[Bug rtl-optimization/94618] [8/9/10 Regression] '-fcompare-debug' failure (length) with -O2 -fnon-call-exceptions since r8-565-g7581ce9a1ad6df9c

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94618

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:c41884a09206be0e21cad7eea71b9754daa969d4

commit r10-7769-gc41884a09206be0e21cad7eea71b9754daa969d4
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Apr 17 10:33:27 2020 +0200

    Fix -fcompare-debug issue in delete_insn_and_edges [PR94618]

    delete_insn_and_edges calls purge_dead_edges whenever deleting the last
insn
    in a bb, whatever it is.  If it called it only for mandatory last insns
    in the basic block (that may not be followed by DEBUG_INSNs, dunno if that
    is control_flow_insn_p or something more complex), that wouldn't be a
    problem, but as it calls it on any last insn and can actually do something
    in the bb, if such an insn is followed by one more more DEBUG_INSNs and
    nothing else in the same bb, we don't call purge_dead_edges with -g and do
    call it with -g0.

    On the testcase, there are two reg-to-reg moves with REG_EH_REGION notes
    (previously memory accesses but simplified and yet not optimized), and the
    second is followed by DEBUG_INSNs; the second move is delete_insn_and_edges
    and after removing it, for -g0 purge_dead_edges removes the REG_EH_REGION
    from the now last insn in the bb (the first reg-to-reg move), while
    for -g it isn't called and things diverge from that quickly on.

    Fixed by calling purdge_dead_edges even if we remove the last real insn
    followed only by DEBUG_INSNs in the same bb.

    2020-04-17  Jakub Jelinek  <jakub@redhat.com>

            PR rtl-optimization/94618
            * cfgrtl.c (delete_insn_and_edges): Set purge not just when
            insn is the BB_END of its block, but also when it is only followed
            by DEBUG_INSNs in its block.

            * g++.dg/opt/pr94618.C: New test.