Implement code patcher for x64

src/x64/macro-assembler-x64.h

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 362 matching lines @@
 
   // Allocation support helpers.
   void LoadAllocationTopHelper(Register result,
                                Register result_end,
                                Register scratch,
                                AllocationFlags flags);
   void UpdateAllocationTopHelper(Register result_end, Register scratch);
 };
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
+// 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.
+};
+#endif  // ENABLE_DEBUGGER_SUPPORT
+
+
 // -----------------------------------------------------------------------------
 // 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.
@@ skipping 23 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_