[Bug tree-optimization/105990] Dead code elimination failed at -O3

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105990

--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
Another case

static short a;
static int b;

void foo(void);
void bar9_(void);
int main() {
    char c;
    b = a = 23;
    for (; b <= 1;)
        a = 1;
    bar9_();
    c = a >= 18 || 2 > 2 >> a ? 1 : 1 << a;
    if (c == 0)
        foo();
}

foo() also can be eliminated.