bug with strict-aliasing for i[56]86

[Greg McGary]

The following test program loses for i586 and i686 with `-O1 -fstrict-aliasing'.
(It's OK for i386 and i486.)

The offending line is commented below.

`len' is garbage because it's allocated to a temporary on the stack,
but the store into the temporary is eliminated.  (It seems to me that
there's no need to have the temporary, since `len' already resides on
the stack as an incoming arg.)

Greg

------------------------------------------------------------------------------
typedef struct charp { char *v, *l, *h; } charp;

typedef struct string { charp str; unsigned length; } string;

extern void
frob (charp s)
{
}

string
hack_string (unsigned len)
{
  string ret;

  frob (ret.str);
  ret.length = len; /* ret.length gets garbage when i[56]86 and -fstrict-aliasing */
  return ret;
}

int
main (void)
{
  string s;
  s = hack_string (10);
  if (s.length != 10)
    abort ();
  return 0;
}
------------------------------------------------------------------------------