[Bug target/122539] CMSE wrongfully clearing non padded union members

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122539

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Andre Simoes Dias Vieira
<avieira@gcc.gnu.org>:

https://gcc.gnu.org/g:4aa3af633c26d61ad2a247bb3399cf815dd757e3

commit r16-5193-g4aa3af633c26d61ad2a247bb3399cf815dd757e3
Author: Andre Vieira <andre.simoesdiasvieira@arm.com>
Date:   Wed Nov 12 10:25:14 2025 +0000

    arm: Fix CMSE clearing of union members with no padding [PR122539]

    This patch fixes the CMSE register clearing to make sure we don't clear
    registers used by a function call.  Before this patch the algorithm would
only
    correctly handle registers with padding bits to clear, any registers that
were
    fully utilised would be wrongfully cleared.

    gcc/ChangeLog:

            PR target/122539
            * config/arm/arm.cc (comp_not_to_clear_mask_str_un): Update
            not_to_clear_reg_mask for union members.

    gcc/testsuite/ChangeLog:

            * gcc.target/arm/cmse/union-3.x: New test.
            * gcc.target/arm/cmse/baseline/union-3.c: New test.
            * gcc.target/arm/cmse/mainline/8m/union-3.c: New test.
            * gcc.target/arm/cmse/mainline/8_1m/union-3.c: New test.