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

[Timothy Arceri]

On 21/11/17 15:02, Ilia Mirkin wrote:
> Should this work out of the box for freedreno and vc4 as well? Or will
> those need changes like radeonsi did?

I'm hopeful they shouldn't need any big changes as the radeonsi changes 
are due to expecting everything to be a vec4 because it code shares with 
the tgsi backend. However I have done 0 testing so any testing on those 
drivers is appreciated.


> 
> 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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