jumpthreading.c 18.4 KB
Newer Older
Christian Würdig's avatar
Christian Würdig committed
1
2
/*
 * This file is part of libFirm.
3
 * Copyright (C) 2012 University of Karlsruhe.
Christian Würdig's avatar
Christian Würdig committed
4
5
 */

Michael Beck's avatar
Michael Beck committed
6
7
/**
 * @file
8
 * @brief   Path-Sensitive Jump Threading
Michael Beck's avatar
Michael Beck committed
9
10
 * @date    10. Sep. 2006
 * @author  Christoph Mallon, Matthias Braun
11
 */
12
13
#include "iroptimize.h"

14
#include <assert.h>
15
#include <stdbool.h>
16
#include "array.h"
17
18
#include "debug.h"
#include "ircons.h"
Christoph Mallon's avatar
Christoph Mallon committed
19
20
#include "irgmod.h"
#include "irgopt.h"
21
22
#include "irgwalk.h"
#include "irnode.h"
23
#include "irnode_t.h"
24
#include "iredges.h"
25
#include "iredges_t.h"
26
#include "irtools.h"
27
#include "tv.h"
28
#include "iroptimize.h"
29
#include "iropt_dbg.h"
30
#include "vrp.h"
31
#include "firmstat_t.h"
32

33
#undef AVOID_PHIB
34

35
DEBUG_ONLY(static firm_dbg_module_t *dbg;)
36

Christoph Mallon's avatar
Christoph Mallon committed
37
38
39
/**
 * Add the new predecessor x to node node, which is either a Block or a Phi
 */
Matthias Braun's avatar
Matthias Braun committed
40
static void add_pred(ir_node *node, ir_node *x)
Christoph Mallon's avatar
Christoph Mallon committed
41
{
Matthias Braun's avatar
Matthias Braun committed
42
43
44
	int        const n   = get_Block_n_cfgpreds(node);
	ir_node  **const ins = ALLOCAN(ir_node*, n+1);
	foreach_irn_in(node, i, pred) {
45
		ins[i] = pred;
Matthias Braun's avatar
Matthias Braun committed
46
	}
Christoph Mallon's avatar
Christoph Mallon committed
47
48
49
50
	ins[n] = x;
	set_irn_in(node, n + 1, ins);
}

51
52
53
54
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,
Matthias Braun's avatar
Matthias Braun committed
55
                                           bool first)
Christoph Mallon's avatar
Christoph Mallon committed
56
{
57
	assert(is_Block(block));
58

59
60
61
	/* 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
62
	 * So we keep a flag that indicated whether we walked at least 1 block
63
	 * away and may use the alternative definition */
Matthias Braun's avatar
Matthias Braun committed
64
	if (block == ssa_second_def_block && !first)
65
66
		return ssa_second_def;

67
	/* already processed this block? */
68
	if (irn_visited(block)) {
69
70
71
72
		ir_node *value = (ir_node*) get_irn_link(block);
		return value;
	}

Matthias Braun's avatar
Matthias Braun committed
73
	ir_graph *irg = get_irn_irg(block);
Matthias Braun's avatar
Matthias Braun committed
74
75
	assert(block != get_irg_start_block(irg));

Christoph Mallon's avatar
Christoph Mallon committed
76
	/* a Block with only 1 predecessor needs no Phi */
Matthias Braun's avatar
Matthias Braun committed
77
	int n_cfgpreds = get_Block_n_cfgpreds(block);
78
	if (n_cfgpreds == 1) {
79
		ir_node *pred_block = get_Block_cfgpred_block(block, 0);
80
81
82
83
84
85
86
		ir_node *value;
		if (pred_block == NULL) {
			ir_graph *irg = get_irn_irg(block);
			value = new_r_Bad(irg, mode);
		} else {
			value = search_def_and_create_phis(pred_block, mode, false);
		}
87
88
89
90
91
		set_irn_link(block, value);
		mark_irn_visited(block);
		return value;
	}

92
	/* create a new Phi */
Matthias Braun's avatar
Matthias Braun committed
93
94
	ir_node **in    = ALLOCAN(ir_node*, n_cfgpreds);
	ir_node  *dummy = new_r_Dummy(irg, mode);
Matthias Braun's avatar
Matthias Braun committed
95
	for (int i = 0; i < n_cfgpreds; ++i) {
96
		in[i] = dummy;
Matthias Braun's avatar
Matthias Braun committed
97
	}
98

Matthias Braun's avatar
Matthias Braun committed
99
	ir_node *phi = new_r_Phi(block, n_cfgpreds, in, mode);
100
101
102
	set_irn_link(block, phi);
	mark_irn_visited(block);

103
	/* set Phi predecessors */
Matthias Braun's avatar
Matthias Braun committed
104
	for (int i = 0; i < n_cfgpreds; ++i) {
105
		ir_node *pred_block = get_Block_cfgpred_block(block, i);
106
107
108
109
110
111
112
		ir_node *pred_val;
		if (pred_block == NULL) {
			ir_graph *irg = get_irn_irg(block);
			pred_val = new_r_Bad(irg, mode);
		} else {
			pred_val = search_def_and_create_phis(pred_block, mode, false);
		}
113
114
		set_irn_n(phi, i, pred_val);
	}
115
116
117
	/* we might have created a potential endless loop, so keep the Phi */
	if (get_irn_mode(phi) == mode_M)
		keep_alive(phi);
118
119
120
121
122

	return phi;
}

/**
123
124
125
 * 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.
126
 */
127
128
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
129
{
130
131
132
133
	/* no need to do anything */
	if (orig_val == second_val)
		return;

Matthias Braun's avatar
Matthias Braun committed
134
	ir_graph *irg = get_irn_irg(orig_val);
135
136
	inc_irg_visited(irg);

Matthias Braun's avatar
Matthias Braun committed
137
	ir_mode *mode = get_irn_mode(orig_val);
138
139
	set_irn_link(orig_block, orig_val);
	mark_irn_visited(orig_block);
140

141
142
	ssa_second_def_block = second_block;
	ssa_second_def       = second_val;
143

144
	/* Only fix the users of the first, i.e. the original node */
145
	foreach_out_edge_safe(orig_val, edge) {
146
		ir_node *user = get_edge_src_irn(edge);
147
148
		/* ignore keeps */
		if (is_End(user))
149
			continue;
150

Matthias Braun's avatar
Matthias Braun committed
151
152
153
		int j = get_edge_src_pos(edge);
		DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j,
		    get_irn_n(user, j)));
154

Matthias Braun's avatar
Matthias Braun committed
155
156
		ir_node *user_block = get_nodes_block(user);
		ir_node *newval;
157
		if (is_Phi(user)) {
158
			ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
159
160
161
162
163
164
			if (pred_block == NULL) {
				ir_graph *irg = get_irn_irg(user_block);
				newval = new_r_Bad(irg, mode);
			} else {
				newval = search_def_and_create_phis(pred_block, mode, true);
			}
165
		} else {
Matthias Braun's avatar
Matthias Braun committed
166
			newval = search_def_and_create_phis(user_block, mode, true);
167
168
		}

169
		/* don't fix newly created Phis from the SSA construction */
170
		if (newval != user) {
Matthias Braun's avatar
Matthias Braun committed
171
172
			DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user,
			    newval));
173
			set_irn_n(user, j, newval);
174
175
176
177
		}
	}
}

178
179
180
181
182
183
184
185
186
187
/**
 * jumpthreading produces critical edges, e.g. B-C:
 *     A         A
 *  \ /       \  |
 *   B    =>   B |
 *  / \       / \|
 *     C         C
 *
 * By splitting this critical edge more threadings might be possible.
 */
188
189
static void split_critical_edge(ir_node *block, int pos)
{
Matthias Braun's avatar
Matthias Braun committed
190
191
192
193
	ir_graph *irg       = get_irn_irg(block);
	ir_node  *in[]      = { get_Block_cfgpred(block, pos) };
	ir_node  *new_block = new_r_Block(irg, ARRAY_SIZE(in), in);
	ir_node  *new_jmp   = new_r_Jmp(new_block);
194
195
196
	set_Block_cfgpred(block, pos, new_jmp);
}

197
typedef struct jumpthreading_env_t {
198
199
200
201
	ir_node      *true_block;  /**< Block we try to thread into */
	ir_node      *cmp;         /**< The Compare node that might be partial
	                                evaluated */
	ir_relation   relation;    /**< The Compare mode of the Compare node. */
Matthias Braun's avatar
Matthias Braun committed
202
203
204
205
206
207
	ir_node      *cnst;
	ir_tarval    *tv;
	ir_visited_t  visited_nr;
	ir_node      *cnst_pred;   /**< the block before the constant */
	int           cnst_pos;    /**< the pos to the constant block (needed to
	                                kill that edge later) */
208
} jumpthreading_env_t;
Christoph Mallon's avatar
Christoph Mallon committed
209

210
211
212
213
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
214
	/* we can evaluate Phis right now, all other nodes get copied */
Matthias Braun's avatar
Matthias Braun committed
215
	ir_node *copy;
Matthias Braun's avatar
Matthias Braun committed
216
217
	if (is_Phi(node)) {
		copy = get_Phi_pred(node, j);
218
		/* we might have to evaluate a Phi-cascade */
Matthias Braun's avatar
Matthias Braun committed
219
		if (get_irn_visited(copy) >= env->visited_nr)
220
			copy = (ir_node*)get_irn_link(copy);
Matthias Braun's avatar
Matthias Braun committed
221
222
223
224
225
	} else {
		copy = exact_copy(node);
		set_nodes_block(copy, copy_block);
		assert(get_irn_mode(copy) != mode_X);

226
		foreach_irn_in(copy, i, pred) {
227
			if (get_nodes_block(pred) != block)
Matthias Braun's avatar
Matthias Braun committed
228
229
				continue;

Matthias Braun's avatar
Matthias Braun committed
230
			ir_node *new_pred;
231
			if (get_irn_visited(pred) >= env->visited_nr) {
232
				new_pred = (ir_node*)get_irn_link(pred);
Matthias Braun's avatar
Matthias Braun committed
233
234
235
			} else {
				new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
			}
236
			DB((dbg, LEVEL_2, ">> Set Pred of %+F to %+F\n", copy, new_pred));
Matthias Braun's avatar
Matthias Braun committed
237
238
239
240
241
242
243
244
245
			set_irn_n(copy, i, new_pred);
		}
	}

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

246
247
248
static void copy_and_fix(const jumpthreading_env_t *env, ir_node *block,
                         ir_node *copy_block, int j)
{
Matthias Braun's avatar
Matthias Braun committed
249
	/* Look at all nodes in the cond_block and copy them into copy_block */
250
251
	foreach_out_edge(block, edge) {
		ir_node *node = get_edge_src_irn(edge);
Andreas Zwinkau's avatar
Andreas Zwinkau committed
252
		if (is_End(node)) {
253
			/* edge is a Keep edge. If the end block is unreachable via normal
Matthias Braun's avatar
Matthias Braun committed
254
			 * control flow, we must maintain end's reachability with Keeps. */
Andreas Zwinkau's avatar
Andreas Zwinkau committed
255
256
257
			keep_alive(copy_block);
			continue;
		}
258
		/* ignore control flow */
Matthias Braun's avatar
Matthias Braun committed
259
		ir_mode *mode = get_irn_mode(node);
Matthias Braun's avatar
Matthias Braun committed
260
		if (mode == mode_X || is_Cond(node) || is_Switch(node))
261
			continue;
262
#ifdef AVOID_PHIB
263
		/* we may not copy mode_b nodes, because this could produce Phi with
264
		 * mode_bs which can't be handled in all backends. Instead we duplicate
Christoph Mallon's avatar
Christoph Mallon committed
265
		 * the node and move it to its users */
266
		if (mode == mode_b) {
267
268
			ir_node *const pred = get_Proj_pred(node);
			long     const pn   = get_Proj_proj(node);
269

270
			foreach_out_edge_safe(node, edge) {
271
272
				ir_node *user       = get_edge_src_irn(edge);
				ir_node *user_block = get_nodes_block(user);
273
				if (user_block == block)
274
275
					continue;

Matthias Braun's avatar
Matthias Braun committed
276
277
				int      pos      = get_edge_src_pos(edge);
				ir_node *cmp_copy = exact_copy(pred);
278
				set_nodes_block(cmp_copy, user_block);
Matthias Braun's avatar
Matthias Braun committed
279
				ir_node *copy = new_r_Proj(cmp_copy, mode_b, pn);
280
281
282
283
				set_irn_n(user, pos, copy);
			}
			continue;
		}
284
#endif
Matthias Braun's avatar
Matthias Braun committed
285
		ir_node *copy = copy_and_fix_node(env, block, copy_block, j, node);
286
287

		/* we might hit values in blocks that have already been processed by a
288
		 * recursive find_phi_with_const() call */
289
		assert(get_irn_visited(copy) <= env->visited_nr);
290
		if (get_irn_visited(copy) >= env->visited_nr) {
291
			ir_node *prev_copy = (ir_node*)get_irn_link(copy);
292
			if (prev_copy != NULL)
293
294
295
				set_irn_link(node, prev_copy);
		}
	}
Christoph Mallon's avatar
Christoph Mallon committed
296

297
298
299
	/* fix data-flow (and reconstruct SSA if needed) */
	foreach_out_edge(block, edge) {
		ir_node *node = get_edge_src_irn(edge);
Matthias Braun's avatar
Matthias Braun committed
300
		ir_mode *mode = get_irn_mode(node);
Matthias Braun's avatar
Matthias Braun committed
301
		if (mode == mode_X || is_Cond(node) || is_Switch(node))
302
			continue;
303
#ifdef AVOID_PHIB
304
		if (mode == mode_b)
305
			continue;
306
#endif
307

308
		DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
Matthias Braun's avatar
Matthias Braun committed
309
		ir_node *copy_node = (ir_node*)get_irn_link(node);
310
		construct_ssa(block, node, copy_block, copy_node);
311
	}
312

313
	/* make sure copied PhiM nodes are kept alive if old nodes were */
314
315
316
317
318
319
320
	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);
321
322
323
324
		if (is_Phi(keep) && is_Phi(copy)) {
			assert(get_irn_mode(keep) == mode_M);
			add_End_keepalive(end, copy);
		}
325
	}
326
327
}

328
/**
Matthias Braun's avatar
Matthias Braun committed
329
 * Returns whether the cmp evaluates to true or false, or can't be evaluated!
330
 *
331
 * @param relation  the compare mode of the Compare
332
333
 * @param tv_left   the left tarval
 * @param tv_right  the right tarval
Matthias Braun's avatar
Matthias Braun committed
334
 * @returns 1: true, 0: false, -1: can't evaluate
335
 */
336
337
static int eval_cmp_tv(ir_relation relation, ir_tarval *tv_left,
                       ir_tarval *tv_right)
338
{
339
	/* does the compare evaluate to true? */
Matthias Braun's avatar
Matthias Braun committed
340
	ir_relation cmp_result = tarval_cmp(tv_left, tv_right);
341
	if (cmp_result == ir_relation_false)
342
		return -1;
343
344
	if ((cmp_result & relation) != 0)
		return 1;
345

346
	return 0;
347
348
}

349
/**
Matthias Braun's avatar
Matthias Braun committed
350
 * Returns whether the cmp evaluates to true or false, or can't be evaluated!
351
352
353
 *
 * @param env      the environment
 * @param cand     the candidate node, either a Const or a Confirm
Matthias Braun's avatar
Matthias Braun committed
354
 * @returns 1: true, 0: false, -1: can't evaluate
355
 */
356
357
static int eval_cmp(jumpthreading_env_t *env, ir_node *cand)
{
358
	if (is_Const(cand)) {
359
360
361
		ir_tarval *tv_cand = get_Const_tarval(cand);
		ir_tarval *tv_cmp  = get_Const_tarval(env->cnst);
		return eval_cmp_tv(env->relation, tv_cand, tv_cmp);
Matthias Braun's avatar
Matthias Braun committed
362
363
364
365
	} else {
		assert(is_Confirm(cand));
		ir_tarval *res = computed_value_Cmp_Confirm(env->cmp, cand, env->cnst,
		                                            env->relation);
366
		if (!tarval_is_constant(res))
367
368
			return -1;
		return res == tarval_b_true;
369
	}
370
371
372
373
374
}

/**
 * Check for Const or Confirm with Const.
 */
Matthias Braun's avatar
Matthias Braun committed
375
static bool is_Const_or_Confirm(const ir_node *node)
376
{
377
378
	if (is_Confirm(node))
		node = get_Confirm_bound(node);
379
380
381
382
	return is_Const(node);
}

/**
383
 * get the tarval of a Const or Confirm with
384
 */
Matthias Braun's avatar
Matthias Braun committed
385
static ir_tarval *get_Const_or_Confirm_tarval(const ir_node *node)
386
{
Matthias Braun's avatar
Matthias Braun committed
387
388
	if (is_Confirm(node))
		node = get_Confirm_bound(node);
389
390
391
	return get_Const_tarval(node);
}

392
393
static ir_node *find_const_or_confirm(jumpthreading_env_t *env, ir_node *jump,
                                      ir_node *value)
394
{
395
	if (irn_visited_else_mark(value))
396
397
		return NULL;

Matthias Braun's avatar
Matthias Braun committed
398
	ir_node *block = get_nodes_block(jump);
399
	if (is_Const_or_Confirm(value)) {
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
		int evaluated = eval_cmp(env, value);
		if (evaluated < 0)
			return NULL;
		/* maybe we could evaluate the condition completely without any
		 * partial tracking along paths. */
		if (block == get_nodes_block(env->cmp)) {
			if (evaluated == 0) {
				ir_graph *irg = get_irn_irg(block);
				ir_node  *bad = new_r_Bad(irg, mode_X);
				exchange(jump, bad);
			} else if (evaluated == 1) {
				dbg_info *dbgi = get_irn_dbg_info(skip_Proj(jump));
				ir_node  *jmp  = new_rd_Jmp(dbgi, get_nodes_block(jump));
				exchange(jump, jmp);
			}
Matthias Braun's avatar
Matthias Braun committed
415
416
			/* we need a bigger visited nr when going back */
			env->visited_nr++;
417
418
419
			return block;
		}
		if (evaluated <= 0)
420
			return NULL;
Christoph Mallon's avatar
Christoph Mallon committed
421

Matthias Braun's avatar
Matthias Braun committed
422
423
		DB((dbg, LEVEL_1, "> Found jump threading candidate %+F->%+F\n",
			block, env->true_block));
Christoph Mallon's avatar
Christoph Mallon committed
424

425
		/* adjust true_block to point directly towards our jump */
426
		add_pred(env->true_block, jump);
427

428
429
		split_critical_edge(env->true_block, 0);

430
		/* we need a bigger visited nr when going back */
431
432
433
		env->visited_nr++;
		return block;
	}
434

435
	if (is_Phi(value)) {
436
		/* the Phi has to be in the same Block as the Jmp */
437
		if (get_nodes_block(value) != block)
438
			return NULL;
439

Matthias Braun's avatar
Matthias Braun committed
440
441
442
443
		for (int i = 0, arity = get_irn_arity(value); i < arity; ++i) {
			ir_node *phi_pred   = get_Phi_pred(value, i);
			ir_node *cfgpred    = get_Block_cfgpred(block, i);
			ir_node *copy_block = find_const_or_confirm(env, cfgpred, phi_pred);
444
			if (copy_block == NULL)
445
446
				continue;

447
			/* copy duplicated nodes in copy_block and fix SSA */
448
			copy_and_fix(env, block, copy_block, i);
449
			if (copy_block == get_nodes_block(cfgpred)) {
450
				env->cnst_pred = block;
451
				env->cnst_pos  = i;
452
			}
453

454
			/* return now as we can't process more possibilities in 1 run */
455
			return copy_block;
456
		}
Christoph Mallon's avatar
Christoph Mallon committed
457
	}
458

459
	return NULL;
Christoph Mallon's avatar
Christoph Mallon committed
460
461
}

462
static ir_node *find_candidate(jumpthreading_env_t *env, ir_node *jump,
463
                               ir_node *value)
464
{
Matthias Braun's avatar
Matthias Braun committed
465
	if (irn_visited_else_mark(value))
466
467
		return NULL;

Matthias Braun's avatar
Matthias Braun committed
468
	ir_node *block = get_nodes_block(jump);
469
	if (is_Const_or_Confirm(value)) {
Matthias Braun's avatar
Matthias Braun committed
470
		ir_tarval *tv = get_Const_or_Confirm_tarval(value);
471
		if (tv != env->tv)
472
473
			return NULL;

Matthias Braun's avatar
Matthias Braun committed
474
475
		DB((dbg, LEVEL_1, "> Found jump threading candidate %+F->%+F\n",
			block, env->true_block));
476

477
		/* adjust true_block to point directly towards our jump */
478
479
		add_pred(env->true_block, jump);

480
481
		split_critical_edge(env->true_block, 0);

482
		/* we need a bigger visited nr when going back */
483
484
		env->visited_nr++;
		return block;
485
	}
486
	if (is_Phi(value)) {
487
		/* the Phi has to be in the same Block as the Jmp */
488
		if (get_nodes_block(value) != block)
489
			return NULL;
490

Matthias Braun's avatar
Matthias Braun committed
491
492
493
494
		for (int i = 0, arity = get_irn_arity(value); i < arity; ++i) {
			ir_node *phi_pred   = get_Phi_pred(value, i);
			ir_node *cfgpred    = get_Block_cfgpred(block, i);
			ir_node *copy_block = find_candidate(env, cfgpred, phi_pred);
495
			if (copy_block == NULL)
496
497
498
499
				continue;

			/* copy duplicated nodes in copy_block and fix SSA */
			copy_and_fix(env, block, copy_block, i);
500
			if (copy_block == get_nodes_block(cfgpred)) {
501
502
503
504
				env->cnst_pred = block;
				env->cnst_pos  = i;
			}

505
			/* return now as we can't process more possibilities in 1 run */
506
			return copy_block;
Christoph Mallon's avatar
Christoph Mallon committed
507
		}
508
	}
509
510
511
512
513
	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);
514

515
516
		/* we assume that the constant is on the right side, swap left/right
		 * if needed */
517
		if (is_Const(left)) {
518
519
520
			ir_node *t = left;
			left       = right;
			right      = t;
521

522
			relation   = get_inversed_relation(relation);
523
		}
524

525
		if (!is_Const(right))
526
527
528
			return NULL;
		if (get_nodes_block(left) != block)
			return NULL;
529
		/* negate condition when we're looking for the false block */
Matthias Braun's avatar
Matthias Braun committed
530
		if (env->tv == tarval_b_false)
531
			relation = get_negated_relation(relation);
532

533
		/* (recursively) look if a pred of a Phi is a constant or a Confirm */
534
535
536
		env->cmp      = cmp;
		env->relation = relation;
		env->cnst     = right;
537
		return find_const_or_confirm(env, jump, left);
538
	}
539

540
541
	return NULL;
}
542
543
544
545
546
547
548
549
550
551
552
553
554
555

/**
 * Block-walker: searches for the following construct
 *
 *  Const or Phi with constants
 *           |
 *          Cmp
 *           |
 *         Cond
 *          /
 *       ProjX
 *        /
 *     Block
 */
556
static void thread_jumps(ir_node* block, void* data)
557
{
558
	bool *changed = (bool*)data;
559

560
	/* we do not deal with Phis, so restrict this to exactly one cfgpred */
561
	if (get_Block_n_cfgpreds(block) != 1)
562
563
		return;

Matthias Braun's avatar
Matthias Braun committed
564
	ir_node *projx = get_Block_cfgpred(block, 0);
565
566
567
	if (!is_Proj(projx))
		return;

Matthias Braun's avatar
Matthias Braun committed
568
	ir_node *cond = get_Proj_pred(projx);
569
	/* TODO handle switch Conds */
Matthias Braun's avatar
Matthias Braun committed
570
	if (!is_Cond(cond))
571
		return;
572

573
	/* (recursively) look if a pred of a Phi is a constant or a Confirm */
574
575
	ir_node  *selector = get_Cond_selector(cond);
	ir_graph *irg      = get_irn_irg(block);
576
577
578
579
580
581
582
583
584
585
586
587
	if (is_Const(selector)) {
		const ir_tarval *tv = get_Const_tarval(selector);
		assert(tv == tarval_b_false || tv == tarval_b_true);
		ir_node    *const cond_block = get_nodes_block(cond);
		ir_node    *const jmp        = new_r_Jmp(cond_block);
		ir_node    *const bad        = new_r_Bad(irg, mode_X);
		const bool        is_true    = tv == tarval_b_true;
		ir_node *const in[] = {
			[pn_Cond_false] = is_true ? bad : jmp,
			[pn_Cond_true]  = is_true ? jmp : bad,
		};
		turn_into_tuple(cond, ARRAY_SIZE(in), in);
588
		*changed = true;
589
590
		return;
	}
591
	inc_irg_visited(irg);
592
593
594
595
596
	jumpthreading_env_t env;
	env.cnst_pred  = NULL;
	env.tv         = get_Proj_proj(projx) == pn_Cond_false
	                 ? tarval_b_false : tarval_b_true;
	env.true_block = block;
597
	env.visited_nr = get_irg_visited(irg);
598

Matthias Braun's avatar
Matthias Braun committed
599
	ir_node *copy_block = find_candidate(&env, projx, selector);
600
	if (copy_block == NULL)
601
602
		return;

603
604
605
606
	if (copy_block != get_nodes_block(cond)) {
		/* We might thread the condition block of an infinite loop,
		 * such that there is no path to End anymore. */
		keep_alive(block);
Andreas Zwinkau's avatar
Andreas Zwinkau committed
607

608
609
610
611
612
		/* we have to remove the edge towards the pred as the pred now
		 * jumps into the true_block. We also have to shorten Phis
		 * in our block because of this */
		ir_node *badX     = new_r_Bad(irg, mode_X);
		int      cnst_pos = env.cnst_pos;
613

614
615
616
		/* shorten Phis */
		foreach_out_edge_safe(env.cnst_pred, edge) {
			ir_node *node = get_edge_src_irn(edge);
617

618
619
620
621
			if (is_Phi(node)) {
				ir_node *bad = new_r_Bad(irg, get_irn_mode(node));
				set_Phi_pred(node, cnst_pos, bad);
			}
Matthias Braun's avatar
Matthias Braun committed
622
		}
623

624
625
		set_Block_cfgpred(env.cnst_pred, cnst_pos, badX);
	}
626
627

	/* the graph is changed now */
628
	*changed = true;
629
630
}

631
void opt_jumpthreading(ir_graph* irg)
632
{
633
634
635
636
	assure_irg_properties(irg,
		IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE
		| IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
		| IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
637

638
	FIRM_DBG_REGISTER(dbg, "firm.opt.jumpthreading");
639

640
	DB((dbg, LEVEL_1, "===> Performing jumpthreading on %+F\n", irg));
641

642
	ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
643

Matthias Braun's avatar
Matthias Braun committed
644
645
	bool changed = false;
	bool rerun;
646
	do {
647
		rerun = false;
648
		irg_block_walk_graph(irg, thread_jumps, NULL, &rerun);
Michael Beck's avatar
Michael Beck committed
649
650
651
		changed |= rerun;
	} while (rerun);

652
	ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
653

654
655
	confirm_irg_properties(irg,
		changed ? IR_GRAPH_PROPERTIES_NONE : IR_GRAPH_PROPERTIES_ALL);
656
}