http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46194
--- Comment #9 from sebpop at gmail dot com <sebpop at gmail dot com>
2011-02-03 19:54:36 UTC ---
>> access_fn_A: {0, +, 1}_1
>> access_fn_B: {0, +, 1}_2
>>
>> (subscript
>> iterations_that_access_an_element_twice_in_A: [0 + 1 * x_1]
>> last_conflict: 1000
>> iterations_that_access_an_element_twice_in_B: [0 + 1 * x_1]
>
> I think that this representation of affine functions is wrong:
> the access in B should read [0 + 0 * x_1 + 1 * x_2] and that
> would not lead to a wrong conclusion like the following...
This representation is correct, as it stands for: there exists
a dependence for all x_1 from 0 to 1000, that is, there exist
a possible overlap that is represented by:
{0, +, 1}_1 ([0 + 1 * x_1]) == {0, +, 1}_2 ([0 + 1 * x_1])
>
>> last_conflict: 1000
>> (Subscript distance: 0
>> )
>> )
>> inner loop index: 0
>> loop nest: (1 2 )
>> distance_vector: 0 0
>> direction_vector: = =
>> )
>
This representation is still wrong, and so I went to see where this
was computed, and the bug seems to be in build_classic_dist_vector_1
I will submit a patch to fix this.
