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1 /* Data references and dependences detectors.
2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Sebastian Pop <pop@cri.ensmp.fr>
5
6 This file is part of GCC.
7
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
11 version.
12
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
21
22 #ifndef GCC_TREE_DATA_REF_H
23 #define GCC_TREE_DATA_REF_H
24
25 #include "graphds.h"
26 #include "lambda.h"
27 #include "omega.h"
28 #include "tree-chrec.h"
29
30 /*
31 innermost_loop_behavior describes the evolution of the address of the memory
32 reference in the innermost enclosing loop. The address is expressed as
33 BASE + STEP * # of iteration, and base is further decomposed as the base
34 pointer (BASE_ADDRESS), loop invariant offset (OFFSET) and
35 constant offset (INIT). Examples, in loop nest
36
37 for (i = 0; i < 100; i++)
38 for (j = 3; j < 100; j++)
39
40 Example 1 Example 2
41 data-ref a[j].b[i][j] *(p + x + 16B + 4B * j)
42
43
44 innermost_loop_behavior
45 base_address &a p
46 offset i * D_i x
47 init 3 * D_j + offsetof (b) 28
48 step D_j 4
49
50 */
51 struct innermost_loop_behavior
52 {
53 tree base_address;
54 tree offset;
55 tree init;
56 tree step;
57
58 /* Alignment information. ALIGNED_TO is set to the largest power of two
59 that divides OFFSET. */
60 tree aligned_to;
61 };
62
63 /* Describes the evolutions of indices of the memory reference. The indices
64 are indices of the ARRAY_REFs and the operands of INDIRECT_REFs.
65 For ARRAY_REFs, BASE_OBJECT is the reference with zeroed indices
66 (note that this reference does not have to be valid, if zero does not
67 belong to the range of the array; hence it is not recommended to use
68 BASE_OBJECT in any code generation). For INDIRECT_REFs, the address is
69 set to the loop-invariant part of the address of the object, except for
70 the constant offset. For the examples above,
71
72 base_object: a[0].b[0][0] *(p + x + 4B * j_0)
73 indices: {j_0, +, 1}_2 {16, +, 4}_2
74 {i_0, +, 1}_1
75 {j_0, +, 1}_2
76 */
77
78 struct indices
79 {
80 /* The object. */
81 tree base_object;
82
83 /* A list of chrecs. Access functions of the indices. */
84 VEC(tree,heap) *access_fns;
85 };
86
87 struct dr_alias
88 {
89 /* The alias information that should be used for new pointers to this
90 location. SYMBOL_TAG is either a DECL or a SYMBOL_MEMORY_TAG. */
91 struct ptr_info_def *ptr_info;
92
93 /* The set of virtual operands corresponding to this memory reference,
94 serving as a description of the alias information for the memory
95 reference. This could be eliminated if we had alias oracle. */
96 bitmap vops;
97 };
98
99 /* Each vector of the access matrix represents a linear access
100 function for a subscript. First elements correspond to the
101 leftmost indices, ie. for a[i][j] the first vector corresponds to
102 the subscript in "i". The elements of a vector are relative to
103 the loop nests in which the data reference is considered,
104 i.e. the vector is relative to the SCoP that provides the context
105 in which this data reference occurs.
106
107 For example, in
108
109 | loop_1
110 | loop_2
111 | a[i+3][2*j+n-1]
112
113 if "i" varies in loop_1 and "j" varies in loop_2, the access
114 matrix with respect to the loop nest {loop_1, loop_2} is:
115
116 | loop_1 loop_2 param_n cst
117 | 1 0 0 3
118 | 0 2 1 -1
119
120 whereas the access matrix with respect to loop_2 considers "i" as
121 a parameter:
122
123 | loop_2 param_i param_n cst
124 | 0 1 0 3
125 | 2 0 1 -1
126 */
127 struct access_matrix
128 {
129 VEC (loop_p, heap) *loop_nest;
130 int nb_induction_vars;
131 VEC (tree, heap) *parameters;
132 VEC (lambda_vector, gc) *matrix;
133 };
134
135 #define AM_LOOP_NEST(M) (M)->loop_nest
136 #define AM_NB_INDUCTION_VARS(M) (M)->nb_induction_vars
137 #define AM_PARAMETERS(M) (M)->parameters
138 #define AM_MATRIX(M) (M)->matrix
139 #define AM_NB_PARAMETERS(M) (VEC_length (tree, AM_PARAMETERS(M)))
140 #define AM_CONST_COLUMN_INDEX(M) (AM_NB_INDUCTION_VARS (M) + AM_NB_PARAMETERS (M))
141 #define AM_NB_COLUMNS(M) (AM_NB_INDUCTION_VARS (M) + AM_NB_PARAMETERS (M) + 1)
142 #define AM_GET_SUBSCRIPT_ACCESS_VECTOR(M, I) VEC_index (lambda_vector, AM_MATRIX (M), I)
143 #define AM_GET_ACCESS_MATRIX_ELEMENT(M, I, J) AM_GET_SUBSCRIPT_ACCESS_VECTOR (M, I)[J]
144
145 /* Return the column in the access matrix of LOOP_NUM. */
146
147 static inline int
148 am_vector_index_for_loop (struct access_matrix *access_matrix, int loop_num)
149 {
150 int i;
151 loop_p l;
152
153 for (i = 0; VEC_iterate (loop_p, AM_LOOP_NEST (access_matrix), i, l); i++)
154 if (l->num == loop_num)
155 return i;
156
157 gcc_unreachable();
158 }
159
160 int access_matrix_get_index_for_parameter (tree, struct access_matrix *);
161
162 struct data_reference
163 {
164 /* A pointer to the statement that contains this DR. */
165 gimple stmt;
166
167 /* A pointer to the memory reference. */
168 tree ref;
169
170 /* Auxiliary info specific to a pass. */
171 void *aux;
172
173 /* True when the data reference is in RHS of a stmt. */
174 bool is_read;
175
176 /* Behavior of the memory reference in the innermost loop. */
177 struct innermost_loop_behavior innermost;
178
179 /* Subscripts of this data reference. */
180 struct indices indices;
181
182 /* Alias information for the data reference. */
183 struct dr_alias alias;
184
185 /* Matrix representation for the data access functions. */
186 struct access_matrix *access_matrix;
187 };
188
189 #define DR_STMT(DR) (DR)->stmt
190 #define DR_REF(DR) (DR)->ref
191 #define DR_BASE_OBJECT(DR) (DR)->indices.base_object
192 #define DR_ACCESS_FNS(DR) (DR)->indices.access_fns
193 #define DR_ACCESS_FN(DR, I) VEC_index (tree, DR_ACCESS_FNS (DR), I)
194 #define DR_NUM_DIMENSIONS(DR) VEC_length (tree, DR_ACCESS_FNS (DR))
195 #define DR_IS_READ(DR) (DR)->is_read
196 #define DR_BASE_ADDRESS(DR) (DR)->innermost.base_address
197 #define DR_OFFSET(DR) (DR)->innermost.offset
198 #define DR_INIT(DR) (DR)->innermost.init
199 #define DR_STEP(DR) (DR)->innermost.step
200 #define DR_PTR_INFO(DR) (DR)->alias.ptr_info
201 #define DR_ALIGNED_TO(DR) (DR)->innermost.aligned_to
202 #define DR_ACCESS_MATRIX(DR) (DR)->access_matrix
203
204 typedef struct data_reference *data_reference_p;
205 DEF_VEC_P(data_reference_p);
206 DEF_VEC_ALLOC_P (data_reference_p, heap);
207
208 enum data_dependence_direction {
209 dir_positive,
210 dir_negative,
211 dir_equal,
212 dir_positive_or_negative,
213 dir_positive_or_equal,
214 dir_negative_or_equal,
215 dir_star,
216 dir_independent
217 };
218
219 /* The description of the grid of iterations that overlap. At most
220 two loops are considered at the same time just now, hence at most
221 two functions are needed. For each of the functions, we store
222 the vector of coefficients, f[0] + x * f[1] + y * f[2] + ...,
223 where x, y, ... are variables. */
224
225 #define MAX_DIM 2
226
227 /* Special values of N. */
228 #define NO_DEPENDENCE 0
229 #define NOT_KNOWN (MAX_DIM + 1)
230 #define CF_NONTRIVIAL_P(CF) ((CF)->n != NO_DEPENDENCE && (CF)->n != NOT_KNOWN)
231 #define CF_NOT_KNOWN_P(CF) ((CF)->n == NOT_KNOWN)
232 #define CF_NO_DEPENDENCE_P(CF) ((CF)->n == NO_DEPENDENCE)
233
234 typedef VEC (tree, heap) *affine_fn;
235
236 typedef struct
237 {
238 unsigned n;
239 affine_fn fns[MAX_DIM];
240 } conflict_function;
241
242 /* What is a subscript? Given two array accesses a subscript is the
243 tuple composed of the access functions for a given dimension.
244 Example: Given A[f1][f2][f3] and B[g1][g2][g3], there are three
245 subscripts: (f1, g1), (f2, g2), (f3, g3). These three subscripts
246 are stored in the data_dependence_relation structure under the form
247 of an array of subscripts. */
248
249 struct subscript
250 {
251 /* A description of the iterations for which the elements are
252 accessed twice. */
253 conflict_function *conflicting_iterations_in_a;
254 conflict_function *conflicting_iterations_in_b;
255
256 /* This field stores the information about the iteration domain
257 validity of the dependence relation. */
258 tree last_conflict;
259
260 /* Distance from the iteration that access a conflicting element in
261 A to the iteration that access this same conflicting element in
262 B. The distance is a tree scalar expression, i.e. a constant or a
263 symbolic expression, but certainly not a chrec function. */
264 tree distance;
265 };
266
267 typedef struct subscript *subscript_p;
268 DEF_VEC_P(subscript_p);
269 DEF_VEC_ALLOC_P (subscript_p, heap);
270
271 #define SUB_CONFLICTS_IN_A(SUB) SUB->conflicting_iterations_in_a
272 #define SUB_CONFLICTS_IN_B(SUB) SUB->conflicting_iterations_in_b
273 #define SUB_LAST_CONFLICT(SUB) SUB->last_conflict
274 #define SUB_DISTANCE(SUB) SUB->distance
275
276 /* A data_dependence_relation represents a relation between two
277 data_references A and B. */
278
279 struct data_dependence_relation
280 {
281
282 struct data_reference *a;
283 struct data_reference *b;
284
285 /* A "yes/no/maybe" field for the dependence relation:
286
287 - when "ARE_DEPENDENT == NULL_TREE", there exist a dependence
288 relation between A and B, and the description of this relation
289 is given in the SUBSCRIPTS array,
290
291 - when "ARE_DEPENDENT == chrec_known", there is no dependence and
292 SUBSCRIPTS is empty,
293
294 - when "ARE_DEPENDENT == chrec_dont_know", there may be a dependence,
295 but the analyzer cannot be more specific. */
296 tree are_dependent;
297
298 /* For each subscript in the dependence test, there is an element in
299 this array. This is the attribute that labels the edge A->B of
300 the data_dependence_relation. */
301 VEC (subscript_p, heap) *subscripts;
302
303 /* The analyzed loop nest. */
304 VEC (loop_p, heap) *loop_nest;
305
306 /* The classic direction vector. */
307 VEC (lambda_vector, heap) *dir_vects;
308
309 /* The classic distance vector. */
310 VEC (lambda_vector, heap) *dist_vects;
311
312 /* An index in loop_nest for the innermost loop that varies for
313 this data dependence relation. */
314 unsigned inner_loop;
315
316 /* Is the dependence reversed with respect to the lexicographic order? */
317 bool reversed_p;
318
319 /* When the dependence relation is affine, it can be represented by
320 a distance vector. */
321 bool affine_p;
322
323 /* Set to true when the dependence relation is on the same data
324 access. */
325 bool self_reference_p;
326 };
327
328 typedef struct data_dependence_relation *ddr_p;
329 DEF_VEC_P(ddr_p);
330 DEF_VEC_ALLOC_P(ddr_p,heap);
331
332 #define DDR_A(DDR) DDR->a
333 #define DDR_B(DDR) DDR->b
334 #define DDR_AFFINE_P(DDR) DDR->affine_p
335 #define DDR_ARE_DEPENDENT(DDR) DDR->are_dependent
336 #define DDR_SUBSCRIPTS(DDR) DDR->subscripts
337 #define DDR_SUBSCRIPT(DDR, I) VEC_index (subscript_p, DDR_SUBSCRIPTS (DDR), I)
338 #define DDR_NUM_SUBSCRIPTS(DDR) VEC_length (subscript_p, DDR_SUBSCRIPTS (DDR))
339
340 #define DDR_LOOP_NEST(DDR) DDR->loop_nest
341 /* The size of the direction/distance vectors: the number of loops in
342 the loop nest. */
343 #define DDR_NB_LOOPS(DDR) (VEC_length (loop_p, DDR_LOOP_NEST (DDR)))
344 #define DDR_INNER_LOOP(DDR) DDR->inner_loop
345 #define DDR_SELF_REFERENCE(DDR) DDR->self_reference_p
346
347 #define DDR_DIST_VECTS(DDR) ((DDR)->dist_vects)
348 #define DDR_DIR_VECTS(DDR) ((DDR)->dir_vects)
349 #define DDR_NUM_DIST_VECTS(DDR) \
350 (VEC_length (lambda_vector, DDR_DIST_VECTS (DDR)))
351 #define DDR_NUM_DIR_VECTS(DDR) \
352 (VEC_length (lambda_vector, DDR_DIR_VECTS (DDR)))
353 #define DDR_DIR_VECT(DDR, I) \
354 VEC_index (lambda_vector, DDR_DIR_VECTS (DDR), I)
355 #define DDR_DIST_VECT(DDR, I) \
356 VEC_index (lambda_vector, DDR_DIST_VECTS (DDR), I)
357 #define DDR_REVERSED_P(DDR) DDR->reversed_p
358
359 \f
360
361 /* Describes a location of a memory reference. */
362
363 typedef struct data_ref_loc_d
364 {
365 /* Position of the memory reference. */
366 tree *pos;
367
368 /* True if the memory reference is read. */
369 bool is_read;
370 } data_ref_loc;
371
372 DEF_VEC_O (data_ref_loc);
373 DEF_VEC_ALLOC_O (data_ref_loc, heap);
374
375 bool get_references_in_stmt (gimple, VEC (data_ref_loc, heap) **);
376 bool dr_analyze_innermost (struct data_reference *);
377 extern bool compute_data_dependences_for_loop (struct loop *, bool,
378 VEC (data_reference_p, heap) **,
379 VEC (ddr_p, heap) **);
380 extern bool compute_data_dependences_for_bb (basic_block, bool,
381 VEC (data_reference_p, heap) **,
382 VEC (ddr_p, heap) **);
383 extern tree find_data_references_in_loop (struct loop *,
384 VEC (data_reference_p, heap) **);
385 extern void print_direction_vector (FILE *, lambda_vector, int);
386 extern void print_dir_vectors (FILE *, VEC (lambda_vector, heap) *, int);
387 extern void print_dist_vectors (FILE *, VEC (lambda_vector, heap) *, int);
388 extern void dump_subscript (FILE *, struct subscript *);
389 extern void dump_ddrs (FILE *, VEC (ddr_p, heap) *);
390 extern void dump_dist_dir_vectors (FILE *, VEC (ddr_p, heap) *);
391 extern void dump_data_reference (FILE *, struct data_reference *);
392 extern void debug_data_reference (struct data_reference *);
393 extern void dump_data_references (FILE *, VEC (data_reference_p, heap) *);
394 extern void debug_data_references (VEC (data_reference_p, heap) *);
395 extern void debug_data_dependence_relation (struct data_dependence_relation *);
396 extern void dump_data_dependence_relation (FILE *,
397 struct data_dependence_relation *);
398 extern void dump_data_dependence_relations (FILE *, VEC (ddr_p, heap) *);
399 extern void debug_data_dependence_relations (VEC (ddr_p, heap) *);
400 extern void dump_data_dependence_direction (FILE *,
401 enum data_dependence_direction);
402 extern void free_dependence_relation (struct data_dependence_relation *);
403 extern void free_dependence_relations (VEC (ddr_p, heap) *);
404 extern void free_data_ref (data_reference_p);
405 extern void free_data_refs (VEC (data_reference_p, heap) *);
406 extern bool find_data_references_in_stmt (struct loop *, gimple,
407 VEC (data_reference_p, heap) **);
408 extern bool graphite_find_data_references_in_stmt (struct loop *, gimple,
409 VEC (data_reference_p, heap) **);
410 struct data_reference *create_data_ref (struct loop *, tree, gimple, bool);
411 extern bool find_loop_nest (struct loop *, VEC (loop_p, heap) **);
412 extern void compute_all_dependences (VEC (data_reference_p, heap) *,
413 VEC (ddr_p, heap) **, VEC (loop_p, heap) *,
414 bool);
415
416 extern void create_rdg_vertices (struct graph *, VEC (gimple, heap) *);
417 extern bool dr_may_alias_p (const struct data_reference *,
418 const struct data_reference *);
419
420 /* Return true when the DDR contains two data references that have the
421 same access functions. */
422
423 static inline bool
424 same_access_functions (const struct data_dependence_relation *ddr)
425 {
426 unsigned i;
427
428 for (i = 0; i < DDR_NUM_SUBSCRIPTS (ddr); i++)
429 if (!eq_evolutions_p (DR_ACCESS_FN (DDR_A (ddr), i),
430 DR_ACCESS_FN (DDR_B (ddr), i)))
431 return false;
432
433 return true;
434 }
435
436 /* Return true when DDR is an anti-dependence relation. */
437
438 static inline bool
439 ddr_is_anti_dependent (ddr_p ddr)
440 {
441 return (DDR_ARE_DEPENDENT (ddr) == NULL_TREE
442 && DR_IS_READ (DDR_A (ddr))
443 && !DR_IS_READ (DDR_B (ddr))
444 && !same_access_functions (ddr));
445 }
446
447 /* Return true when DEPENDENCE_RELATIONS contains an anti-dependence. */
448
449 static inline bool
450 ddrs_have_anti_deps (VEC (ddr_p, heap) *dependence_relations)
451 {
452 unsigned i;
453 ddr_p ddr;
454
455 for (i = 0; VEC_iterate (ddr_p, dependence_relations, i, ddr); i++)
456 if (ddr_is_anti_dependent (ddr))
457 return true;
458
459 return false;
460 }
461
462 /* Return the dependence level for the DDR relation. */
463
464 static inline unsigned
465 ddr_dependence_level (ddr_p ddr)
466 {
467 unsigned vector;
468 unsigned level = 0;
469
470 if (DDR_DIST_VECTS (ddr))
471 level = dependence_level (DDR_DIST_VECT (ddr, 0), DDR_NB_LOOPS (ddr));
472
473 for (vector = 1; vector < DDR_NUM_DIST_VECTS (ddr); vector++)
474 level = MIN (level, dependence_level (DDR_DIST_VECT (ddr, vector),
475 DDR_NB_LOOPS (ddr)));
476 return level;
477 }
478
479 \f
480
481 /* A Reduced Dependence Graph (RDG) vertex representing a statement. */
482 typedef struct rdg_vertex
483 {
484 /* The statement represented by this vertex. */
485 gimple stmt;
486
487 /* True when the statement contains a write to memory. */
488 bool has_mem_write;
489
490 /* True when the statement contains a read from memory. */
491 bool has_mem_reads;
492 } *rdg_vertex_p;
493
494 #define RDGV_STMT(V) ((struct rdg_vertex *) ((V)->data))->stmt
495 #define RDGV_HAS_MEM_WRITE(V) ((struct rdg_vertex *) ((V)->data))->has_mem_write
496 #define RDGV_HAS_MEM_READS(V) ((struct rdg_vertex *) ((V)->data))->has_mem_reads
497 #define RDG_STMT(RDG, I) RDGV_STMT (&(RDG->vertices[I]))
498 #define RDG_MEM_WRITE_STMT(RDG, I) RDGV_HAS_MEM_WRITE (&(RDG->vertices[I]))
499 #define RDG_MEM_READS_STMT(RDG, I) RDGV_HAS_MEM_READS (&(RDG->vertices[I]))
500
501 void dump_rdg_vertex (FILE *, struct graph *, int);
502 void debug_rdg_vertex (struct graph *, int);
503 void dump_rdg_component (FILE *, struct graph *, int, bitmap);
504 void debug_rdg_component (struct graph *, int);
505 void dump_rdg (FILE *, struct graph *);
506 void debug_rdg (struct graph *);
507 int rdg_vertex_for_stmt (struct graph *, gimple);
508
509 /* Data dependence type. */
510
511 enum rdg_dep_type
512 {
513 /* Read After Write (RAW). */
514 flow_dd = 'f',
515
516 /* Write After Read (WAR). */
517 anti_dd = 'a',
518
519 /* Write After Write (WAW). */
520 output_dd = 'o',
521
522 /* Read After Read (RAR). */
523 input_dd = 'i'
524 };
525
526 /* Dependence information attached to an edge of the RDG. */
527
528 typedef struct rdg_edge
529 {
530 /* Type of the dependence. */
531 enum rdg_dep_type type;
532
533 /* Levels of the dependence: the depth of the loops that carry the
534 dependence. */
535 unsigned level;
536
537 /* Dependence relation between data dependences, NULL when one of
538 the vertices is a scalar. */
539 ddr_p relation;
540 } *rdg_edge_p;
541
542 #define RDGE_TYPE(E) ((struct rdg_edge *) ((E)->data))->type
543 #define RDGE_LEVEL(E) ((struct rdg_edge *) ((E)->data))->level
544 #define RDGE_RELATION(E) ((struct rdg_edge *) ((E)->data))->relation
545
546 struct graph *build_rdg (struct loop *);
547 struct graph *build_empty_rdg (int);
548 void free_rdg (struct graph *);
549
550 /* Return the index of the variable VAR in the LOOP_NEST array. */
551
552 static inline int
553 index_in_loop_nest (int var, VEC (loop_p, heap) *loop_nest)
554 {
555 struct loop *loopi;
556 int var_index;
557
558 for (var_index = 0; VEC_iterate (loop_p, loop_nest, var_index, loopi);
559 var_index++)
560 if (loopi->num == var)
561 break;
562
563 return var_index;
564 }
565
566 void stores_from_loop (struct loop *, VEC (gimple, heap) **);
567 void remove_similar_memory_refs (VEC (gimple, heap) **);
568 bool rdg_defs_used_in_other_loops_p (struct graph *, int);
569 bool have_similar_memory_accesses (gimple, gimple);
570
571 /* Determines whether RDG vertices V1 and V2 access to similar memory
572 locations, in which case they have to be in the same partition. */
573
574 static inline bool
575 rdg_has_similar_memory_accesses (struct graph *rdg, int v1, int v2)
576 {
577 return have_similar_memory_accesses (RDG_STMT (rdg, v1),
578 RDG_STMT (rdg, v2));
579 }
580
581 /* In lambda-code.c */
582 bool lambda_transform_legal_p (lambda_trans_matrix, int,
583 VEC (ddr_p, heap) *);
584 void lambda_collect_parameters (VEC (data_reference_p, heap) *,
585 VEC (tree, heap) **);
586 bool lambda_compute_access_matrices (VEC (data_reference_p, heap) *,
587 VEC (tree, heap) *,
588 VEC (loop_p, heap) *,
589 struct obstack *);
590
591 /* In tree-data-ref.c */
592 void split_constant_offset (tree , tree *, tree *);
593
594 /* Strongly connected components of the reduced data dependence graph. */
595
596 typedef struct rdg_component
597 {
598 int num;
599 VEC (int, heap) *vertices;
600 } *rdgc;
601
602 DEF_VEC_P (rdgc);
603 DEF_VEC_ALLOC_P (rdgc, heap);
604
605 DEF_VEC_P (bitmap);
606 DEF_VEC_ALLOC_P (bitmap, heap);
607
608 #endif /* GCC_TREE_DATA_REF_H */