[llvm] [X86] Add DAG combiner for X86ISD::XOR to eliminate redundant XORs (PR #216134)

[via llvm-commits]

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@@ -59394,6 +59394,26 @@ static SDValue combineCMP(SDNode *N, SelectionDAG &DAG,
   return Op.getValue(1);
 }
 
+/// If a matching generic opcode node exists, replace its uses with the value
+/// of the target-specific node N.
+static void matchGenericOp(unsigned Opc, SDNode *N, SDValue N0, SDValue N1,
+                           SelectionDAG &DAG,
+                           TargetLowering::DAGCombinerInfo &DCI,
+                           bool Negate = false) {
+  SDValue Ops[] = {N0, N1};
+  SDVTList VTs = DAG.getVTList(N->getValueType(0));
+  if (SDNode *Generic = DAG.getNodeIfExists(Opc, VTs, Ops)) {
+    SDValue Op(N, 0);
+    if (Negate) {
+      // Bail if this is only used by a user of the x86 node.
+      if (Generic->hasOneUse() && Generic->user_begin()->isOnlyUserOf(N))
+        return;
+      Op = DAG.getNegative(Op, SDLoc(N), N->getSimpleValueType(0));
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AZero13 wrote:

And I did.

https://github.com/llvm/llvm-project/pull/216134