jdk

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/*
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 * Copyright (c) 1997, 2023, 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 "asm/codeBuffer.hpp"
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#include "asm/macroAssembler.hpp"
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#include "asm/macroAssembler.inline.hpp"
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#include "gc/shared/collectedHeap.hpp"
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#include "memory/universe.hpp"
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#include "oops/compressedOops.hpp"
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#include "runtime/icache.hpp"
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#include "runtime/javaThread.hpp"
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#include "runtime/os.hpp"
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#include "utilities/checkedCast.hpp"
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// Implementation of AbstractAssembler
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//
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// The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
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// the assembler keeps a copy of the code buffers boundaries & modifies them when
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// emitting bytes rather than using the code buffers accessor functions all the time.
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// The code buffer is updated via set_code_end(...) after emitting a whole instruction.
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AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
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  if (code == nullptr)  return;
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  CodeSection* cs = code->insts();
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  cs->clear_mark();   // new assembler kills old mark
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  if (cs->start() == nullptr)  {
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    vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());
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  }
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  _code_section = cs;
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  _oop_recorder= code->oop_recorder();
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  DEBUG_ONLY( _short_branch_delta = 0; )
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}
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void AbstractAssembler::set_code_section(CodeSection* cs) {
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  assert(cs->outer() == code_section()->outer(), "sanity");
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  assert(cs->is_allocated(), "need to pre-allocate this section");
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  cs->clear_mark();  // new assembly into this section kills old mark
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  _code_section = cs;
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}
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// Inform CodeBuffer that incoming code and relocation will be for stubs
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address AbstractAssembler::start_a_stub(int required_space) {
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  CodeBuffer*  cb = code();
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  CodeSection* cs = cb->stubs();
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  assert(_code_section == cb->insts(), "not in insts?");
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  if (cs->maybe_expand_to_ensure_remaining(required_space)
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      && cb->blob() == nullptr) {
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    return nullptr;
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  }
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  set_code_section(cs);
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  return pc();
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}
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// Inform CodeBuffer that incoming code and relocation will be code
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// Should not be called if start_a_stub() returned null
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void AbstractAssembler::end_a_stub() {
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  assert(_code_section == code()->stubs(), "not in stubs?");
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  set_code_section(code()->insts());
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}
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// Inform CodeBuffer that incoming code and relocation will be for stubs
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address AbstractAssembler::start_a_const(int required_space, int required_align) {
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  CodeBuffer*  cb = code();
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  CodeSection* cs = cb->consts();
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  assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
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  address end = cs->end();
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  int pad = checked_cast<int>(-(intptr_t)end & (required_align-1));
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  if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
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    if (cb->blob() == nullptr)  return nullptr;
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    end = cs->end();  // refresh pointer
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  }
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  if (pad > 0) {
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    while (--pad >= 0) { *end++ = 0; }
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    cs->set_end(end);
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  }
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  set_code_section(cs);
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  return end;
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}
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// Inform CodeBuffer that incoming code and relocation will be code
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// in section cs (insts or stubs).
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void AbstractAssembler::end_a_const(CodeSection* cs) {
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  assert(_code_section == code()->consts(), "not in consts?");
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  set_code_section(cs);
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}
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void AbstractAssembler::flush() {
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  ICache::invalidate_range(addr_at(0), offset());
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}
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void AbstractAssembler::bind(Label& L) {
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  if (L.is_bound()) {
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    // Assembler can bind a label more than once to the same place.
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    guarantee(L.loc() == locator(), "attempt to redefine label");
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    return;
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  }
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  L.bind_loc(locator());
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  L.patch_instructions((MacroAssembler*)this);
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}
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void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
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  // Each code entry causes one stack bang n pages down the stack where n
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  // is configurable by StackShadowPages.  The setting depends on the maximum
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  // depth of VM call stack or native before going back into java code,
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  // since only java code can raise a stack overflow exception using the
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  // stack banging mechanism.  The VM and native code does not detect stack
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  // overflow.
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  // The code in JavaCalls::call() checks that there is at least n pages
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  // available, so all entry code needs to do is bang once for the end of
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  // this shadow zone.
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  // The entry code may need to bang additional pages if the framesize
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  // is greater than a page.
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  const int page_size = (int)os::vm_page_size();
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  int bang_end = (int)StackOverflow::stack_shadow_zone_size();
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  // This is how far the previous frame's stack banging extended.
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  const int bang_end_safe = bang_end;
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  if (frame_size_in_bytes > page_size) {
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    bang_end += frame_size_in_bytes;
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  }
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  int bang_offset = bang_end_safe;
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  while (bang_offset <= bang_end) {
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    // Need at least one stack bang at end of shadow zone.
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    bang_stack_with_offset(bang_offset);
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    bang_offset += page_size;
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  }
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}
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void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {
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  assert(_loc == -1, "Label is unbound");
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  // Don't add patch locations during scratch emit.
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  if (cb->insts()->scratch_emit()) { return; }
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  if (_patch_index < PatchCacheSize) {
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    _patches[_patch_index] = branch_loc;
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#ifdef ASSERT
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    _lines[_patch_index] = line;
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    _files[_patch_index] = file;
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#endif
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  } else {
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    if (_patch_overflow == nullptr) {
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      _patch_overflow = cb->create_patch_overflow();
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    }
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    _patch_overflow->push(branch_loc);
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  }
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  ++_patch_index;
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}
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void Label::patch_instructions(MacroAssembler* masm) {
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  assert(is_bound(), "Label is bound");
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  CodeBuffer* cb = masm->code();
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  int target_sect = CodeBuffer::locator_sect(loc());
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  address target = cb->locator_address(loc());
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  while (_patch_index > 0) {
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    --_patch_index;
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    int branch_loc;
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    int line = 0;
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    const char* file = nullptr;
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    if (_patch_index >= PatchCacheSize) {
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      branch_loc = _patch_overflow->pop();
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    } else {
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      branch_loc = _patches[_patch_index];
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#ifdef ASSERT
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      line = _lines[_patch_index];
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      file = _files[_patch_index];
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#endif
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    }
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    int branch_sect = CodeBuffer::locator_sect(branch_loc);
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    address branch = cb->locator_address(branch_loc);
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    if (branch_sect == CodeBuffer::SECT_CONSTS) {
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      // The thing to patch is a constant word.
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      *(address*)branch = target;
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      continue;
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    }
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    // Push the target offset into the branch instruction.
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    masm->pd_patch_instruction(branch, target, file, line);
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  }
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}
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void AbstractAssembler::block_comment(const char* comment) {
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  if (sect() == CodeBuffer::SECT_INSTS) {
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    code_section()->outer()->block_comment(offset(), comment);
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  }
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}
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const char* AbstractAssembler::code_string(const char* str) {
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  if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
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    return code_section()->outer()->code_string(str);
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  }
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  return nullptr;
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}
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bool MacroAssembler::uses_implicit_null_check(void* address) {
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  // Exception handler checks the nmethod's implicit null checks table
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  // only when this method returns false.
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  uintptr_t addr = reinterpret_cast<uintptr_t>(address);
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  uintptr_t page_size = (uintptr_t)os::vm_page_size();
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#ifdef _LP64
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  if (UseCompressedOops && CompressedOops::base() != nullptr) {
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    // A SEGV can legitimately happen in C2 code at address
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    // (heap_base + offset) if  Matcher::narrow_oop_use_complex_address
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    // is configured to allow narrow oops field loads to be implicitly
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    // null checked
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    uintptr_t start = (uintptr_t)CompressedOops::base();
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    uintptr_t end = start + page_size;
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    if (addr >= start && addr < end) {
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      return true;
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    }
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  }
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#endif
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  return addr < page_size;
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}
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bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
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  // The offset -1 is used (hardcoded) in a number of places in C1 and MacroAssembler
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  // to indicate an unknown offset. For example, TemplateTable::pop_and_check_object(Register r)
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  // calls MacroAssembler::null_check(Register reg, int offset = -1) which gets here
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  // with -1. Another example is GraphBuilder::access_field(...) which uses -1 as placeholder
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  // for offsets to be patched in later. The -1 there means the offset is not yet known
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  // and may lie outside of the zero-trapping page, and thus we need to ensure we're forcing
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  // an explicit null check for -1.
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  // Check if offset is outside of [0, os::vm_page_size()]
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  return offset < 0 || offset >= static_cast<intptr_t>(os::vm_page_size());
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}
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