[Bug middle-end/108657] [13 Regression] csmith: possible wrong checksum with -O3 and -ftrivial-auto-var-init=zero

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108657

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-02-15

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
In the assembly, the important difference is that with just -O3 c is assigned 1
before calling the first bar, while -O3 -ftrivial-auto-var-init=zero it is
assigned 0.  This is visible already in optimized dump, which for the latter
stores first c = 1; and then twice c = 0; among the various DEFERRED_INITs.

Even further reduced:
int c, e, f;
static int *d = &c;

__attribute__((noipa)) void
foo (void)
{
  if (c != 1)
    __builtin_abort ();
}

int
main ()
{
  for (c = 1; c >= 0; c--)
    {
      e = 0;
      for (int j = 0; j <= 2; j++)
        {
          short k[1];
          if (e)
            break;
          e ^= f;
        }
    }
  *d = 1;
  foo ();
}