[Bug tree-optimization/85698] [8/9 Regression] CPU2017 525.x264_r fails starting with r257581

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85698

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
           Priority|P3                          |P2

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmpf.  Sounds like the issue requires "careful" preparation of stmt operand
order
(aka SSA name numbering).  We've had issues in this area in the past.

Can you help me with isolating this to a single function inside that file?
Maybe try sticking __attribute__((optimize("no-tree-vectorize"))) on some
functions.  Oh, there's also the vect_loop debug counter
(-fdbg-cnt=vect_loop:N).

Eventually we simply trigger a latent issue elsewhere when we now recognize
sth for SLP vectorization.

Otherwise I'll have to find a power8 machine where I can set up CPU 2017
myself (unlikely this week due to public holidays).