Implement tracking and optimizations of packed arrays

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 2065 matching lines @@
     for (int i = 0; i < maps->length(); i++) {
       map_set()->Add(maps->at(i));
     }
     map_set()->Sort();
   }
 
   static HCheckMaps* NewWithTransitions(HValue* object, Handle<Map> map) {
     HCheckMaps* check_map = new HCheckMaps(object, map);
     SmallMapList* map_set = check_map->map_set();
 
-    // If the map to check has the untransitioned elements, it can be hoisted
-    // above TransitionElements instructions.
-    if (map->has_fast_smi_only_elements()) {
-      check_map->ClearGVNFlag(kDependsOnElementsKind);
-    }
+    // Since transitioned elements maps of the initial map don't fail the map
+    // check, the CheckMaps instruction doesn't need to depend on ElementsKinds.
+    check_map->ClearGVNFlag(kDependsOnElementsKind);
 
-    Map* transitioned_fast_element_map =
-        map->LookupElementsTransitionMap(FAST_ELEMENTS, NULL);
-    ASSERT(transitioned_fast_element_map == NULL ||
-           map->elements_kind() != FAST_ELEMENTS);
-    if (transitioned_fast_element_map != NULL) {
-      map_set->Add(Handle<Map>(transitioned_fast_element_map));
-    }
-    Map* transitioned_double_map =
-        map->LookupElementsTransitionMap(FAST_DOUBLE_ELEMENTS, NULL);
-    ASSERT(transitioned_double_map == NULL ||
-           map->elements_kind() == FAST_SMI_ONLY_ELEMENTS);
-    if (transitioned_double_map != NULL) {
-      map_set->Add(Handle<Map>(transitioned_double_map));
-    }
+    ElementsKind kind = map->elements_kind();
+    bool packed = IsFastPackedElementsKind(kind);
+    while (CanTransitionToMoreGeneralFastElementsKind(kind, packed)) {
+      kind = GetNextMoreGeneralFastElementsKind(kind, packed);
+      Map* transitioned_map =
+          map->LookupElementsTransitionMap(kind, NULL);
+      if (transitioned_map) {
+        map_set->Add(Handle<Map>(transitioned_map));
+      }
+    };
     map_set->Sort();
-
     return check_map;
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
   HValue* value() { return OperandAt(0); }
@@ skipping 1822 matching lines @@
     return Representation::Tagged();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(LoadFunctionPrototype)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
+enum HoleCheckMode { PERFORM_HOLE_CHECK, OMIT_HOLE_CHECK };
+
+
 class HLoadKeyedFastElement: public HTemplateInstruction<2> {
  public:
-  enum HoleCheckMode { PERFORM_HOLE_CHECK, OMIT_HOLE_CHECK };
-
   HLoadKeyedFastElement(HValue* obj,
                         HValue* key,
                         HoleCheckMode hole_check_mode = PERFORM_HOLE_CHECK)
       : hole_check_mode_(hole_check_mode) {
     SetOperandAt(0, obj);
     SetOperandAt(1, key);
     set_representation(Representation::Tagged());
     SetGVNFlag(kDependsOnArrayElements);
     SetFlag(kUseGVN);
   }
@@ skipping 21 matching lines @@
     return hole_check_mode_ == other_load->hole_check_mode_;
   }
 
  private:
   HoleCheckMode hole_check_mode_;
 };
 
 
 class HLoadKeyedFastDoubleElement: public HTemplateInstruction<2> {
  public:
-  HLoadKeyedFastDoubleElement(HValue* elements, HValue* key) {
+  HLoadKeyedFastDoubleElement(
+      HValue* elements,
+      HValue* key,
+      HoleCheckMode hole_check_mode = PERFORM_HOLE_CHECK)
+      : hole_check_mode_(hole_check_mode) {
     SetOperandAt(0, elements);
     SetOperandAt(1, key);
     set_representation(Representation::Double());
     SetGVNFlag(kDependsOnDoubleArrayElements);
     SetFlag(kUseGVN);
   }
 
   HValue* elements() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
 
   virtual Representation RequiredInputRepresentation(int index) {
     // The key is supposed to be Integer32.
     return index == 0
       ? Representation::Tagged()
       : Representation::Integer32();
   }
 
+  bool RequiresHoleCheck() {
+    return hole_check_mode_ == PERFORM_HOLE_CHECK;
+  }
+
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(LoadKeyedFastDoubleElement)
 
  protected:
-  virtual bool DataEquals(HValue* other) { return true; }
+  virtual bool DataEquals(HValue* other) {
+    if (!other->IsLoadKeyedFastDoubleElement()) return false;
+    HLoadKeyedFastDoubleElement* other_load =
+        HLoadKeyedFastDoubleElement::cast(other);
+    return hole_check_mode_ == other_load->hole_check_mode_;
+  }
+
+ private:
+  HoleCheckMode hole_check_mode_;
 };
 
 
 class HLoadKeyedSpecializedArrayElement: public HTemplateInstruction<2> {
  public:
   HLoadKeyedSpecializedArrayElement(HValue* external_elements,
                                     HValue* key,
                                     ElementsKind elements_kind)
       :  elements_kind_(elements_kind) {
     SetOperandAt(0, external_elements);
@@ skipping 174 matching lines @@
     // The key is supposed to be Integer32.
     return index == 1
         ? Representation::Integer32()
         : Representation::Tagged();
   }
 
   HValue* object() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
   HValue* value() { return OperandAt(2); }
   bool value_is_smi() {
-    return elements_kind_ == FAST_SMI_ONLY_ELEMENTS;
+    return IsFastSmiElementsKind(elements_kind_);
   }
 
   bool NeedsWriteBarrier() {
     if (value_is_smi()) {
       return false;
     } else {
       return StoringValueNeedsWriteBarrier(value());
     }
   }
 
@@ skipping 121 matching lines @@
 
 class HTransitionElementsKind: public HTemplateInstruction<1> {
  public:
   HTransitionElementsKind(HValue* object,
                           Handle<Map> original_map,
                           Handle<Map> transitioned_map)
       : original_map_(original_map),
         transitioned_map_(transitioned_map) {
     SetOperandAt(0, object);
     SetFlag(kUseGVN);
+    // Don't set GVN DependOn flags here. That would defeat GVN's detection of
+    // congruent HTransitionElementsKind instructions. Instruction hoisting
+    // handles HTransitionElementsKind instruction specially, explicitly adding
+    // DependsOn flags during its dependency calculations.
     SetGVNFlag(kChangesElementsKind);
-    SetGVNFlag(kChangesElementsPointer);
-    SetGVNFlag(kChangesNewSpacePromotion);
+    if (original_map->has_fast_double_elements()) {

[Jakob Kummerow, 2012/05/13 21:55:27]

The bodies of these two if-blocks are the same; I'd suggest to merge them. IIUC,
the most appropriate condition is "if (original_map->has_fast_double_elements()
^ transitioned_map->has_fast_double_elements())", as a PACKED_DOUBLE ->
HOLEY_DOUBLE transition doesn't need to set those flags.

[danno, 2012/05/22 11:05:21]

Done.

+      SetGVNFlag(kChangesElementsPointer);
+      SetGVNFlag(kChangesNewSpacePromotion);
+    }
+    if (transitioned_map->has_fast_double_elements()) {
+      SetGVNFlag(kChangesElementsPointer);
+      SetGVNFlag(kChangesNewSpacePromotion);
+    }
     set_representation(Representation::Tagged());
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
   HValue* object() { return OperandAt(0); }
   Handle<Map> original_map() { return original_map_; }
   Handle<Map> transitioned_map() { return transitioned_map_; }
@@ skipping 217 matching lines @@
       : HMaterializedLiteral<1>(literal_index, depth),
         length_(length),
         boilerplate_object_(boilerplate_object) {
     SetOperandAt(0, context);
     SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   HValue* context() { return OperandAt(0); }
   ElementsKind boilerplate_elements_kind() const {
     if (!boilerplate_object_->IsJSObject()) {
-      return FAST_ELEMENTS;
+      return TERMINAL_FAST_ELEMENTS_KIND;
     }
     return Handle<JSObject>::cast(boilerplate_object_)->GetElementsKind();
   }
   Handle<HeapObject> boilerplate_object() const { return boilerplate_object_; }
   int length() const { return length_; }
 
   bool IsCopyOnWrite() const;
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ skipping 353 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(LoadFieldByIndex);
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_