[llvm-dev] [FPEnv] FNEG instruction

[Cameron McInally via llvm-dev]

On Tue, Oct 2, 2018 at 4:59 PM Sanjay Patel <spatel at rotateright.com> wrote:

>
>
> On Tue, Oct 2, 2018 at 1:06 PM Cameron McInally <cameron.mcinally at nyu.edu>
> 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 fneg_constrained (and if we choose both, then I assume
>>> we'd also add fabs_constrained and copysign_constrained).
>>>
>>
>> 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.
>>
>
> I can't speak for anyone else, but I approve for the same reasons that
> were mentioned early on: fneg makes the intended behavior and potential
> transforms easier to discern.
>

I haven't seen any objections, so will start with this work. Thanks for the
patience, Sanjay.
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