S/390: Add -fsplit-stack support

S/390: Add -fsplit-stack support

libgcc/ChangeLog:

	* config.host: Use t-stack and t-stack-s390 for s390*-*-linux.
	* config/s390/morestack.S: New file.
	* config/s390/t-stack-s390: New file.
	* generic-morestack.c (__splitstack_find): Add s390-specific code.

gcc/ChangeLog:

	* common/config/s390/s390-common.c (s390_supports_split_stack):
	New function.
	(TARGET_SUPPORTS_SPLIT_STACK): New macro.
	* config/s390/s390-protos.h: Add s390_expand_split_stack_prologue.
	* config/s390/s390.c (struct machine_function): New field
	split_stack_varargs_pointer.
	(s390_register_info): Mark r12 as clobbered if it'll be used as temp
	in s390_emit_prologue.
	(s390_emit_prologue): Use r12 as temp if r1 is taken by split-stack
	vararg pointer.
	(morestack_ref): New global.
	(SPLIT_STACK_AVAILABLE): New macro.
	(s390_expand_split_stack_prologue): New function.
	(s390_live_on_entry): New function.
	(s390_va_start): Use split-stack vararg pointer if appropriate.
	(s390_asm_file_end): Emit the split-stack note sections.
	(TARGET_EXTRA_LIVE_ON_ENTRY): New macro.
	* config/s390/s390.md (UNSPEC_STACK_CHECK): New unspec.
	(UNSPECV_SPLIT_STACK_CALL): New unspec.
	(UNSPECV_SPLIT_STACK_DATA): New unspec.
	(split_stack_prologue): New expand.
	(split_stack_space_check): New expand.
	(split_stack_data): New insn.
	(split_stack_call): New expand.
	(split_stack_call_*): New insn.
	(split_stack_cond_call): New expand.
	(split_stack_cond_call_*): New insn.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@233421 138bc75d-0d04-0410-961f-82ee72b054a4