ldstopt.c 25.4 KB
Newer Older
Michael Beck's avatar
Michael Beck committed
1
2
3
4
5
6
7
/*
 * Project:     libFIRM
 * File name:   ir/opt/ldstopt.c
 * Purpose:     load store optimizations
 * Author:
 * Created:
 * CVS-ID:      $Id$
Götz Lindenmaier's avatar
Götz Lindenmaier committed
8
 * Copyright:   (c) 1998-2004 Universitt Karlsruhe
Michael Beck's avatar
Michael Beck committed
9
10
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */
Michael Beck's avatar
Michael Beck committed
11
12
13
14
15
16
17
18
19
20
21
22
23
24
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#endif
#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif
#ifdef HAVE_STRING_H
# include <string.h>
#endif

Michael Beck's avatar
Michael Beck committed
25
26
27
28
29
30
31
32
33
34
35
36
# include "irnode_t.h"
# include "irgraph_t.h"
# include "irmode_t.h"
# include "iropt_t.h"
# include "ircons_t.h"
# include "irgmod.h"
# include "irgwalk.h"
# include "irvrfy.h"
# include "tv_t.h"
# include "dbginfo_t.h"
# include "iropt_dbg.h"
# include "irflag_t.h"
Michael Beck's avatar
Michael Beck committed
37
# include "array.h"
38
# include "irhooks.h"
39
40
41
42
43
# include "opt_polymorphy.h"

#ifdef DO_CACHEOPT
#include "cacheopt/cachesim.h"
#endif
Michael Beck's avatar
Michael Beck committed
44
45
46
47
48
49
50
51
52
53
54
55
56
57

#undef IMAX
#define IMAX(a,b)	((a) > (b) ? (a) : (b))

#define MAX_PROJ	IMAX(pn_Load_max, pn_Store_max)

/**
 * walker environment
 */
typedef struct _walk_env_t {
  struct obstack obst;		/**< list of all stores */
  int changes;
} walk_env_t;

58
59
60
61
62
63
64
/**
 * flags for Load/Store
 */
enum ldst_flags_t {
  LDST_VISITED = 1              /**< if set, this Load/Store is already visited */
};

Michael Beck's avatar
Michael Beck committed
65
66
67
68
/**
 * a Load/Store info
 */
typedef struct _ldst_info_t {
69
70
71
72
  ir_node  *projs[MAX_PROJ];    /**< list of Proj's of this node */
  ir_node  *exc_block;          /**< the exception block if available */
  int      exc_idx;             /**< predecessor index in the exception block */
  unsigned flags;               /**< flags */
Michael Beck's avatar
Michael Beck committed
73
74
} ldst_info_t;

75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
/**
 * flags for control flow
 */
enum block_flags_t {
  BLOCK_HAS_COND = 1,      /**< Block has conditional control flow */
  BLOCK_HAS_EXC  = 2       /**< Block has exceptionl control flow */
};

/**
 * a Block info
 */
typedef struct _block_info_t {
  unsigned flags;               /**< flags for the block */
} block_info_t;

Michael Beck's avatar
Michael Beck committed
90
91
92
93
94
95
96
97
98
99
100
/**
 * walker, clears all links first
 */
static void init_links(ir_node *n, void *env)
{
  set_irn_link(n, NULL);
}

/**
 * get the Load/Store info of a node
 */
101
static ldst_info_t *get_ldst_info(ir_node *node, walk_env_t *env)
Michael Beck's avatar
Michael Beck committed
102
103
104
105
106
107
108
109
110
111
112
113
114
{
  ldst_info_t *info = get_irn_link(node);

  if (! info) {
    info = obstack_alloc(&env->obst, sizeof(*info));

    memset(info, 0, sizeof(*info));

    set_irn_link(node, info);
  }
  return info;
}

115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/**
 * get the Block info of a node
 */
static block_info_t *get_block_info(ir_node *node, walk_env_t *env)
{
  block_info_t *info = get_irn_link(node);

  if (! info) {
    info = obstack_alloc(&env->obst, sizeof(*info));

    memset(info, 0, sizeof(*info));

    set_irn_link(node, info);
  }
  return info;
}

Michael Beck's avatar
Michael Beck committed
132
/**
Michael Beck's avatar
Michael Beck committed
133
 * update the projection info for a Load/Store
Michael Beck's avatar
Michael Beck committed
134
 */
Michael Beck's avatar
Michael Beck committed
135
static int update_projs(ldst_info_t *info, ir_node *proj)
Michael Beck's avatar
Michael Beck committed
136
137
138
139
140
141
142
143
{
  long nr = get_Proj_proj(proj);

  assert(0 <= nr && nr <= MAX_PROJ && "Wrong proj from LoadStore");

  if (info->projs[nr]) {
    /* there is already one, do CSE */
    exchange(proj, info->projs[nr]);
Michael Beck's avatar
Michael Beck committed
144
    return 1;
Michael Beck's avatar
Michael Beck committed
145
  }
Michael Beck's avatar
Michael Beck committed
146
  else {
Michael Beck's avatar
Michael Beck committed
147
    info->projs[nr] = proj;
Michael Beck's avatar
Michael Beck committed
148
149
150
151
152
153
154
155
156
157
158
159
160
161
    return 0;
  }
}

/**
 * update the exception block info for a Load/Store
 */
static int update_exc(ldst_info_t *info, ir_node *block, int pos)
{
  assert(info->exc_block == NULL && "more than one exception block found");

  info->exc_block = block;
  info->exc_idx   = pos;
  return 0;
Michael Beck's avatar
Michael Beck committed
162
163
}

164
165
166
#define get_irn_out_n(node)     (unsigned)get_irn_link(node)
#define set_irn_out_n(node, n)  set_irn_link(adr, (void *)(n))

Michael Beck's avatar
Michael Beck committed
167
168
/**
 * walker, collects all Load/Store/Proj nodes
169
170
 *
 * walks form Start -> End
Michael Beck's avatar
Michael Beck committed
171
 */
Michael Beck's avatar
Michael Beck committed
172
static void collect_nodes(ir_node *node, void *env)
Michael Beck's avatar
Michael Beck committed
173
{
174
  ir_op       *op = get_irn_op(node);
Michael Beck's avatar
Michael Beck committed
175
  ir_node     *pred;
176
  ldst_info_t *ldst_info;
Michael Beck's avatar
Michael Beck committed
177
178
  walk_env_t  *wenv = env;

179
  if (op == op_Proj) {
180
181
182
    ir_node *adr;
    ir_op *op;

Michael Beck's avatar
Michael Beck committed
183
    pred = get_Proj_pred(node);
184
    op   = get_irn_op(pred);
Michael Beck's avatar
Michael Beck committed
185

186
    if (op == op_Load) {
187
      ldst_info = get_ldst_info(pred, wenv);
Michael Beck's avatar
Michael Beck committed
188

189
      wenv->changes |= update_projs(ldst_info, node);
190

191
192
193
194
195
196
      if ((ldst_info->flags & LDST_VISITED) == 0) {
        adr = get_Load_ptr(pred);
        set_irn_out_n(adr, get_irn_out_n(adr) + 1);

        ldst_info->flags |= LDST_VISITED;
      }
197
198
199
200
201
202
    }
    else if (op == op_Store) {
      ldst_info = get_ldst_info(pred, wenv);

      wenv->changes |= update_projs(ldst_info, node);

203
204
205
206
207
208
      if ((ldst_info->flags & LDST_VISITED) == 0) {
        adr = get_Store_ptr(pred);
        set_irn_out_n(adr, get_irn_out_n(adr) + 1);

        ldst_info->flags |= LDST_VISITED;
      }
Michael Beck's avatar
Michael Beck committed
209
210
    }
  }
211
  else if (op == op_Block) { /* check, if it's an exception block */
Michael Beck's avatar
Michael Beck committed
212
213
214
    int i, n;

    for (i = 0, n = get_Block_n_cfgpreds(node); i < n; ++i) {
215
216
217
      ir_node      *pred_block;
      block_info_t *bl_info;

Michael Beck's avatar
Michael Beck committed
218
219
      pred = skip_Proj(get_Block_cfgpred(node, i));

220
221
222
223
224
225
226
227
228
229
230
231
      /* ignore Bad predecessors, they will be removed later */
      if (is_Bad(pred))
	continue;

      pred_block = get_nodes_block(pred);
      bl_info    = get_block_info(pred_block, wenv);

      if (is_fragile_op(pred))
	bl_info->flags |= BLOCK_HAS_EXC;
      else if (is_forking_op(pred))
	bl_info->flags |= BLOCK_HAS_COND;

Michael Beck's avatar
Michael Beck committed
232
      if (get_irn_op(pred) == op_Load || get_irn_op(pred) == op_Store) {
233
        ldst_info = get_ldst_info(pred, wenv);
Michael Beck's avatar
Michael Beck committed
234

235
        wenv->changes |= update_exc(ldst_info, node, i);
Michael Beck's avatar
Michael Beck committed
236
      }
Michael Beck's avatar
Michael Beck committed
237
238
239
240
    }
  }
}

Michael Beck's avatar
Michael Beck committed
241
/**
242
 * Returns an entity if the address ptr points to a constant one.
Michael Beck's avatar
Michael Beck committed
243
244
245
246
247
248
249
250
251
252
253
254
255
 */
static entity *find_constant_entity(ir_node *ptr)
{
  for (;;) {
    ir_op *op = get_irn_op(ptr);

    if (op == op_SymConst && (get_SymConst_kind(ptr) == symconst_addr_ent)) {
      return get_SymConst_entity(ptr);
    }
    else if (op == op_Sel) {
      entity *ent = get_Sel_entity(ptr);
      type *tp    = get_entity_owner(ent);

256
257
258
259
260
261
262
263
264
      /* Do not fiddle about polymorphy. */
      if (is_Class_type(get_entity_owner(ent)) &&
	  ((get_entity_n_overwrites(ent)    != 0) ||
	   (get_entity_n_overwrittenby(ent) != 0)   ) )
	return NULL;

      if (variability_constant == get_entity_variability(ent))
	return ent;

265
      if (is_Array_type(tp)) {
Michael Beck's avatar
Michael Beck committed
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
        /* check bounds */
        int i, n;

        for (i = 0, n = get_Sel_n_indexs(ptr); i < n; ++i) {
          ir_node *bound;
          tarval *tlower, *tupper;
          ir_node *index = get_Sel_index(ptr, i);
          tarval *tv     = computed_value(index);

          /* check if the index is constant */
          if (tv == tarval_bad)
            return NULL;

          bound  = get_array_lower_bound(tp, i);
          tlower = computed_value(bound);
          bound  = get_array_upper_bound(tp, i);
          tupper = computed_value(bound);

          if (tlower == tarval_bad || tupper == tarval_bad)
            return NULL;

287
          if (tarval_cmp(tv, tlower) & pn_Cmp_Lt)
Michael Beck's avatar
Michael Beck committed
288
            return NULL;
289
          if (tarval_cmp(tupper, tv) & pn_Cmp_Lt)
Michael Beck's avatar
Michael Beck committed
290
291
292
293
294
295
296
297
298
299
300
301
302
303
            return NULL;

          /* ok, bounds check finished */
        }
      }

      /* try next */
      ptr = get_Sel_ptr(ptr);
    }
    else
      return NULL;
  }
}

304
305
306
307
308
309
static long get_Sel_array_index_long(ir_node *n, int dim) {
  ir_node *index = get_Sel_index(n, dim);
  assert(get_irn_op(index) == op_Const);
  return get_tarval_long(get_Const_tarval(index));
}

Götz Lindenmaier's avatar
bugfix    
Götz Lindenmaier committed
310
static compound_graph_path *rec_get_accessed_path(ir_node *ptr, int depth) {
Michael Beck's avatar
Michael Beck committed
311
312
313
314
  compound_graph_path *res = NULL;
  entity              *root, *field;
  int                 path_len, pos;

315
316
  if (get_irn_op(ptr) == op_SymConst) {
    assert(get_SymConst_kind(ptr) == symconst_addr_ent);
Michael Beck's avatar
Michael Beck committed
317
    root = get_SymConst_entity(ptr);
Götz Lindenmaier's avatar
Götz Lindenmaier committed
318
    res = (depth == 0) ? NULL : new_compound_graph_path(get_entity_type(root), depth);
Michael Beck's avatar
Michael Beck committed
319
320
  }
  else {
321
322
    assert(get_irn_op(ptr) == op_Sel);
    res = rec_get_accessed_path(get_Sel_ptr(ptr), depth+1);
Michael Beck's avatar
Michael Beck committed
323
324
325
    field = get_Sel_entity(ptr);
    path_len = get_compound_graph_path_length(res);
    pos = path_len - depth - 1;
326
327
328
329
330
331
332
333
334
    set_compound_graph_path_node(res, pos, field);
    if (is_Array_type(get_entity_owner(field))) {
      assert(get_Sel_n_indexs(ptr) == 1 && "multi dim arrays not implemented");
      set_compound_graph_path_array_index(res, pos, get_Sel_array_index_long(ptr, 0));
    }
  }
  return res;
}

Götz Lindenmaier's avatar
bugfix    
Götz Lindenmaier committed
335
336
337
338

/** Returns an access path or NULL.  The access path is only
 *  valid, if the graph is in phase_high and _no_ address computation is used. */
static compound_graph_path *get_accessed_path(ir_node *ptr) {
339
340
341
  return rec_get_accessed_path(ptr, 0);
}

Michael Beck's avatar
Michael Beck committed
342
343
344
345
346
347
348
/**
 * optimize a Load
 */
static int optimize_load(ir_node *load)
{
  ldst_info_t *info = get_irn_link(load);
  ir_mode *load_mode = get_Load_mode(load);
Michael Beck's avatar
Michael Beck committed
349
  ir_node *pred, *mem, *ptr, *new_node;
Michael Beck's avatar
Michael Beck committed
350
  entity *ent;
351
  int res = 0;
Michael Beck's avatar
Michael Beck committed
352

353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
  /* the address of the load to be optimized */
  ptr = get_Load_ptr(load);

  /*
   * Check if we can remove the exception form a Load:
   * this can be done, if the address is from an Sel(Alloc) and
   * the Sel type is a subtype of the alloc type.
   *
   * This optimizes some often used OO constructs,
   * like x = new O; x->t;
   */
  if (info->projs[pn_Load_X_except]) {
    if (get_irn_op(ptr) == op_Sel) {
      ir_node *mem = get_Sel_mem(ptr);

Götz Lindenmaier's avatar
Götz Lindenmaier committed
368
      if (get_irn_op(skip_Proj(mem)) == op_Alloc) {
369
370
371
372
373
374
375
376
377
378
379
380
381
382
        /* ok, check the types */
        entity *ent  = get_Sel_entity(ptr);
        type *s_type = get_entity_type(ent);
        type *a_type = get_Alloc_type(mem);

        if (is_subclass_of(s_type, a_type)) {
          /* ok, condition met: there can't be an exception because
           * alloc guarantees that enough memory was allocated */

          exchange(info->projs[pn_Load_X_except], new_Bad());
          info->projs[pn_Load_X_except] = NULL;
        }
      }
    }
383
384
    else if ((get_irn_op(skip_Proj(ptr)) == op_Alloc) ||
	     ((get_irn_op(ptr) == op_Cast) && (get_irn_op(skip_Proj(get_Cast_op(ptr))) == op_Alloc))) {
385
386
387
388
389
390
391
392
393
394
      /* simple case: a direct load after an Alloc. Firm Alloc throw
       * an exception in case of out-of-memory. So, there is no way for an
       * exception in this load.
       * This code is constructed by the "exception lowering" in the Jack compiler.
       */
       exchange(info->projs[pn_Load_X_except], new_Bad());
       info->projs[pn_Load_X_except] = NULL;
    }
  }

395
  /* do NOT touch volatile loads for now */
Michael Beck's avatar
Michael Beck committed
396
397
398
399
400
  if (get_Load_volatility(load) == volatility_is_volatile)
    return 0;

  if (! info->projs[pn_Load_res] && ! info->projs[pn_Load_X_except]) {
    /* a Load which value is neither used nor exception checked, remove it */
401
    mem  = get_Load_mem(load);
Michael Beck's avatar
Michael Beck committed
402
    exchange(info->projs[pn_Load_M], mem);
403
404

    return 1;
Michael Beck's avatar
Michael Beck committed
405
  }
Michael Beck's avatar
Michael Beck committed
406

407
  /* the mem of the Load. Must still be returned after optimization */
408
409
  mem  = get_Load_mem(load);

410
411
  /* Load from a constant polymorphic field, where we can resolve
     polymorphy. */
Michael Beck's avatar
Michael Beck committed
412
  new_node = transform_node_Load(load);
413
414
415
416
417
418
419
420
421
422
423
424
425
426
  if (new_node != load) {
    if (info->projs[pn_Load_M]) {
      exchange(info->projs[pn_Load_M], mem);
      info->projs[pn_Load_M] = NULL;
    }
    if (info->projs[pn_Load_X_except]) {
      exchange(info->projs[pn_Load_X_except], new_Bad());
      info->projs[pn_Load_X_except] = NULL;
    }
    if (info->projs[pn_Load_res])
      exchange(info->projs[pn_Load_res], new_node);
    return 1;
  }

Michael Beck's avatar
Michael Beck committed
427
428
429
  /* check if we can determine the entity that will be loaded */
  ent = find_constant_entity(ptr);
  if (ent) {
430
431
432
433
434
435
436
437
438
439
440
    if ((allocation_static == get_entity_allocation(ent)) &&
        (visibility_external_allocated != get_entity_visibility(ent))) {
      /* a static allocation that is not external: there should be NO exception
       * when loading. */

      /* no exception, clear the info field as it might be checked later again */
      if (info->projs[pn_Load_X_except]) {
        exchange(info->projs[pn_Load_X_except], new_Bad());
        info->projs[pn_Load_X_except] = NULL;
      }

Götz Lindenmaier's avatar
bugfix    
Götz Lindenmaier committed
441
      if (variability_constant == get_entity_variability(ent)
Michael Beck's avatar
Michael Beck committed
442
443
444
445
446
	        && is_atomic_entity(ent)) {
        /* Might not be atomic after
           lowering of Sels.  In this
           case we could also load, but
           it's more complicated. */
447
448
449
450
451
452
453
454
455
        /* more simpler case: we load the content of a constant value:
         * replace it by the constant itself
         */

        /* no memory */
        if (info->projs[pn_Load_M])
          exchange(info->projs[pn_Load_M], mem);

        /* no result :-) */
Michael Beck's avatar
Michael Beck committed
456
457
458
        if (info->projs[pn_Load_res]) {
          if (is_atomic_entity(ent)) {
            ir_node *c = copy_const_value(get_atomic_ent_value(ent));
459

Michael Beck's avatar
Michael Beck committed
460
461
462
463
464
465
466
467
            DBG_OPT_RC(load, c);
            exchange(info->projs[pn_Load_res], c);

            return 1;
          }
        }
      }
      else if (variability_constant == get_entity_variability(ent)) {
Michael Beck's avatar
Michael Beck committed
468
        compound_graph_path *path;
Götz Lindenmaier's avatar
Götz Lindenmaier committed
469
	/*
Michael Beck's avatar
Michael Beck committed
470
        printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
Michael Beck's avatar
Michael Beck committed
471
472
473
        get_entity_name(get_irg_entity(current_ir_graph)));
        printf("  load: "); DDMN(load);
        printf("  ptr:  "); DDMN(ptr);
Götz Lindenmaier's avatar
Götz Lindenmaier committed
474
	*/
Michael Beck's avatar
Michael Beck committed
475
476
477
478
479
480
481
        path = get_accessed_path(ptr);
        if (path) {
          ir_node *c;

          assert(is_proper_compound_graph_path(path, get_compound_graph_path_length(path)-1));
          c = get_compound_ent_value_by_path(ent, path);

Götz Lindenmaier's avatar
Götz Lindenmaier committed
482
          /* printf("  cons: "); DDMN(c); */
Michael Beck's avatar
Michael Beck committed
483
484
485
486
487

          if (info->projs[pn_Load_M])
            exchange(info->projs[pn_Load_M], mem);
          if (info->projs[pn_Load_res])
            exchange(info->projs[pn_Load_res], copy_const_value(c));
Götz Lindenmaier's avatar
Götz Lindenmaier committed
488
          /*
Michael Beck's avatar
Michael Beck committed
489
490
491
492
493
494
495
496
497
498
          {
            int j;
            for (j = 0; j < get_compound_graph_path_length(path); ++j) {
              entity *node = get_compound_graph_path_node(path, j);
              fprintf(stdout, ".%s", get_entity_name(node));
              if (is_Array_type(get_entity_owner(node)))
                      fprintf(stdout, "[%d]", get_compound_graph_path_array_index(path, j));
            }
            printf("\n");
          }
Götz Lindenmaier's avatar
Götz Lindenmaier committed
499
500
501
502
503
504
505
506
507
508
509
	  */
        } else {
	  /*  We can not determine a correct access path.  E.g., in jack, we load
	      a byte from an object to generate an exception.   Happens in test program
	      Reflectiontest.
	  printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
		 get_entity_name(get_irg_entity(current_ir_graph)));
	  printf("  load: "); DDMN(load);
	  printf("  ptr:  "); DDMN(ptr);
	  if (get_irn_op(ptr) == op_SymConst &&
		get_SymConst_kind(ptr) == symconst_addr_ent) { printf("        "); DDMEO(get_SymConst_entity(ptr)); }
Michael Beck's avatar
Michael Beck committed
510
          printf("cannot optimize.\n");
Götz Lindenmaier's avatar
Götz Lindenmaier committed
511
512
	  */
	}
513
514
515
516
517
518
519
      }

      /* we changed the irg, but try further */
      res = 1;
    }
  }

520
521
522
523
524
  /* Check, if the address of this load is used more than once.
   * If not, this load cannot be removed in any case. */
  if (get_irn_out_n(ptr) <= 1)
    return 0;

525
526
  /* follow the memory chain as long as there are only Loads */
  for (pred = skip_Proj(mem); ; pred = skip_Proj(get_Load_mem(pred))) {
Michael Beck's avatar
Michael Beck committed
527
528

    /*
529
530
531
532
     * BEWARE: one might think that checking the modes is useless, because
     * if the pointers are identical, they refer to the same object.
     * This is only true in strong typed languages, not is C were the following
     * is possible a = *(type1 *)p; b = *(type2 *)p ...
Michael Beck's avatar
Michael Beck committed
533
534
     */

535
    if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
536
537
538
        get_irn_mode(get_Store_value(pred)) == load_mode) {
      ldst_info_t *pred_info = get_irn_link(pred);

539
      /*
540
541
       * a Load immediately after a Store -- a read after write.
       * We may remove the Load, if both Load & Store does not have an exception handler
542
543
       * OR they are in the same block. In the latter case the Load cannot
       * throw an exception when the previous Store was quiet.
544
545
546
547
       *
       * Why we need to check for Store Exc? If the Store cannot be executed (ROM)
       * the exception handler might simply jump into the load block :-(
       * We could make it a little bit better if we would know that the exception
548
       * handler of the Store jumps directly to the end...
549
       */
550
551
      if ((!pred_info->projs[pn_Store_X_except] && !info->projs[pn_Load_X_except]) ||
          get_nodes_block(load) == get_nodes_block(pred)) {
Michael Beck's avatar
Michael Beck committed
552
553
554
555
        ir_node *value = get_Store_value(pred);

        DBG_OPT_RAW(load, value);
        exchange(info->projs[pn_Load_res], value);
556
557
558
559
560
561
562

        if (info->projs[pn_Load_M])
          exchange(info->projs[pn_Load_M], mem);

        /* no exception */
        if (info->projs[pn_Load_X_except])
          exchange( info->projs[pn_Load_X_except], new_Bad());
563
        return 1;
Michael Beck's avatar
Michael Beck committed
564
      }
565
566
567
568
    }
    else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
             get_Load_mode(pred) == load_mode) {
      /*
569
       * a Load after a Load -- a read after read.
570
571
572
       * We may remove the second Load, if it does not have an exception handler
       * OR they are in the same block. In the later case the Load cannot
       * throw an exception when the previous Load was quiet.
573
       *
574
       * Here, there is no need to check if the previos Load has an exception hander because
575
       * they would have exact the same exception...
576
577
578
579
       */
      if (! info->projs[pn_Load_X_except] || get_nodes_block(load) == get_nodes_block(pred)) {
        ldst_info_t *pred_info = get_irn_link(pred);

Michael Beck's avatar
Michael Beck committed
580
        DBG_OPT_RAR(load, pred);
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603

        if (pred_info->projs[pn_Load_res]) {
          /* we need a data proj from the previous load for this optimization */
          exchange( info->projs[pn_Load_res], pred_info->projs[pn_Load_res] );
          if (info->projs[pn_Load_M])
            exchange(info->projs[pn_Load_M], mem);
        }
        else {
          if (info->projs[pn_Load_res]) {
            set_Proj_pred(info->projs[pn_Load_res], pred);
            set_nodes_block(info->projs[pn_Load_res], get_nodes_block(pred));
          }
          if (info->projs[pn_Load_M]) {
            /* Actually, this if should not be necessary.  Construct the Loads
               properly!!! */
            exchange(info->projs[pn_Load_M], mem);
          }
        }

        /* no exception */
        if (info->projs[pn_Load_X_except])
          exchange(info->projs[pn_Load_X_except], new_Bad());

604
        return 1;
Michael Beck's avatar
Michael Beck committed
605
606
      }
    }
607

608
    /* follow only Load chains */
609
610
611
    if (get_irn_op(pred) != op_Load)
      break;
   }
Michael Beck's avatar
Michael Beck committed
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
  return res;
}

/**
 * optimize a Store
 */
static int optimize_store(ir_node *store)
{
  ldst_info_t *info = get_irn_link(store);
  ir_node *pred, *mem, *ptr, *value, *block;
  ir_mode *mode;
  int res = 0;

  if (get_Store_volatility(store) == volatility_is_volatile)
    return 0;

  /*
   * BEWARE: one might think that checking the modes is useless, because
   * if the pointers are identical, they refer to the same object.
   * This is only true in strong typed languages, not is C were the following
   * is possible *(type1 *)p = a; *(type2 *)p = b ...
   */

  ptr   = get_Store_ptr(store);
636
637
638
639
640
641
642

  /* Check, if the address of this load is used more than once.
   * If not, this load cannot be removed in any case. */
  if (get_irn_out_n(ptr) <= 1)
    return 0;

  block = get_nodes_block(store);
Michael Beck's avatar
Michael Beck committed
643
644
645
646
  mem   = get_Store_mem(store);
  value = get_Store_value(store);
  mode  = get_irn_mode(value);

647
648
649
  /* follow the memory chain as long as there are only Loads */
  for (pred = skip_Proj(mem); ; pred = skip_Proj(get_Load_mem(pred))) {
    ldst_info_t *pred_info = get_irn_link(pred);
Michael Beck's avatar
Michael Beck committed
650

651
652
653
    if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
        get_nodes_block(pred) == block && get_irn_mode(get_Store_value(pred)) == mode) {
      /*
654
       * a Store after a Store in the same block -- a write after write.
655
656
657
658
659
660
661
662
663
       * We may remove the first Store, if it does not have an exception handler.
       *
       * TODO: What, if both have the same exception handler ???
       */
      if (get_Store_volatility(pred) != volatility_is_volatile && !pred_info->projs[pn_Store_X_except]) {
        DBG_OPT_WAW(pred, store);
        exchange( pred_info->projs[pn_Store_M], get_Store_mem(pred) );
        return 1;
      }
Michael Beck's avatar
Michael Beck committed
664
    }
665
666
667
    else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
             value == pred_info->projs[pn_Load_res]) {
      /*
668
       * a Store of a value after a Load -- a write after read.
669
670
671
       * We may remove the second Store, if it does not have an exception handler.
       */
      if (! info->projs[pn_Store_X_except]) {
Michael Beck's avatar
Michael Beck committed
672
        DBG_OPT_WAR(store, pred);
673
674
675
        exchange( info->projs[pn_Store_M], mem );
        return 1;
      }
Michael Beck's avatar
Michael Beck committed
676
    }
677

678
    /* follow only Load chains */
679
680
    if (get_irn_op(pred) != op_Load)
      break;
Michael Beck's avatar
Michael Beck committed
681
682
683
684
  }
  return res;
}

Michael Beck's avatar
Michael Beck committed
685
686
687
688
689
690
691
692
693
694
695
696
/**
 * walker, optimizes Phi after Stores:
 * Does the following optimization:
 *
 *   val1   val2   val3          val1  val2  val3
 *    |      |      |               \    |    /
 *   Str    Str    Str               \   |   /
 *      \    |    /                     Phi
 *       \   |   /                       |
 *        \  |  /                       Str
 *          Phi
 *
697
 * This removes the number of stores and allows for predicated execution.
Michael Beck's avatar
Michael Beck committed
698
699
 * Moves Stores back to the end of a function which may be bad
 *
700
 * Is only allowed if the predecessor blocks have only one successor.
Michael Beck's avatar
Michael Beck committed
701
 */
702
static int optimize_phi(ir_node *phi, void *env)
Michael Beck's avatar
Michael Beck committed
703
{
704
  walk_env_t *wenv = env;
Michael Beck's avatar
Michael Beck committed
705
  int i, n;
706
  ir_node *store, *old_store, *ptr, *block, *phiM, *phiD, *exc, *projM;
Michael Beck's avatar
Michael Beck committed
707
708
709
710
711
  ir_mode *mode;
  ir_node **inM, **inD;
  int *idx;
  dbg_info *db = NULL;
  ldst_info_t *info;
712
  block_info_t *bl_info;
Michael Beck's avatar
Michael Beck committed
713
714
715
716
717
718
719
720
721
722

  /* Must be a memory Phi */
  if (get_irn_mode(phi) != mode_M)
    return 0;

  n = get_Phi_n_preds(phi);
  if (n <= 0)
    return 0;

  store = skip_Proj(get_Phi_pred(phi, 0));
723
  old_store = store;
Michael Beck's avatar
Michael Beck committed
724
725
726
  if (get_irn_op(store) != op_Store)
    return 0;

727
728
729
730
731
732
733
734
735
  /* abort on bad blocks */
  if (is_Bad(get_nodes_block(store)))
    return 0;

  /* check if the block has only one output */
  bl_info = get_irn_link(get_nodes_block(store));
  if (bl_info->flags)
    return 0;

Michael Beck's avatar
Michael Beck committed
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
  /* this is the address of the store */
  ptr  = get_Store_ptr(store);
  mode = get_irn_mode(get_Store_value(store));
  info = get_irn_link(store);
  exc  = info->exc_block;

  for (i = 1; i < n; ++i) {
    ir_node *pred = skip_Proj(get_Phi_pred(phi, i));

    if (get_irn_op(pred) != op_Store)
      return 0;

    if (mode != get_irn_mode(get_Store_value(pred)) || ptr != get_Store_ptr(pred))
      return 0;

    info = get_irn_link(pred);

    /* check, if all stores have the same exception flow */
    if (exc != info->exc_block)
      return 0;
756
757
758
759
760
761
762
763
764

    /* abort on bad blocks */
    if (is_Bad(get_nodes_block(store)))
      return 0;

    /* check if the block has only one output */
    bl_info = get_irn_link(get_nodes_block(store));
    if (bl_info->flags)
      return 0;
Michael Beck's avatar
Michael Beck committed
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
  }

  /*
   * ok, when we are here, we found all predecessors of a Phi that
   * are Stores to the same address. That means whatever we do before
   * we enter the block of the Phi, we do a Store.
   * So, we can move the store to the current block:
   *
   *   val1    val2    val3          val1  val2  val3
   *    |       |       |               \    |    /
   * | Str | | Str | | Str |             \   |   /
   *      \     |     /                     Phi
   *       \    |    /                       |
   *        \   |   /                       Str
   *           Phi
   *
781
   * Is only allowed if the predecessor blocks have only one successor.
Michael Beck's avatar
Michael Beck committed
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
   */

  /* first step: collect all inputs */
  NEW_ARR_A(ir_node *, inM, n);
  NEW_ARR_A(ir_node *, inD, n);
  NEW_ARR_A(int, idx, n);

  for (i = 0; i < n; ++i) {
    ir_node *pred = skip_Proj(get_Phi_pred(phi, i));
    info = get_irn_link(pred);

    inM[i] = get_Store_mem(pred);
    inD[i] = get_Store_value(pred);
    idx[i] = info->exc_idx;
  }
  block = get_nodes_block(phi);

  /* second step: create a new memory Phi */
  phiM = new_rd_Phi(get_irn_dbg_info(phi), current_ir_graph, block, n, inM, mode_M);

  /* third step: create a new data Phi */
  phiD = new_rd_Phi(get_irn_dbg_info(phi), current_ir_graph, block, n, inD, mode);

  /* fourth step: create the Store */
  store = new_rd_Store(db, current_ir_graph, block, phiM, ptr, phiD);
807
808
809
810
#ifdef DO_CACHEOPT
  co_set_irn_name(store, co_get_irn_ident(old_store));
#endif

811
812
813
814
  projM = new_rd_Proj(NULL, current_ir_graph, block, store, mode_M, pn_Store_M);

  info = get_ldst_info(store, wenv);
  info->projs[pn_Store_M] = projM;
Michael Beck's avatar
Michael Beck committed
815
816
817
818
819

  /* fifths step: repair exception flow */
  if (exc) {
    ir_node *projX = new_rd_Proj(NULL, current_ir_graph, block, store, mode_X, pn_Store_X_except);

820
821
822
823
    info->projs[pn_Store_X_except] = projX;
    info->exc_block                = exc;
    info->exc_idx                  = idx[0];

Michael Beck's avatar
Michael Beck committed
824
825
826
827
828
829
830
831
832
833
    for (i = 0; i < n; ++i) {
      set_Block_cfgpred(exc, idx[i], projX);
    }

    if (n > 1) {
      /* the exception block should be optimized as some inputs are identical now */
    }
  }

  /* sixt step: replace old Phi */
834
  exchange(phi, projM);
Michael Beck's avatar
Michael Beck committed
835
836
837
838

  return 1;
}

Michael Beck's avatar
Michael Beck committed
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
/**
 * walker, collects all Load/Store/Proj nodes
 */
static void do_load_store_optimize(ir_node *n, void *env)
{
  walk_env_t *wenv = env;

  switch (get_irn_opcode(n)) {

  case iro_Load:
    wenv->changes |= optimize_load(n);
    break;

  case iro_Store:
    wenv->changes |= optimize_store(n);
    break;

856
857
  case iro_Phi:
    wenv->changes |= optimize_phi(n, env);
Michael Beck's avatar
Michael Beck committed
858

Michael Beck's avatar
Michael Beck committed
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
  default:
    ;
  }
}

/*
 * do the load store optimization
 */
void optimize_load_store(ir_graph *irg)
{
  walk_env_t env;

  assert(get_irg_phase_state(irg) != phase_building);

  if (!get_opt_redundant_LoadStore())
    return;

  obstack_init(&env.obst);
  env.changes = 0;

  /* init the links, then collect Loads/Stores/Proj's in lists */
  irg_walk_graph(irg, init_links, collect_nodes, &env);

  /* now we have collected enough information, optimize */
  irg_walk_graph(irg, NULL, do_load_store_optimize, &env);

  obstack_free(&env.obst, NULL);

  /* Handle graph state */
  if (env.changes) {
    if (get_irg_outs_state(current_ir_graph) == outs_consistent)
      set_irg_outs_inconsistent(current_ir_graph);

    /* is this really needed: Yes, as exception block may get bad but this might be tested */
    if (get_irg_dom_state(current_ir_graph) == dom_consistent)
      set_irg_dom_inconsistent(current_ir_graph);
  }
}