src/code-stubs.h

// 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.

#ifndef V8_CODE_STUBS_H_
#define V8_CODE_STUBS_H_

#include "allocation.h"
#include "assembler.h"
#include "codegen.h"
#include "globals.h"
#include "macro-assembler.h"

namespace v8 {
namespace internal {

// List of code stubs used on all platforms.
#define CODE_STUB_LIST_ALL_PLATFORMS(V)  \
  V(CallFunction)                        \
  V(CallConstruct)                       \
  V(BinaryOp)                            \
  V(StringAdd)                           \
  V(NewStringAdd)                        \
  V(SubString)                           \
  V(StringCompare)                       \
  V(Compare)                             \
  V(CompareIC)                           \
  V(CompareNilIC)                        \
  V(MathPow)                             \
  V(StringLength)                        \
  V(FunctionPrototype)                   \
  V(StoreArrayLength)                    \
  V(RecordWrite)                         \
  V(StoreBufferOverflow)                 \
  V(RegExpExec)                          \
  V(TranscendentalCache)                 \
  V(Instanceof)                          \
  V(ConvertToDouble)                     \
  V(WriteInt32ToHeapNumber)              \
  V(StackCheck)                          \
  V(Interrupt)                           \
  V(FastNewClosure)                      \
  V(FastNewContext)                      \
  V(FastNewBlockContext)                 \
  V(FastCloneShallowArray)               \
  V(FastCloneShallowObject)              \
  V(CreateAllocationSite)                \
  V(ToBoolean)                           \
  V(ToNumber)                            \
  V(ArgumentsAccess)                     \
  V(RegExpConstructResult)               \
  V(NumberToString)                      \
  V(DoubleToI)                           \
  V(CEntry)                              \
  V(JSEntry)                             \
  V(KeyedLoadElement)                    \
  V(ArrayNoArgumentConstructor)          \
  V(ArraySingleArgumentConstructor)      \
  V(ArrayNArgumentsConstructor)          \
  V(InternalArrayNoArgumentConstructor)  \
  V(InternalArraySingleArgumentConstructor)      \
  V(InternalArrayNArgumentsConstructor)  \
  V(KeyedStoreElement)                   \
  V(DebuggerStatement)                   \
  V(NameDictionaryLookup)                \
  V(ElementsTransitionAndStore)          \
  V(TransitionElementsKind)              \
  V(StoreArrayLiteralElement)            \
  V(StubFailureTrampoline)               \
  V(StubFailureTailCallTrampoline)       \
  V(ArrayConstructor)                    \
  V(InternalArrayConstructor)            \
  V(ProfileEntryHook)                    \
  V(StoreGlobal)                         \
  /* IC Handler stubs */                 \
  V(LoadField)                           \
  V(KeyedLoadField)                      \
  V(KeyedArrayCall)

// List of code stubs only used on ARM platforms.
#if V8_TARGET_ARCH_ARM
#define CODE_STUB_LIST_ARM(V)  \
  V(GetProperty)               \
  V(SetProperty)               \
  V(InvokeBuiltin)             \
  V(DirectCEntry)
#else
#define CODE_STUB_LIST_ARM(V)
#endif

// List of code stubs only used on MIPS platforms.
#if V8_TARGET_ARCH_MIPS
#define CODE_STUB_LIST_MIPS(V)  \
  V(RegExpCEntry)               \
  V(DirectCEntry)
#else
#define CODE_STUB_LIST_MIPS(V)
#endif

// Combined list of code stubs.
#define CODE_STUB_LIST(V)            \
  CODE_STUB_LIST_ALL_PLATFORMS(V)    \
  CODE_STUB_LIST_ARM(V)              \
  CODE_STUB_LIST_MIPS(V)

// Mode to overwrite BinaryExpression values.
enum OverwriteMode { NO_OVERWRITE, OVERWRITE_LEFT, OVERWRITE_RIGHT };

// Stub is base classes of all stubs.
class CodeStub BASE_EMBEDDED {
 public:
  enum Major {
#define DEF_ENUM(name) name,
    CODE_STUB_LIST(DEF_ENUM)
#undef DEF_ENUM
    NoCache,  // marker for stubs that do custom caching
    NUMBER_OF_IDS
  };

  // Retrieve the code for the stub. Generate the code if needed.
  Handle<Code> GetCode(Isolate* isolate);

  // Retrieve the code for the stub, make and return a copy of the code.
  Handle<Code> GetCodeCopyFromTemplate(Isolate* isolate);
  static Major MajorKeyFromKey(uint32_t key) {
    return static_cast<Major>(MajorKeyBits::decode(key));
  }
  static int MinorKeyFromKey(uint32_t key) {
    return MinorKeyBits::decode(key);
  }

  // Gets the major key from a code object that is a code stub or binary op IC.
  static Major GetMajorKey(Code* code_stub) {
    return static_cast<Major>(code_stub->major_key());
  }

  static const char* MajorName(Major major_key, bool allow_unknown_keys);

  virtual ~CodeStub() {}

  bool CompilingCallsToThisStubIsGCSafe(Isolate* isolate) {
    bool is_pregenerated = IsPregenerated(isolate);
    Code* code = NULL;
    CHECK(!is_pregenerated || FindCodeInCache(&code, isolate));
    return is_pregenerated;
  }

  // See comment above, where Instanceof is defined.
  virtual bool IsPregenerated(Isolate* isolate) { return false; }

  static void GenerateStubsAheadOfTime(Isolate* isolate);
  static void GenerateStubsRequiringBuiltinsAheadOfTime(Isolate* isolate);
  static void GenerateFPStubs(Isolate* isolate);

  // Some stubs put untagged junk on the stack that cannot be scanned by the
  // GC.  This means that we must be statically sure that no GC can occur while
  // they are running.  If that is the case they should override this to return
  // true, which will cause an assertion if we try to call something that can
  // GC or if we try to put a stack frame on top of the junk, which would not
  // result in a traversable stack.
  virtual bool SometimesSetsUpAFrame() { return true; }

  // Lookup the code in the (possibly custom) cache.
  bool FindCodeInCache(Code** code_out, Isolate* isolate);

  // Returns information for computing the number key.
  virtual Major MajorKey() = 0;
  virtual int MinorKey() = 0;

  virtual InlineCacheState GetICState() {
    return UNINITIALIZED;
  }
  virtual ExtraICState GetExtraICState() {
    return kNoExtraICState;
  }
  virtual Code::StubType GetStubType() {
    return Code::NORMAL;
  }
  virtual int GetStubFlags() {
    return -1;
  }

  virtual void PrintName(StringStream* stream);

  // Returns a name for logging/debugging purposes.
  SmartArrayPointer<const char> GetName();

 protected:
  static bool CanUseFPRegisters();

  // Generates the assembler code for the stub.
  virtual Handle<Code> GenerateCode(Isolate* isolate) = 0;

  virtual void VerifyPlatformFeatures(Isolate* isolate);

  // Returns whether the code generated for this stub needs to be allocated as
  // a fixed (non-moveable) code object.
  virtual bool NeedsImmovableCode() { return false; }

  virtual void PrintBaseName(StringStream* stream);
  virtual void PrintState(StringStream* stream) { }

 private:
  // Perform bookkeeping required after code generation when stub code is
  // initially generated.
  void RecordCodeGeneration(Code* code, Isolate* isolate);

  // Finish the code object after it has been generated.
  virtual void FinishCode(Handle<Code> code) { }

  // Activate newly generated stub. Is called after
  // registering stub in the stub cache.
  virtual void Activate(Code* code) { }

  // BinaryOpStub needs to override this.
  virtual Code::Kind GetCodeKind() const;

  // Add the code to a specialized cache, specific to an individual
  // stub type. Please note, this method must add the code object to a
  // roots object, otherwise we will remove the code during GC.
  virtual void AddToSpecialCache(Handle<Code> new_object) { }

  // Find code in a specialized cache, work is delegated to the specific stub.
  virtual bool FindCodeInSpecialCache(Code** code_out, Isolate* isolate) {
    return false;
  }

  // If a stub uses a special cache override this.
  virtual bool UseSpecialCache() { return false; }

  // Computes the key based on major and minor.
  uint32_t GetKey() {
    ASSERT(static_cast<int>(MajorKey()) < NUMBER_OF_IDS);
    return MinorKeyBits::encode(MinorKey()) |
           MajorKeyBits::encode(MajorKey());
  }

  class MajorKeyBits: public BitField<uint32_t, 0, kStubMajorKeyBits> {};
  class MinorKeyBits: public BitField<uint32_t,
      kStubMajorKeyBits, kStubMinorKeyBits> {};  // NOLINT

  friend class BreakPointIterator;
};


class PlatformCodeStub : public CodeStub {
 public:
  // Retrieve the code for the stub. Generate the code if needed.
  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual Code::Kind GetCodeKind() const { return Code::STUB; }

 protected:
  // Generates the assembler code for the stub.
  virtual void Generate(MacroAssembler* masm) = 0;
};


enum StubFunctionMode { NOT_JS_FUNCTION_STUB_MODE, JS_FUNCTION_STUB_MODE };
enum HandlerArgumentsMode { DONT_PASS_ARGUMENTS, PASS_ARGUMENTS };

enum ContinuationType { NORMAL_CONTINUATION, TAIL_CALL_CONTINUATION };


struct CodeStubInterfaceDescriptor {
  CodeStubInterfaceDescriptor();
  int register_param_count_;

  Register stack_parameter_count_;
  // if hint_stack_parameter_count_ > 0, the code stub can optimize the
  // return sequence. Default value is -1, which means it is ignored.
  int hint_stack_parameter_count_;
  ContinuationType continuation_type_;
  StubFunctionMode function_mode_;
  Register* register_params_;

  Address deoptimization_handler_;
  HandlerArgumentsMode handler_arguments_mode_;

  bool initialized() const { return register_param_count_ >= 0; }

  bool HasTailCallContinuation() const {
    return continuation_type_ == TAIL_CALL_CONTINUATION;
  }

  int environment_length() const {
    return register_param_count_;
  }

  void SetMissHandler(ExternalReference handler) {
    miss_handler_ = handler;
    has_miss_handler_ = true;
    // Our miss handler infrastructure doesn't currently support
    // variable stack parameter counts.
    ASSERT(!stack_parameter_count_.is_valid());
  }

  ExternalReference miss_handler() {
    ASSERT(has_miss_handler_);
    return miss_handler_;
  }

  bool has_miss_handler() {
    return has_miss_handler_;
  }

  Register GetParameterRegister(int index) {
    return register_params_[index];
  }

  bool IsParameterCountRegister(int index) {
    return GetParameterRegister(index).is(stack_parameter_count_);
  }

  int GetHandlerParameterCount() {
    int params = environment_length();
    if (handler_arguments_mode_ == PASS_ARGUMENTS) {
      params += 1;
    }
    return params;
  }

 private:
  ExternalReference miss_handler_;
  bool has_miss_handler_;
};


class HydrogenCodeStub : public CodeStub {
 public:
  enum InitializationState {
    UNINITIALIZED,
    INITIALIZED
  };

  explicit HydrogenCodeStub(InitializationState state = INITIALIZED) {
    is_uninitialized_ = (state == UNINITIALIZED);
  }

  virtual Code::Kind GetCodeKind() const { return Code::STUB; }

  CodeStubInterfaceDescriptor* GetInterfaceDescriptor(Isolate* isolate) {
    return isolate->code_stub_interface_descriptor(MajorKey());
  }

  bool IsUninitialized() { return is_uninitialized_; }

  template<class SubClass>
  static Handle<Code> GetUninitialized(Isolate* isolate) {
    SubClass::GenerateAheadOfTime(isolate);
    return SubClass().GetCode(isolate);
  }

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor) = 0;

  // Retrieve the code for the stub. Generate the code if needed.
  virtual Handle<Code> GenerateCode(Isolate* isolate) = 0;

  virtual int NotMissMinorKey() = 0;

  Handle<Code> GenerateLightweightMissCode(Isolate* isolate);

  template<class StateType>
  void TraceTransition(StateType from, StateType to);

 private:
  class MinorKeyBits: public BitField<int, 0, kStubMinorKeyBits - 1> {};
  class IsMissBits: public BitField<bool, kStubMinorKeyBits - 1, 1> {};

  void GenerateLightweightMiss(MacroAssembler* masm);
  virtual int MinorKey() {
    return IsMissBits::encode(is_uninitialized_) |
        MinorKeyBits::encode(NotMissMinorKey());
  }

  bool is_uninitialized_;
};


// Helper interface to prepare to/restore after making runtime calls.
class RuntimeCallHelper {
 public:
  virtual ~RuntimeCallHelper() {}

  virtual void BeforeCall(MacroAssembler* masm) const = 0;

  virtual void AfterCall(MacroAssembler* masm) const = 0;

 protected:
  RuntimeCallHelper() {}

 private:
  DISALLOW_COPY_AND_ASSIGN(RuntimeCallHelper);
};


// TODO(bmeurer): Move to the StringAddStub declaration once we're
// done with the translation to a hydrogen code stub.
enum StringAddFlags {
  // Omit both parameter checks.
  STRING_ADD_CHECK_NONE = 0,
  // Check left parameter.
  STRING_ADD_CHECK_LEFT = 1 << 0,
  // Check right parameter.
  STRING_ADD_CHECK_RIGHT = 1 << 1,
  // Check both parameters.
  STRING_ADD_CHECK_BOTH = STRING_ADD_CHECK_LEFT | STRING_ADD_CHECK_RIGHT
};

} }  // namespace v8::internal

#if V8_TARGET_ARCH_IA32
#include "ia32/code-stubs-ia32.h"
#elif V8_TARGET_ARCH_X64
#include "x64/code-stubs-x64.h"
#elif V8_TARGET_ARCH_ARM
#include "arm/code-stubs-arm.h"
#elif V8_TARGET_ARCH_MIPS
#include "mips/code-stubs-mips.h"
#else
#error Unsupported target architecture.
#endif

namespace v8 {
namespace internal {


// RuntimeCallHelper implementation used in stubs: enters/leaves a
// newly created internal frame before/after the runtime call.
class StubRuntimeCallHelper : public RuntimeCallHelper {
 public:
  StubRuntimeCallHelper() {}

  virtual void BeforeCall(MacroAssembler* masm) const;

  virtual void AfterCall(MacroAssembler* masm) const;
};


// Trivial RuntimeCallHelper implementation.
class NopRuntimeCallHelper : public RuntimeCallHelper {
 public:
  NopRuntimeCallHelper() {}

  virtual void BeforeCall(MacroAssembler* masm) const {}

  virtual void AfterCall(MacroAssembler* masm) const {}
};


class ToNumberStub: public HydrogenCodeStub {
 public:
  ToNumberStub() { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return ToNumber; }
  int NotMissMinorKey() { return 0; }
};


class NumberToStringStub V8_FINAL : public HydrogenCodeStub {
 public:
  NumberToStringStub() {}

  virtual Handle<Code> GenerateCode(Isolate* isolate) V8_OVERRIDE;

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor) V8_OVERRIDE;

  static void InstallDescriptors(Isolate* isolate);

  // Parameters accessed via CodeStubGraphBuilder::GetParameter()
  static const int kNumber = 0;

 private:
  virtual Major MajorKey() V8_OVERRIDE { return NumberToString; }
  virtual int NotMissMinorKey() V8_OVERRIDE { return 0; }
};


class FastNewClosureStub : public HydrogenCodeStub {
 public:
  explicit FastNewClosureStub(LanguageMode language_mode, bool is_generator)
    : language_mode_(language_mode),
      is_generator_(is_generator) { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  static void InstallDescriptors(Isolate* isolate);

  LanguageMode language_mode() const { return language_mode_; }
  bool is_generator() const { return is_generator_; }

 private:
  class StrictModeBits: public BitField<bool, 0, 1> {};
  class IsGeneratorBits: public BitField<bool, 1, 1> {};

  Major MajorKey() { return FastNewClosure; }
  int NotMissMinorKey() {
    return StrictModeBits::encode(language_mode_ != CLASSIC_MODE) |
      IsGeneratorBits::encode(is_generator_);
  }

  LanguageMode language_mode_;
  bool is_generator_;
};


class FastNewContextStub : public PlatformCodeStub {
 public:
  static const int kMaximumSlots = 64;

  explicit FastNewContextStub(int slots) : slots_(slots) {
    ASSERT(slots_ > 0 && slots_ <= kMaximumSlots);
  }

  void Generate(MacroAssembler* masm);

 private:
  int slots_;

  Major MajorKey() { return FastNewContext; }
  int MinorKey() { return slots_; }
};


class FastNewBlockContextStub : public PlatformCodeStub {
 public:
  static const int kMaximumSlots = 64;

  explicit FastNewBlockContextStub(int slots) : slots_(slots) {
    ASSERT(slots_ > 0 && slots_ <= kMaximumSlots);
  }

  void Generate(MacroAssembler* masm);

 private:
  int slots_;

  Major MajorKey() { return FastNewBlockContext; }
  int MinorKey() { return slots_; }
};

class FastCloneShallowArrayStub : public HydrogenCodeStub {
 public:
  // Maximum length of copied elements array.
  static const int kMaximumClonedLength = 8;
  enum Mode {
    CLONE_ELEMENTS,
    CLONE_DOUBLE_ELEMENTS,
    COPY_ON_WRITE_ELEMENTS,
    CLONE_ANY_ELEMENTS,
    LAST_CLONE_MODE = CLONE_ANY_ELEMENTS
  };

  static const int kFastCloneModeCount = LAST_CLONE_MODE + 1;

  FastCloneShallowArrayStub(Mode mode,
                            AllocationSiteMode allocation_site_mode,
                            int length)
      : mode_(mode),
        allocation_site_mode_(allocation_site_mode),
        length_((mode == COPY_ON_WRITE_ELEMENTS) ? 0 : length) {
    ASSERT_GE(length_, 0);
    ASSERT_LE(length_, kMaximumClonedLength);
  }

  Mode mode() const { return mode_; }
  int length() const { return length_; }
  AllocationSiteMode allocation_site_mode() const {
    return allocation_site_mode_;
  }

  ElementsKind ComputeElementsKind() const {
    switch (mode()) {
      case CLONE_ELEMENTS:
      case COPY_ON_WRITE_ELEMENTS:
        return FAST_ELEMENTS;
      case CLONE_DOUBLE_ELEMENTS:
        return FAST_DOUBLE_ELEMENTS;
      case CLONE_ANY_ELEMENTS:
        /*fall-through*/;
    }
    UNREACHABLE();
    return LAST_ELEMENTS_KIND;
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Mode mode_;
  AllocationSiteMode allocation_site_mode_;
  int length_;

  class AllocationSiteModeBits: public BitField<AllocationSiteMode, 0, 1> {};
  class ModeBits: public BitField<Mode, 1, 4> {};
  class LengthBits: public BitField<int, 5, 4> {};
  // Ensure data fits within available bits.
  STATIC_ASSERT(LAST_ALLOCATION_SITE_MODE == 1);
  STATIC_ASSERT(kFastCloneModeCount < 16);
  STATIC_ASSERT(kMaximumClonedLength < 16);
  Major MajorKey() { return FastCloneShallowArray; }
  int NotMissMinorKey() {
    return AllocationSiteModeBits::encode(allocation_site_mode_)
        | ModeBits::encode(mode_)
        | LengthBits::encode(length_);
  }
};


class FastCloneShallowObjectStub : public HydrogenCodeStub {
 public:
  // Maximum number of properties in copied object.
  static const int kMaximumClonedProperties = 6;

  explicit FastCloneShallowObjectStub(int length)
      : length_(length) {
    ASSERT_GE(length_, 0);
    ASSERT_LE(length_, kMaximumClonedProperties);
  }

  int length() const { return length_; }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  int length_;

  Major MajorKey() { return FastCloneShallowObject; }
  int NotMissMinorKey() { return length_; }

  DISALLOW_COPY_AND_ASSIGN(FastCloneShallowObjectStub);
};


class CreateAllocationSiteStub : public HydrogenCodeStub {
 public:
  explicit CreateAllocationSiteStub() { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE { return true; }

  static void GenerateAheadOfTime(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return CreateAllocationSite; }
  int NotMissMinorKey() { return 0; }

  DISALLOW_COPY_AND_ASSIGN(CreateAllocationSiteStub);
};


class InstanceofStub: public PlatformCodeStub {
 public:
  enum Flags {
    kNoFlags = 0,
    kArgsInRegisters = 1 << 0,
    kCallSiteInlineCheck = 1 << 1,
    kReturnTrueFalseObject = 1 << 2
  };

  explicit InstanceofStub(Flags flags) : flags_(flags) { }

  static Register left();
  static Register right();

  void Generate(MacroAssembler* masm);

 private:
  Major MajorKey() { return Instanceof; }
  int MinorKey() { return static_cast<int>(flags_); }

  bool HasArgsInRegisters() const {
    return (flags_ & kArgsInRegisters) != 0;
  }

  bool HasCallSiteInlineCheck() const {
    return (flags_ & kCallSiteInlineCheck) != 0;
  }

  bool ReturnTrueFalseObject() const {
    return (flags_ & kReturnTrueFalseObject) != 0;
  }

  virtual void PrintName(StringStream* stream);

  Flags flags_;
};


enum AllocationSiteOverrideMode {
  DONT_OVERRIDE,
  DISABLE_ALLOCATION_SITES,
  LAST_ALLOCATION_SITE_OVERRIDE_MODE = DISABLE_ALLOCATION_SITES
};


class ArrayConstructorStub: public PlatformCodeStub {
 public:
  enum ArgumentCountKey { ANY, NONE, ONE, MORE_THAN_ONE };
  ArrayConstructorStub(Isolate* isolate, int argument_count);
  explicit ArrayConstructorStub(Isolate* isolate);

  void Generate(MacroAssembler* masm);

 private:
  void GenerateDispatchToArrayStub(MacroAssembler* masm,
                                   AllocationSiteOverrideMode mode);

  virtual CodeStub::Major MajorKey() { return ArrayConstructor; }
  virtual int MinorKey() { return argument_count_; }

  ArgumentCountKey argument_count_;
};


class InternalArrayConstructorStub: public PlatformCodeStub {
 public:
  explicit InternalArrayConstructorStub(Isolate* isolate);

  void Generate(MacroAssembler* masm);

 private:
  virtual CodeStub::Major MajorKey() { return InternalArrayConstructor; }
  virtual int MinorKey() { return 0; }

  void GenerateCase(MacroAssembler* masm, ElementsKind kind);
};


class MathPowStub: public PlatformCodeStub {
 public:
  enum ExponentType { INTEGER, DOUBLE, TAGGED, ON_STACK };

  explicit MathPowStub(ExponentType exponent_type)
      : exponent_type_(exponent_type) { }
  virtual void Generate(MacroAssembler* masm);

 private:
  virtual CodeStub::Major MajorKey() { return MathPow; }
  virtual int MinorKey() { return exponent_type_; }

  ExponentType exponent_type_;
};


class ICStub: public PlatformCodeStub {
 public:
  explicit ICStub(Code::Kind kind) : kind_(kind) { }
  virtual Code::Kind GetCodeKind() const { return kind_; }
  virtual InlineCacheState GetICState() { return MONOMORPHIC; }

  bool Describes(Code* code) {
    return GetMajorKey(code) == MajorKey() && code->stub_info() == MinorKey();
  }

 protected:
  class KindBits: public BitField<Code::Kind, 0, 4> {};
  virtual void FinishCode(Handle<Code> code) {
    code->set_stub_info(MinorKey());
  }
  Code::Kind kind() { return kind_; }

  virtual int MinorKey() {
    return KindBits::encode(kind_);
  }

 private:
  Code::Kind kind_;
};


class FunctionPrototypeStub: public ICStub {
 public:
  explicit FunctionPrototypeStub(Code::Kind kind) : ICStub(kind) { }
  virtual void Generate(MacroAssembler* masm);

 private:
  virtual CodeStub::Major MajorKey() { return FunctionPrototype; }
};


class StringLengthStub: public ICStub {
 public:
  explicit StringLengthStub(Code::Kind kind) : ICStub(kind) { }
  virtual void Generate(MacroAssembler* masm);

 private:
  STATIC_ASSERT(KindBits::kSize == 4);
    virtual CodeStub::Major MajorKey() { return StringLength; }
};


class StoreICStub: public ICStub {
 public:
  StoreICStub(Code::Kind kind, StrictModeFlag strict_mode)
      : ICStub(kind), strict_mode_(strict_mode) { }

 protected:
  virtual ExtraICState GetExtraICState() {
    return StoreIC::ComputeExtraICState(strict_mode_);
  }

 private:
  STATIC_ASSERT(KindBits::kSize == 4);
  class StrictModeBits: public BitField<bool, 4, 1> {};
  virtual int MinorKey() {
    return KindBits::encode(kind()) | StrictModeBits::encode(strict_mode_);
  }

  StrictModeFlag strict_mode_;
};


class StoreArrayLengthStub: public StoreICStub {
 public:
  explicit StoreArrayLengthStub(Code::Kind kind, StrictModeFlag strict_mode)
      : StoreICStub(kind, strict_mode) { }
  virtual void Generate(MacroAssembler* masm);

 private:
  virtual CodeStub::Major MajorKey() { return StoreArrayLength; }
};


class HICStub: public HydrogenCodeStub {
 public:
  virtual Code::Kind GetCodeKind() const { return kind(); }
  virtual InlineCacheState GetICState() { return MONOMORPHIC; }

 protected:
  class KindBits: public BitField<Code::Kind, 0, 4> {};
  virtual Code::Kind kind() const = 0;
};


class HandlerStub: public HICStub {
 public:
  virtual Code::Kind GetCodeKind() const { return Code::HANDLER; }
  virtual int GetStubFlags() { return kind(); }

 protected:
  HandlerStub() : HICStub() { }
  virtual int NotMissMinorKey() { return bit_field_; }
  int bit_field_;
};


class LoadFieldStub: public HandlerStub {
 public:
  LoadFieldStub(bool inobject, int index, Representation representation) {
    Initialize(Code::LOAD_IC, inobject, index, representation);
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  Representation representation() {
    if (unboxed_double()) return Representation::Double();
    return Representation::Tagged();
  }

  virtual Code::Kind kind() const {
    return KindBits::decode(bit_field_);
  }

  bool is_inobject() {
    return InobjectBits::decode(bit_field_);
  }

  int offset() {
    int index = IndexBits::decode(bit_field_);
    int offset = index * kPointerSize;
    if (is_inobject()) return offset;
    return FixedArray::kHeaderSize + offset;
  }

  bool unboxed_double() {
    return UnboxedDoubleBits::decode(bit_field_);
  }

  virtual Code::StubType GetStubType() { return Code::FAST; }

 protected:
  LoadFieldStub() : HandlerStub() { }

  void Initialize(Code::Kind kind,
                  bool inobject,
                  int index,
                  Representation representation) {
    bool unboxed_double = FLAG_track_double_fields && representation.IsDouble();
    bit_field_ = KindBits::encode(kind)
        | InobjectBits::encode(inobject)
        | IndexBits::encode(index)
        | UnboxedDoubleBits::encode(unboxed_double);
  }

 private:
  STATIC_ASSERT(KindBits::kSize == 4);
  class InobjectBits: public BitField<bool, 4, 1> {};
  class IndexBits: public BitField<int, 5, 11> {};
  class UnboxedDoubleBits: public BitField<bool, 16, 1> {};
  virtual CodeStub::Major MajorKey() { return LoadField; }
};


class StoreGlobalStub : public HandlerStub {
 public:
  explicit StoreGlobalStub(bool is_constant) {
    bit_field_ = IsConstantBits::encode(is_constant);
  }

  Handle<Code> GetCodeCopyFromTemplate(Isolate* isolate,
                                       Map* receiver_map,
                                       PropertyCell* cell) {
    Handle<Code> code = CodeStub::GetCodeCopyFromTemplate(isolate);
    // Replace the placeholder cell and global object map with the actual global
    // cell and receiver map.
    Map* cell_map = isolate->heap()->global_property_cell_map();
    code->ReplaceNthObject(1, cell_map, cell);
    code->ReplaceNthObject(1, isolate->heap()->meta_map(), receiver_map);
    return code;
  }

  virtual Code::Kind kind() const { return Code::STORE_IC; }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  virtual ExtraICState GetExtraICState() { return bit_field_; }

  bool is_constant() {
    return IsConstantBits::decode(bit_field_);
  }
  void set_is_constant(bool value) {
    bit_field_ = IsConstantBits::update(bit_field_, value);
  }

  Representation representation() {
    return Representation::FromKind(RepresentationBits::decode(bit_field_));
  }
  void set_representation(Representation r) {
    bit_field_ = RepresentationBits::update(bit_field_, r.kind());
  }

 private:
  virtual int NotMissMinorKey() { return GetExtraICState(); }
  Major MajorKey() { return StoreGlobal; }

  class IsConstantBits: public BitField<bool, 0, 1> {};
  class RepresentationBits: public BitField<Representation::Kind, 1, 8> {};

  int bit_field_;

  DISALLOW_COPY_AND_ASSIGN(StoreGlobalStub);
};


class KeyedLoadFieldStub: public LoadFieldStub {
 public:
  KeyedLoadFieldStub(bool inobject, int index, Representation representation)
      : LoadFieldStub() {
    Initialize(Code::KEYED_LOAD_IC, inobject, index, representation);
  }

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  virtual Handle<Code> GenerateCode(Isolate* isolate);

 private:
  virtual CodeStub::Major MajorKey() { return KeyedLoadField; }
};


class KeyedArrayCallStub: public HICStub {
 public:
  KeyedArrayCallStub(bool holey, int argc) : HICStub(), argc_(argc) {
    bit_field_ = ContextualBits::encode(false) | HoleyBits::encode(holey);
  }

  virtual Code::Kind kind() const { return Code::KEYED_CALL_IC; }
  virtual ExtraICState GetExtraICState() { return bit_field_; }

  ElementsKind elements_kind() {
    return HoleyBits::decode(bit_field_) ? FAST_HOLEY_ELEMENTS : FAST_ELEMENTS;
  }

  int argc() { return argc_; }
  virtual int GetStubFlags() { return argc(); }

  static bool IsHoley(Handle<Code> code) {
    ExtraICState state = code->extra_ic_state();
    return HoleyBits::decode(state);
  }

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  virtual Handle<Code> GenerateCode(Isolate* isolate);

 private:
  virtual int NotMissMinorKey() {
    return GetExtraICState() | ArgcBits::encode(argc_);
  }

  class ContextualBits: public BitField<bool, 0, 1> {};
  STATIC_ASSERT(CallICBase::Contextual::kShift == ContextualBits::kShift);
  STATIC_ASSERT(CallICBase::Contextual::kSize == ContextualBits::kSize);
  class HoleyBits: public BitField<bool, 1, 1> {};
  STATIC_ASSERT(Code::kArgumentsBits <= kStubMinorKeyBits - 2);
  class ArgcBits: public BitField<int, 2, Code::kArgumentsBits> {};
  virtual CodeStub::Major MajorKey() { return KeyedArrayCall; }
  int bit_field_;
  int argc_;
};


class BinaryOpStub: public HydrogenCodeStub {
 public:
  BinaryOpStub(Token::Value op, OverwriteMode mode)
      : HydrogenCodeStub(UNINITIALIZED), op_(op), mode_(mode) {
    ASSERT(op <= LAST_TOKEN && op >= FIRST_TOKEN);
    Initialize();
  }

  explicit BinaryOpStub(ExtraICState state)
      : op_(decode_token(OpBits::decode(state))),
        mode_(OverwriteModeField::decode(state)),
        fixed_right_arg_(
            Maybe<int>(HasFixedRightArgBits::decode(state),
                decode_arg_value(FixedRightArgValueBits::decode(state)))),
        left_state_(LeftStateField::decode(state)),
        right_state_(fixed_right_arg_.has_value
            ? ((fixed_right_arg_.value <= Smi::kMaxValue) ? SMI : INT32)
            : RightStateField::decode(state)),
        result_state_(ResultStateField::decode(state)) {
    // We don't deserialize the SSE2 Field, since this is only used to be able
    // to include SSE2 as well as non-SSE2 versions in the snapshot. For code
    // generation we always want it to reflect the current state.
    ASSERT(!fixed_right_arg_.has_value ||
           can_encode_arg_value(fixed_right_arg_.value));
  }

  static const int FIRST_TOKEN = Token::BIT_OR;
  static const int LAST_TOKEN = Token::MOD;

  static void GenerateAheadOfTime(Isolate* isolate);
  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate, CodeStubInterfaceDescriptor* descriptor);
  static void InitializeForIsolate(Isolate* isolate) {
    BinaryOpStub binopStub(UNINITIALIZED);
    binopStub.InitializeInterfaceDescriptor(
        isolate, isolate->code_stub_interface_descriptor(CodeStub::BinaryOp));
  }

  virtual Code::Kind GetCodeKind() const { return Code::BINARY_OP_IC; }
  virtual InlineCacheState GetICState() {
    if (Max(left_state_, right_state_) == NONE) {
      return ::v8::internal::UNINITIALIZED;
    }
    if (Max(left_state_, right_state_) == GENERIC) return MEGAMORPHIC;
    return MONOMORPHIC;
  }

  virtual void VerifyPlatformFeatures(Isolate* isolate) V8_OVERRIDE {
    ASSERT(CpuFeatures::VerifyCrossCompiling(SSE2));
  }

  virtual ExtraICState GetExtraICState() {
    bool sse_field = Max(result_state_, Max(left_state_, right_state_)) > SMI &&
                     CpuFeatures::IsSafeForSnapshot(SSE2);

    return OpBits::encode(encode_token(op_))
         | LeftStateField::encode(left_state_)
         | RightStateField::encode(fixed_right_arg_.has_value
                                       ? NONE : right_state_)
         | ResultStateField::encode(result_state_)
         | HasFixedRightArgBits::encode(fixed_right_arg_.has_value)
         | FixedRightArgValueBits::encode(fixed_right_arg_.has_value
                                              ? encode_arg_value(
                                                  fixed_right_arg_.value)
                                              : 0)
         | SSE2Field::encode(sse_field)
         | OverwriteModeField::encode(mode_);
  }

  bool CanReuseDoubleBox() {
    return result_state_ <= NUMBER && result_state_ > SMI &&
      ((left_state_ > SMI && left_state_ <= NUMBER &&
        mode_ == OVERWRITE_LEFT) ||
       (right_state_ > SMI && right_state_ <= NUMBER &&
        mode_ == OVERWRITE_RIGHT));
  }

  bool HasSideEffects(Isolate* isolate) const {
    Handle<Type> left = GetLeftType(isolate);
    Handle<Type> right = GetRightType(isolate);
    return left->Maybe(Type::Receiver()) || right->Maybe(Type::Receiver());
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  Maybe<Handle<Object> > Result(Handle<Object> left,
                         Handle<Object> right,
                         Isolate* isolate);

  Token::Value operation() const { return op_; }
  OverwriteMode mode() const { return mode_; }
  Maybe<int> fixed_right_arg() const { return fixed_right_arg_; }

  Handle<Type> GetLeftType(Isolate* isolate) const;
  Handle<Type> GetRightType(Isolate* isolate) const;
  Handle<Type> GetResultType(Isolate* isolate) const;

  void UpdateStatus(Handle<Object> left,
                    Handle<Object> right,
                    Maybe<Handle<Object> > result);

  void PrintState(StringStream* stream);

 private:
  explicit BinaryOpStub(InitializationState state) : HydrogenCodeStub(state),
                                                     op_(Token::ADD),
                                                     mode_(NO_OVERWRITE) {
    Initialize();
  }
  void Initialize();

  enum State { NONE, SMI, INT32, NUMBER, STRING, GENERIC };

  // We truncate the last bit of the token.
  STATIC_ASSERT(LAST_TOKEN - FIRST_TOKEN < (1 << 5));
  class LeftStateField:         public BitField<State, 0,  3> {};
  // When fixed right arg is set, we don't need to store the right state.
  // Thus the two fields can overlap.
  class HasFixedRightArgBits:   public BitField<bool, 4, 1> {};
  class FixedRightArgValueBits: public BitField<int,  5, 4> {};
  class RightStateField:        public BitField<State, 5, 3> {};
  class ResultStateField:       public BitField<State, 9, 3> {};
  class SSE2Field:              public BitField<bool, 12, 1> {};
  class OverwriteModeField:     public BitField<OverwriteMode, 13, 2> {};
  class OpBits:                 public BitField<int, 15,  5> {};

  virtual CodeStub::Major MajorKey() { return BinaryOp; }
  virtual int NotMissMinorKey() { return GetExtraICState(); }

  static Handle<Type> StateToType(State state,
                                  Isolate* isolate);

  static void Generate(Token::Value op,
                       State left,
                       int right,
                       State result,
                       OverwriteMode mode,
                       Isolate* isolate);

  static void Generate(Token::Value op,
                       State left,
                       State right,
                       State result,
                       OverwriteMode mode,
                       Isolate* isolate);

  void UpdateStatus(Handle<Object> object,
                    State* state);

  bool can_encode_arg_value(int32_t value) const;
  int encode_arg_value(int32_t value) const;
  int32_t decode_arg_value(int value)  const;
  int encode_token(Token::Value op) const;
  Token::Value decode_token(int op) const;

  bool has_int_result() const {
    return op_ == Token::BIT_XOR || op_ == Token::BIT_AND ||
           op_ == Token::BIT_OR || op_ == Token::SAR || op_ == Token::SHL;
  }

  const char* StateToName(State state);

  void PrintBaseName(StringStream* stream);

  Token::Value op_;
  OverwriteMode mode_;

  Maybe<int> fixed_right_arg_;
  State left_state_;
  State right_state_;
  State result_state_;
};


// TODO(bmeurer): Rename to StringAddStub once we dropped the old StringAddStub.
class NewStringAddStub V8_FINAL : public HydrogenCodeStub {
 public:
  NewStringAddStub(StringAddFlags flags, PretenureFlag pretenure_flag)
      : bit_field_(StringAddFlagsBits::encode(flags) |
                   PretenureFlagBits::encode(pretenure_flag)) {}

  StringAddFlags flags() const {
    return StringAddFlagsBits::decode(bit_field_);
  }

  PretenureFlag pretenure_flag() const {
    return PretenureFlagBits::decode(bit_field_);
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate) V8_OVERRIDE;

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor) V8_OVERRIDE;

  static void InstallDescriptors(Isolate* isolate);

  // Parameters accessed via CodeStubGraphBuilder::GetParameter()
  static const int kLeft = 0;
  static const int kRight = 1;

 private:
  class StringAddFlagsBits: public BitField<StringAddFlags, 0, 2> {};
  class PretenureFlagBits: public BitField<PretenureFlag, 2, 1> {};
  uint32_t bit_field_;

  virtual Major MajorKey() V8_OVERRIDE { return NewStringAdd; }
  virtual int NotMissMinorKey() V8_OVERRIDE { return bit_field_; }

  virtual void PrintBaseName(StringStream* stream) V8_OVERRIDE;

  DISALLOW_COPY_AND_ASSIGN(NewStringAddStub);
};


class ICCompareStub: public PlatformCodeStub {
 public:
  ICCompareStub(Token::Value op,
                CompareIC::State left,
                CompareIC::State right,
                CompareIC::State handler)
      : op_(op),
        left_(left),
        right_(right),
        state_(handler) {
    ASSERT(Token::IsCompareOp(op));
  }

  virtual void Generate(MacroAssembler* masm);

  void set_known_map(Handle<Map> map) { known_map_ = map; }

  static void DecodeMinorKey(int minor_key,
                             CompareIC::State* left_state,
                             CompareIC::State* right_state,
                             CompareIC::State* handler_state,
                             Token::Value* op);

  static CompareIC::State CompareState(int minor_key) {
    return static_cast<CompareIC::State>(HandlerStateField::decode(minor_key));
  }

  virtual InlineCacheState GetICState();

 private:
  class OpField: public BitField<int, 0, 3> { };
  class LeftStateField: public BitField<int, 3, 4> { };
  class RightStateField: public BitField<int, 7, 4> { };
  class HandlerStateField: public BitField<int, 11, 4> { };

  virtual void FinishCode(Handle<Code> code) {
    code->set_stub_info(MinorKey());
  }

  virtual CodeStub::Major MajorKey() { return CompareIC; }
  virtual int MinorKey();

  virtual Code::Kind GetCodeKind() const { return Code::COMPARE_IC; }

  void GenerateSmis(MacroAssembler* masm);
  void GenerateNumbers(MacroAssembler* masm);
  void GenerateInternalizedStrings(MacroAssembler* masm);
  void GenerateStrings(MacroAssembler* masm);
  void GenerateUniqueNames(MacroAssembler* masm);
  void GenerateObjects(MacroAssembler* masm);
  void GenerateMiss(MacroAssembler* masm);
  void GenerateKnownObjects(MacroAssembler* masm);
  void GenerateGeneric(MacroAssembler* masm);

  bool strict() const { return op_ == Token::EQ_STRICT; }
  Condition GetCondition() const { return CompareIC::ComputeCondition(op_); }

  virtual void AddToSpecialCache(Handle<Code> new_object);
  virtual bool FindCodeInSpecialCache(Code** code_out, Isolate* isolate);
  virtual bool UseSpecialCache() { return state_ == CompareIC::KNOWN_OBJECT; }

  Token::Value op_;
  CompareIC::State left_;
  CompareIC::State right_;
  CompareIC::State state_;
  Handle<Map> known_map_;
};


class CompareNilICStub : public HydrogenCodeStub  {
 public:
  Handle<Type> GetType(Isolate* isolate, Handle<Map> map = Handle<Map>());
  Handle<Type> GetInputType(Isolate* isolate, Handle<Map> map);

  explicit CompareNilICStub(NilValue nil) : nil_value_(nil) { }

  CompareNilICStub(ExtraICState ic_state,
                   InitializationState init_state = INITIALIZED)
      : HydrogenCodeStub(init_state),
        nil_value_(NilValueField::decode(ic_state)),
        state_(State(TypesField::decode(ic_state))) {
      }

  static Handle<Code> GetUninitialized(Isolate* isolate,
                                       NilValue nil) {
    return CompareNilICStub(nil, UNINITIALIZED).GetCode(isolate);
  }

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  static void InitializeForIsolate(Isolate* isolate) {
    CompareNilICStub compare_stub(kNullValue, UNINITIALIZED);
    compare_stub.InitializeInterfaceDescriptor(
        isolate,
        isolate->code_stub_interface_descriptor(CodeStub::CompareNilIC));
  }

  virtual InlineCacheState GetICState() {
    if (state_.Contains(GENERIC)) {
      return MEGAMORPHIC;
    } else if (state_.Contains(MONOMORPHIC_MAP)) {
      return MONOMORPHIC;
    } else {
      return PREMONOMORPHIC;
    }
  }

  virtual Code::Kind GetCodeKind() const { return Code::COMPARE_NIL_IC; }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual ExtraICState GetExtraICState() {
    return NilValueField::encode(nil_value_) |
           TypesField::encode(state_.ToIntegral());
  }

  void UpdateStatus(Handle<Object> object);

  bool IsMonomorphic() const { return state_.Contains(MONOMORPHIC_MAP); }
  NilValue GetNilValue() const { return nil_value_; }
  void ClearState() { state_.RemoveAll(); }

  virtual void PrintState(StringStream* stream);
  virtual void PrintBaseName(StringStream* stream);

 private:
  friend class CompareNilIC;

  enum CompareNilType {
    UNDEFINED,
    NULL_TYPE,
    MONOMORPHIC_MAP,
    GENERIC,
    NUMBER_OF_TYPES
  };

  // At most 6 different types can be distinguished, because the Code object
  // only has room for a single byte to hold a set and there are two more
  // boolean flags we need to store. :-P
  STATIC_ASSERT(NUMBER_OF_TYPES <= 6);

  class State : public EnumSet<CompareNilType, byte> {
   public:
    State() : EnumSet<CompareNilType, byte>(0) { }
    explicit State(byte bits) : EnumSet<CompareNilType, byte>(bits) { }

    void Print(StringStream* stream) const;
  };

  CompareNilICStub(NilValue nil, InitializationState init_state)
      : HydrogenCodeStub(init_state), nil_value_(nil) { }

  class NilValueField : public BitField<NilValue, 0, 1> {};
  class TypesField    : public BitField<byte,     1, NUMBER_OF_TYPES> {};

  virtual CodeStub::Major MajorKey() { return CompareNilIC; }
  virtual int NotMissMinorKey() { return GetExtraICState(); }

  NilValue nil_value_;
  State state_;

  DISALLOW_COPY_AND_ASSIGN(CompareNilICStub);
};


class CEntryStub : public PlatformCodeStub {
 public:
  explicit CEntryStub(int result_size,
                      SaveFPRegsMode save_doubles = kDontSaveFPRegs)
      : result_size_(result_size), save_doubles_(save_doubles) { }

  void Generate(MacroAssembler* masm);

  // The version of this stub that doesn't save doubles is generated ahead of
  // time, so it's OK to call it from other stubs that can't cope with GC during
  // their code generation.  On machines that always have gp registers (x64) we
  // can generate both variants ahead of time.
  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE;
  static void GenerateAheadOfTime(Isolate* isolate);

 protected:
  virtual void VerifyPlatformFeatures(Isolate* isolate) V8_OVERRIDE {
    ASSERT(CpuFeatures::VerifyCrossCompiling(SSE2));
  };

 private:
  void GenerateCore(MacroAssembler* masm,
                    Label* throw_normal_exception,
                    Label* throw_termination_exception,
                    Label* throw_out_of_memory_exception,
                    bool do_gc,
                    bool always_allocate_scope);

  // Number of pointers/values returned.
  Isolate* isolate_;
  const int result_size_;
  SaveFPRegsMode save_doubles_;

  Major MajorKey() { return CEntry; }
  int MinorKey();

  bool NeedsImmovableCode();
};


class JSEntryStub : public PlatformCodeStub {
 public:
  JSEntryStub() { }

  void Generate(MacroAssembler* masm) { GenerateBody(masm, false); }

 protected:
  void GenerateBody(MacroAssembler* masm, bool is_construct);

 private:
  Major MajorKey() { return JSEntry; }
  int MinorKey() { return 0; }

  virtual void FinishCode(Handle<Code> code);

  int handler_offset_;
};


class JSConstructEntryStub : public JSEntryStub {
 public:
  JSConstructEntryStub() { }

  void Generate(MacroAssembler* masm) { GenerateBody(masm, true); }

 private:
  int MinorKey() { return 1; }

  virtual void PrintName(StringStream* stream) {
    stream->Add("JSConstructEntryStub");
  }
};


class ArgumentsAccessStub: public PlatformCodeStub {
 public:
  enum Type {
    READ_ELEMENT,
    NEW_NON_STRICT_FAST,
    NEW_NON_STRICT_SLOW,
    NEW_STRICT
  };

  explicit ArgumentsAccessStub(Type type) : type_(type) { }

 private:
  Type type_;

  Major MajorKey() { return ArgumentsAccess; }
  int MinorKey() { return type_; }

  void Generate(MacroAssembler* masm);
  void GenerateReadElement(MacroAssembler* masm);
  void GenerateNewStrict(MacroAssembler* masm);
  void GenerateNewNonStrictFast(MacroAssembler* masm);
  void GenerateNewNonStrictSlow(MacroAssembler* masm);

  virtual void PrintName(StringStream* stream);
};


class RegExpExecStub: public PlatformCodeStub {
 public:
  RegExpExecStub() { }

 private:
  Major MajorKey() { return RegExpExec; }
  int MinorKey() { return 0; }

  void Generate(MacroAssembler* masm);
};


class RegExpConstructResultStub: public PlatformCodeStub {
 public:
  RegExpConstructResultStub() { }

 private:
  Major MajorKey() { return RegExpConstructResult; }
  int MinorKey() { return 0; }

  void Generate(MacroAssembler* masm);
};


class CallFunctionStub: public PlatformCodeStub {
 public:
  CallFunctionStub(int argc, CallFunctionFlags flags)
      : argc_(argc), flags_(flags) { }

  void Generate(MacroAssembler* masm);

  virtual void FinishCode(Handle<Code> code) {
    code->set_has_function_cache(RecordCallTarget());
  }

  static int ExtractArgcFromMinorKey(int minor_key) {
    return ArgcBits::decode(minor_key);
  }

 private:
  int argc_;
  CallFunctionFlags flags_;

  virtual void PrintName(StringStream* stream);

  // Minor key encoding in 32 bits with Bitfield <Type, shift, size>.
  class FlagBits: public BitField<CallFunctionFlags, 0, 2> {};
  class ArgcBits: public BitField<unsigned, 2, 32 - 2> {};

  Major MajorKey() { return CallFunction; }
  int MinorKey() {
    // Encode the parameters in a unique 32 bit value.
    return FlagBits::encode(flags_) | ArgcBits::encode(argc_);
  }

  bool ReceiverMightBeImplicit() {
    return (flags_ & RECEIVER_MIGHT_BE_IMPLICIT) != 0;
  }

  bool RecordCallTarget() {
    return (flags_ & RECORD_CALL_TARGET) != 0;
  }
};


class CallConstructStub: public PlatformCodeStub {
 public:
  explicit CallConstructStub(CallFunctionFlags flags) : flags_(flags) {}

  void Generate(MacroAssembler* masm);

  virtual void FinishCode(Handle<Code> code) {
    code->set_has_function_cache(RecordCallTarget());
  }

 private:
  CallFunctionFlags flags_;

  virtual void PrintName(StringStream* stream);

  Major MajorKey() { return CallConstruct; }
  int MinorKey() { return flags_; }

  bool RecordCallTarget() {
    return (flags_ & RECORD_CALL_TARGET) != 0;
  }
};


enum StringIndexFlags {
  // Accepts smis or heap numbers.
  STRING_INDEX_IS_NUMBER,

  // Accepts smis or heap numbers that are valid array indices
  // (ECMA-262 15.4). Invalid indices are reported as being out of
  // range.
  STRING_INDEX_IS_ARRAY_INDEX
};


// Generates code implementing String.prototype.charCodeAt.
//
// Only supports the case when the receiver is a string and the index
// is a number (smi or heap number) that is a valid index into the
// string. Additional index constraints are specified by the
// flags. Otherwise, bails out to the provided labels.
//
// Register usage: |object| may be changed to another string in a way
// that doesn't affect charCodeAt/charAt semantics, |index| is
// preserved, |scratch| and |result| are clobbered.
class StringCharCodeAtGenerator {
 public:
  StringCharCodeAtGenerator(Register object,
                            Register index,
                            Register result,
                            Label* receiver_not_string,
                            Label* index_not_number,
                            Label* index_out_of_range,
                            StringIndexFlags index_flags)
      : object_(object),
        index_(index),
        result_(result),
        receiver_not_string_(receiver_not_string),
        index_not_number_(index_not_number),
        index_out_of_range_(index_out_of_range),
        index_flags_(index_flags) {
    ASSERT(!result_.is(object_));
    ASSERT(!result_.is(index_));
  }

  // Generates the fast case code. On the fallthrough path |result|
  // register contains the result.
  void GenerateFast(MacroAssembler* masm);

  // Generates the slow case code. Must not be naturally
  // reachable. Expected to be put after a ret instruction (e.g., in
  // deferred code). Always jumps back to the fast case.
  void GenerateSlow(MacroAssembler* masm,
                    const RuntimeCallHelper& call_helper);

  // Skip handling slow case and directly jump to bailout.
  void SkipSlow(MacroAssembler* masm, Label* bailout) {
    masm->bind(&index_not_smi_);
    masm->bind(&call_runtime_);
    masm->jmp(bailout);
  }

 private:
  Register object_;
  Register index_;
  Register result_;

  Label* receiver_not_string_;
  Label* index_not_number_;
  Label* index_out_of_range_;

  StringIndexFlags index_flags_;

  Label call_runtime_;
  Label index_not_smi_;
  Label got_smi_index_;
  Label exit_;

  DISALLOW_COPY_AND_ASSIGN(StringCharCodeAtGenerator);
};


// Generates code for creating a one-char string from a char code.
class StringCharFromCodeGenerator {
 public:
  StringCharFromCodeGenerator(Register code,
                              Register result)
      : code_(code),
        result_(result) {
    ASSERT(!code_.is(result_));
  }

  // Generates the fast case code. On the fallthrough path |result|
  // register contains the result.
  void GenerateFast(MacroAssembler* masm);

  // Generates the slow case code. Must not be naturally
  // reachable. Expected to be put after a ret instruction (e.g., in
  // deferred code). Always jumps back to the fast case.
  void GenerateSlow(MacroAssembler* masm,
                    const RuntimeCallHelper& call_helper);

  // Skip handling slow case and directly jump to bailout.
  void SkipSlow(MacroAssembler* masm, Label* bailout) {
    masm->bind(&slow_case_);
    masm->jmp(bailout);
  }

 private:
  Register code_;
  Register result_;

  Label slow_case_;
  Label exit_;

  DISALLOW_COPY_AND_ASSIGN(StringCharFromCodeGenerator);
};


// Generates code implementing String.prototype.charAt.
//
// Only supports the case when the receiver is a string and the index
// is a number (smi or heap number) that is a valid index into the
// string. Additional index constraints are specified by the
// flags. Otherwise, bails out to the provided labels.
//
// Register usage: |object| may be changed to another string in a way
// that doesn't affect charCodeAt/charAt semantics, |index| is
// preserved, |scratch1|, |scratch2|, and |result| are clobbered.
class StringCharAtGenerator {
 public:
  StringCharAtGenerator(Register object,
                        Register index,
                        Register scratch,
                        Register result,
                        Label* receiver_not_string,
                        Label* index_not_number,
                        Label* index_out_of_range,
                        StringIndexFlags index_flags)
      : char_code_at_generator_(object,
                                index,
                                scratch,
                                receiver_not_string,
                                index_not_number,
                                index_out_of_range,
                                index_flags),
        char_from_code_generator_(scratch, result) {}

  // Generates the fast case code. On the fallthrough path |result|
  // register contains the result.
  void GenerateFast(MacroAssembler* masm) {
    char_code_at_generator_.GenerateFast(masm);
    char_from_code_generator_.GenerateFast(masm);
  }

  // Generates the slow case code. Must not be naturally
  // reachable. Expected to be put after a ret instruction (e.g., in
  // deferred code). Always jumps back to the fast case.
  void GenerateSlow(MacroAssembler* masm,
                    const RuntimeCallHelper& call_helper) {
    char_code_at_generator_.GenerateSlow(masm, call_helper);
    char_from_code_generator_.GenerateSlow(masm, call_helper);
  }

  // Skip handling slow case and directly jump to bailout.
  void SkipSlow(MacroAssembler* masm, Label* bailout) {
    char_code_at_generator_.SkipSlow(masm, bailout);
    char_from_code_generator_.SkipSlow(masm, bailout);
  }

 private:
  StringCharCodeAtGenerator char_code_at_generator_;
  StringCharFromCodeGenerator char_from_code_generator_;

  DISALLOW_COPY_AND_ASSIGN(StringCharAtGenerator);
};


class AllowStubCallsScope {
 public:
  AllowStubCallsScope(MacroAssembler* masm, bool allow)
       : masm_(masm), previous_allow_(masm->allow_stub_calls()) {
    masm_->set_allow_stub_calls(allow);
  }
  ~AllowStubCallsScope() {
    masm_->set_allow_stub_calls(previous_allow_);
  }

 private:
  MacroAssembler* masm_;
  bool previous_allow_;

  DISALLOW_COPY_AND_ASSIGN(AllowStubCallsScope);
};


class KeyedLoadDictionaryElementStub : public HydrogenCodeStub {
 public:
  KeyedLoadDictionaryElementStub() {}

  virtual Handle<Code> GenerateCode(Isolate* isolate) V8_OVERRIDE;

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor) V8_OVERRIDE;

 private:
  Major MajorKey() { return KeyedLoadElement; }
  int NotMissMinorKey() { return DICTIONARY_ELEMENTS; }

  DISALLOW_COPY_AND_ASSIGN(KeyedLoadDictionaryElementStub);
};


class KeyedLoadDictionaryElementPlatformStub : public PlatformCodeStub {
 public:
  KeyedLoadDictionaryElementPlatformStub() {}

  void Generate(MacroAssembler* masm);

 private:
  Major MajorKey() { return KeyedLoadElement; }
  int MinorKey() { return DICTIONARY_ELEMENTS; }

  DISALLOW_COPY_AND_ASSIGN(KeyedLoadDictionaryElementPlatformStub);
};


class DoubleToIStub : public PlatformCodeStub {
 public:
  DoubleToIStub(Register source,
                Register destination,
                int offset,
                bool is_truncating,
                bool skip_fastpath = false) : bit_field_(0) {
    bit_field_ = SourceRegisterBits::encode(source.code_) |
      DestinationRegisterBits::encode(destination.code_) |
      OffsetBits::encode(offset) |
      IsTruncatingBits::encode(is_truncating) |
      SkipFastPathBits::encode(skip_fastpath) |
      SSEBits::encode(CpuFeatures::IsSafeForSnapshot(SSE2) ?
                          CpuFeatures::IsSafeForSnapshot(SSE3) ? 2 : 1 : 0);
  }

  Register source() {
    Register result = { SourceRegisterBits::decode(bit_field_) };
    return result;
  }

  Register destination() {
    Register result = { DestinationRegisterBits::decode(bit_field_) };
    return result;
  }

  bool is_truncating() {
    return IsTruncatingBits::decode(bit_field_);
  }

  bool skip_fastpath() {
    return SkipFastPathBits::decode(bit_field_);
  }

  int offset() {
    return OffsetBits::decode(bit_field_);
  }

  void Generate(MacroAssembler* masm);

  virtual bool SometimesSetsUpAFrame() { return false; }

 protected:
  virtual void VerifyPlatformFeatures(Isolate* isolate) V8_OVERRIDE {
    ASSERT(CpuFeatures::VerifyCrossCompiling(SSE2));
  }

 private:
  static const int kBitsPerRegisterNumber = 6;
  STATIC_ASSERT((1L << kBitsPerRegisterNumber) >= Register::kNumRegisters);
  class SourceRegisterBits:
      public BitField<int, 0, kBitsPerRegisterNumber> {};  // NOLINT
  class DestinationRegisterBits:
      public BitField<int, kBitsPerRegisterNumber,
        kBitsPerRegisterNumber> {};  // NOLINT
  class IsTruncatingBits:
      public BitField<bool, 2 * kBitsPerRegisterNumber, 1> {};  // NOLINT
  class OffsetBits:
      public BitField<int, 2 * kBitsPerRegisterNumber + 1, 3> {};  // NOLINT
  class SkipFastPathBits:
      public BitField<int, 2 * kBitsPerRegisterNumber + 4, 1> {};  // NOLINT
  class SSEBits:
      public BitField<int, 2 * kBitsPerRegisterNumber + 5, 2> {};  // NOLINT

  Major MajorKey() { return DoubleToI; }
  int MinorKey() { return bit_field_; }

  int bit_field_;

  DISALLOW_COPY_AND_ASSIGN(DoubleToIStub);
};


class KeyedLoadFastElementStub : public HydrogenCodeStub {
 public:
  KeyedLoadFastElementStub(bool is_js_array, ElementsKind elements_kind) {
    bit_field_ = ElementsKindBits::encode(elements_kind) |
        IsJSArrayBits::encode(is_js_array);
  }

  bool is_js_array() const {
    return IsJSArrayBits::decode(bit_field_);
  }

  ElementsKind elements_kind() const {
    return ElementsKindBits::decode(bit_field_);
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  class ElementsKindBits: public BitField<ElementsKind, 0, 8> {};
  class IsJSArrayBits: public BitField<bool, 8, 1> {};
  uint32_t bit_field_;

  Major MajorKey() { return KeyedLoadElement; }
  int NotMissMinorKey() { return bit_field_; }

  DISALLOW_COPY_AND_ASSIGN(KeyedLoadFastElementStub);
};


class KeyedStoreFastElementStub : public HydrogenCodeStub {
 public:
  KeyedStoreFastElementStub(bool is_js_array,
                            ElementsKind elements_kind,
                            KeyedAccessStoreMode mode) {
    bit_field_ = ElementsKindBits::encode(elements_kind) |
        IsJSArrayBits::encode(is_js_array) |
        StoreModeBits::encode(mode);
  }

  bool is_js_array() const {
    return IsJSArrayBits::decode(bit_field_);
  }

  ElementsKind elements_kind() const {
    return ElementsKindBits::decode(bit_field_);
  }

  KeyedAccessStoreMode store_mode() const {
    return StoreModeBits::decode(bit_field_);
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  class ElementsKindBits: public BitField<ElementsKind,      0, 8> {};
  class StoreModeBits: public BitField<KeyedAccessStoreMode, 8, 4> {};
  class IsJSArrayBits: public BitField<bool,                12, 1> {};
  uint32_t bit_field_;

  Major MajorKey() { return KeyedStoreElement; }
  int NotMissMinorKey() { return bit_field_; }

  DISALLOW_COPY_AND_ASSIGN(KeyedStoreFastElementStub);
};


class TransitionElementsKindStub : public HydrogenCodeStub {
 public:
  TransitionElementsKindStub(ElementsKind from_kind,
                             ElementsKind to_kind) {
    bit_field_ = FromKindBits::encode(from_kind) |
        ToKindBits::encode(to_kind);
  }

  ElementsKind from_kind() const {
    return FromKindBits::decode(bit_field_);
  }

  ElementsKind to_kind() const {
    return ToKindBits::decode(bit_field_);
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  class FromKindBits: public BitField<ElementsKind, 8, 8> {};
  class ToKindBits: public BitField<ElementsKind, 0, 8> {};
  uint32_t bit_field_;

  Major MajorKey() { return TransitionElementsKind; }
  int NotMissMinorKey() { return bit_field_; }

  DISALLOW_COPY_AND_ASSIGN(TransitionElementsKindStub);
};


enum ContextCheckMode {
  CONTEXT_CHECK_REQUIRED,
  CONTEXT_CHECK_NOT_REQUIRED,
  LAST_CONTEXT_CHECK_MODE = CONTEXT_CHECK_NOT_REQUIRED
};


class ArrayConstructorStubBase : public HydrogenCodeStub {
 public:
  ArrayConstructorStubBase(ElementsKind kind, ContextCheckMode context_mode,
                           AllocationSiteOverrideMode override_mode) {
    // It only makes sense to override local allocation site behavior
    // if there is a difference between the global allocation site policy
    // for an ElementsKind and the desired usage of the stub.
    ASSERT(!(FLAG_track_allocation_sites &&
             override_mode == DISABLE_ALLOCATION_SITES) ||
           AllocationSite::GetMode(kind) == TRACK_ALLOCATION_SITE);
    bit_field_ = ElementsKindBits::encode(kind) |
        AllocationSiteOverrideModeBits::encode(override_mode) |
        ContextCheckModeBits::encode(context_mode);
  }

  ElementsKind elements_kind() const {
    return ElementsKindBits::decode(bit_field_);
  }

  AllocationSiteOverrideMode override_mode() const {
    return AllocationSiteOverrideModeBits::decode(bit_field_);
  }

  ContextCheckMode context_mode() const {
    return ContextCheckModeBits::decode(bit_field_);
  }

  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE {
    // We only pre-generate stubs that verify correct context
    return context_mode() == CONTEXT_CHECK_REQUIRED;
  }

  static void GenerateStubsAheadOfTime(Isolate* isolate);
  static void InstallDescriptors(Isolate* isolate);

  // Parameters accessed via CodeStubGraphBuilder::GetParameter()
  static const int kConstructor = 0;
  static const int kPropertyCell = 1;

 private:
  int NotMissMinorKey() { return bit_field_; }

  // Ensure data fits within available bits.
  STATIC_ASSERT(LAST_ALLOCATION_SITE_OVERRIDE_MODE == 1);
  STATIC_ASSERT(LAST_CONTEXT_CHECK_MODE == 1);

  class ElementsKindBits: public BitField<ElementsKind, 0, 8> {};
  class AllocationSiteOverrideModeBits: public
      BitField<AllocationSiteOverrideMode, 8, 1> {};  // NOLINT
  class ContextCheckModeBits: public BitField<ContextCheckMode, 9, 1> {};
  uint32_t bit_field_;

  DISALLOW_COPY_AND_ASSIGN(ArrayConstructorStubBase);
};


class ArrayNoArgumentConstructorStub : public ArrayConstructorStubBase {
 public:
  ArrayNoArgumentConstructorStub(
      ElementsKind kind,
      ContextCheckMode context_mode = CONTEXT_CHECK_REQUIRED,
      AllocationSiteOverrideMode override_mode = DONT_OVERRIDE)
      : ArrayConstructorStubBase(kind, context_mode, override_mode) {
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return ArrayNoArgumentConstructor; }

  DISALLOW_COPY_AND_ASSIGN(ArrayNoArgumentConstructorStub);
};


class ArraySingleArgumentConstructorStub : public ArrayConstructorStubBase {
 public:
  ArraySingleArgumentConstructorStub(
      ElementsKind kind,
      ContextCheckMode context_mode = CONTEXT_CHECK_REQUIRED,
      AllocationSiteOverrideMode override_mode = DONT_OVERRIDE)
      : ArrayConstructorStubBase(kind, context_mode, override_mode) {
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return ArraySingleArgumentConstructor; }

  DISALLOW_COPY_AND_ASSIGN(ArraySingleArgumentConstructorStub);
};


class ArrayNArgumentsConstructorStub : public ArrayConstructorStubBase {
 public:
  ArrayNArgumentsConstructorStub(
      ElementsKind kind,
      ContextCheckMode context_mode = CONTEXT_CHECK_REQUIRED,
      AllocationSiteOverrideMode override_mode = DONT_OVERRIDE)
      : ArrayConstructorStubBase(kind, context_mode, override_mode) {
  }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return ArrayNArgumentsConstructor; }

  DISALLOW_COPY_AND_ASSIGN(ArrayNArgumentsConstructorStub);
};


class InternalArrayConstructorStubBase : public HydrogenCodeStub {
 public:
  explicit InternalArrayConstructorStubBase(ElementsKind kind) {
    kind_ = kind;
  }

  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE { return true; }
  static void GenerateStubsAheadOfTime(Isolate* isolate);
  static void InstallDescriptors(Isolate* isolate);

  // Parameters accessed via CodeStubGraphBuilder::GetParameter()
  static const int kConstructor = 0;

  ElementsKind elements_kind() const { return kind_; }

 private:
  int NotMissMinorKey() { return kind_; }

  ElementsKind kind_;

  DISALLOW_COPY_AND_ASSIGN(InternalArrayConstructorStubBase);
};


class InternalArrayNoArgumentConstructorStub : public
    InternalArrayConstructorStubBase {
 public:
  explicit InternalArrayNoArgumentConstructorStub(ElementsKind kind)
      : InternalArrayConstructorStubBase(kind) { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return InternalArrayNoArgumentConstructor; }

  DISALLOW_COPY_AND_ASSIGN(InternalArrayNoArgumentConstructorStub);
};


class InternalArraySingleArgumentConstructorStub : public
    InternalArrayConstructorStubBase {
 public:
  explicit InternalArraySingleArgumentConstructorStub(ElementsKind kind)
      : InternalArrayConstructorStubBase(kind) { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return InternalArraySingleArgumentConstructor; }

  DISALLOW_COPY_AND_ASSIGN(InternalArraySingleArgumentConstructorStub);
};


class InternalArrayNArgumentsConstructorStub : public
    InternalArrayConstructorStubBase {
 public:
  explicit InternalArrayNArgumentsConstructorStub(ElementsKind kind)
      : InternalArrayConstructorStubBase(kind) { }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  Major MajorKey() { return InternalArrayNArgumentsConstructor; }

  DISALLOW_COPY_AND_ASSIGN(InternalArrayNArgumentsConstructorStub);
};


class KeyedStoreElementStub : public PlatformCodeStub {
 public:
  KeyedStoreElementStub(bool is_js_array,
                        ElementsKind elements_kind,
                        KeyedAccessStoreMode store_mode)
      : is_js_array_(is_js_array),
        elements_kind_(elements_kind),
        store_mode_(store_mode),
        fp_registers_(CanUseFPRegisters()) { }

  Major MajorKey() { return KeyedStoreElement; }
  int MinorKey() {
    return ElementsKindBits::encode(elements_kind_) |
        IsJSArrayBits::encode(is_js_array_) |
        StoreModeBits::encode(store_mode_) |
        FPRegisters::encode(fp_registers_);
  }

  void Generate(MacroAssembler* masm);

 private:
  class ElementsKindBits: public BitField<ElementsKind,      0, 8> {};
  class StoreModeBits: public BitField<KeyedAccessStoreMode, 8, 4> {};
  class IsJSArrayBits: public BitField<bool,                12, 1> {};
  class FPRegisters: public BitField<bool,                  13, 1> {};

  bool is_js_array_;
  ElementsKind elements_kind_;
  KeyedAccessStoreMode store_mode_;
  bool fp_registers_;

  DISALLOW_COPY_AND_ASSIGN(KeyedStoreElementStub);
};


class ToBooleanStub: public HydrogenCodeStub {
 public:
  enum Type {
    UNDEFINED,
    BOOLEAN,
    NULL_TYPE,
    SMI,
    SPEC_OBJECT,
    STRING,
    SYMBOL,
    HEAP_NUMBER,
    NUMBER_OF_TYPES
  };

  // At most 8 different types can be distinguished, because the Code object
  // only has room for a single byte to hold a set of these types. :-P
  STATIC_ASSERT(NUMBER_OF_TYPES <= 8);

  class Types : public EnumSet<Type, byte> {
   public:
    Types() : EnumSet<Type, byte>(0) {}
    explicit Types(byte bits) : EnumSet<Type, byte>(bits) {}

    byte ToByte() const { return ToIntegral(); }
    void Print(StringStream* stream) const;
    bool UpdateStatus(Handle<Object> object);
    bool NeedsMap() const;
    bool CanBeUndetectable() const;
    bool IsGeneric() const { return ToIntegral() == Generic().ToIntegral(); }

    static Types Generic() { return Types((1 << NUMBER_OF_TYPES) - 1); }
  };

  explicit ToBooleanStub(Types types = Types())
      : types_(types) { }
  explicit ToBooleanStub(ExtraICState state)
      : types_(static_cast<byte>(state)) { }

  bool UpdateStatus(Handle<Object> object);
  Types GetTypes() { return types_; }

  virtual Handle<Code> GenerateCode(Isolate* isolate);
  virtual void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

  virtual Code::Kind GetCodeKind() const { return Code::TO_BOOLEAN_IC; }
  virtual void PrintState(StringStream* stream);

  virtual bool SometimesSetsUpAFrame() { return false; }

  static void InitializeForIsolate(Isolate* isolate) {
    ToBooleanStub stub;
    stub.InitializeInterfaceDescriptor(
        isolate,
        isolate->code_stub_interface_descriptor(CodeStub::ToBoolean));
  }

  static Handle<Code> GetUninitialized(Isolate* isolate) {
    return ToBooleanStub(UNINITIALIZED).GetCode(isolate);
  }

  virtual ExtraICState GetExtraICState() {
    return types_.ToIntegral();
  }

  virtual InlineCacheState GetICState() {
    if (types_.IsEmpty()) {
      return ::v8::internal::UNINITIALIZED;
    } else {
      return MONOMORPHIC;
    }
  }

 private:
  Major MajorKey() { return ToBoolean; }
  int NotMissMinorKey() { return GetExtraICState(); }

  explicit ToBooleanStub(InitializationState init_state) :
    HydrogenCodeStub(init_state) {}

  Types types_;
};


class ElementsTransitionAndStoreStub : public HydrogenCodeStub {
 public:
  ElementsTransitionAndStoreStub(ElementsKind from_kind,
                                 ElementsKind to_kind,
                                 bool is_jsarray,
                                 KeyedAccessStoreMode store_mode)
      : from_kind_(from_kind),
        to_kind_(to_kind),
        is_jsarray_(is_jsarray),
        store_mode_(store_mode) {}

  ElementsKind from_kind() const { return from_kind_; }
  ElementsKind to_kind() const { return to_kind_; }
  bool is_jsarray() const { return is_jsarray_; }
  KeyedAccessStoreMode store_mode() const { return store_mode_; }

  virtual Handle<Code> GenerateCode(Isolate* isolate);

  void InitializeInterfaceDescriptor(
      Isolate* isolate,
      CodeStubInterfaceDescriptor* descriptor);

 private:
  class FromBits:      public BitField<ElementsKind,          0, 8> {};
  class ToBits:        public BitField<ElementsKind,          8, 8> {};
  class IsJSArrayBits: public BitField<bool,                 16, 1> {};
  class StoreModeBits: public BitField<KeyedAccessStoreMode, 17, 4> {};

  Major MajorKey() { return ElementsTransitionAndStore; }
  int NotMissMinorKey() {
    return FromBits::encode(from_kind_) |
        ToBits::encode(to_kind_) |
        IsJSArrayBits::encode(is_jsarray_) |
        StoreModeBits::encode(store_mode_);
  }

  ElementsKind from_kind_;
  ElementsKind to_kind_;
  bool is_jsarray_;
  KeyedAccessStoreMode store_mode_;

  DISALLOW_COPY_AND_ASSIGN(ElementsTransitionAndStoreStub);
};


class StoreArrayLiteralElementStub : public PlatformCodeStub {
 public:
  StoreArrayLiteralElementStub()
        : fp_registers_(CanUseFPRegisters()) { }

 private:
  class FPRegisters: public BitField<bool,                0, 1> {};

  Major MajorKey() { return StoreArrayLiteralElement; }
  int MinorKey() { return FPRegisters::encode(fp_registers_); }

  void Generate(MacroAssembler* masm);

  bool fp_registers_;

  DISALLOW_COPY_AND_ASSIGN(StoreArrayLiteralElementStub);
};


class StubFailureTrampolineStub : public PlatformCodeStub {
 public:
  explicit StubFailureTrampolineStub(StubFunctionMode function_mode)
      : fp_registers_(CanUseFPRegisters()), function_mode_(function_mode) {}

  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE { return true; }

  static void GenerateAheadOfTime(Isolate* isolate);

 private:
  class FPRegisters:       public BitField<bool,                0, 1> {};
  class FunctionModeField: public BitField<StubFunctionMode,    1, 1> {};

  Major MajorKey() { return StubFailureTrampoline; }
  int MinorKey() {
    return FPRegisters::encode(fp_registers_) |
        FunctionModeField::encode(function_mode_);
  }

  void Generate(MacroAssembler* masm);

  bool fp_registers_;
  StubFunctionMode function_mode_;

  DISALLOW_COPY_AND_ASSIGN(StubFailureTrampolineStub);
};


class StubFailureTailCallTrampolineStub : public PlatformCodeStub {
 public:
  StubFailureTailCallTrampolineStub() : fp_registers_(CanUseFPRegisters()) {}

  virtual bool IsPregenerated(Isolate* isolate) V8_OVERRIDE { return true; }

  static void GenerateAheadOfTime(Isolate* isolate);

 private:
  class FPRegisters: public BitField<bool, 0, 1> {};
  Major MajorKey() { return StubFailureTailCallTrampoline; }
  int MinorKey() { return FPRegisters::encode(fp_registers_); }

  void Generate(MacroAssembler* masm);

  bool fp_registers_;

  DISALLOW_COPY_AND_ASSIGN(StubFailureTailCallTrampolineStub);
};


class ProfileEntryHookStub : public PlatformCodeStub {
 public:
  explicit ProfileEntryHookStub() {}

  // The profile entry hook function is not allowed to cause a GC.
  virtual bool SometimesSetsUpAFrame() { return false; }

  // Generates a call to the entry hook if it's enabled.
  static void MaybeCallEntryHook(MacroAssembler* masm);

 private:
  static void EntryHookTrampoline(intptr_t function,
                                  intptr_t stack_pointer,
                                  Isolate* isolate);

  Major MajorKey() { return ProfileEntryHook; }
  int MinorKey() { return 0; }

  void Generate(MacroAssembler* masm);

  DISALLOW_COPY_AND_ASSIGN(ProfileEntryHookStub);
};

} }  // namespace v8::internal

#endif  // V8_CODE_STUBS_H_