* gimple-fold.c (get_range_strlen_tree): Record if the computed
	length is optimistic.  If it is, then arrange to compute the
	conservative length as well.

	* gcc.dg/strlenopt-40.c: Update
	* gcc.dg/strlenopt-51.c: Likewise.
	* gcc.dg/tree-ssa/pr79376.c: Likewise.

Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r267505