jumpthreading.c 20 KB
Newer Older
Christian Würdig's avatar
Christian Würdig committed
1
/*
2
 * Copyright (C) 1995-2010 University of Karlsruhe.  All right reserved.
Christian Würdig's avatar
Christian Würdig committed
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

Michael Beck's avatar
Michael Beck committed
20
21
/**
 * @file
22
 * @brief   Path-Sensitive Jump Threading
Michael Beck's avatar
Michael Beck committed
23
24
 * @date    10. Sep. 2006
 * @author  Christoph Mallon, Matthias Braun
25
 */
26
27
#include "config.h"

28
29
#include "iroptimize.h"

30
#include <assert.h>
31
#include <stdbool.h>
32
#include "array_t.h"
33
34
#include "debug.h"
#include "ircons.h"
Christoph Mallon's avatar
Christoph Mallon committed
35
36
#include "irgmod.h"
#include "irgopt.h"
37
38
#include "irgwalk.h"
#include "irnode.h"
39
#include "irnode_t.h"
40
#include "iredges.h"
41
#include "iredges_t.h"
42
#include "irtools.h"
43
#include "irgraph.h"
44
#include "tv.h"
45
#include "iroptimize.h"
46
#include "iropt_dbg.h"
47
#include "irpass.h"
48
#include "vrp.h"
49
#include "firmstat_t.h"
50

51
#undef AVOID_PHIB
52

53
DEBUG_ONLY(static firm_dbg_module_t *dbg;)
54

Christoph Mallon's avatar
Christoph Mallon committed
55
56
57
58
59
60
61
/**
 * Add the new predecessor x to node node, which is either a Block or a Phi
 */
static void add_pred(ir_node* node, ir_node* x)
{
	ir_node** ins;

62
	int const n = get_Block_n_cfgpreds(node);
Christoph Mallon's avatar
Christoph Mallon committed
63
	NEW_ARR_A(ir_node*, ins, n + 1);
64
	for (int i = 0; i < n; i++)
65
		ins[i] = get_irn_n(node, i);
Christoph Mallon's avatar
Christoph Mallon committed
66
67
68
69
	ins[n] = x;
	set_irn_in(node, n + 1, ins);
}

70
71
72
73
74
static ir_node *ssa_second_def;
static ir_node *ssa_second_def_block;

static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode,
                                           int first)
Christoph Mallon's avatar
Christoph Mallon committed
75
{
76
77
78
79
80
	int i;
	int n_cfgpreds;
	ir_graph *irg;
	ir_node *phi;
	ir_node **in;
81
	ir_node *dummy;
82

83
84
	/* In case of a bad input to a block we need to return the bad value */
	if (is_Bad(block)) {
85
		ir_graph *irg = get_irn_irg(block);
Matthias Braun's avatar
Matthias Braun committed
86
		return new_r_Bad(irg, mode);
87
	}
88

89
90
91
	/* the other defs can't be marked for cases where a user of the original
	 * value is in the same block as the alternative definition.
	 * In this case we mustn't use the alternative definition.
Michael Beck's avatar
Michael Beck committed
92
	 * So we keep a flag that indicated whether we walked at least 1 block
93
94
95
96
97
	 * away and may use the alternative definition */
	if (block == ssa_second_def_block && !first) {
		return ssa_second_def;
	}

98
	/* already processed this block? */
99
	if (irn_visited(block)) {
100
101
102
103
		ir_node *value = (ir_node*) get_irn_link(block);
		return value;
	}

Matthias Braun's avatar
Matthias Braun committed
104
105
106
	irg = get_irn_irg(block);
	assert(block != get_irg_start_block(irg));

Christoph Mallon's avatar
Christoph Mallon committed
107
	/* a Block with only 1 predecessor needs no Phi */
108
	n_cfgpreds = get_Block_n_cfgpreds(block);
109
	if (n_cfgpreds == 1) {
110
		ir_node *pred_block = get_Block_cfgpred_block(block, 0);
111
		ir_node *value      = search_def_and_create_phis(pred_block, mode, 0);
112
113
114
115
116
117

		set_irn_link(block, value);
		mark_irn_visited(block);
		return value;
	}

118
	/* create a new Phi */
Christoph Mallon's avatar
Christoph Mallon committed
119
	NEW_ARR_A(ir_node*, in, n_cfgpreds);
120
	dummy = new_r_Dummy(irg, mode);
121
	for (i = 0; i < n_cfgpreds; ++i)
122
		in[i] = dummy;
123

124
	phi = new_r_Phi(block, n_cfgpreds, in, mode);
125
126
127
	set_irn_link(block, phi);
	mark_irn_visited(block);

128
	/* set Phi predecessors */
129
	for (i = 0; i < n_cfgpreds; ++i) {
130
		ir_node *pred_block = get_Block_cfgpred_block(block, i);
131
		ir_node *pred_val   = search_def_and_create_phis(pred_block, mode, 0);
132
133
134
135
136
137
138
139

		set_irn_n(phi, i, pred_val);
	}

	return phi;
}

/**
140
141
142
 * Given a set of values this function constructs SSA-form for the users of the
 * first value (the users are determined through the out-edges of the value).
 * Uses the irn_visited flags. Works without using the dominance tree.
143
 */
144
145
static void construct_ssa(ir_node *orig_block, ir_node *orig_val,
                          ir_node *second_block, ir_node *second_val)
Christoph Mallon's avatar
Christoph Mallon committed
146
{
147
148
149
	ir_graph *irg;
	ir_mode *mode;

150
151
152
153
	/* no need to do anything */
	if (orig_val == second_val)
		return;

154
	irg = get_irn_irg(orig_val);
155
156
	inc_irg_visited(irg);

157
158
159
	mode = get_irn_mode(orig_val);
	set_irn_link(orig_block, orig_val);
	mark_irn_visited(orig_block);
160

161
162
	ssa_second_def_block = second_block;
	ssa_second_def       = second_val;
163

164
	/* Only fix the users of the first, i.e. the original node */
165
	foreach_out_edge_safe(orig_val, edge) {
166
167
168
169
		ir_node *user = get_edge_src_irn(edge);
		int j = get_edge_src_pos(edge);
		ir_node *user_block = get_nodes_block(user);
		ir_node *newval;
170

171
172
		/* ignore keeps */
		if (is_End(user))
173
			continue;
174
175
176

		DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));

177
		if (is_Phi(user)) {
178
			ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
179
			newval = search_def_and_create_phis(pred_block, mode, 1);
180
		} else {
181
			newval = search_def_and_create_phis(user_block, mode, 1);
182
183
		}

184
		/* don't fix newly created Phis from the SSA construction */
185
186
187
		if (newval != user) {
			DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
			set_irn_n(user, j, newval);
188
189
190
191
		}
	}
}

192
193
194
195
196
197
198
199
200
201
/**
 * jumpthreading produces critical edges, e.g. B-C:
 *     A         A
 *  \ /       \  |
 *   B    =>   B |
 *  / \       / \|
 *     C         C
 *
 * By splitting this critical edge more threadings might be possible.
 */
202
203
204
205
206
207
208
209
210
211
212
213
214
static void split_critical_edge(ir_node *block, int pos)
{
	ir_graph *irg = get_irn_irg(block);
	ir_node *in[1];
	ir_node *new_block;
	ir_node *new_jmp;

	in[0] = get_Block_cfgpred(block, pos);
	new_block = new_r_Block(irg, 1, in);
	new_jmp = new_r_Jmp(new_block);
	set_Block_cfgpred(block, pos, new_jmp);
}

215
typedef struct jumpthreading_env_t {
216
	ir_node       *true_block;
217
	ir_node       *cmp;        /**< The Compare node that might be partial evaluated */
218
	ir_relation    relation;   /**< The Compare mode of the Compare node. */
219
	ir_node       *cnst;
Matthias Braun's avatar
Matthias Braun committed
220
	ir_tarval     *tv;
221
	ir_visited_t   visited_nr;
222
223
224
225

	ir_node       *cnst_pred;   /**< the block before the constant */
	int            cnst_pos;    /**< the pos to the constant block (needed to
	                                  kill that edge later) */
226
} jumpthreading_env_t;
Christoph Mallon's avatar
Christoph Mallon committed
227

228
229
230
231
static ir_node *copy_and_fix_node(const jumpthreading_env_t *env,
                                  ir_node *block, ir_node *copy_block, int j,
                                  ir_node *node)
{
Matthias Braun's avatar
Matthias Braun committed
232
233
234
235
236
237
	int      i, arity;
	ir_node *copy;

	/* we can evaluate Phis right now, all other nodes get copied */
	if (is_Phi(node)) {
		copy = get_Phi_pred(node, j);
238
		/* we might have to evaluate a Phi-cascade */
239
		if (get_irn_visited(copy) >= env->visited_nr) {
240
			copy = (ir_node*)get_irn_link(copy);
Matthias Braun's avatar
Matthias Braun committed
241
242
243
244
245
246
247
248
		}
	} else {
		copy = exact_copy(node);
		set_nodes_block(copy, copy_block);

		assert(get_irn_mode(copy) != mode_X);

		arity = get_irn_arity(copy);
249
		for (i = 0; i < arity; ++i) {
Matthias Braun's avatar
Matthias Braun committed
250
251
252
			ir_node *pred     = get_irn_n(copy, i);
			ir_node *new_pred;

253
			if (get_nodes_block(pred) != block)
Matthias Braun's avatar
Matthias Braun committed
254
255
				continue;

256
			if (get_irn_visited(pred) >= env->visited_nr) {
257
				new_pred = (ir_node*)get_irn_link(pred);
Matthias Braun's avatar
Matthias Braun committed
258
259
260
			} else {
				new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
			}
261
			DB((dbg, LEVEL_2, ">> Set Pred of %+F to %+F\n", copy, new_pred));
Matthias Braun's avatar
Matthias Braun committed
262
263
264
265
266
267
268
269
270
271
			set_irn_n(copy, i, new_pred);
		}
	}

	set_irn_link(node, copy);
	set_irn_visited(node, env->visited_nr);

	return copy;
}

272
273
274
static void copy_and_fix(const jumpthreading_env_t *env, ir_node *block,
                         ir_node *copy_block, int j)
{
275
276
277
278
	/* Look at all nodes in the cond_block and copy them into pred */
	foreach_out_edge(block, edge) {
		ir_node *node = get_edge_src_irn(edge);
		ir_node *copy;
279
280
		ir_mode *mode;

Andreas Zwinkau's avatar
Andreas Zwinkau committed
281
		if (is_End(node)) {
282
283
			/* edge is a Keep edge. If the end block is unreachable via normal
			 * control flow, we must maintain end's reachability with Keeps.
Andreas Zwinkau's avatar
Andreas Zwinkau committed
284
285
286
287
			 */
			keep_alive(copy_block);
			continue;
		}
288
		/* ignore control flow */
289
		mode = get_irn_mode(node);
Matthias Braun's avatar
Matthias Braun committed
290
		if (mode == mode_X || is_Cond(node) || is_Switch(node))
291
			continue;
292
#ifdef AVOID_PHIB
293
		/* we may not copy mode_b nodes, because this could produce Phi with
294
		 * mode_bs which can't be handled in all backends. Instead we duplicate
Christoph Mallon's avatar
Christoph Mallon committed
295
		 * the node and move it to its users */
296
		if (mode == mode_b) {
297
298
			ir_node *const pred = get_Proj_pred(node);
			long     const pn   = get_Proj_proj(node);
299

300
			foreach_out_edge_safe(node, edge) {
301
302
303
304
305
				ir_node *cmp_copy;
				ir_node *user       = get_edge_src_irn(edge);
				int pos             = get_edge_src_pos(edge);
				ir_node *user_block = get_nodes_block(user);

306
				if (user_block == block)
307
308
309
310
					continue;

				cmp_copy = exact_copy(pred);
				set_nodes_block(cmp_copy, user_block);
311
				copy = new_r_Proj(cmp_copy, mode_b, pn);
312
313
314
315
				set_irn_n(user, pos, copy);
			}
			continue;
		}
316
#endif
Christoph Mallon's avatar
Christoph Mallon committed
317

Matthias Braun's avatar
Matthias Braun committed
318
		copy = copy_and_fix_node(env, block, copy_block, j, node);
319
320

		/* we might hit values in blocks that have already been processed by a
321
		 * recursive find_phi_with_const() call */
322
		assert(get_irn_visited(copy) <= env->visited_nr);
323
		if (get_irn_visited(copy) >= env->visited_nr) {
324
			ir_node *prev_copy = (ir_node*)get_irn_link(copy);
325
			if (prev_copy != NULL)
326
327
328
				set_irn_link(node, prev_copy);
		}
	}
Christoph Mallon's avatar
Christoph Mallon committed
329

330
331
332
	/* fix data-flow (and reconstruct SSA if needed) */
	foreach_out_edge(block, edge) {
		ir_node *node = get_edge_src_irn(edge);
333
		ir_node *copy_node;
334
335
336
		ir_mode *mode;

		mode = get_irn_mode(node);
Matthias Braun's avatar
Matthias Braun committed
337
		if (mode == mode_X || is_Cond(node) || is_Switch(node))
338
			continue;
339
#ifdef AVOID_PHIB
340
		if (mode == mode_b)
341
			continue;
342
#endif
343

344
345
		DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));

346
		copy_node = (ir_node*)get_irn_link(node);
347
		construct_ssa(block, node, copy_block, copy_node);
348
	}
349
350
351
352
353
354
355
356
357
358
359

	/* make sure new nodes are kept alive if old nodes were */
	ir_graph *irg = get_irn_irg(block);
	ir_node  *end = get_irg_end(irg);
	for (int i = 0, arity = get_End_n_keepalives(end); i < arity; ++i) {
		ir_node *keep = get_End_keepalive(end, i);
		if (get_irn_visited(keep) < env->visited_nr || is_Block(keep))
			continue;
		ir_node *copy = get_irn_link(keep);
		add_End_keepalive(end, copy);
	}
360
361
}

362
/**
Michael Beck's avatar
Michael Beck committed
363
 * returns whether the cmp evaluates to true or false, or can't be evaluated!
364
 * 1: true, 0: false, -1: can't evaluate
365
 *
366
 * @param relation  the compare mode of the Compare
367
368
 * @param tv_left   the left tarval
 * @param tv_right  the right tarval
369
 */
370
371
static int eval_cmp_tv(ir_relation relation, ir_tarval *tv_left,
                       ir_tarval *tv_right)
372
{
373
	ir_relation cmp_result = tarval_cmp(tv_left, tv_right);
374

375
	/* does the compare evaluate to true? */
376
	if (cmp_result == ir_relation_false)
377
		return -1;
378
379
	if ((cmp_result & relation) != 0)
		return 1;
380

381
	return 0;
382
383
}

384
385
386
#if 0
/* Matze: disabled, check first if the compare still is correct */

387
388
389
390
391
/**
 * returns whether the cmp evaluates to true or false according to vrp
 * information , or can't be evaluated!
 * 1: true, 0: false, -1: can't evaluate
 *
392
393
394
 * @param relation  the compare mode of the Compare
 * @param left      the left node
 * @param right     the right node
395
 */
396
static int eval_cmp_vrp(ir_relation relation, ir_node *left, ir_node *right)
397
{
398
	ir_relation cmp_result = vrp_cmp(left, right);
399
	/* does the compare evaluate to true? */
400
	if (cmp_result == ir_relation_false)
401
		return -1;
402
403
404

	if ((cmp_result & relation) != cmp_result) {
		if ((cmp_result & relation) != 0) {
405
406
			return -1;
		}
407
		return 0;
408
	}
409
410
	return 1;
}
411
412
#endif

413
/**
414
415
416
417
418
 * returns whether the cmp evaluates to true or false, or can't be evaluated!
 * 1: true, 0: false, -1: can't evaluate
 *
 * @param env      the environment
 * @param cand     the candidate node, either a Const or a Confirm
419
 */
420
421
static int eval_cmp(jumpthreading_env_t *env, ir_node *cand)
{
422
	if (is_Const(cand)) {
423
424
		ir_tarval *tv_cand = get_Const_tarval(cand);
		ir_tarval *tv_cmp  = get_Const_tarval(env->cnst);
425

426
		return eval_cmp_tv(env->relation, tv_cand, tv_cmp);
427
	} else { /* a Confirm */
428
		ir_tarval *res = computed_value_Cmp_Confirm(env->cmp, cand, env->cnst, env->relation);
429
430
431
432

		if (res == tarval_bad)
			return -1;
		return res == tarval_b_true;
433
	}
434
435
436
437
438
}

/**
 * Check for Const or Confirm with Const.
 */
439
440
static int is_Const_or_Confirm(const ir_node *node)
{
441
442
	if (is_Confirm(node))
		node = get_Confirm_bound(node);
443
444
445
446
	return is_Const(node);
}

/**
447
 * get the tarval of a Const or Confirm with
448
 */
Matthias Braun's avatar
Matthias Braun committed
449
static ir_tarval *get_Const_or_Confirm_tarval(const ir_node *node)
450
{
451
	if (is_Confirm(node)) {
452
		if (get_Confirm_bound(node))
453
454
455
456
457
			node = get_Confirm_bound(node);
	}
	return get_Const_tarval(node);
}

458
459
static ir_node *find_const_or_confirm(jumpthreading_env_t *env, ir_node *jump,
                                      ir_node *value)
460
{
461
462
	ir_node *block = get_nodes_block(jump);

463
	if (irn_visited_else_mark(value))
464
465
		return NULL;

466
	if (is_Const_or_Confirm(value)) {
467
		if (eval_cmp(env, value) <= 0)
468
			return NULL;
Christoph Mallon's avatar
Christoph Mallon committed
469
470
471

		DB((
			dbg, LEVEL_1,
yb9976's avatar
yb9976 committed
472
			"> Found jump threading candidate %+F->%+F\n",
473
			block, env->true_block
Christoph Mallon's avatar
Christoph Mallon committed
474
475
		));

476
		/* adjust true_block to point directly towards our jump */
477
		add_pred(env->true_block, jump);
478

479
480
		split_critical_edge(env->true_block, 0);

481
		/* we need a bigger visited nr when going back */
482
		env->visited_nr++;
483

484
485
		return block;
	}
486

487
	if (is_Phi(value)) {
488
		int i, arity;
Christoph Mallon's avatar
Christoph Mallon committed
489

490
		/* the Phi has to be in the same Block as the Jmp */
491
		if (get_nodes_block(value) != block)
492
			return NULL;
493

494
		arity = get_irn_arity(value);
495
		for (i = 0; i < arity; ++i) {
496
497
			ir_node *copy_block;
			ir_node *phi_pred = get_Phi_pred(value, i);
498
			ir_node *cfgpred  = get_Block_cfgpred(block, i);
499

500
			copy_block = find_const_or_confirm(env, cfgpred, phi_pred);
501
			if (copy_block == NULL)
502
503
				continue;

504
			/* copy duplicated nodes in copy_block and fix SSA */
505
			copy_and_fix(env, block, copy_block, i);
506

507
			if (copy_block == get_nodes_block(cfgpred)) {
508
				env->cnst_pred = block;
509
				env->cnst_pos  = i;
510
			}
511

512
			/* return now as we can't process more possibilities in 1 run */
513
			return copy_block;
514
		}
Christoph Mallon's avatar
Christoph Mallon committed
515
	}
516

517
	return NULL;
Christoph Mallon's avatar
Christoph Mallon committed
518
519
}

520
static ir_node *find_candidate(jumpthreading_env_t *env, ir_node *jump,
521
                               ir_node *value)
522
{
523
524
	ir_node *block = get_nodes_block(jump);

525
	if (irn_visited_else_mark(value)) {
526
		return NULL;
527
	}
528

529
	if (is_Const_or_Confirm(value)) {
Matthias Braun's avatar
Matthias Braun committed
530
		ir_tarval *tv = get_Const_or_Confirm_tarval(value);
531

532
		if (tv != env->tv)
533
534
535
536
			return NULL;

		DB((
			dbg, LEVEL_1,
yb9976's avatar
yb9976 committed
537
			"> Found jump threading candidate %+F->%+F\n",
538
			block, env->true_block
539
540
		));

541
		/* adjust true_block to point directly towards our jump */
542
543
		add_pred(env->true_block, jump);

544
545
		split_critical_edge(env->true_block, 0);

546
		/* we need a bigger visited nr when going back */
547
		env->visited_nr++;
548

549
		return block;
550
	}
551
	if (is_Phi(value)) {
552
		int i, arity;
553

554
		/* the Phi has to be in the same Block as the Jmp */
555
		if (get_nodes_block(value) != block)
556
			return NULL;
557

558
		arity = get_irn_arity(value);
559
		for (i = 0; i < arity; ++i) {
560
561
562
			ir_node *copy_block;
			ir_node *phi_pred = get_Phi_pred(value, i);
			ir_node *cfgpred  = get_Block_cfgpred(block, i);
563

564
			copy_block = find_candidate(env, cfgpred, phi_pred);
565
			if (copy_block == NULL)
566
567
568
569
570
				continue;

			/* copy duplicated nodes in copy_block and fix SSA */
			copy_and_fix(env, block, copy_block, i);

571
			if (copy_block == get_nodes_block(cfgpred)) {
572
573
574
575
				env->cnst_pred = block;
				env->cnst_pos  = i;
			}

576
			/* return now as we can't process more possibilities in 1 run */
577
			return copy_block;
Christoph Mallon's avatar
Christoph Mallon committed
578
		}
579
	}
580
581
582
583
584
	if (is_Cmp(value)) {
		ir_node    *cmp      = value;
		ir_node    *left     = get_Cmp_left(cmp);
		ir_node    *right    = get_Cmp_right(cmp);
		ir_relation relation = get_Cmp_relation(cmp);
585

586
587
		/* we assume that the constant is on the right side, swap left/right
		 * if needed */
588
		if (is_Const(left)) {
589
590
591
			ir_node *t = left;
			left       = right;
			right      = t;
592

593
			relation   = get_inversed_relation(relation);
594
		}
595

596
		if (!is_Const(right))
597
			return NULL;
598

599
600
		if (get_nodes_block(left) != block)
			return NULL;
601

602
		/* negate condition when we're looking for the false block */
603
		if (env->tv == tarval_b_false) {
604
			relation = get_negated_relation(relation);
605
		}
606

607
		/* (recursively) look if a pred of a Phi is a constant or a Confirm */
608
609
610
		env->cmp      = cmp;
		env->relation = relation;
		env->cnst     = right;
611

612
		return find_const_or_confirm(env, jump, left);
613
	}
614

615
616
	return NULL;
}
617
618
619
620
621
622
623
624
625
626
627
628
629
630

/**
 * Block-walker: searches for the following construct
 *
 *  Const or Phi with constants
 *           |
 *          Cmp
 *           |
 *         Cond
 *          /
 *       ProjX
 *        /
 *     Block
 */
631
static void thread_jumps(ir_node* block, void* data)
632
{
633
	jumpthreading_env_t env;
634
	bool *changed = (bool*)data;
635
	ir_node *selector;
636
637
	ir_node *projx;
	ir_node *cond;
638
	ir_node *copy_block;
639
	int      selector_evaluated;
640
	ir_graph *irg;
Matthias Braun's avatar
Matthias Braun committed
641
	ir_node *badX;
642
	int      cnst_pos;
643

644
	/* we do not deal with Phis, so restrict this to exactly one cfgpred */
645
	if (get_Block_n_cfgpreds(block) != 1)
646
647
648
649
650
651
652
653
		return;

	projx = get_Block_cfgpred(block, 0);
	if (!is_Proj(projx))
		return;
	assert(get_irn_mode(projx) == mode_X);

	cond = get_Proj_pred(projx);
654
	/* TODO handle switch Conds */
Matthias Braun's avatar
Matthias Braun committed
655
	if (!is_Cond(cond))
656
		return;
657

Michael Beck's avatar
Michael Beck committed
658
	/* handle cases that can be immediately evaluated */
Matthias Braun's avatar
Matthias Braun committed
659
	selector = get_Cond_selector(cond);
660
	selector_evaluated = -1;
661
662
663
664
665
666
667
668
669
	if (is_Cmp(selector)) {
		ir_node *left  = get_Cmp_left(selector);
		ir_node *right = get_Cmp_right(selector);
		if (is_Const(left) && is_Const(right)) {
			ir_relation relation = get_Cmp_relation(selector);
			ir_tarval  *tv_left  = get_Const_tarval(left);
			ir_tarval  *tv_right = get_Const_tarval(right);

			selector_evaluated = eval_cmp_tv(relation, tv_left, tv_right);
670
		}
671
672
673
674
675
676
677
678
679
#if 0
		if (selector_evaluated < 0) {
			/* This is only the case if the predecessor nodes are not
			 * constant or the comparison could not be evaluated.
			 * Try with VRP information now.
			 */
			selector_evaluated = eval_cmp_vrp(relation, left, right);
		}
#endif
680
	} else if (is_Const_or_Confirm(selector)) {
Matthias Braun's avatar
Matthias Braun committed
681
		ir_tarval *tv = get_Const_or_Confirm_tarval(selector);
682
		if (tv == tarval_b_true) {
683
684
			selector_evaluated = 1;
		} else {
685
			assert(tv == tarval_b_false);
686
687
688
689
690
			selector_evaluated = 0;
		}
	}

	env.cnst_pred = NULL;
691
	if (get_Proj_proj(projx) == pn_Cond_false) {
692
		env.tv = tarval_b_false;
693
		if (selector_evaluated >= 0)
694
			selector_evaluated = !selector_evaluated;
695
	} else {
696
		env.tv = tarval_b_true;
697
698
	}

699
	if (selector_evaluated == 0) {
700
		ir_graph *irg = get_irn_irg(block);
Matthias Braun's avatar
Matthias Braun committed
701
		ir_node  *bad = new_r_Bad(irg, mode_X);
702
		exchange(projx, bad);
703
		*changed = true;
704
		return;
705
	} else if (selector_evaluated == 1) {
706
		dbg_info *dbgi = get_irn_dbg_info(selector);
707
		ir_node  *jmp  = new_rd_Jmp(dbgi, get_nodes_block(projx));
yb9976's avatar
yb9976 committed
708
		DBG_OPT_JUMPTHREADING(projx, jmp);
709
		exchange(projx, jmp);
710
		*changed = true;
711
712
713
		return;
	}

714
	/* (recursively) look if a pred of a Phi is a constant or a Confirm */
715
	env.true_block = block;
716
717
718
	irg = get_irn_irg(block);
	inc_irg_visited(irg);
	env.visited_nr = get_irg_visited(irg);
719
720
721

	copy_block = find_candidate(&env, projx, selector);
	if (copy_block == NULL)
722
723
		return;

Andreas Zwinkau's avatar
Andreas Zwinkau committed
724
725
726
727
	/* We might thread the condition block of an infinite loop,
	 * such that there is no path to End anymore. */
	keep_alive(block);

728
	/* we have to remove the edge towards the pred as the pred now
729
	 * jumps into the true_block. We also have to shorten Phis
730
	 * in our block because of this */
Matthias Braun's avatar
Matthias Braun committed
731
	badX     = new_r_Bad(irg, mode_X);
732
733
	cnst_pos = env.cnst_pos;

734
	/* shorten Phis */
735
	foreach_out_edge_safe(env.cnst_pred, edge) {
736
737
		ir_node *node = get_edge_src_irn(edge);

Matthias Braun's avatar
Matthias Braun committed
738
739
		if (is_Phi(node)) {
			ir_node *bad = new_r_Bad(irg, get_irn_mode(node));
740
			set_Phi_pred(node, cnst_pos, bad);
Matthias Braun's avatar
Matthias Braun committed
741
		}
742
743
	}

Matthias Braun's avatar
Matthias Braun committed
744
	set_Block_cfgpred(env.cnst_pred, cnst_pos, badX);
745
746

	/* the graph is changed now */
747
	*changed = true;
748
749
}

750
void opt_jumpthreading(ir_graph* irg)
751
{
752
753
754
755
756
757
758
	bool changed;
	bool rerun;

	assure_irg_properties(irg,
		IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE
		| IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
		| IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
759

760
	FIRM_DBG_REGISTER(dbg, "firm.opt.jumpthreading");
761

762
	DB((dbg, LEVEL_1, "===> Performing jumpthreading on %+F\n", irg));
763

764
	ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
765

766
	changed = false;
767
	do {
768
		rerun = false;
769
		irg_block_walk_graph(irg, thread_jumps, NULL, &rerun);
Michael Beck's avatar
Michael Beck committed
770
771
772
		changed |= rerun;
	} while (rerun);

773
	ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
774

775
776
	confirm_irg_properties(irg,
		changed ? IR_GRAPH_PROPERTIES_NONE : IR_GRAPH_PROPERTIES_ALL);
777
}
778
779

/* Creates an ir_graph pass for opt_jumpthreading. */
780
ir_graph_pass_t *opt_jumpthreading_pass(const char *name)
781
{
782
	return def_graph_pass(name ? name : "jumpthreading", opt_jumpthreading);
783
}