[Mesa-dev] [PATCH 9/9] tgsi: add ArrayID documentation

[Christian König]

Am 14.03.2013 15:53, schrieb Christoph Bumiller:
> On 14.03.2013 15:20, Christian König wrote:
>> From: Christian König <christian.koenig at amd.com>
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   src/gallium/docs/source/tgsi.rst |   16 ++++++++++++++++
>>   1 file changed, 16 insertions(+)
>>
>> diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
>> index d9a7fe9..27fe039 100644
>> --- a/src/gallium/docs/source/tgsi.rst
>> +++ b/src/gallium/docs/source/tgsi.rst
>> @@ -1833,6 +1833,22 @@ If Interpolate flag is set to 1, a Declaration Interpolate token follows.
>>   
>>   If file is TGSI_FILE_RESOURCE, a Declaration Resource token follows.
>>   
>> +If Array flag is set to 1, a Declaration Array token follows.
>> +
>> +Array Declaration
>> +^^^^^^^^^^^^^^^^^^^^^^^^
>> +
>> +Declarations can optional have an ArrayID attribute which can be referred by
>> +indirect addressing operands. An ArrayID of zero is reserved and treaded as
>> +if no ArrayID is specified.
>> +
>> +If an indirect addressing operand refers to an specific declaration by using
> s/an/a

Thx, fixed.

>
>> +an ArrayID only the registers in this declaration are guaranteed to be
>> +accessed, accessing any register outside this declaration results in undefined
>> +behavior.
> + Note that the effective index is zero-based and not relative to the
> specified declaration. XXX: Is it ? Should it be ?

Yes for compatibility reasons, otherwise we would need to change all 
drivers at once.

>
>> +
>> +If no ArrayID is specified with an indirect addressing operand the whole
>> +register file might be accessed by this operand.
>>   
> + A practice which is strongly discouraged. Don't do this if you have
> more than 1 declaration for the file in question ! It will prevent
> packing of scalar/vec2 arrays and effective memory alias analysis.

A bit shortened, but in general added the remark.

> Packing ? Yes !
> We can pack arrays if they're declared as e.g.
> TEMP[0-3].xyzw
> TEMP[4-31].x
>
> And the caches will be very very thankful that we don't just access
> every 4th element of our 4 times larger than it needs to be buffer !!!
>
> And if your card can't do that, pleeease be nice and still make it
> possible for other drivers. :o3

It is probably possible with the new information to do so, but not 
priority for me cause I primary need it for our LLVM backend.

Christian.