https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69320
Bug ID: 69320
Summary: wrong code generation at -O2 and higher
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamrial at gmail dot com
Target Milestone: ---
Created attachment 37377
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37377&action=edit
Assembly and preprocessed output of miscompiled file
http://fate.ffmpeg.org/report.cgi?time=20160116195307&slot=x86_64-archlinux-gcc-experimental
https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/svq1enc.c;h=1e1745e7b10ed24e8a600d643b5aa951317f2aba;hb=HEAD
FFmpeg's svq1 encoder is being miscompiled by GCC 6 starting with revision
r232361. I'm attaching example assembly of the last good commit and the first
bad, alongside the preprocessed output.
To reproduce the issue you can download ffmpeg and run the fate svq1 tests (no
external samples needed to run), which will fail and create output video files
full of artifacts from the revision mentioned above onward:
git clone https://git.videolan.org/git/ffmpeg.git && cd ffmpeg && ./configure
&& make fate-vsynth{1,2,3}-svq1
