[Mesa-dev] [PATCH 2/3] mesa/st: use ESSL cap top enable gpu_shader5

[Ilia Mirkin]

On Thu, Mar 21, 2019 at 9:55 AM Rob Clark <robdclark at gmail.com> wrote:
>
> For GLES2+ contexts, enable EXT_gpu_shader5 if the driver exposes a
> sufficiently high ESSL feature level, even if the GLSL feature level
> isn't high enough.
>
> This allows drivers to support EXT_gpu_shader5 in GLES contexts before
> they support all the additional features of ARB_gpu_shader5 in GL
> contexts.
>
> We can also use this cap to enable ARB_ES3_1_compatibility.
>
> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
>  src/mesa/state_tracker/st_extensions.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
> index c953bfd9f7a..92450d88acf 100644
> --- a/src/mesa/state_tracker/st_extensions.c
> +++ b/src/mesa/state_tracker/st_extensions.c
> @@ -1056,6 +1056,8 @@ void st_init_extensions(struct pipe_screen *screen,
>     consts->GLSLVersionCompat =
>        screen->get_param(screen, PIPE_CAP_GLSL_FEATURE_LEVEL_COMPATIBILITY);
>
> +   const unsigned ESSLVersion =
> +      screen->get_param(screen, PIPE_CAP_ESSL_FEATURE_LEVEL);
>     const unsigned GLSLVersion =
>        api == API_OPENGL_COMPAT ? consts->GLSLVersionCompat :
>                                   consts->GLSLVersion;
> @@ -1077,6 +1079,13 @@ void st_init_extensions(struct pipe_screen *screen,
>
>     consts->AllowGLSLCrossStageInterpolationMismatch = options->allow_glsl_cross_stage_interpolation_mismatch;
>
> +   /* Technically we are turning on the EXT_gpu_shader5 extension,
> +    * ARB_gpu_shader5 does not exist in GLES, but this flag is what
> +    * switches on EXT_gpu_shader5:
> +    */
> +   if (api == API_OPENGLES2 && ESSLVersion >= 320)
> +      extensions->ARB_gpu_shader5 = GL_TRUE;
> +
>     if (GLSLVersion >= 400)
>        extensions->ARB_gpu_shader5 = GL_TRUE;
>     if (GLSLVersion >= 410)
> @@ -1539,6 +1548,9 @@ void st_init_extensions(struct pipe_screen *screen,
>        extensions->ARB_gpu_shader5 &&
>        extensions->EXT_shader_integer_mix;
>
> +   if (ESSLVersion >= 310)
> +      extensions->ARB_ES3_1_compatibility = GL__TRUE;

I'd make this also conditional on api == API_OPENGLES2 as well. This
extension nominally requires GL 4.4, and I think it'd be VERY awkward
to provide prior to GL 4.0 (which includes ARB_gpu_shader5 as a
component of it).

Sorry for leaving a bit of a mess with ARB_gpu_shader5 enablement.
It's just a _lot_ of different features, and it was daunting to add
checks for every bit of it. Looking again, I don't think the situation
has changed much. OES_gpu_shader5 is a small subset of ARB_gpu_shader5
(a lot of the bits are in core ESSL 3.10, some are in various
OES_multisample-related exts), but it's still a lot of unrelated and
annoying-to-describe things. So I think your current approach, or a
variant of it, is definitely the right way forward.

Cheers,

  -ilia


  -ilia