gcc:
2018-08-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* common.opt: Add new optimization option
	-fassume-zero-terminated-char-arrays.
	* gimple-fold.h (looks_like_a_char_array_without_typecast_p): Declare.
	* gimple-fold.c (looks_like_a_char_array_without_typecast_p): Helper
	function for strlen range estimations.
	(get_range_strlen): Use looks_like_a_char_array_without_typecast_p.
	* tree-ssa-strlen.c (maybe_set_strlen_range): Likewise.
	(get_min_string_length): Avoid not NUL terminated string literals.
	* doc/invoke.texi: Document -fassume-zero-terminated-char-arrays.
	* tree-ssa-dse.c (compute_trims): Avoid folding away undefined
	behaviour.

testsuite:
2018-08-32  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* gcc.dg/pr83373.c: Add xfail.
	* gcc.dg/strlenopt-36.c: Adjust test expectations.
	* gcc.dg/strlenopt-40.c: Likewise.
	* gcc.dg/strlenopt-45.c: Likewise.
	* gcc.dg/strlenopt-48.c: Likewise.
	* gcc.dg/strlenopt-51.c: Likewise.
	* gcc.dg/strlenopt-57.c: New test.
	* gcc.dg/strlenopt-58.c: New test.
	* gcc.dg/strlenopt-59.c: New test.