[llvm] [SelectionDAG] Make `(a & x) | (~a & y) -> (a & (x ^ y)) ^ y` available for all targets (PR #137641)

[Simon Pilgrim via llvm-commits]

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@@ -8110,6 +8110,59 @@ static SDValue visitORCommutative(SelectionDAG &DAG, SDValue N0, SDValue N1,
   return SDValue();
 }
 
+static SDValue foldMaskedMergeImpl(SDValue AndL0, SDValue AndR0, SDValue AndL1,
+                                   SDValue AndR1, const SDLoc &DL,
+                                   SelectionDAG &DAG) {
+  if (!isBitwiseNot(AndL0, true) || !AndL0->hasOneUse())
+    return SDValue();
+  SDValue NotOp = AndL0->getOperand(0);
+  if (NotOp == AndR1)
+    std::swap(AndR1, AndL1);
+  if (NotOp != AndL1)
+    return SDValue();
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RKSimon wrote:

Can you use SDPatternMatch instead to match this?

https://github.com/llvm/llvm-project/pull/137641