src/ia32/assembler-ia32.cc

// Copyright (c) 1994-2006 Sun Microsystems Inc.
// All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// - Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// - Redistribution in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the
// distribution.
//
// - Neither the name of Sun Microsystems or the names of contributors may
// be used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.

// The original source code covered by the above license above has been modified
// significantly by Google Inc.
// Copyright 2012 the V8 project authors. All rights reserved.

#include "v8.h"

#if defined(V8_TARGET_ARCH_IA32)

#include "disassembler.h"
#include "macro-assembler.h"
#include "serialize.h"

namespace v8 {
namespace internal {

// -----------------------------------------------------------------------------
// Implementation of CpuFeatures

#ifdef DEBUG
bool CpuFeatures::initialized_ = false;
#endif
uint64_t CpuFeatures::supported_ = 0;
uint64_t CpuFeatures::found_by_runtime_probing_only_ = 0;


ExternalReference ExternalReference::cpu_features() {
  ASSERT(CpuFeatures::initialized_);
  return ExternalReference(&CpuFeatures::supported_);
}


int IntelDoubleRegister::NumAllocatableRegisters() {
  if (CpuFeatures::IsSupported(SSE2)) {
    return XMMRegister::kNumAllocatableRegisters;
  } else {
    return X87TopOfStackRegister::kNumAllocatableRegisters;
  }
}


int IntelDoubleRegister::NumRegisters() {
  if (CpuFeatures::IsSupported(SSE2)) {
    return XMMRegister::kNumRegisters;
  } else {
    return X87TopOfStackRegister::kNumRegisters;
  }
}


const char* IntelDoubleRegister::AllocationIndexToString(int index) {
  if (CpuFeatures::IsSupported(SSE2)) {
    return XMMRegister::AllocationIndexToString(index);
  } else {
    return X87TopOfStackRegister::AllocationIndexToString(index);
  }
}


// The Probe method needs executable memory, so it uses Heap::CreateCode.
// Allocation failure is silent and leads to safe default.
void CpuFeatures::Probe() {
  ASSERT(!initialized_);
  ASSERT(supported_ == 0);
#ifdef DEBUG
  initialized_ = true;
#endif
  if (Serializer::enabled()) {
    supported_ |= OS::CpuFeaturesImpliedByPlatform();
    return;  // No features if we might serialize.
  }

  const int kBufferSize = 4 * KB;
  VirtualMemory* memory = new VirtualMemory(kBufferSize);
  if (!memory->IsReserved()) {
    delete memory;
    return;
  }
  ASSERT(memory->size() >= static_cast<size_t>(kBufferSize));
  if (!memory->Commit(memory->address(), kBufferSize, true/*executable*/)) {
    delete memory;
    return;
  }

  Assembler assm(NULL, memory->address(), kBufferSize);
  Label cpuid, done;
#define __ assm.
  // Save old esp, since we are going to modify the stack.
  __ push(ebp);
  __ pushfd();
  __ push(ecx);
  __ push(ebx);
  __ mov(ebp, esp);

  // If we can modify bit 21 of the EFLAGS register, then CPUID is supported.
  __ pushfd();
  __ pop(eax);
  __ mov(edx, eax);
  __ xor_(eax, 0x200000);  // Flip bit 21.
  __ push(eax);
  __ popfd();
  __ pushfd();
  __ pop(eax);
  __ xor_(eax, edx);  // Different if CPUID is supported.
  __ j(not_zero, &cpuid);

  // CPUID not supported. Clear the supported features in edx:eax.
  __ xor_(eax, eax);
  __ xor_(edx, edx);
  __ jmp(&done);

  // Invoke CPUID with 1 in eax to get feature information in
  // ecx:edx. Temporarily enable CPUID support because we know it's
  // safe here.
  __ bind(&cpuid);
  __ mov(eax, 1);
  supported_ = (1 << CPUID);
  { CpuFeatureScope fscope(&assm, CPUID);
    __ cpuid();
  }
  supported_ = 0;

  // Move the result from ecx:edx to edx:eax and make sure to mark the
  // CPUID feature as supported.
  __ mov(eax, edx);
  __ or_(eax, 1 << CPUID);
  __ mov(edx, ecx);

  // Done.
  __ bind(&done);
  __ mov(esp, ebp);
  __ pop(ebx);
  __ pop(ecx);
  __ popfd();
  __ pop(ebp);
  __ ret(0);
#undef __

  typedef uint64_t (*F0)();
  F0 probe = FUNCTION_CAST<F0>(reinterpret_cast<Address>(memory->address()));
  uint64_t probed_features = probe();
  uint64_t platform_features = OS::CpuFeaturesImpliedByPlatform();
  supported_ = probed_features | platform_features;
  found_by_runtime_probing_only_ = probed_features & ~platform_features;

  delete memory;
}


// -----------------------------------------------------------------------------
// Implementation of Displacement

void Displacement::init(Label* L, Type type) {
  ASSERT(!L->is_bound());
  int next = 0;
  if (L->is_linked()) {
    next = L->pos();
    ASSERT(next > 0);  // Displacements must be at positions > 0
  }
  // Ensure that we _never_ overflow the next field.
  ASSERT(NextField::is_valid(Assembler::kMaximalBufferSize));
  data_ = NextField::encode(next) | TypeField::encode(type);
}


// -----------------------------------------------------------------------------
// Implementation of RelocInfo


const int RelocInfo::kApplyMask =
  RelocInfo::kCodeTargetMask | 1 << RelocInfo::RUNTIME_ENTRY |
    1 << RelocInfo::JS_RETURN | 1 << RelocInfo::INTERNAL_REFERENCE |
    1 << RelocInfo::DEBUG_BREAK_SLOT | 1 << RelocInfo::CODE_AGE_SEQUENCE;


bool RelocInfo::IsCodedSpecially() {
  // The deserializer needs to know whether a pointer is specially coded.  Being
  // specially coded on IA32 means that it is a relative address, as used by
  // branch instructions.  These are also the ones that need changing when a
  // code object moves.
  return (1 << rmode_) & kApplyMask;
}


void RelocInfo::PatchCode(byte* instructions, int instruction_count) {
  // Patch the code at the current address with the supplied instructions.
  for (int i = 0; i < instruction_count; i++) {
    *(pc_ + i) = *(instructions + i);
  }

  // Indicate that code has changed.
  CPU::FlushICache(pc_, instruction_count);
}


// Patch the code at the current PC with a call to the target address.
// Additional guard int3 instructions can be added if required.
void RelocInfo::PatchCodeWithCall(Address target, int guard_bytes) {
  // Call instruction takes up 5 bytes and int3 takes up one byte.
  static const int kCallCodeSize = 5;
  int code_size = kCallCodeSize + guard_bytes;

  // Create a code patcher.
  CodePatcher patcher(pc_, code_size);

  // Add a label for checking the size of the code used for returning.
#ifdef DEBUG
  Label check_codesize;
  patcher.masm()->bind(&check_codesize);
#endif

  // Patch the code.
  patcher.masm()->call(target, RelocInfo::NONE32);

  // Check that the size of the code generated is as expected.
  ASSERT_EQ(kCallCodeSize,
            patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));

  // Add the requested number of int3 instructions after the call.
  ASSERT_GE(guard_bytes, 0);
  for (int i = 0; i < guard_bytes; i++) {
    patcher.masm()->int3();
  }
}


// -----------------------------------------------------------------------------
// Implementation of Operand

Operand::Operand(Register base, int32_t disp, RelocInfo::Mode rmode) {
  // [base + disp/r]
  if (disp == 0 && RelocInfo::IsNone(rmode) && !base.is(ebp)) {
    // [base]
    set_modrm(0, base);
    if (base.is(esp)) set_sib(times_1, esp, base);
  } else if (is_int8(disp) && RelocInfo::IsNone(rmode)) {
    // [base + disp8]
    set_modrm(1, base);
    if (base.is(esp)) set_sib(times_1, esp, base);
    set_disp8(disp);
  } else {
    // [base + disp/r]
    set_modrm(2, base);
    if (base.is(esp)) set_sib(times_1, esp, base);
    set_dispr(disp, rmode);
  }
}


Operand::Operand(Register base,
                 Register index,
                 ScaleFactor scale,
                 int32_t disp,
                 RelocInfo::Mode rmode) {
  ASSERT(!index.is(esp));  // illegal addressing mode
  // [base + index*scale + disp/r]
  if (disp == 0 && RelocInfo::IsNone(rmode) && !base.is(ebp)) {
    // [base + index*scale]
    set_modrm(0, esp);
    set_sib(scale, index, base);
  } else if (is_int8(disp) && RelocInfo::IsNone(rmode)) {
    // [base + index*scale + disp8]
    set_modrm(1, esp);
    set_sib(scale, index, base);
    set_disp8(disp);
  } else {
    // [base + index*scale + disp/r]
    set_modrm(2, esp);
    set_sib(scale, index, base);
    set_dispr(disp, rmode);
  }
}


Operand::Operand(Register index,
                 ScaleFactor scale,
                 int32_t disp,
                 RelocInfo::Mode rmode) {
  ASSERT(!index.is(esp));  // illegal addressing mode
  // [index*scale + disp/r]
  set_modrm(0, esp);
  set_sib(scale, index, ebp);
  set_dispr(disp, rmode);
}


bool Operand::is_reg(Register reg) const {
  return ((buf_[0] & 0xF8) == 0xC0)  // addressing mode is register only.
      && ((buf_[0] & 0x07) == reg.code());  // register codes match.
}


bool Operand::is_reg_only() const {
  return (buf_[0] & 0xF8) == 0xC0;  // Addressing mode is register only.
}


Register Operand::reg() const {
  ASSERT(is_reg_only());
  return Register::from_code(buf_[0] & 0x07);
}


// -----------------------------------------------------------------------------
// Implementation of Assembler.

// Emit a single byte. Must always be inlined.
#define EMIT(x)                                 \
  *pc_++ = (x)


#ifdef GENERATED_CODE_COVERAGE
static void InitCoverageLog();
#endif

Assembler::Assembler(Isolate* isolate, void* buffer, int buffer_size)
    : AssemblerBase(isolate, buffer, buffer_size),
      positions_recorder_(this) {
  // Clear the buffer in debug mode unless it was provided by the
  // caller in which case we can't be sure it's okay to overwrite
  // existing code in it; see CodePatcher::CodePatcher(...).
#ifdef DEBUG
  if (own_buffer_) {
    memset(buffer_, 0xCC, buffer_size_);  // int3
  }
#endif

  reloc_info_writer.Reposition(buffer_ + buffer_size_, pc_);

#ifdef GENERATED_CODE_COVERAGE
  InitCoverageLog();
#endif
}


void Assembler::GetCode(CodeDesc* desc) {
  // Finalize code (at this point overflow() may be true, but the gap ensures
  // that we are still not overlapping instructions and relocation info).
  ASSERT(pc_ <= reloc_info_writer.pos());  // No overlap.
  // Set up code descriptor.
  desc->buffer = buffer_;
  desc->buffer_size = buffer_size_;
  desc->instr_size = pc_offset();
  desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
  desc->origin = this;
}


void Assembler::Align(int m) {
  ASSERT(IsPowerOf2(m));
  int mask = m - 1;
  int addr = pc_offset();
  Nop((m - (addr & mask)) & mask);
}


bool Assembler::IsNop(Address addr) {
  Address a = addr;
  while (*a == 0x66) a++;
  if (*a == 0x90) return true;
  if (a[0] == 0xf && a[1] == 0x1f) return true;
  return false;
}


void Assembler::Nop(int bytes) {
  EnsureSpace ensure_space(this);

  if (!CpuFeatures::IsSupported(SSE2)) {
    // Older CPUs that do not support SSE2 may not support multibyte NOP
    // instructions.
    for (; bytes > 0; bytes--) {
      EMIT(0x90);
    }
    return;
  }

  // Multi byte nops from http://support.amd.com/us/Processor_TechDocs/40546.pdf
  while (bytes > 0) {
    switch (bytes) {
      case 2:
        EMIT(0x66);
      case 1:
        EMIT(0x90);
        return;
      case 3:
        EMIT(0xf);
        EMIT(0x1f);
        EMIT(0);
        return;
      case 4:
        EMIT(0xf);
        EMIT(0x1f);
        EMIT(0x40);
        EMIT(0);
        return;
      case 6:
        EMIT(0x66);
      case 5:
        EMIT(0xf);
        EMIT(0x1f);
        EMIT(0x44);
        EMIT(0);
        EMIT(0);
        return;
      case 7:
        EMIT(0xf);
        EMIT(0x1f);
        EMIT(0x80);
        EMIT(0);
        EMIT(0);
        EMIT(0);
        EMIT(0);
        return;
      default:
      case 11:
        EMIT(0x66);
        bytes--;
      case 10:
        EMIT(0x66);
        bytes--;
      case 9:
        EMIT(0x66);
        bytes--;
      case 8:
        EMIT(0xf);
        EMIT(0x1f);
        EMIT(0x84);
        EMIT(0);
        EMIT(0);
        EMIT(0);
        EMIT(0);
        EMIT(0);
        bytes -= 8;
    }
  }
}


void Assembler::CodeTargetAlign() {
  Align(16);  // Preferred alignment of jump targets on ia32.
}


void Assembler::cpuid() {
  ASSERT(IsEnabled(CPUID));
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xA2);
}


void Assembler::pushad() {
  EnsureSpace ensure_space(this);
  EMIT(0x60);
}


void Assembler::popad() {
  EnsureSpace ensure_space(this);
  EMIT(0x61);
}


void Assembler::pushfd() {
  EnsureSpace ensure_space(this);
  EMIT(0x9C);
}


void Assembler::popfd() {
  EnsureSpace ensure_space(this);
  EMIT(0x9D);
}


void Assembler::push(const Immediate& x) {
  EnsureSpace ensure_space(this);
  if (x.is_int8()) {
    EMIT(0x6a);
    EMIT(x.x_);
  } else {
    EMIT(0x68);
    emit(x);
  }
}


void Assembler::push_imm32(int32_t imm32) {
  EnsureSpace ensure_space(this);
  EMIT(0x68);
  emit(imm32);
}


void Assembler::push(Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x50 | src.code());
}


void Assembler::push(const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0xFF);
  emit_operand(esi, src);
}


void Assembler::pop(Register dst) {
  ASSERT(reloc_info_writer.last_pc() != NULL);
  EnsureSpace ensure_space(this);
  EMIT(0x58 | dst.code());
}


void Assembler::pop(const Operand& dst) {
  EnsureSpace ensure_space(this);
  EMIT(0x8F);
  emit_operand(eax, dst);
}


void Assembler::enter(const Immediate& size) {
  EnsureSpace ensure_space(this);
  EMIT(0xC8);
  emit_w(size);
  EMIT(0);
}


void Assembler::leave() {
  EnsureSpace ensure_space(this);
  EMIT(0xC9);
}


void Assembler::mov_b(Register dst, const Operand& src) {
  CHECK(dst.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x8A);
  emit_operand(dst, src);
}


void Assembler::mov_b(const Operand& dst, int8_t imm8) {
  EnsureSpace ensure_space(this);
  EMIT(0xC6);
  emit_operand(eax, dst);
  EMIT(imm8);
}


void Assembler::mov_b(const Operand& dst, Register src) {
  CHECK(src.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x88);
  emit_operand(src, dst);
}


void Assembler::mov_w(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x8B);
  emit_operand(dst, src);
}


void Assembler::mov_w(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x89);
  emit_operand(src, dst);
}


void Assembler::mov(Register dst, int32_t imm32) {
  EnsureSpace ensure_space(this);
  EMIT(0xB8 | dst.code());
  emit(imm32);
}


void Assembler::mov(Register dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  EMIT(0xB8 | dst.code());
  emit(x);
}


void Assembler::mov(Register dst, Handle<Object> handle) {
  EnsureSpace ensure_space(this);
  EMIT(0xB8 | dst.code());
  emit(handle);
}


void Assembler::mov(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x8B);
  emit_operand(dst, src);
}


void Assembler::mov(Register dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x89);
  EMIT(0xC0 | src.code() << 3 | dst.code());
}


void Assembler::mov(const Operand& dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  EMIT(0xC7);
  emit_operand(eax, dst);
  emit(x);
}


void Assembler::mov(const Operand& dst, Handle<Object> handle) {
  EnsureSpace ensure_space(this);
  EMIT(0xC7);
  emit_operand(eax, dst);
  emit(handle);
}


void Assembler::mov(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x89);
  emit_operand(src, dst);
}


void Assembler::movsx_b(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xBE);
  emit_operand(dst, src);
}


void Assembler::movsx_w(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xBF);
  emit_operand(dst, src);
}


void Assembler::movzx_b(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xB6);
  emit_operand(dst, src);
}


void Assembler::movzx_w(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xB7);
  emit_operand(dst, src);
}


void Assembler::cmov(Condition cc, Register dst, const Operand& src) {
  ASSERT(IsEnabled(CMOV));
  EnsureSpace ensure_space(this);
  // Opcode: 0f 40 + cc /r.
  EMIT(0x0F);
  EMIT(0x40 + cc);
  emit_operand(dst, src);
}


void Assembler::cld() {
  EnsureSpace ensure_space(this);
  EMIT(0xFC);
}


void Assembler::rep_movs() {
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0xA5);
}


void Assembler::rep_stos() {
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0xAB);
}


void Assembler::stos() {
  EnsureSpace ensure_space(this);
  EMIT(0xAB);
}


void Assembler::xchg(Register dst, Register src) {
  EnsureSpace ensure_space(this);
  if (src.is(eax) || dst.is(eax)) {  // Single-byte encoding.
    EMIT(0x90 | (src.is(eax) ? dst.code() : src.code()));
  } else {
    EMIT(0x87);
    EMIT(0xC0 | src.code() << 3 | dst.code());
  }
}


void Assembler::adc(Register dst, int32_t imm32) {
  EnsureSpace ensure_space(this);
  emit_arith(2, Operand(dst), Immediate(imm32));
}


void Assembler::adc(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x13);
  emit_operand(dst, src);
}


void Assembler::add(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x03);
  emit_operand(dst, src);
}


void Assembler::add(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x01);
  emit_operand(src, dst);
}


void Assembler::add(const Operand& dst, const Immediate& x) {
  ASSERT(reloc_info_writer.last_pc() != NULL);
  EnsureSpace ensure_space(this);
  emit_arith(0, dst, x);
}


void Assembler::and_(Register dst, int32_t imm32) {
  and_(dst, Immediate(imm32));
}


void Assembler::and_(Register dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  emit_arith(4, Operand(dst), x);
}


void Assembler::and_(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x23);
  emit_operand(dst, src);
}


void Assembler::and_(const Operand& dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  emit_arith(4, dst, x);
}


void Assembler::and_(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x21);
  emit_operand(src, dst);
}


void Assembler::cmpb(const Operand& op, int8_t imm8) {
  EnsureSpace ensure_space(this);
  if (op.is_reg(eax)) {
    EMIT(0x3C);
  } else {
    EMIT(0x80);
    emit_operand(edi, op);  // edi == 7
  }
  EMIT(imm8);
}


void Assembler::cmpb(const Operand& op, Register reg) {
  CHECK(reg.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x38);
  emit_operand(reg, op);
}


void Assembler::cmpb(Register reg, const Operand& op) {
  CHECK(reg.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x3A);
  emit_operand(reg, op);
}


void Assembler::cmpw(const Operand& op, Immediate imm16) {
  ASSERT(imm16.is_int16());
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x81);
  emit_operand(edi, op);
  emit_w(imm16);
}


void Assembler::cmp(Register reg, int32_t imm32) {
  EnsureSpace ensure_space(this);
  emit_arith(7, Operand(reg), Immediate(imm32));
}


void Assembler::cmp(Register reg, Handle<Object> handle) {
  EnsureSpace ensure_space(this);
  emit_arith(7, Operand(reg), Immediate(handle));
}


void Assembler::cmp(Register reg, const Operand& op) {
  EnsureSpace ensure_space(this);
  EMIT(0x3B);
  emit_operand(reg, op);
}


void Assembler::cmp(const Operand& op, const Immediate& imm) {
  EnsureSpace ensure_space(this);
  emit_arith(7, op, imm);
}


void Assembler::cmp(const Operand& op, Handle<Object> handle) {
  EnsureSpace ensure_space(this);
  emit_arith(7, op, Immediate(handle));
}


void Assembler::cmpb_al(const Operand& op) {
  EnsureSpace ensure_space(this);
  EMIT(0x38);  // CMP r/m8, r8
  emit_operand(eax, op);  // eax has same code as register al.
}


void Assembler::cmpw_ax(const Operand& op) {
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x39);  // CMP r/m16, r16
  emit_operand(eax, op);  // eax has same code as register ax.
}


void Assembler::dec_b(Register dst) {
  CHECK(dst.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0xFE);
  EMIT(0xC8 | dst.code());
}


void Assembler::dec_b(const Operand& dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xFE);
  emit_operand(ecx, dst);
}


void Assembler::dec(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0x48 | dst.code());
}


void Assembler::dec(const Operand& dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xFF);
  emit_operand(ecx, dst);
}


void Assembler::cdq() {
  EnsureSpace ensure_space(this);
  EMIT(0x99);
}


void Assembler::idiv(Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  EMIT(0xF8 | src.code());
}


void Assembler::imul(Register reg) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  EMIT(0xE8 | reg.code());
}


void Assembler::imul(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xAF);
  emit_operand(dst, src);
}


void Assembler::imul(Register dst, Register src, int32_t imm32) {
  EnsureSpace ensure_space(this);
  if (is_int8(imm32)) {
    EMIT(0x6B);
    EMIT(0xC0 | dst.code() << 3 | src.code());
    EMIT(imm32);
  } else {
    EMIT(0x69);
    EMIT(0xC0 | dst.code() << 3 | src.code());
    emit(imm32);
  }
}


void Assembler::inc(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0x40 | dst.code());
}


void Assembler::inc(const Operand& dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xFF);
  emit_operand(eax, dst);
}


void Assembler::lea(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x8D);
  emit_operand(dst, src);
}


void Assembler::mul(Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  EMIT(0xE0 | src.code());
}


void Assembler::neg(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  EMIT(0xD8 | dst.code());
}


void Assembler::not_(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  EMIT(0xD0 | dst.code());
}


void Assembler::or_(Register dst, int32_t imm32) {
  EnsureSpace ensure_space(this);
  emit_arith(1, Operand(dst), Immediate(imm32));
}


void Assembler::or_(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0B);
  emit_operand(dst, src);
}


void Assembler::or_(const Operand& dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  emit_arith(1, dst, x);
}


void Assembler::or_(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x09);
  emit_operand(src, dst);
}


void Assembler::rcl(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xD0 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xD0 | dst.code());
    EMIT(imm8);
  }
}


void Assembler::rcr(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xD8 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xD8 | dst.code());
    EMIT(imm8);
  }
}

void Assembler::ror(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xC8 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xC8 | dst.code());
    EMIT(imm8);
  }
}

void Assembler::ror_cl(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xD3);
  EMIT(0xC8 | dst.code());
}


void Assembler::sar(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xF8 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xF8 | dst.code());
    EMIT(imm8);
  }
}


void Assembler::sar_cl(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xD3);
  EMIT(0xF8 | dst.code());
}


void Assembler::sbb(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x1B);
  emit_operand(dst, src);
}


void Assembler::shld(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xA5);
  emit_operand(dst, src);
}


void Assembler::shl(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xE0 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xE0 | dst.code());
    EMIT(imm8);
  }
}


void Assembler::shl_cl(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xD3);
  EMIT(0xE0 | dst.code());
}


void Assembler::shrd(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xAD);
  emit_operand(dst, src);
}


void Assembler::shr(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint5(imm8));  // illegal shift count
  if (imm8 == 1) {
    EMIT(0xD1);
    EMIT(0xE8 | dst.code());
  } else {
    EMIT(0xC1);
    EMIT(0xE8 | dst.code());
    EMIT(imm8);
  }
}


void Assembler::shr_cl(Register dst) {
  EnsureSpace ensure_space(this);
  EMIT(0xD3);
  EMIT(0xE8 | dst.code());
}


void Assembler::sub(const Operand& dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  emit_arith(5, dst, x);
}


void Assembler::sub(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x2B);
  emit_operand(dst, src);
}


void Assembler::sub(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x29);
  emit_operand(src, dst);
}


void Assembler::test(Register reg, const Immediate& imm) {
  EnsureSpace ensure_space(this);
  // Only use test against byte for registers that have a byte
  // variant: eax, ebx, ecx, and edx.
  if (RelocInfo::IsNone(imm.rmode_) &&
      is_uint8(imm.x_) &&
      reg.is_byte_register()) {
    uint8_t imm8 = imm.x_;
    if (reg.is(eax)) {
      EMIT(0xA8);
      EMIT(imm8);
    } else {
      emit_arith_b(0xF6, 0xC0, reg, imm8);
    }
  } else {
    // This is not using emit_arith because test doesn't support
    // sign-extension of 8-bit operands.
    if (reg.is(eax)) {
      EMIT(0xA9);
    } else {
      EMIT(0xF7);
      EMIT(0xC0 | reg.code());
    }
    emit(imm);
  }
}


void Assembler::test(Register reg, const Operand& op) {
  EnsureSpace ensure_space(this);
  EMIT(0x85);
  emit_operand(reg, op);
}


void Assembler::test_b(Register reg, const Operand& op) {
  CHECK(reg.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x84);
  emit_operand(reg, op);
}


void Assembler::test(const Operand& op, const Immediate& imm) {
  EnsureSpace ensure_space(this);
  EMIT(0xF7);
  emit_operand(eax, op);
  emit(imm);
}


void Assembler::test_b(const Operand& op, uint8_t imm8) {
  if (op.is_reg_only() && !op.reg().is_byte_register()) {
    test(op, Immediate(imm8));
    return;
  }
  EnsureSpace ensure_space(this);
  EMIT(0xF6);
  emit_operand(eax, op);
  EMIT(imm8);
}


void Assembler::xor_(Register dst, int32_t imm32) {
  EnsureSpace ensure_space(this);
  emit_arith(6, Operand(dst), Immediate(imm32));
}


void Assembler::xor_(Register dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  EMIT(0x33);
  emit_operand(dst, src);
}


void Assembler::xor_(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x31);
  emit_operand(src, dst);
}


void Assembler::xor_(const Operand& dst, const Immediate& x) {
  EnsureSpace ensure_space(this);
  emit_arith(6, dst, x);
}


void Assembler::bt(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xA3);
  emit_operand(src, dst);
}


void Assembler::bts(const Operand& dst, Register src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0xAB);
  emit_operand(src, dst);
}


void Assembler::hlt() {
  EnsureSpace ensure_space(this);
  EMIT(0xF4);
}


void Assembler::int3() {
  EnsureSpace ensure_space(this);
  EMIT(0xCC);
}


void Assembler::nop() {
  EnsureSpace ensure_space(this);
  EMIT(0x90);
}


void Assembler::rdtsc() {
  ASSERT(IsEnabled(RDTSC));
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x31);
}


void Assembler::ret(int imm16) {
  EnsureSpace ensure_space(this);
  ASSERT(is_uint16(imm16));
  if (imm16 == 0) {
    EMIT(0xC3);
  } else {
    EMIT(0xC2);
    EMIT(imm16 & 0xFF);
    EMIT((imm16 >> 8) & 0xFF);
  }
}


// Labels refer to positions in the (to be) generated code.
// There are bound, linked, and unused labels.
//
// Bound labels refer to known positions in the already
// generated code. pos() is the position the label refers to.
//
// Linked labels refer to unknown positions in the code
// to be generated; pos() is the position of the 32bit
// Displacement of the last instruction using the label.


void Assembler::print(Label* L) {
  if (L->is_unused()) {
    PrintF("unused label\n");
  } else if (L->is_bound()) {
    PrintF("bound label to %d\n", L->pos());
  } else if (L->is_linked()) {
    Label l = *L;
    PrintF("unbound label");
    while (l.is_linked()) {
      Displacement disp = disp_at(&l);
      PrintF("@ %d ", l.pos());
      disp.print();
      PrintF("\n");
      disp.next(&l);
    }
  } else {
    PrintF("label in inconsistent state (pos = %d)\n", L->pos_);
  }
}


void Assembler::bind_to(Label* L, int pos) {
  EnsureSpace ensure_space(this);
  ASSERT(0 <= pos && pos <= pc_offset());  // must have a valid binding position
  while (L->is_linked()) {
    Displacement disp = disp_at(L);
    int fixup_pos = L->pos();
    if (disp.type() == Displacement::CODE_RELATIVE) {
      // Relative to Code* heap object pointer.
      long_at_put(fixup_pos, pos + Code::kHeaderSize - kHeapObjectTag);
    } else {
      if (disp.type() == Displacement::UNCONDITIONAL_JUMP) {
        ASSERT(byte_at(fixup_pos - 1) == 0xE9);  // jmp expected
      }
      // Relative address, relative to point after address.
      int imm32 = pos - (fixup_pos + sizeof(int32_t));
      long_at_put(fixup_pos, imm32);
    }
    disp.next(L);
  }
  while (L->is_near_linked()) {
    int fixup_pos = L->near_link_pos();
    int offset_to_next =
        static_cast<int>(*reinterpret_cast<int8_t*>(addr_at(fixup_pos)));
    ASSERT(offset_to_next <= 0);
    // Relative address, relative to point after address.
    int disp = pos - fixup_pos - sizeof(int8_t);
    CHECK(0 <= disp && disp <= 127);
    set_byte_at(fixup_pos, disp);
    if (offset_to_next < 0) {
      L->link_to(fixup_pos + offset_to_next, Label::kNear);
    } else {
      L->UnuseNear();
    }
  }
  L->bind_to(pos);
}


void Assembler::bind(Label* L) {
  EnsureSpace ensure_space(this);
  ASSERT(!L->is_bound());  // label can only be bound once
  bind_to(L, pc_offset());
}


void Assembler::call(Label* L) {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  if (L->is_bound()) {
    const int long_size = 5;
    int offs = L->pos() - pc_offset();
    ASSERT(offs <= 0);
    // 1110 1000 #32-bit disp.
    EMIT(0xE8);
    emit(offs - long_size);
  } else {
    // 1110 1000 #32-bit disp.
    EMIT(0xE8);
    emit_disp(L, Displacement::OTHER);
  }
}


void Assembler::call(byte* entry, RelocInfo::Mode rmode) {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  ASSERT(!RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE8);
  if (RelocInfo::IsRuntimeEntry(rmode)) {
    emit(reinterpret_cast<uint32_t>(entry), rmode);
  } else {
    emit(entry - (pc_ + sizeof(int32_t)), rmode);
  }
}


int Assembler::CallSize(const Operand& adr) {
  // Call size is 1 (opcode) + adr.len_ (operand).
  return 1 + adr.len_;
}


void Assembler::call(const Operand& adr) {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  EMIT(0xFF);
  emit_operand(edx, adr);
}


int Assembler::CallSize(Handle<Code> code, RelocInfo::Mode rmode) {
  return 1 /* EMIT */ + sizeof(uint32_t) /* emit */;
}


void Assembler::call(Handle<Code> code,
                     RelocInfo::Mode rmode,
                     TypeFeedbackId ast_id) {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE8);
  emit(code, rmode, ast_id);
}


void Assembler::jmp(Label* L, Label::Distance distance) {
  EnsureSpace ensure_space(this);
  if (L->is_bound()) {
    const int short_size = 2;
    const int long_size  = 5;
    int offs = L->pos() - pc_offset();
    ASSERT(offs <= 0);
    if (is_int8(offs - short_size)) {
      // 1110 1011 #8-bit disp.
      EMIT(0xEB);
      EMIT((offs - short_size) & 0xFF);
    } else {
      // 1110 1001 #32-bit disp.
      EMIT(0xE9);
      emit(offs - long_size);
    }
  } else if (distance == Label::kNear) {
    EMIT(0xEB);
    emit_near_disp(L);
  } else {
    // 1110 1001 #32-bit disp.
    EMIT(0xE9);
    emit_disp(L, Displacement::UNCONDITIONAL_JUMP);
  }
}


void Assembler::jmp(byte* entry, RelocInfo::Mode rmode) {
  EnsureSpace ensure_space(this);
  ASSERT(!RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE9);
  if (RelocInfo::IsRuntimeEntry(rmode)) {
    emit(reinterpret_cast<uint32_t>(entry), rmode);
  } else {
    emit(entry - (pc_ + sizeof(int32_t)), rmode);
  }
}


void Assembler::jmp(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xFF);
  emit_operand(esp, adr);
}


void Assembler::jmp(Handle<Code> code, RelocInfo::Mode rmode) {
  EnsureSpace ensure_space(this);
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE9);
  emit(code, rmode);
}


void Assembler::j(Condition cc, Label* L, Label::Distance distance) {
  EnsureSpace ensure_space(this);
  ASSERT(0 <= cc && static_cast<int>(cc) < 16);
  if (L->is_bound()) {
    const int short_size = 2;
    const int long_size  = 6;
    int offs = L->pos() - pc_offset();
    ASSERT(offs <= 0);
    if (is_int8(offs - short_size)) {
      // 0111 tttn #8-bit disp
      EMIT(0x70 | cc);
      EMIT((offs - short_size) & 0xFF);
    } else {
      // 0000 1111 1000 tttn #32-bit disp
      EMIT(0x0F);
      EMIT(0x80 | cc);
      emit(offs - long_size);
    }
  } else if (distance == Label::kNear) {
    EMIT(0x70 | cc);
    emit_near_disp(L);
  } else {
    // 0000 1111 1000 tttn #32-bit disp
    // Note: could eliminate cond. jumps to this jump if condition
    //       is the same however, seems to be rather unlikely case.
    EMIT(0x0F);
    EMIT(0x80 | cc);
    emit_disp(L, Displacement::OTHER);
  }
}


void Assembler::j(Condition cc, byte* entry, RelocInfo::Mode rmode) {
  EnsureSpace ensure_space(this);
  ASSERT((0 <= cc) && (static_cast<int>(cc) < 16));
  // 0000 1111 1000 tttn #32-bit disp.
  EMIT(0x0F);
  EMIT(0x80 | cc);
  if (RelocInfo::IsRuntimeEntry(rmode)) {
    emit(reinterpret_cast<uint32_t>(entry), rmode);
  } else {
    emit(entry - (pc_ + sizeof(int32_t)), rmode);
  }
}


void Assembler::j(Condition cc, Handle<Code> code) {
  EnsureSpace ensure_space(this);
  // 0000 1111 1000 tttn #32-bit disp
  EMIT(0x0F);
  EMIT(0x80 | cc);
  emit(code, RelocInfo::CODE_TARGET);
}


// FPU instructions.

void Assembler::fld(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xD9, 0xC0, i);
}


void Assembler::fstp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDD, 0xD8, i);
}


void Assembler::fld1() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xE8);
}


void Assembler::fldpi() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xEB);
}


void Assembler::fldz() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xEE);
}


void Assembler::fldln2() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xED);
}


void Assembler::fld_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  emit_operand(eax, adr);
}


void Assembler::fld_d(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDD);
  emit_operand(eax, adr);
}


void Assembler::fstp_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  emit_operand(ebx, adr);
}


void Assembler::fstp_d(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDD);
  emit_operand(ebx, adr);
}


void Assembler::fst_d(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDD);
  emit_operand(edx, adr);
}


void Assembler::fild_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  emit_operand(eax, adr);
}


void Assembler::fild_d(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDF);
  emit_operand(ebp, adr);
}


void Assembler::fistp_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  emit_operand(ebx, adr);
}


void Assembler::fisttp_s(const Operand& adr) {
  ASSERT(IsEnabled(SSE3));
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  emit_operand(ecx, adr);
}


void Assembler::fisttp_d(const Operand& adr) {
  ASSERT(IsEnabled(SSE3));
  EnsureSpace ensure_space(this);
  EMIT(0xDD);
  emit_operand(ecx, adr);
}


void Assembler::fist_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  emit_operand(edx, adr);
}


void Assembler::fistp_d(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDF);
  emit_operand(edi, adr);
}


void Assembler::fabs() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xE1);
}


void Assembler::fchs() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xE0);
}


void Assembler::fcos() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xFF);
}


void Assembler::fsin() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xFE);
}


void Assembler::fptan() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF2);
}


void Assembler::fyl2x() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF1);
}


void Assembler::f2xm1() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF0);
}


void Assembler::fscale() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xFD);
}


void Assembler::fninit() {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  EMIT(0xE3);
}


void Assembler::fadd(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDC, 0xC0, i);
}


void Assembler::fsub(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDC, 0xE8, i);
}


void Assembler::fisub_s(const Operand& adr) {
  EnsureSpace ensure_space(this);
  EMIT(0xDA);
  emit_operand(esp, adr);
}


void Assembler::fmul(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDC, 0xC8, i);
}


void Assembler::fdiv(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDC, 0xF8, i);
}


void Assembler::faddp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDE, 0xC0, i);
}


void Assembler::fsubp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDE, 0xE8, i);
}


void Assembler::fsubrp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDE, 0xE0, i);
}


void Assembler::fmulp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDE, 0xC8, i);
}


void Assembler::fdivp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDE, 0xF8, i);
}


void Assembler::fprem() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF8);
}


void Assembler::fprem1() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF5);
}


void Assembler::fxch(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xD9, 0xC8, i);
}


void Assembler::fincstp() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xF7);
}


void Assembler::ffree(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDD, 0xC0, i);
}


void Assembler::ftst() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xE4);
}


void Assembler::fucomp(int i) {
  EnsureSpace ensure_space(this);
  emit_farith(0xDD, 0xE8, i);
}


void Assembler::fucompp() {
  EnsureSpace ensure_space(this);
  EMIT(0xDA);
  EMIT(0xE9);
}


void Assembler::fucomi(int i) {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  EMIT(0xE8 + i);
}


void Assembler::fucomip() {
  EnsureSpace ensure_space(this);
  EMIT(0xDF);
  EMIT(0xE9);
}


void Assembler::fcompp() {
  EnsureSpace ensure_space(this);
  EMIT(0xDE);
  EMIT(0xD9);
}


void Assembler::fnstsw_ax() {
  EnsureSpace ensure_space(this);
  EMIT(0xDF);
  EMIT(0xE0);
}


void Assembler::fwait() {
  EnsureSpace ensure_space(this);
  EMIT(0x9B);
}


void Assembler::frndint() {
  EnsureSpace ensure_space(this);
  EMIT(0xD9);
  EMIT(0xFC);
}


void Assembler::fnclex() {
  EnsureSpace ensure_space(this);
  EMIT(0xDB);
  EMIT(0xE2);
}


void Assembler::sahf() {
  EnsureSpace ensure_space(this);
  EMIT(0x9E);
}


void Assembler::setcc(Condition cc, Register reg) {
  ASSERT(reg.is_byte_register());
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x90 | cc);
  EMIT(0xC0 | reg.code());
}


void Assembler::cvttss2si(Register dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0x0F);
  EMIT(0x2C);
  emit_operand(dst, src);
}


void Assembler::cvttsd2si(Register dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x2C);
  emit_operand(dst, src);
}


void Assembler::cvtsd2si(Register dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x2D);
  emit_sse_operand(dst, src);
}


void Assembler::cvtsi2sd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x2A);
  emit_sse_operand(dst, src);
}


void Assembler::cvtss2sd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0x0F);
  EMIT(0x5A);
  emit_sse_operand(dst, src);
}


void Assembler::cvtsd2ss(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x5A);
  emit_sse_operand(dst, src);
}


void Assembler::addsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x58);
  emit_sse_operand(dst, src);
}


void Assembler::addsd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x58);
  emit_sse_operand(dst, src);
}


void Assembler::mulsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x59);
  emit_sse_operand(dst, src);
}


void Assembler::mulsd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x59);
  emit_sse_operand(dst, src);
}


void Assembler::subsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x5C);
  emit_sse_operand(dst, src);
}


void Assembler::divsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x5E);
  emit_sse_operand(dst, src);
}


void Assembler::xorpd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x57);
  emit_sse_operand(dst, src);
}


void Assembler::xorps(XMMRegister dst, XMMRegister src) {
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x57);
  emit_sse_operand(dst, src);
}


void Assembler::sqrtsd(XMMRegister dst, XMMRegister src) {
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x51);
  emit_sse_operand(dst, src);
}


void Assembler::andpd(XMMRegister dst, XMMRegister src) {
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x54);
  emit_sse_operand(dst, src);
}


void Assembler::orpd(XMMRegister dst, XMMRegister src) {
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x56);
  emit_sse_operand(dst, src);
}


void Assembler::ucomisd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x2E);
  emit_sse_operand(dst, src);
}


void Assembler::ucomisd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x2E);
  emit_sse_operand(dst, src);
}


void Assembler::roundsd(XMMRegister dst, XMMRegister src, RoundingMode mode) {
  ASSERT(IsEnabled(SSE4_1));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x3A);
  EMIT(0x0B);
  emit_sse_operand(dst, src);
  // Mask precision exeption.
  EMIT(static_cast<byte>(mode) | 0x8);
}

void Assembler::movmskpd(Register dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x50);
  emit_sse_operand(dst, src);
}


void Assembler::movmskps(Register dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x50);
  emit_sse_operand(dst, src);
}


void Assembler::pcmpeqd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x76);
  emit_sse_operand(dst, src);
}


void Assembler::cmpltsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0xC2);
  emit_sse_operand(dst, src);
  EMIT(1);  // LT == 1
}


void Assembler::movaps(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x28);
  emit_sse_operand(dst, src);
}


void Assembler::movdqa(const Operand& dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x7F);
  emit_sse_operand(src, dst);
}


void Assembler::movdqa(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x6F);
  emit_sse_operand(dst, src);
}


void Assembler::movdqu(const Operand& dst, XMMRegister src ) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0x0F);
  EMIT(0x7F);
  emit_sse_operand(src, dst);
}


void Assembler::movdqu(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0x0F);
  EMIT(0x6F);
  emit_sse_operand(dst, src);
}


void Assembler::movntdqa(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE4_1));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x38);
  EMIT(0x2A);
  emit_sse_operand(dst, src);
}


void Assembler::movntdq(const Operand& dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xE7);
  emit_sse_operand(src, dst);
}


void Assembler::prefetch(const Operand& src, int level) {
  ASSERT(is_uint2(level));
  EnsureSpace ensure_space(this);
  EMIT(0x0F);
  EMIT(0x18);
  // Emit hint number in Reg position of RegR/M.
  XMMRegister code = XMMRegister::from_code(level);
  emit_sse_operand(code, src);
}


void Assembler::movdbl(XMMRegister dst, const Operand& src) {
  EnsureSpace ensure_space(this);
  movsd(dst, src);
}


void Assembler::movdbl(const Operand& dst, XMMRegister src) {
  EnsureSpace ensure_space(this);
  movsd(dst, src);
}


void Assembler::movsd(const Operand& dst, XMMRegister src ) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);  // double
  EMIT(0x0F);
  EMIT(0x11);  // store
  emit_sse_operand(src, dst);
}


void Assembler::movsd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);  // double
  EMIT(0x0F);
  EMIT(0x10);  // load
  emit_sse_operand(dst, src);
}


void Assembler::movsd(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF2);
  EMIT(0x0F);
  EMIT(0x10);
  emit_sse_operand(dst, src);
}


void Assembler::movss(const Operand& dst, XMMRegister src ) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);  // float
  EMIT(0x0F);
  EMIT(0x11);  // store
  emit_sse_operand(src, dst);
}


void Assembler::movss(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);  // float
  EMIT(0x0F);
  EMIT(0x10);  // load
  emit_sse_operand(dst, src);
}


void Assembler::movss(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0xF3);
  EMIT(0x0F);
  EMIT(0x10);
  emit_sse_operand(dst, src);
}


void Assembler::movd(XMMRegister dst, const Operand& src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x6E);
  emit_sse_operand(dst, src);
}


void Assembler::movd(const Operand& dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x7E);
  emit_sse_operand(src, dst);
}


void Assembler::extractps(Register dst, XMMRegister src, byte imm8) {
  ASSERT(CpuFeatures::IsSupported(SSE4_1));
  ASSERT(is_uint8(imm8));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x3A);
  EMIT(0x17);
  emit_sse_operand(dst, src);
  EMIT(imm8);
}


void Assembler::pand(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xDB);
  emit_sse_operand(dst, src);
}


void Assembler::pxor(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xEF);
  emit_sse_operand(dst, src);
}


void Assembler::por(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xEB);
  emit_sse_operand(dst, src);
}


void Assembler::ptest(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE4_1));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x38);
  EMIT(0x17);
  emit_sse_operand(dst, src);
}


void Assembler::psllq(XMMRegister reg, int8_t shift) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x73);
  emit_sse_operand(esi, reg);  // esi == 6
  EMIT(shift);
}


void Assembler::psllq(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xF3);
  emit_sse_operand(dst, src);
}


void Assembler::psrlq(XMMRegister reg, int8_t shift) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x73);
  emit_sse_operand(edx, reg);  // edx == 2
  EMIT(shift);
}


void Assembler::psrlq(XMMRegister dst, XMMRegister src) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0xD3);
  emit_sse_operand(dst, src);
}


void Assembler::pshufd(XMMRegister dst, XMMRegister src, uint8_t shuffle) {
  ASSERT(IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x70);
  emit_sse_operand(dst, src);
  EMIT(shuffle);
}


void Assembler::pextrd(const Operand& dst, XMMRegister src, int8_t offset) {
  ASSERT(IsEnabled(SSE4_1));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x3A);
  EMIT(0x16);
  emit_sse_operand(src, dst);
  EMIT(offset);
}


void Assembler::pinsrd(XMMRegister dst, const Operand& src, int8_t offset) {
  ASSERT(IsEnabled(SSE4_1));
  EnsureSpace ensure_space(this);
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x3A);
  EMIT(0x22);
  emit_sse_operand(dst, src);
  EMIT(offset);
}


void Assembler::emit_sse_operand(XMMRegister reg, const Operand& adr) {
  Register ireg = { reg.code() };
  emit_operand(ireg, adr);
}


void Assembler::emit_sse_operand(XMMRegister dst, XMMRegister src) {
  EMIT(0xC0 | dst.code() << 3 | src.code());
}


void Assembler::emit_sse_operand(Register dst, XMMRegister src) {
  EMIT(0xC0 | dst.code() << 3 | src.code());
}


void Assembler::Print() {
  Disassembler::Decode(isolate(), stdout, buffer_, pc_);
}


void Assembler::RecordJSReturn() {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  RecordRelocInfo(RelocInfo::JS_RETURN);
}


void Assembler::RecordDebugBreakSlot() {
  positions_recorder()->WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  RecordRelocInfo(RelocInfo::DEBUG_BREAK_SLOT);
}


void Assembler::RecordComment(const char* msg, bool force) {
  if (FLAG_code_comments || force) {
    EnsureSpace ensure_space(this);
    RecordRelocInfo(RelocInfo::COMMENT, reinterpret_cast<intptr_t>(msg));
  }
}


void Assembler::GrowBuffer() {
  ASSERT(overflow());
  if (!own_buffer_) FATAL("external code buffer is too small");

  // Compute new buffer size.
  CodeDesc desc;  // the new buffer
  if (buffer_size_ < 4*KB) {
    desc.buffer_size = 4*KB;
  } else {
    desc.buffer_size = 2*buffer_size_;
  }
  // Some internal data structures overflow for very large buffers,
  // they must ensure that kMaximalBufferSize is not too large.
  if ((desc.buffer_size > kMaximalBufferSize) ||
      (desc.buffer_size > isolate()->heap()->MaxOldGenerationSize())) {
    V8::FatalProcessOutOfMemory("Assembler::GrowBuffer");
  }

  // Set up new buffer.
  desc.buffer = NewArray<byte>(desc.buffer_size);
  desc.instr_size = pc_offset();
  desc.reloc_size = (buffer_ + buffer_size_) - (reloc_info_writer.pos());

  // Clear the buffer in debug mode. Use 'int3' instructions to make
  // sure to get into problems if we ever run uninitialized code.
#ifdef DEBUG
  memset(desc.buffer, 0xCC, desc.buffer_size);
#endif

  // Copy the data.
  int pc_delta = desc.buffer - buffer_;
  int rc_delta = (desc.buffer + desc.buffer_size) - (buffer_ + buffer_size_);
  OS::MemMove(desc.buffer, buffer_, desc.instr_size);
  OS::MemMove(rc_delta + reloc_info_writer.pos(),
              reloc_info_writer.pos(), desc.reloc_size);

  // Switch buffers.
  if (isolate()->assembler_spare_buffer() == NULL &&
      buffer_size_ == kMinimalBufferSize) {
    isolate()->set_assembler_spare_buffer(buffer_);
  } else {
    DeleteArray(buffer_);
  }
  buffer_ = desc.buffer;
  buffer_size_ = desc.buffer_size;
  pc_ += pc_delta;
  reloc_info_writer.Reposition(reloc_info_writer.pos() + rc_delta,
                               reloc_info_writer.last_pc() + pc_delta);

  // Relocate runtime entries.
  for (RelocIterator it(desc); !it.done(); it.next()) {
    RelocInfo::Mode rmode = it.rinfo()->rmode();
    if (rmode == RelocInfo::INTERNAL_REFERENCE) {
      int32_t* p = reinterpret_cast<int32_t*>(it.rinfo()->pc());
      if (*p != 0) {  // 0 means uninitialized.
        *p += pc_delta;
      }
    }
  }

  ASSERT(!overflow());
}


void Assembler::emit_arith_b(int op1, int op2, Register dst, int imm8) {
  ASSERT(is_uint8(op1) && is_uint8(op2));  // wrong opcode
  ASSERT(is_uint8(imm8));
  ASSERT((op1 & 0x01) == 0);  // should be 8bit operation
  EMIT(op1);
  EMIT(op2 | dst.code());
  EMIT(imm8);
}


void Assembler::emit_arith(int sel, Operand dst, const Immediate& x) {
  ASSERT((0 <= sel) && (sel <= 7));
  Register ireg = { sel };
  if (x.is_int8()) {
    EMIT(0x83);  // using a sign-extended 8-bit immediate.
    emit_operand(ireg, dst);
    EMIT(x.x_ & 0xFF);
  } else if (dst.is_reg(eax)) {
    EMIT((sel << 3) | 0x05);  // short form if the destination is eax.
    emit(x);
  } else {
    EMIT(0x81);  // using a literal 32-bit immediate.
    emit_operand(ireg, dst);
    emit(x);
  }
}


void Assembler::emit_operand(Register reg, const Operand& adr) {
  const unsigned length = adr.len_;
  ASSERT(length > 0);

  // Emit updated ModRM byte containing the given register.
  pc_[0] = (adr.buf_[0] & ~0x38) | (reg.code() << 3);

  // Emit the rest of the encoded operand.
  for (unsigned i = 1; i < length; i++) pc_[i] = adr.buf_[i];
  pc_ += length;

  // Emit relocation information if necessary.
  if (length >= sizeof(int32_t) && !RelocInfo::IsNone(adr.rmode_)) {
    pc_ -= sizeof(int32_t);  // pc_ must be *at* disp32
    RecordRelocInfo(adr.rmode_);
    pc_ += sizeof(int32_t);
  }
}


void Assembler::emit_farith(int b1, int b2, int i) {
  ASSERT(is_uint8(b1) && is_uint8(b2));  // wrong opcode
  ASSERT(0 <= i &&  i < 8);  // illegal stack offset
  EMIT(b1);
  EMIT(b2 + i);
}


void Assembler::db(uint8_t data) {
  EnsureSpace ensure_space(this);
  EMIT(data);
}


void Assembler::dd(uint32_t data) {
  EnsureSpace ensure_space(this);
  emit(data);
}


void Assembler::RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data) {
  ASSERT(!RelocInfo::IsNone(rmode));
  // Don't record external references unless the heap will be serialized.
  if (rmode == RelocInfo::EXTERNAL_REFERENCE) {
#ifdef DEBUG
    if (!Serializer::enabled()) {
      Serializer::TooLateToEnableNow();
    }
#endif
    if (!Serializer::enabled() && !emit_debug_code()) {
      return;
    }
  }
  RelocInfo rinfo(pc_, rmode, data, NULL);
  reloc_info_writer.Write(&rinfo);
}


#ifdef GENERATED_CODE_COVERAGE
static FILE* coverage_log = NULL;


static void InitCoverageLog() {
  char* file_name = getenv("V8_GENERATED_CODE_COVERAGE_LOG");
  if (file_name != NULL) {
    coverage_log = fopen(file_name, "aw+");
  }
}


void LogGeneratedCodeCoverage(const char* file_line) {
  const char* return_address = (&file_line)[-1];
  char* push_insn = const_cast<char*>(return_address - 12);
  push_insn[0] = 0xeb;  // Relative branch insn.
  push_insn[1] = 13;    // Skip over coverage insns.
  if (coverage_log != NULL) {
    fprintf(coverage_log, "%s\n", file_line);
    fflush(coverage_log);
  }
}

#endif

} }  // namespace v8::internal

#endif  // V8_TARGET_ARCH_IA32