[41.0.0] x64: Fix lowering rules for shld
#12323
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* x64: Fix lowering rules for `shld` These failed to account for the edge case of 0/width(type) shifts where the `shld` instruction is no longer applicable. Guards are added to ensure that the shift amounts are both greater than zero. This in theory shouldn't have much practical impact since shift-by-zero and shift-by-type-width are both optimized away in the mid-end. That means that this is only possible to expose with opt-level=0 which may help explain why this went undiscovered for ~1 year. Closes bytecodealliance#12318 * Fix Winch's encoding of shift-by-32
alexcrichton
requested review from
cfallin and
dicej
and removed request for
a team
cfallin
approved these changes
Jan 12, 2026
alexcrichton
merged commit 7e98de5
into
bytecodealliance:release-41.0.0
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Backport of #12321