Reviewers: Jakob,
Description:
Allow removal of obsolete map checks after transitions.
This allows side effect dominator tracking to remove map checks that are
dominated by a single HStoreNamedField that performs a transition on the
same object. A similar trick could be applied to HAllocateObject.
[email protected]
Please review this at https://chromiumcodereview.appspot.com/12035026/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/hydrogen-instructions.h
M src/hydrogen-instructions.cc
Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index
fc6c3c599a80b06e004d0ec60aff0212f005d587..9df554c2a1db5630267a960e04a0d4f8b15dfe6e
100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1162,6 +1162,26 @@ void HCheckInstanceType::GetCheckMaskAndTag(uint8_t*
mask, uint8_t* tag) {
}
+void HCheckMaps::SetSideEffectDominator(GVNFlag side_effect,
+ HValue* dominator) {
+ ASSERT(side_effect == kChangesMaps);
+ // TODO(mstarzinger): For now we specialize on HStoreNamedField, but once
+ // type information is rich enough we should generalize this to any HType
+ // for which the map is known.
+ if (dominator->IsStoreNamedField()) {
+ HStoreNamedField* store = HStoreNamedField::cast(dominator);
+ Handle<Map> map = store->transition();
+ if (map.is_null() || store->object() != value()) return;
+ for (int i = 0; i < map_set()->length(); i++) {
+ if (map.is_identical_to(map_set()->at(i))) {
+ DeleteAndReplaceWith(NULL);
+ return;
+ }
+ }
+ }
+}
+
+
void HLoadElements::PrintDataTo(StringStream* stream) {
value()->PrintNameTo(stream);
if (HasTypeCheck()) {
Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index
1a43f0fb53fd88f5e68b4e00ac68f49643a8c7c1..5df8b26c5a37002f794eb0f7e8170da85c209740
100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -193,6 +193,7 @@ class LChunkBuilder;
V(WrapReceiver)
#define GVN_TRACKED_FLAG_LIST(V) \
+ V(Maps) \
V(NewSpacePromotion)
#define GVN_UNTRACKED_FLAG_LIST(V) \
@@ -205,7 +206,6 @@ class LChunkBuilder;
V(DoubleArrayElements) \
V(SpecializedArrayElements) \
V(GlobalVars) \
- V(Maps) \
V(ArrayLengths) \
V(ContextSlots) \
V(OsrEntries)
@@ -2248,6 +2248,7 @@ class HCheckMaps: public HTemplateInstruction<2> {
SetOperandAt(1, typecheck != NULL ? typecheck : value);
set_representation(Representation::Tagged());
SetFlag(kUseGVN);
+ SetFlag(kTrackSideEffectDominators);
SetGVNFlag(kDependsOnMaps);
SetGVNFlag(kDependsOnElementsKind);
map_set()->Add(map, zone);
@@ -2257,6 +2258,7 @@ class HCheckMaps: public HTemplateInstruction<2> {
SetOperandAt(1, value);
set_representation(Representation::Tagged());
SetFlag(kUseGVN);
+ SetFlag(kTrackSideEffectDominators);
SetGVNFlag(kDependsOnMaps);
SetGVNFlag(kDependsOnElementsKind);
for (int i = 0; i < maps->length(); i++) {
@@ -2291,7 +2293,7 @@ class HCheckMaps: public HTemplateInstruction<2> {
virtual Representation RequiredInputRepresentation(int index) {
return Representation::Tagged();
}
-
+ virtual void SetSideEffectDominator(GVNFlag side_effect, HValue*
dominator);
virtual void PrintDataTo(StringStream* stream);
virtual HType CalculateInferredType();
--
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