[Bug target/95646] [GCC 9/10] arm-none-eabi function attribute 'cmse_nonsecure_entry' wipes register values with -Os

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95646

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by SRINATH PARVATHANENI
<sripar01@gcc.gnu.org>:

https://gcc.gnu.org/g:f1370bf2aa6cac4ab6235d8480b0a5d4f85ca54e

commit r10-9806-gf1370bf2aa6cac4ab6235d8480b0a5d4f85ca54e
Author: Srinath Parvathaneni <srinath.parvathaneni@arm.com>
Date:   Thu May 6 10:46:45 2021 +0100

    arm: Do not clobber callee saved registers with CMSE.

    As reported in bugzilla when the -mcmse option is used while compiling for
size
    (-Os) with a thumb-1 target the generated code will clear the registers
r7-r10.
    These however are callee saved and should be preserved accross ABI
boundaries.
    The reason this happens is because these registers are made "fixed" when
    optimising for size with Thumb-1 in a way to make sure they are not used,
as
    pushing and popping hi-registers requires extra moves to and from LO_REGS.

    To fix this, this patch uses 'callee_saved_reg_p', which accounts for this
    optimisation, instead of 'call_used_or_fixed_reg_p'. Be aware of
    'callee_saved_reg_p''s definition, as it does still take call used
registers
    into account, which aren't callee_saved in my opinion, so it is a rather
    misnoemer, works in our advantage here though as it does exactly what we
need.

    gcc/ChangeLog:
    2020-06-19  Andre Vieira  <andre.simoesdiasvieira@arm.com>

            PR target/95646
            * config/arm/arm.c: (cmse_nonsecure_entry_clear_before_return): Use
            'callee_saved_reg_p' instead of 'calL_used_or_fixed_reg_p'.

    gcc/testsuite/ChangeLog:
    2020-06-19  Andre Vieira  <andre.simoesdiasvieira@arm.com>

            PR target/95646
            * gcc.target/arm/pr95646.c: New test.

    (cherry picked from commit 5f426554fd804d65509875d706d8b8bc3a48393b)