_loop_vec_info::_loop_vec_info used get_loop_array to get the
order of the blocks when creating stmt_vec_infos, but then used
dfs_enumerate_from to get the order of the blocks that the rest
of the vectoriser uses.  We should be able to use that order
for creating stmt_vec_infos too.

2018-08-01  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Use the
	result of dfs_enumerate_from when constructing stmt_vec_infos,
	instead of additionally calling get_loop_body.

From-SVN: r263221