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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/103986] [9/10 Regression] Miscompilation with
 -O2 -funswitch-loops and __builtin_unreachable
Date: Wed, 12 Jan 2022 07:08:04 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103986

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 {=20=20=20=20=20=20=20=20
        short x;
        short y;
        short z;
};
static inline
void f(struct GridZYXIterator *t) {
    t->x++;
    if(t->x =3D=3D 3) {
        t->x =3D 0;
        t->y++;
        if(t->y =3D=3D 3) {
            t->y =3D 0;
            t->z++;
        }
    }
}
static int t =3D 0;
static void g() __attribute__((noipa));
static void g(){t++; if (t > 27) __builtin_abort();};
int main()
{
        struct GridZYXIterator it =3D {0,0,0};
        while(it.z !=3D 3) {
        assume(it.y < 3 && it.z < 3);
                g();
                f(&it);
        }=20=20=20=20=20=20=20
}

Confirmed.=