[Bug tree-optimization/59594] [4.9 Regression] wrong code (by tree vectorizer) at -O3 on x86_64-linux-gnu

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59594

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Jakub Jelinek from comment #2)
> (In reply to H.J. Lu from comment #1)
> > It is caused by r204062.
> 
> That is only a part of the story, this testcase seems to be interesting.
> 
> Starting with r204062 until r204560 this has been broken because of an ldist
> bug.
> r204561 fixed that again and the testcase worked until r206147.
> r206148 (aka negative step vectorization support) started to ICE on this.
> With r206178 it stopped ICEing and works again with -O3 -mtune=generic, not
> sure if that has been intentional to change the generic tuning with that
> patch.  H.J.?

There was a typo in r206178 and was fixed by r206180:

http://gcc.gnu.org/git/?p=gcc.git;a=commit;h=ff385162ee38caf3100ba4a0f682241c3b0d681d

Can you try r206180 on this?

> Anyway, with -O3 -mtune=core-avx2 e.g. r206178 still ICEs and r206179 (which
> fixed the ICE) starts the miscompilation.