tree-vect-loop-manip.c (slpeel_add_loop_guard): Preserve preheaders.

2017-03-07  Richard Biener  <rguenther@suse.de>

	* tree-vect-loop-manip.c (slpeel_add_loop_guard): Preserve
	preheaders.

From-SVN: r245950

gcc/ChangeLog

+2017-03-07  Richard Biener  <rguenther@suse.de>
+
+	* tree-vect-loop-manip.c (slpeel_add_loop_guard): Preserve
+	preheaders.
+
 2017-03-07  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/i386/i386.c (ix86_local_alignment): Align most aggregates

gcc/tree-vect-loop-manip.c

@@ -569,6 +569,11 @@ slpeel_add_loop_guard (basic_block guard_bb, tree cond,
   enter_e->count -= new_e->count;
   enter_e->probability = inverse_probability (probability);
   set_immediate_dominator (CDI_DOMINATORS, guard_to, dom_bb);
+
+  /* Split enter_e to preserve LOOPS_HAVE_PREHEADERS.  */
+  if (enter_e->dest->loop_father->header == enter_e->dest)
+    split_edge (enter_e);
+
   return new_e;
 }