gcse.c (INSN_CUID, [...]): Use gcc_assert and gcc_unreachable.

	* gcse.c (INSN_CUID, insert_set_in_table, find_avail_set,
	cprop_insn, do_local_cprop, local_cprop_pass, find_bypass_set,
	process_insert_insn, insert_insn_end_bb, pre_insert_copy_insn,
	hoist_code, extract_mentioned_regs_helper, compute_store_table,
	insert_store): Use gcc_assert and gcc_unreachable.
	* ggc-common.c (ggc_splay_alloc, ggc_splay_dont_free,
	gt_pch_note_object, gt_pch_note_reorder, relocate_ptrs,
	ggc_record_overhead): Likewise.
	* ggc-page.c (alloc_page, free_page, ggc_set_mark, ggc_marked_p,
	init_ggc, ggc_push_context, ggc_recalculate_in_use_p,
	ggc_pop_context, clear_marks, validate_free_objects,
	ggc_pch_read): Likewise.
	* ggc-zone.c (ggc_allocated_p, free_chunk, ggc_set_mark,
	ggc_marked_p, ggc_get_size, init_ggc, destroy_ggc_zone,
	ggc_push_context, check_cookies, ggc_collect,
	ggc_print_statistics): Likewise.
	* gimple-low.c (lower_function_body, lower_stmt,
	lower_bind_expr): Likewise.
	* gimplify.c (gimple_tree_eq, push_gimplify_context,
	pop_gimplify_context, gimple_pop_condition, create_tmp_var,
	declare_tmp_vars, gimple_add_tmp_var, annotate_all_with_locus,
	mostly_copy_tree_r, gimplify_return_expr, gimplify_switch_expr,
	gimplify_case_label_expr, gimplify_exit_block_expr,
	canonicalize_component_ref, gimplify_compound_lval,
	gimplify_self_mod_expr, gimplify_call_expr,
	gimplify_init_ctor_eval, gimplify_init_constructor,
	gimplify_modify_expr, gimplify_save_expr, gimplify_target_expr,
	gimplify_expr, check_pointer_types_r,
	force_gimple_operand): Likewise.
	* global.c (global_alloc, build_insn_chain): Likewise.
	* graph.c (clean_graph_dump_file,
	finish_graph_dump_file): Likewise.
	gcov-io.c (gcov_open): Use GCOV_CHECK.

From-SVN: r87240