================
@@ -720,18 +720,17 @@ SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
unsigned Scale = NumDstEltBits / NumSrcEltBits;
unsigned NumSrcElts = SrcVT.getVectorNumElements();
APInt DemandedSrcBits = APInt::getZero(NumSrcEltBits);
- APInt DemandedSrcElts = APInt::getZero(NumSrcElts);
for (unsigned i = 0; i != Scale; ++i) {
unsigned EltOffset = IsLE ? i : (Scale - 1 - i);
unsigned BitOffset = EltOffset * NumSrcEltBits;
APInt Sub = DemandedBits.extractBits(NumSrcEltBits, BitOffset);
- if (!Sub.isZero()) {
+ if (!Sub.isZero())
DemandedSrcBits |= Sub;
- for (unsigned j = 0; j != NumElts; ++j)
- if (DemandedElts[j])
- DemandedSrcElts.setBit((j * Scale) + i);
- }
}
+ // Need to demand all smaller source elements that maps to a demanded
+ // destination element, since recursive calls below may turn not demanded
+ // elements into poison.
+ APInt DemandedSrcElts = APIntOps::ScaleBitMask(DemandedElts, NumSrcElts);
----------------
bjope wrote:
Checking for poison before calling Simplify* does not work as long as the
Simply* functions are allowed to turn undemanded elements into poison.
So the idea would be that for SimplifyMultipleUseDemandedBits/VectorElts, when
we get the new value back, then we can freeze that value instead of passing
along the "DoNotPoison" mask as in
https://github.com/llvm/llvm-project/pull/145903/
That was difficult to do for the normal SimplifyDemandedVectorElts that is
doing the RAUW under the hood, but might work for the MultipleUse case.
https://github.com/llvm/llvm-project/pull/145902
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