[Mesa-dev] [PATCH 2/8] glsl: mark xfb varyings as always active

[Timothy Arceri]

On 23/09/17 02:59, Kenneth Graunke wrote:
> On Tuesday, September 12, 2017 4:37:29 PM PDT Timothy Arceri wrote:
>> This will be used by the nir linking pass so that we don't remove
>> otherwise unused varyings.
>> ---
>>   src/compiler/glsl/link_varyings.cpp | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
>> index 528506fd0eb..656bf79ca9d 100644
>> --- a/src/compiler/glsl/link_varyings.cpp
>> +++ b/src/compiler/glsl/link_varyings.cpp
>> @@ -2268,6 +2268,9 @@ assign_varying_locations(struct gl_context *ctx,
>>            return false;
>>         }
>>   
>> +      /* Mark xfb varyings as always active */
>> +      matched_candidate->toplevel_var->data.always_active_io = 1;
>> +
>>         if (matched_candidate->toplevel_var->data.is_unmatched_generic_inout) {
>>            matched_candidate->toplevel_var->data.is_xfb_only = 1;
>>            matches.record(matched_candidate->toplevel_var, NULL);
>>
> 
> Hmm...it looks like this could actually fix a bug today.  At least, I'm
> not seeing what code prevents us from deleting variables that are used
> for transform feedback but not otherwise.

is_xfb_only is used for that, it also has special meaning when packing 
since xfb varyings must be packed. For a nir pass is_xfb_only isn't 
really required and we can just use always_active_io instead.

> 
> Patches 1-2 are:
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
>