Simple elimination of redundant array-hole checks.

src/hydrogen-instructions.h

 // Copyright 2011 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 3237 matching lines @@
   HValue* key() { return OperandAt(1); }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     // The key is supposed to be Integer32.
     return (index == 1) ? Representation::Integer32()
         : Representation::Tagged();
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
+  bool check_hole_value() const;

[Kevin Millikin (Chromium), 2011/05/09 14:59:54]

This should probably have a CamelCase name.  I'd also like it to sound more
obviously like a predicate.  ShouldCheckHoleValue?  MustCheckHoleValue?

+
   DECLARE_CONCRETE_INSTRUCTION(LoadKeyedFastElement)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
 class HLoadKeyedSpecializedArrayElement: public HBinaryOperation {
  public:
   HLoadKeyedSpecializedArrayElement(HValue* external_elements,
@@ skipping 560 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_