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

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 70e2395574747085a8a554cc0a84d00eecd81390..07f521f1b7b82ca303064ba132868d0ea5f8c729 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -3650,7 +3650,120 @@ void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
-

[danno, 2013/05/06 15:53:06]

Stray whitespace removal, please add back. 

[titzer, 2013/05/07 17:51:03]

Done.

 #endif
 
+
+// global accesses that can be shared across instructions
+HObjectAccess elements_pointer_access_(
+    HObjectAccess::kElementsPointer, JSObject::kElementsOffset);
+HObjectAccess array_length_access_(
+    HObjectAccess::kArrayLengths, JSArray::kLengthOffset);
+HObjectAccess fixed_array_length_access_(
+    HObjectAccess::kInobject, FixedArray::kLengthOffset);
+HObjectAccess map_access_(
+    HObjectAccess::kMaps, JSObject::kMapOffset);
+
+
+HObjectAccess* HObjectAccess::ForElementsPointer() {
+  return &elements_pointer_access_;
+}
+
+
+HObjectAccess* HObjectAccess::ForArrayLength() {
+  return &array_length_access_;
+}
+
+
+HObjectAccess* HObjectAccess::ForFixedArrayLength() {
+  return &fixed_array_length_access_;
+}
+
+
+HObjectAccess* HObjectAccess::ForMap() {
+  return &map_access_;
+}
+

[danno, 2013/05/06 15:53:06]

nit: two newlines

[titzer, 2013/05/07 17:51:03]

Done.

+HObjectAccess* HObjectAccess::ForInobjectOffset(Zone *zone, int offset,
+    Handle<String> name) {
+
+  ASSERT(offset >= 0);
+  Portion portion = kInobject;
+
+  if (offset == JSObject::kElementsOffset) {
+    portion = kElementsPointer;
+  } else if (offset == JSArray::kLengthOffset) {
+    portion = kArrayLengths;  // XXX: only true for arrays?
+  } else if (offset == JSObject::kMapOffset) {
+    portion = kMaps;
+  }
+  return new(zone) HObjectAccess(portion, offset, name);
+}
+

[danno, 2013/05/06 15:53:06]

nit: two lines

[titzer, 2013/05/07 17:51:03]

Done.

+HObjectAccess* HObjectAccess::ForOffset(Zone *zone, int offset,
+    Handle<String> name) {
+  return new(zone) HObjectAccess(kInobject, offset, name);
+}
+

[danno, 2013/05/06 15:53:06]

nit: two lines

[titzer, 2013/05/07 17:51:03]

Done.

+HObjectAccess* HObjectAccess::ForField(Zone *zone, Handle<Map> map,
+    LookupResult *lookup, Handle<String> name) {
+  ASSERT(lookup->IsField() || lookup->IsTransitionToField(*map));
+  int index;
+  if (lookup->IsField()) {
+    index = lookup->GetLocalFieldIndexFromMap(*map);
+  } else {
+    Map* transition = lookup->GetTransitionMapFromMap(*map);
+    int descriptor = transition->LastAdded();
+    index = transition->instance_descriptors()->GetFieldIndex(descriptor) -
+        map->inobject_properties();
+  }
+  if (index < 0) {
+    // Negative property indices are in-object properties, indexed
+    // from the end of the fixed part of the object.
+    int offset = (index * kPointerSize) + map->instance_size();
+    return new(zone) HObjectAccess(HObjectAccess::kInobject, offset);
+  } else {
+    // Non-negative property indices are in the properties array.
+    int offset = (index * kPointerSize) + FixedArray::kHeaderSize;
+    return new(zone)
+        HObjectAccess(HObjectAccess::kBackingStore, offset, name);
+  }
+}
+
+
+void HObjectAccess::SetGVNFlags(HValue *instr, bool is_store) {
+  // set the appropriate GVN flags for a given load or store instruction
+  if (is_store) {
+    // track dominating allocations in order to eliminate write barriers
+    instr->SetGVNFlag(kDependsOnNewSpacePromotion);
+    instr->SetFlag(HValue::kTrackSideEffectDominators);
+  } else {
+    // try to GVN loads, but don't hoist have map changes
+    instr->SetFlag(HValue::kUseGVN);
+    instr->SetGVNFlag(kDependsOnMaps);
+  }
+
+  switch (portion_) {
+    case kArrayLengths:
+      instr->SetGVNFlag(is_store
+          ? kChangesArrayLengths : kDependsOnArrayLengths);
+      break;
+    case kInobject:
+      instr->SetGVNFlag(is_store
+          ? kChangesInobjectFields : kDependsOnInobjectFields);
+      break;
+    case kBackingStore:
+      instr->SetGVNFlag(is_store
+          ? kChangesBackingStoreFields : kDependsOnBackingStoreFields);
+      break;
+    case kElementsPointer:
+      instr->SetGVNFlag(is_store
+          ? kChangesElementsPointer : kDependsOnElementsPointer);
+      break;
+    case kMaps:
+      instr->SetGVNFlag(is_store
+          ? kChangesMaps : kDependsOnMaps);
+      break;
+  }
+}
+
 } }  // namespace v8::internal