[Bug middle-end/44838] [4.6 regression] FAIL: gcc.dg/pr39794.c

["sandra at codesourcery dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #7 from sandra at codesourcery dot com  2010-07-07 00:42 -------
Hmmm.  It's possible I built my toolchain incorrectly, but I'm seeing that it
aborts when compiled with -m64 but not with -m32.  The failure mode looks
identical to that reported in PR39794:

(gdb) print a
$1 = {0, 1, 4, 2, 10, 12, 24, 44, 72, 92, 60, 34, 244, 47, 58, 291}
(gdb) print ref
$2 = {0, 1, 4, 2, 10, 12, 24, 44, 72, 136, 232, 416, 736, 1296, 2304, 2032}

This slightly modified version of the test case fails when compiled with -m64
-O2 -funroll-loops -fno-ivopts:

extern void abort ();

void
foo (int *a, int n)
{
  int *lasta = a + n;
  for (; a != lasta; a++)
    {
      *a *= 2;
      a[1] = a[-1] + a[-2];
    }
}

int a[16];
int ref[16] = { 0, 1, 4, 2, 10, 12, 24, 44,
                72, 136, 232, 416, 736, 1296, 2304, 2032 };

int
main ()
{
  int i;
  for (i = 0; i < 16; i++)
    a[i] = i;
  foo (a + 2, 16 - 3);
  for (i = 0; i < 16; i++)
    if (ref[i] != a[i])
      abort ();
  return 0;
}

So, not an ivopts problem at all?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44838