[llvm] [IR][DAG] Add support for `nneg` flag with `uitofp` (PR #86141)

[Simon Pilgrim via llvm-commits]

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@@ -54062,7 +54062,8 @@ static SDValue combineUIntToFP(SDNode *N, SelectionDAG &DAG,
   // Since UINT_TO_FP is legal (it's marked custom), dag combiner won't
   // optimize it to a SINT_TO_FP when the sign bit is known zero. Perform
   // the optimization here.
-  if (DAG.SignBitIsZero(Op0)) {
+  SDNodeFlags Flags = N->getFlags();
+  if (Flags.hasNonNeg() || DAG.SignBitIsZero(Op0)) {
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RKSimon wrote:

Please can you add some test coverage (maybe to uint_to_fp.ll?)

https://github.com/llvm/llvm-project/pull/86141