lower_switch.c 15.6 KB
Newer Older
1
/*
2
 * Copyright (C) 1995-2011 University of Karlsruhe.  All right reserved.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
 *
 * 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.
 */

/**
 * @file
 * @brief   Lowering of Switches if necessary or advantageous.
 * @author  Moritz Kroll
 */
#include "config.h"

27
#include <limits.h>
28
#include <stdbool.h>
29

30
#include "array_t.h"
31
#include "ircons.h"
Moritz Kroll's avatar
Moritz Kroll committed
32
#include "irgopt.h"
33
34
35
#include "irgwalk.h"
#include "irnode_t.h"
#include "irouts.h"
Michael Beck's avatar
Michael Beck committed
36
#include "irpass_t.h"
37
#include "lowering.h"
38
#include "error.h"
39
#include "irnodeset.h"
40

41
#define foreach_out_irn(irn, i, outirn) for (i = get_irn_n_outs(irn) - 1;\
42
43
	i >= 0 && (outirn = get_irn_out(irn, i)); --i)

44
typedef struct walk_env_t {
45
46
	ir_nodeset_t  processed;
	ir_mode      *selector_mode;
47
	unsigned      spare_size; /**< the allowed spare size for table switches */
Matthias Braun's avatar
Matthias Braun committed
48
	unsigned      small_switch;
49
	bool          changed;    /**< indicates whether a change was performed */
50
51
} walk_env_t;

52
typedef struct case_data_t {
Matthias Braun's avatar
Matthias Braun committed
53
54
	const ir_switch_table_entry *entry;
	ir_node                     *target;
55
56
} case_data_t;

Matthias Braun's avatar
Matthias Braun committed
57
58
typedef struct switch_info_t {
	ir_node     *switchn;
59
60
	ir_tarval   *switch_min;
	ir_tarval   *switch_max;
Matthias Braun's avatar
Matthias Braun committed
61
62
63
64
65
	ir_node     *default_block;
	unsigned     num_cases;
	case_data_t *cases;
	ir_node    **defusers;    /**< the Projs pointing to the default case */
} switch_info_t;
66

Matthias Braun's avatar
Matthias Braun committed
67
68
69
/**
 * analyze enough to decide if we should lower the switch
 */
70
static void analyse_switch0(switch_info_t *info, ir_node *switchn)
71
{
72
73
74
75
76
77
78
79
	const ir_switch_table *table      = get_Switch_table(switchn);
	size_t                 n_entries  = ir_switch_table_get_n_entries(table);
	ir_mode               *mode       = get_irn_mode(get_Switch_selector(switchn));
	ir_tarval             *switch_min = get_mode_max(mode);
	ir_tarval             *switch_max = get_mode_min(mode);
	unsigned               num_cases  = 0;

	for (size_t e = 0; e < n_entries; ++e) {
Matthias Braun's avatar
Matthias Braun committed
80
81
82
		const ir_switch_table_entry *entry
			= ir_switch_table_get_entry_const(table, e);
		if (entry->pn == 0)
83
84
			continue;

85
86
87
88
89
		if (tarval_cmp(entry->min, switch_min) == ir_relation_less)
			switch_min = entry->min;
		if (tarval_cmp(entry->max, switch_max) == ir_relation_greater)
			switch_max = entry->max;

90
		++num_cases;
91
92
	}

Matthias Braun's avatar
Matthias Braun committed
93
94
95
96
	info->switchn    = switchn;
	info->switch_min = switch_min;
	info->switch_max = switch_max;
	info->num_cases  = num_cases;
97
98
99
100
}

static int casecmp(const void *a, const void *b)
{
Matthias Braun's avatar
Matthias Braun committed
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
	const case_data_t           *cda = (const case_data_t*)a;
	const case_data_t           *cdb = (const case_data_t*)b;
	const ir_switch_table_entry *ea  = cda->entry;
	const ir_switch_table_entry *eb  = cdb->entry;

	if (ea == eb)
		return 0;

	if (tarval_cmp(ea->max, eb->min) == ir_relation_less)
		return -1;
	/* cases must be non overlapping, so the only remaining case is greater */
	assert(tarval_cmp(ea->min, eb->max) == ir_relation_greater);
	return 1;
}

/**
 * Analyse the stuff that anayse_switch0() left out
 */
static void analyse_switch1(switch_info_t *info)
{
	const ir_node         *switchn   = info->switchn;
	const ir_switch_table *table     = get_Switch_table(switchn);
	size_t                 n_entries = ir_switch_table_get_n_entries(table);
	unsigned               n_outs    = get_Switch_n_outs(switchn);
	ir_node              **targets   = XMALLOCNZ(ir_node*, n_outs);
	unsigned               num_cases = info->num_cases;
	case_data_t           *cases     = XMALLOCN(case_data_t, num_cases);
	unsigned               c         = 0;
	size_t                 e;
	int                    i;
	ir_node               *proj;

	foreach_out_irn(switchn, i, proj) {
		long     pn     = get_Proj_proj(proj);
		ir_node *target = get_irn_out(proj, 0);

		assert((unsigned)pn < n_outs);
		assert(targets[(unsigned)pn] == NULL);
		targets[(unsigned)pn] = target;
	}

	for (e = 0; e < n_entries; ++e) {
		const ir_switch_table_entry *entry
			= ir_switch_table_get_entry_const(table, e);
		if (entry->pn == 0)
			continue;

		cases[c].entry  = entry;
		cases[c].target = targets[entry->pn];
		++c;
	}
	assert(c == num_cases);
153
154

	/*
Matthias Braun's avatar
Matthias Braun committed
155
156
	 * Switch should be transformed into an if cascade.
	 * So first order the cases, so we can do a binary search on them.
157
	 */
Matthias Braun's avatar
Matthias Braun committed
158
159
160
161
	qsort(cases, num_cases, sizeof(cases[0]), casecmp);

	info->default_block = targets[pn_Switch_default];
	info->cases         = cases;
Matthias Braun's avatar
Matthias Braun committed
162
	free(targets);
Matthias Braun's avatar
Matthias Braun committed
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
}

static void normalize_table(ir_node *switchn, ir_mode *new_mode,
                            ir_tarval *delta)
{
	ir_switch_table *table     = get_Switch_table(switchn);
	size_t           n_entries = ir_switch_table_get_n_entries(table);
	size_t           e;
	/* adapt switch_table */
	for (e = 0; e < n_entries; ++e) {
		ir_switch_table_entry *entry = ir_switch_table_get_entry(table, e);
		ir_tarval *min = entry->min;

		if (entry->pn == 0)
			continue;

		min = tarval_convert_to(min, new_mode);
		if (delta != NULL)
			min = tarval_sub(min, delta, NULL);

		if (entry->min == entry->max) {
			entry->min = min;
			entry->max = min;
		} else {
			ir_tarval *max = entry->max;
			max = tarval_convert_to(max, new_mode);
			if (delta != NULL)
				max = tarval_sub(max, delta, NULL);
			entry->min = min;
			entry->max = max;
		}
	}
}

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
static void create_out_of_bounds_check(switch_info_t *info)
{
	ir_node    *switchn       = info->switchn;
	ir_graph   *irg           = get_irn_irg(switchn);
	dbg_info   *dbgi          = get_irn_dbg_info(switchn);
	ir_node    *selector      = get_Switch_selector(switchn);
	ir_node    *block         = get_nodes_block(switchn);
	ir_node   **default_preds = NEW_ARR_F(ir_node*, 0);
	ir_node    *default_block = NULL;
	ir_node    *max_const;
	ir_node    *proj_true;
	ir_node    *proj_false;
	ir_node    *cmp;
	ir_node    *oob_cond;
	ir_node    *in[1];
	ir_node    *new_block;
	int         i;
	ir_node    *proj;
	size_t      n_default_preds;

	assert(tarval_is_null(info->switch_min));

	/* check for out-of-bounds */
	max_const  = new_r_Const(irg, info->switch_max);
	cmp        = new_rd_Cmp(dbgi, block, selector, max_const, ir_relation_less_equal);
	oob_cond   = new_rd_Cond(dbgi, block, cmp);
	proj_true  = new_r_Proj(oob_cond, mode_X, pn_Cond_true);
	proj_false = new_r_Proj(oob_cond, mode_X, pn_Cond_false);

	ARR_APP1(ir_node*, default_preds, proj_false);

	/* create new block containing the switch */
	in[0] = proj_true;
	new_block = new_r_Block(irg, 1, in);
	set_nodes_block(switchn, new_block);

	/* adjust projs */
	foreach_out_irn(switchn, i, proj) {
		long pn = get_Proj_proj(proj);
		if (pn == pn_Switch_default) {
			assert(default_block == NULL);
			default_block = get_irn_out(proj, 0);
			ARR_APP1(ir_node*, default_preds, proj);
		}
		set_nodes_block(proj, new_block);
	}

	/* adapt default block */
	n_default_preds = ARR_LEN(default_preds);
	if (n_default_preds > 1) {
		/* create new intermediate blocks so we don't have critical edges */
		size_t p;
		for (p = 0; p < n_default_preds; ++p) {
			ir_node *pred = default_preds[p];
			ir_node *split_block;
			ir_node *block_in[1];

			block_in[0] = pred;
			split_block = new_r_Block(irg, 1, block_in);

			default_preds[p] = new_r_Jmp(split_block);
		}
	}
	set_irn_in(default_block, n_default_preds, default_preds);

	DEL_ARR_F(default_preds);

	clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
}

Matthias Braun's avatar
Matthias Braun committed
267
268
269
/**
 * normalize switch to work on an unsigned input with the first case at 0
 */
270
static void normalize_switch(switch_info_t *info, ir_mode *selector_mode)
Matthias Braun's avatar
Matthias Braun committed
271
{
272
273
274
275
	ir_node   *switchn         = info->switchn;
	ir_graph  *irg             = get_irn_irg(switchn);
	ir_node   *block           = get_nodes_block(switchn);
	ir_node   *selector        = get_Switch_selector(switchn);
276
	ir_mode   *mode            = get_irn_mode(selector);
277
278
279
280
	ir_tarval *delta           = NULL;
	bool       needs_normalize = false;

	ir_tarval *min = info->switch_min;
Matthias Braun's avatar
Matthias Braun committed
281
	if (mode_is_signed(mode)) {
282
283
284
		mode             = find_unsigned_mode(mode);
		selector         = new_r_Conv(block, selector, mode);
		min              = tarval_convert_to(min, mode);
285
		info->switch_min = min;
286
		info->switch_max = tarval_convert_to(info->switch_max, mode);
287
		needs_normalize  = true;
Matthias Braun's avatar
Matthias Braun committed
288
289
290
	}

	/* normalize so switch_min is at 0 */
291
292
293
294
	if (min != get_mode_null(mode)) {
		ir_node  *min_const = new_r_Const(irg, min);
		dbg_info *dbgi      = get_irn_dbg_info(switchn);
		selector = new_rd_Sub(dbgi, block, selector, min_const, mode);
Matthias Braun's avatar
Matthias Braun committed
295

296
297
298
		info->switch_max = tarval_sub(info->switch_max, min, mode);
		info->switch_min = get_mode_null(mode);
		delta            = min;
Matthias Braun's avatar
Matthias Braun committed
299

300
		needs_normalize = true;
Matthias Braun's avatar
Matthias Braun committed
301
302
	}

303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
	/* if we have a selector_mode set, then the we will have a switch node,
	 * we have to construct an out-of-bounds check then and after that convert
	 * the switch/selector to the backends desired switch mode */
	if (selector_mode != NULL) {
		set_Switch_selector(switchn, selector);
		create_out_of_bounds_check(info);

		selector = new_r_Conv(block, selector, selector_mode);
		mode     = selector_mode;
		info->switch_min = tarval_convert_to(info->switch_min, mode);
		info->switch_max = tarval_convert_to(info->switch_max, mode);
		if (delta != NULL)
			delta = tarval_convert_to(delta, mode);
		needs_normalize = true;
	}

319
	if (needs_normalize) {
Matthias Braun's avatar
Matthias Braun committed
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
		set_Switch_selector(switchn, selector);
		normalize_table(switchn, mode, delta);
	}
}

/**
 * Create an if (selector == caseval) Cond node (and handle the special case
 * of ranged cases)
 */
static ir_node *create_case_cond(const ir_switch_table_entry *entry,
                                 dbg_info *dbgi, ir_node *block,
                                 ir_node *selector)
{
	ir_graph *irg      = get_irn_irg(block);
	ir_node  *minconst = new_r_Const(irg, entry->min);
	ir_node  *cmp;

	if (entry->min == entry->max) {
		cmp = new_rd_Cmp(dbgi, block, selector, minconst, ir_relation_equal);
	} else {
		ir_tarval *adjusted_max = tarval_sub(entry->max, entry->min, NULL);
		ir_node   *sub          = new_rd_Sub(dbgi, block, selector, minconst,
		                                     get_tarval_mode(adjusted_max));
		ir_node   *maxconst     = new_r_Const(irg, adjusted_max);
		cmp = new_rd_Cmp(dbgi, block, sub, maxconst, ir_relation_less_equal);
	}

	return new_rd_Cond(dbgi, block, cmp);
348
349
350
351
352
}

/**
 * Creates an if cascade realizing binary search.
 */
Matthias Braun's avatar
Matthias Braun committed
353
static void create_if_cascade(switch_info_t *info, ir_node *block,
354
                              case_data_t *curcases, unsigned numcases)
355
{
Matthias Braun's avatar
Matthias Braun committed
356
357
358
359
	ir_graph      *irg      = get_irn_irg(block);
	const ir_node *switchn  = info->switchn;
	dbg_info      *dbgi     = get_irn_dbg_info(switchn);
	ir_node       *selector = get_Switch_selector(switchn);
360

361
362
	if (numcases == 0) {
		/* zero cases: "goto default;" */
Matthias Braun's avatar
Matthias Braun committed
363
		ARR_APP1(ir_node*, info->defusers, new_r_Jmp(block));
364
	} else if (numcases == 1) {
Matthias Braun's avatar
Matthias Braun committed
365
366
367
		/*only one case: "if (sel == val) goto target else goto default;"*/
		const ir_switch_table_entry *entry = curcases[0].entry;
		ir_node *cond      = create_case_cond(entry, dbgi, block, selector);
368
369
370
371
		ir_node *trueproj  = new_r_Proj(cond, mode_X, pn_Cond_true);
		ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);

		set_Block_cfgpred(curcases[0].target, 0, trueproj);
Matthias Braun's avatar
Matthias Braun committed
372
		ARR_APP1(ir_node*, info->defusers, falseproj);
373
	} else if (numcases == 2) {
374
		/* only two cases: "if (sel == val[0]) goto target[0];" */
Matthias Braun's avatar
Matthias Braun committed
375
376
377
		const ir_switch_table_entry *entry0 = curcases[0].entry;
		const ir_switch_table_entry *entry1 = curcases[1].entry;
		ir_node *cond      = create_case_cond(entry0, dbgi, block, selector);
378
379
		ir_node *trueproj  = new_r_Proj(cond, mode_X, pn_Cond_true);
		ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
380
381
382
		ir_node *in[1];
		ir_node *neblock;

383
384
385
386
		set_Block_cfgpred(curcases[0].target, 0, trueproj);

		in[0] = falseproj;
		neblock = new_r_Block(irg, 1, in);
387

388
		/* second part: "else if (sel == val[1]) goto target[1] else goto default;" */
Matthias Braun's avatar
Matthias Braun committed
389
		cond      = create_case_cond(entry1, dbgi, neblock, selector);
390
391
392
		trueproj  = new_r_Proj(cond, mode_X, pn_Cond_true);
		falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
		set_Block_cfgpred(curcases[1].target, 0, trueproj);
Matthias Braun's avatar
Matthias Braun committed
393
		ARR_APP1(ir_node*, info->defusers, falseproj);
394
395
	} else {
		/* recursive case: split cases in the middle */
Matthias Braun's avatar
Matthias Braun committed
396
397
398
399
		unsigned midcase = numcases / 2;
		const ir_switch_table_entry *entry = curcases[midcase].entry;
		ir_node *val = new_r_Const(irg, entry->min);
		ir_node *cmp = new_rd_Cmp(dbgi, block, selector, val, ir_relation_less);
400
		ir_node *cond = new_rd_Cond(dbgi, block, cmp);
401
402
403
404
		ir_node *in[1];
		ir_node *ltblock;
		ir_node *geblock;

405
406
		in[0]   = new_r_Proj(cond, mode_X, pn_Cond_true);
		ltblock = new_r_Block(irg, 1, in);
407

408
409
		in[0]   = new_r_Proj(cond, mode_X, pn_Cond_false);
		geblock = new_r_Block(irg, 1, in);
410

Matthias Braun's avatar
Matthias Braun committed
411
412
		create_if_cascade(info, ltblock, curcases, midcase);
		create_if_cascade(info, geblock, curcases + midcase, numcases - midcase);
413
414
415
416
	}
}

/**
Matthias Braun's avatar
Matthias Braun committed
417
 * Block-Walker: searches for Switch nodes
418
 */
Matthias Braun's avatar
Matthias Braun committed
419
static void find_switch_nodes(ir_node *block, void *ctx)
420
{
Matthias Braun's avatar
Matthias Braun committed
421
422
423
424
	walk_env_t   *env = (walk_env_t *)ctx;
	ir_node      *projx;
	ir_node      *switchn;
	switch_info_t info;
425

426
427
	/* because we split critical blocks only blocks with 1 predecessors may
	 * contain Proj->Cond nodes */
428
	if (get_Block_n_cfgpreds(block) != 1)
429
430
431
		return;

	projx = get_Block_cfgpred(block, 0);
432
	if (!is_Proj(projx))
433
434
435
		return;
	assert(get_irn_mode(projx) == mode_X);

Matthias Braun's avatar
Matthias Braun committed
436
437
	switchn = get_Proj_pred(projx);
	if (!is_Switch(switchn))
438
439
		return;

Matthias Braun's avatar
Matthias Braun committed
440
	if (ir_nodeset_contains(&env->processed, switchn))
441
		return;
Matthias Braun's avatar
Matthias Braun committed
442
	ir_nodeset_insert(&env->processed, switchn);
443

444
	analyse_switch0(&info, switchn);
445

446
447
448
449
	/*
	 * Here we have: num_cases and [switch_min, switch_max] interval.
	 * We do an if-cascade if there are too many spare numbers.
	 */
450
451
452
453
454
455
456
457
458
459
	ir_mode   *mode  = get_irn_mode(get_Switch_selector(switchn));
	ir_tarval *spare = tarval_sub(info.switch_max, info.switch_min, mode);
	mode  = find_unsigned_mode(mode);
	spare = tarval_convert_to(spare, mode);
	ir_tarval *num_cases_minus_one
		= new_tarval_from_long(info.num_cases-1, mode);
	spare = tarval_sub(spare, num_cases_minus_one, mode);
	ir_tarval *spare_size = new_tarval_from_long(env->spare_size, mode);
	bool lower_switch = (info.num_cases <= env->small_switch
	 || (tarval_cmp(spare, spare_size) & ir_relation_greater_equal));
Matthias Braun's avatar
Matthias Braun committed
460
461

	if (!lower_switch) {
462
463
		/* we won't decompose the switch. But we must add an out-of-bounds
		 * check */
464
		normalize_switch(&info, env->selector_mode);
465
		return;
466
	}
467

468
	normalize_switch(&info, NULL);
Matthias Braun's avatar
Matthias Braun committed
469
	analyse_switch1(&info);
470
471

	/* Now create the if cascade */
472
	env->changed  = true;
Matthias Braun's avatar
Matthias Braun committed
473
	info.defusers = NEW_ARR_F(ir_node*, 0);
474
	block         = get_nodes_block(switchn);
Matthias Braun's avatar
Matthias Braun committed
475
	create_if_cascade(&info, block, info.cases, info.num_cases);
Moritz Kroll's avatar
Moritz Kroll committed
476
477

	/* Connect new default case users */
Matthias Braun's avatar
Matthias Braun committed
478
	set_irn_in(info.default_block, ARR_LEN(info.defusers), info.defusers);
479

Matthias Braun's avatar
Matthias Braun committed
480
481
	DEL_ARR_F(info.defusers);
	xfree(info.cases);
482
483
	clear_irg_properties(get_irn_irg(block), IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES
	                                  | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
484
485
}

486
487
void lower_switch(ir_graph *irg, unsigned small_switch, unsigned spare_size,
                  ir_mode *selector_mode)
488
{
489
490
491
	if (mode_is_signed(selector_mode))
		panic("expected unsigned mode for switch selector");

492
	walk_env_t env;
493
	env.selector_mode       = selector_mode;
494
	env.spare_size          = spare_size;
Matthias Braun's avatar
Matthias Braun committed
495
	env.small_switch        = small_switch;
496
	env.changed             = false;
497
	ir_nodeset_init(&env.processed);
498

Moritz Kroll's avatar
Moritz Kroll committed
499
	remove_critical_cf_edges(irg);
500
501
	assure_irg_outs(irg);

Matthias Braun's avatar
Matthias Braun committed
502
	irg_block_walk_graph(irg, find_switch_nodes, NULL, &env);
503
	ir_nodeset_destroy(&env.processed);
504
}