[cfgloop] PR middle-end/68375: Restructure get_loop_body_in_bfs_order to handle…

[cfgloop] PR middle-end/68375: Restructure get_loop_body_in_bfs_order to handle loops with only a header

	PR middle-end/68375
	* cfgloop.c (get_loop_body_in_bfs_order): Restructure loop to avoid
	bogus assertion.

	* gcc.dg/pr68375.c: New test.

From-SVN: r230798

gcc/ChangeLog

+2015-11-24  Richard Biener  <rguenther@suse.de>
+            Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR middle-end/68375
+	* cfgloop.c (get_loop_body_in_bfs_order): Restructure loop to avoid
+	bogus assertion.
+
 2015-11-24  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/68483

gcc/cfgloop.c

@@ -913,37 +913,32 @@ get_loop_body_in_bfs_order (const struct loop *loop)
   basic_block *blocks;
   basic_block bb;
   bitmap visited;
-  unsigned int i = 0;
-  unsigned int vc = 1;
+  unsigned int i = 1;
+  unsigned int vc = 0;
 
   gcc_assert (loop->num_nodes);
   gcc_assert (loop->latch != EXIT_BLOCK_PTR_FOR_FN (cfun));
 
   blocks = XNEWVEC (basic_block, loop->num_nodes);
   visited = BITMAP_ALLOC (NULL);
-
-  bb = loop->header;
+  blocks[0] = loop->header;
+  bitmap_set_bit (visited, loop->header->index);
   while (i < loop->num_nodes)
     {
       edge e;
       edge_iterator ei;
-
-      if (bitmap_set_bit (visited, bb->index))
-	/* This basic block is now visited */
-	blocks[i++] = bb;
+      gcc_assert (i > vc);
+      bb = blocks[vc++];
 
       FOR_EACH_EDGE (e, ei, bb->succs)
 	{
 	  if (flow_bb_inside_loop_p (loop, e->dest))
 	    {
+	      /* This bb is now visited.  */
 	      if (bitmap_set_bit (visited, e->dest->index))
 		blocks[i++] = e->dest;
 	    }
 	}
-
-      gcc_assert (i > vc);
-
-      bb = blocks[vc++];
     }
 
   BITMAP_FREE (visited);

gcc/testsuite/ChangeLog

+2015-11-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR middle-end/68375
+	* gcc.dg/pr68375.c: New test.
+
 2015-11-24  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/68483

gcc/testsuite/gcc.dg/pr68375.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized-graph" } */
+
+int a, c, d, e, g, h;
+short f;
+
+int
+foo ()
+{
+}
+
+short
+fn1 (void)
+{
+  int j[2];
+  for (; e; e++)
+    if (j[0])
+      for (;;)
+	;
+  if (!g)
+    return f;
+}
+
+int
+main (void)
+{
+  for (; a < 1; a++)
+    {
+      for (c = 0; c < 2; c++)
+	{
+	  d && (f = 0);
+	  h = fn1 ();
+	}
+      __builtin_printf ("%d\n", (char) f);
+   }
+
+ return 0;
+}
+