[llvm] [DAG] Fold (and X, (bswap/bitreverse (not Y))) -> (and X, (not (bswap/bitreverse Y))) on ANDNOT capable targets (PR #112547)

[via llvm-commits]

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@@ -7350,6 +7350,21 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
   if (SDValue R = foldLogicOfShifts(N, N1, N0, DAG))
     return R;
 
+  // If the target supports ANDNOT, attempt to reconstruct an ANDNOT pattern
+  // that might have become separated by a bitwise-agnostic instruction.
+  if (TLI.hasAndNot(SDValue(N, 0))) {
+    SDValue X, Y;
+
+    // Fold (and X, (bswap (not Y))) -> (and X, (not (bswap Y)))
+    // Fold (and X, (bitreverse (not Y))) -> (and X, (not (bitreverse Y)))
+    for (unsigned Opc : {ISD::BSWAP, ISD::BITREVERSE})
+      if (sd_match(N, m_And(m_Value(X),
+                            m_OneUse(m_UnaryOp(Opc, m_Not(m_Value(Y)))))) &&
+          !sd_match(X, m_Not(m_Value())))
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goldsteinn wrote:

I guess assuming `~Y` is one-use.

https://github.com/llvm/llvm-project/pull/112547