While changing LABEL_REF_LABEL it might as well become an inline
function, so that its clearer what types are involved.  Unfortunately
because it is still possible to use XEXP and related macros on a
LABEL_REF rtx you can still set the field to be a non insn rtx.  The
other unfortunate thing is that the generators actually create LABEL_REF
rtx that refer to MATCH_x rtx, so there we actually need to use XEXP to
bypass the checking this patch adds.

gcc/ChangeLog:

2016-10-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* rtl.h (label_ref_label): New function.
	(set_label_ref_label): New function.
	(LABEL_REF_LABEL): Delete.
	* alias.c (rtx_equal_for_memref_p): Adjust.
	* cfgbuild.c (make_edges): Likewise.
	(purge_dead_tablejump_edges): Likewise.
	* cfgexpand.c (convert_debug_memory_address): Likewise.
	* cfgrtl.c (patch_jump_insn): Likewise.
	* combine.c (distribute_notes): Likewise.
	* cse.c (hash_rtx_cb): Likewise.
	(exp_equiv_p): Likewise.
	(fold_rtx): Likewise.
	(check_for_label_ref): Likewise.
	* cselib.c (rtx_equal_for_cselib_1): Likewise.
	(cselib_hash_rtx): Likewise.
	* emit-rtl.c (mark_label_nuses): Likewise.
	* explow.c (convert_memory_address_addr_space_1): Likewise.
	* final.c (output_asm_label): Likewise.
	(output_addr_const): Likewise.
	* gcse.c (add_label_notes): Likewise.
	* genconfig.c (walk_insn_part): Likewise.
	* genrecog.c (validate_pattern): Likewise.
	* ifcvt.c (cond_exec_get_condition): Likewise.
	(noce_emit_store_flag): Likewise.
	(noce_get_alt_condition): Likewise.
	(noce_get_condition): Likewise.
	* jump.c (maybe_propagate_label_ref): Likewise.
	(mark_jump_label_1): Likewise.
	(redirect_exp_1): Likewise.
	(rtx_renumbered_equal_p): Likewise.
	* lra-constraints.c (operands_match_p): Likewise.
	* print-rtl.c (print_value): Likewise.
	* reload.c (find_reloads): Likewise.
	* reload1.c (set_label_offsets): Likewise.
	* reorg.c (get_branch_condition): Likewise.
	* rtl-tests.c (test_uncond_jump): Likewise.
	* rtl.c (rtx_equal_p_cb): Likewise.
	(rtx_equal_p): Likewise.
	* rtlanal.c (reg_mentioned_p): Likewise.
	(rtx_referenced_p): Likewise.
	(get_condition): Likewise.
	* varasm.c (const_hash_1): Likewise.
	(compare_constant): Likewise.
	(const_rtx_hash_1): Likewise.
	(output_constant_pool_1): Likewise.

From-SVN: r241401