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

[Christoph Bumiller]

On 15.03.2013 13:08, Christian König wrote:
> 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.
>
At some point you'll be able to make use of the info in your backend,
too, and then you'll regret having to refamiliarize with this code just
because you didn't add the extra (estimated) 2 lines to set the UsageMask.

Also, NAK from me until array access/declarations for the other files
follows suit.
Sorry for being so ... pesky, but I'd really like this change to be 100%
complete. Come on, doesn't it nag on your conscience if this is left to
remain only a few smalls steps from perfection ?

> Christian.