src/x64/macro-assembler-x64.h

// Copyright 2009 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       copyright notice, this list of conditions and the following
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#ifndef V8_X64_MACRO_ASSEMBLER_X64_H_
#define V8_X64_MACRO_ASSEMBLER_X64_H_

#include "assembler.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.
static const Register kScratchRegister = { 10 };  // r10.
static const Register kRootRegister = { 13 };     // r13

// Convenience for platform-independent signatures.
typedef Operand MemOperand;

// 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:
  MacroAssembler(void* buffer, int size);

  void LoadRoot(Register destination, Heap::RootListIndex index);
  void CompareRoot(Register with, Heap::RootListIndex index);
  void CompareRoot(Operand with, Heap::RootListIndex index);
  void PushRoot(Heap::RootListIndex index);

  // ---------------------------------------------------------------------------
  // GC Support

  // Set the remembered set bit for [object+offset].
  // object is the object being stored into, value is the object being stored.
  // If offset is zero, then the scratch register contains the array index into
  // the elements array represented as a Smi.
  // All registers are clobbered by the operation.
  void RecordWrite(Register object,
                   int offset,
                   Register value,
                   Register scratch);

  // Set the remembered set bit for [object+offset].
  // The value is known to not be a smi.
  // object is the object being stored into, value is the object being stored.
  // If offset is zero, then the scratch register contains the array index into
  // the elements array represented as a Smi.
  // All registers are clobbered by the operation.
  void RecordWriteNonSmi(Register object,
                         int offset,
                         Register value,
                         Register scratch);


#ifdef ENABLE_DEBUGGER_SUPPORT
  // ---------------------------------------------------------------------------
  // Debugger Support

  void SaveRegistersToMemory(RegList regs);
  void RestoreRegistersFromMemory(RegList regs);
  void PushRegistersFromMemory(RegList regs);
  void PopRegistersToMemory(RegList regs);
  void CopyRegistersFromStackToMemory(Register base,
                                      Register scratch,
                                      RegList regs);
  void DebugBreak();
#endif

  // ---------------------------------------------------------------------------
  // Stack limit support

  // Do simple test for stack overflow. This doesn't handle an overflow.
  void StackLimitCheck(Label* on_stack_limit_hit);

  // ---------------------------------------------------------------------------
  // Activation frames

  void EnterInternalFrame() { EnterFrame(StackFrame::INTERNAL); }
  void LeaveInternalFrame() { LeaveFrame(StackFrame::INTERNAL); }

  void EnterConstructFrame() { EnterFrame(StackFrame::CONSTRUCT); }
  void LeaveConstructFrame() { LeaveFrame(StackFrame::CONSTRUCT); }

  // 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.
  void EnterExitFrame(ExitFrame::Mode mode, int result_size = 1);

  // 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(ExitFrame::Mode mode, int result_size = 1);


  // ---------------------------------------------------------------------------
  // JavaScript invokes

  // Invoke the JavaScript function code by either calling or jumping.
  void InvokeCode(Register code,
                  const ParameterCount& expected,
                  const ParameterCount& actual,
                  InvokeFlag flag);

  void InvokeCode(Handle<Code> code,
                  const ParameterCount& expected,
                  const ParameterCount& actual,
                  RelocInfo::Mode rmode,
                  InvokeFlag flag);

  // 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);

  void InvokeFunction(JSFunction* function,
                      const ParameterCount& actual,
                      InvokeFlag flag);

  // 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);

  // 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.

  // 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 integer.
  void Integer32ToSmi(Register dst, Register src);

  // Tag an integer value if possible, or jump the integer value cannot be
  // represented as a smi. Only uses the low 32 bit of the src registers.
  // NOTICE: Destroys the dst register even if unsuccessful!
  void Integer32ToSmi(Register dst, Register src, Label* on_overflow);

  // 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);

  // Convert smi to 64-bit integer (sign extended if necessary).
  void SmiToInteger64(Register dst, Register 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);

  // Simple comparison of smis.
  void SmiCompare(Register dst, Register src);
  void SmiCompare(Register dst, Smi* src);
  void SmiCompare(const Operand& dst, Register src);
  void SmiCompare(const Operand& dst, Smi* 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);

  // Is the value a positive tagged smi.
  Condition CheckPositiveSmi(Register src);

  // Are both values tagged smis.
  Condition CheckBothSmi(Register first, Register second);

  // Are both values tagged smis.
  Condition CheckBothPositiveSmi(Register first, Register second);

  // Are either value a tagged smi.
  Condition CheckEitherSmi(Register first, Register second);

  // 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);

  // 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);

  // Jump if the unsigned integer value cannot be represented by a smi.
  void JumpIfUIntNotValidSmiValue(Register src, Label* on_invalid);

  // Jump to label if the value is a tagged smi.
  void JumpIfSmi(Register src, Label* on_smi);

  // Jump to label if the value is not a tagged smi.
  void JumpIfNotSmi(Register src, Label* on_not_smi);

  // Jump to label if the value is not a positive tagged smi.
  void JumpIfNotPositiveSmi(Register src, Label* on_not_smi);

  // 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);

  // Jump if either or both register are not smi values.
  void JumpIfNotBothSmi(Register src1, Register src2, Label* on_not_both_smi);

  // Jump if either or both register are not positive smi values.
  void JumpIfNotBothPositiveSmi(Register src1, Register src2,
                                Label* on_not_both_smi);

  // 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);

  // 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,
  // 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);

  // Subtract an integer constant from a tagged smi, giving a tagged smi as
  // result. No testing on the result is done.
  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);

  // 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);

  // 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);

  // 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);

  // 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);

  // 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);

  // 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);

  // 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,
                            Label* on_not_smi_result);
  void SmiShiftLogicalRightConstant(Register dst,
                                  Register src,
                                  int shift_value,
                                  Label* on_not_smi_result);
  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,
                    Label* on_not_smi_result);
  // 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);
  // 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);

  // 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);

  // Basic Smi operations.
  void Move(Register dst, Smi* source) {
    Set(dst, reinterpret_cast<int64_t>(source));
  }

  void Move(const Operand& dst, Smi* source) {
    Set(dst, reinterpret_cast<int64_t>(source));
  }

  void Push(Smi* smi);
  void Test(const Operand& dst, Smi* source);

  // ---------------------------------------------------------------------------
  // String macros.
  void JumpIfNotBothSequentialAsciiStrings(Register first_object,
                                           Register second_object,
                                           Register scratch1,
                                           Register scratch2,
                                           Label* on_not_both_flat_ascii);

  // 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);

  void JumpIfBothInstanceTypesAreNotSequentialAscii(
      Register first_object_instance_type,
      Register second_object_instance_type,
      Register scratch1,
      Register scratch2,
      Label* on_fail);

  // ---------------------------------------------------------------------------
  // 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);

  // 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 Push(Handle<Object> source);

  // 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);

  // 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 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)
  void CheckMap(Register obj,
                Handle<Map> map,
                Label* fail,
                bool is_heap_object);

  // 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 is similar to integer cmp, but requires unsigned
  // jcc instructions (je, ja, jae, jb, jbe, je, and jz).
  void FCmp();

  // Abort execution if argument is not a number. Used in debug code.
  void AbortIfNotNumber(Register object, const char* msg);

  // Abort execution if argument is not a smi. Used in debug code.
  void AbortIfNotSmi(Register object, const char* msg);

  // ---------------------------------------------------------------------------
  // Exception handling

  // Push a new try handler and link into try handler chain.  The return
  // address must be pushed before calling this helper.
  void PushTryHandler(CodeLocation try_location, HandlerType type);

  // Unlink the stack handler on top of the stack from the try handler chain.
  void PopTryHandler();

  // ---------------------------------------------------------------------------
  // Inline caching support

  // Generates code that verifies that the maps of objects in the
  // prototype chain of object hasn't changed since the code was
  // generated and branches to the miss label if any map has. If
  // necessary the function also generates code for security check
  // in case of global object holders. The scratch and holder
  // registers are always clobbered, but the object register is only
  // clobbered if it the same as the holder register. The function
  // returns a register containing the holder - either object_reg or
  // holder_reg.
  Register CheckMaps(JSObject* object, Register object_reg,
                     JSObject* holder, Register holder_reg,
                     Register scratch, Label* miss);

  // 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);


  // ---------------------------------------------------------------------------
  // 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 AllocateConsString(Register result,
                          Register scratch1,
                          Register scratch2,
                          Label* gc_required);
  void AllocateAsciiConsString(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);

  // Generates code for reporting that an illegal operation has
  // occurred.
  void IllegalOperation(int num_arguments);

  // Find the function context up the context chain.
  void LoadContext(Register dst, int context_chain_length);

  // ---------------------------------------------------------------------------
  // Runtime calls

  // Call a code stub.
  void CallStub(CodeStub* stub);

  // 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(Runtime::Function* f, int num_arguments);

  // 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);

  // 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();

  Handle<Object> CodeObject() { return code_object_; }


  // ---------------------------------------------------------------------------
  // 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);

  // 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_; }

 private:
  bool generating_stub_;
  bool allow_stub_calls_;
  // 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,
                      InvokeFlag flag);

  // Activation support.
  void EnterFrame(StackFrame::Type type);
  void LeaveFrame(StackFrame::Type type);

  // Allocation support helpers.
  void LoadAllocationTopHelper(Register result,
                               Register result_end,
                               Register scratch,
                               AllocationFlags flags);
  void UpdateAllocationTopHelper(Register result_end, Register scratch);
};


// 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.
static inline Operand FieldOperand(Register object, int offset) {
  return Operand(object, offset - kHeapObjectTag);
}


// Generate an Operand for loading an indexed field from an object.
static inline Operand FieldOperand(Register object,
                                   Register index,
                                   ScaleFactor scale,
                                   int offset) {
  return Operand(object, index, scale, offset - kHeapObjectTag);
}


#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) {                                               \
    byte* x64_coverage_function =                                         \
        reinterpret_cast<byte*>(FUNCTION_ADDR(LogGeneratedCodeCoverage)); \
    masm->pushfd();                                                       \
    masm->pushad();                                                       \
    masm->push(Immediate(reinterpret_cast<int>(&__FILE_LINE__)));         \
    masm->call(x64_coverage_function, RelocInfo::RUNTIME_ENTRY);          \
    masm->pop(rax);                                                       \
    masm->popad();                                                        \
    masm->popfd();                                                        \
  }                                                                       \
  masm->
#else
#define ACCESS_MASM(masm) masm->
#endif


} }  // namespace v8::internal

#endif  // V8_X64_MACRO_ASSEMBLER_X64_H_