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[turbofan] Infer receiver maps from earlier map checks.

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When trying to infer receiver maps for property accesses, go hunting in
the effect chain to find an earlier CheckMaps or StoreField for the
receiver.

BUG=v8:5267
R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2704563005
Cr-Commit-Position: refs/heads/master@{#43274}
This commit is contained in:
bmeurer 2017-02-17 02:48:32 -08:00 committed by Commit bot
parent 3503ddf0db
commit 4b07a97978
1 changed files with 28 additions and 1 deletions
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29
src/compiler/js-native-context-specialization.cc
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@ -2178,7 +2178,34 @@ MaybeHandle<Map> JSNativeContextSpecialization::InferReceiverMap(Node* receiver,
}
}
}
// TODO(turbofan): Go hunting for CheckMaps(receiver) in the effect chain?
// Go hunting for a matching CheckMaps(receiver) or StoreField[Map](receiver)
// in the {effect} chain.
// TODO(turbofan): Propagate the information along the control/effect chains
// instead at some point to avoid this potentially inefficient hunting.
while (true) {
if (effect->opcode() == IrOpcode::kCheckMaps) {
ZoneHandleSet<Map> maps = CheckMapsParametersOf(effect->op()).maps();
if (maps.size() == 1u) {
Node* object = NodeProperties::GetValueInput(effect, 0);
if (NodeProperties::IsSame(receiver, object)) return maps[0];
}
} else if (effect->opcode() == IrOpcode::kStoreField) {
FieldAccess const access = FieldAccessOf(effect->op());
if (access.offset == HeapObject::kMapOffset) {
Node* object = NodeProperties::GetValueInput(effect, 0);
Node* value = NodeProperties::GetValueInput(effect, 1);
if (object == receiver) {
HeapObjectMatcher m(value);
if (m.HasValue()) return Handle<Map>::cast(m.Value());
}
break;
}
} else if (!effect->op()->HasProperty(Operator::kNoWrite) ||
effect->op()->EffectInputCount() != 1) {
break;
}
effect = NodeProperties::GetEffectInput(effect);
}
return MaybeHandle<Map>();
}