if (log_is_enabled(Debug, interpreter, oopmap)) {
569
    ResourceMark rm;
570
    log_debug(interpreter, oopmap)("enqueue %s at bci %d for cleanup",
571
                          entry->method()->name_and_sig_as_C_string(), entry->bci());
572
  }
573
}
574

575
bool OopMapCache::has_cleanup_work() {
576
  return Atomic::load(&_old_entries) != nullptr;
577
}
578

579
void OopMapCache::try_trigger_cleanup() {
580
  // See we can take the lock for the notification without blocking.
581
  // This allows triggering the cleanup from GC paths, that can hold
582
  // the service lock for e.g. oop iteration in service thread.
583
  if (has_cleanup_work() && Service_lock->try_lock_without_rank_check()) {
584
    Service_lock->notify_all();
585
    Service_lock->unlock();
586
  }
587
}
588

589
void OopMapCache::cleanup() {
590
  OopMapCacheEntry* entry = Atomic::xchg(&_old_entries, (OopMapCacheEntry*)nullptr);
591
  if (entry == nullptr) {
592
    // No work.
593
    return;
594
  }
595

596
  // About to delete the entries than might still be accessed by other threads
597
  // on lookup path. Need to sync up with them before proceeding.
598
  GlobalCounter::write_synchronize();
599

600
  while (entry != nullptr) {
601
    if (log_is_enabled(Debug, interpreter, oopmap)) {
602
      ResourceMark rm;
603
      log_debug(interpreter, oopmap)("cleanup entry %s at bci %d",
604
                          entry->method()->name_and_sig_as_C_string(), entry->bci());
605
    }
606
    OopMapCacheEntry* next = entry->_next;
607
    OopMapCacheEntry::deallocate(entry);
608
    entry = next;
609
  }
610
}
611

612
void OopMapCache::compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry) {
613
  // Due to the invariants above it's tricky to allocate a temporary OopMapCacheEntry on the stack
614
  OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
615
  tmp->initialize();
616
  tmp->fill(method, bci);
617
  if (tmp->has_valid_mask()) {
618
    entry->copy_from(tmp);
619
  }
620
  OopMapCacheEntry::deallocate(tmp);
621
}
622