[flang-commits] [flang] [mlir] [mlir][math] Replace roundeven call by nearbyint call when target does not have C23 features (PR #88687)

[Frederik Harwath via flang-commits]

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@@ -185,8 +186,15 @@ void mlir::populateMathToLibmConversionPatterns(RewritePatternSet &patterns) {
   populatePatternsForOp<math::Log10Op>(patterns, ctx, "log10f", "log10");
   populatePatternsForOp<math::Log1pOp>(patterns, ctx, "log1pf", "log1p");
   populatePatternsForOp<math::PowFOp>(patterns, ctx, "powf", "pow");
-  populatePatternsForOp<math::RoundEvenOp>(patterns, ctx, "roundevenf",
-                                           "roundeven");
+  if (options.allowC23Features)
+    populatePatternsForOp<math::RoundEvenOp>(patterns, ctx, "roundevenf",
+                                             "roundeven");
+  else if (options.roundingModeIsDefault)
+    populatePatternsForOp<math::RoundEvenOp>(patterns, ctx, "nearbyintf",
+                                             "nearbyint");
+  // Roundeven: using nearbyint (pre-C23) for roundeven requires the
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frederik-h wrote:

Thanks for the explanation. So I assume that using `nearbyint` instead of `roundeven` should be equivalent as long as no one changes the rounding mode? Or are there other semantics differences? I am wondering if you could handle this in your frontend if there was a `nearbyint` in the math dialect? Not sure if that's better though.

https://github.com/llvm/llvm-project/pull/88687