[FFmpeg-devel] [RFC] Disable gcc auto-vectorisation

Måns Rullgård mans
Tue Jul 14 00:47:37 CEST 2009

Since gcc 4.3, the auto-vectoriser (-ftree-vectorize) has been enabled
at -O3 optimisation level.  This vectoriser is, mildly put, useless.
When it doesn't produce outright broken code, it is a gamble whether
the result is any faster whatsoever, and we have seen cases where it
introduced a significant slowdown.

My proposal is to disable this misfeature by adding
-fno-tree-vectorize to the compiler flags when using gcc.

Does anyone have a good reason for not doing this?

M?ns Rullg?rd
mans at mansr.com

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