[Mesa-dev] [PATCH 00/13] RadeonSI: Reduce user SGPR usage

Nicolai Hähnle nhaehnle at gmail.com
Tue Feb 20 16:46:33 UTC 2018

With a small comment on patch 6, patches 1-8:

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>

for now.

However, I'm unhappy about how complex this is all getting. 32- vs. 
64-bit, merged vs. non-merged, monolithic vs. non-monolithic, and then 
special user SGPR uses like for blits and soon VBO descriptors, it feels 
like it's becoming too much.

The problem is I don't have a good answer to it all :)

Perhaps some of it could be helped by having an explicit userdata 
staging area, i.e.

   uint32_t userdata_XX[16]; // or 32
   uint32_t userdata_XX_dirty;

Then si_upload_descriptors would write its pointers into userdata_XX in 
the right location and set the appropriate dirty bit(s), and a separate 
emit_userdata function would use the contiguous bit scan to actually 
emit all the userdata together -- this would include VS state bits, tess 
state info, and blit shader SGPRs.

I do think this would be cleaner especially than the current 
si_emit_shader_pointer_* code, and it would coalesce more SH reg writes 
as a side bonus. What do you think?

The other half of it is how the LLVM functions are created.


On 17.02.2018 20:43, Marek Olšák wrote:
> Hi,
> This series has the following effect on user SGPRs:
> 64-bit pointers:
>      TCS:    14 -> 12
>      Merged VS-TCS: 24 -> 20
>      Merged VS-GS:  18 -> 16
>      Merged TES-GS: 18 -> 14
> 32-bit pointers:
>      TCS:    10 -> 8
>      Merged VS-TCS: 16 -> 12
>      Merged VS-GS:  11 -> 9
>      Merged TES-GS: 11 -> 6
> I tested both monolithic and non-monolithic shaders, and both 64-bit
> and 32-bit pointers. (4 combinations)
> This series is a prerequisite for VBO descriptors in user SGPRs.
> Note that merged LS-HS and ES-GS don't even use s[6:7] input SGPRs
> yet. Those only provide 40 bits of scalar data (not 64 bits like
> s[0:1]).
> Please review.
> Thanks,
> Marek
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev

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Aber vergiss niemals, wie sie sein sollte.

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