On Mon, Jul 3, 2023 at 1:00 AM Rémi Denis-Courmont <r...@remlab.net> wrote: > > Hi, > > The diff is ok. I even have a slight incline in favour thereof for the sake > of consistency. Yet, I may be vainly pedantic but I do have problems with the > description. > > Le 3 juillet 2023 05:44:12 GMT+03:00, Khem Raj <raj.k...@gmail.com> a écrit : > >Add missing operand > > The spec does explicitly make the mask and tail policy mandatory, but I can't > see any such requirements for the group multiplier. To the contrary, there > are several examples in the spec _without_ explicit multiplier. > > In reality, `vsetvli` (and `vsetivli`) merely transfers an immediate value to > the vector configuration register. Missing fields are to be left at zero for > forward compatibility, and `m1` happens to encode as 0b000. >
I just replicated what GAS is doing here implicitly. > > Which clang complains about but gcc assumes it to be > >'m1' if not specifiied. > > The technical term for the RISC-V support in LLVM AS version 15 and earlier > is "useless junk". If you want to compile FFmpeg on RISC-V with Clang, you > *must* disable the integrated AS and use binutils GNU/as instead. > > The Linux RISC-V kernel altogether gave up on LLVM entirely, requiring GCC > for RVV, so they're even stricter (and without kernel support, FFmpeg support > is obviously useless). > > *Hopefully* LLVM gets their act together by release 16, and ship a usable > assembler, rather than tell us to use automatic RVV vectorisation (which *is* > a release 16 feature, though it was half-baked last time I tried). > I am on clang/llvm trunk ( future 17.0 release ), I will also open an issue with llvm on github regarding this. > > > >Fixes building with clang > > More like bug-compatible work-around than fix, AFAIU. I can do it although I did not find a relevant section in spec about these being optional, I did see examples omitting them though. > > >| src/libswscale/riscv/rgb2rgb_rvv.S:88:25: error: operand must be > >e[8|16|32|64|128|256|512|1024],m[1|2|4|8|f2|f4|f8],[ta|tu],[ma|mu] > > Do you have a reference to the Github RVV spec to validate this, that I > overlooked, or it's just misled and misleading spew from LLVM? Perhaps the latter but I also did not see reference to the former. Here is a small example a.S #.option arch, +zve32x # OK #vsetvli t4, t3, e8, m1, ta, ma # BAD vsetvli t4, t3, e8, ta, ma clang -target riscv64 -march=rv64izve32x1p0 a.S -c > > >| vsetvli t4, t3, e8, ta, ma > >| ^ > > > >Signed-off-by: Khem Raj <raj.k...@gmail.com> > >--- > > libswscale/riscv/rgb2rgb_rvv.S | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > >diff --git a/libswscale/riscv/rgb2rgb_rvv.S b/libswscale/riscv/rgb2rgb_rvv.S > >index 5626d906eb..bbdfdbebbc 100644 > >--- a/libswscale/riscv/rgb2rgb_rvv.S > >+++ b/libswscale/riscv/rgb2rgb_rvv.S > >@@ -85,7 +85,7 @@ func ff_interleave_bytes_rvv, zve32x > > mv t3, a3 > > addi a4, a4, -1 > > 2: > >- vsetvli t4, t3, e8, ta, ma > >+ vsetvli t4, t3, e8, m1, ta, ma > > sub t3, t3, t4 > > vle8.v v8, (t0) > > add t0, t4, t0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
