[Mesa-dev] [PATCH 4/6] glsl/linker: don't fail non static used inputs without matching outputs

[Timothy Arceri]

On 2/2/19 10:28 am, Timothy Arceri wrote:
> 
> 
> On 2/2/19 5:05 am, Andres Gomez wrote:
>> If there is no Static Use of an input variable, the linker shouldn't
>> fail whenever there is no defined matching output variable in the
>> previous stage.
>>
>>  From page 47 (page 51 of the PDF) of the GLSL 4.60 v.5 spec:
>>
>>    " Only the input variables that are statically read need to be
>>      written by the previous stage; it is allowed to have superfluous
>>      declarations of input variables."
>>
>> Now, we complete this exception whenever the input variable has an
>> explicit location. Previously, 18004c338f6 ("glsl: fail when a
>> shader's input var has not an equivalent out var in previous") took
>> care of the cases in which the input variable didn't have an explicit
>> location.
>>
>> Additionally, likewise 1aa5738e666 ("glsl: relax input->output
>> validation for SSO programs"), avoid failing also for programs that
>> utilize GL_ARB_separate_shader_objects.
>>
>> Cc: Timothy Arceri <tarceri at itsqueeze.com>
>> Cc: Iago Toral Quiroga <itoral at igalia.com>
>> Cc: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
>> Cc: Tapani Pälli <tapani.palli at intel.com>
>> Cc: Ian Romanick <ian.d.romanick at intel.com>
>> Signed-off-by: Andres Gomez <agomez at igalia.com>
>> ---
>>   src/compiler/glsl/link_varyings.cpp | 16 ++++++++++++++--
>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/compiler/glsl/link_varyings.cpp 
>> b/src/compiler/glsl/link_varyings.cpp
>> index e5f7d3e322a..6cebc5b3c5a 100644
>> --- a/src/compiler/glsl/link_varyings.cpp
>> +++ b/src/compiler/glsl/link_varyings.cpp
>> @@ -808,8 +808,20 @@ cross_validate_outputs_to_inputs(struct 
>> gl_context *ctx,
>>                  output = 
>> output_explicit_locations[idx][input->data.location_frac].var;
>> -               if (output == NULL ||
>> -                   input->data.location != output->data.location) {
>> +               if (output == NULL) {
>> +                  /* A linker failure should only happen when, for 
>> programs
>> +                   * not using sso, there is no output declaration 
>> and there
>> +                   * is Static Use of the declared input.
>> +                   */
>> +                  if (input->data.used && !prog->SeparateShader) {
> 
> This is not really what used was designed for so it's always a bit 
> unsettling to see this type of thing.
> 
> However its better that what we do now and is consistent with 
> 18004c338f6 so this patch is:
> 
> Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

Actually I take this back after seeing Ilia's comment. I think we need 
some more piglit tests for the SSO cases where an SSO contains two or 
more stages.

> 
> 
>> +                     linker_error(prog,
>> +                                  "%s shader input `%s' with explicit 
>> location "
>> +                                  "has no matching output\n",
>> +                                  
>> _mesa_shader_stage_to_string(consumer->Stage),
>> +                                  input->name);
>> +                     break;
>> +                  }
>> +               } else if (input->data.location != 
>> output->data.location) {
>>                     linker_error(prog,
>>                                  "%s shader input `%s' with explicit 
>> location "
>>                                  "has no matching output\n",
>>
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