[Bug tree-optimization/97053] [10/11 Regression] an O2, O3 codegen bug

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97053

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Another testcase for -O2 -fno-tree-dse that shows more issues, that it affects
not just the overlapping case handling, but also can affect also the adjacent
cases:
struct __attribute__((packed, may_alias)) S { long long s; };
struct __attribute__((packed, may_alias)) T { short t; };

__attribute__((noipa)) void
test (char *p, char *q, int s)
{
  if ((s & 1) == 0)
    {
      if (*(short __attribute__((may_alias)) *) &p[sizeof (short)]
          != *(short __attribute__((may_alias)) *) &q[sizeof (short)]
          || (((struct S __attribute__((may_alias)) *) &p[1])->s
              != ((struct S __attribute__((may_alias)) *) &q[1])->s)
          || (*(short __attribute__((may_alias)) *) &p[2 * sizeof (short)]
              != *(short __attribute__((may_alias)) *) &q[2 * sizeof (short)]))
        __builtin_abort ();
    }
  else
    {
      if (*(short __attribute__((may_alias)) *) &p[sizeof (short)]
          != *(short __attribute__((may_alias)) *) &q[sizeof (short)]
          || (((struct S __attribute__((may_alias)) *) &p[1])->s
              != ((struct S __attribute__((may_alias)) *) &q[1])->s)
          || (((struct T __attribute__((may_alias)) *) &p[2 * sizeof (short) -
1])->t
              != ((struct T __attribute__((may_alias)) *) &q[2 * sizeof (short)
- 1])->t)
          || p[3 * sizeof (short) - 2] != q[3 * sizeof (short) - 2])
        __builtin_abort ();
    }
}

__attribute__((noipa)) void
foo (long long *p, char *q, char *r, char *s)
{
  char a[64] __attribute__((aligned (__alignof (short))));
  *(short __attribute__((may_alias)) *) &a[sizeof (short)] = 1;
  ((struct S __attribute__((may_alias)) *) &a[1])->s = p[0];
  *(short __attribute__((may_alias)) *) &a[2 * sizeof (short)] = 2;
  *(short __attribute__((may_alias)) *) &q[sizeof (short)] = 1;
  ((struct S __attribute__((may_alias)) *) &r[1])->s = p[0];
  *(short __attribute__((may_alias)) *) &s[2 * sizeof (short)] = 2;
  test (a, q, 0);
}

__attribute__((noipa)) void
bar (long long *p, char *q, char *r, char *s, char *t)
{
  char a[64] __attribute__((aligned (__alignof (short))));
  *(short __attribute__((may_alias)) *) &a[sizeof (short)] = 1;
  ((struct S __attribute__((may_alias)) *) &a[1])->s = p[0];
  ((struct T __attribute__((may_alias)) *) &a[2 * sizeof (short) - 1])->t = 2;
  a[3 * sizeof (short) - 2] = 3;
  *(short __attribute__((may_alias)) *) &q[sizeof (short)] = 1;
  ((struct S __attribute__((may_alias)) *) &r[1])->s = p[0];
  ((struct T __attribute__((may_alias)) *) &s[2 * sizeof (short) - 1])->t = 2;
  t[3 * sizeof (short) - 2] = 3;
  test (a, q, 1);
}

__attribute__((noipa)) void
baz (long long *p, char *q, char *r, char *s)
{
  char a[64] __attribute__((aligned (__alignof (short))));
  *(short __attribute__((may_alias)) *) &a[2 * sizeof (short)] = 2;
  ((struct S __attribute__((may_alias)) *) &a[1])->s = p[0];
  *(short __attribute__((may_alias)) *) &a[sizeof (short)] = 1;
  *(short __attribute__((may_alias)) *) &q[2 * sizeof (short)] = 2;
  ((struct S __attribute__((may_alias)) *) &r[1])->s = p[0];
  *(short __attribute__((may_alias)) *) &s[sizeof (short)] = 1;
  test (a, q, 2);
}

__attribute__((noipa)) void
qux (long long *p, char *q, char *r, char *s, char *t)
{
  char a[64] __attribute__((aligned (__alignof (short))));
  *(short __attribute__((may_alias)) *) &a[2 * sizeof (short) - 1] = 2;
  ((struct S __attribute__((may_alias)) *) &a[1])->s = p[0];
  a[3 * sizeof (short) - 2] = 3;
  *(short __attribute__((may_alias)) *) &a[sizeof (short)] = 1;
  ((struct T __attribute__((may_alias)) *) &q[2 * sizeof (short) - 1])->t = 2;
  ((struct S __attribute__((may_alias)) *) &r[1])->s = p[0];
  s[3 * sizeof (short) - 2] = 3;
  ((struct T __attribute__((may_alias)) *) &t[sizeof (short)])->t = 1;
  test (a, q, 3);
}

int
main ()
{
  char a[64];
  long long p = -1LL;
  foo (&p, &a[0], &a[0], &a[0]);
  bar (&p, &a[0], &a[0], &a[0], &a[0]);
  baz (&p, &a[0], &a[0], &a[0]);
  qux (&p, &a[0], &a[0], &a[0], &a[0]);
  return 0;
}