Martin Storsjö: > On Wed, 21 May 2025, Andreas Rheinhardt wrote: > >> Jiawei: >>> This patch modifies the FFmpeg build system to remove the explicit >>> disabling >>> of GCC's auto-vectorization feature. >>> >>> Modern GCC versions (>= 10.0) have demonstrated stable auto- >>> vectorization >>> capabilities through extensive optimizations in loop analysis and SIMD >>> code generation. The explicit -fno-tree-vectorize flag originally added >>> in commit 973859f (2009) to workaround early GCC vectorization >>> instability >>> is no longer necessary. >>> >>> Key improvements justifying this change: >>> 1. Enhanced heuristics for loop vectorization cost models >>> 2. Mature handling of alignment and memory access patterns >>> 3. Robust fallback mechanisms for unsupported architectures >>> >>> This change allows FFmpeg to benefit from automated SIMD optimizations >>> when built with -O3 optimization level, particularly improving >>> performance on x86_64 (AVX), ARM64 (SVE) and RISC-V(RVV) architectures. >>> >>> [1] https://git.ffmpeg.org/gitweb/ffmpeg.git/ >>> commit/973859f5230e77beea7bb59dc081870689d6d191 >>> >>> --- >>> configure | 1 - >>> 1 file changed, 1 deletion(-) >>> >>> diff --git a/configure b/configure >>> index 3730b0524c..b9e95ce4ec 100755 >>> --- a/configure >>> +++ b/configure >>> @@ -7656,7 +7656,6 @@ if enabled icc; then >>> disable aligned_stack >>> fi >>> elif enabled gcc; then >>> - check_optflags -fno-tree-vectorize >>> check_cflags -Werror=format-security >>> check_cflags -Werror=implicit-function-declaration >>> check_cflags -Werror=missing-prototypes >> >> FYI: The last discussion about auto-vectorization is here: >> https://ffmpeg.org/pipermail/ffmpeg-devel/2022-July/299405.html >> It contains a report about a failing build with vectorization enabled: >> https://ffmpeg.org/pipermail/ffmpeg-devel/2022-July/299421.html >> I don't know whether this is still reproducible with the latest GCC. > > The issue which was reported last time, when compiling for i686 mingw32 > with --cpu=haswell, seems to have gone away in > 182663a58a7a099e02e76da3b0f96d63e5c26a6d, where we made the whole > problematic x86 inline cabac assembly noinline on i386. (That whole > inline assembly block has been problematic in a large number of cases > anyway.) >
So there are currently no known miscompilations due to vectorization with GCC? - Andreas _______________________________________________ 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".
