CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. 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.

//     * Redistributions 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 Google Inc. nor the names of its

//       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.

#include "v8.h"

#if V8_TARGET_ARCH_MIPS

#include "codegen.h"

#include "macro-assembler.h"

#include "simulator-mips.h"

namespace v8 {

namespace internal {

UnaryMathFunction CreateTranscendentalFunction(TranscendentalCache::Type type) {

  switch (type) {

    case TranscendentalCache::SIN: return &sin;

    case TranscendentalCache::COS: return &cos;

    case TranscendentalCache::TAN: return &tan;

    case TranscendentalCache::LOG: return &log;

    default: UNIMPLEMENTED();

  }

  return NULL;

}

#define __ masm.

#if defined(USE_SIMULATOR)

byte* fast_exp_mips_machine_code = NULL;

double fast_exp_simulator(double x) {

  return Simulator::current(Isolate::Current())->CallFP(

      fast_exp_mips_machine_code, x, 0);

}

#endif

UnaryMathFunction CreateExpFunction() {

  if (!FLAG_fast_math) return &exp;

  size_t actual_size;

  byte* buffer = static_cast<byte*>(OS::Allocate(1 * KB, &actual_size, true));

  if (buffer == NULL) return &exp;

  ExternalReference::InitializeMathExpData();

  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));

  {

    DoubleRegister input = f12;

    DoubleRegister result = f0;

    DoubleRegister double_scratch1 = f4;

    DoubleRegister double_scratch2 = f6;

    Register temp1 = t0;

    Register temp2 = t1;

    Register temp3 = t2;

    if (!IsMipsSoftFloatABI) {

      // Input value is in f12 anyway, nothing to do.

    } else {

      __ Move(input, a0, a1);

    }

    __ Push(temp3, temp2, temp1);

    MathExpGenerator::EmitMathExp(

        &masm, input, result, double_scratch1, double_scratch2,

        temp1, temp2, temp3);

    __ Pop(temp3, temp2, temp1);

    if (!IsMipsSoftFloatABI) {

      // Result is already in f0, nothing to do.

    } else {

      __ Move(v0, v1, result);

    }

    __ Ret();

  }

  CodeDesc desc;

  masm.GetCode(&desc);

  ASSERT(!RelocInfo::RequiresRelocation(desc));

  CPU::FlushICache(buffer, actual_size);

  OS::ProtectCode(buffer, actual_size);

#if !defined(USE_SIMULATOR)

  return FUNCTION_CAST<UnaryMathFunction>(buffer);

#else

  fast_exp_mips_machine_code = buffer;

  return &fast_exp_simulator;

#endif

}

#undef __

UnaryMathFunction CreateSqrtFunction() {

  return &sqrt;

}

// -------------------------------------------------------------------------

// Platform-specific RuntimeCallHelper functions.

void StubRuntimeCallHelper::BeforeCall(MacroAssembler* masm) const {

  masm->EnterFrame(StackFrame::INTERNAL);

  ASSERT(!masm->has_frame());

  masm->set_has_frame(true);

}

void StubRuntimeCallHelper::AfterCall(MacroAssembler* masm) const {

  masm->LeaveFrame(StackFrame::INTERNAL);

  ASSERT(masm->has_frame());

  masm->set_has_frame(false);

}

// -------------------------------------------------------------------------

// Code generators

#define __ ACCESS_MASM(masm)

void ElementsTransitionGenerator::GenerateMapChangeElementsTransition(

    MacroAssembler* masm, AllocationSiteMode mode,

    Label* allocation_memento_found) {

  // ----------- S t a t e -------------

  //  -- a0    : value

  //  -- a1    : key

  //  -- a2    : receiver

  //  -- ra    : return address

  //  -- a3    : target map, scratch for subsequent call

  //  -- t0    : scratch (elements)

  // -----------------------------------

  if (mode == TRACK_ALLOCATION_SITE) {

    ASSERT(allocation_memento_found != NULL);

    __ JumpIfJSArrayHasAllocationMemento(a2, t0, allocation_memento_found);

  }

  // Set transitioned map.

  __ sw(a3, FieldMemOperand(a2, HeapObject::kMapOffset));

  __ RecordWriteField(a2,

                      HeapObject::kMapOffset,

                      a3,

                      t5,

                      kRAHasNotBeenSaved,

                      kDontSaveFPRegs,

                      EMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

}

void ElementsTransitionGenerator::GenerateSmiToDouble(

    MacroAssembler* masm, AllocationSiteMode mode, Label* fail) {

  // ----------- S t a t e -------------

  //  -- a0    : value

  //  -- a1    : key

  //  -- a2    : receiver

  //  -- ra    : return address

  //  -- a3    : target map, scratch for subsequent call

  //  -- t0    : scratch (elements)

  // -----------------------------------

  Label loop, entry, convert_hole, gc_required, only_change_map, done;

  Register scratch = t6;

  if (mode == TRACK_ALLOCATION_SITE) {

    __ JumpIfJSArrayHasAllocationMemento(a2, t0, fail);

  }

  // Check for empty arrays, which only require a map transition and no changes

  // to the backing store.

  __ lw(t0, FieldMemOperand(a2, JSObject::kElementsOffset));

  __ LoadRoot(at, Heap::kEmptyFixedArrayRootIndex);

  __ Branch(&only_change_map, eq, at, Operand(t0));

  __ push(ra);

  __ lw(t1, FieldMemOperand(t0, FixedArray::kLengthOffset));

  // t0: source FixedArray

  // t1: number of elements (smi-tagged)

  // Allocate new FixedDoubleArray.

  __ sll(scratch, t1, 2);

  __ Addu(scratch, scratch, FixedDoubleArray::kHeaderSize);

  __ Allocate(scratch, t2, t3, t5, &gc_required, DOUBLE_ALIGNMENT);

  // t2: destination FixedDoubleArray, not tagged as heap object

  // Set destination FixedDoubleArray's length and map.

  __ LoadRoot(t5, Heap::kFixedDoubleArrayMapRootIndex);

  __ sw(t1, MemOperand(t2, FixedDoubleArray::kLengthOffset));

  __ sw(t5, MemOperand(t2, HeapObject::kMapOffset));

  // Update receiver's map.

  __ sw(a3, FieldMemOperand(a2, HeapObject::kMapOffset));

  __ RecordWriteField(a2,

                      HeapObject::kMapOffset,

                      a3,

                      t5,

                      kRAHasBeenSaved,

                      kDontSaveFPRegs,

                      OMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

  // Replace receiver's backing store with newly created FixedDoubleArray.

  __ Addu(a3, t2, Operand(kHeapObjectTag));

  __ sw(a3, FieldMemOperand(a2, JSObject::kElementsOffset));

  __ RecordWriteField(a2,

                      JSObject::kElementsOffset,

                      a3,

                      t5,

                      kRAHasBeenSaved,

                      kDontSaveFPRegs,

                      EMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

  // Prepare for conversion loop.

  __ Addu(a3, t0, Operand(FixedArray::kHeaderSize - kHeapObjectTag));

  __ Addu(t3, t2, Operand(FixedDoubleArray::kHeaderSize));

  __ sll(t2, t1, 2);

  __ Addu(t2, t2, t3);

  __ li(t0, Operand(kHoleNanLower32));

  __ li(t1, Operand(kHoleNanUpper32));

  // t0: kHoleNanLower32

  // t1: kHoleNanUpper32

  // t2: end of destination FixedDoubleArray, not tagged

  // t3: begin of FixedDoubleArray element fields, not tagged

  __ Branch(&entry);

  __ bind(&only_change_map);

  __ sw(a3, FieldMemOperand(a2, HeapObject::kMapOffset));

  __ RecordWriteField(a2,

                      HeapObject::kMapOffset,

                      a3,

                      t5,

                      kRAHasNotBeenSaved,

                      kDontSaveFPRegs,

                      OMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

  __ Branch(&done);

  // Call into runtime if GC is required.

  __ bind(&gc_required);

  __ pop(ra);

  __ Branch(fail);

  // Convert and copy elements.

  __ bind(&loop);

  __ lw(t5, MemOperand(a3));

  __ Addu(a3, a3, kIntSize);

  // t5: current element

  __ UntagAndJumpIfNotSmi(t5, t5, &convert_hole);

  // Normal smi, convert to double and store.

  __ mtc1(t5, f0);

  __ cvt_d_w(f0, f0);

  __ sdc1(f0, MemOperand(t3));

  __ Addu(t3, t3, kDoubleSize);

  __ Branch(&entry);

  // Hole found, store the-hole NaN.

  __ bind(&convert_hole);

  if (FLAG_debug_code) {

    // Restore a "smi-untagged" heap object.

    __ SmiTag(t5);

    __ Or(t5, t5, Operand(1));

    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);

    __ Assert(eq, kObjectFoundInSmiOnlyArray, at, Operand(t5));

  }

  __ sw(t0, MemOperand(t3));  // mantissa

  __ sw(t1, MemOperand(t3, kIntSize));  // exponent

  __ Addu(t3, t3, kDoubleSize);

  __ bind(&entry);

  __ Branch(&loop, lt, t3, Operand(t2));

  __ pop(ra);

  __ bind(&done);

}

void ElementsTransitionGenerator::GenerateDoubleToObject(

    MacroAssembler* masm, AllocationSiteMode mode, Label* fail) {

  // ----------- S t a t e -------------

  //  -- a0    : value

  //  -- a1    : key

  //  -- a2    : receiver

  //  -- ra    : return address

  //  -- a3    : target map, scratch for subsequent call

  //  -- t0    : scratch (elements)

  // -----------------------------------

  Label entry, loop, convert_hole, gc_required, only_change_map;

  if (mode == TRACK_ALLOCATION_SITE) {

    __ JumpIfJSArrayHasAllocationMemento(a2, t0, fail);

  }

  // Check for empty arrays, which only require a map transition and no changes

  // to the backing store.

  __ lw(t0, FieldMemOperand(a2, JSObject::kElementsOffset));

  __ LoadRoot(at, Heap::kEmptyFixedArrayRootIndex);

  __ Branch(&only_change_map, eq, at, Operand(t0));

  __ MultiPush(a0.bit() | a1.bit() | a2.bit() | a3.bit() | ra.bit());

  __ lw(t1, FieldMemOperand(t0, FixedArray::kLengthOffset));

  // t0: source FixedArray

  // t1: number of elements (smi-tagged)

  // Allocate new FixedArray.

  __ sll(a0, t1, 1);

  __ Addu(a0, a0, FixedDoubleArray::kHeaderSize);

  __ Allocate(a0, t2, t3, t5, &gc_required, NO_ALLOCATION_FLAGS);

  // t2: destination FixedArray, not tagged as heap object

  // Set destination FixedDoubleArray's length and map.

  __ LoadRoot(t5, Heap::kFixedArrayMapRootIndex);

  __ sw(t1, MemOperand(t2, FixedDoubleArray::kLengthOffset));

  __ sw(t5, MemOperand(t2, HeapObject::kMapOffset));

  // Prepare for conversion loop.

  __ Addu(t0, t0, Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag + 4));

  __ Addu(a3, t2, Operand(FixedArray::kHeaderSize));

  __ Addu(t2, t2, Operand(kHeapObjectTag));

  __ sll(t1, t1, 1);

  __ Addu(t1, a3, t1);

  __ LoadRoot(t3, Heap::kTheHoleValueRootIndex);

  __ LoadRoot(t5, Heap::kHeapNumberMapRootIndex);

  // Using offsetted addresses.

  // a3: begin of destination FixedArray element fields, not tagged

  // t0: begin of source FixedDoubleArray element fields, not tagged, +4

  // t1: end of destination FixedArray, not tagged

  // t2: destination FixedArray

  // t3: the-hole pointer

  // t5: heap number map

  __ Branch(&entry);

  // Call into runtime if GC is required.

  __ bind(&gc_required);

  __ MultiPop(a0.bit() | a1.bit() | a2.bit() | a3.bit() | ra.bit());

  __ Branch(fail);

  __ bind(&loop);

  __ lw(a1, MemOperand(t0));

  __ Addu(t0, t0, kDoubleSize);

  // a1: current element's upper 32 bit

  // t0: address of next element's upper 32 bit

  __ Branch(&convert_hole, eq, a1, Operand(kHoleNanUpper32));

  // Non-hole double, copy value into a heap number.

  __ AllocateHeapNumber(a2, a0, t6, t5, &gc_required);

  // a2: new heap number

  __ lw(a0, MemOperand(t0, -12));

  __ sw(a0, FieldMemOperand(a2, HeapNumber::kMantissaOffset));

  __ sw(a1, FieldMemOperand(a2, HeapNumber::kExponentOffset));

  __ mov(a0, a3);

  __ sw(a2, MemOperand(a3));

  __ Addu(a3, a3, kIntSize);

  __ RecordWrite(t2,

                 a0,

                 a2,

                 kRAHasBeenSaved,

                 kDontSaveFPRegs,

                 EMIT_REMEMBERED_SET,

                 OMIT_SMI_CHECK);

  __ Branch(&entry);

  // Replace the-hole NaN with the-hole pointer.

  __ bind(&convert_hole);

  __ sw(t3, MemOperand(a3));

  __ Addu(a3, a3, kIntSize);

  __ bind(&entry);

  __ Branch(&loop, lt, a3, Operand(t1));

  __ MultiPop(a2.bit() | a3.bit() | a0.bit() | a1.bit());

  // Replace receiver's backing store with newly created and filled FixedArray.

  __ sw(t2, FieldMemOperand(a2, JSObject::kElementsOffset));

  __ RecordWriteField(a2,

                      JSObject::kElementsOffset,

                      t2,

                      t5,

                      kRAHasBeenSaved,

                      kDontSaveFPRegs,

                      EMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

  __ pop(ra);

  __ bind(&only_change_map);

  // Update receiver's map.

  __ sw(a3, FieldMemOperand(a2, HeapObject::kMapOffset));

  __ RecordWriteField(a2,

                      HeapObject::kMapOffset,

                      a3,

                      t5,

                      kRAHasNotBeenSaved,

                      kDontSaveFPRegs,

                      OMIT_REMEMBERED_SET,

                      OMIT_SMI_CHECK);

}

void StringCharLoadGenerator::Generate(MacroAssembler* masm,

                                       Register string,

                                       Register index,

                                       Register result,

                                       Label* call_runtime) {

  // Fetch the instance type of the receiver into result register.

  __ lw(result, FieldMemOperand(string, HeapObject::kMapOffset));

  __ lbu(result, FieldMemOperand(result, Map::kInstanceTypeOffset));

  // We need special handling for indirect strings.

  Label check_sequential;

  __ And(at, result, Operand(kIsIndirectStringMask));

  __ Branch(&check_sequential, eq, at, Operand(zero_reg));

  // Dispatch on the indirect string shape: slice or cons.

  Label cons_string;

  __ And(at, result, Operand(kSlicedNotConsMask));

  __ Branch(&cons_string, eq, at, Operand(zero_reg));

  // Handle slices.

  Label indirect_string_loaded;

  __ lw(result, FieldMemOperand(string, SlicedString::kOffsetOffset));

  __ lw(string, FieldMemOperand(string, SlicedString::kParentOffset));

  __ sra(at, result, kSmiTagSize);

  __ Addu(index, index, at);

  __ jmp(&indirect_string_loaded);

  // Handle cons strings.

  // Check whether the right hand side is the empty string (i.e. if

  // this is really a flat string in a cons string). If that is not

  // the case we would rather go to the runtime system now to flatten

  // the string.

  __ bind(&cons_string);

  __ lw(result, FieldMemOperand(string, ConsString::kSecondOffset));

  __ LoadRoot(at, Heap::kempty_stringRootIndex);

  __ Branch(call_runtime, ne, result, Operand(at));

  // Get the first of the two strings and load its instance type.

  __ lw(string, FieldMemOperand(string, ConsString::kFirstOffset));

  __ bind(&indirect_string_loaded);

  __ lw(result, FieldMemOperand(string, HeapObject::kMapOffset));

  __ lbu(result, FieldMemOperand(result, Map::kInstanceTypeOffset));

  // Distinguish sequential and external strings. Only these two string

  // representations can reach here (slices and flat cons strings have been

  // reduced to the underlying sequential or external string).

  Label external_string, check_encoding;

  __ bind(&check_sequential);

  STATIC_ASSERT(kSeqStringTag == 0);

  __ And(at, result, Operand(kStringRepresentationMask));

  __ Branch(&external_string, ne, at, Operand(zero_reg));

  // Prepare sequential strings

  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);

  __ Addu(string,

          string,

          SeqTwoByteString::kHeaderSize - kHeapObjectTag);

  __ jmp(&check_encoding);

  // Handle external strings.

  __ bind(&external_string);

  if (FLAG_debug_code) {

    // Assert that we do not have a cons or slice (indirect strings) here.

    // Sequential strings have already been ruled out.

    __ And(at, result, Operand(kIsIndirectStringMask));

    __ Assert(eq, kExternalStringExpectedButNotFound,

        at, Operand(zero_reg));

  }

  // Rule out short external strings.

  STATIC_CHECK(kShortExternalStringTag != 0);

  __ And(at, result, Operand(kShortExternalStringMask));

  __ Branch(call_runtime, ne, at, Operand(zero_reg));

  __ lw(string, FieldMemOperand(string, ExternalString::kResourceDataOffset));

  Label ascii, done;

  __ bind(&check_encoding);

  STATIC_ASSERT(kTwoByteStringTag == 0);

  __ And(at, result, Operand(kStringEncodingMask));

  __ Branch(&ascii, ne, at, Operand(zero_reg));

  // Two-byte string.

  __ sll(at, index, 1);

  __ Addu(at, string, at);

  __ lhu(result, MemOperand(at));

  __ jmp(&done);

  __ bind(&ascii);

  // Ascii string.

  __ Addu(at, string, index);

  __ lbu(result, MemOperand(at));

  __ bind(&done);

}

static MemOperand ExpConstant(int index, Register base) {

  return MemOperand(base, index * kDoubleSize);

}

void MathExpGenerator::EmitMathExp(MacroAssembler* masm,

                                   DoubleRegister input,

                                   DoubleRegister result,

                                   DoubleRegister double_scratch1,

                                   DoubleRegister double_scratch2,

                                   Register temp1,

                                   Register temp2,

                                   Register temp3) {

  ASSERT(!input.is(result));

  ASSERT(!input.is(double_scratch1));

  ASSERT(!input.is(double_scratch2));

  ASSERT(!result.is(double_scratch1));

  ASSERT(!result.is(double_scratch2));

  ASSERT(!double_scratch1.is(double_scratch2));

  ASSERT(!temp1.is(temp2));

  ASSERT(!temp1.is(temp3));

  ASSERT(!temp2.is(temp3));

  ASSERT(ExternalReference::math_exp_constants(0).address() != NULL);

  Label zero, infinity, done;

  __ li(temp3, Operand(ExternalReference::math_exp_constants(0)));

  __ ldc1(double_scratch1, ExpConstant(0, temp3));

  __ BranchF(&zero, NULL, ge, double_scratch1, input);

  __ ldc1(double_scratch2, ExpConstant(1, temp3));

  __ BranchF(&infinity, NULL, ge, input, double_scratch2);

  __ ldc1(double_scratch1, ExpConstant(3, temp3));

  __ ldc1(result, ExpConstant(4, temp3));

  __ mul_d(double_scratch1, double_scratch1, input);

  __ add_d(double_scratch1, double_scratch1, result);

  __ FmoveLow(temp2, double_scratch1);

  __ sub_d(double_scratch1, double_scratch1, result);

  __ ldc1(result, ExpConstant(6, temp3));

  __ ldc1(double_scratch2, ExpConstant(5, temp3));

  __ mul_d(double_scratch1, double_scratch1, double_scratch2);

  __ sub_d(double_scratch1, double_scratch1, input);

  __ sub_d(result, result, double_scratch1);

  __ mul_d(double_scratch2, double_scratch1, double_scratch1);

  __ mul_d(result, result, double_scratch2);

  __ ldc1(double_scratch2, ExpConstant(7, temp3));

  __ mul_d(result, result, double_scratch2);

  __ sub_d(result, result, double_scratch1);

  // Mov 1 in double_scratch2 as math_exp_constants_array[8] == 1.

  ASSERT(*reinterpret_cast<double*>

         (ExternalReference::math_exp_constants(8).address()) == 1);

  __ Move(double_scratch2, 1);

  __ add_d(result, result, double_scratch2);

  __ srl(temp1, temp2, 11);

  __ Ext(temp2, temp2, 0, 11);

  __ Addu(temp1, temp1, Operand(0x3ff));

  // Must not call ExpConstant() after overwriting temp3!

  __ li(temp3, Operand(ExternalReference::math_exp_log_table()));

  __ sll(at, temp2, 3);

  __ Addu(temp3, temp3, Operand(at));

  __ lw(temp2, MemOperand(temp3, 0));

  __ lw(temp3, MemOperand(temp3, kPointerSize));

  // The first word is loaded is the lower number register.

  if (temp2.code() < temp3.code()) {

    __ sll(at, temp1, 20);

    __ Or(temp1, temp3, at);

    __ Move(double_scratch1, temp2, temp1);

  } else {

    __ sll(at, temp1, 20);

    __ Or(temp1, temp2, at);

    __ Move(double_scratch1, temp3, temp1);

  }

  __ mul_d(result, result, double_scratch1);

  __ Branch(&done);

  __ bind(&zero);

  __ Move(result, kDoubleRegZero);

  __ Branch(&done);

  __ bind(&infinity);

  __ ldc1(result, ExpConstant(2, temp3));

  __ bind(&done);

}

// nop(CODE_AGE_MARKER_NOP)

static const uint32_t kCodeAgePatchFirstInstruction = 0x00010180;

static byte* GetNoCodeAgeSequence(uint32_t* length) {

  // The sequence of instructions that is patched out for aging code is the

  // following boilerplate stack-building prologue that is found in FUNCTIONS

  static bool initialized = false;

  static uint32_t sequence[kNoCodeAgeSequenceLength];

  byte* byte_sequence = reinterpret_cast<byte*>(sequence);

  *length = kNoCodeAgeSequenceLength * Assembler::kInstrSize;

  if (!initialized) {

    CodePatcher patcher(byte_sequence, kNoCodeAgeSequenceLength);

    patcher.masm()->Push(ra, fp, cp, a1);

    patcher.masm()->nop(Assembler::CODE_AGE_SEQUENCE_NOP);

    patcher.masm()->Addu(fp, sp, Operand(2 * kPointerSize));

    initialized = true;

  }

  return byte_sequence;

}

bool Code::IsYoungSequence(byte* sequence) {

  uint32_t young_length;

  byte* young_sequence = GetNoCodeAgeSequence(&young_length);

  bool result = !memcmp(sequence, young_sequence, young_length);

  ASSERT(result ||

         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction);

  return result;

}

void Code::GetCodeAgeAndParity(byte* sequence, Age* age,

                               MarkingParity* parity) {

  if (IsYoungSequence(sequence)) {

    *age = kNoAgeCodeAge;

    *parity = NO_MARKING_PARITY;

  } else {

    Address target_address = Memory::Address_at(

        sequence + Assembler::kInstrSize * (kNoCodeAgeSequenceLength - 1));

    Code* stub = GetCodeFromTargetAddress(target_address);

    GetCodeAgeAndParity(stub, age, parity);

  }

}

void Code::PatchPlatformCodeAge(Isolate* isolate,

                                byte* sequence,

                                Code::Age age,

                                MarkingParity parity) {

  uint32_t young_length;

  byte* young_sequence = GetNoCodeAgeSequence(&young_length);

  if (age == kNoAgeCodeAge) {

    CopyBytes(sequence, young_sequence, young_length);

    CPU::FlushICache(sequence, young_length);

  } else {

    Code* stub = GetCodeAgeStub(isolate, age, parity);

    CodePatcher patcher(sequence, young_length / Assembler::kInstrSize);

    // Mark this code sequence for FindPlatformCodeAgeSequence()

    patcher.masm()->nop(Assembler::CODE_AGE_MARKER_NOP);

    // Save the function's original return address

    // (it will be clobbered by Call(t9))

    patcher.masm()->mov(at, ra);

    // Load the stub address to t9 and call it

    patcher.masm()->li(t9,

        Operand(reinterpret_cast<uint32_t>(stub->instruction_start())));

    patcher.masm()->Call(t9);

    // Record the stub address in the empty space for GetCodeAgeAndParity()

    patcher.masm()->dd(reinterpret_cast<uint32_t>(stub->instruction_start()));

  }

}

#undef __

} }  // namespace v8::internal

#endif  // V8_TARGET_ARCH_MIPS