summaryrefslogtreecommitdiffhomepage
path: root/ir/ana/callgraph.c
blob: 2f4d8844d2885c73ef20f1d3b34838281f9f1406 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
/*
 * This file is part of libFirm.
 * Copyright (C) 2012 University of Karlsruhe.
 */

/**
 * @file
 * @brief       Representation and computation of the callgraph.
 * @author      Goetz Lindenmaier
 * @date        21.7.2004
 */
#include "callgraph.h"

#include "array.h"
#include "cgana.h"
#include "hashptr.h"
#include "irgraph_t.h"
#include "irgwalk.h"
#include "irloop_t.h"
#include "irnode_t.h"
#include "irprog_t.h"
#include "panic.h"
#include "pmap.h"
#include "raw_bitset.h"
#include "util.h"
#include <stdlib.h>

static ir_visited_t master_cg_visited = 0;

irp_callgraph_state get_irp_callgraph_state(void)
{
	return irp->callgraph_state;
}

void set_irp_callgraph_state(irp_callgraph_state s)
{
	irp->callgraph_state = s;
}

size_t get_irg_n_callers(const ir_graph *irg)
{
	assert(irg->callers != NULL);
	return irg->callers ? ARR_LEN(irg->callers) : 0;
}

ir_graph *get_irg_caller(const ir_graph *irg, size_t pos)
{
	assert(pos < get_irg_n_callers(irg));
	return irg->callers ? irg->callers[pos] : NULL;
}

int is_irg_caller_backedge(const ir_graph *irg, size_t pos)
{
	assert(pos < get_irg_n_callers(irg));
	return irg->caller_isbe != NULL ? rbitset_is_set(irg->caller_isbe, pos) : 0;
}

/** Search the caller in the list of all callers and set its backedge property. */
static void set_irg_caller_backedge(ir_graph *irg, const ir_graph *caller)
{
	/* allocate a new array on demand */
	size_t n_callers = get_irg_n_callers(irg);
	if (irg->caller_isbe == NULL)
		irg->caller_isbe = rbitset_malloc(n_callers);
	for (size_t i = 0; i < n_callers; ++i) {
		if (get_irg_caller(irg, i) == caller) {
			rbitset_set(irg->caller_isbe, i);
			break;
		}
	}
}

int has_irg_caller_backedge(const ir_graph *irg)
{
	if (irg->caller_isbe != NULL) {
		for (size_t i = 0, n_callers = get_irg_n_callers(irg);
		     i < n_callers; ++i)
			if (rbitset_is_set(irg->caller_isbe, i))
				return 1;
	}
	return 0;
}

/**
 * Find the reversion position of a caller.
 * Given the position pos_caller of an caller of irg, return
 * irg's callee position on that caller.
 */
static size_t reverse_pos(const ir_graph *callee, size_t pos_caller)
{
	ir_graph *caller = get_irg_caller(callee, pos_caller);
	/* search the other relation for the corresponding edge. */
	for (size_t i = 0, n_callees = get_irg_n_callees(caller);
	     i < n_callees; ++i) {
		if (get_irg_callee(caller, i) == callee) {
			return i;
		}
	}
	panic("reverse_pos() did not find position");
}

size_t get_irg_caller_loop_depth(const ir_graph *irg, size_t pos)
{
	ir_graph *caller     = get_irg_caller(irg, pos);
	size_t    pos_callee = reverse_pos(irg, pos);
	return get_irg_callee_loop_depth(caller, pos_callee);
}

size_t get_irg_n_callees(const ir_graph *irg)
{
	assert(irg->callees != NULL);
	return ARR_LEN(irg->callees);
}

ir_graph *get_irg_callee(const ir_graph *irg, size_t pos)
{
	assert(pos < get_irg_n_callees(irg));
	return irg->callees ? irg->callees[pos]->irg : NULL;
}

int is_irg_callee_backedge(const ir_graph *irg, size_t pos)
{
	assert(pos < get_irg_n_callees(irg));
	return irg->callee_isbe != NULL ? rbitset_is_set(irg->callee_isbe, pos) : 0;
}

int has_irg_callee_backedge(const ir_graph *irg)
{
	if (irg->callee_isbe != NULL) {
		for (size_t i = 0, n_callees = get_irg_n_callees(irg);
		     i < n_callees; ++i)
			if (rbitset_is_set(irg->callee_isbe, i))
				return 1;
	}
	return 0;
}

/**
 * Mark the callee at position pos as a backedge.
 */
static void set_irg_callee_backedge(ir_graph *irg, size_t pos)
{
	/* allocate a new array on demand */
	size_t n = get_irg_n_callees(irg);
	if (irg->callee_isbe == NULL)
		irg->callee_isbe = rbitset_malloc(n);
	assert(pos < n);
	rbitset_set(irg->callee_isbe, pos);
}

size_t get_irg_callee_loop_depth(const ir_graph *irg, size_t pos)
{
	assert(pos < get_irg_n_callees(irg));
	return irg->callees ? irg->callees[pos]->max_depth : 0;
}


/**
 * Pre-Walker called by compute_callgraph(), analyses all Call nodes.
 */
static void ana_Call(ir_node *n, void *env)
{
	(void)env;
	if (!is_Call(n))
		return;

	ir_graph *irg = get_irn_irg(n);
	for (size_t i = 0, n_callees = cg_get_call_n_callees(n); i < n_callees;
	     ++i) {
		ir_entity *callee_e = cg_get_call_callee(n, i);
		ir_graph  *callee   = get_entity_linktime_irg(callee_e);

		if (callee) {
			cg_callee_entry buf;
			buf.irg = callee;
			pset_insert((pset *)callee->callers, irg, hash_ptr(irg));
			cg_callee_entry *found = (cg_callee_entry*) pset_find((pset *)irg->callees, &buf, hash_ptr(callee));
			if (found) {  /* add Call node to list, compute new nesting. */
				ir_node **arr = found->call_list;
				ARR_APP1(ir_node *, arr, n);
				found->call_list = arr;
			} else { /* New node, add Call node and init nesting. */
				found = OALLOC(get_irg_obstack(irg), cg_callee_entry);
				found->irg = callee;
				found->call_list = NEW_ARR_F(ir_node *, 1);
				found->call_list[0] = n;
				found->max_depth = 0;
				pset_insert((pset *)irg->callees, found, hash_ptr(callee));
			}
			unsigned depth = get_loop_depth(get_irn_loop(get_nodes_block(n)));
			found->max_depth = MAX(found->max_depth, depth);
		}
	}
}

/** compare two ir graphs in a cg_callee_entry */
static int cg_callee_entry_cmp(const void *elt, const void *key)
{
	const cg_callee_entry *e1 = (const cg_callee_entry*) elt;
	const cg_callee_entry *e2 = (const cg_callee_entry*) key;
	return e1->irg != e2->irg;
}

/** compare two ir graphs for pointer identity */
static int graph_cmp(const void *elt, const void *key)
{
	const ir_graph *e1 = (const ir_graph*) elt;
	const ir_graph *e2 = (const ir_graph*) key;
	return e1 != e2;
}

void compute_callgraph(void)
{
	/* initialize */
	free_callgraph();

	foreach_irp_irg(i, irg) {
		assert(get_irg_callee_info_state(irg) == irg_callee_info_consistent);
		irg->callees = (cg_callee_entry **)new_pset(cg_callee_entry_cmp, 8);
		irg->callers = (ir_graph **)new_pset(graph_cmp, 8);
		//construct_cf_backedges(irg);
	}

	/* Compute the call graph */
	foreach_irp_irg(i, irg) {
		construct_cf_backedges(irg);   // We also find the maximal loop depth of a call.
		irg_walk_graph(irg, ana_Call, NULL, NULL);
	}

	/* Change the sets to arrays. */
	foreach_irp_irg(i, irg) {
		pset *callee_set = (pset *)irg->callees;
		size_t count = pset_count(callee_set);
		irg->callees = NEW_ARR_F(cg_callee_entry *, count);
		irg->callee_isbe = NULL;
		size_t j = 0;
		foreach_pset(callee_set, cg_callee_entry, callee) {
			irg->callees[j++] = callee;
		}
		del_pset(callee_set);
		assert(j == count);

		pset *caller_set = (pset *)irg->callers;
		count = pset_count(caller_set);
		irg->callers = NEW_ARR_F(ir_graph *, count);
		irg->caller_isbe =  NULL;
		j = 0;
		foreach_pset(caller_set, ir_graph, c) {
			irg->callers[j++] = c;
		}
		del_pset(caller_set);
		assert(j == count);
	}
	set_irp_callgraph_state(irp_callgraph_consistent);
}

void free_callgraph(void)
{
	foreach_irp_irg(i, irg) {
		if (irg->callees) DEL_ARR_F(irg->callees);
		if (irg->callers) DEL_ARR_F(irg->callers);
		if (irg->callee_isbe) free(irg->callee_isbe);
		if (irg->caller_isbe) free(irg->caller_isbe);
		irg->callees = NULL;
		irg->callers = NULL;
		irg->callee_isbe = NULL;
		irg->caller_isbe = NULL;
	}
	set_irp_callgraph_state(irp_callgraph_none);
}

/**
 * Returns non-zero if a graph was already visited.
 */
static inline int cg_irg_visited(ir_graph *irg)
{
	return irg->self_visited >= master_cg_visited;
}

/**
 * Marks a graph as visited.
 */
static inline void mark_cg_irg_visited(ir_graph *irg)
{
	irg->self_visited = master_cg_visited;
}

static void do_walk(ir_graph *irg, callgraph_walk_func *pre,
                    callgraph_walk_func *post, void *env)
{
	if (cg_irg_visited(irg))
		return;
	mark_cg_irg_visited(irg);

	if (pre != NULL)
		pre(irg, env);

	for (size_t i = 0, n_callees = get_irg_n_callees(irg); i < n_callees; i++) {
		ir_graph *m = get_irg_callee(irg, i);
		do_walk(m, pre, post, env);
	}

	if (post != NULL)
		post(irg, env);
}

void callgraph_walk(callgraph_walk_func *pre, callgraph_walk_func *post, void *env)
{
	++master_cg_visited;

	/* roots are methods which have no callers in the current program */
	foreach_irp_irg(i, irg) {
		if (get_irg_n_callers(irg) == 0)
			do_walk(irg, pre, post, env);
	}

	/* in case of unreachable call loops we haven't visited some irgs yet */
	foreach_irp_irg(i, irg) {
		do_walk(irg, pre, post, env);
	}
}

static ir_graph *outermost_ir_graph;   /**< The outermost graph the scc is computed
                                            for */
static ir_loop *current_loop;      /**< Current cfloop construction is working
                                        on. */
static size_t loop_node_cnt = 0;   /**< Counts the number of allocated cfloop nodes.
                                        Each cfloop node gets a unique number.
                                        What for? ev. remove. @@@ */
static size_t current_dfn = 1;     /**< Counter to generate depth first numbering
                                        of visited nodes.  */

typedef struct scc_info {
	size_t dfn;            /**< Depth first search number. */
	size_t uplink;         /**< dfn number of ancestor. */
	ir_visited_t visited;  /**< visited counter */
	int in_stack;          /**< Marks whether node is on the stack. */
} scc_info;

/**
 * allocates a new scc_info on the obstack
 */
static inline scc_info *new_scc_info(struct obstack *obst)
{
	return OALLOCZ(obst, scc_info);
}

/**
 * Set a graphs visited flag to i.
 */
static inline void set_cg_irg_visited(ir_graph *irg, ir_visited_t i)
{
	irg->self_visited = i;
}

static inline void mark_irg_in_stack(ir_graph *irg)
{
	scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	info->in_stack = 1;
}

static inline void mark_irg_not_in_stack(ir_graph *irg)
{
	scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	info->in_stack = 0;
}

static inline int irg_is_in_stack(const ir_graph *irg)
{
	scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	return info->in_stack;
}

static inline void set_irg_uplink(ir_graph *irg, size_t uplink)
{
	scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	info->uplink = uplink;
}

static inline size_t get_irg_uplink(const ir_graph *irg)
{
	const scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	return info->uplink;
}

static inline void set_irg_dfn(ir_graph *irg, size_t dfn)
{
	scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	info->dfn = dfn;
}

static inline size_t get_irg_dfn(const ir_graph *irg)
{
	const scc_info *info = (scc_info*) get_irg_link(irg);
	assert(info != NULL);
	return info->dfn;
}

static ir_graph **stack = NULL;
static size_t tos = 0;                /**< top of stack */

/**
 * Initialize the irg stack.
 */
static inline void init_stack(void)
{
	if (stack) {
		ARR_RESIZE(ir_graph *, stack, 1000);
	} else {
		stack = NEW_ARR_F(ir_graph *, 1000);
	}
	tos = 0;
}

/**
 * push a graph on the irg stack
 * @param n the graph to be pushed
 */
static inline void push(ir_graph *irg)
{
	if (tos == ARR_LEN(stack)) {
		size_t nlen = ARR_LEN(stack) * 2;
		ARR_RESIZE(ir_graph*, stack, nlen);
	}
	stack[tos++] = irg;
	mark_irg_in_stack(irg);
}

/**
 * return the topmost graph on the stack and pop it
 */
static inline ir_graph *pop(void)
{
	assert(tos > 0);
	ir_graph *irg = stack[--tos];
	mark_irg_not_in_stack(irg);
	return irg;
}

/**
 * The nodes up to irg belong to the current loop.
 * Removes them from the stack and adds them to the current loop.
 */
static inline void pop_scc_to_loop(ir_graph *irg)
{
	ir_graph *m;
	do {
		m = pop();
		++loop_node_cnt;
		set_irg_dfn(m, loop_node_cnt);
		add_loop_irg(current_loop, m);
		m->l = current_loop;
	} while (m != irg);
}

/* GL ??? my last son is my grandson???  Removes cfloops with no
   ir_nodes in them.  Such loops have only another loop as son. (Why
   can't they have two loops as sons? Does it never get that far? ) */
static void close_loop(ir_loop *l)
{
	size_t       last     = get_loop_n_elements(l) - 1;
	loop_element lelement = get_loop_element(l, last);
	ir_loop     *last_son = lelement.son;

	if (get_kind(last_son) == k_ir_loop && get_loop_n_elements(last_son) == 1) {

		lelement = get_loop_element(last_son, 0);
		ir_loop *gson = lelement.son;
		if (get_kind(gson) == k_ir_loop) {
			loop_element new_last_son;

			gson->outer_loop = l;
			new_last_son.son = gson;
			l->children[last] = new_last_son;
		}
	}
	current_loop = l;
}

/**
 * Removes and unmarks all nodes up to n from the stack.
 * The nodes must be visited once more to assign them to a scc.
 */
static inline void pop_scc_unmark_visit(ir_graph *n)
{
	ir_graph *m = NULL;
	while (m != n) {
		m = pop();
		set_cg_irg_visited(m, 0);
	}
}

/**
 * Allocates a new loop as son of current_loop.  Sets current_loop
 * to the new loop and returns the father.
 */
static ir_loop *new_loop(void)
{
	ir_loop *father = current_loop;
	ir_loop *son    = alloc_loop(father, get_irg_obstack(outermost_ir_graph));

	current_loop = son;
	return father;
}


static void init_scc(struct obstack *obst)
{
	current_dfn   = 1;
	loop_node_cnt = 0;
	init_stack();

	foreach_irp_irg(i, irg) {
		set_irg_link(irg, new_scc_info(obst));
	}
}

/** Returns non-zero if n is a loop header, i.e., it is a Block node
 *  and has predecessors within the cfloop and out of the cfloop.
 *
 *  @param root: only needed for assertion.
 */
static int is_head(const ir_graph *n, const ir_graph *root)
{
	bool some_outof_loop = false;
	bool some_in_loop    = false;

	for (size_t i = 0, n_callees = get_irg_n_callees(n); i < n_callees; ++i) {
		const ir_graph *pred = get_irg_callee(n, i);
		if (is_irg_callee_backedge(n, i)) continue;
		if (!irg_is_in_stack(pred)) {
			some_outof_loop = true;
		} else {
			if (get_irg_uplink(pred) < get_irg_uplink(root))  {
				assert(get_irg_uplink(pred) >= get_irg_uplink(root));
			}
			some_in_loop = true;
		}
	}

	return some_outof_loop && some_in_loop;
}

/**
 * Returns non-zero if n is possible loop head of an endless loop.
 * I.e., it is a Block or Phi node and has only predecessors
 * within the loop.
 * @arg root: only needed for assertion.
 */
static int is_endless_head(const ir_graph *n, const ir_graph *root)
{
	bool some_outof_loop = false;
	bool some_in_loop    = false;

	for (size_t i = 0, n_calless = get_irg_n_callees(n); i < n_calless; ++i) {
		const ir_graph *pred = get_irg_callee(n, i);
		assert(pred != NULL);
		if (is_irg_callee_backedge(n, i))
			continue;
		if (!irg_is_in_stack(pred)) {
			some_outof_loop = true;
		} else {
			if (get_irg_uplink(pred) < get_irg_uplink(root)) {
				assert(get_irg_uplink(pred) >= get_irg_uplink(root));
			}
			some_in_loop = true;
		}
	}
	return !some_outof_loop && some_in_loop;
}

/**
 * Finds index of the predecessor with the smallest dfn number
 * greater-equal than limit.
 */
static bool smallest_dfn_pred(const ir_graph *n, size_t limit, size_t *result)
{
	size_t index = 0;
	size_t min   = 0;
	bool   found = false;
	for (size_t i = 0, n_callees = get_irg_n_callees(n); i < n_callees; ++i) {
		const ir_graph *pred = get_irg_callee(n, i);
		if (is_irg_callee_backedge(n, i) || !irg_is_in_stack(pred))
			continue;
		if (get_irg_dfn(pred) >= limit && (!found || get_irg_dfn(pred) < min)) {
			index = i;
			min   = get_irg_dfn(pred);
			found = true;
		}
	}

	*result = index;
	return found;
}

/** Finds index of the predecessor with the largest dfn number. */
static bool largest_dfn_pred(const ir_graph *n, size_t *result)
{
	size_t index = 0;
	size_t max   = 0;
	bool   found = false;

	for (size_t i = 0, n_callees = get_irg_n_callees(n); i < n_callees; ++i) {
		const ir_graph *pred = get_irg_callee(n, i);
		if (is_irg_callee_backedge (n, i) || !irg_is_in_stack(pred))
			continue;
		/* Note: dfn is always > 0 */
		if (get_irg_dfn(pred) > max) {
			index = i;
			max   = get_irg_dfn(pred);
			found = true;
		}
	}

	*result = index;
	return found;
}

static ir_graph *find_tail(const ir_graph *n)
{
	/*
	if (!icfg && rm_cyclic_phis && remove_cyclic_phis (n)) return NULL;
	*/
	bool      found     = false;
	size_t    res_index = 0;
	ir_graph *m         = stack[tos - 1];  /* tos = top of stack */
	if (is_head(m, n)) {
		found = smallest_dfn_pred(m, 0, &res_index);
		if (!found &&  /* no smallest dfn pred found. */
			n == m)
			return NULL;
	} else {
		if (m == n)
			return NULL;    // Is this to catch Phi - self loops?
		for (size_t i = tos - 1; i > 0;) {
			m = stack[--i];

			if (is_head(m, n)) {
				found = smallest_dfn_pred(m, get_irg_dfn(m) + 1, &res_index);
				if (!found)  /* no smallest dfn pred found. */
					found = largest_dfn_pred(m, &res_index);

				break;
			}

			/* We should not walk past our selves on the stack:  The upcoming nodes
			   are not in this loop. We assume a loop not reachable from Start. */
			if (m == n) {
				found = false;
				break;
			}

		}

		if (!found) {
			/* A dead loop not reachable from Start. */
			for (size_t i = tos-1; i > 0;) {
				m = stack[--i];
				if (is_endless_head(m, n)) {
					found = smallest_dfn_pred(m, get_irg_dfn(m) + 1, &res_index);
					if (!found)  /* no smallest dfn pred found. */
						found = largest_dfn_pred(m, &res_index);
					break;
				}
				/* It's not an unreachable loop, either. */
				if (m == n)
					break;
			}
		}

	}
	assert(found);

	set_irg_callee_backedge(m, res_index);
	return get_irg_callee(m, res_index);
}

static void cgscc(ir_graph *n)
{
	if (cg_irg_visited(n))
		return;
	mark_cg_irg_visited(n);

	/* Initialize the node */
	set_irg_dfn(n, current_dfn);      /* Depth first number for this node */
	set_irg_uplink(n, current_dfn);   /* ... is default uplink. */
	++current_dfn;
	push(n);

	for (size_t i = 0, n_callees = get_irg_n_callees(n); i < n_callees; ++i) {
		if (is_irg_callee_backedge(n, i))
			continue;
		ir_graph *m = get_irg_callee(n, i);

		/** This marks the backedge, but does it guarantee a correct loop tree? */
		//if (m == n) { set_irg_callee_backedge(n, i); continue; }

		cgscc(m);
		if (irg_is_in_stack(m)) {
			/* Uplink of m is smaller if n->m is a backedge.
			   Propagate the uplink to mark the cfloop. */
			if (get_irg_uplink(m) < get_irg_uplink(n))
				set_irg_uplink(n, get_irg_uplink(m));
		}
	}

	if (get_irg_dfn(n) == get_irg_uplink(n)) {
		/* This condition holds for
		   1) the node with the incoming backedge.
		   That is: We found a cfloop!
		   2) Straight line code, because no uplink has been propagated, so the
		   uplink still is the same as the dfn.

		   But n might not be a proper cfloop head for the analysis. Proper cfloop
		   heads are Block and Phi nodes. find_tail searches the stack for
		   Block's and Phi's and takes those nodes as cfloop heads for the current
		   cfloop instead and marks the incoming edge as backedge. */

		ir_graph *tail = find_tail(n);
		if (tail) {
			/* We have a cfloop, that is no straight line code,
			   because we found a cfloop head!
			   Next actions: Open a new cfloop on the cfloop tree and
			   try to find inner cfloops */
			ir_loop *l = new_loop();

			/* Remove the cfloop from the stack ... */
			pop_scc_unmark_visit(n);

			/* The current backedge has been marked, that is temporarily eliminated,
			   by find tail. Start the scc algorithm
			   anew on the subgraph thats left (the current cfloop without the backedge)
			   in order to find more inner cfloops. */

			cgscc(tail);

			assert(cg_irg_visited(n));
			close_loop(l);
		} else {
			pop_scc_to_loop(n);
		}
	}
}


/**
 * reset the backedge information for all callers in all irgs
 */
static void reset_isbe(void)
{
	foreach_irp_irg(i, irg) {
		free(irg->caller_isbe);
		irg->caller_isbe = NULL;

		free(irg->callee_isbe);
		irg->callee_isbe = NULL;
	}
}

void find_callgraph_recursions(void)
{
	reset_isbe();

	/* -- compute the looptree. -- */

	/* The outermost graph.  We start here.  Then we start at all
	functions in irg list that are never called, then at the remaining
	unvisited ones. The third step is needed for functions that are not
	reachable from the outermost graph, but call themselves in a cycle. */
	assert(get_irp_main_irg());
	outermost_ir_graph = get_irp_main_irg();
	struct obstack temp;
	obstack_init(&temp);
	init_scc(&temp);

	current_loop = NULL;
	new_loop();  /* sets current_loop */

	++master_cg_visited;
	cgscc(outermost_ir_graph);
	foreach_irp_irg(i, irg) {
		if (!cg_irg_visited(irg) && get_irg_n_callers(irg) == 0)
			cgscc(irg);
	}
	foreach_irp_irg(i, irg) {
		if (!cg_irg_visited(irg))
			cgscc(irg);
	}
	obstack_free(&temp, NULL);

	irp->outermost_cg_loop = current_loop;
	mature_loops(current_loop, get_irg_obstack(outermost_ir_graph));

	/* -- Reverse the backedge information. -- */
	foreach_irp_irg(i, irg) {
		for (size_t j = 0, n_callees = get_irg_n_callees(irg); j < n_callees; ++j) {
			if (is_irg_callee_backedge(irg, j))
				set_irg_caller_backedge(get_irg_callee(irg, j), irg);
		}
	}

	irp->callgraph_state = irp_callgraph_and_calltree_consistent;
}

void analyse_loop_nesting_depth(void)
{
	/* establish preconditions. */
	if (get_irp_callee_info_state() != irg_callee_info_consistent) {
		ir_entity **free_methods = NULL;

		cgana(&free_methods);
		free(free_methods);
	}

	if (irp_callgraph_consistent != get_irp_callgraph_state()) {
		compute_callgraph();
	}

	find_callgraph_recursions();

	set_irp_loop_nesting_depth_state(loop_nesting_depth_consistent);
}

loop_nesting_depth_state get_irp_loop_nesting_depth_state(void)
{
	return irp->lnd_state;
}

void set_irp_loop_nesting_depth_state(loop_nesting_depth_state s)
{
	irp->lnd_state = s;
}

void set_irp_loop_nesting_depth_state_inconsistent(void)
{
	if (irp->lnd_state == loop_nesting_depth_consistent)
		irp->lnd_state = loop_nesting_depth_inconsistent;
}