* common.opt (-fstack-clash-protection): New option.
	* flag-types.h (enum stack_check_type): Note difference between
	-fstack-check= and -fstack-clash-protection.
	* params.def (PARAM_STACK_CLASH_PROTECTION_GUARD_SIZE): New PARAM.
	(PARAM_STACK_CLASH_PROTECTION_PROBE_INTERVAL): Likewise.
	* toplev.c (process_options): Issue warnings/errors for cases
	not handled with -fstack-clash-protection.
	* doc/invoke.texi (-fstack-clash-protection): Document new option.
	(-fstack-check): Note additional problem with -fstack-check=generic.
	Note that -fstack-check is primarily for Ada and refer users
	to -fstack-clash-protection for stack-clash-protection.
	Document new params for stack clash protection.

	* gcc.dg/stack-check-2.c: New test.
	* lib/target-supports.exp
	(check_effective_target_supports_stack_clash_protection): New function.
	(check_effective_target_frame_pointer_for_non_leaf): Likewise.
	(check_effective_target_caller_implicit_probes): Likewise.

From-SVN: r252994