[Mesa-dev] [Mesa-stable] [PATCH] nv50/ir: skip optimizing ADD+SHL to SHLADD when src(1) is 0

[Samuel Pitoiset]

On 09/26/2017 12:29 PM, Juan A. Suarez Romero wrote:
> On Mon, 2017-05-01 at 12:11 -0400, Ilia Mirkin wrote:
>> On Mon, May 1, 2017 at 12:09 PM, Samuel Pitoiset
>> <samuel.pitoiset at gmail.com> wrote:
>>> On 05/01/2017 05:59 PM, Ilia Mirkin wrote:
>>>>
>>>> I think this is off. It shouldn't matter what the code sequence is,
>>>> it's all representable. You need to teach replaceZero to not mess
>>>> things up for SHLADD's src(1).
>>>
>>>
>>> It's representable but stupid to do it. We should keep the ADD there and
>>> this also avoids a workaround in the replaceZero logic just for that.
>>>
>>> IMHO, this is the better solution.
>>
>> Yes, that would be a better optimization. However at this stage, you
>> have a y = SHL(x, 0) + ADD(y, z). I think it makes sense to combine
>> them into one and let DCE take care of it.
>>
>> Ideally we wouldn't get into such a situation, but the real issue is
>> that a perfectly representable (if dumb) instruction like SHLADD(x, 0,
>> y) gets messed up by replaceZero. We should fix replaceZero. We should
>> also try to avoid generating such stupid instructions.
>>
> 
> So what was the final conclusion for this patch? Was replaceZero fixed?

I don't think it has been fixed, but I could be wrong.

> 
> 	J.A.
>