[Mesa-dev] [PATCH] nir/search: Save/restore the variables_seen bitmask when matching

[Ian Romanick]

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 <idr at freedesktop.org> wrote:
>>> On 05/08/2015 11:55 AM, Jason Ekstrand wrote:
>>>> On Fri, May 8, 2015 at 11:53 AM, Jason Ekstrand <jason at jlekstrand.net> 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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