[Mesa-dev] [PATCH 1/4] radeonsi: correct maximum wave count per SIMD

[Marek Olšák]

On Aug 24, 2017 1:21 PM, "Nicolai Hähnle" <nhaehnle at gmail.com> wrote:

On 24.08.2017 12:34, Marek Olšák wrote:

>
>
> On Aug 24, 2017 10:17 AM, "Nicolai Hähnle" <nhaehnle at gmail.com <mailto:
> nhaehnle at gmail.com>> wrote:
>
>     On 23.08.2017 22:44, Marek Olšák wrote:
>
>         From: Marek Olšák <marek.olsak at amd.com <mailto:marek.olsak at amd.com
> >>
>
>
>         ---
>            src/gallium/drivers/radeonsi/si_shader.c | 17 ++++++++++++++++-
>            1 file changed, 16 insertions(+), 1 deletion(-)
>
>         diff --git a/src/gallium/drivers/radeonsi/si_shader.c
>         b/src/gallium/drivers/radeonsi/si_shader.c
>         index f02fc9e..186a3dd 100644
>         --- a/src/gallium/drivers/radeonsi/si_shader.c
>         +++ b/src/gallium/drivers/radeonsi/si_shader.c
>         @@ -5029,21 +5029,36 @@ static void si_shader_dump_stats(struct
>         si_screen *sscreen,
>                                           struct pipe_debug_callback
> *debug,
>                                           unsigned processor,
>                                           FILE *file,
>                                           bool check_debug_option)
>            {
>                  const struct si_shader_config *conf = &shader->config;
>                  unsigned num_inputs = shader->selector ?
>         shader->selector->info.num_inputs : 0;
>                  unsigned code_size = si_get_shader_binary_size(shader);
>                  unsigned lds_increment = sscreen->b.chip_class >= CIK ?
>         512 : 256;
>                  unsigned lds_per_wave = 0;
>         -       unsigned max_simd_waves = 10;
>         +       unsigned max_simd_waves;
>         +
>         +       switch (sscreen->b.family) {
>         +       /* SGPR initialization bug workaround on Tonga and
>         Iceland reduces
>         +        * the wave count to 8. */
>         +       case CHIP_TONGA:
>         +       case CHIP_ICELAND:
>         +       /* These always have 8 waves: */
>         +       case CHIP_POLARIS10:
>         +       case CHIP_POLARIS11:
>         +       case CHIP_POLARIS12:
>         +               max_simd_waves = 8;
>
>
>     This should be implied by the num_sgprs set by LLVM, though.
>
>
> I have no idea what you mean or why it's relevant.
>

There's this code later in the function:

        if (conf->num_sgprs) {
                if (sscreen->b.chip_class >= VI)
                        max_simd_waves = MIN2(max_simd_waves, 800 /
conf->num_sgprs);
                else
                        max_simd_waves = MIN2(max_simd_waves, 512 /
conf->num_sgprs);
        }


Yes, but that's alright. Why is it important? num_sgprs is always nonzero.




Also, what do you mean by Polaris always having 8 waves?


The closed Vulkan driver source code says that.

Marek


Cheers,
Nicolai




> Marek
>
>
>     Cheers,
>     Nicolai
>
>
>
>         +               break;
>         +       default:
>         +               max_simd_waves = 10;
>         +       }
>                  /* Compute LDS usage for PS. */
>                  switch (processor) {
>                  case PIPE_SHADER_FRAGMENT:
>                          /* The minimum usage per wave is (num_inputs *
>         48). The maximum
>                           * usage is (num_inputs * 48 * 16).
>                           * We can get anything in between and it varies
>         between waves.
>                           *
>                           * The 48 bytes per input for a single
>         primitive is equal to
>                           * 4 bytes/component * 4 components/input * 3
>         points.
>
>
>
>     --     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.
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