re PR tree-optimization/84238 (ICE tree check: expected integer_cst, have plus_expr in to_wide, at tree.h:5527)

	PR tree-optimization/84238
	* tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Verify the result of
	get_range_strlen.

	* gcc.dg/Wstringop-overflow-3.c: New test.

From-SVN: r257497