[llvm] SelectionDAG: neg (and x, 1) --> SIGN_EXTEND_INREG x, i1 (PR #131239)

[Matthias Braun via llvm-commits]

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@@ -3964,6 +3964,20 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
           isNullConstant(N1S.getOperand(0)))
         return DAG.getSplat(VT, DL, N1S.getOperand(1));
     }
+
+    // sub 0, (and x, 1)  -->  SIGN_EXTEND_INREG x, i1
+    if (N1.getOpcode() == ISD::AND && N1.hasOneUse() &&
+        isOneOrOneSplat(N1->getOperand(1))) {
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MatzeB wrote:

Submitted one as #131367

https://github.com/llvm/llvm-project/pull/131239