EffectAnalyzer: Do not reorder mayNotReturn with traps or global writes - #9211
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Expressions that may not return (loops, atomic.wait, struct.wait) can fail to terminate, which would prevent a subsequent trap or global state write (including calls) from ever executing. Update EffectAnalyzer::orderedBefore to disallow reordering mayNotReturn with traps or global writes, set mayNotReturn on AtomicWait, and clear loopEffects.mayNotReturn in LoopInvariantCodeMotion for the whole loop summary. Fixes #9182.
kripken
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Oct 5, 2026
| // Cannot reorder code that may not return with traps or global state | ||
| // changes. | ||
| if ((mayNotReturn && (other.trap || other.writesGlobalState())) || | ||
| (other.mayNotReturn && (trap || writesGlobalState()))) { |
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Why handle traps and not throws etc?
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The throws case and other control flow cases are already handled here: https://github.com/WebAssembly/binaryen/pull/9211/changes#diff-963609105fd78eff33b9674f5f72d45b5b8dbb8d8e4c866085fdd8c994b51a84R341-R345. mayNotReturn is already considered a side effect, so it is not reordered with respect to control flow.
kripken
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Oct 5, 2026
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Expressions that may not return (loops, atomic.wait, struct.wait) can fail to terminate, which would prevent a subsequent trap or global state write (including calls) from ever executing. Update EffectAnalyzer::orderedBefore to disallow reordering mayNotReturn with traps or global writes, set mayNotReturn on AtomicWait, and clear loopEffects.mayNotReturn in LoopInvariantCodeMotion for the whole loop summary.
Fixes #9182.