[Bug target/94697] aarch64: bti j at function start instead of bti c

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94697

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Szabolcs Nagy <nsz@gcc.gnu.org>:

https://gcc.gnu.org/g:f6e42cdee5de2b3441afc88c8888c1166bdffe57

commit r9-8594-gf6e42cdee5de2b3441afc88c8888c1166bdffe57
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Fri Apr 17 16:54:12 2020 +0100

    aarch64: ensure bti c is emitted at function start [PR94697]

    The bti pass currently first emits bti c at function start
    if there is no paciasp (which also acts as indirect call
    landing pad), then bti j is emitted at jump labels, however
    if there is a label right before paciasp then the function
    start can end up like

      foo:
      label:
        bti j
        paciasp
        ...

    This patch is a minimal fix that just moves the bti c handling
    after the bti j handling so we end up with

      foo:
        bti c
      label:
        bti j
        paciasp
        ...

    This could be improved by emitting bti jc in this case, or by
    detecting that the label is not in fact an indirect jump target
    and then this situation would be much less common.

    Needs to be backported to gcc-9 branch.

    Backported without the testcase because of missing infrastructure
    for check-function-bodies.

    gcc/ChangeLog:

            Backport from mainline.
            2020-04-23  Szabolcs Nagy  <szabolcs.nagy@arm.com>

            PR target/94697
            * config/aarch64/aarch64-bti-insert.c (rest_of_insert_bti): Swap
            bti c and bti j handling.