ffmpeg | branch: master | Rémi Denis-Courmont <r...@remlab.net> | Sat May 11 17:26:14 2024 +0300| [0e32192548cd38a206ef3ed3c0ad8edc337a1e5f] | committer: Rémi Denis-Courmont
lavu/riscv: do not fallback to AT_HWCAP auxillary vector If __riscv_hwprobe() fails, then the kernel version is presumably too old. There is not much point falling back to the auxillary vector. - The Linux kernel requires I, so the flag is always set on Linux, and run-time detection is unnecessary. Our RISC-V assembler does anyway not support targets without I. - Linux can compile with or without F and D, but it cannot perform run-time detection for them (a kernel with F support will not boot a processor without F). The run-time detection is thus useless in that case. Besides F and D extensions are used throughout the C code, so their run-time detection would not be practical. - Support for V was added in a later kernel version than riscv_hwprobe(), so the system call will always be available if the kernel supports V. The only exception would be vendor kernel forks, but those are known to haphasardly pretend to support V on systems without actual V support, or with only pre-ratification binary-incompatible version. Furthermore, a large chunk of our optimisations require Zba and/or Zbb which cannot be detected with HWCAP in those kernels. For what it is worth, OpenJDK already took a similar action. Note that this keeps AT_HWCAP usage for platforms with neither C run-time <sys/hwprobe.h> nor kernel <asm/hwprobe.h>, notably kernels other than Linux. > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0e32192548cd38a206ef3ed3c0ad8edc337a1e5f --- libavutil/riscv/cpu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/libavutil/riscv/cpu.c b/libavutil/riscv/cpu.c index 73abd289a6..04ac404bbf 100644 --- a/libavutil/riscv/cpu.c +++ b/libavutil/riscv/cpu.c @@ -83,9 +83,8 @@ int ff_get_cpu_flags_riscv(void) break; default: } - } else -#endif -#if HAVE_GETAUXVAL + } +#elif HAVE_GETAUXVAL { const unsigned long hwcap = getauxval(AT_HWCAP); _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog To unsubscribe, visit link above, or email ffmpeg-cvslog-requ...@ffmpeg.org with subject "unsubscribe".
