Am 14.11.2014 um 19:38 schrieb Henri Verbeet: > On 14 November 2014 18:50, Ilia Mirkin <imir...@alum.mit.edu> wrote: >> I can't speak for the radeon guys, but I know I sure would love to see >> any reports of poor code being generated by nouveau in response to >> legitimate-seeming TGSI (or GLSL). In some cases, a simple >> optimization can be added to take care of it, and I'd definitely >> appreciate the extra pair of eyeballs on driver-generated code :) >> >> The report can be as simple as "here is the TGSI snippet, take a look >> at how crappy the code it generates is". At least for nouveau, I can >> feed that directly into a compiler that can target any of the relevant >> backends. >> >> [Note, r600g didn't have an optimizer enabled until ~1y ago; not sure >> if your analysis was with or without sb.] >> > It was with sb, but probably before TGSI got FSLT/FSGE/etc. > > For reference, what currently happens for r600g is something like this: > > D3D: > cnd r[0], r[0].w, c[1], c[2] > > GLSL: > R0.xyzw = (R0.w > 0.5 ? ps_c[1].xyzw : ps_c[2].xyzw); > > TGSI: > FSLT TEMP[0].x, IMM[0].xxxx, TEMP[0].xxxx > UIF TEMP[0].xxxx :0 > MOV TEMP[0], CONST[1] > ELSE :0 > MOV TEMP[0], CONST[2] > ENDIF > > R600: > SETGE_DX10 T0.x, 0.5, T0.x > CNDE_INT R0.x, T0.x, KC0[1].x, KC0[2].x > CNDE_INT R0.y, T0.x, KC0[1].y, KC0[2].y > CNDE_INT R0.z, T0.x, KC0[1].z, KC0[2].z > CNDE_INT R0.w, T0.x, KC0[1].w, KC0[2].w > > While ideally that would just be 4 CNDGE's, that's better than what I > remember. IIRC there used to be a bunch of int/float conversions as > well.
That looks quite ok to me. Slightly suboptimal maybe but quite reasonable - you can't really expect "optimal" code always. (With the proposal to nuke cnd from tgsi though you'd just generate the same in any case probably.) I suspect the bunch of int/float conversions got away when switching comparison operation stuff in glsl to tgsi translation to using ints ones on hardware which supports integers (a year ago or so). I know this made some tgsi look a bit nicer but I don't know the effects this had on backends (which also probably learned some new tricks since then). _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
