[Mesa-dev] [PATCH 8/8] glsl: only divide left components when it is a dual slot double.

[Ian Romanick]

On 12/09/2015 04:07 AM, Timothy Arceri wrote:
> On Wed, 2015-12-09 at 16:06 +1000, Dave Airlie wrote:
>> From: Dave Airlie <airlied at redhat.com>
>>
>> Signed-off-by: Dave Airlie <airlied at redhat.com>
>> ---
>>  src/glsl/lower_packed_varyings.cpp | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/glsl/lower_packed_varyings.cpp
>> b/src/glsl/lower_packed_varyings.cpp
>> index 037c27d..ec9af62 100644
>> --- a/src/glsl/lower_packed_varyings.cpp
>> +++ b/src/glsl/lower_packed_varyings.cpp
>> @@ -472,7 +472,7 @@
>> lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>>        char right_swizzle_name[4] = { 0, 0, 0, 0 };
>>  
>>        left_components = 4 - fine_location % 4;
>> -      if (rvalue->type->is_double()) {
>> +      if (rvalue->type->is_dual_slot_double()) {
> 
> The subject line says what the change is but there is no explanation on
> why it was made. Can you add more detail to the comment?
> 
> To me the existing code *seems* correct as all doubles take up twice
> the amount of components, why would we only divide by 2 when its a dual
> slot double? 

Yeah... it seems like after this change it might try to pack a double in
the W component of a vec3.

>>           /* We might actually end up with 0 left components! */
>>           left_components /= 2;
>>        }
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