1 /* Copyright (C) 2002 by Universitaet Karlsruhe
4 * Authors: Goetz Lindenmaier
6 * irscc.c Computing the strongly connected regions and building
7 * backedge/loop datastructures.
17 #include "irgraph_t.h"
23 ir_graph *outermost_ir_graph; /* The outermost graph the scc is computed
25 static ir_loop *current_loop; /* Current loop construction is working
27 static int loop_node_cnt = 0; /* Counts the number of allocated loop nodes.
28 Each loop node gets a unique number.
29 What for? ev. remove. @@@ */
30 static int current_dfn = 1; /* Counter to generate depth first numbering
33 /**********************************************************************/
34 /* Node attributes needed for the construction. **/
35 /**********************************************************************/
37 typedef struct scc_info {
38 bool in_stack; /* Marks whether node is on the stack. */
39 int dfn; /* Depth first search number. */
40 int uplink; /* dfn number of ancestor. */
41 ir_loop *loop; /* Refers to the containing loop. */
43 struct section *section;
49 static INLINE scc_info* new_scc_info() {
50 scc_info *info = obstack_alloc (outermost_ir_graph->obst, sizeof (scc_info));
51 memset (info, 0, sizeof (scc_info));
56 mark_irn_in_stack (ir_node *n) {
57 assert(get_irn_link(n));
58 ((scc_info *)get_irn_link(n))->in_stack = true;
62 mark_irn_not_in_stack (ir_node *n) {
63 assert(get_irn_link(n));
64 ((scc_info *)get_irn_link(n))->in_stack = false;
68 irn_is_in_stack (ir_node *n) {
69 assert(get_irn_link(n));
70 return ((scc_info *)get_irn_link(n))->in_stack;
74 set_irn_uplink (ir_node *n, int uplink) {
75 assert(get_irn_link(n));
76 ((scc_info *)get_irn_link(n))->uplink = uplink;
80 get_irn_uplink (ir_node *n) {
81 assert(get_irn_link(n));
82 return ((scc_info *)get_irn_link(n))->uplink;
86 set_irn_dfn (ir_node *n, int dfn) {
87 if (! get_irn_link(n)) { DDMN(n); DDME(get_irg_ent(current_ir_graph));}
88 assert(get_irn_link(n));
89 ((scc_info *)get_irn_link(n))->dfn = dfn;
93 get_irn_dfn (ir_node *n) {
94 assert(get_irn_link(n));
95 return ((scc_info *)get_irn_link(n))->dfn;
98 /* Uses temporary information to set the loop */
100 set_irn_loop_tmp (ir_node *n, ir_loop* loop) {
101 assert(get_irn_link(n));
102 ((scc_info *)get_irn_link(n))->loop = loop;
105 /* Uses temporary information to get the loop */
106 static INLINE ir_loop *
107 get_irn_loop_tmp (ir_node *n) {
108 assert(get_irn_link(n));
109 return ((scc_info *)get_irn_link(n))->loop;
112 static ir_loop *find_nodes_loop (ir_node *n, ir_loop *l) {
116 /* Test whether n is contained in this loop. */
117 for (i = 0; i < get_loop_n_nodes(l); i++)
118 if (n == get_loop_node(l, i)) return l;
120 /* Is this a leave in the loop tree? If so loop not found. */
121 if (get_loop_n_sons(l) == 0) return NULL;
123 /* Else descend in the loop tree. */
124 for (i = 0; i < get_loop_n_sons(l); i++) {
125 res = find_nodes_loop(n, get_loop_son(l, i));
131 /* @@@ temporary implementation, costly!!! */
132 ir_loop * get_irn_loop(ir_node *n) {
133 ir_loop *l = get_irg_loop(current_ir_graph);
134 l = find_nodes_loop(n, l);
138 /**********************************************************************/
140 /**********************************************************************/
142 static ir_node **stack = NULL;
143 static int tos = 0; /* top of stack */
145 static INLINE void init_stack() {
147 ARR_RESIZE (ir_node *, stack, 1000);
149 stack = NEW_ARR_F (ir_node *, 1000);
154 static INLINE void free_stack() {
165 if (tos == ARR_LEN (stack)) {
166 int nlen = ARR_LEN (stack) * 2;
167 ARR_RESIZE (ir_node *, stack, nlen);
170 mark_irn_in_stack(n);
173 static INLINE ir_node *
176 ir_node *n = stack[--tos];
177 mark_irn_not_in_stack(n);
181 /* The nodes up to n belong to the current loop.
182 Removes them from the stack and adds them to the current loop. */
184 pop_scc_to_loop (ir_node *n)
190 set_irn_dfn(m, loop_node_cnt);
192 add_loop_node(current_loop, m);
193 set_irn_loop_tmp(m, current_loop);
198 /* Removes and unmarks all nodes up to n from the stack.
199 The nodes must be visited once more to assign them to a scc. */
201 pop_scc_unmark_visit (ir_node *n)
207 set_irn_visited(m, 0);
211 /**********************************************************************/
212 /* The loop datastructure. **/
213 /**********************************************************************/
215 /* Allocates a new loop as son of current_loop. Sets current_loop
216 to the new loop and returns the father. */
217 static ir_loop *new_loop (void) {
218 ir_loop *father, *son;
220 father = current_loop;
222 son = (ir_loop *) obstack_alloc (outermost_ir_graph->obst, sizeof (ir_loop));
223 memset (son, 0, sizeof (ir_loop));
224 son->kind = k_ir_loop;
225 son->sons = NEW_ARR_F (ir_loop *, 0);
226 son->nodes = NEW_ARR_F (ir_node *, 0);
228 son->outer_loop = father;
229 add_loop_son(father, son);
230 son->depth = father->depth+1;
231 } else { /* The root loop */
232 son->outer_loop = son;
240 /* Finishes the datastructures, copies the arrays to the obstack
241 of current_ir_graph. */
242 static void mature_loop (ir_loop *loop) {
245 new_sons = NEW_ARR_D (ir_loop *, current_ir_graph->obst, ARR_LEN(loop->sons));
246 memcpy (new_sons, loop->sons, sizeof (ir_loop *) * ARR_LEN(loop->sons));
247 DEL_ARR_F(loop->sons);
248 loop->sons = new_sons;
251 /* Returns outer loop, itself if outermost. */
252 ir_loop *get_loop_outer_loop (ir_loop *loop) {
253 assert(loop && loop->kind == k_ir_loop);
254 return loop->outer_loop;
257 /* Returns nesting depth of this loop */
258 int get_loop_depth (ir_loop *loop) {
259 assert(loop); assert(loop->kind == k_ir_loop);
263 /* Returns the number of inner loops */
264 int get_loop_n_sons (ir_loop *loop) {
265 assert(loop && loop->kind == k_ir_loop);
266 return ARR_LEN(loop->sons);
268 ir_loop *get_loop_son (ir_loop *loop, int pos) {
269 assert(loop && loop->kind == k_ir_loop);
270 return loop->sons[pos];
273 add_loop_son(ir_loop *loop, ir_loop *son) {
274 assert(loop && loop->kind == k_ir_loop);
275 ARR_APP1 (ir_loop *, loop->sons, son);
278 /* Returns the number of nodes in the loop */
279 int get_loop_n_nodes (ir_loop *loop) {
280 assert(loop); assert(loop->kind == k_ir_loop);
281 return ARR_LEN(loop->nodes);
283 ir_node *get_loop_node (ir_loop *loop, int pos) {
284 assert(loop && loop->kind == k_ir_loop);
285 return loop->nodes[pos];
288 add_loop_node(ir_loop *loop, ir_node *n) {
289 assert(loop && loop->kind == k_ir_loop);
290 ARR_APP1 (ir_node *, loop->nodes, n);
293 /* The outermost loop is remarked in the surrounding graph. */
294 void set_irg_loop(ir_graph *irg, ir_loop *loop) {
298 ir_loop *get_irg_loop(ir_graph *irg) {
303 /**********************************************************************/
304 /* Constructing and destructing the loop/backedge information. **/
305 /**********************************************************************/
307 /* Initialization steps. **********************************************/
310 init_node (ir_node *n, void *env) {
311 set_irn_link (n, new_scc_info());
314 /* Also init nodes not visible in intraproc_view. */
315 /* @@@ init_node is called for too many nodes -- this wastes memory!.
316 The mem is not lost as its on the obstack. */
317 if (get_irn_op(n) == op_Filter) {
318 for (i = 0; i < get_Filter_n_cg_preds(n); i++)
319 init_node(get_Filter_cg_pred(n, i), NULL);
321 if (get_irn_op(n) == op_Block) {
322 for (i = 0; i < get_Block_cg_n_cfgpreds(n); i++) {
323 init_node(get_Block_cg_cfgpred(n, i), NULL);
326 /* The following pattern matches only after a call from above pattern. */
327 if ((get_irn_op(n) == op_Proj) /*&& (get_Proj_proj(n) == 0)*/) {
328 /* @@@ init_node is called for every proj -- this wastes memory!.
329 The mem is not lost as its on the obstack. */
330 ir_node *cb = get_Proj_pred(n);
331 if ((get_irn_op(cb) == op_CallBegin) ||
332 (get_irn_op(cb) == op_EndReg) ||
333 (get_irn_op(cb) == op_EndExcept)) {
335 init_node(get_nodes_Block(cb), NULL);
341 init_scc (ir_graph *irg) {
345 irg_walk_graph (irg, init_node, NULL, NULL);
347 irg_walk (irg, link_to_reg_end, NULL, NULL);
356 cg_walk (init_node, NULL, NULL);
360 Works, but is inefficient.
364 interprocedural_view = 1;
368 for (i = 0; i < get_irp_n_irgs(); i++) {
369 current_ir_graph = get_irp_irg(i);
370 irg_walk_graph (current_ir_graph, init_node, NULL, NULL);
371 /* @@@ decrease max_visited to avoide double walks */
376 /* Condition for breaking the recursion. */
377 static bool is_outermost_Start(ir_node *n) {
378 /* Test whether this is the outermost Start node. If so
379 recursion must end. */
380 if ((get_irn_op(n) == op_Block) &&
381 (get_Block_n_cfgpreds(n) == 1) &&
382 (get_irn_op(skip_Proj(get_Block_cfgpred(n, 0))) == op_Start) &&
383 (get_nodes_Block(skip_Proj(get_Block_cfgpred(n, 0))) == n)) {
387 /* @@@ Bad condition:
388 not possible in interprocedural view as outermost_graph is
389 not necessarily the only with a dead-end start block.
390 Besides current_ir_graph is not set properly. */
391 if ((get_irn_op(n) == op_Block) &&
392 (n == get_irg_start_block(current_ir_graph))) {
393 if ((!interprocedural_view) ||
394 (current_ir_graph == outermost_ir_graph))
401 /* Don't walk from nodes to blocks except for Control flow operations. */
403 get_start_index(ir_node *n) {
404 if (is_cfop(n) || is_fragile_op(n) || get_irn_op(n) == op_Start)
410 /* Returns current_ir_graph and set it to the irg of predecessor index
412 static INLINE ir_graph *
413 switch_irg (ir_node *n, int index) {
414 ir_graph *old_current = current_ir_graph;
416 if (interprocedural_view) {
417 /* Only Filter and Block nodes can have predecessors in other graphs. */
418 if (get_irn_op(n) == op_Filter)
419 n = get_nodes_Block(n);
420 if (get_irn_op(n) == op_Block) {
421 ir_node *cfop = skip_Proj(get_Block_cfgpred(n, index));
422 if (is_ip_cfop(cfop)) {
423 current_ir_graph = get_irn_irg(cfop);
424 set_irg_visited(current_ir_graph, get_max_irg_visited());
432 /* Walks up the stack passing n and then finding the node
433 where we walked into the irg n is contained in.
434 Here we switch the irg. */
436 find_irg_on_stack (ir_node *n) {
438 ir_graph *old_current = current_ir_graph;
441 if (interprocedural_view) {
442 for (i = tos; i >= 0; i--) {
443 if (stack[i] == n) break;
450 for (; i >= 0; i--) {
452 //printf(" Visiting %d ", i); DDMN(m);
454 current_ir_graph = get_irn_irg(m);
457 if (get_irn_op(m) == op_Filter) {
458 /* Find the corresponding ip_cfop */
459 ir_node *pred = stack[i+1];
461 for (j = 0; j < get_Filter_n_cg_preds(m); j++)
462 if (get_Filter_cg_pred(m, j) == pred) break;
463 if (j >= get_Filter_n_cg_preds(m))
464 /* It is a filter we didn't pass as the predecessors are marked. */
466 assert(get_Filter_cg_pred(m, j) == pred);
476 static void test(ir_node *pred, ir_node *root, ir_node *this) {
478 if (get_irn_uplink(pred) >= get_irn_uplink(root)) return;
480 printf("this: %d ", get_irn_uplink(this)); DDMN(this);
481 printf("pred: %d ", get_irn_uplink(pred)); DDMN(pred);
482 printf("root: %d ", get_irn_uplink(root)); DDMN(root);
484 printf("tos: %d\n", tos);
486 for (i = tos; i >= 0; i--) {
487 ir_node *n = stack[i];
489 printf(" uplink: %d, pos: %d ", get_irn_uplink(n), i); DDMN(n);
493 /* Returns true if n is a loop header, i.e., it is a Block, Phi
494 or Filter node and has predecessors within the loop and out
497 is_head (ir_node *n, ir_node *root)
500 int some_outof_loop = 0, some_in_loop = 0;
502 /* Test for legal loop header */
503 if (!((get_irn_op(n) == op_Block) ||
504 (get_irn_op(n) == op_Phi) ||
505 ((get_irn_op(n) == op_Filter) && interprocedural_view)))
508 if (!is_outermost_Start(n)) {
509 for (i = get_start_index(n); i < get_irn_arity(n); i++) {
510 ir_node *pred = get_irn_n(n, i);
512 if (is_backedge(n, i)) continue;
513 if (!irn_is_in_stack(pred)) {
516 assert(get_irn_uplink(pred) >= get_irn_uplink(root));
521 return some_outof_loop && some_in_loop;
524 /* Returns index of the predecessor with the smallest dfn number
525 greater-equal than limit. */
527 smallest_dfn_pred (ir_node *n, int limit)
529 int i, index = -2, min = -1;
531 if (!is_outermost_Start(n)) {
532 for (i = get_start_index(n); i < get_irn_arity(n); i++) {
533 ir_node *pred = get_irn_n(n, i);
535 if (is_backedge(n, i) || !irn_is_in_stack(pred)) continue;
536 if (get_irn_dfn(pred) >= limit
537 && (min == -1 || get_irn_dfn(pred) < min)) {
539 min = get_irn_dfn(pred);
546 /* Returns index of the predecessor with the largest dfn number. */
548 largest_dfn_pred (ir_node *n)
550 int i, index = -2, max = -1;
552 if (!is_outermost_Start(n)) {
553 for (i = get_start_index(n); i < get_irn_arity(n); i++) {
554 ir_node *pred = get_irn_n(n, i);
555 if (is_backedge (n, i) || !irn_is_in_stack(pred)) continue;
556 if (get_irn_dfn(pred) > max) {
558 max = get_irn_dfn(pred);
565 /* Searches the stack for possible loop heads. Tests these for backedges.
566 If it finds a head with an unmarked backedge it marks this edge and
567 returns the tail of the loop.
568 If it finds no backedge returns NULL. */
570 find_tail (ir_node *n) {
572 int i, res_index = -2;
575 if (!icfg && rm_cyclic_phis && remove_cyclic_phis (n)) return NULL;
579 if (is_head (m, n)) {
580 res_index = smallest_dfn_pred(m, 0);
581 if ((res_index == -2) && /* no smallest dfn pred found. */
585 if (m == n) return NULL;
586 for (i = tos-2; ; --i) {
588 if (is_head (m, n)) {
589 res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
590 if (res_index == -2) /* no smallest dfn pred found. */
591 res_index = largest_dfn_pred (m);
596 assert (res_index > -2);
598 set_backedge (m, res_index);
599 return is_outermost_Start(n) ? NULL : get_irn_n(m, res_index);
603 /* The core algorithm. *****************************************/
605 static void scc (ir_node *n) {
609 if (irn_visited(n)) return;
611 //printf("mark: %d ", get_irn_visited(n)); DDMN(n);
612 //DDME(get_irg_ent(current_ir_graph));
614 /* Initialize the node */
615 set_irn_dfn(n, current_dfn); /* Depth first number for this node */
616 set_irn_uplink(n, current_dfn); /* ... is default uplink. */
617 set_irn_loop_tmp(n, NULL);
620 /* What's this good for?
621 n->ana.scc.section = NULL;
626 if (!is_outermost_Start(n)) {
627 for (i = get_start_index(n); i < get_irn_arity(n); i++) {
629 if (is_backedge(n, i)) continue;
631 m = get_irn_n(n, i); //get_irn_ip_pred(n, i);
632 if ((!m) || (get_irn_op(m) == op_Unknown)) continue;
634 //return_recur(n, i);
636 if (irn_is_in_stack(m)) {
637 /* Uplink of m is smaller if n->m is a backedge.
638 Propagate the uplink to mark the loop. */
639 if (get_irn_uplink(m) < get_irn_uplink(n))
640 set_irn_uplink(n, get_irn_uplink(m));
644 if (get_irn_dfn(n) == get_irn_uplink(n)) {
645 /* This condition holds for the node with the incoming backedge. */
646 ir_node *tail = find_tail(n);
648 /* We found a new loop! */
649 ir_loop *l = new_loop();
650 /* Remove the loop from the stack ... */
651 pop_scc_unmark_visit (n);
652 /* and recompute it in a better order; and so that it goes into
654 rem = find_irg_on_stack(tail);
656 current_ir_graph = rem;
658 assert (irn_visited(n));
667 /* Constructs backedge information for irg. In interprocedural view constructs
668 backedges for all methods called by irg, too. */
669 void construct_backedges(ir_graph *irg) {
670 ir_graph *rem = current_ir_graph;
674 assert(!interprocedural_view &&
675 "not implemented, use construct_ip_backedges");
677 current_ir_graph = irg;
678 outermost_ir_graph = irg;
683 new_loop(); /* sets current_loop */
684 head_rem = current_loop; /* Just for assertion */
686 if (interprocedural_view) {
687 set_irg_visited(irg, inc_max_irg_visited());
690 inc_irg_visited(irg);
693 scc(get_irg_end(irg));
694 for (i = 0; i < get_End_n_keepalives(get_irg_end(irg)); i++)
695 scc(get_End_keepalive(get_irg_end(irg), i));
697 if (interprocedural_view) finish_ip_walk();
699 assert(head_rem == current_loop);
700 set_irg_loop(irg, current_loop);
701 assert(get_irg_loop(irg)->kind == k_ir_loop);
703 irg->loops = current_loop;
707 count_loop (the_loop, &count, &depth);
711 current_ir_graph = rem;
716 void construct_ip_backedges () {
717 ir_graph *rem = current_ir_graph;
718 int rem_ipv = interprocedural_view;
721 outermost_ir_graph = get_irp_main_irg();
726 new_loop(); /* sets current_loop */
727 interprocedural_view = 1;
729 inc_max_irg_visited();
730 for (i = 0; i < get_irp_n_irgs(); i++)
731 set_irg_visited(get_irp_irg(i), get_max_irg_visited());
733 for (i = 0; i < get_irp_n_irgs(); i++) {
735 current_ir_graph = get_irp_irg(i);
736 //DDME(get_irg_ent(current_ir_graph));
737 /* Find real entry points */
738 sb = get_irg_start_block(current_ir_graph);
739 if ((get_Block_n_cfgpreds(sb) > 1) ||
740 (get_nodes_Block(get_Block_cfgpred(sb, 0)) != sb)) continue;
741 // printf("running scc for "); DDME(get_irg_ent(current_ir_graph));
742 /* Compute scc for this graph */
743 outermost_ir_graph = current_ir_graph;
744 set_irg_visited(outermost_ir_graph, get_max_irg_visited());
745 scc(get_irg_end(current_ir_graph));
746 for (j = 0; j < get_End_n_keepalives(get_irg_end(outermost_ir_graph)); j++)
747 scc(get_End_keepalive(get_irg_end(outermost_ir_graph), j));
750 set_irg_loop(outermost_ir_graph, current_loop);
751 assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
753 current_ir_graph = rem;
754 interprocedural_view = rem_ipv;