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

[Nicolai Hähnle]

Nothing wrong with them, really. All the LLVM stuff has caused me to 
fall behind on going through Mesa patches, sorry for that. 9-13 are finally

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

On 25.02.2018 02:04, Marek Olšák wrote:
> So what is wrong with patches 9-13?
> 
> We can do cleanups after those.
> 
> Marek
> 
> On Thu, Feb 22, 2018 at 5:17 PM, Marek Olšák <maraeo at gmail.com> wrote:
>> I don't think that adding "uint32_t userdata_XX[16];" would simplify anything.
>>
>> The bottom line is, patches 9-13 are prerequisites for VBO descriptors
>> in user SGPRs, so they block that optimization as long as they sit on
>> the mailing list.
>>
>> Marek
>>
>> On Tue, Feb 20, 2018 at 8:51 PM, Marek Olšák <maraeo at gmail.com> wrote:
>>> The user SGPRs for blits are kinda a separate thing where the standard
>>> emit paths are disabled. 64-bit pointers are a short-term issue and
>>> will be removed in 2 years (or 1.5 years or when we want to kill off
>>> old LLVM support). VBO descriptors in user SGPRs will require 32-bit
>>> pointers. Next-gen will also require 32-bit pointers. The number of
>>> codepaths will be reduced to merged/non-merged and mono/non-mono
>>> again. For gfx9 and later, the only codepaths will be mono/non-mono.
>>>
>>> There will just be a transitory period when both 32-bit and 64-bit
>>> pointers will be supported, and both the old and new way of setting up
>>> VBO descriptors will be supported. However, next-gen will only support
>>> one way - the newer way.
>>>
>>> Overall, I don't see an increase in complexity other than the transitory period.
>>>
>>> Marek
>>>
>>> On Tue, Feb 20, 2018 at 5:46 PM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
>>>> 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.
>>>>
>>>> Thanks,
>>>> Nicolai
>>>>
>>>>
>>>> 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
>>>>>
>>>>
>>>>
>>>> --
>>>> Lerne, wie die Welt wirklich ist,
>>>> Aber vergiss niemals, wie sie sein sollte.


-- 
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.