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[2001:470:27:11::2]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-553ac1350adsm374250e87.61.2025.06.13.01.42.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jun 2025 01:42:12 -0700 (PDT) Date: Fri, 13 Jun 2025 11:42:11 +0300 (EEST) From: =?ISO-8859-15?Q?Martin_Storsj=F6?= To: Jiawei In-Reply-To: <20250613083704.6858-1-jiawei@iscas.ac.cn> Message-ID: References: <20250613083704.6858-1-jiawei@iscas.ac.cn> MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [PATCH v5] gcc: Don't disable '-ftree-vectorize' if gcc version higher than 13. X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: ffmpeg-devel@ffmpeg.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: On Fri, 13 Jun 2025, Jiawei wrote: > This patch modifies the FFmpeg build system to allow GCC to use the > `-ftree-vectorize` flag when the compiler version is 13 or newer. > Enabling this flag can improve performance through better loop analysis > and auto-vectorization (SIMD) opportunities in modern GCC versions. > > The explicit `-fno-tree-vectorize` flag was originally added in commit > 973859f5230e (2009). A previous attempt to enable `-ftree-vectorize` > was made in commit cb8646af24bd (2016), but it was reverted in > fd6dbc53855f. The reason for the revert was that the inline x86 CABAC > assembly code caused compiler errors ??? the compiler would run out of > available registers during vectorization, making it unable to compile > some functions. > > In commit 182663a58a7a (2023), the problematic CABAC function was made > non-inline. This significantly reduces the risk of register exhaustion > caused by inlining large assembly blocks, making the vectorizer safer > to enable for other functions. > > Given improvements in GCC's vectorizer and the mitigation of the > original issue, we now re-enable `-ftree-vectorize` for GCC version 13 > and above. > > Version log: > Only allow GCC versions >= 13 to use -ftree-vectorize. > Modify the commit description. > Add historical context and rationale for the change. > > Disscussion see: > https://patchwork.ffmpeg.org/project/ffmpeg/patch/20250521061750.54882-1-jiawei@iscas.ac.cn/ > > > Signed-off-by: Jiawei > --- > configure | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) Thanks; I'm ok with this version. Whoever applies it can touch up the commit message to remove the ???? word (maybe just replace it with an "as"), it sounds reasonably right like that. // 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-request@ffmpeg.org with subject "unsubscribe".