[llvm] [NVPTX] Enhance `mul.wide` and `mad.wide` peepholes (PR #150477)

[Alex MacLean via llvm-commits]

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@@ -5408,6 +5408,53 @@ static SDValue PerformREMCombine(SDNode *N,
   return SDValue();
 }
 
+// (any_extend|sign_extend|zero_extend (mul|shl) x, y) -> (mul.wide x, y)
+static SDValue
+PerformExtendMULWIDECombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI) {
+  unsigned ExtOpcode = N->getOpcode();
+  assert(ExtOpcode == ISD::ANY_EXTEND || ExtOpcode == ISD::SIGN_EXTEND ||
+         ExtOpcode == ISD::ZERO_EXTEND);
+  EVT ToVT = N->getValueType(0);
+  if (!(ToVT == MVT::i32 || ToVT == MVT::i64))
+    return SDValue();
+  SDValue Op = N->getOperand(0);
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AlexMaclean wrote:

Should we also be checking that `Op` has only one use?

https://github.com/llvm/llvm-project/pull/150477