tree-ssa-sccvn.c (vn_reference_lookup_3): Always punt if the call to get_ref_base_and_extent returns -1 as the max size.

	* tree-ssa-sccvn.c (vn_reference_lookup_3): Always punt if the call to
	get_ref_base_and_extent returns -1 as the max size.

From-SVN: r167958