On Tue, 30 May 2023, Martin Storsjö wrote:
Current clang versions fail to support the dotprod and i8mm features in the .arch_extension directive, but do support them if enabled with -march=armv8.4-a on the command line. (Curiously, lowering the arch level with ".arch armv8.2-a" doesn't make the extensions unavailable if they were enabled with -march; if that changes, Clang should also learn to support these extensions via .arch_extension for them to remain usable here.)
FWIW, since today, Clang does support enabling these extensions with both these extensions, see https://github.com/llvm/llvm-project/commit/4b8d9abca7d0280878fb12de331e688ee85d7cd8 and https://github.com/llvm/llvm-project/commit/4b8d9abca7d0280878fb12de331e688ee85d7cd8.
It turns out that it is possible to enable these extensions with older Clang via assembly too, but due to a bug, it would require using e.g. ".arch armv8.6-a+crc" (it requires using a "+<ext>" for any random unrelated extension). I won't try to support using that in our assembly, as the proper mechanism should be supported going forward.
As there was no further opposition, I'll push this patchset now with the last modifications that were suggested.
// Martin _______________________________________________ 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".
