Add a HBreak instruction for debugging

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 138587c43f72b45b9be5193682174eb37b6896be..820bfdea4c2241866245ec6a0721c25db874773a 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -76,6 +76,7 @@ class LChunkBuilder;
   V(BoundsCheck)                               \
   V(BoundsCheckBaseIndexInformation)           \
   V(Branch)                                    \
+  V(Break)                                     \
   V(CallConstantFunction)                      \
   V(CallFunction)                              \
   V(CallGlobal)                                \
@@ -1463,6 +1464,16 @@ class HSoftDeoptimize: public HTemplateInstruction<0> {
 };
 
 
+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)