Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: c3b478c1983f5de5b1b216aa888ca5b47c738ac3
https://github.com/WebKit/WebKit/commit/c3b478c1983f5de5b1b216aa888ca5b47c738ac3
Author: Keith Miller <[email protected]>
Date: 2025-09-17 (Wed, 17 Sep 2025)
Changed paths:
A JSTests/stress/array-allocation-elimination-closure-capture.js
A JSTests/stress/array-allocation-elimination-conditional-usage.js
A JSTests/stress/array-allocation-elimination-cross-function.js
A
JSTests/stress/array-allocation-elimination-loop-unroll-materialize-at-osr.js
A JSTests/stress/array-allocation-sink-with-osr-exit-materialization.js
A
JSTests/stress/array-sink-osr-materialization-self-reference-in-butterfly.js
A JSTests/stress/array-sink-osr-materialization.js
M Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h
M Source/JavaScriptCore/dfg/DFGBackwardsPropagationPhase.cpp
M Source/JavaScriptCore/dfg/DFGClobberize.h
M Source/JavaScriptCore/dfg/DFGCloneHelper.h
M Source/JavaScriptCore/dfg/DFGConstantFoldingPhase.cpp
M Source/JavaScriptCore/dfg/DFGDoesGC.cpp
M Source/JavaScriptCore/dfg/DFGFixupPhase.cpp
M Source/JavaScriptCore/dfg/DFGLoopUnrollingPhase.cpp
M Source/JavaScriptCore/dfg/DFGMayExit.cpp
M Source/JavaScriptCore/dfg/DFGNode.cpp
M Source/JavaScriptCore/dfg/DFGNode.h
M Source/JavaScriptCore/dfg/DFGNodeType.h
M Source/JavaScriptCore/dfg/DFGObjectAllocationSinkingPhase.cpp
M Source/JavaScriptCore/dfg/DFGObjectMaterializationData.h
M Source/JavaScriptCore/dfg/DFGOperations.cpp
M Source/JavaScriptCore/dfg/DFGOperations.h
M Source/JavaScriptCore/dfg/DFGPredictionPropagationPhase.cpp
M Source/JavaScriptCore/dfg/DFGPromotedHeapLocation.h
M Source/JavaScriptCore/dfg/DFGSafeToExecute.h
M Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp
M Source/JavaScriptCore/dfg/DFGSpeculativeJIT.h
M Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp
M Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp
M Source/JavaScriptCore/dfg/DFGStoreBarrierInsertionPhase.cpp
M Source/JavaScriptCore/dfg/DFGUseKind.h
M Source/JavaScriptCore/dfg/DFGValidate.cpp
M Source/JavaScriptCore/ftl/FTLCapabilities.cpp
M Source/JavaScriptCore/ftl/FTLExitTimeObjectMaterialization.cpp
M Source/JavaScriptCore/ftl/FTLExitTimeObjectMaterialization.h
M Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp
M Source/JavaScriptCore/ftl/FTLOperations.cpp
M Source/JavaScriptCore/ftl/FTLOperations.h
M Source/JavaScriptCore/runtime/IndexingType.cpp
M Source/JavaScriptCore/runtime/IndexingType.h
Log Message:
-----------
Array allocation sinking should split allocations into two, an Array
allocation and a Butterfly allocation
rdar://159207754
https://bugs.webkit.org/show_bug.cgi?id=298606
Reviewed by Yusuke Suzuki.
This patch minorly rearchitects how we do Array allocation sinking in DFG.
Previously we tried to model Arrays
in ObjectAllocationSinking as two allocations one where the actual Array was
allocated and a "Butterfly"
at each `GetButterfly`. This meant that there was now a reverse data dependency
between the GetButterfly and
the Array allocation Nodes. This was a little unintuitive but also meant that
any control flow that would
merge two `GetButterfly`s would escape the Array.
This PR simplifies things by more directly representing the heap in
ObjectAllocationSinking. There are now
two nodes that get sunk when sinking an Array: NewButterflyWithSize and
NewArrayWithButterfly. All the
indexed properties and the Butterfly's location are stored on the
NewArrayWithButterfly's Allocation.
The NewButterflyWithSize only contains the Array's length. If we ever wanted to
extend Array allocation sinking
to support out of bounds stores we'd have to teach `handleNode` how to deal
with writes to multiple allocations.
Originally I had all the indexed properties and the length are stored on the
LocalHeap of NewButterflyWithSize and
NewArrayWithButterfly's LocalHeap only contains the butterfly. But I realized
that we crash while trying to materialize
a phantom array that contains itself or another newly materialized object
that's in a cycle. This is because we have to
materialize the pointer as a PutByVal. We can't emit this PutByVal without the
Array since we need to write barrier after
the store.
Overall, this change is perf neutral or maybe a slight progression on JetStream
3.
Canonical link: https://commits.webkit.org/300129@main
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