Avoid GCC 4.1 build failure in fold-const.c

We had:

	      tree t = fold_vec_perm (type, arg1, arg2,
				      vec_perm_indices (sel, 2, nelts));

where fold_vec_perm takes a const vec_perm_indices &.  GCC 4.1 apparently
required a public copy constructor:

gcc/vec-perm-indices.h:85: error: 'vec_perm_indices::vec_perm_indices(const vec_perm_indices&)' is private
gcc/fold-const.c:11410: error: within this context

even though no copy should be made here.  This patch tries to work
around that by constructing the vec_perm_indices separately.

2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* fold-const.c (fold_ternary_loc): Construct the vec_perm_indices
	in a separate statement.

From-SVN: r256740

gcc/ChangeLog

 2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	* fold-const.c (fold_ternary_loc): Construct the vec_perm_indices
+	in a separate statement.
+
+2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	* tree-vect-data-refs.c (vect_analyze_data_ref_accesses):
 
 2018-01-16  Jakub Jelinek  <jakub@redhat.com>

gcc/fold-const.c

@@ -11406,8 +11406,8 @@ fold_ternary_loc (location_t loc, enum tree_code code, tree type,
 		  else /* Currently unreachable.  */
 		    return NULL_TREE;
 		}
-	      tree t = fold_vec_perm (type, arg1, arg2,
-				      vec_perm_indices (sel, 2, nelts));
+	      vec_perm_indices indices (sel, 2, nelts);
+	      tree t = fold_vec_perm (type, arg1, arg2, indices);
 	      if (t != NULL_TREE)
 		return t;
 	    }