[Bug tree-optimization/81403] [8 Regression] wrong code at -O3

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81403

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Kind-of a duplicate of PR80620 as well.  Testing a patch.