[Nouveau] Dealing with opencl kernel parameters in nouveau now that RES support is gone

[Hans de Goede]

Hi,

On 22-02-16 13:41, Samuel Pitoiset wrote:
> Hi there,
>
> On 02/22/2016 12:26 PM, Hans de Goede wrote:

<snip>

>> So back to the problem of getting OpenCL(ish) code to work again with
>> the recent mesa changes. For starters I would like to get:
>>
>> src/gallium/tests/trivial/compute.c and then the test with mask 8,
>> test_input_global() to work again, when that is working I should be
>> able to adjust my llvm work (and if necessary clover) to start to
>> work again.
>>
>> Currently the test_input_global() test uses the following bit of
>> TGSI code:
>>
>> COMP
>> DCL SV[0], THREAD_ID[0]
>> DCL TEMP[0], LOCAL
>> DCL TEMP[1], LOCAL
>> IMM UINT32 { 8, 0, 0, 0 }
>>
>>     BGNSUB\n"
>>         UMUL TEMP[0], SV[0], IMM[0]
>>         LOAD TEMP[1].xy, RINPUT, TEMP[0]
>>         LOAD TEMP[0].x, RGLOBAL, TEMP[1].yyyy
>>         UADD TEMP[1].x, TEMP[0], -TEMP[1]
>>         STORE RGLOBAL.x, TEMP[1].yyyy, TEMP[1]
>>         RET
>>     ENDSUB
>>
>>
>> Where by RINPUT and RGLOBAL get replaces by processing the
>> code with cpp and the following defines:
>>
>> #define RGLOBAL        RES[32767]
>> #define RLOCAL         RES[32766]
>> #define RPRIVATE       RES[32765]
>> #define RINPUT         RES[32764]
>>
>> If I understand how memory is supposed to work, then I would need to
>> change the TGSI as follows:
>>
>> COMP
>> DCL SV[0], THREAD_ID[0]
>> DCL MEMORY[0]
>> DCL TEMP[0], LOCAL
>> DCL TEMP[1], LOCAL
>> IMM UINT32 { 8, 0, 0, 0 }
>>
>> BGNSUB\n"
>> UMUL TEMP[0], SV[0], IMM[0]
>> LOAD TEMP[1].xy, RINPUT, TEMP[0]
>> LOAD TEMP[0].x, MEMORY[0], TEMP[1].yyyy
>> UADD TEMP[1].x, TEMP[0], -TEMP[1]
>> STORE MEMORY[0].x, TEMP[1].yyyy, TEMP[1]
>> RET
>> ENDSUB
>
> Nope, this won't work because RINPUT is RES[32764]. And you have to remove all occurrences to RES because it's not longer supported. In my opinion, using BUFFER[0] in a first time should work. Currently, only SHARED with MEMORY is supported.

Right, as I say below "This only solves the accessing of the global memory, it does not solve
getting to the kernel input kernel parameters"

>> This assumes, that as discussed declaring memory without a , SHARED or
>> other
>> flag means the memory is global.
>>
>> So 2 questions:
>>
>> 1) Do the above changes for using the new MEMORY keyword look as intended
>> to you?
>>
>> 2) This only solves the accessing of the global memory, it does not solve
>> getting to the kernel input kernel parameters, how would I deal with
>> those ?
>
> The input kernel parameters are directly passed through a call to pipe_context::launch_grid. You just have to fill the pipe_grid_info::input array with your parameters and they will be uploaded by nvXX_compute_upload_input().

Right, the uploading side I understand, the question is how to get to them from
the compute kernel's tgsi code ?

If I understand you correctly you are suggesting to use BUFFER[0] for this,
that is fine from a nouveau point-of-view, but might be a bit nouveau
centric way of looking at things, I think a better approach would be
a separate input register-file for this, as that will be more flexible
when people try to do opencl via clang->llvm->tgsi on other GPUs.

> I will have a look at the test_input_global().

Thanks!

Regards,

Hans