[clang] Miscompilation at -Os

[cardigan1008]

This code prints 1 at -Os and 0 at -O0/1/2/3:

int printf(const char *, ...);
long a, b = 208;
short c;
long(d)(long e) { return (a && e && 2036854775807 / e) * a; }
void f(long *e) {
  if (d(c | (*e = b || 0)))
    for (;;)
      ;
}
int main() {
  long *g = &b;
  *g = 0;
  f(&b);
  printf("%d\n", (int)b);
}

Compiler Explorer: https://godbolt.org/z/vPvna9s5Y

Bisected to ebe741f which was committed by @haopliu

[pinskia]

Reduced down to just:

int b = 208;
[[gnu::noinline]]
void f(int *e, int a) {
  *e = !!b;
  if (a)
    __builtin_trap();
}
int main(void) {
  b = 0;
  f(&b, 0);
  if (b != 0)
    __builtin_trap();
}

[nikic]

I think the problem here is basically the same as the one in #119116 (comment).

[haopliu]

Fixed the problem in #120044.

Will reenable the DSE improvement in #124058