[Bug libstdc++/121148] Should use modular arithmetic for _Atomic_word

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121148

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ro at gcc dot gnu.org

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And the sparc code looks OK too, wrapping without UB:

    _Atomic_word __tmp1, __tmp2;
    _Atomic_word __val_extended = __val;

    __asm__ __volatile__("1:    ldx     [%3], %0\n\t"
                         "      add     %0, %4, %1\n\t"
                         "      casx    [%3], %0, %1\n\t"
                         "      sub     %0, %1, %0\n\t"
                         "      brnz,pn %0, 1b\n\t"
                         "       nop"
                         : "=&r" (__tmp1), "=&r" (__tmp2), "=m" (*__mem)
                         : "r" (__mem), "r" (__val_extended), "m" (*__mem));
    return __tmp2;