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

[Timothy Arceri]

On 03/07/17 10:46, Timothy Arceri wrote:
> 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.

Well maybe not disable, but surely we could ignore it.

> 
> 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;
>>   }
>>
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