Introduce HObjectAccess, which is used by LoadNamedField and StoreNamedField to denote what parts

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index decc62705b28808de6ca0f78b66fc503421dbc5e..2cb19d8c2dea27b5467b0d8a038ba8270959432c 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -5186,46 +5186,94 @@ class HStoreContextSlot: public HTemplateInstruction<2> {
 };
 
 
+// Represents an access to a portion of an object, such as the map pointer,
+// array elements pointer, etc, but not accesses to array elements themselves.
+class HObjectAccess {
+ public:
+  inline bool IsInobject() const {
+    return portion_ != kBackingStore;
+  }
+
+  inline int offset() const {
+    return offset_;
+  }
+
+  inline Handle<String> name() const {
+    return name_;
+  }
+
+  static HObjectAccess ForElementsPointer() {
+    return HObjectAccess(kElementsPointer, JSObject::kElementsOffset);
+  }
+
+  static HObjectAccess ForArrayLength() {
+    return HObjectAccess(kArrayLengths, JSArray::kLengthOffset);
+  }
+
+  static HObjectAccess ForFixedArrayLength() {
+    return HObjectAccess(kInobject, FixedArray::kLengthOffset);
+  }
+
+  static HObjectAccess ForMap() {
+    return HObjectAccess(kMaps, JSObject::kMapOffset);
+  }
+
+  // Create an access to a property in an object or backing store
+  static HObjectAccess For(bool is_inobject, int offset);

[danno, 2013/05/08 12:05:35]

This should be "ForJSObjectField". It only works for JSObjects (the concept of
"is_inobject" only is valid for JSObjects and their sub-classes.

[titzer, 2013/05/08 15:15:45]

The only remaining use of this is for accessing a heap object allocation site
(not a JSObject), and the code stubs, which now check whether they are inobject,
and if so, call the ForJSObjectOffset.

+
+  // Create an access to an in-object property in an object
+  static HObjectAccess ForOffset(int offset,

[danno, 2013/05/08 12:05:35]

This guy is *super* dangerous. Either it should only work on JSObjects, or you
*must* pass in a map. It's important to be clear that object's are not always
JSObjects, there are all sorts of HeapObject that we store to. ForOffset can't
be the swiss-army knife you'd like it to be without knowing exactly what kind of
object you're operating on.

[titzer, 2013/05/08 15:15:45]

I've split it apart into ForJSObjectOffset, ForJSArrayOffset, and
ForFixedArrayOffset.

+      Handle<String> name = Handle<String>::null());
+
+  // Create an access to a resolved field (in-object or backing store)
+  static HObjectAccess ForField(Handle<Map> map,
+      LookupResult *lookup, Handle<String> name = Handle<String>::null());
+
+  void PrintTo(StringStream* stream);
+
+ protected:
+  void SetGVNFlags(HValue *instr, bool is_store);
+
+ private:
+  // internal use only; different parts of an object or array
+  enum Portion {
+    kMaps,             // map of an object
+    kArrayLengths,     // the length of an array
+    kElementsPointer,  // elements pointer
+    kBackingStore,     // some field in the backing store
+    kInobject          // some other in-object field
+  };
+
+  HObjectAccess(Portion portion, int offset,
+      Handle<String> name = Handle<String>::null())
+      : portion_(portion), offset_(offset), name_(name) {
+    ASSERT(offset_ == offset);    // offset must fit
+    ASSERT(portion_ == portion);  // portion must fit
+  }
+
+  unsigned portion_ : 3;
+  unsigned offset_  : 29;
+  Handle<String> name_;
+
+  friend class HLoadNamedField;
+  friend class HStoreNamedField;
+};
+
+
 class HLoadNamedField: public HTemplateInstruction<2> {
  public:
-  HLoadNamedField(HValue* object, bool is_in_object,
-                  Representation field_representation,
-                  int offset, HValue* typecheck = NULL)
-      : is_in_object_(is_in_object),
-        field_representation_(field_representation),
-        offset_(offset) {
+  HLoadNamedField(HValue* object,
+                  HObjectAccess access,
+                  HValue* typecheck = NULL,
+                  Representation representation = Representation::Tagged())
+      : access_(access),
+        field_representation_(representation) {
     ASSERT(object != NULL);
     SetOperandAt(0, object);
     SetOperandAt(1, typecheck != NULL ? typecheck : object);
 
-    if (FLAG_track_fields && field_representation.IsSmi()) {
-      set_type(HType::Smi());
-      set_representation(Representation::Tagged());
-    } else if (FLAG_track_double_fields && field_representation.IsDouble()) {
-      set_representation(field_representation);
-    } else {
-      set_representation(Representation::Tagged());
-    }
-    SetFlag(kUseGVN);
-    SetGVNFlag(kDependsOnMaps);
-    if (is_in_object) {
-      SetGVNFlag(kDependsOnInobjectFields);
-    } else {
-      SetGVNFlag(kDependsOnBackingStoreFields);
-    }
-  }
-
-  static HLoadNamedField* NewArrayLength(Zone* zone, HValue* object,
-                                         HValue* typecheck,
-                                         HType type = HType::Tagged()) {
-    Representation representation =
-        type.IsSmi() ? Representation::Smi() : Representation::Tagged();
-    HLoadNamedField* result = new(zone) HLoadNamedField(
-        object, true, representation, JSArray::kLengthOffset, typecheck);
-    result->set_type(type);
-    result->SetGVNFlag(kDependsOnArrayLengths);
-    result->ClearGVNFlag(kDependsOnInobjectFields);
-    return result;
+    set_representation(Representation::Tagged());
+    access.SetGVNFlags(this, false);
   }
 
   HValue* object() { return OperandAt(0); }
@@ -5235,9 +5283,9 @@ class HLoadNamedField: public HTemplateInstruction<2> {
   }
 
   bool HasTypeCheck() const { return OperandAt(0) != OperandAt(1); }
-  bool is_in_object() const { return is_in_object_; }
+  bool is_in_object() const { return access_.IsInobject(); }
   Representation field_representation() const { return representation_; }
-  int offset() const { return offset_; }
+  int offset() const { return access_.offset(); }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ -5249,15 +5297,14 @@ class HLoadNamedField: public HTemplateInstruction<2> {
  protected:
   virtual bool DataEquals(HValue* other) {
     HLoadNamedField* b = HLoadNamedField::cast(other);
-    return is_in_object_ == b->is_in_object_ && offset_ == b->offset_;
+    return is_in_object() == b->is_in_object() && offset() == b->offset();
   }
 
  private:
   virtual bool IsDeletable() const { return true; }
 
-  bool is_in_object_;
+  HObjectAccess access_;
   Representation field_representation_;
-  int offset_;
 };
 
 
@@ -5551,26 +5598,16 @@ class HLoadKeyedGeneric: public HTemplateInstruction<3> {
 class HStoreNamedField: public HTemplateInstruction<2> {
  public:
   HStoreNamedField(HValue* obj,
-                   Handle<String> name,
+                   HObjectAccess access,
                    HValue* val,
-                   bool in_object,
-                   Representation field_representation,
-                   int offset)
-      : name_(name),
-        is_in_object_(in_object),
-        field_representation_(field_representation),
-        offset_(offset),
+                   Representation representation = Representation::Tagged())
+      : access_(access),
+        field_representation_(representation),
         transition_unique_id_(),
         new_space_dominator_(NULL) {
     SetOperandAt(0, obj);
     SetOperandAt(1, val);
-    SetFlag(kTrackSideEffectDominators);
-    SetGVNFlag(kDependsOnNewSpacePromotion);
-    if (is_in_object_) {
-      SetGVNFlag(kChangesInobjectFields);
-    } else {
-      SetGVNFlag(kChangesBackingStoreFields);
-    }
+    access.SetGVNFlags(this, true);
   }
 
   DECLARE_CONCRETE_INSTRUCTION(StoreNamedField)
@@ -5590,9 +5627,9 @@ class HStoreNamedField: public HTemplateInstruction<2> {
   HValue* object() { return OperandAt(0); }
   HValue* value() { return OperandAt(1); }
 
-  Handle<String> name() const { return name_; }
-  bool is_in_object() const { return is_in_object_; }
-  int offset() const { return offset_; }
+  Handle<String> name() const { return access_.name(); }
+  bool is_in_object() const { return access_.IsInobject(); }
+  int offset() const { return access_.offset(); }
   Handle<Map> transition() const { return transition_; }
   UniqueValueId transition_unique_id() const { return transition_unique_id_; }
   void set_transition(Handle<Map> map) { transition_ = map; }
@@ -5617,10 +5654,8 @@ class HStoreNamedField: public HTemplateInstruction<2> {
   }
 
  private:
-  Handle<String> name_;
-  bool is_in_object_;
+  HObjectAccess access_;
   Representation field_representation_;
-  int offset_;
   Handle<Map> transition_;
   UniqueValueId transition_unique_id_;
   HValue* new_space_dominator_;