[llvm] [DAG] fold avgu(zext(x), zext(y)) -> zext(avgu(x, y)) (PR #95134)

[Jay Foad via llvm-commits]

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@@ -5236,6 +5236,21 @@ SDValue DAGCombiner::visitAVG(SDNode *N) {
     return DAG.getNode(ISD::SRL, DL, VT, X,
                        DAG.getShiftAmountConstant(1, VT, DL));
 
+  // fold avgu(zext(x), zext(y)) -> zext(avgu(x, y))
+  SDValue A;
+  SDValue B;
+  if (hasOperation(ISD::AVGFLOORU, VT) &&
+      sd_match(N, m_c_BinOp(ISD::AVGFLOORU, m_ZExt(m_Value(A)),
+                            m_ZExt(m_Value(B))))) {
+    SDValue AvgFloorU = DAG.getNode(ISD::AVGFLOORU, DL, A.getValueType(), A, B);
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jayfoad wrote:

Don't you also need to check that A and B are both being extended _from_ the same size?

https://github.com/llvm/llvm-project/pull/95134