From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id C745043C7C for ; Wed, 27 Jul 2022 21:02:02 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id A019668B916; Thu, 28 Jul 2022 00:01:58 +0300 (EEST) Received: from mail8.parnet.fi (mail8.parnet.fi [77.234.108.134]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 411A268B677 for ; Thu, 28 Jul 2022 00:01:52 +0300 (EEST) Received: from mail9.parnet.fi (mail9.parnet.fi [77.234.108.21]) by mail8.parnet.fi with ESMTP id 26RL1oFw012417-26RL1oFx012417 for ; Thu, 28 Jul 2022 00:01:50 +0300 Received: from foo.martin.st (host-97-187.parnet.fi [77.234.97.187]) by mail9.parnet.fi (Postfix) with ESMTPS id 6AEE8A143E for ; Thu, 28 Jul 2022 00:01:49 +0300 (EEST) Date: Thu, 28 Jul 2022 00:01:49 +0300 (EEST) From: =?ISO-8859-15?Q?Martin_Storsj=F6?= To: FFmpeg development discussions and patches In-Reply-To: Message-ID: References: <05a46152f1b2458ea326edd9cfb6d817@amazon.com> MIME-Version: 1.0 X-FE-Policy-ID: 3:14:2:SYSTEM Subject: Re: [FFmpeg-devel] [PATCH] enable auto vectorization for gcc 7 and higher 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 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 Wed, 27 Jul 2022, Hendrik Leppkes wrote: > On Wed, Jul 27, 2022 at 7:39 PM James Almer wrote: >> >> On 7/27/2022 2:34 PM, Swinney, Jonathan wrote: >>> I recognize that this patch is going to be somewhat controversial. I'm submitting it mostly to see what the opinions are and evaluate options. I am working on improving performance for aarch64. On that architecture, there are fewer hand written assembly implementations of hot functions than there are for x86_64 and allowing gcc to auto-vectorize yields noticeable improvements. >>> >>> Gcc vectorization has improved recently and it hasn't been evaluated on the mailing list for a few years. This is the latest discussion I found in my searches: http://ffmpeg.org/pipermail/ffmpeg-devel/2016-May/193977.html >> >> Every time this was done, it was inevitably reverted after complains and >> crash reports started piling up because gcc can't really handle all the >> inline code our codebase has, among other things. >> > > No need to wait for issues, I just tested, and the same issues still > persist that have existed for years with GCC now. They don't seem to > care to make it compatible with inline asm, which might be fair > enough, but it means it just can't work here. > > In file included from libavcodec/cabac_functions.h:49, > from libavcodec/h264_cabac.c:36: > libavcodec/h264_cabac.c: In function 'ff_h264_decode_mb_cabac': > libavcodec/x86/cabac.h:199:5: error: 'asm' operand has impossible constraints This particular bit of inline assembly has historically been very problematic in many configurations (although primarily on i386 I think) - see e.g. 8990c5869e27fcd43b53045f87ba251f42e7d293. Would something like that be enough for that build configuration to succeed, or are there many other cases that break? // 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".