[Mesa-stable] [Mesa-dev] [PATCH] glsl/linker: Link all out vars from a shader objects on a single stage

[Timothy Arceri]

On 30/08/18 08:16, Andres Gomez wrote:
> Vadym, should we also include this in the stable queues ?
> 

Yes. It should be fine to add this to stable. Thanks.

> On Mon, 2018-08-27 at 15:20 +0300, Vadym Shovkoplias wrote:
>> From: "vadym.shovkoplias" <vadym.shovkoplias at globallogic.com>
>>
>> During intra stage linking some out variables can be dropped because
>> it is not used in a shader with the main function. But these out vars
>> can be referenced on later stages which can lead to further linking
>> errors.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105731
>> Signed-off-by: Vadym Shovkoplias <vadym.shovkoplias at globallogic.com>
>> ---
>>   src/compiler/glsl/linker.cpp | 38 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>
>> diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
>> index 3ce78fe642..3b0c01c316 100644
>> --- a/src/compiler/glsl/linker.cpp
>> +++ b/src/compiler/glsl/linker.cpp
>> @@ -2187,6 +2187,41 @@ link_cs_input_layout_qualifiers(struct gl_shader_program *prog,
>>      }
>>   }
>>   
>> +/**
>> + * Link all out variables on a single stage which are not
>> + * directly used in a shader with the main function.
>> + */
>> +static void
>> +link_output_variables(struct gl_linked_shader *linked_shader,
>> +                      struct gl_shader **shader_list,
>> +                      unsigned num_shaders)
>> +{
>> +   struct glsl_symbol_table *symbols = linked_shader->symbols;
>> +
>> +   for (unsigned i = 0; i < num_shaders; i++) {
>> +
>> +      /* Skip shader object with main function */
>> +      if (shader_list[i]->symbols->get_function("main"))
>> +         continue;
>> +
>> +      foreach_in_list (ir_instruction, ir, shader_list[i]->ir) {
>> +
>> +         if (ir->ir_type != ir_type_variable)
>> +            continue;
>> +
>> +         ir_variable *const var = (ir_variable *) ir;
>> +
>> +         if (var->data.mode == ir_var_shader_out &&
>> +               !symbols->get_variable(var->name)) {
>> +            symbols->add_variable(var);
>> +            linked_shader->ir->push_head(var);
>> +         }
>> +      }
>> +   }
>> +
>> +   return;
>> +}
>> +
>>   
>>   /**
>>    * Combine a group of shaders for a single stage to generate a linked shader
>> @@ -2352,6 +2387,9 @@ link_intrastage_shaders(void *mem_ctx,
>>         return NULL;
>>      }
>>   
>> +   if (linked->Stage != MESA_SHADER_FRAGMENT)
>> +      link_output_variables(linked, shader_list, num_shaders);
>> +
>>      /* Make a pass over all variable declarations to ensure that arrays with
>>       * unspecified sizes have a size specified.  The size is inferred from the
>>       * max_array_access field.