On 04.04.2013 16:53, Zack Rusin wrote: >> 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 Did you mean signed version ? Would you mind doing an s/UCMP/ICMP in TGSI and then chaning all the UCMPs in other code to MOVC ? You're right, it would make more sense like this, though you might want to call it IMOVC so the condition register isn't interpreted as a float ... or is it supposed to be ?
> 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
