https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68909
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> --- (In reply to Chengnian Sun from comment #2) > Is it related to this recently fixed bug? > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67778 Doesn't look like it, this one has been caused by: commit a1965220d5ae62c617abfe40e1dc5c03bb7aa38f Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4> Date: Sat Nov 7 06:31:14 2015 +0000 [PATCH] Remove more backedge threading support * tree-ssa-threadedge.c (dummy_simplify): Remove. (thread_around_empty_blocks): Remove backedge_seen_p argument. If we thread to a backedge, then return false. Update recursive call to eliminate backedge_seen_p argument. (thread_through_normal_block): Remove backedge_seen_p argument. Remove backedge_seen_p argument from calls to thread_around_empty_blocks. Remove checks on backedge_seen_p. If we thread to a backedge, then return 0. (thread_across_edge): Remove bookkeeping for backedge_seen. Don't pass it to thread_through_normal_block or thread_through_empty_blocks. For joiner handling, if we see a backedge, do not try normal threading. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@229911 138bc75d-0d04-0410-961f-82ee72b054a4