[Mesa-dev] mesa/st: support lowering user-clip-planes automatically

[Rob Clark]

hmm, initially the UCP lowering did work post var lowering (since it
had work after tgsi_to_nir).. the same might not be true of the
drawpix/wpos_ytransform/etc lowering that is used internally in
mesa/st for variants.

I assume something like this is the issue?

BR,
-R

On Fri, Oct 18, 2019 at 3:24 PM Marek Olšák <maraeo at gmail.com> wrote:
>
> Oh BTW, drivers that want to implement pipe_screen::finalize_nir to improve cached shader compilation can't use any of those lowering passes, because then things blow up. The only _optional_ lowering you can do in st/mesa is clamp_color and force_persample_in_shader, which covers iris at least (radeonsi doesn't need any). If you need more, you either need to invest a significant amount of time to make driver-specific NIR work with the lowering passes, or give up on good shader cache efficiency.
>
> Marek
>
> On Fri, Oct 18, 2019 at 4:17 PM Marek Olšák <maraeo at gmail.com> wrote:
>>
>> Note that none of the lowering passes work if I enable them on radeonsi. So if you think about enabling them for your driver, I guess you have some work to do in the driver as well.
>>
>> On the other hand, having multiple shader variants in st/mesa is a performance disadvantage. The lowering should be done at the machine-level assembly code, so that you don't have to completely recompile from a higher-level IR.
>>
>> Marek
>>
>> On Fri, Oct 18, 2019 at 4:08 PM Marek Olšák <maraeo at gmail.com> wrote:
>>>
>>> On Fri, Oct 18, 2019 at 9:07 AM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>>>
>>>> On Fri, Oct 18, 2019 at 9:04 AM Erik Faye-Lund
>>>> <erik.faye-lund at collabora.com> wrote:
>>>> >
>>>> > On Fri, 2019-10-18 at 08:57 -0400, Ilia Mirkin wrote:
>>>> > > On Fri, Oct 18, 2019 at 8:51 AM Erik Faye-Lund
>>>> > > <erik.faye-lund at collabora.com> wrote:
>>>> > > > On Thu, 2019-10-17 at 22:24 -0400, Ilia Mirkin wrote:
>>>> > > > > In the meanwhile (unless you plan on taking up Jason's
>>>> > > > > suggestion),
>>>> > > > > might I recommend some assert's for the unhandled cases so that
>>>> > > > > there
>>>> > > > > are no surprises?
>>>> > > >
>>>> > > > Good idea. I sent a MR for it here:
>>>> > > >
>>>> > > > https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2380
>>>> > >
>>>> > > Not sure that approach works, esp with SSO.
>>>> >
>>>> > If so, wouldn't that already be a problem with the existing
>>>> > lower_depth_clamp-stuff, then? I mean, I just lifted the logic from
>>>> > there...
>>>>
>>>> Yeah, that looks bogus. I'm moderately sure that checking
>>>> "st->vp/gp/tep" at LinkShader time is wrong. Marek can probably
>>>> confirm.
>>>
>>>
>>> Don't read any context states at link time. It's wrong.
>>>
>>> Marek
>
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