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

[Thorsten Schütt via llvm-commits]

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@@ -3882,7 +3882,15 @@ void SelectionDAGBuilder::visitUIToFP(const User &I) {
   SDValue N = getValue(I.getOperand(0));
   EVT DestVT = DAG.getTargetLoweringInfo().getValueType(DAG.getDataLayout(),
                                                         I.getType());
-  setValue(&I, DAG.getNode(ISD::UINT_TO_FP, getCurSDLoc(), DestVT, N));
+  bool IsNonNeg = false;
+  if (auto *PNI = dyn_cast<PossiblyNonNegInst>(&I))
+    IsNonNeg = true;
+
+  unsigned Opc = ISD::UINT_TO_FP;
+  if (IsNonNeg && DAG.getTargetLoweringInfo().isSIToFPCheaperThanUIToFP(
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tschuett wrote:

It should have been unary op.

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