RFC: Update ISL under gcc/infrastructure/ ? // Remove CLooG?

Tobias Grosser tobias@grosser.es
Wed Nov 5 23:39:00 GMT 2014

On 04.11.2014 16:17, Tobias Burnus wrote:
> Hi all,
> currently, contrib/download_prerequisites downloads isl-0.12.2 from
> ftp://gcc.gnu.org/pub/gcc/infrastructure/$ISL.tar.bz2
> However, that version has a bug which causes an ICE (PR 62289).
> End of October, ISL 0.14 was released, which should contain a fix for
> that issue. Hence, one should consider using 0.14 instead of /infrastructure/
> and download_prerequisites.
> Download: http://isl.gforge.inria.fr

Thanks Tobias for bringing this one up.

> Disclaimer: I haven't tested that version, yet.
>   * * *
> The page https://gcc.gnu.org/install/prerequisites.html lists 0.12.2 as
> version to be used (without "(or later)").
> The configure script does some version checks, but seeminly only to rule
> out early version of ISL as it is only the check for an include file.
> According to https://groups.google.com/forum/#!topic/isl-development/CQGVfj60SQM
> "0.14 was kept backward compatible with 0.13." [But 0.15 will break it.]
> Thus, assuming 0.13 works, 0.14 also should work. Release notes:
> http://repo.or.cz/w/isl.git/blob/HEAD:/ChangeLog

Right. 0.13 should work from svn revision 213816.

As Richard pointed out, isl introduce a backward incompatible change in 
0.13 that unfortunately made it impossible to compile 4.8 with isl 0.13.

Judging from Richards comments, this seems to continue to cause issues.

@Sven, we need to be very careful with such changes in the future. If it 
is low cost, we may even consider to make isl_int again available for
a couple of releases (from 0.14.1 on).

> Comments? Especially from Richard and Tobias?
> * * *
> Finally, is CLooG still needed or will GCC also work with only ISL? Looking
> at https://gcc.gnu.org/ml/gcc-patches/2014-08/msg01742.html , it seems as if
> it is about the right time to remove it.

CLooG is not necessarily needed. You can run graphite just with ISL. The 
main reason that ISL code generation is not enabled by default is that 
we did not yet get extensive testing and it was unclear who will have 
the time to fix possible bugs.

@Mircae, Roman: Would you have time to help with bug-fixing if we do the 
switch now? (I am happy to review patches and give advice, but can not 
do the full move myself)


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