[bootstrap-O1] add initializers to avoid warnings at -O1

Building with the bootstrap-O1 configuration option fails to compile a
number of files due to AFAICT false-positive warnings about uses of
uninitialized variables.

This patch adds dummy initializers to silence them all.

for  gcc/ChangeLog

	* multiple_target.c (create_dispatcher_calls): Init e_next.
	* tree-ssa-loop-split.c (split_loop): Init border.
	* tree-vect-loop.c (vect_determine_vectorization_factor): Init
	scalar_type.

From-SVN: r244086

gcc/ChangeLog

+2017-01-04  Alexandre Oliva <aoliva@redhat.com>
+
+	* multiple_target.c (create_dispatcher_calls): Init e_next.
+	* tree-ssa-loop-split.c (split_loop): Init border.
+	* tree-vect-loop.c (vect_determine_vectorization_factor): Init
+	scalar_type.
+
 2017-01-04  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	PR target/71977

gcc/multiple_target.c

@@ -42,7 +42,7 @@ static void
 create_dispatcher_calls (struct cgraph_node *node)
 {
   cgraph_edge *e;
-  cgraph_edge *e_next;
+  cgraph_edge *e_next = NULL;
 
   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
   for (e = node->callers; e ;e = (e == NULL) ? e_next : e->next_caller)

gcc/tree-ssa-loop-split.c

@@ -497,7 +497,7 @@ split_loop (struct loop *loop1, struct tree_niter_desc *niter)
   unsigned i;
   bool changed = false;
   tree guard_iv;
-  tree border;
+  tree border = NULL_TREE;
   affine_iv iv;
 
   bbs = get_loop_body (loop1);

gcc/tree-vect-loop.c

@@ -183,7 +183,7 @@ vect_determine_vectorization_factor (loop_vec_info loop_vinfo)
   basic_block *bbs = LOOP_VINFO_BBS (loop_vinfo);
   unsigned nbbs = loop->num_nodes;
   unsigned int vectorization_factor = 0;
-  tree scalar_type;
+  tree scalar_type = NULL_TREE;
   gphi *phi;
   tree vectype;
   unsigned int nunits;