Supported folding of constant size allocation followed by dynamic size allocation.

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 1220 matching lines @@
   virtual int operand_position(int index) const V8_OVERRIDE {
     const int pos = position_.operand_position(index);
     return (pos != RelocInfo::kNoPosition) ? pos : position();
   }
   void set_operand_position(Zone* zone, int index, int pos) {
     ASSERT(0 <= index && index < OperandCount());
     position_.ensure_storage_for_operand_positions(zone, OperandCount());
     position_.set_operand_position(index, pos);
   }
 
+  bool Dominates(HInstruction* other);
+
   bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
   virtual void Verify() V8_OVERRIDE;
 #endif
 
   virtual bool IsCall() { return false; }
 
@@ skipping 6199 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_