First simplistic implementation of escape analysis.

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 1040 matching lines @@
   bool HasRange() const { return range_ != NULL; }
   bool CanBeNegative() const { return !HasRange() || range()->CanBeNegative(); }
   bool CanBeZero() const { return !HasRange() || range()->CanBeZero(); }
   bool RangeCanInclude(int value) const {
     return !HasRange() || range()->Includes(value);
   }
   void AddNewRange(Range* r, Zone* zone);
   void RemoveLastAddedRange();
   void ComputeInitialRange(Zone* zone);
 
+  // Escape analysis helpers.
+  virtual bool HasEscapingOperandAt(int index) { return true; }
+
   // Representation helpers.
   virtual Representation observed_input_representation(int index) {
     return Representation::None();
   }
   virtual Representation RequiredInputRepresentation(int index) = 0;
   virtual void InferRepresentation(HInferRepresentation* h_infer);
 
   // This gives the instruction an opportunity to replace itself with an
   // instruction that does the same in some better way.  To replace an
   // instruction with a new one, first add the new instruction to the graph,
@@ skipping 351 matching lines @@
   explicit HDummyUse(HValue* value) {
     SetOperandAt(0, value);
     // Pretend to be a Smi so that the HChange instructions inserted
     // before any use generate as little code as possible.
     set_representation(Representation::Tagged());
     set_type(HType::Smi());
   }
 
   HValue* value() { return OperandAt(0); }
 
+  virtual bool HasEscapingOperandAt(int index) { return false; }
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(DummyUse);
 };
 
 
@@ skipping 439 matching lines @@
   }
   int ToOperandIndex(int environment_index) {
     for (int i = 0; i < assigned_indexes_.length(); ++i) {
       if (assigned_indexes_[i] == environment_index) return i;
     }
     return -1;
   }
   virtual int OperandCount() { return values_.length(); }
   virtual HValue* OperandAt(int index) const { return values_[index]; }
 
+  virtual bool HasEscapingOperandAt(int index) { return false; }
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   void MergeWith(ZoneList<HSimulate*>* list);
   bool is_candidate_for_removal() { return removable_ == REMOVABLE_SIMULATE; }
 
   DECLARE_CONCRETE_INSTRUCTION(Simulate)
 
 #ifdef DEBUG
@@ skipping 889 matching lines @@
       Map* transitioned_map =
           map->LookupElementsTransitionMap(kind);
       if (transitioned_map) {
         check_map->map_set_.Add(Handle<Map>(transitioned_map), zone);
       }
     };
     check_map->map_set_.Sort();
     return check_map;
   }
 
+  virtual bool HasEscapingOperandAt(int index) { return false; }
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
   virtual void SetSideEffectDominator(GVNFlag side_effect, HValue* dominator);
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
   HValue* value() { return OperandAt(0); }
   SmallMapList* map_set() { return &map_set_; }
 
@@ skipping 411 matching lines @@
   int arguments_count() const { return values_.length(); }
 
   void AddArgument(HValue* argument, Zone* zone) {
     values_.Add(NULL, zone);  // Resize list.
     SetOperandAt(values_.length() - 1, argument);
   }
 
   virtual int OperandCount() { return values_.length(); }
   virtual HValue* OperandAt(int index) const { return values_[index]; }
 
+  virtual bool HasEscapingOperandAt(int index) { return false; }
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(ArgumentsObject)
 
  protected:
   virtual void InternalSetOperandAt(int index, HValue* value) {
     values_[index] = value;
   }
@@ skipping 2183 matching lines @@
   HValue* object() { return OperandAt(0); }
   HValue* typecheck() {
     ASSERT(HasTypeCheck());
     return OperandAt(1);
   }
 
   bool HasTypeCheck() const { return OperandAt(0) != OperandAt(1); }
   HObjectAccess access() const { return access_; }
   Representation field_representation() const { return representation_; }
 
+  virtual bool HasEscapingOperandAt(int index) { return false; }
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedField)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HLoadNamedField* b = HLoadNamedField::cast(other);
@@ skipping 312 matching lines @@
         transition_(),
         transition_unique_id_(),
         new_space_dominator_(NULL) {
     SetOperandAt(0, obj);
     SetOperandAt(1, val);
     access.SetGVNFlags(this, true);
   }
 
   DECLARE_CONCRETE_INSTRUCTION(StoreNamedField)
 
+  virtual bool HasEscapingOperandAt(int index) { return index == 1; }
   virtual Representation RequiredInputRepresentation(int index) {
     if (FLAG_track_double_fields &&
         index == 1 && field_representation_.IsDouble()) {
       return field_representation_;
     } else if (FLAG_track_fields &&
                index == 1 && field_representation_.IsSmi()) {
       return field_representation_;
     }
     return Representation::Tagged();
   }
@@ skipping 82 matching lines @@
   Handle<String> name_;
   StrictModeFlag strict_mode_flag_;
 };
 
 
 class HStoreKeyed
     : public HTemplateInstruction<3>, public ArrayInstructionInterface {
  public:
   HStoreKeyed(HValue* obj, HValue* key, HValue* val,
               ElementsKind elements_kind)
       : elements_kind_(elements_kind),

[titzer, 2013/06/28 12:40:55]

Perhaps:

HasEscapingOperandAt(int index) { return index == 2 }

[Michael Starzinger, 2013/06/28 13:37:27]

Done. As discussed offline: This will only work of the key is a known HConstant
and not a computed value. Also the key itself escapes, so it should rather be
"return index != 0". This will also require adaptation of HLoadElements
accordingly.

       index_offset_(0),
       is_dehoisted_(false),
       new_space_dominator_(NULL) {
     SetOperandAt(0, obj);
     SetOperandAt(1, key);
     SetOperandAt(2, val);
 
     if (IsFastObjectElementsKind(elements_kind)) {
       SetFlag(kTrackSideEffectDominators);
       SetGVNFlag(kDependsOnNewSpacePromotion);
@@ skipping 102 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(StoreKeyed)
 
  private:
   ElementsKind elements_kind_;
   uint32_t index_offset_;
   bool is_dehoisted_;
   HValue* new_space_dominator_;
 };
 
 
 class HStoreKeyedGeneric: public HTemplateInstruction<4> {

[titzer, 2013/06/28 12:40:55]

Also here...

[Michael Starzinger, 2013/06/28 13:37:27]

For a generic store I think this won't work as the generic store will call into
ICs and/or the runtime. Also generic indicates that some weird corner-case like
accessors or prototype lookups are involved. And this will be hard without a
materialized receiver object.

  public:
   HStoreKeyedGeneric(HValue* context,
                      HValue* object,
                      HValue* key,
                      HValue* value,
                      StrictModeFlag strict_mode_flag)
       : strict_mode_flag_(strict_mode_flag) {
     SetOperandAt(0, object);
     SetOperandAt(1, key);
     SetOperandAt(2, value);
@@ skipping 639 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_