[Mesa-dev] [PATCH 14/14] st/glsl_to_nir: enable NIR link time opts

[Ilia Mirkin]

Should this work out of the box for freedreno and vc4 as well? Or will
those need changes like radeonsi did?

On Mon, Nov 20, 2017 at 10:37 PM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> ---
>  src/mesa/state_tracker/st_glsl_to_nir.cpp | 77 +++++++++++++++++++++++++++++++
>  1 file changed, 77 insertions(+)
>
> diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
> index 27e36bd306..53e07a78e2 100644
> --- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
> +++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
> @@ -468,36 +468,107 @@ st_nir_get_mesa_program(struct gl_context *ctx,
>     NIR_PASS_V(nir, nir_lower_io_to_temporaries,
>                nir_shader_get_entrypoint(nir),
>                true, true);
>     NIR_PASS_V(nir, nir_lower_global_vars_to_local);
>     NIR_PASS_V(nir, nir_split_var_copies);
>     NIR_PASS_V(nir, nir_lower_var_copies);
>
>     return nir;
>  }
>
> +static void
> +st_nir_link_shaders(nir_shader **producer, nir_shader **consumer)
> +{
> +   nir_lower_io_arrays_to_elements(*producer, *consumer);
> +
> +   NIR_PASS_V(*producer, nir_remove_dead_variables, nir_var_shader_out);
> +   NIR_PASS_V(*consumer, nir_remove_dead_variables, nir_var_shader_in);
> +
> +   if (nir_remove_unused_varyings(*producer, *consumer)) {
> +      NIR_PASS_V(*producer, nir_lower_global_vars_to_local);
> +      NIR_PASS_V(*consumer, nir_lower_global_vars_to_local);
> +
> +      /* The backend might not be able to handle indirects on
> +       * temporaries so we need to lower indirects on any of the
> +       * varyings we have demoted here.
> +       *
> +       * TODO: radeonsi shouldn't need to do this, however LLVM isn't
> +       * currently smart enough to handle indirects without causing excess
> +       * spilling causing the gpu to hang.
> +       *
> +       * See the following thread for more details of the problem:
> +       * https://lists.freedesktop.org/archives/mesa-dev/2017-July/162106.html
> +       */
> +      nir_variable_mode indirect_mask = nir_var_local;
> +
> +      NIR_PASS_V(*producer, nir_lower_indirect_derefs, indirect_mask);
> +      NIR_PASS_V(*consumer, nir_lower_indirect_derefs, indirect_mask);
> +
> +      st_nir_opts(*producer);
> +      st_nir_opts(*consumer);
> +   }
> +}
> +
>  extern "C" {
>
>  bool
>  st_link_nir(struct gl_context *ctx,
>              struct gl_shader_program *shader_program)
>  {
>     struct st_context *st = st_context(ctx);
>
> +   /* Determine first and last stage. */
> +   unsigned first = MESA_SHADER_STAGES;
> +   unsigned last = 0;
> +   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
> +      if (!shader_program->_LinkedShaders[i])
> +         continue;
> +      if (first == MESA_SHADER_STAGES)
> +         first = i;
> +      last = i;
> +   }
> +
>     for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
>        struct gl_linked_shader *shader = shader_program->_LinkedShaders[i];
>        if (shader == NULL)
>           continue;
>
>        nir_shader *nir = st_nir_get_mesa_program(ctx, shader_program, shader);
> +
> +      nir_variable_mode mask = (nir_variable_mode) 0;
> +      if (i != first)
> +         mask = (nir_variable_mode)(mask | nir_var_shader_in);
> +
> +      if (i != last)
> +         mask = (nir_variable_mode)(mask | nir_var_shader_out);
> +
> +      nir_lower_io_to_scalar_early(nir, mask);
> +      st_nir_opts(nir);
> +   }
> +
> +   /* Linking the stages in the opposite order (from fragment to vertex)
> +    * ensures that inter-shader outputs written to in an earlier stage
> +    * are eliminated if they are (transitively) not used in a later
> +    * stage.
> +    */
> +   int next = last;
> +   for (int i = next - 1; i >= 0; i--) {
> +      struct gl_linked_shader *shader = shader_program->_LinkedShaders[i];
> +      if (shader == NULL)
> +         continue;
> +
> +      st_nir_link_shaders(&shader->Program->nir,
> +                          &shader_program->_LinkedShaders[next]->Program->nir);
> +      next = i;
>     }
>
> +   int prev = -1;
>     for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
>        struct gl_linked_shader *shader = shader_program->_LinkedShaders[i];
>        if (shader == NULL)
>           continue;
>
>        nir_shader *nir = shader->Program->nir;
>
>        /* fragment shaders may need : */
>        if (nir->info.stage == MESA_SHADER_FRAGMENT) {
>           static const gl_state_index wposTransformState[STATE_LENGTH] = {
> @@ -526,20 +597,26 @@ st_link_nir(struct gl_context *ctx,
>              _mesa_add_state_reference(shader->Program->Parameters,
>                                        wposTransformState);
>           }
>        }
>
>        NIR_PASS_V(nir, nir_lower_system_values);
>
>        nir_shader_gather_info(nir, nir_shader_get_entrypoint(nir));
>        shader->Program->info = nir->info;
>
> +      if (prev != -1) {
> +         nir_compact_varyings(shader_program->_LinkedShaders[prev]->Program->nir,
> +                              nir, ctx->API != API_OPENGL_COMPAT);
> +      }
> +      prev = i;
> +
>        st_glsl_to_nir_post_opts(st, shader->Program, shader_program);
>
>        assert(shader->Program);
>        if (!ctx->Driver.ProgramStringNotify(ctx,
>                                             _mesa_shader_stage_to_program(i),
>                                             shader->Program)) {
>           _mesa_reference_program(ctx, &shader->Program, NULL);
>           return false;
>        }
>     }
> --
> 2.14.3
>
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