[llvm] [DAG] Matched FixedWidth pattern for ISD::AVGFLOORU (PR #84903)

[Jay Foad via llvm-commits]

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@@ -2820,6 +2820,22 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
   return SDValue();
 }
 
+// Attempt to form avgflooru(A, B) from add(and(A, B), lshr(xor(A, B), 1))
+static SDValue combineFixedwidthToAVGFLOORU(SDNode *N, SelectionDAG &DAG) {
+  const TargetLowering &TLI = DAG.getTargetLoweringInfo();
+  SDValue N0 = N->getOperand(0);
+  EVT VT = N0.getValueType();
+  SDLoc DL(N);
+  if (TLI.isOperationLegal(ISD::AVGFLOORU, VT)) {
+    SDValue A, B;
+    if (sd_match(N, m_Add(m_And(m_Value(A), m_Value(B)),
+                          m_Srl(m_Xor(m_Deferred(A), m_Deferred(B)),
+                                m_SpecificInt(1))))) {
+      return DAG.getNode(ISD::AVGFLOORU, DL, VT, A, B);
+    }
+  }
+}
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jayfoad wrote:

Missing `return SDValue()` at the end of the function. (Doesn't your compiler warn about that?)

https://github.com/llvm/llvm-project/pull/84903