First implementation of allocation elimination in Hydrogen.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 08667c994197356d3080e5c99fd9ec7b83853be8..0bec1534e3d32bd0bb3e2081d57696682fcba974 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -87,6 +87,7 @@ class LChunkBuilder;
   V(CallNewArray)                              \
   V(CallRuntime)                               \
   V(CallStub)                                  \
+  V(CapturedObject)                            \
   V(Change)                                    \
   V(CheckFunction)                             \
   V(CheckHeapObject)                           \
@@ -3429,20 +3430,10 @@ class HInductionVariableAnnotation : public HUnaryOperation {
 };
 
 
-class HArgumentsObject: public HTemplateInstruction<0> {
+// Common base class for HArgumentsObject and HCapturedObject.
+class HDematerializedObject: public HTemplateInstruction<0> {
  public:
-  HArgumentsObject(int count, Zone* zone) : values_(count, zone) {
-    set_representation(Representation::Tagged());
-    SetFlag(kIsArguments);
-  }
-
-  const ZoneList<HValue*>* arguments_values() const { return &values_; }
-  int arguments_count() const { return values_.length(); }
-
-  void AddArgument(HValue* argument, Zone* zone) {
-    values_.Add(NULL, zone);  // Resize list.
-    SetOperandAt(values_.length() - 1, argument);
-  }
+  HDematerializedObject(int count, Zone* zone) : values_(count, zone) {}
 
   virtual int OperandCount() { return values_.length(); }
   virtual HValue* OperandAt(int index) const { return values_[index]; }
@@ -3452,17 +3443,50 @@ class HArgumentsObject: public HTemplateInstruction<0> {
     return Representation::None();
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(ArgumentsObject)
-
  protected:
   virtual void InternalSetOperandAt(int index, HValue* value) {
     values_[index] = value;
   }
 
+  ZoneList<HValue*> values_;

[titzer, 2013/08/01 17:11:50]

How is this values_ array indexed? Does it store only in-object properties and
is indexed by field index?

[Michael Starzinger, 2013/08/05 15:13:00]

Correct. I added a comment to both HArgumentsObject and HCapturedObject below
that covers this.

+
  private:
   virtual bool IsDeletable() const { return true; }
+};
 
-  ZoneList<HValue*> values_;
+
+class HArgumentsObject: public HDematerializedObject {
+ public:
+  HArgumentsObject(int count, Zone* zone)
+      : HDematerializedObject(count, zone) {
+    set_representation(Representation::Tagged());
+    SetFlag(kIsArguments);
+  }
+
+  const ZoneList<HValue*>* arguments_values() const { return &values_; }
+  int arguments_count() const { return values_.length(); }
+
+  void AddArgument(HValue* argument, Zone* zone) {
+    values_.Add(NULL, zone);  // Resize list.
+    SetOperandAt(values_.length() - 1, argument);
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(ArgumentsObject)
+};
+
+
+class HCapturedObject: public HDematerializedObject {
+ public:
+  HCapturedObject(int length, Zone* zone)
+      : HDematerializedObject(length, zone) {
+    set_representation(Representation::Tagged());
+    values_.AddBlock(NULL, length, zone);  // Resize list.
+  }
+
+  const ZoneList<HValue*>* values() const { return &values_; }
+  int length() const { return values_.length(); }
+
+  DECLARE_CONCRETE_INSTRUCTION(CapturedObject)
 };
 
 
@@ -6286,7 +6310,6 @@ class HStoreKeyed
     }
   }
 
-  virtual bool HasEscapingOperandAt(int index) { return index != 0; }
   virtual Representation RequiredInputRepresentation(int index) {
     // kind_fast:       tagged[int32] = tagged
     // kind_double:     tagged[int32] = double