[Bug tree-optimization/123298] [13/14/15/16 Regression] wrong code at -O2/-O3 starting in GCC 9

[mikpelinux at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123298

--- Comment #6 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Started with r9-2635-g78ea9abc201824:

78ea9abc2018243af7f7ada6135144ac90c6ad27 is the first new commit
commit 78ea9abc2018243af7f7ada6135144ac90c6ad27
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 27 10:55:53 2018 +0000

    cfganal.h (rev_post_order_and_mark_dfs_back_seme): Declare.