[Bug debug/68909] [6 Regression] ICE on valid code at -O3 on x86_64-linux-gnu in maybe_record_trace_start, at dwarf2cfi.c:2297

[mpolacek at gcc dot gnu.org]

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