s390.c (MIN_UNROLL_PROBES): Define.

s390.c (MIN_UNROLL_PROBES): Define.

	* config/s390/s390.c (MIN_UNROLL_PROBES): Define.
	(allocate_stack_space): New function, partially extracted from
	s390_emit_prologue.
	(s390_emit_prologue): Track offset to most recent stack probe.
	Code to allocate space moved into allocate_stack_space.
	Dump actions when no stack is allocated.
	(s390_prologue_plus_offset): New function.
	(s390_emit_stack_probe): Likewise.

	* gcc.dg/stack-check-5.c:  Add argument for s390.
	* lib/target-supports.exp:
	(check_effective_target_supports_stack_clash_protection): Enable for
	s390/s390x targets.

Co-Authored-By: Jeff Law <law@redhat.com>
From-SVN: r253049