S/390: Remove TARGET_CPU_ZARCH

S/390: Remove TARGET_CPU_ZARCH

TARGET_CPU_ZARCH allowed to distinguish between g5/g6 and newer
machines.  Since the former are now gone, we can assume that
TARGET_CPU_ZARCH is always true.  As a side-effect, branch splitting
is now completely gone.  Some parts of literal pool splitting are also
gone, but it's still there: we need to support it because floating
point and vector instructions still cannot use relative addressing.

gcc/ChangeLog:

2018-08-08  Ilya Leoshkevich  <iii@linux.ibm.com>

	* config/s390/s390.c (s390_loadrelative_operand_p):
        Remove TARGET_CPU_ZARCH usages.
	(s390_rtx_costs): Likewise.
	(s390_legitimate_constant_p): Likewise.
	(s390_cannot_force_const_mem): Likewise.
	(legitimate_reload_constant_p): Likewise.
	(s390_preferred_reload_class): Likewise.
	(legitimize_pic_address): Likewise.
	(legitimize_tls_address): Likewise.
	(s390_split_branches): Removed.
	(s390_add_execute): Removed.
	(s390_dump_pool): Remove TARGET_CPU_ZARCH usages.
	(s390_mainpool_start): Likewise.
	(s390_mainpool_finish): Likewise.
	(s390_mainpool_cancel): Removed.
	(s390_chunkify_start): Remove TARGET_CPU_ZARCH usages.
	(s390_chunkify_cancel): Likewise.
	(s390_return_addr_rtx): Likewise.
	(s390_register_info): Remove split_branches_pending_p uages.
	(s390_optimize_register_info): Likewise.
	(s390_init_frame_layout): Remove TARGET_CPU_ZARCH and
        split_branches_pending_p usages.
	(s390_can_eliminate): Remove TARGET_CPU_ZARCH usages.
	(s390_load_got): Likewise.
	(s390_expand_split_stack_prologue): Likewise.
	(output_asm_nops): Likewise.
	(s390_function_profiler): Likewise.
	(s390_emit_call): Likewise.
	(s390_conditional_register_usage): Likewise.
	(s390_optimize_prologue): Likewise.
	(s390_reorg): Remove TARGET_CPU_ZARCH and
        split_branches_pending_p usages.
	(s390_option_override_internal): Remove TARGET_CPU_ZARCH
        usages.
	(s390_output_indirect_thunk_function): Likewise.
	* config/s390/s390.h (TARGET_CPU_ZARCH): Removed.
	(TARGET_CPU_ZARCH_P): Removed.
	(struct machine_function): Remove split_branches_pending_p.
	* config/s390/s390.md: Remove TARGET_CPU_ZARCH usages.

From-SVN: r263394