DFG::StrCat isn't really effectful
authorfpizlo@apple.com <fpizlo@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Thu, 27 Aug 2015 23:59:57 +0000 (23:59 +0000)
committerfpizlo@apple.com <fpizlo@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Thu, 27 Aug 2015 23:59:57 +0000 (23:59 +0000)
commitb79ca897b5b42bcec6250c647ba29650a73042a3
tree47c3370e890145a45ad553b25936de2513d60ae3
parent69093927c023f5e6460992598e67b58001a0fc0b
DFG::StrCat isn't really effectful
https://bugs.webkit.org/show_bug.cgi?id=148443

Reviewed by Geoffrey Garen.

I previously made the DFG StrCat node effectful because it is implemented by calling a
DFGOperations function that could cause arbitrary effects. But, the node is only generated from the
op_strcat bytecode operation, and that operation is only used when we first ensure that its
operands are primitives. Primitive operands to StrCat cannot cause arbitrary side-effects. The
reason why I didn't immediately mark StrCat as pure was because there was nothing in DFG IR that
guaranteed that StrCat's children were primitives.

This change adds a KnownPrimitiveUse use kind, and applies it to StrCat. This allows us to mark
StrCat as being pure. This should be a speed-up because we can CSE StrCat and because it means that
we can OSR exit after a StrCat (a pure node doesn't clobber exit state), so we can convert more
of a large string concatenation into MakeRope's.

* dfg/DFGAbstractInterpreterInlines.h:
(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):
* dfg/DFGClobberize.h:
(JSC::DFG::clobberize):
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupNode):
(JSC::DFG::FixupPhase::attemptToMakeFastStringAdd):
* dfg/DFGOperations.cpp:
* dfg/DFGSafeToExecute.h:
(JSC::DFG::SafeToExecuteEdge::operator()):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::speculate):
* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGUseKind.cpp:
(WTF::printInternal):
* dfg/DFGUseKind.h:
(JSC::DFG::typeFilterFor):
(JSC::DFG::shouldNotHaveTypeCheck):
* ftl/FTLCapabilities.cpp:
(JSC::FTL::canCompile):
* ftl/FTLLowerDFGToLLVM.cpp:
(JSC::FTL::DFG::LowerDFGToLLVM::compileStrCat):
(JSC::FTL::DFG::LowerDFGToLLVM::speculate):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@189075 268f45cc-cd09-0410-ab3c-d52691b4dbfc
13 files changed:
Source/JavaScriptCore/ChangeLog
Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h
Source/JavaScriptCore/dfg/DFGClobberize.h
Source/JavaScriptCore/dfg/DFGFixupPhase.cpp
Source/JavaScriptCore/dfg/DFGOperations.cpp
Source/JavaScriptCore/dfg/DFGSafeToExecute.h
Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp
Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp
Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp
Source/JavaScriptCore/dfg/DFGUseKind.cpp
Source/JavaScriptCore/dfg/DFGUseKind.h
Source/JavaScriptCore/ftl/FTLCapabilities.cpp
Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp