================
@@ -874,6 +874,30 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
SrcTy.getScalarSizeInBits());
break;
}
+ case TargetOpcode::G_SHUFFLE_VECTOR: {
+ // Collect the minimum number of sign bits that are shared by every vector
+ // element referenced by the shuffle.
+ APInt DemandedLHS, DemandedRHS;
+ unsigned NumElts = MRI.getType(MI.getOperand(1).getReg()).getNumElements();
+ if (!getShuffleDemandedElts(NumElts, MI.getOperand(3).getShuffleMask(),
+ DemandedElts, DemandedLHS, DemandedRHS))
+ return 1;
+
+ unsigned Tmp = std::numeric_limits<unsigned>::max();
+ if (!!DemandedLHS)
+ Tmp =
+ computeNumSignBits(MI.getOperand(1).getReg(), DemandedLHS, Depth +
1);
+ if (!!DemandedRHS) {
+ unsigned Tmp2 =
+ computeNumSignBits(MI.getOperand(2).getReg(), DemandedRHS, Depth +
1);
+ Tmp = std::min(Tmp, Tmp2);
+ }
+ // If we don't know anything, early out and try computeKnownBits fall-back.
+ if (Tmp == 1)
+ break;
+ assert(Tmp <= TyBits && "Failed to determine minimum sign bits");
----------------
jayfoad wrote:
I don't think this is particularly useful. You could just initialize `Tmp` to
`TyBits` instead.
https://github.com/llvm/llvm-project/pull/139505
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