Reviewers: Yang,
Description:
Add support to turn polymorphic loads from the same prototype into a
monomorphic
load.
[email protected]
Please review this at https://chromiumcodereview.appspot.com/18887002/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/hydrogen.cc
Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index
591b870a44292e3cc0bf947248d370f23a01a836..fa719298da2df178009c63a161c7db3e7000b9be
100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -4978,12 +4978,40 @@ HInstruction*
HOptimizedGraphBuilder::TryLoadPolymorphicAsMonomorphic(
representation = representation.generalize(new_representation);
}
- if (count != types->length()) return NULL;
+ if (count == types->length()) {
+ // Everything matched; can use monomorphic load.
+ BuildCheckHeapObject(object);
+ AddInstruction(HCheckMaps::New(object, types, zone()));
+ return BuildLoadNamedField(object, access, representation);
+ }
+
+ if (count != 0) return NULL;
+
+ // Second chance: the property is on the prototype and all maps have the
+ // same prototype.
+ Handle<Map> map(types->at(0));
+
+ Handle<JSObject> prototype(JSObject::cast(map->prototype()));
+ for (count = 1; count < types->length(); ++count) {
+ Handle<Map> test_map(types->at(count));
+ // Ensure the property is on the prototype, not the object itself.
+ if (ComputeLoadStoreField(test_map, name, &lookup, false)) return NULL;
+ if (test_map->prototype() != *prototype) return NULL;
+ }
+
+ LookupInPrototypes(map, name, &lookup);
+ if (!lookup.IsField()) return NULL;
- // Everything matched; can use monomorphic load.
BuildCheckHeapObject(object);
AddInstruction(HCheckMaps::New(object, types, zone()));
- return BuildLoadNamedField(object, access, representation);
+ Handle<JSObject> holder(lookup.holder());
+ Handle<Map> holder_map(holder->map());
+ AddInstruction(new(zone()) HCheckPrototypeMaps(
+ prototype, holder, zone(), top_info()));
+ HValue* holder_value = AddInstruction(new(zone()) HConstant(holder));
+ return BuildLoadNamedField(holder_value,
+ HObjectAccess::ForField(holder_map, &lookup, name),
+ ComputeLoadStoreRepresentation(map, &lookup));
}
--
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