[Mesa-dev] [PATCH 3/3] glsl/linker: Adapt flat varying handling in preparation for geometry shaders.

[Paul Berry]

On 8 April 2013 10:57, Ian Romanick <idr at freedesktop.org> wrote:

> On 04/06/2013 07:49 PM, Paul Berry wrote:
>
>> When a varying is consumed by transform feedback, but is not used by
>> the fragment shader, assign_varying_locations() sets its interpolation
>> type to "flat" in order to ensure that lower_packed_varyings never has
>> to deal with non-flat integral varyings (the GLSL spec doesn't require
>> integral vertex outputs to be flat if they aren't consumed by the
>> fragment shader).
>>
>> A similar situation will arise when geometry shader support is added,
>> since the GLSL spec only requires integral vertex shader outputs to be
>> flat when they are consumed by the geometry shader.  This patch
>>
>                                      ^^^^^^^^
> fragment?


Oops, yes.  Thanks.


>
>
>  modifies the linker to handle this situation too.
>> ---
>>   src/glsl/link_varyings.cpp | 30 ++++++++++++++++++++----------
>>   1 file changed, 20 insertions(+), 10 deletions(-)
>>
>> diff --git a/src/glsl/link_varyings.cpp b/src/glsl/link_varyings.cpp
>> index 431d8fd..7e90beb 100644
>> --- a/src/glsl/link_varyings.cpp
>> +++ b/src/glsl/link_varyings.cpp
>> @@ -541,7 +541,7 @@ store_tfeedback_info(struct gl_context *ctx, struct
>> gl_shader_program *prog,
>>   class varying_matches
>>   {
>>   public:
>> -   varying_matches(bool disable_varying_packing);
>> +   varying_matches(bool disable_varying_packing, bool consumer_is_fs);
>>      ~varying_matches();
>>      void record(ir_variable *producer_var, ir_variable *consumer_var);
>>      unsigned assign_locations();
>> @@ -621,11 +621,15 @@ private:
>>       * it was allocated.
>>       */
>>      unsigned matches_capacity;
>> +
>> +   const bool consumer_is_fs;
>>   };
>>
>>
>> -varying_matches::varying_**matches(bool disable_varying_packing)
>> -   : disable_varying_packing(**disable_varying_packing)
>> +varying_matches::varying_**matches(bool disable_varying_packing,
>> +                                 bool consumer_is_fs)
>> +   : disable_varying_packing(**disable_varying_packing),
>> +     consumer_is_fs(consumer_is_fs)
>>   {
>>      /* Note: this initial capacity is rather arbitrarily chosen to be
>> large
>>       * enough for many cases without wasting an unreasonable amount of
>> space.
>> @@ -672,12 +676,12 @@ varying_matches::record(ir_**variable
>> *producer_var, ir_variable *consumer_var)
>>         return;
>>      }
>>
>> -   if (consumer_var == NULL) {
>> -      /* Since there is no consumer_var, the interpolation type of this
>> -       * varying cannot possibly affect rendering.  Also, since the GL
>> spec
>> -       * only requires integer varyings to be "flat" when they are
>> fragment
>> -       * shader inputs, it is possible that this variable is non-flat
>> and is
>> -       * (or contains) an integer.
>> +   if (consumer_var == NULL || !consumer_is_fs) {
>> +      /* Since this varying is not being consumed by the fragment
>> shader, its
>> +       * interpolation type varying cannot possibly affect rendering.
>>  Also,
>> +       * since the GL spec only requires integer varyings to be "flat"
>> when
>> +       * they are fragment shader inputs, it is possible that this
>> variable is
>> +       * non-flat and is (or contains) an integer.
>>          *
>>          * lower_packed_varyings requires all integer varyings to flat,
>>          * regardless of where they appear.  We can trivially satisfy that
>> @@ -685,6 +689,11 @@ varying_matches::record(ir_**variable
>> *producer_var, ir_variable *consumer_var)
>>          */
>>         producer_var->centroid = false;
>>         producer_var->interpolation = INTERP_QUALIFIER_FLAT;
>> +
>> +      if (consumer_var) {
>> +         consumer_var->centroid = false;
>> +         consumer_var->interpolation = INTERP_QUALIFIER_FLAT;
>> +      }
>>      }
>>
>>      if (this->num_matches == this->matches_capacity) {
>> @@ -979,7 +988,8 @@ assign_varying_locations(**struct gl_context *ctx,
>>   {
>>      const unsigned producer_base = VARYING_SLOT_VAR0;
>>      const unsigned consumer_base = VARYING_SLOT_VAR0;
>> -   varying_matches matches(ctx->Const.**DisableVaryingPacking);
>> +   varying_matches matches(ctx->Const.**DisableVaryingPacking,
>> +                           consumer && consumer->Type ==
>> GL_FRAGMENT_SHADER);
>>      hash_table *tfeedback_candidates
>>         = hash_table_ctor(0, hash_table_string_hash,
>> hash_table_string_compare);
>>      hash_table *consumer_inputs
>>
>>
>
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