[Polly-ACC] Add isl_space.h to gpu_tree.c

[alaindenzler]

Summary

This patch adds <isl_space.h> to gpu_tree.c. This prevents a segfault when allocating a new isl_space in the function create_sync_domain(), as the compiler now knows that the return type is a pointer instead of assuming the function returns an int.

Inspired by Tobias Grosser & Siddhart, initially discovered by Philip Pfaffe.

[philip.pfaffe]

Thanks for fixing this!

This can manifest itself as a bug only because we're building with C89, which doesn't even warn about the missing declaration. Does it make sense to also raise the version? That should be a separate change though.

[grosser]

Yes, raise we should raise the version. Also, please add a propoer commit message explaining what the underlying error was here. We should also make sure that this bug has been fixed in the latest ppcg, such that we do not re-import it again.

[alaindenzler]

I checked the latest ppcg source and the header is also included there. Maybe consider updating to the latest ppcg?

polly/trunk/lib/External/ppcg/gpu_tree.c

 /*
  * Copyright 2013      Ecole Normale Superieure
  *
  * Use of this software is governed by the MIT license
  *
  * Written by Sven Verdoolaege,
  * Ecole Normale Superieure, 45 rue d'Ulm, 75230 Paris, France
  */
 
 #include <string.h>
 
 #include <isl/set.h>
 #include <isl/union_set.h>
+#include <isl/space.h>
 
 #include "gpu_tree.h"
 
 /* The functions in this file are used to navigate part of a schedule tree
  * that is mapped to blocks.  Initially, this part consists of a linear
  * branch segment with a mark node with name "kernel" on the outer end
  * and a mark node with name "thread" on the inner end.
  * During the mapping to blocks, branching may be introduced, but only