[graphite] discard scops for which entry==exit

In this patch we discard the scops where entry and exit are the same BB.
This is an effort to remove graphite-scop-detection.c:limit_scops.
Removing the limit_scops function introduces correctness regressions.
We are making relevant changes in incremental steps to fix those bugs,
and finally we intend to remove limit_scops.

2015-06-29  Aditya Kumar  <aditya.k7@samsung.com>
                Sebastian Pop <s.pop@samsung.com>

        * graphite-scop-detection.c (build_scops_1): Discard scops for which entry==exit

Co-Authored-By: Sebastian Pop <s.pop@samsung.com>

From-SVN: r225850

gcc/ChangeLog

 2015-07-15  Aditya Kumar  <aditya.k7@samsung.com>
+	    Sebastian Pop <s.pop@samsung.com>
+
+        * graphite-scop-detection.c (build_scops_1): Discard scops for
+	which entry==exit.
+
+2015-07-15  Aditya Kumar  <aditya.k7@samsung.com>
             Sebastian Pop <s.pop@samsung.com>
 
         * graphite-scop-detection.c (stmt_simple_for_scop_p): Bail out in

gcc/graphite-scop-detection.c

@@ -794,7 +794,14 @@ build_scops_1 (basic_block current, loop_p outermost_loop,
     {
       open_scop.exit = sinfo.exit;
       gcc_assert (open_scop.exit);
-      scops->safe_push (open_scop);
+      if (open_scop.entry != open_scop.exit)
+	scops->safe_push (open_scop);
+      else
+	{
+	  sinfo.difficult = true;
+	  sinfo.exits = false;
+	  sinfo.exit = NULL;
+	}
     }
 
   result.exit = sinfo.exit;