text: // 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:
  //
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  //       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
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  //       with the distribution.
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  //       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
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  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #ifndef V8_X64_MACRO_ASSEMBLER_X64_H_
  #define V8_X64_MACRO_ASSEMBLER_X64_H_
  
  #include "assembler.h"
  #include "frames.h"
  #include "v8globals.h"
  
  namespace v8 {
  namespace internal {
  
  // Default scratch register used by MacroAssembler (and other code that needs
  // a spare register). The register isn't callee save, and not used by the
  // function calling convention.
  const Register kScratchRegister = { 10 };      // r10.
  const Register kSmiConstantRegister = { 12 };  // r12 (callee save).
  const Register kRootRegister = { 13 };         // r13 (callee save).
  // Value of smi in kSmiConstantRegister.
  const int kSmiConstantRegisterValue = 1;
  // Actual value of root register is offset from the root array's start
  // to take advantage of negitive 8-bit displacement values.
  const int kRootRegisterBias = 128;
  
  // Convenience for platform-independent signatures.
  typedef Operand MemOperand;
  
  enum RememberedSetAction { EMIT_REMEMBERED_SET, OMIT_REMEMBERED_SET };
  enum SmiCheck { INLINE_SMI_CHECK, OMIT_SMI_CHECK };
  
  bool AreAliased(Register r1, Register r2, Register r3, Register r4);
  
  // Forward declaration.
  class JumpTarget;
  
  struct SmiIndex {
    SmiIndex(Register index_register, ScaleFactor scale)
        : reg(index_register),
          scale(scale) {}
    Register reg;
    ScaleFactor scale;
  };
  
  
  // MacroAssembler implements a collection of frequently used macros.
  class MacroAssembler: public Assembler {
   public:
    // The isolate parameter can be NULL if the macro assembler should
    // not use isolate-dependent functionality. In this case, it's the
    // responsibility of the caller to never invoke such function on the
    // macro assembler.
    MacroAssembler(Isolate* isolate, void* buffer, int size);
  
    // Prevent the use of the RootArray during the lifetime of this
    // scope object.
    class NoRootArrayScope BASE_EMBEDDED {
     public:
      explicit NoRootArrayScope(MacroAssembler* assembler)
          : variable_(&assembler->root_array_available_),
            old_value_(assembler->root_array_available_) {
        assembler->root_array_available_ = false;
      }
      ~NoRootArrayScope() {
        *variable_ = old_value_;
      }
     private:
      bool* variable_;
      bool old_value_;
    };
  
    // Operand pointing to an external reference.
    // May emit code to set up the scratch register. The operand is
    // only guaranteed to be correct as long as the scratch register
    // isn't changed.
    // If the operand is used more than once, use a scratch register
    // that is guaranteed not to be clobbered.
    Operand ExternalOperand(ExternalReference reference,
                            Register scratch = kScratchRegister);
    // Loads and stores the value of an external reference.
    // Special case code for load and store to take advantage of
    // load_rax/store_rax if possible/necessary.
    // For other operations, just use:
    //   Operand operand = ExternalOperand(extref);
    //   operation(operand, ..);
    void Load(Register destination, ExternalReference source);
    void Store(ExternalReference destination, Register source);
    // Loads the address of the external reference into the destination
    // register.
    void LoadAddress(Register destination, ExternalReference source);
    // Returns the size of the code generated by LoadAddress.
    // Used by CallSize(ExternalReference) to find the size of a call.
    int LoadAddressSize(ExternalReference source);
    // Pushes the address of the external reference onto the stack.
    void PushAddress(ExternalReference source);
  
    // Operations on roots in the root-array.
    void LoadRoot(Register destination, Heap::RootListIndex index);
    void StoreRoot(Register source, Heap::RootListIndex index);
    // Load a root value where the index (or part of it) is variable.
    // The variable_offset register is added to the fixed_offset value
    // to get the index into the root-array.
    void LoadRootIndexed(Register destination,
                         Register variable_offset,
                         int fixed_offset);
    void CompareRoot(Register with, Heap::RootListIndex index);
    void CompareRoot(const Operand& with, Heap::RootListIndex index);
    void PushRoot(Heap::RootListIndex index);
  
    // These functions do not arrange the registers in any particular order so
    // they are not useful for calls that can cause a GC.  The caller can
    // exclude up to 3 registers that do not need to be saved and restored.
    void PushCallerSaved(SaveFPRegsMode fp_mode,
                         Register exclusion1 = no_reg,
                         Register exclusion2 = no_reg,
                         Register exclusion3 = no_reg);
    void PopCallerSaved(SaveFPRegsMode fp_mode,
                        Register exclusion1 = no_reg,
                        Register exclusion2 = no_reg,
                        Register exclusion3 = no_reg);
  
  // ---------------------------------------------------------------------------
  // GC Support
  
  
    enum RememberedSetFinalAction {
      kReturnAtEnd,
      kFallThroughAtEnd
    };
  
    // Record in the remembered set the fact that we have a pointer to new space
    // at the address pointed to by the addr register.  Only works if addr is not
    // in new space.
    void RememberedSetHelper(Register object,  // Used for debug code.
                             Register addr,
                             Register scratch,
                             SaveFPRegsMode save_fp,
                             RememberedSetFinalAction and_then);
  
    void CheckPageFlag(Register object,
                       Register scratch,
                       int mask,
                       Condition cc,
                       Label* condition_met,
                       Label::Distance condition_met_distance = Label::kFar);
  
    // Check if object is in new space.  Jumps if the object is not in new space.
    // The register scratch can be object itself, but scratch will be clobbered.
    void JumpIfNotInNewSpace(Register object,
                             Register scratch,
                             Label* branch,
                             Label::Distance distance = Label::kFar) {
      InNewSpace(object, scratch, not_equal, branch, distance);
    }
  
    // Check if object is in new space.  Jumps if the object is in new space.
    // The register scratch can be object itself, but it will be clobbered.
    void JumpIfInNewSpace(Register object,
                          Register scratch,
                          Label* branch,
                          Label::Distance distance = Label::kFar) {
      InNewSpace(object, scratch, equal, branch, distance);
    }
  
    // Check if an object has the black incremental marking color.  Also uses rcx!
    void JumpIfBlack(Register object,
                     Register scratch0,
                     Register scratch1,
                     Label* on_black,
                     Label::Distance on_black_distance = Label::kFar);
  
    // Detects conservatively whether an object is data-only, i.e. it does need to
    // be scanned by the garbage collector.
    void JumpIfDataObject(Register value,
                          Register scratch,
                          Label* not_data_object,
                          Label::Distance not_data_object_distance);
  
    // Checks the color of an object.  If the object is already grey or black
    // then we just fall through, since it is already live.  If it is white and
    // we can determine that it doesn't need to be scanned, then we just mark it
    // black and fall through.  For the rest we jump to the label so the
    // incremental marker can fix its assumptions.
    void EnsureNotWhite(Register object,
                        Register scratch1,
                        Register scratch2,
                        Label* object_is_white_and_not_data,
                        Label::Distance distance);
  
    // Notify the garbage collector that we wrote a pointer into an object.
    // |object| is the object being stored into, |value| is the object being
    // stored.  value and scratch registers are clobbered by the operation.
    // The offset is the offset from the start of the object, not the offset from
    // the tagged HeapObject pointer.  For use with FieldOperand(reg, off).
    void RecordWriteField(
        Register object,
        int offset,
        Register value,
        Register scratch,
        SaveFPRegsMode save_fp,
        RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
        SmiCheck smi_check = INLINE_SMI_CHECK);
  
    // As above, but the offset has the tag presubtracted.  For use with
    // Operand(reg, off).
    void RecordWriteContextSlot(
        Register context,
        int offset,
        Register value,
        Register scratch,
        SaveFPRegsMode save_fp,
        RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
        SmiCheck smi_check = INLINE_SMI_CHECK) {
      RecordWriteField(context,
                       offset + kHeapObjectTag,
                       value,
                       scratch,
                       save_fp,
                       remembered_set_action,
                       smi_check);
    }
  
    // Notify the garbage collector that we wrote a pointer into a fixed array.
    // |array| is the array being stored into, |value| is the
    // object being stored.  |index| is the array index represented as a non-smi.
    // All registers are clobbered by the operation RecordWriteArray
    // filters out smis so it does not update the write barrier if the
    // value is a smi.
    void RecordWriteArray(
        Register array,
        Register value,
        Register index,
        SaveFPRegsMode save_fp,
        RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
        SmiCheck smi_check = INLINE_SMI_CHECK);
  
    // For page containing |object| mark region covering |address|
    // dirty. |object| is the object being stored into, |value| is the
    // object being stored. The address and value registers are clobbered by the
    // operation.  RecordWrite filters out smis so it does not update
    // the write barrier if the value is a smi.
    void RecordWrite(
        Register object,
        Register address,
        Register value,
        SaveFPRegsMode save_fp,
        RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
        SmiCheck smi_check = INLINE_SMI_CHECK);
  
  #ifdef ENABLE_DEBUGGER_SUPPORT
    // ---------------------------------------------------------------------------
    // Debugger Support
  
    void DebugBreak();
  #endif
  
    // Enter specific kind of exit frame; either in normal or
    // debug mode. Expects the number of arguments in register rax and
    // sets up the number of arguments in register rdi and the pointer
    // to the first argument in register rsi.
    //
    // Allocates arg_stack_space * kPointerSize memory (not GCed) on the stack
    // accessible via StackSpaceOperand.
    void EnterExitFrame(int arg_stack_space = 0, bool save_doubles = false);
  
    // Enter specific kind of exit frame. Allocates arg_stack_space * kPointerSize
    // memory (not GCed) on the stack accessible via StackSpaceOperand.
    void EnterApiExitFrame(int arg_stack_space);
  
    // Leave the current exit frame. Expects/provides the return value in
    // register rax:rdx (untouched) and the pointer to the first
    // argument in register rsi.
    void LeaveExitFrame(bool save_doubles = false);
  
    // Leave the current exit frame. Expects/provides the return value in
    // register rax (untouched).
    void LeaveApiExitFrame();
  
    // Push and pop the registers that can hold pointers.
    void PushSafepointRegisters() { Pushad(); }
    void PopSafepointRegisters() { Popad(); }
    // Store the value in register src in the safepoint register stack
    // slot for register dst.
    void StoreToSafepointRegisterSlot(Register dst, const Immediate& imm);
    void StoreToSafepointRegisterSlot(Register dst, Register src);
    void LoadFromSafepointRegisterSlot(Register dst, Register src);
  
    void InitializeRootRegister() {
      ExternalReference roots_array_start =
          ExternalReference::roots_array_start(isolate());
      movq(kRootRegister, roots_array_start);
      addq(kRootRegister, Immediate(kRootRegisterBias));
    }
  
    // ---------------------------------------------------------------------------
    // JavaScript invokes
  
    // Set up call kind marking in rcx. The method takes rcx as an
    // explicit first parameter to make the code more readable at the
    // call sites.
    void SetCallKind(Register dst, CallKind kind);
  
    // Invoke the JavaScript function code by either calling or jumping.
    void InvokeCode(Register code,
                    const ParameterCount& expected,
                    const ParameterCount& actual,
                    InvokeFlag flag,
                    const CallWrapper& call_wrapper,
                    CallKind call_kind);
  
    void InvokeCode(Handle<Code> code,
                    const ParameterCount& expected,
                    const ParameterCount& actual,
                    RelocInfo::Mode rmode,
                    InvokeFlag flag,
                    const CallWrapper& call_wrapper,
                    CallKind call_kind);
  
    // Invoke the JavaScript function in the given register. Changes the
    // current context to the context in the function before invoking.
    void InvokeFunction(Register function,
                        const ParameterCount& actual,
                        InvokeFlag flag,
                        const CallWrapper& call_wrapper,
                        CallKind call_kind);
  
    void InvokeFunction(Handle<JSFunction> function,
                        const ParameterCount& actual,
                        InvokeFlag flag,
                        const CallWrapper& call_wrapper,
                        CallKind call_kind);
  
    // Invoke specified builtin JavaScript function. Adds an entry to
    // the unresolved list if the name does not resolve.
    void InvokeBuiltin(Builtins::JavaScript id,
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper = NullCallWrapper());
  
    // Store the function for the given builtin in the target register.
    void GetBuiltinFunction(Register target, Builtins::JavaScript id);
  
    // Store the code object for the given builtin in the target register.
    void GetBuiltinEntry(Register target, Builtins::JavaScript id);
  
  
    // ---------------------------------------------------------------------------
    // Smi tagging, untagging and operations on tagged smis.
  
    void InitializeSmiConstantRegister() {
      movq(kSmiConstantRegister,
           reinterpret_cast<uint64_t>(Smi::FromInt(kSmiConstantRegisterValue)),
           RelocInfo::NONE64);
    }
  
    // Conversions between tagged smi values and non-tagged integer values.
  
    // Tag an integer value. The result must be known to be a valid smi value.
    // Only uses the low 32 bits of the src register. Sets the N and Z flags
    // based on the value of the resulting smi.
    void Integer32ToSmi(Register dst, Register src);
  
    // Stores an integer32 value into a memory field that already holds a smi.
    void Integer32ToSmiField(const Operand& dst, Register src);
  
    // Adds constant to src and tags the result as a smi.
    // Result must be a valid smi.
    void Integer64PlusConstantToSmi(Register dst, Register src, int constant);
  
    // Convert smi to 32-bit integer. I.e., not sign extended into
    // high 32 bits of destination.
    void SmiToInteger32(Register dst, Register src);
    void SmiToInteger32(Register dst, const Operand& src);
  
    // Convert smi to 64-bit integer (sign extended if necessary).
    void SmiToInteger64(Register dst, Register src);
    void SmiToInteger64(Register dst, const Operand& src);
  
    // Multiply a positive smi's integer value by a power of two.
    // Provides result as 64-bit integer value.
    void PositiveSmiTimesPowerOfTwoToInteger64(Register dst,
                                               Register src,
                                               int power);
  
    // Divide a positive smi's integer value by a power of two.
    // Provides result as 32-bit integer value.
    void PositiveSmiDivPowerOfTwoToInteger32(Register dst,
                                             Register src,
                                             int power);
  
    // Perform the logical or of two smi values and return a smi value.
    // If either argument is not a smi, jump to on_not_smis and retain
    // the original values of source registers. The destination register
    // may be changed if it's not one of the source registers.
    void SmiOrIfSmis(Register dst,
                     Register src1,
                     Register src2,
                     Label* on_not_smis,
                     Label::Distance near_jump = Label::kFar);
  
  
    // Simple comparison of smis.  Both sides must be known smis to use these,
    // otherwise use Cmp.
    void SmiCompare(Register smi1, Register smi2);
    void SmiCompare(Register dst, Smi* src);
    void SmiCompare(Register dst, const Operand& src);
    void SmiCompare(const Operand& dst, Register src);
    void SmiCompare(const Operand& dst, Smi* src);
    // Compare the int32 in src register to the value of the smi stored at dst.
    void SmiCompareInteger32(const Operand& dst, Register src);
    // Sets sign and zero flags depending on value of smi in register.
    void SmiTest(Register src);
  
    // Functions performing a check on a known or potential smi. Returns
    // a condition that is satisfied if the check is successful.
  
    // Is the value a tagged smi.
    Condition CheckSmi(Register src);
    Condition CheckSmi(const Operand& src);
  
    // Is the value a non-negative tagged smi.
    Condition CheckNonNegativeSmi(Register src);
  
    // Are both values tagged smis.
    Condition CheckBothSmi(Register first, Register second);
  
    // Are both values non-negative tagged smis.
    Condition CheckBothNonNegativeSmi(Register first, Register second);
  
    // Are either value a tagged smi.
    Condition CheckEitherSmi(Register first,
                             Register second,
                             Register scratch = kScratchRegister);
  
    // Is the value the minimum smi value (since we are using
    // two's complement numbers, negating the value is known to yield
    // a non-smi value).
    Condition CheckIsMinSmi(Register src);
  
    // Checks whether an 32-bit integer value is a valid for conversion
    // to a smi.
    Condition CheckInteger32ValidSmiValue(Register src);
  
    // Checks whether an 32-bit unsigned integer value is a valid for
    // conversion to a smi.
    Condition CheckUInteger32ValidSmiValue(Register src);
  
    // Check whether src is a Smi, and set dst to zero if it is a smi,
    // and to one if it isn't.
    void CheckSmiToIndicator(Register dst, Register src);
    void CheckSmiToIndicator(Register dst, const Operand& src);
  
    // Test-and-jump functions. Typically combines a check function
    // above with a conditional jump.
  
    // Jump if the value cannot be represented by a smi.
    void JumpIfNotValidSmiValue(Register src, Label* on_invalid,
                                Label::Distance near_jump = Label::kFar);
  
    // Jump if the unsigned integer value cannot be represented by a smi.
    void JumpIfUIntNotValidSmiValue(Register src, Label* on_invalid,
                                    Label::Distance near_jump = Label::kFar);
  
    // Jump to label if the value is a tagged smi.
    void JumpIfSmi(Register src,
                   Label* on_smi,
                   Label::Distance near_jump = Label::kFar);
  
    // Jump to label if the value is not a tagged smi.
    void JumpIfNotSmi(Register src,
                      Label* on_not_smi,
                      Label::Distance near_jump = Label::kFar);
  
    // Jump to label if the value is not a non-negative tagged smi.
    void JumpUnlessNonNegativeSmi(Register src,
                                  Label* on_not_smi,
                                  Label::Distance near_jump = Label::kFar);
  
    // Jump to label if the value, which must be a tagged smi, has value equal
    // to the constant.
    void JumpIfSmiEqualsConstant(Register src,
                                 Smi* constant,
                                 Label* on_equals,
                                 Label::Distance near_jump = Label::kFar);
  
    // Jump if either or both register are not smi values.
    void JumpIfNotBothSmi(Register src1,
                          Register src2,
                          Label* on_not_both_smi,
                          Label::Distance near_jump = Label::kFar);
  
    // Jump if either or both register are not non-negative smi values.
    void JumpUnlessBothNonNegativeSmi(Register src1, Register src2,
                                      Label* on_not_both_smi,
                                      Label::Distance near_jump = Label::kFar);
  
    // Operations on tagged smi values.
  
    // Smis represent a subset of integers. The subset is always equivalent to
    // a two's complement interpretation of a fixed number of bits.
  
    // Optimistically adds an integer constant to a supposed smi.
    // If the src is not a smi, or the result is not a smi, jump to
    // the label.
    void SmiTryAddConstant(Register dst,
                           Register src,
                           Smi* constant,
                           Label* on_not_smi_result,
                           Label::Distance near_jump = Label::kFar);
  
    // Add an integer constant to a tagged smi, giving a tagged smi as result.
    // No overflow testing on the result is done.
    void SmiAddConstant(Register dst, Register src, Smi* constant);
  
    // Add an integer constant to a tagged smi, giving a tagged smi as result.
    // No overflow testing on the result is done.
    void SmiAddConstant(const Operand& dst, Smi* constant);
  
    // Add an integer constant to a tagged smi, giving a tagged smi as result,
    // or jumping to a label if the result cannot be represented by a smi.
    void SmiAddConstant(Register dst,
                        Register src,
                        Smi* constant,
                        Label* on_not_smi_result,
                        Label::Distance near_jump = Label::kFar);
  
    // Subtract an integer constant from a tagged smi, giving a tagged smi as
    // result. No testing on the result is done. Sets the N and Z flags
    // based on the value of the resulting integer.
    void SmiSubConstant(Register dst, Register src, Smi* constant);
  
    // Subtract an integer constant from a tagged smi, giving a tagged smi as
    // result, or jumping to a label if the result cannot be represented by a smi.
    void SmiSubConstant(Register dst,
                        Register src,
                        Smi* constant,
                        Label* on_not_smi_result,
                        Label::Distance near_jump = Label::kFar);
  
    // Negating a smi can give a negative zero or too large positive value.
    // NOTICE: This operation jumps on success, not failure!
    void SmiNeg(Register dst,
                Register src,
                Label* on_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    // Adds smi values and return the result as a smi.
    // If dst is src1, then src1 will be destroyed, even if
    // the operation is unsuccessful.
    void SmiAdd(Register dst,
                Register src1,
                Register src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
    void SmiAdd(Register dst,
                Register src1,
                const Operand& src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    void SmiAdd(Register dst,
                Register src1,
                Register src2);
  
    // Subtracts smi values and return the result as a smi.
    // If dst is src1, then src1 will be destroyed, even if
    // the operation is unsuccessful.
    void SmiSub(Register dst,
                Register src1,
                Register src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    void SmiSub(Register dst,
                Register src1,
                Register src2);
  
    void SmiSub(Register dst,
                Register src1,
                const Operand& src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    void SmiSub(Register dst,
                Register src1,
                const Operand& src2);
  
    // Multiplies smi values and return the result as a smi,
    // if possible.
    // If dst is src1, then src1 will be destroyed, even if
    // the operation is unsuccessful.
    void SmiMul(Register dst,
                Register src1,
                Register src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    // Divides one smi by another and returns the quotient.
    // Clobbers rax and rdx registers.
    void SmiDiv(Register dst,
                Register src1,
                Register src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    // Divides one smi by another and returns the remainder.
    // Clobbers rax and rdx registers.
    void SmiMod(Register dst,
                Register src1,
                Register src2,
                Label* on_not_smi_result,
                Label::Distance near_jump = Label::kFar);
  
    // Bitwise operations.
    void SmiNot(Register dst, Register src);
    void SmiAnd(Register dst, Register src1, Register src2);
    void SmiOr(Register dst, Register src1, Register src2);
    void SmiXor(Register dst, Register src1, Register src2);
    void SmiAndConstant(Register dst, Register src1, Smi* constant);
    void SmiOrConstant(Register dst, Register src1, Smi* constant);
    void SmiXorConstant(Register dst, Register src1, Smi* constant);
  
    void SmiShiftLeftConstant(Register dst,
                              Register src,
                              int shift_value);
    void SmiShiftLogicalRightConstant(Register dst,
                                    Register src,
                                    int shift_value,
                                    Label* on_not_smi_result,
                                    Label::Distance near_jump = Label::kFar);
    void SmiShiftArithmeticRightConstant(Register dst,
                                         Register src,
                                         int shift_value);
  
    // Shifts a smi value to the left, and returns the result if that is a smi.
    // Uses and clobbers rcx, so dst may not be rcx.
    void SmiShiftLeft(Register dst,
                      Register src1,
                      Register src2);
    // Shifts a smi value to the right, shifting in zero bits at the top, and
    // returns the unsigned intepretation of the result if that is a smi.
    // Uses and clobbers rcx, so dst may not be rcx.
    void SmiShiftLogicalRight(Register dst,
                              Register src1,
                              Register src2,
                              Label* on_not_smi_result,
                              Label::Distance near_jump = Label::kFar);
    // Shifts a smi value to the right, sign extending the top, and
    // returns the signed intepretation of the result. That will always
    // be a valid smi value, since it's numerically smaller than the
    // original.
    // Uses and clobbers rcx, so dst may not be rcx.
    void SmiShiftArithmeticRight(Register dst,
                                 Register src1,
                                 Register src2);
  
    // Specialized operations
  
    // Select the non-smi register of two registers where exactly one is a
    // smi. If neither are smis, jump to the failure label.
    void SelectNonSmi(Register dst,
                      Register src1,
                      Register src2,
                      Label* on_not_smis,
                      Label::Distance near_jump = Label::kFar);
  
    // Converts, if necessary, a smi to a combination of number and
    // multiplier to be used as a scaled index.
    // The src register contains a *positive* smi value. The shift is the
    // power of two to multiply the index value by (e.g.
    // to index by smi-value * kPointerSize, pass the smi and kPointerSizeLog2).
    // The returned index register may be either src or dst, depending
    // on what is most efficient. If src and dst are different registers,
    // src is always unchanged.
    SmiIndex SmiToIndex(Register dst, Register src, int shift);
  
    // Converts a positive smi to a negative index.
    SmiIndex SmiToNegativeIndex(Register dst, Register src, int shift);
  
    // Add the value of a smi in memory to an int32 register.
    // Sets flags as a normal add.
    void AddSmiField(Register dst, const Operand& src);
  
    // Basic Smi operations.
    void Move(Register dst, Smi* source) {
      LoadSmiConstant(dst, source);
    }
  
    void Move(const Operand& dst, Smi* source) {
      Register constant = GetSmiConstant(source);
      movq(dst, constant);
    }
  
    void Push(Smi* smi);
    void Test(const Operand& dst, Smi* source);
  
  
    // ---------------------------------------------------------------------------
    // String macros.
  
    // If object is a string, its map is loaded into object_map.
    void JumpIfNotString(Register object,
                         Register object_map,
                         Label* not_string,
                         Label::Distance near_jump = Label::kFar);
  
  
    void JumpIfNotBothSequentialAsciiStrings(
        Register first_object,
        Register second_object,
        Register scratch1,
        Register scratch2,
        Label* on_not_both_flat_ascii,
        Label::Distance near_jump = Label::kFar);
  
    // Check whether the instance type represents a flat ASCII string. Jump to the
    // label if not. If the instance type can be scratched specify same register
    // for both instance type and scratch.
    void JumpIfInstanceTypeIsNotSequentialAscii(
        Register instance_type,
        Register scratch,
        Label*on_not_flat_ascii_string,
        Label::Distance near_jump = Label::kFar);
  
    void JumpIfBothInstanceTypesAreNotSequentialAscii(
        Register first_object_instance_type,
        Register second_object_instance_type,
        Register scratch1,
        Register scratch2,
        Label* on_fail,
        Label::Distance near_jump = Label::kFar);
  
    // ---------------------------------------------------------------------------
    // Macro instructions.
  
    // Load a register with a long value as efficiently as possible.
    void Set(Register dst, int64_t x);
    void Set(const Operand& dst, int64_t x);
  
    // Move if the registers are not identical.
    void Move(Register target, Register source);
  
    // Support for constant splitting.
    bool IsUnsafeInt(const int x);
    void SafeMove(Register dst, Smi* src);
    void SafePush(Smi* src);
  
    // Bit-field support.
    void TestBit(const Operand& dst, int bit_index);
  
    // Handle support
    void Move(Register dst, Handle<Object> source);
    void Move(const Operand& dst, Handle<Object> source);
    void Cmp(Register dst, Handle<Object> source);
    void Cmp(const Operand& dst, Handle<Object> source);
    void Cmp(Register dst, Smi* src);
    void Cmp(const Operand& dst, Smi* src);
    void Push(Handle<Object> source);
  
    // Load a heap object and handle the case of new-space objects by
    // indirecting via a global cell.
    void LoadHeapObject(Register result, Handle<HeapObject> object);
    void PushHeapObject(Handle<HeapObject> object);
  
    void LoadObject(Register result, Handle<Object> object) {
      if (object->IsHeapObject()) {
        LoadHeapObject(result, Handle<HeapObject>::cast(object));
      } else {
        Move(result, object);
      }
    }
  
    // Load a global cell into a register.
    void LoadGlobalCell(Register dst, Handle<JSGlobalPropertyCell> cell);
  
    // Emit code to discard a non-negative number of pointer-sized elements
    // from the stack, clobbering only the rsp register.
    void Drop(int stack_elements);
  
    void Call(Label* target) { call(target); }
  
    // Control Flow
    void Jump(Address destination, RelocInfo::Mode rmode);
    void Jump(ExternalReference ext);
    void Jump(Handle<Code> code_object, RelocInfo::Mode rmode);
  
    void Call(Address destination, RelocInfo::Mode rmode);
    void Call(ExternalReference ext);
    void Call(Handle<Code> code_object,
              RelocInfo::Mode rmode,
              TypeFeedbackId ast_id = TypeFeedbackId::None());
  
    // The size of the code generated for different call instructions.
    int CallSize(Address destination, RelocInfo::Mode rmode) {
      return kCallInstructionLength;
    }
    int CallSize(ExternalReference ext);
    int CallSize(Handle<Code> code_object) {
      // Code calls use 32-bit relative addressing.
      return kShortCallInstructionLength;
    }
    int CallSize(Register target) {
      // Opcode: REX_opt FF /2 m64
      return (target.high_bit() != 0) ? 3 : 2;
    }
    int CallSize(const Operand& target) {
      // Opcode: REX_opt FF /2 m64
      return (target.requires_rex() ? 2 : 1) + target.operand_size();
    }
  
    // Emit call to the code we are currently generating.
    void CallSelf() {
      Handle<Code> self(reinterpret_cast<Code**>(CodeObject().location()));
      Call(self, RelocInfo::CODE_TARGET);
    }
  
    // Non-x64 instructions.
    // Push/pop all general purpose registers.
    // Does not push rsp/rbp nor any of the assembler's special purpose registers
    // (kScratchRegister, kSmiConstantRegister, kRootRegister).
    void Pushad();
    void Popad();
    // Sets the stack as after performing Popad, without actually loading the
    // registers.
    void Dropad();
  
    // Compare object type for heap object.
    // Always use unsigned comparisons: above and below, not less and greater.
    // Incoming register is heap_object and outgoing register is map.
    // They may be the same register, and may be kScratchRegister.
    void CmpObjectType(Register heap_object, InstanceType type, Register map);
  
    // Compare instance type for map.
    // Always use unsigned comparisons: above and below, not less and greater.
    void CmpInstanceType(Register map, InstanceType type);
  
    // Check if a map for a JSObject indicates that the object has fast elements.
    // Jump to the specified label if it does not.
    void CheckFastElements(Register map,
                           Label* fail,
                           Label::Distance distance = Label::kFar);
  
    // Check if a map for a JSObject indicates that the object can have both smi
    // and HeapObject elements.  Jump to the specified label if it does not.
    void CheckFastObjectElements(Register map,
                                 Label* fail,
                                 Label::Distance distance = Label::kFar);
  
    // Check if a map for a JSObject indicates that the object has fast smi only
    // elements.  Jump to the specified label if it does not.
    void CheckFastSmiElements(Register map,
                              Label* fail,
                              Label::Distance distance = Label::kFar);
  
    // Check to see if maybe_number can be stored as a double in
    // FastDoubleElements. If it can, store it at the index specified by index in
    // the FastDoubleElements array elements, otherwise jump to fail.  Note that
    // index must not be smi-tagged.
    void StoreNumberToDoubleElements(Register maybe_number,
                                     Register elements,
                                     Register index,
                                     XMMRegister xmm_scratch,
                                     Label* fail,
                                     int elements_offset = 0);
  
    // Compare an object's map with the specified map and its transitioned
    // elements maps if mode is ALLOW_ELEMENT_TRANSITION_MAPS. FLAGS are set with
    // result of map compare. If multiple map compares are required, the compare
    // sequences branches to early_success.
    void CompareMap(Register obj,
                    Handle<Map> map,
                    Label* early_success,
                    CompareMapMode mode = REQUIRE_EXACT_MAP);
  
    // Check if the map of an object is equal to a specified map and branch to
    // label if not. Skip the smi check if not required (object is known to be a
    // heap object). If mode is ALLOW_ELEMENT_TRANSITION_MAPS, then also match
    // against maps that are ElementsKind transition maps of the specified map.
    void CheckMap(Register obj,
                  Handle<Map> map,
                  Label* fail,
                  SmiCheckType smi_check_type,
                  CompareMapMode mode = REQUIRE_EXACT_MAP);
  
    // Check if the map of an object is equal to a specified map and branch to a
    // specified target if equal. Skip the smi check if not required (object is
    // known to be a heap object)
    void DispatchMap(Register obj,
                     Handle<Map> map,
                     Handle<Code> success,
                     SmiCheckType smi_check_type);
  
    // Check if the object in register heap_object is a string. Afterwards the
    // register map contains the object map and the register instance_type
    // contains the instance_type. The registers map and instance_type can be the
    // same in which case it contains the instance type afterwards. Either of the
    // registers map and instance_type can be the same as heap_object.
    Condition IsObjectStringType(Register heap_object,
                                 Register map,
                                 Register instance_type);
  
    // FCmp compares and pops the two values on top of the FPU stack.
    // The flag results are similar to integer cmp, but requires unsigned
    // jcc instructions (je, ja, jae, jb, jbe, je, and jz).
    void FCmp();
  
    void ClampUint8(Register reg);
  
    void ClampDoubleToUint8(XMMRegister input_reg,
                            XMMRegister temp_xmm_reg,
                            Register result_reg);
  
    void LoadUint32(XMMRegister dst, Register src, XMMRegister scratch);
  
    void LoadInstanceDescriptors(Register map, Register descriptors);
    void EnumLength(Register dst, Register map);
    void NumberOfOwnDescriptors(Register dst, Register map);
  
    template<typename Field>
    void DecodeField(Register reg) {
      static const int shift = Field::kShift + kSmiShift;
      static const int mask = Field::kMask >> Field::kShift;
      shr(reg, Immediate(shift));
      and_(reg, Immediate(mask));
      shl(reg, Immediate(kSmiShift));
    }
  
    // Abort execution if argument is not a number, enabled via --debug-code.
    void AssertNumber(Register object);
  
    // Abort execution if argument is a smi, enabled via --debug-code.
    void AssertNotSmi(Register object);
  
    // Abort execution if argument is not a smi, enabled via --debug-code.
    void AssertSmi(Register object);
    void AssertSmi(const Operand& object);
  
    // Abort execution if a 64 bit register containing a 32 bit payload does not
    // have zeros in the top 32 bits, enabled via --debug-code.
    void AssertZeroExtended(Register reg);
  
    // Abort execution if argument is not a string, enabled via --debug-code.
    void AssertString(Register object);
  
    // Abort execution if argument is not the root value with the given index,
    // enabled via --debug-code.
    void AssertRootValue(Register src,
                         Heap::RootListIndex root_value_index,
                         const char* message);
  
    // ---------------------------------------------------------------------------
    // Exception handling
  
    // Push a new try handler and link it into try handler chain.
    void PushTryHandler(StackHandler::Kind kind, int handler_index);
  
    // Unlink the stack handler on top of the stack from the try handler chain.
    void PopTryHandler();
  
    // Activate the top handler in the try hander chain and pass the
    // thrown value.
    void Throw(Register value);
  
    // Propagate an uncatchable exception out of the current JS stack.
    void ThrowUncatchable(Register value);
  
    // ---------------------------------------------------------------------------
    // Inline caching support
  
    // Generate code for checking access rights - used for security checks
    // on access to global objects across environments. The holder register
    // is left untouched, but the scratch register and kScratchRegister,
    // which must be different, are clobbered.
    void CheckAccessGlobalProxy(Register holder_reg,
                                Register scratch,
                                Label* miss);
  
    void GetNumberHash(Register r0, Register scratch);
  
    void LoadFromNumberDictionary(Label* miss,
                                  Register elements,
                                  Register key,
                                  Register r0,
                                  Register r1,
                                  Register r2,
                                  Register result);
  
  
    // ---------------------------------------------------------------------------
    // Allocation support
  
    // Allocate an object in new space. If the new space is exhausted control
    // continues at the gc_required label. The allocated object is returned in
    // result and end of the new object is returned in result_end. The register
    // scratch can be passed as no_reg in which case an additional object
    // reference will be added to the reloc info. The returned pointers in result
    // and result_end have not yet been tagged as heap objects. If
    // result_contains_top_on_entry is true the content of result is known to be
    // the allocation top on entry (could be result_end from a previous call to
    // AllocateInNewSpace). If result_contains_top_on_entry is true scratch
    // should be no_reg as it is never used.
    void AllocateInNewSpace(int object_size,
                            Register result,
                            Register result_end,
                            Register scratch,
                            Label* gc_required,
                            AllocationFlags flags);
  
    void AllocateInNewSpace(int header_size,
                            ScaleFactor element_size,
                            Register element_count,
                            Register result,
                            Register result_end,
                            Register scratch,
                            Label* gc_required,
                            AllocationFlags flags);
  
    void AllocateInNewSpace(Register object_size,
                            Register result,
                            Register result_end,
                            Register scratch,
                            Label* gc_required,
                            AllocationFlags flags);
  
    // Undo allocation in new space. The object passed and objects allocated after
    // it will no longer be allocated. Make sure that no pointers are left to the
    // object(s) no longer allocated as they would be invalid when allocation is
    // un-done.
    void UndoAllocationInNewSpace(Register object);
  
    // Allocate a heap number in new space with undefined value. Returns
    // tagged pointer in result register, or jumps to gc_required if new
    // space is full.
    void AllocateHeapNumber(Register result,
                            Register scratch,
                            Label* gc_required);
  
    // Allocate a sequential string. All the header fields of the string object
    // are initialized.
    void AllocateTwoByteString(Register result,
                               Register length,
                               Register scratch1,
                               Register scratch2,
                               Register scratch3,
                               Label* gc_required);
    void AllocateAsciiString(Register result,
                             Register length,
                             Register scratch1,
                             Register scratch2,
                             Register scratch3,
                             Label* gc_required);
  
    // Allocate a raw cons string object. Only the map field of the result is
    // initialized.
    void AllocateTwoByteConsString(Register result,
                            Register scratch1,
                            Register scratch2,
                            Label* gc_required);
    void AllocateAsciiConsString(Register result,
                                 Register scratch1,
                                 Register scratch2,
                                 Label* gc_required);
  
    // Allocate a raw sliced string object. Only the map field of the result is
    // initialized.
    void AllocateTwoByteSlicedString(Register result,
                              Register scratch1,
                              Register scratch2,
                              Label* gc_required);
    void AllocateAsciiSlicedString(Register result,
                                   Register scratch1,
                                   Register scratch2,
                                   Label* gc_required);
  
    // ---------------------------------------------------------------------------
    // Support functions.
  
    // Check if result is zero and op is negative.
    void NegativeZeroTest(Register result, Register op, Label* then_label);
  
    // Check if result is zero and op is negative in code using jump targets.
    void NegativeZeroTest(CodeGenerator* cgen,
                          Register result,
                          Register op,
                          JumpTarget* then_target);
  
    // Check if result is zero and any of op1 and op2 are negative.
    // Register scratch is destroyed, and it must be different from op2.
    void NegativeZeroTest(Register result, Register op1, Register op2,
                          Register scratch, Label* then_label);
  
    // Try to get function prototype of a function and puts the value in
    // the result register. Checks that the function really is a
    // function and jumps to the miss label if the fast checks fail. The
    // function register will be untouched; the other register may be
    // clobbered.
    void TryGetFunctionPrototype(Register function,
                                 Register result,
                                 Label* miss,
                                 bool miss_on_bound_function = false);
  
    // Generates code for reporting that an illegal operation has
    // occurred.
    void IllegalOperation(int num_arguments);
  
    // Picks out an array index from the hash field.
    // Register use:
    //   hash - holds the index's hash. Clobbered.
    //   index - holds the overwritten index on exit.
    void IndexFromHash(Register hash, Register index);
  
    // Find the function context up the context chain.
    void LoadContext(Register dst, int context_chain_length);
  
    // Conditionally load the cached Array transitioned map of type
    // transitioned_kind from the native context if the map in register
    // map_in_out is the cached Array map in the native context of
    // expected_kind.
    void LoadTransitionedArrayMapConditional(
        ElementsKind expected_kind,
        ElementsKind transitioned_kind,
        Register map_in_out,
        Register scratch,
        Label* no_map_match);
  
    // Load the initial map for new Arrays from a JSFunction.
    void LoadInitialArrayMap(Register function_in,
                             Register scratch,
                             Register map_out,
                             bool can_have_holes);
  
    // Load the global function with the given index.
    void LoadGlobalFunction(int index, Register function);
  
    // Load the initial map from the global function. The registers
    // function and map can be the same.
    void LoadGlobalFunctionInitialMap(Register function, Register map);
  
    // ---------------------------------------------------------------------------
    // Runtime calls
  
    // Call a code stub.
    void CallStub(CodeStub* stub, TypeFeedbackId ast_id = TypeFeedbackId::None());
  
    // Tail call a code stub (jump).
    void TailCallStub(CodeStub* stub);
  
    // Return from a code stub after popping its arguments.
    void StubReturn(int argc);
  
    // Call a runtime routine.
    void CallRuntime(const Runtime::Function* f, int num_arguments);
  
    // Call a runtime function and save the value of XMM registers.
    void CallRuntimeSaveDoubles(Runtime::FunctionId id);
  
    // Convenience function: Same as above, but takes the fid instead.
    void CallRuntime(Runtime::FunctionId id, int num_arguments);
  
    // Convenience function: call an external reference.
    void CallExternalReference(const ExternalReference& ext,
                               int num_arguments);
  
    // Tail call of a runtime routine (jump).
    // Like JumpToExternalReference, but also takes care of passing the number
    // of parameters.
    void TailCallExternalReference(const ExternalReference& ext,
                                   int num_arguments,
                                   int result_size);
  
    // Convenience function: tail call a runtime routine (jump).
    void TailCallRuntime(Runtime::FunctionId fid,
                         int num_arguments,
                         int result_size);
  
    // Jump to a runtime routine.
    void JumpToExternalReference(const ExternalReference& ext, int result_size);
  
    // Prepares stack to put arguments (aligns and so on).  WIN64 calling
    // convention requires to put the pointer to the return value slot into
    // rcx (rcx must be preserverd until CallApiFunctionAndReturn).  Saves
    // context (rsi).  Clobbers rax.  Allocates arg_stack_space * kPointerSize
    // inside the exit frame (not GCed) accessible via StackSpaceOperand.
    void PrepareCallApiFunction(int arg_stack_space);
  
    // Calls an API function.  Allocates HandleScope, extracts returned value
    // from handle and propagates exceptions.  Clobbers r14, r15, rbx and
    // caller-save registers.  Restores context.  On return removes
    // stack_space * kPointerSize (GCed).
    void CallApiFunctionAndReturn(Address function_address, int stack_space);
  
    // Before calling a C-function from generated code, align arguments on stack.
    // After aligning the frame, arguments must be stored in esp[0], esp[4],
    // etc., not pushed. The argument count assumes all arguments are word sized.
    // The number of slots reserved for arguments depends on platform. On Windows
    // stack slots are reserved for the arguments passed in registers. On other
    // platforms stack slots are only reserved for the arguments actually passed
    // on the stack.
    void PrepareCallCFunction(int num_arguments);
  
    // Calls a C function and cleans up the space for arguments allocated
    // by PrepareCallCFunction. The called function is not allowed to trigger a
    // garbage collection, since that might move the code and invalidate the
    // return address (unless this is somehow accounted for by the called
    // function).
    void CallCFunction(ExternalReference function, int num_arguments);
    void CallCFunction(Register function, int num_arguments);
  
    // Calculate the number of stack slots to reserve for arguments when calling a
    // C function.
    int ArgumentStackSlotsForCFunctionCall(int num_arguments);
  
    // ---------------------------------------------------------------------------
    // Utilities
  
    void Ret();
  
    // Return and drop arguments from stack, where the number of arguments
    // may be bigger than 2^16 - 1.  Requires a scratch register.
    void Ret(int bytes_dropped, Register scratch);
  
    Handle<Object> CodeObject() {
      ASSERT(!code_object_.is_null());
      return code_object_;
    }
  
    // Copy length bytes from source to destination.
    // Uses scratch register internally (if you have a low-eight register
    // free, do use it, otherwise kScratchRegister will be used).
    // The min_length is a minimum limit on the value that length will have.
    // The algorithm has some special cases that might be omitted if the string
    // is known to always be long.
    void CopyBytes(Register destination,
                   Register source,
                   Register length,
                   int min_length = 0,
                   Register scratch = kScratchRegister);
  
    // Initialize fields with filler values.  Fields starting at |start_offset|
    // not including end_offset are overwritten with the value in |filler|.  At
    // the end the loop, |start_offset| takes the value of |end_offset|.
    void InitializeFieldsWithFiller(Register start_offset,
                                    Register end_offset,
                                    Register filler);
  
  
    // ---------------------------------------------------------------------------
    // StatsCounter support
  
    void SetCounter(StatsCounter* counter, int value);
    void IncrementCounter(StatsCounter* counter, int value);
    void DecrementCounter(StatsCounter* counter, int value);
  
  
    // ---------------------------------------------------------------------------
    // Debugging
  
    // Calls Abort(msg) if the condition cc is not satisfied.
    // Use --debug_code to enable.
    void Assert(Condition cc, const char* msg);
  
    void AssertFastElements(Register elements);
  
    // Like Assert(), but always enabled.
    void Check(Condition cc, const char* msg);
  
    // Print a message to stdout and abort execution.
    void Abort(const char* msg);
  
    // Check that the stack is aligned.
    void CheckStackAlignment();
  
    // Verify restrictions about code generated in stubs.
    void set_generating_stub(bool value) { generating_stub_ = value; }
    bool generating_stub() { return generating_stub_; }
    void set_allow_stub_calls(bool value) { allow_stub_calls_ = value; }
    bool allow_stub_calls() { return allow_stub_calls_; }
    void set_has_frame(bool value) { has_frame_ = value; }
    bool has_frame() { return has_frame_; }
    inline bool AllowThisStubCall(CodeStub* stub);
  
    static int SafepointRegisterStackIndex(Register reg) {
      return SafepointRegisterStackIndex(reg.code());
    }
  
    // Activation support.
    void EnterFrame(StackFrame::Type type);
    void LeaveFrame(StackFrame::Type type);
  
    // Expects object in rax and returns map with validated enum cache
    // in rax.  Assumes that any other register can be used as a scratch.
    void CheckEnumCache(Register null_value,
                        Label* call_runtime);
  
    // AllocationSiteInfo support. Arrays may have an associated
    // AllocationSiteInfo object that can be checked for in order to pretransition
    // to another type.
    // On entry, receiver_reg should point to the array object.
    // scratch_reg gets clobbered.
    // If allocation info is present, condition flags are set to equal
    void TestJSArrayForAllocationSiteInfo(Register receiver_reg,
                                          Register scratch_reg);
  
   private:
    // Order general registers are pushed by Pushad.
    // rax, rcx, rdx, rbx, rsi, rdi, r8, r9, r11, r14, r15.
    static const int kSafepointPushRegisterIndices[Register::kNumRegisters];
    static const int kNumSafepointSavedRegisters = 11;
    static const int kSmiShift = kSmiTagSize + kSmiShiftSize;
  
    bool generating_stub_;
    bool allow_stub_calls_;
    bool has_frame_;
    bool root_array_available_;
  
    // Returns a register holding the smi value. The register MUST NOT be
    // modified. It may be the "smi 1 constant" register.
    Register GetSmiConstant(Smi* value);
  
    intptr_t RootRegisterDelta(ExternalReference other);
  
    // Moves the smi value to the destination register.
    void LoadSmiConstant(Register dst, Smi* value);
  
    // This handle will be patched with the code object on installation.
    Handle<Object> code_object_;
  
    // Helper functions for generating invokes.
    void InvokePrologue(const ParameterCount& expected,
                        const ParameterCount& actual,
                        Handle<Code> code_constant,
                        Register code_register,
                        Label* done,
                        bool* definitely_mismatches,
                        InvokeFlag flag,
                        Label::Distance near_jump = Label::kFar,
                        const CallWrapper& call_wrapper = NullCallWrapper(),
                        CallKind call_kind = CALL_AS_METHOD);
  
    void EnterExitFramePrologue(bool save_rax);
  
    // Allocates arg_stack_space * kPointerSize memory (not GCed) on the stack
    // accessible via StackSpaceOperand.
    void EnterExitFrameEpilogue(int arg_stack_space, bool save_doubles);
  
    void LeaveExitFrameEpilogue();
  
    // Allocation support helpers.
    // Loads the top of new-space into the result register.
    // Otherwise the address of the new-space top is loaded into scratch (if
    // scratch is valid), and the new-space top is loaded into result.
    void LoadAllocationTopHelper(Register result,
                                 Register scratch,
                                 AllocationFlags flags);
    // Update allocation top with value in result_end register.
    // If scratch is valid, it contains the address of the allocation top.
    void UpdateAllocationTopHelper(Register result_end, Register scratch);
  
    // Helper for PopHandleScope.  Allowed to perform a GC and returns
    // NULL if gc_allowed.  Does not perform a GC if !gc_allowed, and
    // possibly returns a failure object indicating an allocation failure.
    Object* PopHandleScopeHelper(Register saved,
                                 Register scratch,
                                 bool gc_allowed);
  
    // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
    void InNewSpace(Register object,
                    Register scratch,
                    Condition cc,
                    Label* branch,
                    Label::Distance distance = Label::kFar);
  
    // Helper for finding the mark bits for an address.  Afterwards, the
    // bitmap register points at the word with the mark bits and the mask
    // the position of the first bit.  Uses rcx as scratch and leaves addr_reg
    // unchanged.
    inline void GetMarkBits(Register addr_reg,
                            Register bitmap_reg,
                            Register mask_reg);
  
    // Helper for throwing exceptions.  Compute a handler address and jump to
    // it.  See the implementation for register usage.
    void JumpToHandlerEntry();
  
    // Compute memory operands for safepoint stack slots.
    Operand SafepointRegisterSlot(Register reg);
    static int SafepointRegisterStackIndex(int reg_code) {
      return kNumSafepointRegisters - kSafepointPushRegisterIndices[reg_code] - 1;
    }
  
    // Needs access to SafepointRegisterStackIndex for compiled frame
    // traversal.
    friend class StandardFrame;
  };
  
  
  // The code patcher is used to patch (typically) small parts of code e.g. for
  // debugging and other types of instrumentation. When using the code patcher
  // the exact number of bytes specified must be emitted. Is not legal to emit
  // relocation information. If any of these constraints are violated it causes
  // an assertion.
  class CodePatcher {
   public:
    CodePatcher(byte* address, int size);
    virtual ~CodePatcher();
  
    // Macro assembler to emit code.
    MacroAssembler* masm() { return &masm_; }
  
   private:
    byte* address_;  // The address of the code being patched.
    int size_;  // Number of bytes of the expected patch size.
    MacroAssembler masm_;  // Macro assembler used to generate the code.
  };
  
  
  // -----------------------------------------------------------------------------
  // Static helper functions.
  
  // Generate an Operand for loading a field from an object.
  inline Operand FieldOperand(Register object, int offset) {
    return Operand(object, offset - kHeapObjectTag);
  }
  
  
  // Generate an Operand for loading an indexed field from an object.
  inline Operand FieldOperand(Register object,
                              Register index,
                              ScaleFactor scale,
                              int offset) {
    return Operand(object, index, scale, offset - kHeapObjectTag);
  }
  
  
  inline Operand ContextOperand(Register context, int index) {
    return Operand(context, Context::SlotOffset(index));
  }
  
  
  inline Operand GlobalObjectOperand() {
    return ContextOperand(rsi, Context::GLOBAL_OBJECT_INDEX);
  }
  
  
  // Provides access to exit frame stack space (not GCed).
  inline Operand StackSpaceOperand(int index) {
  #ifdef _WIN64
    const int kShaddowSpace = 4;
    return Operand(rsp, (index + kShaddowSpace) * kPointerSize);
  #else
    return Operand(rsp, index * kPointerSize);
  #endif
  }
  
  
  
  #ifdef GENERATED_CODE_COVERAGE
  extern void LogGeneratedCodeCoverage(const char* file_line);
  #define CODE_COVERAGE_STRINGIFY(x) #x
  #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
  #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
  #define ACCESS_MASM(masm) {                                                  \
      Address x64_coverage_function = FUNCTION_ADDR(LogGeneratedCodeCoverage); \
      masm->pushfq();                                                          \
      masm->Pushad();                                                          \
      masm->push(Immediate(reinterpret_cast<int>(&__FILE_LINE__)));            \
      masm->Call(x64_coverage_function, RelocInfo::EXTERNAL_REFERENCE);        \
      masm->pop(rax);                                                          \
      masm->Popad();                                                           \
      masm->popfq();                                                           \
    }                                                                          \
    masm->
  #else
  #define ACCESS_MASM(masm) masm->
  #endif
  
  } }  // namespace v8::internal
  
  #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_
  