[llvm] [InstCombine] Remove shl if we only demand known signbits of shift source (PR #79014)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 29 08:11:04 PST 2024
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@@ -640,25 +640,31 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
DemandedMask, Known))
return R;
- // TODO: If we only want bits that already match the signbit then we don't
+ uint64_t ShiftAmt = SA->getLimitedValue(BitWidth - 1);
+ // If we only want bits that already match the signbit then we don't
// need to shift.
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nikic wrote:
It looks like you ended up dropping this comment entirely instead.
https://github.com/llvm/llvm-project/pull/79014
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