On 05/08/2015 03:31 PM, Ian Romanick wrote:
> On 05/08/2015 03:25 PM, Jason Ekstrand wrote:
>> On Fri, May 8, 2015 at 3:20 PM, Ian Romanick <[email protected]> wrote:
>>> On 05/08/2015 11:55 AM, Jason Ekstrand wrote:
>>>> On Fri, May 8, 2015 at 11:53 AM, Jason Ekstrand <[email protected]>
>>>> wrote:
>>>>> total instructions in shared programs: 7152330 -> 7137006 (-0.21%)
>>>>> instructions in affected programs: 1330548 -> 1315224 (-1.15%)
>>>>> helped: 5797
>>>>> HURT: 76
>>>>
>>>> I'm doing some looking into the hurt programs. It seems as if there
>>>> are some very strange interatctions between flrp and ffma. I'm still
>>>> working out exactly how to fix it up.
>>>
>>> Yes, I noticed this too. Did you see my reply to Ken earlier today?
>>> The problem I noticed /seems/ restricted to cases where the would-be
>>> interpolant is scalar but the other values are vector.
>>
>> It would surprise me a lot of that mattered. At the point where we do
>> opt_algebraic in NIR, we've already scalarized things. That said,
>> there is a *lot* going on in an optimization loop so anything's
>> possible.
>
> If I take the shader_runner test that I included in the e-mail to Ken
> and s/float alpha/vec3 alpha/ I get LRPs. I made some obvious tweaks to
> opt_algebraic to handle the mix of scalar and vector, and something like
> 150 shaders were helped.
>
> I spent about an hour digging into it, and I came up dry. I have tried
> adding some rules to nir_opt_algebraic.py to convert the fmul/ffma to
> flrp, and I couldn't get a break point at the nir_opt_ffma to trigger.
> I was going to ask about it at the office on Monday, but it came up on
> the list first.
FWIW, those rules were:
(('ffma', b, c, ('fmul', a, ('fadd', 1.0, ('fneg', c)))), ('flrp', a, b, c),
'!options->lower_flrp'),
(('ffma', c, b, ('fmul', a, ('fadd', 1.0, ('fneg', c)))), ('flrp', a, b, c),
'!options->lower_flrp'),
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