[llvm-dev] [FPEnv] FNEG instruction (original) (raw)

Cameron McInally via llvm-dev llvm-dev at lists.llvm.org
Tue Oct 2 12:24:33 PDT 2018

On Tue, Oct 2, 2018 at 3:11 PM Roman Lebedev <lebedev.ri at gmail.com> wrote:

On Tue, Oct 2, 2018 at 10:06 PM Cameron McInally via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > On Mon, Oct 1, 2018 at 5:41 PM Sanjay Patel <spatel at rotateright.com> wrote: >> >> I don't see any controversy for the preliminary requirement of removing BinaryOperator::isFNeg() and friends, so start with that? >> That work may reveal other potential regressions that we can patch in advance too. > > > This is true and I will agree to do this work... > >> >> Other than that, I think there's really only a question of do we want 1 or both of fneg and fnegconstrained (and if we choose both, then I assume we'd also add fabsconstrained and copysignconstrained). > > > but this is the real goal. Doing the BinaryOperator::isFNeg() work is in vain if we don't have at least a conditional approval of an explicit FNEG IR instruction. > > Would it be possible to obtain that conditional approval before work begins? That seems most prudent.

Will this affect (regress, pessimize) the current optimizations for

non-strict cases? What about -ffast-math?

The goal is for no regressions, but there may be problems to work through to get there.

-ffast-math allows for unsafe transformations, so should remain unchanged. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181002/7e27faca/attachment.html>

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