[llvm] [ConstantFolding] Fix incorrect nvvm_round folding (PR #151563)

[Lewis Crawford via llvm-commits]

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@@ -2679,11 +2679,9 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       case Intrinsic::nvvm_round_ftz_f:
       case Intrinsic::nvvm_round_f:
       case Intrinsic::nvvm_round_d: {
-        // Use APFloat implementation instead of native libm call, as some
-        // implementations (e.g. on PPC) do not preserve the sign of negative 0.
         bool IsFTZ = nvvm::UnaryMathIntrinsicShouldFTZ(IntrinsicID);
         auto V = IsFTZ ? FTZPreserveSign(APF) : APF;
-        V.roundToIntegral(APFloat::rmNearestTiesToAway);
+        V.roundToIntegral(APFloat::rmNearestTiesToEven);
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LewisCrawford wrote:

Good suggestion. I've added a comment about this now.

https://github.com/llvm/llvm-project/pull/151563