[llvm-dev] PR43374 - when should comparing NaN values raise a floating point exception?

Kristof Beyls via llvm-dev llvm-dev at lists.llvm.org
Fri Oct 11 00:44:01 PDT 2019


Op do 10 okt. 2019 om 18:39 schreef Ulrich Weigand via llvm-dev <
llvm-dev at lists.llvm.org>:

> Kevin Neal <Kevin.Neal at sas.com> wrote on 01.10.2019 16:25:55:
>
> > Ulrich offered to do it instead since I expect he can get it done
> > much faster than me. Instead I'm doing SIToFP and UIToFP. Ulrich
> > said he wasn't going to be able to get to it for a couple of weeks,
> > but that was a week or two ago.
>
> Sorry for the late reply, I've been traveling ...
>
> Yes, I'll start looking into strict FP comparisons.  One issue is
> indeed that we'll need to support both signaling and non-signaling
> comparisons.
>
> My prefered solution would probably be to have two sets of strict
> intrinsics, one for signaling compares and one for non-signaling
> ones, implement those in the back-ends using the appropriate set
> of signaling vs. non-signaling instructions, and then leave it to
> the front-end to chose which of the two to use when, in order to
> implement the semantics mandated by the language standard.
>
> Thanks for sharing your thoughts, Ulrich. The approach described above
seems to make sense to me.
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