Implement local check elimination on basic blocks.

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 3464 matching lines @@
     return !has_double_value_ && !has_external_reference_value_ &&
         unique_id_ == other;
   }
 
   Unique<Object> GetUnique() const {
     // TODO(titzer): store a Unique<HeapObject> inside the HConstant.
     Address raw_address = reinterpret_cast<Address>(unique_id_.Hashcode());
     return Unique<Object>(raw_address, handle_);
   }
 
+  template<typename T>
+  Unique<T> GetCastedUnique() const {
+    // TODO(titzer): store a Unique<HeapObject> inside the HConstant.
+    Address raw_address = reinterpret_cast<Address>(unique_id_.Hashcode());
+    return Unique<T>(raw_address, Handle<T>::cast(handle_));
+  }
+
 #ifdef DEBUG
   virtual void Verify() V8_OVERRIDE { }
 #endif
 
   DECLARE_CONCRETE_INSTRUCTION(Constant)
 
  protected:
   virtual Range* InferRange(Zone* zone) V8_OVERRIDE;
 
   virtual bool DataEquals(HValue* other) V8_OVERRIDE {
@@ skipping 3569 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_