[Mesa-dev] [PATCH 06/92] nir/lower_system_values: add support for the FRAG_COORD system value

[Timothy Arceri]

This and the previous patch seem a bit hacky to me. It seems it would be 
better to either plum the system value all the way through NIR for all 
drivers or simply disable GLSLFragCoordIsSysVal when radeonsi is going 
to be using the NIR path.

On 27/06/17 00:09, Nicolai Hähnle wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
> 
> Arguably this could convert to a load intrinsic, but other code paths
> already expect this as a fragment shader input.
> ---
>   src/compiler/nir/nir_lower_system_values.c | 36 ++++++++++++++++++++++++++----
>   1 file changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/src/compiler/nir/nir_lower_system_values.c b/src/compiler/nir/nir_lower_system_values.c
> index 810100a..64a1354 100644
> --- a/src/compiler/nir/nir_lower_system_values.c
> +++ b/src/compiler/nir/nir_lower_system_values.c
> @@ -21,22 +21,46 @@
>    * IN THE SOFTWARE.
>    *
>    * Authors:
>    *    Connor Abbott (cwabbott0 at gmail.com)
>    *
>    */
>   
>   #include "nir.h"
>   #include "nir_builder.h"
>   
> +static nir_ssa_def *
> +get_frag_coord(nir_builder *b, nir_shader *shader, nir_variable *orig)
> +{
> +   nir_variable *pos = NULL;
> +
> +   assert(shader->stage == MESA_SHADER_FRAGMENT);
> +
> +   nir_foreach_variable(var, &shader->inputs) {
> +      if (var->data.location == VARYING_SLOT_POS) {
> +         pos = var;
> +         break;
> +      }
> +   }
> +
> +   if (!pos) {
> +      pos = nir_variable_create(shader, nir_var_shader_in, glsl_vec4_type(), "gl_FragCoord");
> +      pos->data.location = VARYING_SLOT_POS;
> +      pos->data.pixel_center_integer = orig->data.pixel_center_integer;
> +      pos->data.origin_upper_left = orig->data.origin_upper_left;
> +   }
> +
> +   return nir_load_var(b, pos);
> +}
> +
>   static bool
> -convert_block(nir_block *block, nir_builder *b)
> +convert_block(nir_block *block, nir_builder *b, nir_shader *shader)
>   {
>      bool progress = false;
>   
>      nir_foreach_instr_safe(instr, block) {
>         if (instr->type != nir_instr_type_intrinsic)
>            continue;
>   
>         nir_intrinsic_instr *load_var = nir_instr_as_intrinsic(instr);
>   
>         if (load_var->intrinsic != nir_intrinsic_load_var)
> @@ -109,59 +133,63 @@ convert_block(nir_block *block, nir_builder *b)
>               sysval = nir_load_vertex_id(b);
>            }
>            break;
>   
>         case SYSTEM_VALUE_INSTANCE_INDEX:
>            sysval = nir_iadd(b,
>                              nir_load_instance_id(b),
>                              nir_load_base_instance(b));
>            break;
>   
> +      case SYSTEM_VALUE_FRAG_COORD:
> +         sysval = get_frag_coord(b, shader, var);
> +         break;
> +
>         default:
>            break;
>         }
>   
>         if (sysval == NULL) {
>            nir_intrinsic_op sysval_op =
>               nir_intrinsic_from_system_value(var->data.location);
>            sysval = nir_load_system_value(b, sysval_op, 0);
>         }
>   
>         nir_ssa_def_rewrite_uses(&load_var->dest.ssa, nir_src_for_ssa(sysval));
>         nir_instr_remove(&load_var->instr);
>   
>         progress = true;
>      }
>   
>      return progress;
>   }
>   
>   static bool
> -convert_impl(nir_function_impl *impl)
> +convert_impl(nir_function_impl *impl, nir_shader *shader)
>   {
>      bool progress = false;
>      nir_builder builder;
>      nir_builder_init(&builder, impl);
>   
>      nir_foreach_block(block, impl) {
> -      progress |= convert_block(block, &builder);
> +      progress |= convert_block(block, &builder, shader);
>      }
>   
>      nir_metadata_preserve(impl, nir_metadata_block_index |
>                                  nir_metadata_dominance);
>      return progress;
>   }
>   
>   bool
>   nir_lower_system_values(nir_shader *shader)
>   {
>      bool progress = false;
>   
>      nir_foreach_function(function, shader) {
>         if (function->impl)
> -         progress = convert_impl(function->impl) || progress;
> +         progress = convert_impl(function->impl, shader) || progress;
>      }
>   
>      exec_list_make_empty(&shader->system_values);
>   
>      return progress;
>   }
>