[PATCH] D122155: Add warning when eval-method is set in the presence of value unsafe floating-point calculations.

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/include/clang/Basic/DiagnosticFrontendKinds.td:50-53
+def warn_eval_method_setting_via_option_in_value_unsafe_context : Warning<
+    "setting the eval method via '-ffp-eval-method' has not effect when numeric "
+    "results of floating-point calculations aren't value-safe.">,
+    InGroup<IncompatibleFPOpts>;
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andrew.w.kaylor wrote:
> zahiraam wrote:
> > aaron.ballman wrote:
> > > Unless you have a strong reason for this to be a warning, this seems like a situation we should diagnose as an error with a much clearer message.
> > May  be @andrew.w.kaylor would weigh in on this?
> I was going to say that for the command line option we could just issue a warning saying that the later option overrides the earlier, but it's a bit complicated to sort out what that would mean if the eval method follows a fast-math option and it might not always be what the user intended. So, I guess I'd agree that it should be an error.
> 
> For the case with pragmas, the model I'd follow is the mixing of #pragma float_control(except, on) with a fast-math mode or #pragma float_control(precise, off) with a non-ignore exception mode. In both those cases we issue an error.
> For the case with pragmas, the model I'd follow is the mixing of #pragma float_control(except, on) with a fast-math mode or #pragma float_control(precise, off) with a non-ignore exception mode. In both those cases we issue an error.

Good catch, I think that's a good approach as well.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122155/new/

https://reviews.llvm.org/D122155