[llvm-branch-commits] [llvm] [SelectionDAG] Handle constants in SimplifyMultipleUseDemandedBits (PR #224882)

[Simon Pilgrim via llvm-branch-commits]

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@@ -766,6 +766,12 @@ SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
   unsigned BitWidth = DemandedBits.getBitWidth();
   KnownBits LHSKnown, RHSKnown;
   switch (Op.getOpcode()) {
+  case ISD::Constant: {
+    const APInt &Value = Op->getAsAPIntVal();
+    if (!Value.isZero() && (Value & DemandedBits).isZero())
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RKSimon wrote:

I'm not sure about adding general constant folding - SimplifyMultipleUseDemandedBits is mainly about bypassing unnecessary nodes not creating new ones - returning zero is probably as far as I'd recommend we go and we should rely on folds making use of ComputeKnownBits to handle other cases.

https://github.com/llvm/llvm-project/pull/224882