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 2006-2008 the V8 project authors. All rights reserved.

#include "v8.h"

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

namespace v8 {
namespace internal {

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

// Safe default is no features.
uint64_t CpuFeatures::supported_ = 0;
uint64_t CpuFeatures::enabled_ = 0;
uint64_t CpuFeatures::found_by_runtime_probing_ = 0;


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

  Assembler assm(NULL, 0);
  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, Operand(esp));

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

  // CPUID not supported. Clear the supported features in edx:eax.
  __ xor_(eax, Operand(eax));
  __ xor_(edx, Operand(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);
  { Scope fscope(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, Operand(edx));
  __ or_(eax, 1 << CPUID);
  __ mov(edx, Operand(ecx));

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

  CodeDesc desc;
  assm.GetCode(&desc);
  Object* code = Heap::CreateCode(desc,
                                  NULL,
                                  Code::ComputeFlags(Code::STUB),
                                  Handle<Code>::null());
  if (!code->IsCode()) return;
  LOG(CodeCreateEvent(Logger::BUILTIN_TAG,
                      Code::cast(code), "CpuFeatures::Probe"));
  typedef uint64_t (*F0)();
  F0 probe = FUNCTION_CAST<F0>(Code::cast(code)->entry());
  supported_ = probe();
  found_by_runtime_probing_ = supported_;
  uint64_t os_guarantees = OS::CpuFeaturesImpliedByPlatform();
  supported_ |= os_guarantees;
  found_by_runtime_probing_ &= ~os_guarantees;
}


// -----------------------------------------------------------------------------
// 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;


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::NONE);

  // 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.
  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 && rmode == RelocInfo::NONE && !base.is(ebp)) {
    // [base]
    set_modrm(0, base);
    if (base.is(esp)) set_sib(times_1, esp, base);
  } else if (is_int8(disp) && rmode == RelocInfo::NONE) {
    // [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 && rmode == RelocInfo::NONE && !base.is(ebp)) {
    // [base + index*scale]
    set_modrm(0, esp);
    set_sib(scale, index, base);
  } else if (is_int8(disp) && rmode == RelocInfo::NONE) {
    // [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.
}

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

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


#ifdef GENERATED_CODE_COVERAGE
static void InitCoverageLog();
#endif

// Spare buffer.
byte* Assembler::spare_buffer_ = NULL;

Assembler::Assembler(void* buffer, int buffer_size) {
  if (buffer == NULL) {
    // Do our own buffer management.
    if (buffer_size <= kMinimalBufferSize) {
      buffer_size = kMinimalBufferSize;

      if (spare_buffer_ != NULL) {
        buffer = spare_buffer_;
        spare_buffer_ = NULL;
      }
    }
    if (buffer == NULL) {
      buffer_ = NewArray<byte>(buffer_size);
    } else {
      buffer_ = static_cast<byte*>(buffer);
    }
    buffer_size_ = buffer_size;
    own_buffer_ = true;
  } else {
    // Use externally provided buffer instead.
    ASSERT(buffer_size > 0);
    buffer_ = static_cast<byte*>(buffer);
    buffer_size_ = buffer_size;
    own_buffer_ = false;
  }

  // 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

  // Setup buffer pointers.
  ASSERT(buffer_ != NULL);
  pc_ = buffer_;
  reloc_info_writer.Reposition(buffer_ + buffer_size, pc_);

  last_pc_ = NULL;
  current_statement_position_ = RelocInfo::kNoPosition;
  current_position_ = RelocInfo::kNoPosition;
  written_statement_position_ = current_statement_position_;
  written_position_ = current_position_;
#ifdef GENERATED_CODE_COVERAGE
  InitCoverageLog();
#endif
}


Assembler::~Assembler() {
  if (own_buffer_) {
    if (spare_buffer_ == NULL && buffer_size_ == kMinimalBufferSize) {
      spare_buffer_ = buffer_;
    } else {
      DeleteArray(buffer_);
    }
  }
}


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.
  // Setup 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;

  Counters::reloc_info_size.Increment(desc->reloc_size);
}


void Assembler::Align(int m) {
  ASSERT(IsPowerOf2(m));
  while ((pc_offset() & (m - 1)) != 0) {
    nop();
  }
}


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


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


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


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


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


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


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


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


void Assembler::pop(Register dst) {
  ASSERT(reloc_info_writer.last_pc() != NULL);
  if (FLAG_push_pop_elimination && (reloc_info_writer.last_pc() <= last_pc_)) {
    // (last_pc_ != NULL) is rolled into the above check.
    // If a last_pc_ is set, we need to make sure that there has not been any
    // relocation information generated between the last instruction and this
    // pop instruction.
    byte instr = last_pc_[0];
    if ((instr & ~0x7) == 0x50) {
      int push_reg_code = instr & 0x7;
      if (push_reg_code == dst.code()) {
        pc_ = last_pc_;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (same reg) eliminated\n", pc_offset());
        }
      } else {
        // Convert 'push src; pop dst' to 'mov dst, src'.
        last_pc_[0] = 0x8b;
        Register src = { push_reg_code };
        EnsureSpace ensure_space(this);
        emit_operand(dst, Operand(src));
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (reg->reg) eliminated\n", pc_offset());
        }
      }
      last_pc_ = NULL;
      return;
    } else if (instr == 0xff) {  // push of an operand, convert to a move
      byte op1 = last_pc_[1];
      // Check if the operation is really a push.
      if ((op1 & 0x38) == (6 << 3)) {
        op1 = (op1 & ~0x38) | static_cast<byte>(dst.code() << 3);
        last_pc_[0] = 0x8b;
        last_pc_[1] = op1;
        last_pc_ = NULL;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (op->reg) eliminated\n", pc_offset());
        }
        return;
      }
    } else if ((instr == 0x89) &&
               (last_pc_[1] == 0x04) &&
               (last_pc_[2] == 0x24)) {
      // 0x71283c   396  890424         mov [esp],eax
      // 0x71283f   399  58             pop eax
      if (dst.is(eax)) {
        // change to
        // 0x710fac   216  83c404         add esp,0x4
        last_pc_[0] = 0x83;
        last_pc_[1] = 0xc4;
        last_pc_[2] = 0x04;
        last_pc_ = NULL;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (mov-pop) eliminated\n", pc_offset());
        }
        return;
      }
    } else if (instr == 0x6a && dst.is(eax)) {  // push of immediate 8 bit
      byte imm8 = last_pc_[1];
      if (imm8 == 0) {
        // 6a00         push 0x0
        // 58           pop eax
        last_pc_[0] = 0x31;
        last_pc_[1] = 0xc0;
        // change to
        // 31c0         xor eax,eax
        last_pc_ = NULL;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (imm->reg) eliminated\n", pc_offset());
        }
        return;
      } else {
        // 6a00         push 0xXX
        // 58           pop eax
        last_pc_[0] = 0xb8;
        EnsureSpace ensure_space(this);
        if ((imm8 & 0x80) != 0) {
          EMIT(0xff);
          EMIT(0xff);
          EMIT(0xff);
          // change to
          // b8XXffffff   mov eax,0xffffffXX
        } else {
          EMIT(0x00);
          EMIT(0x00);
          EMIT(0x00);
          // change to
          // b8XX000000   mov eax,0x000000XX
        }
        last_pc_ = NULL;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop (imm->reg) eliminated\n", pc_offset());
        }
        return;
      }
    } else if (instr == 0x68 && dst.is(eax)) {  // push of immediate 32 bit
      // 68XXXXXXXX   push 0xXXXXXXXX
      // 58           pop eax
      last_pc_[0] = 0xb8;
      last_pc_ = NULL;
      // change to
      // b8XXXXXXXX   mov eax,0xXXXXXXXX
      if (FLAG_print_push_pop_elimination) {
        PrintF("%d push/pop (imm->reg) eliminated\n", pc_offset());
      }
      return;
    }

    // Other potential patterns for peephole:
    // 0x712716   102  890424         mov [esp], eax
    // 0x712719   105  8b1424         mov edx, [esp]
  }
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x58 | dst.code());
}


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


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


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


void Assembler::mov_b(Register dst, const Operand& src) {
  ASSERT(dst.code() < 4);
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x8A);
  emit_operand(dst, src);
}


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


void Assembler::mov_b(const Operand& dst, Register src) {
  ASSERT(src.code() < 4);
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x88);
  emit_operand(src, dst);
}


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


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


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


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


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


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


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


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


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


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


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


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


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


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


void Assembler::cmov(Condition cc, Register dst, int32_t imm32) {
  ASSERT(CpuFeatures::IsEnabled(CMOV));
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  UNIMPLEMENTED();
  USE(cc);
  USE(dst);
  USE(imm32);
}


void Assembler::cmov(Condition cc, Register dst, Handle<Object> handle) {
  ASSERT(CpuFeatures::IsEnabled(CMOV));
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  UNIMPLEMENTED();
  USE(cc);
  USE(dst);
  USE(handle);
}


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


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


void Assembler::xchg(Register dst, Register src) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  emit_arith(2, Operand(dst), Immediate(imm32));
}


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


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


void Assembler::add(const Operand& dst, const Immediate& x) {
  ASSERT(reloc_info_writer.last_pc() != NULL);
  if (FLAG_push_pop_elimination && (reloc_info_writer.last_pc() <= last_pc_)) {
    byte instr = last_pc_[0];
    if ((instr & 0xf8) == 0x50) {
      // Last instruction was a push. Check whether this is a pop without a
      // result.
      if ((dst.is_reg(esp)) &&
          (x.x_ == kPointerSize) && (x.rmode_ == RelocInfo::NONE)) {
        pc_ = last_pc_;
        last_pc_ = NULL;
        if (FLAG_print_push_pop_elimination) {
          PrintF("%d push/pop(noreg) eliminated\n", pc_offset());
        }
        return;
      }
    }
  }
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  emit_arith(0, dst, x);
}


void Assembler::and_(Register dst, int32_t imm32) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  emit_arith(4, Operand(dst), Immediate(imm32));
}


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


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


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


void Assembler::cmpb(const Operand& op, int8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x80);
  emit_operand(edi, op);  // edi == 7
  EMIT(imm8);
}


void Assembler::cmpb(const Operand& dst, Register src) {
  ASSERT(src.is_byte_register());
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x38);
  emit_operand(src, dst);
}


void Assembler::cmpb(Register dst, const Operand& src) {
  ASSERT(dst.is_byte_register());
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x3A);
  emit_operand(dst, src);
}


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


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


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


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


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


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


void Assembler::cmpb_al(const Operand& op) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  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) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0xFE);
  EMIT(0xC8 | dst.code());
}


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


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


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


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


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


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


void Assembler::imul(Register dst, Register src, int32_t imm32) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  EMIT(0x40 | dst.code());
}


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


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


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


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


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


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


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


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


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


void Assembler::rcl(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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::sar(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  EMIT(0xD3);
  EMIT(0xF8 | dst.code());
}


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


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


void Assembler::shl(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  EMIT(0xD3);
  EMIT(0xE0 | dst.code());
}


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


void Assembler::shr(Register dst, uint8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = pc_;
  EMIT(0xD3);
  EMIT(0xE8 | dst.code());
}


void Assembler::subb(const Operand& op, int8_t imm8) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  if (op.is_reg(eax)) {
    EMIT(0x2c);
  } else {
    EMIT(0x80);
    emit_operand(ebp, op);  // ebp == 5
  }
  EMIT(imm8);
}


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


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


void Assembler::subb(Register dst, const Operand& src) {
  ASSERT(dst.code() < 4);
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x2A);
  emit_operand(dst, src);
}


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


void Assembler::test(Register reg, const Immediate& imm) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  // Only use test against byte for registers that have a byte
  // variant: eax, ebx, ecx, and edx.
  if (imm.rmode_ == RelocInfo::NONE && is_uint8(imm.x_) && reg.code() < 4) {
    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);
  last_pc_ = pc_;
  EMIT(0x85);
  emit_operand(reg, op);
}


void Assembler::test_b(Register reg, const Operand& op) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x84);
  emit_operand(reg, op);
}


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


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


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


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


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


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


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


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


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


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


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


void Assembler::ret(int imm16) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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);
  last_pc_ = NULL;
  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);
  }
  L->bind_to(pos);
}


void Assembler::link_to(Label* L, Label* appendix) {
  EnsureSpace ensure_space(this);
  last_pc_ = NULL;
  if (appendix->is_linked()) {
    if (L->is_linked()) {
      // Append appendix to L's list.
      Label p;
      Label q = *L;
      do {
        p = q;
        Displacement disp = disp_at(&q);
        disp.next(&q);
      } while (q.is_linked());
      Displacement disp = disp_at(&p);
      disp.link_to(appendix);
      disp_at_put(&p, disp);
      p.Unuse();  // to avoid assertion failure in ~Label
    } else {
      // L is empty, simply use appendix.
      *L = *appendix;
    }
  }
  appendix->Unuse();  // appendix should not be used anymore
}


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


void Assembler::call(Label* L) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  ASSERT(!RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE8);
  emit(entry - (pc_ + sizeof(int32_t)), rmode);
}


void Assembler::call(const Operand& adr) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0xFF);
  emit_operand(edx, adr);
}


void Assembler::call(Handle<Code> code, RelocInfo::Mode rmode) {
  WriteRecordedPositions();
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE8);
  emit(reinterpret_cast<intptr_t>(code.location()), rmode);
}


void Assembler::jmp(Label* L) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  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 {
    // 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);
  last_pc_ = pc_;
  ASSERT(!RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE9);
  emit(entry - (pc_ + sizeof(int32_t)), rmode);
}


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


void Assembler::jmp(Handle<Code> code, RelocInfo::Mode rmode) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  EMIT(0xE9);
  emit(reinterpret_cast<intptr_t>(code.location()), rmode);
}



void Assembler::j(Condition cc, Label* L, Hint hint) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  ASSERT(0 <= cc && cc < 16);
  if (FLAG_emit_branch_hints && hint != no_hint) EMIT(hint);
  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 {
    // 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, Hint hint) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  ASSERT((0 <= cc) && (cc < 16));
  if (FLAG_emit_branch_hints && hint != no_hint) EMIT(hint);
  // 0000 1111 1000 tttn #32-bit disp.
  EMIT(0x0F);
  EMIT(0x80 | cc);
  emit(entry - (pc_ + sizeof(int32_t)), rmode);
}


void Assembler::j(Condition cc, Handle<Code> code, Hint hint) {
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  if (FLAG_emit_branch_hints && hint != no_hint) EMIT(hint);
  // 0000 1111 1000 tttn #32-bit disp
  EMIT(0x0F);
  EMIT(0x80 | cc);
  emit(reinterpret_cast<intptr_t>(code.location()), RelocInfo::CODE_TARGET);
}


// FPU instructions.

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


void Assembler::comisd(XMMRegister dst, XMMRegister src) {
  ASSERT(CpuFeatures::IsEnabled(SSE2));
  EnsureSpace ensure_space(this);
  last_pc_ = pc_;
  EMIT(0x66);
  EMIT(0x0F);
  EMIT(0x2F);
  emit_sse_operand(dst, src);
}


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


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


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


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


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


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


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


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


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


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


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


void Assembler::RecordPosition(int pos) {
  ASSERT(pos != RelocInfo::kNoPosition);
  ASSERT(pos >= 0);
  current_position_ = pos;
}


void Assembler::RecordStatementPosition(int pos) {
  ASSERT(pos != RelocInfo::kNoPosition);
  ASSERT(pos >= 0);
  current_statement_position_ = pos;
}


void Assembler::WriteRecordedPositions() {
  // Write the statement position if it is different from what was written last
  // time.
  if (current_statement_position_ != written_statement_position_) {
    EnsureSpace ensure_space(this);
    RecordRelocInfo(RelocInfo::STATEMENT_POSITION, current_statement_position_);
    written_statement_position_ = current_statement_position_;
  }

  // Write the position if it is different from what was written last time and
  // also different from the written statement position.
  if (current_position_ != written_position_ &&
      current_position_ != written_statement_position_) {
    EnsureSpace ensure_space(this);
    RecordRelocInfo(RelocInfo::POSITION, current_position_);
    written_position_ = current_position_;
  }
}


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 > Heap::MaxOldGenerationSize())) {
    V8::FatalProcessOutOfMemory("Assembler::GrowBuffer");
  }

  // Setup 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_);
  memmove(desc.buffer, buffer_, desc.instr_size);
  memmove(rc_delta + reloc_info_writer.pos(),
          reloc_info_writer.pos(), desc.reloc_size);

  // Switch buffers.
  if (spare_buffer_ == NULL && buffer_size_ == kMinimalBufferSize) {
    spare_buffer_ = buffer_;
  } else {
    DeleteArray(buffer_);
  }
  buffer_ = desc.buffer;
  buffer_size_ = desc.buffer_size;
  pc_ += pc_delta;
  if (last_pc_ != NULL) {
    last_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::RUNTIME_ENTRY) {
      int32_t* p = reinterpret_cast<int32_t*>(it.rinfo()->pc());
      *p -= pc_delta;  // relocate entry
    } else 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) && adr.rmode_ != RelocInfo::NONE) {
    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::dd(uint32_t data, RelocInfo::Mode reloc_info) {
  EnsureSpace ensure_space(this);
  emit(data, reloc_info);
}


void Assembler::RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data) {
  ASSERT(rmode != RelocInfo::NONE);
  // 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() && !FLAG_debug_code) {
      return;
    }
  }
  RelocInfo rinfo(pc_, rmode, data);
  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