[Bug tree-optimization/103986] [9/10 Regression] Miscompilation with -O2 -funswitch-loops and __builtin_unreachable

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103986

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-01-12
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Those come from dom3.

Here is a testcase which runs in finite time to test this (plus it is not a C
testcase also):
#define assume(Expression) do { if((Expression)) (void)0; else
__builtin_unreachable(); } while(0)
struct GridZYXIterator {        
        short x;
        short y;
        short z;
};
static inline
void f(struct GridZYXIterator *t) {
    t->x++;
    if(t->x == 3) {
        t->x = 0;
        t->y++;
        if(t->y == 3) {
            t->y = 0;
            t->z++;
        }
    }
}
static int t = 0;
static void g() __attribute__((noipa));
static void g(){t++; if (t > 27) __builtin_abort();};
int main()
{
        struct GridZYXIterator it = {0,0,0};
        while(it.z != 3) {
        assume(it.y < 3 && it.z < 3);
                g();
                f(&it);
        }       
}

Confirmed.