Improve and simplify removal of unreachable code

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 3372 matching lines @@
       ASSERT(!handle_.is_null());
       unique_id_ = UniqueValueId(handle_);
     }
   }
 
   bool UniqueValueIdsMatch(UniqueValueId other) {
     return !has_double_value_ && !has_external_reference_value_ &&
         unique_id_ == other;
   }
 
+  bool SameConstantObject(HConstant* other) {

[Michael Starzinger, 2013/08/16 15:02:20]

nit: Let's rename this to just "SameConstant", it doesn't look specific to
objects.

[Jakob Kummerow, 2013/08/20 08:46:56]

This seems to cover a subset of the functionality of DataEquals() below. Maybe
re-use that instead? If you actually need the specialized behavior then that's
fine of course.

[danno, 2013/10/01 10:43:18]

Actually, I use DataEquals now. Makes it even simpler.

+    if (HasSmiValue() && other->HasSmiValue()) {

[Michael Starzinger, 2013/08/16 15:02:20]

Shouldn't this be HasInteger32Value in these checks? Also what about
HasDoubleValue?

[danno, 2013/10/01 10:43:18]

See above.

+      return int32_value_ == other->int32_value_;
+    }
+    return UniqueValueIdsMatch(other->unique_id_);
+  }
+
 #ifdef DEBUG
   virtual void Verify() { }
 #endif
 
   DECLARE_CONCRETE_INSTRUCTION(Constant)
 
  protected:
   virtual Range* InferRange(Zone* zone);
 
   virtual bool DataEquals(HValue* other) {
@@ skipping 601 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(CompareHoleAndBranch)
 };
 
 
 class HCompareObjectEqAndBranch: public HTemplateControlInstruction<2, 2> {
  public:
   // TODO(danno): make this private when the IfBuilder properly constructs
   // control flow instructions.
   HCompareObjectEqAndBranch(HValue* left,
                             HValue* right) {
+    ASSERT(!left->IsConstant() ||
+           (!HConstant::cast(left)->HasInteger32Value() ||
+            HConstant::cast(left)->HasSmiValue()));
+    ASSERT(!right->IsConstant() ||
+           (!HConstant::cast(right)->HasInteger32Value() ||
+            HConstant::cast(right)->HasSmiValue()));
     SetOperandAt(0, left);
     SetOperandAt(1, right);
   }
 
   DECLARE_INSTRUCTION_FACTORY_P2(HCompareObjectEqAndBranch, HValue*, HValue*);
 
   HValue* left() { return OperandAt(0); }
   HValue* right() { return OperandAt(1); }
 
   virtual void PrintDataTo(StringStream* stream);
@@ skipping 2783 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_