> On 04.04.2013 03:45, Zack Rusin wrote: > > It's part of SM4 (http://goo.gl/4IpeK). It's also fairly > > painful to emulate without branching. Most hardware > > supports it natively and even llvm has a 'select' opcode > > which can handle it without too much hassle. > > > > diff --git a/src/gallium/docs/source/tgsi.rst > > b/src/gallium/docs/source/tgsi.rst > > index 28308cb..6c5a02b 100644 > > --- a/src/gallium/docs/source/tgsi.rst > > +++ b/src/gallium/docs/source/tgsi.rst > > @@ -72,6 +72,17 @@ used. > > > > dst.w = src.w > > > > +.. opcode:: MOVC - Conditional move > > + > > +.. math:: > > + > > + dst.x = src0.x ? src1.x : src2.x > > + > > + dst.y = src0.y ? src1.y : src2.y > > + > > + dst.z = src0.z ? src1.z : src2.z > > + > > + dst.w = src0.w ? src1.w : src2.w > > > > I think we already have that: > > .. opcode:: UCMP - Integer Conditional Move > > .. math:: > > dst.x = src0.x ? src1.x : src2.x > > dst.y = src0.y ? src1.y : src2.y > > dst.z = src0.z ? src1.z : src2.z > > dst.w = src0.w ? src1.w : src2.w > > > No difference apart from the source ordering (the "integer" just implies > that any non-zero value counts as true, i.e. also inf, nan and -0).
That's really broken. UCMP needs to be a an unsigned version of the CMP instruction which does dst.chan = (src0.chan < 0) ? src1.chan : src2.chan not a whole new instruction. It's what everyone implements anyway. So if st_glsl_to_tgsi needs a conditional move we need to add the above patch and change it to use it. > And if you want more conditional ops, in theory we also have > predication, albeit support for that depends on the driver > (PIPE_SHADER_CAP_MAX_PREDS). No, that's a completely different thing. z _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
