ToThis should be able to be eliminated in Constant Folding
https://bugs.webkit.org/show_bug.cgi?id=157213
Reviewed by Saam Barati.
This patch enables eliminating the ToThis value when we have abstract interpreter
indicates the node is not needed. Since there are Objects that override their
ToThis behavior we first check if we can eliminate the node by looking at its
speculated type. If the function is in strict mode then we can eliminate ToThis as
long as the speculated type is not SpecObjectOther since that contains objects
that may set OverridesToThis. If the function is not in strict mode then we can
eliminate ToThis as long is the speculated type is an object that is not SpecObjectOther.
If we can't eliminate with type information we can still eliminate the ToThis node with
the proven structure set. When ToThis only sees structures that do not set OverridesToThis
it can be eliminated. Additionally, if the function is in strict mode then we can eliminate
ToThis as long as all only the object structures don't set OverridesToThis.
* dfg/DFGAbstractInterpreterInlines.h:
(JSC::DFG::isToThisAnIdentity):
(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):
* dfg/DFGConstantFoldingPhase.cpp:
(JSC::DFG::ConstantFoldingPhase::foldConstants):
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupToThis):
* tests/stress/to-this-global-object.js: Added.
(test):
(test2):
(get for):
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@200325 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp b/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp
index 3d5f17f..c434bcc 100644
--- a/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp
+++ b/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp
@@ -1728,6 +1728,9 @@
return;
}
+ // FIXME: This should cover other use cases but we don't have use kinds for them. It's not critical,
+ // however, since we cover all the missing cases in constant folding.
+ // https://bugs.webkit.org/show_bug.cgi?id=157213
if (node->child1()->shouldSpeculateStringObject()) {
fixEdge<StringObjectUse>(node->child1());
node->convertToIdentity();
