Re: asking your advice about bug

[Tobias Grosser <tobias at grosser dot es>]

On 02/17/2014 06:50 PM, Roman Gareev wrote:
> Hi Tobias,
>
>
>   thanks for the answer!

Hi Roman,

sorry for missing this mail.

>   I think that the segfault is being caused by NULL arguments being passedto compute_deps
> by loop_level_carries_dependences. *This is **causing **an* *assignment of**
> NULL values to the following parameters of **compute_deps:* must_raw_no_source,
> may_raw_no_source, must_war_no_source, may_war_no_source,
> must_waw_no_source, may_waw_no_source. They are being passed to subtract_commutative_associative_deps
> and dereferenced in the following statements:
>
>
>   *must_raw_no_source = isl_union_map_subtract (*must_raw_no_source,
> x_must_raw_no_source);
>
>
>   *may_raw_no_source = isl_union_map_subtract (*may_raw_no_source,
> x_may_raw_no_source);
>
>
>   *must_war_no_source = isl_union_map_subtract (*must_war_no_source,
> x_must_war_no_source);
>
>
>   *may_war_no_source = isl_union_map_subtract (*may_war_no_source,
> x_may_war_no_source);
>
>
>   *must_waw_no_source = isl_union_map_subtract (*must_waw_no_source,
> x_must_waw_no_source);
>
>
>   *may_waw_no_source = isl_union_map_subtract (*may_waw_no_source,
> x_may_waw_no_source);
>
>   This is the reason of segfault. (All functions mentioned above are located
> in gcc/graphite-dependences.c)

Interesting analysis.

>   I think that this can be solved by the addition to
> subtract_commutative_associative_deps of NULL checking of the following
> variables: must_raw_no_source, may_raw_no_source, must_war_no_source,
> may_war_no_source, must_waw_no_source, may_waw_no_source. I've implemented
> this in the patch, which can be found below.

Yes, this would be a 'solution'. However, I am in fact surprised that 
those variables are NULL at all. Do you have an idea why this is the 
case? Understanding this would help to understand if the patch you 
propose is actually the right solution or if it is just hiding a 
previous bug.

Cheers,
Tobias