https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68908
--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
While working on this, I've found something weird, as shown in the following
testcase:
int
main (void)
{
_Atomic _Bool a = 1;
__builtin_printf ("%d\n", a);
__atomic_fetch_add (&a, 1, __ATOMIC_SEQ_CST);
__builtin_printf ("%d\n", a);
_Atomic _Bool b = 1;
__builtin_printf ("%d\n", b);
++b;
__builtin_printf ("%d\n", b);
if (a != b)
__builtin_abort ();
}
crashes, i.e. given _Atomic _Bool x = 1;
++x == 1, but
__atomic_fetch_add (&x, 1, __ATOMIC_SEQ_CST) == 2.
And because of that my patch to implement this optimization regresses
c11-atomic-exec-2.c and c11-atomic-exec-3.c, where we deal with incrementing
atomic bool.
