[DAG] visitORCommutative - use sd_match to reduce the need for commutative operand matching. NFCI.

Use sd_match to match commutative inner AND/OR/XOR node arguments instead of some messy manual matching of each commutation.

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -7655,23 +7655,17 @@ static SDValue visitORCommutative(SelectionDAG &DAG, SDValue N0, SDValue N1,
     }
   }
 
-  if (N0.getOpcode() == ISD::XOR) {
-    // fold or (xor x, y), x --> or x, y
-    //      or (xor x, y), (x and/or y) --> or x, y
-    SDValue N00 = N0.getOperand(0);
-    SDValue N01 = N0.getOperand(1);
-    if (N00 == N1)
-      return DAG.getNode(ISD::OR, SDLoc(N), VT, N01, N1);
-    if (N01 == N1)
-      return DAG.getNode(ISD::OR, SDLoc(N), VT, N00, N1);
+  SDValue X, Y;
 
-    if (N1.getOpcode() == ISD::AND || N1.getOpcode() == ISD::OR) {
-      SDValue N10 = N1.getOperand(0);
-      SDValue N11 = N1.getOperand(1);
-      if ((N00 == N10 && N01 == N11) || (N00 == N11 && N01 == N10))
-        return DAG.getNode(ISD::OR, SDLoc(N), VT, N00, N01);
-    }
-  }
+  // fold or (xor X, N1), N1 --> or X, N1
+  if (sd_match(N0, m_Xor(m_Value(X), m_Specific(N1))))
+    return DAG.getNode(ISD::OR, SDLoc(N), VT, X, N1);
+
+  // fold or (xor x, y), (x and/or y) --> or x, y
+  if (sd_match(N0, m_Xor(m_Value(X), m_Value(Y))) &&
+      (sd_match(N1, m_And(m_Specific(X), m_Specific(Y))) ||
+       sd_match(N1, m_Or(m_Specific(X), m_Specific(Y)))))
+    return DAG.getNode(ISD::OR, SDLoc(N), VT, X, Y);
 
   if (SDValue R = foldLogicOfShifts(N, N0, N1, DAG))
     return R;