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 fc57aa879c68111e4158f7db07ebe685c2790110..db7cd3ad3de3f022700ddf5f19b6fecb767e25e0 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -2464,7 +2464,7 @@ void HParameter::PrintDataTo(StringStream* stream) {
 
 void HLoadNamedField::PrintDataTo(StringStream* stream) {
   object()->PrintNameTo(stream);
-  stream->Add(" @%d%s", offset(), is_in_object() ? "[in-object]" : "");
+  access_.PrintTo(stream);
   if (HasTypeCheck()) {
     stream->Add(" ");
     typecheck()->PrintNameTo(stream);
@@ -2757,11 +2757,9 @@ void HStoreNamedGeneric::PrintDataTo(StringStream* stream) {
 
 void HStoreNamedField::PrintDataTo(StringStream* stream) {
   object()->PrintNameTo(stream);
-  stream->Add(".");
-  stream->Add(*String::cast(*name())->ToCString());
+  access_.PrintTo(stream);
   stream->Add(" = ");
   value()->PrintNameTo(stream);
-  stream->Add(" @%d%s", offset(), is_in_object() ? "[in-object]" : "");
   if (NeedsWriteBarrier()) {
     stream->Add(" (write-barrier)");
   }
@@ -3628,4 +3626,117 @@ void HCheckFunction::Verify() {
 
 #endif
 
+
+HObjectAccess HObjectAccess::For(bool is_inobject, int offset) {
+  if (is_inobject) return ForOffset(offset, Handle<String>::null());
+  return HObjectAccess(kBackingStore, offset, Handle<String>::null());
+}
+
+
+HObjectAccess HObjectAccess::ForOffset(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?

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

This is only true for arrays, which should _always_ use the ForArrayLength
variant. This case should be removed, it is just another case of kInobject.

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

I've split this into ForJSObjectOffset and ForJSArrayOffset.

+  } else if (offset == JSObject::kMapOffset) {
+    portion = kMaps;
+  }
+  return HObjectAccess(portion, offset, name);
+}
+
+
+HObjectAccess HObjectAccess::ForField(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 HObjectAccess(kInobject, offset);
+  } else {
+    // Non-negative property indices are in the properties array.
+    int offset = (index * kPointerSize) + FixedArray::kHeaderSize;
+    return 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;
+  }
+}
+
+
+void HObjectAccess::PrintTo(StringStream* stream) {
+  stream->Add(".@%d", offset_);
+
+  // several portions have well-known names
+  switch (portion_) {
+    case kArrayLengths:
+      stream->Add("[array-length]");
+      return;
+    case kElementsPointer:
+      stream->Add("[elements]");
+      return;
+    case kMaps:
+      stream->Add("[map]");
+      return;
+    case kInobject:
+      stream->Add("[in-object]");
+      break;  // also print the name if possible
+  }
+
+  // otherwise, add the name if it is known
+  if (!name_.is_null()) {
+    stream->Add(" name[");
+    stream->Add(*String::cast(*name_)->ToCString());
+    stream->Add("]");
+  }
+}
+
 } }  // namespace v8::internal