re PR middle-end/82694 (Linux kernel miscompiled since r250765)

re PR middle-end/82694 (Linux kernel miscompiled since r250765)

	PR middle-end/82694
	* common.opt (fstrict-overflow): No longer an alias.
	(fwrapv-pointer): New option.
	* tree.h (TYPE_OVERFLOW_WRAPS, TYPE_OVERFLOW_UNDEFINED): Define
	also for pointer types based on flag_wrapv_pointer.
	* opts.c (common_handle_option) <case OPT_fstrict_overflow>: Set
	opts->x_flag_wrap[pv] to !value, clear opts->x_flag_trapv if
	opts->x_flag_wrapv got set.
	* fold-const.c (fold_comparison, fold_binary_loc): Revert 2017-08-01
	changes, just use TYPE_OVERFLOW_UNDEFINED on pointer type instead of
	POINTER_TYPE_OVERFLOW_UNDEFINED.
	* match.pd: Likewise in address comparison pattern.
	* doc/invoke.texi: Document -fwrapv and -fstrict-overflow.

	* gcc.dg/no-strict-overflow-7.c: Revert 2017-08-01 changes.
	* gcc.dg/tree-ssa/pr81388-1.c: Likewise.

From-SVN: r256686