[llvm-dev] [FPEnv] FNEG instruction

[Cameron McInally via llvm-dev]

On Thu, Sep 27, 2018 at 10:14 AM Sanjay Patel <spatel at rotateright.com>
wrote:

> Regarding non-IEEE targets: yes, we definitely support those, so we do
> have to be careful about not breaking them. I know because I have broken
> them. :)
> See the discussion and related links here: https://reviews.llvm.org/D19391
>
> But having an exactly specified fneg op makes that easier, not harder, as
> I see it. Unfortunately, if a target doesn't support this op (always toggle
> the sign bit and only the sign bit), then we can't canonicalize 'fsub -0.0,
> X' to 'fneg X' because those are not identical ops (denorms, NaN).
>
> So that leads back to the m_FNeg abstraction - it will have to match both
> ops to not lose optimizations.
>

I like this idea.

So how do we get official approval to begin this work?
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