Add a HBreak instruction for debugging

src/hydrogen-instructions.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 58 matching lines @@
   V(ApplyArguments)                            \
   V(ArgumentsElements)                         \
   V(ArgumentsLength)                           \
   V(ArgumentsObject)                           \
   V(Bitwise)                                   \
   V(BitNot)                                    \
   V(BlockEntry)                                \
   V(BoundsCheck)                               \
   V(BoundsCheckBaseIndexInformation)           \
   V(Branch)                                    \
+  V(Break)                                     \
   V(CallConstantFunction)                      \
   V(CallFunction)                              \
   V(CallGlobal)                                \
   V(CallKeyed)                                 \
   V(CallKnownGlobal)                           \
   V(CallNamed)                                 \
   V(CallNew)                                   \
   V(CallNewArray)                              \
   V(CallRuntime)                               \
   V(CallStub)                                  \
@@ skipping 1367 matching lines @@
 class HSoftDeoptimize: public HTemplateInstruction<0> {
  public:
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(SoftDeoptimize)
 };
 
 
+class HBreak: public HTemplateInstruction<0> {

[Jakob Kummerow, 2013/05/15 11:23:36]

I'd prefer to call this instruction HDebugBreak (and the lithium equivalent
LDebugBreak) to avoid confusion, since it doesn't have anything to do with the
JS "break" statement, whereas we already have an OS::DebugBreak() that serves
the same purpose in C++ code.

Also, a short comment here would be nice:
// Inserts an int3/stop break instruction for debugging purposes.

+ public:
+  virtual Representation RequiredInputRepresentation(int index) {
+    return Representation::None();
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(Break)
+};
+
+
 class HDeoptimize: public HControlInstruction {
  public:
   HDeoptimize(int environment_length, Zone* zone)
       : values_(environment_length, zone) { }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   virtual int OperandCount() { return values_.length(); }
@@ skipping 4973 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_