[PATCH v14 19/19] vect: Guard against infinite loop in vect_create_constant_vectors

If we need to replicate the vectors but vec_num ends up with a
value of 0 because of alterations elsewhere in this function
then the final loop never terminates because no SLP_TREE_VEC_DEFS
are pushed by its inner loop.  This change eases debugging.

gcc/ChangeLog:

	* tree-vect-slp.cc (vect_create_constant_vectors):
	Add an assertion to guard against the outer loop never
	terminating because the inner loop is never entered.
---
 gcc/tree-vect-slp.cc | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index ca9bae97e7e..0880875bcf0 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -11282,9 +11282,15 @@ vect_create_constant_vectors (vec_info *vinfo, slp_tree op_node)
      NUMBER_OF_SCALARS/NUNITS or NUNITS/NUMBER_OF_SCALARS, and hence we have
      to replicate the vectors.  */
   while (number_of_vectors > SLP_TREE_VEC_DEFS (op_node).length ())
-    for (i = 0; SLP_TREE_VEC_DEFS (op_node).iterate (i, &vop) && i < vec_num;
-	 i++)
-      SLP_TREE_VEC_DEFS (op_node).quick_push (vop);
+    {
+      /* Guard against the outer loop never terminating because the
+	 inner loop is never entered.  */
+      gcc_checking_assert (vec_num > 0);
+
+      for (i = 0; SLP_TREE_VEC_DEFS (op_node).iterate (i, &vop) && i < vec_num;
+	   i++)
+	SLP_TREE_VEC_DEFS (op_node).quick_push (vop);
+    }
 }
 
 /* Get the scalar definition of the Nth lane from SLP_NODE or NULL_TREE
-- 
2.43.0