[Mesa-dev] TGSI thoughts

[Keith Whitwell]

On Wed, 2010-07-28 at 01:00 -0700, Jakob Bornecrantz wrote:
> On Tue, Jul 27, 2010 at 10:25 PM, Zack Rusin <zackr at vmware.com> wrote:
> > On Tuesday 27 July 2010 23:57:17 Jakob Bornecrantz wrote:
> >> First off, the Core TGSI instruction set includes a lot of
> >> instructions that not necessary all hardware can handle foremost off
> >> these are DDX and DDY which should either be moved to the GLSL cap or
> >> get a cap of its own. Related to this is IF and friends, tho this can
> >> be handled by a compiler or optimizer but sometimes this might be
> >> better to tell the higher levels about it so maybe a cap or some sort
> >> of cap hint? And while on branching instructions the CAL and RET
> >> opcodes could also do with the same treatment.
> >
> > We already have PIPE_CAP_GLSL. Or are you saying that you'd like to keep
> > support for GLSL but not for those features? Personally I don't think that
> > would make a lot of sense (you'll never be able to pass actual conformance on
> > anything like that).
> 
> What I was trying to say is that at least according to the docs all
> these instructions are in the Core TGSI set and must be available in
> all drivers. Obviously they are not, especially DDX and DDY which are
> quite magical.


There's nothing magical about them at all.  They're fundamental to
advanced texturing and have been part of D3D since PS2.x and are present
in GLSL 1.0 and probably all the post-ARB_fp assembly extensions.

The i915 is a PS2.0 (barely) part, which is why you're not used to
seeing them.

At a guess, it sounds like these should be listed under CAP_GLSL and
CAP_SM3 (as we don't care much about 2.x).

Keith