Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: e0d2a13f551fe60f4893b41479de31884fe84751
https://github.com/WebKit/WebKit/commit/e0d2a13f551fe60f4893b41479de31884fe84751
Author: Yijia Huang <yijia_hu...@apple.com>
Date: 2025-01-06 (Mon, 06 Jan 2025)
Changed paths:
A JSTests/stress/loop-unrolling-branch.js
M Source/JavaScriptCore/dfg/DFGLoopUnrollingPhase.cpp
Log Message:
-----------
[JSC] Loop unrolling phase should inverse the condition if needed before
computing the iteration count
https://bugs.webkit.org/show_bug.cgi?id=285473
rdar://142439066
Reviewed by Yusuke Suzuki.
Previously, loop unrolling failed to handle cases where the loop's
"not taken" branch pointed back into the loop, requiring condition
inversion. This led to incorrect comparisons, invalid iteration
counts, and missed optimization opportunities.
This fix introduces `inverseCondition` to track whether the condition
needs inversion and updates `comparisonFunction` to apply the correct
comparison logic dynamically. It improves robustness, ensures accurate
unrolling for complex branching structures, and adds better debug information.
* JSTests/stress/loop-unrolling-branch.js: Added.
* Source/JavaScriptCore/dfg/DFGLoopUnrollingPhase.cpp:
(JSC::DFG::LoopUnrollingPhase::LoopData::condition const):
(JSC::DFG::LoopUnrollingPhase::locateTail):
(JSC::DFG::LoopUnrollingPhase::identifyInductionVariable):
(JSC::DFG::LoopUnrollingPhase::LoopData::dump const):
(JSC::DFG::LoopUnrollingPhase::comparisonFunction):
Canonical link: https://commits.webkit.org/288509@main
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