icBuffer_x86.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#include "precompiled.hpp"
#include "asm/macroAssembler.hpp"
#include "asm/macroAssembler.inline.hpp"
#include "code/icBuffer.hpp"
#include "gc/shared/collectedHeap.inline.hpp"
#include "interpreter/bytecodes.hpp"
#include "memory/resourceArea.hpp"
#include "nativeInst_x86.hpp"
#include "oops/oop.inline.hpp"

int InlineCacheBuffer::ic_stub_code_size() {
  // Worst case, if destination is not a near call:
  // lea rax, lit1
  // lea scratch, lit2
  // jmp scratch

  // Best case
  // lea rax, lit1
  // jmp lit2

  int best = NativeMovConstReg::instruction_size + NativeJump::instruction_size;
  int worst = 2 * NativeMovConstReg::instruction_size + 3;
  return MAX2(best, worst);
}



void InlineCacheBuffer::assemble_ic_buffer_code(address code_begin, void* cached_value, address entry_point) {
  ResourceMark rm;
  CodeBuffer      code(code_begin, ic_stub_code_size());
  MacroAssembler* masm            = new MacroAssembler(&code);
  // note: even though the code contains an embedded value, we do not need reloc info
  // because
  // (1) the value is old (i.e., doesn't matter for scavenges)
  // (2) these ICStubs are removed *before* a GC happens, so the roots disappear
  // assert(cached_value == NULL || cached_oop->is_perm(), "must be perm oop");
  masm->lea(rax, AddressLiteral((address) cached_value, relocInfo::metadata_type));
  masm->jump(ExternalAddress(entry_point));
}


address InlineCacheBuffer::ic_buffer_entry_point(address code_begin) {
  NativeMovConstReg* move = nativeMovConstReg_at(code_begin);   // creation also verifies the object
  address jmp = move->next_instruction_address();
  NativeInstruction* ni = nativeInstruction_at(jmp);
  if (ni->is_jump()) {
    NativeJump*        jump = nativeJump_at(jmp);
    return jump->jump_destination();
  } else {
    assert(ni->is_far_jump(), "unexpected instruction");
    NativeFarJump*     jump = nativeFarJump_at(jmp);
    return jump->jump_destination();
  }
}


void* InlineCacheBuffer::ic_buffer_cached_value(address code_begin) {
  // creation also verifies the object
  NativeMovConstReg* move = nativeMovConstReg_at(code_begin);
  // Verifies the jump
  address jmp = move->next_instruction_address();
  NativeInstruction* ni = nativeInstruction_at(jmp);
  if (ni->is_jump()) {
    NativeJump*        jump = nativeJump_at(jmp);
  } else {
    assert(ni->is_far_jump(), "unexpected instruction");
    NativeFarJump*     jump = nativeFarJump_at(jmp);
  }
  void* o = (void*)move->data();
  return o;
}