3 * @author Sebastian Hack
15 #include <libcore/lc_opts.h>
16 #include <libcore/lc_opts_enum.h>
17 #include <libcore/lc_timing.h>
18 #endif /* WITH_LIBCORE */
29 #include "iredges_t.h"
39 #include "firm/bearch_firm.h"
40 #include "ia32/bearch_ia32.h"
41 #include "arm/bearch_arm.h"
42 #include "ppc32/bearch_ppc32.h"
43 #include "mips/bearch_mips.h"
50 #include "besched_t.h"
51 #include "belistsched.h"
53 #include "bespillbelady.h"
55 #include "beraextern.h"
56 #include "bechordal_t.h"
58 #include "beifg_impl.h"
59 #include "becopyopt.h"
60 #include "becopystat.h"
61 #include "bessadestr.h"
64 #include "beschedmris.h"
67 #include "beprofile.h"
68 #include "beblocksched.h"
69 #include "be_dbgout.h"
71 /* options visible for anyone */
72 static be_options_t be_options = {
73 DUMP_NONE, /* dump flags */
74 BE_TIME_OFF, /* no timing */
75 0, /* no opt profile */
76 1, /* try to omit frame pointer */
77 0, /* always stabs debugging output */
78 BE_VRFY_WARN, /* verification level: warn */
79 "i44pc52.info.uni-karlsruhe.de", /* ilp server */
80 "cplex" /* ilp solver */
84 static char config_file[256] = { 0 };
86 /* register allocator to use. */
87 static const be_ra_t *ra = &be_ra_chordal_allocator;
89 /* back end instruction set architecture to use */
90 static const arch_isa_if_t *isa_if = &ia32_isa_if;
94 static lc_opt_entry_t *be_grp_root = NULL;
96 /* possible dumping options */
97 static const lc_opt_enum_mask_items_t dump_items[] = {
98 { "none", DUMP_NONE },
99 { "initial", DUMP_INITIAL },
101 { "sched", DUMP_SCHED },
102 { "prepared", DUMP_PREPARED },
103 { "regalloc", DUMP_RA },
104 { "final", DUMP_FINAL },
106 { "all", 2 * DUMP_BE - 1 },
110 /* register allocators */
111 static const lc_opt_enum_const_ptr_items_t ra_items[] = {
112 { "chordal", &be_ra_chordal_allocator },
113 { "external", &be_ra_external_allocator },
117 /* instruction set architectures. */
118 static const lc_opt_enum_const_ptr_items_t isa_items[] = {
119 { "ia32", &ia32_isa_if },
121 { "arm", &arm_isa_if },
122 { "ppc32", &ppc32_isa_if },
123 { "mips", &mips_isa_if },
128 /* verify options. */
129 static const lc_opt_enum_int_items_t vrfy_items[] = {
130 { "off", BE_VRFY_OFF },
131 { "warn", BE_VRFY_WARN },
132 { "assert", BE_VRFY_ASSERT },
136 static lc_opt_enum_mask_var_t dump_var = {
137 &be_options.dump_flags, dump_items
140 static lc_opt_enum_const_ptr_var_t ra_var = {
141 (const void **) &ra, ra_items
144 static lc_opt_enum_const_ptr_var_t isa_var = {
145 (const void **) &isa_if, isa_items
148 static lc_opt_enum_int_var_t vrfy_var = {
149 &be_options.vrfy_option, vrfy_items
152 static const lc_opt_table_entry_t be_main_options[] = {
153 LC_OPT_ENT_STR ("config", "read another config file containing backend options", config_file, sizeof(config_file)),
154 LC_OPT_ENT_ENUM_MASK("dump", "dump irg on several occasions", &dump_var),
155 LC_OPT_ENT_ENUM_PTR ("ra", "register allocator", &ra_var),
156 LC_OPT_ENT_ENUM_PTR ("isa", "the instruction set architecture", &isa_var),
157 LC_OPT_ENT_NEGBOOL ("noomitfp", "do not omit frame pointer", &be_options.omit_fp),
158 LC_OPT_ENT_BOOL ("stabs", "enable stabs debug support", &be_options.stabs_debug_support),
159 LC_OPT_ENT_ENUM_PTR ("vrfy", "verify the backend irg", &vrfy_var),
160 LC_OPT_ENT_BOOL ("time", "get backend timing statistics", &be_options.timing),
161 LC_OPT_ENT_BOOL ("profile", "instrument the code for execution count profiling", &be_options.opt_profile),
164 LC_OPT_ENT_STR ("ilp.server", "the ilp server name", be_options.ilp_server, sizeof(be_options.ilp_server)),
165 LC_OPT_ENT_STR ("ilp.solver", "the ilp solver name", be_options.ilp_solver, sizeof(be_options.ilp_solver)),
166 #endif /* WITH_ILP */
170 #endif /* WITH_LIBCORE */
172 void be_opt_register(void)
176 lc_opt_entry_t *be_grp_ra;
177 static int run_once = 0;
181 be_grp_root = lc_opt_get_grp(firm_opt_get_root(), "be");
182 be_grp_ra = lc_opt_get_grp(be_grp_root, "ra");
184 lc_opt_add_table(be_grp_root, be_main_options);
186 /* register allocator options */
187 for(i = 0; ra_items[i].name != NULL; ++i) {
188 const be_ra_t *ra = ra_items[i].value;
189 ra->register_options(be_grp_ra);
192 /* register isa options */
193 for(i = 0; isa_items[i].name != NULL; ++i) {
194 const arch_isa_if_t *isa = isa_items[i].value;
195 isa->register_options(be_grp_root);
198 /* scheduler register options */
199 list_sched_register_options(be_grp_root);
201 be_block_schedule_register_options(be_grp_root);
203 #endif /* WITH_LIBCORE */
206 /* Parse one argument. */
207 int be_parse_arg(const char *arg) {
209 if (strcmp(arg, "help") == 0 || (arg[0] == '?' && arg[1] == '\0')) {
210 lc_opt_print_help(be_grp_root, stdout);
213 return lc_opt_from_single_arg(be_grp_root, NULL, arg, NULL);
216 #endif /* WITH_LIBCORE */
219 /** The be parameters returned by default, all off. */
220 const static backend_params be_params = {
227 /* Perform schedule verification if requested. */
228 static void be_sched_vrfy(ir_graph *irg, int vrfy_opt) {
229 if (vrfy_opt == BE_VRFY_WARN) {
230 be_verify_schedule(irg);
232 else if (vrfy_opt == BE_VRFY_ASSERT) {
233 assert(be_verify_schedule(irg) && "Schedule verification failed.");
237 /* Initialize the Firm backend. Must be run BEFORE init_firm()! */
238 const backend_params *be_init(void)
248 if (isa_if->get_params)
249 return isa_if->get_params();
254 * Initializes the main environment for the backend.
256 * @param env an empty environment
257 * @param file_handle the file handle where the output will be written to
259 static be_main_env_t *be_init_env(be_main_env_t *env, FILE *file_handle)
261 memset(env, 0, sizeof(*env));
262 obstack_init(&env->obst);
263 env->arch_env = obstack_alloc(&env->obst, sizeof(env->arch_env[0]));
264 env->options = &be_options;
265 FIRM_DBG_REGISTER(env->dbg, "be.main");
267 arch_env_init(env->arch_env, isa_if, file_handle, env);
269 /* Register the irn handler of the architecture */
270 if (arch_isa_get_irn_handler(env->arch_env->isa))
271 arch_env_push_irn_handler(env->arch_env, arch_isa_get_irn_handler(env->arch_env->isa));
274 * Register the node handler of the back end infrastructure.
275 * This irn handler takes care of the platform independent
276 * spill, reload and perm nodes.
278 arch_env_push_irn_handler(env->arch_env, &be_node_irn_handler);
279 env->phi_handler = be_phi_handler_new(env->arch_env);
280 arch_env_push_irn_handler(env->arch_env, env->phi_handler);
282 env->db_handle = be_options.stabs_debug_support ? be_stabs_open(file_handle) : be_nulldbg_open();
286 static void be_done_env(be_main_env_t *env)
288 env->arch_env->isa->impl->done(env->arch_env->isa);
289 be_dbg_close(env->db_handle);
290 be_phi_handler_free(env->phi_handler);
291 obstack_free(&env->obst, NULL);
295 * A wrapper around a firm dumper. Dumps only, if
298 * @param mask a bitmask containing the reason what will be dumped
299 * @param irg the IR graph to dump
300 * @param suffix the suffix for the dumper
301 * @param dumper the dumper to be called
303 static void dump(int mask, ir_graph *irg, const char *suffix,
304 void (*dumper)(ir_graph *, const char *))
306 if(be_options.dump_flags & mask)
307 be_dump(irg, suffix, dumper);
311 * Prepare a backend graph for code generation and initialize its birg
313 static void initialize_birg(be_irg_t *birg, ir_graph *irg, be_main_env_t *env)
315 memset(birg, 0, sizeof(*birg));
317 birg->main_env = env;
319 edges_deactivate_kind(irg, EDGE_KIND_DEP);
320 edges_activate_kind(irg, EDGE_KIND_DEP);
322 DBG((env->dbg, LEVEL_2, "====> IRG: %F\n", irg));
323 dump(DUMP_INITIAL, irg, "-begin", dump_ir_block_graph);
325 be_stat_init_irg(env->arch_env, irg);
326 be_do_stat_nodes(irg, "01 Begin");
328 /* set the current graph (this is important for several firm functions) */
329 current_ir_graph = irg;
331 /* Normalize proj nodes. */
332 normalize_proj_nodes(irg);
334 /* Make just one return node. */
335 normalize_one_return(irg);
337 /* Remove critical edges */
338 remove_critical_cf_edges(irg);
340 /* Compute the dominance information. */
344 /* Ensure, that the ir_edges are computed. */
347 /* check, if the dominance property is fulfilled. */
348 be_check_dominance(irg);
350 /* reset the phi handler. */
351 be_phi_handler_reset(env->phi_handler);
356 #define BE_TIMER_PUSH(timer) \
357 if (be_options.timing == BE_TIME_ON) { \
358 int res = lc_timer_push(timer); \
359 if (be_options.vrfy_option == BE_VRFY_ASSERT) \
360 assert(res && "Timer already on stack, cannot be pushed twice."); \
361 else if (be_options.vrfy_option == BE_VRFY_WARN && ! res) \
362 fprintf(stderr, "Timer %s already on stack, cannot be pushed twice.\n", \
363 lc_timer_get_name(timer)); \
365 #define BE_TIMER_POP(timer) \
366 if (be_options.timing == BE_TIME_ON) { \
367 lc_timer_t *tmp = lc_timer_pop(); \
368 if (be_options.vrfy_option == BE_VRFY_ASSERT) \
369 assert(tmp == timer && "Attempt to pop wrong timer."); \
370 else if (be_options.vrfy_option == BE_VRFY_WARN && tmp != timer) \
371 fprintf(stderr, "Attempt to pop wrong timer. %s is on stack, trying to pop %s.\n", \
372 lc_timer_get_name(tmp), lc_timer_get_name(timer)); \
376 #define BE_TIMER_ONLY(code) do { if (be_options.timing == BE_TIME_ON) { code; } } while(0)
380 #define BE_TIMER_PUSH(timer)
381 #define BE_TIMER_POP(timer)
382 #define BE_TIMER_ONLY(code)
384 #endif /* WITH_LIBCORE */
388 * The Firm backend main loop.
389 * Do architecture specific lowering for all graphs
390 * and call the architecture specific code generator.
392 * @param file_handle the file handle the output will be written to
393 * @param cup_name name of the compilation unit
395 static void be_main_loop(FILE *file_handle, const char *cup_name)
400 unsigned num_nodes_b = 0;
401 unsigned num_nodes_a = 0;
402 unsigned num_nodes_r = 0;
403 char prof_filename[256];
404 static const char suffix[] = ".prof";
408 be_ra_timer_t *ra_timer;
411 lc_timer_t *t_abi = NULL;
412 lc_timer_t *t_codegen = NULL;
413 lc_timer_t *t_sched = NULL;
414 lc_timer_t *t_constr = NULL;
415 lc_timer_t *t_regalloc = NULL;
416 lc_timer_t *t_finish = NULL;
417 lc_timer_t *t_emit = NULL;
418 lc_timer_t *t_other = NULL;
419 lc_timer_t *t_verify = NULL;
421 if (be_options.timing == BE_TIME_ON) {
422 t_abi = lc_timer_register("beabi", "be abi introduction");
423 t_codegen = lc_timer_register("codegen", "codegeneration");
424 t_sched = lc_timer_register("sched", "scheduling");
425 t_constr = lc_timer_register("constr", "assure constraints");
426 t_regalloc = lc_timer_register("regalloc", "register allocation");
427 t_finish = lc_timer_register("finish", "graph finish");
428 t_emit = lc_timer_register("emiter", "code emiter");
429 t_verify = lc_timer_register("verify", "graph verification");
430 t_other = lc_timer_register("other", "other");
432 #endif /* WITH_LIBCORE */
434 be_init_env(&env, file_handle);
436 isa = arch_env_get_isa(env.arch_env);
438 be_dbg_so(env.db_handle, cup_name);
439 be_dbg_types(env.db_handle);
441 /* we might need 1 birg more for instrumentation constructor */
442 num_birgs = get_irp_n_irgs();
443 birgs = alloca(sizeof(birgs[0]) * (num_birgs + 1));
445 /* First: initialize all birgs */
446 for(i = 0; i < get_irp_n_irgs(); ++i) {
447 ir_graph *irg = get_irp_irg(i);
449 initialize_birg(&birgs[i], irg, &env);
453 Get the filename for the profiling data.
454 Beware: '\0' is already included in sizeof(suffix)
456 memset(prof_filename, 0, sizeof(prof_filename));
457 strncpy(prof_filename, cup_name, sizeof(prof_filename) - sizeof(suffix));
458 strcat(prof_filename, suffix);
461 Next: Either instruments all irgs with profiling code
462 or try to read in profile data for current translation unit.
464 if (be_options.opt_profile) {
465 ir_graph *prof_init_irg = be_profile_instrument(prof_filename, profile_default);
466 initialize_birg(&birgs[num_birgs], prof_init_irg, &env);
468 set_method_img_section(get_irg_entity(prof_init_irg), section_constructors);
471 be_profile_read(prof_filename);
475 for (i = 0; i < num_birgs; ++i) {
476 be_irg_t *birg = & birgs[i];
477 ir_graph *irg = birg->irg;
478 optimization_state_t state;
479 const arch_code_generator_if_t *cg_if;
481 /* set the current graph (this is important for several firm functions) */
482 current_ir_graph = irg;
484 /* stop and reset timers */
486 LC_STOP_AND_RESET_TIMER(t_abi);
487 LC_STOP_AND_RESET_TIMER(t_codegen);
488 LC_STOP_AND_RESET_TIMER(t_sched);
489 LC_STOP_AND_RESET_TIMER(t_constr);
490 LC_STOP_AND_RESET_TIMER(t_regalloc);
491 LC_STOP_AND_RESET_TIMER(t_finish);
492 LC_STOP_AND_RESET_TIMER(t_emit);
493 LC_STOP_AND_RESET_TIMER(t_verify);
494 LC_STOP_AND_RESET_TIMER(t_other);
496 BE_TIMER_PUSH(t_other); /* t_other */
499 * Create execution frequencies from profile data or estimate some
501 if(be_profile_has_data()) {
502 birg->execfreqs = be_create_execfreqs_from_profile(irg);
504 birg->execfreqs = compute_execfreq(irg, 10);
507 BE_TIMER_ONLY(num_nodes_b = get_num_reachable_nodes(irg));
509 /* Get the code generator interface. */
510 cg_if = isa->impl->get_code_generator_if(isa);
512 /* get a code generator for this graph. */
513 birg->cg = cg_if->init(birg);
515 /* some transformations need to be done before abi introduce */
516 arch_code_generator_before_abi(birg->cg);
518 /* reset the phi handler. */
519 be_phi_handler_reset(env.phi_handler);
521 /* implement the ABI conventions. */
522 BE_TIMER_PUSH(t_abi);
523 birg->abi = be_abi_introduce(birg);
526 dump(DUMP_ABI, irg, "-abi", dump_ir_block_graph);
527 be_do_stat_nodes(irg, "02 Abi");
530 BE_TIMER_PUSH(t_codegen);
531 arch_code_generator_prepare_graph(birg->cg);
532 BE_TIMER_POP(t_codegen);
534 be_do_stat_nodes(irg, "03 Prepare");
537 Since the code generator made a lot of new nodes and skipped
538 a lot of old ones, we should do dead node elimination here.
539 Note that this requires disabling the edges here.
541 edges_deactivate(irg);
542 //dead_node_elimination(irg);
545 /* Compute loop nesting information (for weighting copies) */
546 construct_cf_backedges(irg);
547 dump(DUMP_PREPARED, irg, "-prepared", dump_ir_block_graph);
548 BE_TIMER_ONLY(num_nodes_r = get_num_reachable_nodes(irg));
550 /* let backend prepare scheduling */
551 BE_TIMER_PUSH(t_codegen);
552 arch_code_generator_before_sched(birg->cg);
553 BE_TIMER_POP(t_codegen);
555 /* schedule the irg */
556 BE_TIMER_PUSH(t_sched);
557 list_sched(birg, &be_options);
558 BE_TIMER_POP(t_sched);
560 dump(DUMP_SCHED, irg, "-sched", dump_ir_block_graph_sched);
563 BE_TIMER_PUSH(t_verify);
564 be_sched_vrfy(irg, be_options.vrfy_option);
565 BE_TIMER_POP(t_verify);
567 be_do_stat_nodes(irg, "04 Schedule");
569 /* introduce patterns to assure constraints */
570 BE_TIMER_PUSH(t_constr);
571 /* we switch off optimizations here, because they might cause trouble */
572 save_optimization_state(&state);
574 set_opt_normalize(0);
576 /* add Keeps for should_be_different constrained nodes */
577 /* beware: needs schedule due to usage of be_ssa_constr */
578 assure_constraints(birg);
579 BE_TIMER_POP(t_constr);
581 dump(DUMP_SCHED, irg, "-assured", dump_ir_block_graph_sched);
582 be_do_stat_nodes(irg, "05 Constraints");
584 /* connect all stack modifying nodes together (see beabi.c) */
585 BE_TIMER_PUSH(t_abi);
586 be_abi_fix_stack_nodes(birg->abi, NULL);
589 dump(DUMP_SCHED, irg, "-fix_stack", dump_ir_block_graph_sched);
592 BE_TIMER_PUSH(t_verify);
593 be_sched_vrfy(irg, be_options.vrfy_option);
594 BE_TIMER_POP(t_verify);
596 /* do some statistics */
597 be_do_stat_reg_pressure(birg);
599 /* stuff needs to be done after scheduling but before register allocation */
600 BE_TIMER_PUSH(t_codegen);
601 arch_code_generator_before_ra(birg->cg);
602 BE_TIMER_POP(t_codegen);
604 /* Do register allocation */
605 BE_TIMER_PUSH(t_regalloc);
606 ra_timer = ra->allocate(birg);
607 BE_TIMER_POP(t_regalloc);
609 dump(DUMP_RA, irg, "-ra", dump_ir_block_graph_sched);
610 be_do_stat_nodes(irg, "06 Register Allocation");
612 /* let the code generator prepare the graph for emitter */
613 BE_TIMER_PUSH(t_finish);
614 arch_code_generator_after_ra(birg->cg);
615 BE_TIMER_POP(t_finish);
617 /* fix stack offsets */
618 BE_TIMER_PUSH(t_abi);
619 be_abi_fix_stack_nodes(birg->abi, NULL);
620 be_remove_dead_nodes_from_schedule(irg);
621 be_abi_fix_stack_bias(birg->abi);
624 BE_TIMER_PUSH(t_finish);
625 arch_code_generator_finish(birg->cg);
626 BE_TIMER_POP(t_finish);
628 dump(DUMP_FINAL, irg, "-finish", dump_ir_block_graph_sched);
630 /* check schedule and register allocation */
631 BE_TIMER_PUSH(t_verify);
632 if (be_options.vrfy_option == BE_VRFY_WARN) {
633 //irg_verify(irg, VRFY_ENFORCE_SSA);
634 be_check_dominance(irg);
635 be_verify_out_edges(irg);
636 be_verify_schedule(irg);
637 be_verify_register_allocation(env.arch_env, irg);
639 else if (be_options.vrfy_option == BE_VRFY_ASSERT) {
640 //assert(irg_verify(irg, VRFY_ENFORCE_SSA) && "irg verification failed");
641 assert(be_verify_out_edges(irg));
642 assert(be_check_dominance(irg) && "Dominance verification failed");
643 assert(be_verify_schedule(irg) && "Schedule verification failed");
644 assert(be_verify_register_allocation(env.arch_env, irg)
645 && "register allocation verification failed");
647 BE_TIMER_POP(t_verify);
649 /* emit assembler code */
650 BE_TIMER_PUSH(t_emit);
651 arch_code_generator_done(birg->cg);
652 BE_TIMER_POP(t_emit);
654 dump(DUMP_FINAL, irg, "-end", dump_ir_extblock_graph_sched);
656 BE_TIMER_PUSH(t_abi);
657 be_abi_free(birg->abi);
660 be_do_stat_nodes(irg, "07 Final");
661 restore_optimization_state(&state);
663 BE_TIMER_ONLY(num_nodes_a = get_num_reachable_nodes(irg));
664 BE_TIMER_POP(t_other);
666 #define LC_EMIT(timer) printf("%-20s: %.3lf msec\n", lc_timer_get_description(timer), (double)lc_timer_elapsed_usec(timer) / 1000.0)
667 #define LC_EMIT_RA(timer) printf("\t%-20s: %.3lf msec\n", lc_timer_get_description(timer), (double)lc_timer_elapsed_usec(timer) / 1000.0)
669 printf("==>> IRG %s <<==\n", get_entity_name(get_irg_entity(irg)));
670 printf("# nodes at begin: %u\n", num_nodes_b);
671 printf("# nodes before ra: %u\n", num_nodes_r);
672 printf("# nodes at end: %u\n\n", num_nodes_a);
678 LC_EMIT_RA(ra_timer->t_prolog);
679 LC_EMIT_RA(ra_timer->t_live);
680 LC_EMIT_RA(ra_timer->t_spill);
681 LC_EMIT_RA(ra_timer->t_spillslots);
682 LC_EMIT_RA(ra_timer->t_color);
683 LC_EMIT_RA(ra_timer->t_ifg);
684 LC_EMIT_RA(ra_timer->t_copymin);
685 LC_EMIT_RA(ra_timer->t_ssa);
686 LC_EMIT_RA(ra_timer->t_epilog);
687 LC_EMIT_RA(ra_timer->t_verify);
688 LC_EMIT_RA(ra_timer->t_other);
697 free_execfreq(birg->execfreqs);
699 /* switched off due to statistics (statistic module needs all irgs) */
700 if (! stat_is_active())
711 /* Main interface to the frontend. */
712 void be_main(FILE *file_handle, const char *cup_name)
715 lc_timer_t *t = NULL;
716 #endif /* WITH_LIBCORE */
719 /* The user specified another config file to read. do that now. */
720 if(strlen(config_file) > 0) {
723 if((f = fopen(config_file, "rt")) != NULL) {
724 lc_opt_from_file(config_file, f, NULL);
729 if (be_options.timing == BE_TIME_ON) {
730 t = lc_timer_register("bemain", "measure complete bemain loop");
732 if (lc_timer_enter_high_priority()) {
733 fprintf(stderr, "Warning: Could not enter high priority mode.\n");
736 lc_timer_reset_and_start(t);
738 #endif /* WITH_LIBCORE */
740 /* never build code for pseudo irgs */
741 set_visit_pseudo_irgs(0);
744 be_main_loop(file_handle, cup_name);
747 if (be_options.timing == BE_TIME_ON) {
749 lc_timer_leave_high_priority();
750 printf("%-20s: %lu msec\n", "BEMAINLOOP", lc_timer_elapsed_msec(t));
752 #endif /* WITH_LIBCORE */
755 /** The debug info retriever function. */
756 static retrieve_dbg_func retrieve_dbg = NULL;
758 /* Sets a debug info retriever. */
759 void be_set_debug_retrieve(retrieve_dbg_func func) {
763 /* Retrieve the debug info. */
764 const char *be_retrieve_dbg_info(const dbg_info *dbg, unsigned *line) {
766 return retrieve_dbg(dbg, line);
771 int be_put_ignore_regs(const be_irg_t *birg, const arch_register_class_t *cls, bitset_t *bs)
774 bs = bitset_alloca(cls->n_regs);
776 bitset_clear_all(bs);
778 assert(bitset_size(bs) == (unsigned) cls->n_regs);
779 arch_put_non_ignore_regs(birg->main_env->arch_env, cls, bs);
781 be_abi_put_ignore_regs(birg->abi, cls, bs);
782 return bitset_popcnt(bs);