[Bug tree-optimization/49632] ICE in compute_affine_dependence (tree-data-ref.c:4038) with -O3

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49632

Sebastian Pop <spop at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P5
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.07.08 04:55:59
     Ever Confirmed|0                           |1
           Severity|normal                      |minor

--- Comment #2 from Sebastian Pop <spop at gcc dot gnu.org> 2011-07-08 04:55:59 UTC ---
Further reduced the testcase to:

extern int k, A[7][7];
void f (void)
{
  for (int i = 0; i < 5; ++i)
    for (int j = 0; j < 5; ++j)
      for (k = 4; k >= 0; --k)
    A[i][j] = A[i][j+1];
}

And with this testcase, I have the following error:

| (Number of distance vectors differ: Banerjee has 1, Omega has 2.
| Banerjee dist vectors:
|   0   1   0 
| Omega dist vectors:
|   0   1   0 
|   0  -1   0 

And here again, Omega is wrong: a distance vector has to be
lexicographically positive: i.e., the first non zero component in a
distance vector (lexicographically = from left to right) should be
positive, and so the distance vector "0  -1   0" is wrong.

As in PR46851, I will just lower the priority of this bug: Omega is
not used elsewhere than in the implementation of -fcheck-data-deps.