Add a HBreak instruction for debugging

src/x64/lithium-x64.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 71 matching lines @@
   V(ClassOfTestAndBranch)                       \
   V(CmpConstantEqAndBranch)                     \
   V(CmpIDAndBranch)                             \
   V(CmpObjectEqAndBranch)                       \
   V(CmpMapAndBranch)                            \
   V(CmpT)                                       \
   V(ConstantD)                                  \
   V(ConstantI)                                  \
   V(ConstantT)                                  \
   V(Context)                                    \
+  V(DebugBreak)                                 \
   V(DeclareGlobals)                             \
   V(DeleteProperty)                             \
   V(Deoptimize)                                 \
   V(DivI)                                       \
   V(DoubleToI)                                  \
   V(DummyUse)                                   \
   V(ElementsKind)                               \
   V(FixedArrayBaseLength)                       \
   V(MapEnumLength)                              \
   V(FunctionLiteral)                            \
@@ skipping 1063 matching lines @@
 
   LOperand* value() { return inputs_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(Branch, "branch")
   DECLARE_HYDROGEN_ACCESSOR(Branch)
 
   virtual void PrintDataTo(StringStream* stream);
 };
 
 
+class LDebugBreak: public LTemplateInstruction<0, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(DebugBreak, "break")
+};
+
+
 class LCmpMapAndBranch: public LTemplateInstruction<0, 1, 0> {
  public:
   explicit LCmpMapAndBranch(LOperand* value) {
     inputs_[0] = value;
   }
 
   LOperand* value() { return inputs_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(CmpMapAndBranch, "cmp-map-and-branch")
   DECLARE_HYDROGEN_ACCESSOR(CompareMap)
@@ skipping 1522 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_