[Mesa-dev] GLSL IR int-to-float pass

Jerome Glisse j.glisse at gmail.com
Wed May 25 10:48:40 PDT 2011

On Wed, May 25, 2011 at 9:41 AM, Keith Whitwell <keithw at vmware.com> wrote:
> On Wed, 2011-05-25 at 09:32 -0400, Jerome Glisse wrote:
>> On Tue, May 24, 2011 at 8:09 PM, Bryan Cain <bryancain3 at gmail.com> wrote:
>> > Hi,
>> >
>> > In the past few days, I've been working on native integer support in my
>> > GLSL to TGSI translator.  Something that's come to my attention is that
>> > supporting Gallium targets with and without integer support using a
>> > single GLSL IR backend will more or less require a GLSL IR pass to
>> > convert int, uint, and possibly bool variables and operations to floats.
>> >
>> > Currently, this is done directly in the backend, in both ir_to_mesa and
>> > st_glsl_to_tgsi.  However, the mod_to_fract and div_to_mul_rcp lowering
>> > passes for GLSL IR need to know whether to lower integer modulus and
>> > division operations to their corresponding float operations.  (They both
>> > do this in Mesa master without asking the backend, but that will be easy
>> > to change later.)  So a GLSL IR pass will be needed to do the type lowering.
>> >
>> > Such a pass would also have the advantage of less duplicated
>> > functionality between backends, since ir_to_mesa could also take
>> > advantage of the pass to eliminate some code.
>> >
>> > I'm more than willing to try writing such a pass myself if no one else
>> > is interested in doing it, but I figure I should make sure there are no
>> > objections before starting on it.
>> >
>> > Bryan
>> TGSI needs to grow type support (int, uint and possibly int8,16,32..)
> Or go away entirely...
> I'm not trying to impose a direction on this, but it seems like the GLSL
> IR->TGSI converter (once running) could be pushed down into the
> individual drivers and GLSL IR or a close cousin of it could become the
> gallium-level interface.  Then individual drivers could be modified to
> consume IR directly.
> Keith

I am also in favor of getting rid of tgsi, i would prefer having the
driver callback into mesa to set informations mesa needs from the
shader, for instance that would allow driver to pick where they put
attribute (might be a huge win on hw like r6xx or newer) and few
others things like that.


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