https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78762
Bug ID: 78762 Summary: Regression: Splitting unaligned AVX loads also when AVX2 is enabled Product: gcc Version: 7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: linux at carewolf dot com Target Milestone: --- Created attachment 40295 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40295&action=edit Test In gcc 7 when not optimizing for speed or newer Intel architectures unaligned AVX loads are now split. It appears this is on purpose, and the code related to it quite old, but I haven't been able to trigger it with older versions gcc (tried 4.9, 5 and 6). However this is a special tuning intended for Sandybridge and possibly AMD cpus. It does not trigger on any AVX2 processor. Therefore it now causes a universal performance degradation in code optimized for generic AVX2. I suggest this tuning is disabled when avx2 is enabled.