Make HJSArrayLength more likely to have identical GVNs.

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 1911 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(CallRuntime)
 
  private:
   const Runtime::Function* c_function_;
   Handle<String> name_;
 };
 
 
 class HJSArrayLength: public HTemplateInstruction<2> {
  public:
-  HJSArrayLength(HValue* value, HValue* typecheck,
-                 HType type = HType::Tagged()) {
-    set_type(type);
-    // 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);
-    SetGVNFlag(kDependsOnArrayLengths);
-    SetGVNFlag(kDependsOnMaps);
-  }
+  static HJSArrayLength* Create(HGraph* graph,
+                                HValue* value,
+                                HValue* typecheck,
+                                HType type = HType::Tagged());
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
+  const HValue* value() const { return OperandAt(0); }
   HValue* value() { return OperandAt(0); }
   HValue* typecheck() { return OperandAt(1); }
 
   DECLARE_CONCRETE_INSTRUCTION(JSArrayLength)
 
  protected:
   virtual bool DataEquals(HValue* other_raw) { return true; }
 
  private:
   virtual bool IsDeletable() const { return true; }
+
+  HJSArrayLength(HValue* value, HValue* typecheck,
+                 HType type = HType::Tagged()) {
+    set_type(type);
+    // 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);
+    SetGVNFlag(kDependsOnArrayLengths);
+    SetGVNFlag(kDependsOnMaps);
+  }
 };
 
 
 class HFixedArrayBaseLength: public HUnaryOperation {
  public:
   explicit HFixedArrayBaseLength(HValue* value) : HUnaryOperation(value) {
     set_type(HType::Smi());
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnArrayLengths);
@@ skipping 282 matching lines @@
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
   HValue* value() { return OperandAt(0); }
   SmallMapList* map_set() { return &map_set_; }
+  bool has_dependency() { return OperandAt(1) != OperandAt(0); }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMaps)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HCheckMaps* b = HCheckMaps::cast(other);
     // Relies on the fact that map_set has been sorted before.
     if (map_set()->length() != b->map_set()->length()) return false;
     for (int i = 0; i < map_set()->length(); i++) {
       if (!map_set()->at(i).is_identical_to(b->map_set()->at(i))) return false;
@@ skipping 3116 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_