[Mesa-dev] [PATCH 1/2] mesa: remove redundant modulus operation

[Timothy Arceri]

On 24/05/17 08:07, Ian Romanick wrote:
> On 05/23/2017 05:01 AM, Timothy Arceri wrote:
>> The if check above means we can only get here if size is less than 4.
>> ---
>>   src/mesa/program/prog_parameter.c | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/src/mesa/program/prog_parameter.c b/src/mesa/program/prog_parameter.c
>> index 44e680c..40bc47d 100644
>> --- a/src/mesa/program/prog_parameter.c
>> +++ b/src/mesa/program/prog_parameter.c
>> @@ -260,23 +260,22 @@ _mesa_add_parameter(struct gl_program_parameter_list *paramList,
>>         struct gl_program_parameter *p = paramList->Parameters + oldNum + i;
>>         p->Name = strdup(name ? name : "");
>>         p->Type = type;
>>         p->Size = size;
>>         p->DataType = datatype;
>>         if (values) {
>>            if (size >= 4) {
>>               COPY_4V(paramList->ParameterValues[oldNum + i], values);
>>            } else {
>>               /* copy 1, 2 or 3 values */
>> -            GLuint remaining = size % 4;
>> -            assert(remaining < 4);
>> -            for (j = 0; j < remaining; j++) {
>> +            assert(size < 4);
>> +            for (j = 0; j < size; j++) {
>>                  paramList->ParameterValues[oldNum + i][j].f = values[j].f;
>>               }
>>               /* fill in remaining positions with zeros */
>>               for (; j < 4; j++) {
>>                  paramList->ParameterValues[oldNum + i][j].f = 0.0f;
>>               }
> 
> It might be interesting to see if just setting all four values to 0.0
> before the copy produces better code.  There are a bunch of different
> micro optimizations possible depending on what GCC does.

I've actually been looking at whether we can stop allocating 4 
components here by default. I think it should be ok to do, state 
references always pass a size of 4 as do uniforms from asm. This would 
allow us to allocate the actual size we need for glsl uniforms.

It looks like i965 already skips these excess components and assigns a 
pointer to static consts zero instead. Seems the gallium change should 
be simple enough, i915 looks like it could be a little more tricky.

> 
> Either way, this patch is
> 
> Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
> 
>>            }
>>            values += 4;
>>         } else {
>>            /* silence valgrind */
>>
>