[llvm] [TargetLowering] Fold (a | b) ==/!= b -> (a & ~b) ==/!= 0 when and-not exists (PR #145368)

[Simon Pilgrim via llvm-commits]

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@@ -4212,6 +4214,42 @@ SDValue TargetLowering::foldSetCCWithAnd(EVT VT, SDValue N0, SDValue N1,
   return SDValue();
 }
 
+/// This helper function of SimplifySetCC tries to optimize the comparison when
+/// either operand of the SetCC node is a bitwise-or instruction.
+/// For now, this just transforms (X | Y) ==/!= Y into X & ~Y ==/!= 0.
+SDValue TargetLowering::foldSetCCWithOr(EVT VT, SDValue N0, SDValue N1,
+                                        ISD::CondCode Cond, const SDLoc &DL,
+                                        DAGCombinerInfo &DCI) const {
+  if (N1.getOpcode() == ISD::OR && N0.getOpcode() != ISD::OR)
+    std::swap(N0, N1);
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RKSimon wrote:

do any of tests cover this?

https://github.com/llvm/llvm-project/pull/145368