[Bug tree-optimization/66873] fortran variant of outer-1.c not parallelized by autopar

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66873

--- Comment #9 from vries at gcc dot gnu.org ---
(In reply to vries from comment #7)
> Created attachment 35986 [details]
> Updated tentative patch
> 
> I found that always doing graphite before parloops resulted in failures to
> parallelize reduction testcases.
> 

That was due to not using -ffast-math.

By using this ( https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01863.html )
approved patch, we no longer have that problem.

However, we run into: PR66997 - outer loop reduction fails to parallelize with
graphite.

And the runtime of graphite is excessive in some cases, with prevents us from
using graphite by default, f.i. Bug 53852 - [4.9/5/6 Regression]
-ftree-loop-linear: large compile time / memory usage.