Am 03.07.2013 17:28, schrieb Jose Fonseca: > I don't fully grasp every detail (many paths), but looks good in principle. > > Where do the 16xf32 vectors come from? Those are the size vectors. Normally (except for 1d case) these contain width/height/depth/_ (or just width/height for 2d texture). So, if there's one lod and we minify width/height/depth get all minified in one step, and the sizes are then extracted from that. In the 8-wide case if there's 2 lods the minfication is done separate for both levels (because sse lacks the true vector shift) then the vectors concatenated. But now we've got (for the 8-wide case) 8 lods, hence 8 of these w/h/d/_ vectors all concatenated into one. Now ideally I guess we'd just use separate vectors but that would mean even more specialized code. Also, you have to consider even if you had a separate "width" and "height" vector, it is impossible to minify them by the lod values, it would be a buttload of scalar extraction, scalar shifts and inserts (REALLY missing the true vector shift), unless you've got AVX2 (or AMD Bulldozer) so it's probably still better to keep w/h/d/_ vectors and just hope llvm does something reaosonable with them (we hopefully shouldn't hit intrinsics as the vectors aren't really used a lot). In fact the code looks so butt ugly there for minification because needed to keep a separate path for 4-wide and 8-wide. Because if you have a w/h/d/_/w/h/d/_ vector and try to minify (right shift) by l0l0l0l0l1l1l1l1 llvm cannot separate that into 2 4-wide parts last time I checked, and that simple shift will be a mess of 16 extracts, 8 scalar shifts and 8 inserts... All that because intel forgot the real vector shift instruction before avx2, I don't think there's any other simd instruction set which lacks it.
> > Also, please add a comment somewhere summarizing all the code paths for lod > handling: > > - AVX vs non AVX > - SOA vs AOS > - scalar lod vs stamp lod Ok I'll add some more clarifying comments. Roland > > But I couldn't spot anything wrong. > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
