Add fake data dependencies (instead of disabling GVN) to fix code motion

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 1643 matching lines @@
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CallRuntime)
 
  private:
   const Runtime::Function* c_function_;
   Handle<String> name_;
 };
 
 
-class HJSArrayLength: public HUnaryOperation {
+class HJSArrayLength: public HTemplateInstruction<2> {
  public:
-  explicit HJSArrayLength(HValue* value) : HUnaryOperation(value) {
+  HJSArrayLength(HValue* value, HValue* typecheck) {
     // The length of an array is stored as a tagged value in the array
     // object. It is guaranteed to be 32 bit integer, but it can be
     // represented as either a smi or heap number.
+    SetOperandAt(0, value);
+    SetOperandAt(1, typecheck);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnArrayLengths);
     SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
 
+  HValue* value() { return OperandAt(0); }
+
   DECLARE_CONCRETE_INSTRUCTION(JSArrayLength)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
 class HFixedArrayLength: public HUnaryOperation {
  public:
   explicit HFixedArrayLength(HValue* value) : HUnaryOperation(value) {
@@ skipping 210 matching lines @@
     SetFlag(kUseGVN);
     SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
-
   Handle<Map> map() const { return map_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMap)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HCheckMap* b = HCheckMap::cast(other);
     return map_.is_identical_to(b->map());
   }
 
@@ skipping 47 matching lines @@
     return new HCheckInstanceType(value, IS_STRING);
   }
   static HCheckInstanceType* NewIsSymbol(HValue* value) {
     return new HCheckInstanceType(value, IS_SYMBOL);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
-
   virtual HValue* Canonicalize();
 
   bool is_interval_check() const { return check_ <= LAST_INTERVAL_CHECK; }
   void GetCheckInterval(InstanceType* first, InstanceType* last);
   void GetCheckMaskAndTag(uint8_t* mask, uint8_t* tag);
 
   DECLARE_CONCRETE_INSTRUCTION(CheckInstanceType)
 
  protected:
   // TODO(ager): It could be nice to allow the ommision of instance
@@ skipping 454 matching lines @@
     SetOperandAt(0, index);
     SetOperandAt(1, length);
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Integer32();
   }
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
-
   HValue* index() { return OperandAt(0); }
   HValue* length() { return OperandAt(1); }
 
   DECLARE_CONCRETE_INSTRUCTION(BoundsCheck)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
@@ skipping 1652 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_