1 /*
2 +----------------------------------------------------------------------+
3 | Zend Engine, CFG - Control Flow Graph |
4 +----------------------------------------------------------------------+
5 | Copyright (c) The PHP Group |
6 +----------------------------------------------------------------------+
7 | This source file is subject to version 3.01 of the PHP license, |
8 | that is bundled with this package in the file LICENSE, and is |
9 | available through the world-wide-web at the following url: |
10 | https://www.php.net/license/3_01.txt |
11 | If you did not receive a copy of the PHP license and are unable to |
12 | obtain it through the world-wide-web, please send a note to |
13 | license@php.net so we can mail you a copy immediately. |
14 +----------------------------------------------------------------------+
15 | Authors: Dmitry Stogov <dmitry@php.net> |
16 +----------------------------------------------------------------------+
17 */
18
19 #include "zend_compile.h"
20 #include "zend_cfg.h"
21 #include "zend_func_info.h"
22 #include "zend_worklist.h"
23 #include "zend_optimizer.h"
24 #include "zend_optimizer_internal.h"
25 #include "zend_sort.h"
26
zend_mark_reachable(zend_op * opcodes,zend_cfg * cfg,zend_basic_block * b)27 static void zend_mark_reachable(zend_op *opcodes, zend_cfg *cfg, zend_basic_block *b) /* {{{ */
28 {
29 zend_basic_block *blocks = cfg->blocks;
30
31 zend_worklist work;
32 ALLOCA_FLAG(list_use_heap)
33 ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
34
35 zend_worklist_push(&work, b - cfg->blocks);
36
37 while (zend_worklist_len(&work)) {
38 int i;
39 b = cfg->blocks + zend_worklist_pop(&work);
40
41 b->flags |= ZEND_BB_REACHABLE;
42 if (b->successors_count == 0) {
43 b->flags |= ZEND_BB_EXIT;
44 continue;
45 }
46
47 for (i = 0; i < b->successors_count; i++) {
48 zend_basic_block *succ = blocks + b->successors[i];
49
50 if (b->len != 0) {
51 uint8_t opcode = opcodes[b->start + b->len - 1].opcode;
52 if (opcode == ZEND_MATCH) {
53 succ->flags |= ZEND_BB_TARGET;
54 } else if (opcode == ZEND_SWITCH_LONG || opcode == ZEND_SWITCH_STRING) {
55 if (i == b->successors_count - 1) {
56 succ->flags |= ZEND_BB_FOLLOW | ZEND_BB_TARGET;
57 } else {
58 succ->flags |= ZEND_BB_TARGET;
59 }
60 } else if (b->successors_count == 1) {
61 if (opcode == ZEND_JMP) {
62 succ->flags |= ZEND_BB_TARGET;
63 } else {
64 succ->flags |= ZEND_BB_FOLLOW;
65
66 if ((cfg->flags & ZEND_CFG_STACKLESS)) {
67 if (opcode == ZEND_INCLUDE_OR_EVAL ||
68 opcode == ZEND_GENERATOR_CREATE ||
69 opcode == ZEND_YIELD ||
70 opcode == ZEND_YIELD_FROM ||
71 opcode == ZEND_DO_FCALL ||
72 opcode == ZEND_DO_UCALL ||
73 opcode == ZEND_DO_FCALL_BY_NAME) {
74 succ->flags |= ZEND_BB_ENTRY;
75 }
76 }
77 if ((cfg->flags & ZEND_CFG_RECV_ENTRY)) {
78 if (opcode == ZEND_RECV ||
79 opcode == ZEND_RECV_INIT) {
80 succ->flags |= ZEND_BB_RECV_ENTRY;
81 }
82 }
83 }
84 } else {
85 ZEND_ASSERT(b->successors_count == 2);
86 if (i == 0) {
87 succ->flags |= ZEND_BB_TARGET;
88 } else {
89 succ->flags |= ZEND_BB_FOLLOW;
90 }
91 }
92 } else {
93 succ->flags |= ZEND_BB_FOLLOW;
94 }
95
96 /* Check reachability of successor */
97 if (!(succ->flags & ZEND_BB_REACHABLE)) {
98 zend_worklist_push(&work, succ - cfg->blocks);
99 }
100 }
101 }
102
103 ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
104 }
105 /* }}} */
106
zend_mark_reachable_blocks(const zend_op_array * op_array,zend_cfg * cfg,int start)107 static void zend_mark_reachable_blocks(const zend_op_array *op_array, zend_cfg *cfg, int start) /* {{{ */
108 {
109 zend_basic_block *blocks = cfg->blocks;
110
111 blocks[start].flags = ZEND_BB_START;
112 zend_mark_reachable(op_array->opcodes, cfg, blocks + start);
113
114 if (op_array->last_try_catch) {
115 zend_basic_block *b;
116 int j, changed;
117 uint32_t *block_map = cfg->map;
118
119 do {
120 changed = 0;
121
122 /* Add exception paths */
123 for (j = 0; j < op_array->last_try_catch; j++) {
124
125 /* check for jumps into the middle of try block */
126 b = blocks + block_map[op_array->try_catch_array[j].try_op];
127 if (!(b->flags & ZEND_BB_REACHABLE)) {
128 zend_basic_block *end;
129
130 if (op_array->try_catch_array[j].catch_op) {
131 end = blocks + block_map[op_array->try_catch_array[j].catch_op];
132 while (b != end) {
133 if (b->flags & ZEND_BB_REACHABLE) {
134 op_array->try_catch_array[j].try_op = b->start;
135 break;
136 }
137 b++;
138 }
139 }
140 b = blocks + block_map[op_array->try_catch_array[j].try_op];
141 if (!(b->flags & ZEND_BB_REACHABLE)) {
142 if (op_array->try_catch_array[j].finally_op) {
143 end = blocks + block_map[op_array->try_catch_array[j].finally_op];
144 while (b != end) {
145 if (b->flags & ZEND_BB_REACHABLE) {
146 op_array->try_catch_array[j].try_op = op_array->try_catch_array[j].catch_op;
147 changed = 1;
148 zend_mark_reachable(op_array->opcodes, cfg, blocks + block_map[op_array->try_catch_array[j].try_op]);
149 break;
150 }
151 b++;
152 }
153 }
154 }
155 }
156
157 b = blocks + block_map[op_array->try_catch_array[j].try_op];
158 if (b->flags & ZEND_BB_REACHABLE) {
159 b->flags |= ZEND_BB_TRY;
160 if (op_array->try_catch_array[j].catch_op) {
161 b = blocks + block_map[op_array->try_catch_array[j].catch_op];
162 b->flags |= ZEND_BB_CATCH;
163 if (!(b->flags & ZEND_BB_REACHABLE)) {
164 changed = 1;
165 zend_mark_reachable(op_array->opcodes, cfg, b);
166 }
167 }
168 if (op_array->try_catch_array[j].finally_op) {
169 b = blocks + block_map[op_array->try_catch_array[j].finally_op];
170 b->flags |= ZEND_BB_FINALLY;
171 if (!(b->flags & ZEND_BB_REACHABLE)) {
172 changed = 1;
173 zend_mark_reachable(op_array->opcodes, cfg, b);
174 }
175 }
176 if (op_array->try_catch_array[j].finally_end) {
177 b = blocks + block_map[op_array->try_catch_array[j].finally_end];
178 b->flags |= ZEND_BB_FINALLY_END;
179 if (!(b->flags & ZEND_BB_REACHABLE)) {
180 changed = 1;
181 zend_mark_reachable(op_array->opcodes, cfg, b);
182 }
183 }
184 } else {
185 if (op_array->try_catch_array[j].catch_op) {
186 ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].catch_op]].flags & ZEND_BB_REACHABLE));
187 }
188 if (op_array->try_catch_array[j].finally_op) {
189 ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].finally_op]].flags & ZEND_BB_REACHABLE));
190 }
191 if (op_array->try_catch_array[j].finally_end) {
192 ZEND_ASSERT(!(blocks[block_map[op_array->try_catch_array[j].finally_end]].flags & ZEND_BB_REACHABLE));
193 }
194 }
195 }
196 } while (changed);
197 }
198
199 if (cfg->flags & ZEND_FUNC_FREE_LOOP_VAR) {
200 zend_basic_block *b;
201 int j;
202 uint32_t *block_map = cfg->map;
203
204 /* Mark blocks that are unreachable, but free a loop var created in a reachable block. */
205 for (b = blocks; b < blocks + cfg->blocks_count; b++) {
206 if (b->flags & ZEND_BB_REACHABLE) {
207 continue;
208 }
209
210 for (j = b->start; j < b->start + b->len; j++) {
211 zend_op *opline = &op_array->opcodes[j];
212 if (zend_optimizer_is_loop_var_free(opline)) {
213 zend_op *def_opline = zend_optimizer_get_loop_var_def(op_array, opline);
214 if (def_opline) {
215 uint32_t def_block = block_map[def_opline - op_array->opcodes];
216 if (blocks[def_block].flags & ZEND_BB_REACHABLE) {
217 b->flags |= ZEND_BB_UNREACHABLE_FREE;
218 break;
219 }
220 }
221 }
222 }
223 }
224 }
225 }
226 /* }}} */
227
zend_cfg_remark_reachable_blocks(const zend_op_array * op_array,zend_cfg * cfg)228 void zend_cfg_remark_reachable_blocks(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
229 {
230 zend_basic_block *blocks = cfg->blocks;
231 int i;
232 int start = 0;
233
234 for (i = 0; i < cfg->blocks_count; i++) {
235 if (blocks[i].flags & ZEND_BB_REACHABLE) {
236 start = i;
237 i++;
238 break;
239 }
240 }
241
242 /* clear all flags */
243 for (i = 0; i < cfg->blocks_count; i++) {
244 blocks[i].flags = 0;
245 }
246
247 zend_mark_reachable_blocks(op_array, cfg, start);
248 }
249 /* }}} */
250
initialize_block(zend_basic_block * block)251 static void initialize_block(zend_basic_block *block) {
252 block->flags = 0;
253 block->successors = block->successors_storage;
254 block->successors_count = 0;
255 block->predecessors_count = 0;
256 block->predecessor_offset = -1;
257 block->idom = -1;
258 block->loop_header = -1;
259 block->level = -1;
260 block->children = -1;
261 block->next_child = -1;
262 }
263
264 #define BB_START(i) do { \
265 if (!block_map[i]) { blocks_count++;} \
266 block_map[i]++; \
267 } while (0)
268
zend_build_cfg(zend_arena ** arena,const zend_op_array * op_array,uint32_t build_flags,zend_cfg * cfg)269 ZEND_API void zend_build_cfg(zend_arena **arena, const zend_op_array *op_array, uint32_t build_flags, zend_cfg *cfg) /* {{{ */
270 {
271 uint32_t flags = 0;
272 uint32_t i;
273 int j;
274 uint32_t *block_map;
275 zend_function *fn;
276 int blocks_count = 0;
277 zend_basic_block *blocks;
278 zval *zv;
279 bool extra_entry_block = 0;
280
281 cfg->flags = build_flags & (ZEND_CFG_STACKLESS|ZEND_CFG_RECV_ENTRY);
282
283 cfg->map = block_map = zend_arena_calloc(arena, op_array->last, sizeof(uint32_t));
284
285 /* Build CFG, Step 1: Find basic blocks starts, calculate number of blocks */
286 BB_START(0);
287 for (i = 0; i < op_array->last; i++) {
288 zend_op *opline = op_array->opcodes + i;
289 switch (opline->opcode) {
290 case ZEND_RECV:
291 case ZEND_RECV_INIT:
292 if (build_flags & ZEND_CFG_RECV_ENTRY) {
293 BB_START(i + 1);
294 }
295 break;
296 case ZEND_RETURN:
297 case ZEND_RETURN_BY_REF:
298 case ZEND_GENERATOR_RETURN:
299 case ZEND_VERIFY_NEVER_TYPE:
300 if (i + 1 < op_array->last) {
301 BB_START(i + 1);
302 }
303 break;
304 case ZEND_MATCH_ERROR:
305 case ZEND_THROW:
306 /* Don't treat THROW as terminator if it's used in expression context,
307 * as we may lose live ranges when eliminating unreachable code. */
308 if (opline->extended_value != ZEND_THROW_IS_EXPR && i + 1 < op_array->last) {
309 BB_START(i + 1);
310 }
311 break;
312 case ZEND_INCLUDE_OR_EVAL:
313 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
314 ZEND_FALLTHROUGH;
315 case ZEND_GENERATOR_CREATE:
316 case ZEND_YIELD:
317 case ZEND_YIELD_FROM:
318 if (build_flags & ZEND_CFG_STACKLESS) {
319 BB_START(i + 1);
320 }
321 break;
322 case ZEND_DO_FCALL:
323 case ZEND_DO_UCALL:
324 case ZEND_DO_FCALL_BY_NAME:
325 flags |= ZEND_FUNC_HAS_CALLS;
326 if (build_flags & ZEND_CFG_STACKLESS) {
327 BB_START(i + 1);
328 }
329 break;
330 case ZEND_DO_ICALL:
331 flags |= ZEND_FUNC_HAS_CALLS;
332 break;
333 case ZEND_INIT_FCALL:
334 case ZEND_INIT_NS_FCALL_BY_NAME:
335 zv = CRT_CONSTANT(opline->op2);
336 if (opline->opcode == ZEND_INIT_NS_FCALL_BY_NAME) {
337 /* The third literal is the lowercased unqualified name */
338 zv += 2;
339 }
340 if ((fn = zend_hash_find_ptr(EG(function_table), Z_STR_P(zv))) != NULL) {
341 if (fn->type == ZEND_INTERNAL_FUNCTION) {
342 flags |= zend_optimizer_classify_function(
343 Z_STR_P(zv), opline->extended_value);
344 }
345 }
346 break;
347 case ZEND_FAST_CALL:
348 BB_START(OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes);
349 BB_START(i + 1);
350 break;
351 case ZEND_FAST_RET:
352 if (i + 1 < op_array->last) {
353 BB_START(i + 1);
354 }
355 break;
356 case ZEND_JMP:
357 BB_START(OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes);
358 if (i + 1 < op_array->last) {
359 BB_START(i + 1);
360 }
361 break;
362 case ZEND_JMPZ:
363 case ZEND_JMPNZ:
364 case ZEND_JMPZ_EX:
365 case ZEND_JMPNZ_EX:
366 case ZEND_JMP_SET:
367 case ZEND_COALESCE:
368 case ZEND_ASSERT_CHECK:
369 case ZEND_JMP_NULL:
370 case ZEND_BIND_INIT_STATIC_OR_JMP:
371 case ZEND_JMP_FRAMELESS:
372 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
373 BB_START(i + 1);
374 break;
375 case ZEND_CATCH:
376 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
377 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
378 }
379 BB_START(i + 1);
380 break;
381 case ZEND_FE_FETCH_R:
382 case ZEND_FE_FETCH_RW:
383 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
384 BB_START(i + 1);
385 break;
386 case ZEND_FE_RESET_R:
387 case ZEND_FE_RESET_RW:
388 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
389 BB_START(i + 1);
390 break;
391 case ZEND_SWITCH_LONG:
392 case ZEND_SWITCH_STRING:
393 case ZEND_MATCH:
394 {
395 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
396 zval *zv;
397 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
398 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv)));
399 } ZEND_HASH_FOREACH_END();
400 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
401 BB_START(i + 1);
402 break;
403 }
404 case ZEND_FETCH_R:
405 case ZEND_FETCH_W:
406 case ZEND_FETCH_RW:
407 case ZEND_FETCH_FUNC_ARG:
408 case ZEND_FETCH_IS:
409 case ZEND_FETCH_UNSET:
410 case ZEND_UNSET_VAR:
411 case ZEND_ISSET_ISEMPTY_VAR:
412 if (opline->extended_value & ZEND_FETCH_LOCAL) {
413 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
414 } else if ((opline->extended_value & (ZEND_FETCH_GLOBAL | ZEND_FETCH_GLOBAL_LOCK)) &&
415 !op_array->function_name) {
416 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
417 }
418 break;
419 case ZEND_FUNC_GET_ARGS:
420 flags |= ZEND_FUNC_VARARG;
421 break;
422 case ZEND_EXT_STMT:
423 flags |= ZEND_FUNC_HAS_EXTENDED_STMT;
424 break;
425 case ZEND_EXT_FCALL_BEGIN:
426 case ZEND_EXT_FCALL_END:
427 flags |= ZEND_FUNC_HAS_EXTENDED_FCALL;
428 break;
429 case ZEND_FREE:
430 case ZEND_FE_FREE:
431 if (zend_optimizer_is_loop_var_free(opline)
432 && ((opline-1)->opcode != ZEND_MATCH_ERROR
433 || (opline-1)->extended_value != ZEND_THROW_IS_EXPR)) {
434 BB_START(i);
435 flags |= ZEND_FUNC_FREE_LOOP_VAR;
436 }
437 break;
438 }
439 }
440
441 /* If the entry block has predecessors, we may need to split it */
442 if ((build_flags & ZEND_CFG_NO_ENTRY_PREDECESSORS)
443 && op_array->last > 0 && block_map[0] > 1) {
444 extra_entry_block = 1;
445 }
446
447 if (op_array->last_try_catch) {
448 for (j = 0; j < op_array->last_try_catch; j++) {
449 BB_START(op_array->try_catch_array[j].try_op);
450 if (op_array->try_catch_array[j].catch_op) {
451 BB_START(op_array->try_catch_array[j].catch_op);
452 }
453 if (op_array->try_catch_array[j].finally_op) {
454 BB_START(op_array->try_catch_array[j].finally_op);
455 }
456 if (op_array->try_catch_array[j].finally_end) {
457 BB_START(op_array->try_catch_array[j].finally_end);
458 }
459 }
460 }
461
462 blocks_count += extra_entry_block;
463 cfg->blocks_count = blocks_count;
464
465 /* Build CFG, Step 2: Build Array of Basic Blocks */
466 cfg->blocks = blocks = zend_arena_calloc(arena, sizeof(zend_basic_block), blocks_count);
467
468 blocks_count = -1;
469
470 if (extra_entry_block) {
471 initialize_block(&blocks[0]);
472 blocks[0].start = 0;
473 blocks[0].len = 0;
474 blocks_count++;
475 }
476
477 for (i = 0; i < op_array->last; i++) {
478 if (block_map[i]) {
479 if (blocks_count >= 0) {
480 blocks[blocks_count].len = i - blocks[blocks_count].start;
481 }
482 blocks_count++;
483 initialize_block(&blocks[blocks_count]);
484 blocks[blocks_count].start = i;
485 }
486 block_map[i] = blocks_count;
487 }
488
489 blocks[blocks_count].len = i - blocks[blocks_count].start;
490 blocks_count++;
491
492 /* Build CFG, Step 3: Calculate successors */
493 for (j = 0; j < blocks_count; j++) {
494 zend_basic_block *block = &blocks[j];
495 zend_op *opline;
496 if (block->len == 0) {
497 block->successors_count = 1;
498 block->successors[0] = j + 1;
499 continue;
500 }
501
502 opline = op_array->opcodes + block->start + block->len - 1;
503 switch (opline->opcode) {
504 case ZEND_FAST_RET:
505 case ZEND_RETURN:
506 case ZEND_RETURN_BY_REF:
507 case ZEND_GENERATOR_RETURN:
508 case ZEND_THROW:
509 case ZEND_MATCH_ERROR:
510 case ZEND_VERIFY_NEVER_TYPE:
511 break;
512 case ZEND_JMP:
513 block->successors_count = 1;
514 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
515 break;
516 case ZEND_JMPZ:
517 case ZEND_JMPNZ:
518 case ZEND_JMPZ_EX:
519 case ZEND_JMPNZ_EX:
520 case ZEND_JMP_SET:
521 case ZEND_COALESCE:
522 case ZEND_ASSERT_CHECK:
523 case ZEND_JMP_NULL:
524 case ZEND_BIND_INIT_STATIC_OR_JMP:
525 case ZEND_JMP_FRAMELESS:
526 block->successors_count = 2;
527 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
528 block->successors[1] = j + 1;
529 break;
530 case ZEND_CATCH:
531 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
532 block->successors_count = 2;
533 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
534 block->successors[1] = j + 1;
535 } else {
536 block->successors_count = 1;
537 block->successors[0] = j + 1;
538 }
539 break;
540 case ZEND_FE_FETCH_R:
541 case ZEND_FE_FETCH_RW:
542 block->successors_count = 2;
543 block->successors[0] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
544 block->successors[1] = j + 1;
545 break;
546 case ZEND_FE_RESET_R:
547 case ZEND_FE_RESET_RW:
548 block->successors_count = 2;
549 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
550 block->successors[1] = j + 1;
551 break;
552 case ZEND_FAST_CALL:
553 block->successors_count = 2;
554 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
555 block->successors[1] = j + 1;
556 break;
557 case ZEND_SWITCH_LONG:
558 case ZEND_SWITCH_STRING:
559 case ZEND_MATCH:
560 {
561 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
562 zval *zv;
563 uint32_t s = 0;
564
565 block->successors_count = (opline->opcode == ZEND_MATCH ? 1 : 2) + zend_hash_num_elements(jumptable);
566 block->successors = zend_arena_calloc(arena, block->successors_count, sizeof(int));
567
568 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
569 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv))];
570 } ZEND_HASH_FOREACH_END();
571
572 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
573 if (opline->opcode != ZEND_MATCH) {
574 block->successors[s++] = j + 1;
575 }
576 break;
577 }
578 default:
579 block->successors_count = 1;
580 block->successors[0] = j + 1;
581 break;
582 }
583 }
584
585 /* Build CFG, Step 4, Mark Reachable Basic Blocks */
586 cfg->flags |= flags;
587 zend_mark_reachable_blocks(op_array, cfg, 0);
588 }
589 /* }}} */
590
zend_cfg_build_predecessors(zend_arena ** arena,zend_cfg * cfg)591 ZEND_API void zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
592 {
593 int j, s, edges;
594 zend_basic_block *b;
595 zend_basic_block *blocks = cfg->blocks;
596 zend_basic_block *end = blocks + cfg->blocks_count;
597 int *predecessors;
598
599 edges = 0;
600 for (b = blocks; b < end; b++) {
601 b->predecessors_count = 0;
602 }
603 for (b = blocks; b < end; b++) {
604 if (!(b->flags & ZEND_BB_REACHABLE)) {
605 b->successors_count = 0;
606 b->predecessors_count = 0;
607 } else {
608 for (s = 0; s < b->successors_count; s++) {
609 edges++;
610 blocks[b->successors[s]].predecessors_count++;
611 }
612 }
613 }
614
615 cfg->edges_count = edges;
616 cfg->predecessors = predecessors = (int*)zend_arena_calloc(arena, sizeof(int), edges);
617
618 edges = 0;
619 for (b = blocks; b < end; b++) {
620 if (b->flags & ZEND_BB_REACHABLE) {
621 b->predecessor_offset = edges;
622 edges += b->predecessors_count;
623 b->predecessors_count = 0;
624 }
625 }
626
627 for (j = 0; j < cfg->blocks_count; j++) {
628 if (blocks[j].flags & ZEND_BB_REACHABLE) {
629 /* SWITCH_STRING/LONG may have few identical successors */
630 for (s = 0; s < blocks[j].successors_count; s++) {
631 int duplicate = 0;
632 int p;
633
634 for (p = 0; p < s; p++) {
635 if (blocks[j].successors[p] == blocks[j].successors[s]) {
636 duplicate = 1;
637 break;
638 }
639 }
640 if (!duplicate) {
641 zend_basic_block *b = blocks + blocks[j].successors[s];
642
643 predecessors[b->predecessor_offset + b->predecessors_count] = j;
644 b->predecessors_count++;
645 }
646 }
647 }
648 }
649 }
650 /* }}} */
651
652 /* Computes a postorder numbering of the CFG */
compute_postnum_recursive(int * postnum,int * cur,const zend_cfg * cfg,int block_num)653 static void compute_postnum_recursive(
654 int *postnum, int *cur, const zend_cfg *cfg, int block_num) /* {{{ */
655 {
656 int s;
657 zend_basic_block *block = &cfg->blocks[block_num];
658 if (postnum[block_num] != -1) {
659 return;
660 }
661
662 postnum[block_num] = -2; /* Marker for "currently visiting" */
663 for (s = 0; s < block->successors_count; s++) {
664 compute_postnum_recursive(postnum, cur, cfg, block->successors[s]);
665 }
666 postnum[block_num] = (*cur)++;
667 }
668 /* }}} */
669
670 /* Computes dominator tree using algorithm from "A Simple, Fast Dominance Algorithm" by
671 * Cooper, Harvey and Kennedy. */
zend_cfg_compute_dominators_tree(const zend_op_array * op_array,zend_cfg * cfg)672 ZEND_API void zend_cfg_compute_dominators_tree(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
673 {
674 zend_basic_block *blocks = cfg->blocks;
675 int blocks_count = cfg->blocks_count;
676 int j, k, changed;
677
678 if (cfg->blocks_count == 1) {
679 blocks[0].level = 0;
680 return;
681 }
682
683 ALLOCA_FLAG(use_heap)
684 int *postnum = do_alloca(sizeof(int) * cfg->blocks_count, use_heap);
685 memset(postnum, -1, sizeof(int) * cfg->blocks_count);
686 j = 0;
687 compute_postnum_recursive(postnum, &j, cfg, 0);
688
689 /* FIXME: move declarations */
690 blocks[0].idom = 0;
691 do {
692 changed = 0;
693 /* Iterating in RPO here would converge faster */
694 for (j = 1; j < blocks_count; j++) {
695 int idom = -1;
696
697 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
698 continue;
699 }
700 for (k = 0; k < blocks[j].predecessors_count; k++) {
701 int pred = cfg->predecessors[blocks[j].predecessor_offset + k];
702
703 if (blocks[pred].idom >= 0) {
704 if (idom < 0) {
705 idom = pred;
706 } else {
707 while (idom != pred) {
708 while (postnum[pred] < postnum[idom]) pred = blocks[pred].idom;
709 while (postnum[idom] < postnum[pred]) idom = blocks[idom].idom;
710 }
711 }
712 }
713 }
714
715 if (idom >= 0 && blocks[j].idom != idom) {
716 blocks[j].idom = idom;
717 changed = 1;
718 }
719 }
720 } while (changed);
721 blocks[0].idom = -1;
722
723 for (j = 1; j < blocks_count; j++) {
724 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
725 continue;
726 }
727 if (blocks[j].idom >= 0) {
728 /* Sort by block number to traverse children in pre-order */
729 if (blocks[blocks[j].idom].children < 0 ||
730 j < blocks[blocks[j].idom].children) {
731 blocks[j].next_child = blocks[blocks[j].idom].children;
732 blocks[blocks[j].idom].children = j;
733 } else {
734 int k = blocks[blocks[j].idom].children;
735 while (blocks[k].next_child >=0 && j > blocks[k].next_child) {
736 k = blocks[k].next_child;
737 }
738 blocks[j].next_child = blocks[k].next_child;
739 blocks[k].next_child = j;
740 }
741 }
742 }
743
744 for (j = 0; j < blocks_count; j++) {
745 int idom = blocks[j].idom, level = 0;
746 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
747 continue;
748 }
749 while (idom >= 0) {
750 level++;
751 if (blocks[idom].level >= 0) {
752 level += blocks[idom].level;
753 break;
754 } else {
755 idom = blocks[idom].idom;
756 }
757 }
758 blocks[j].level = level;
759 }
760
761 free_alloca(postnum, use_heap);
762 }
763 /* }}} */
764
dominates(zend_basic_block * blocks,int a,int b)765 static bool dominates(zend_basic_block *blocks, int a, int b) /* {{{ */
766 {
767 while (blocks[b].level > blocks[a].level) {
768 b = blocks[b].idom;
769 }
770 return a == b;
771 }
772 /* }}} */
773
zend_cfg_identify_loops(const zend_op_array * op_array,zend_cfg * cfg)774 ZEND_API void zend_cfg_identify_loops(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
775 {
776 int i, j, k, n;
777 int time;
778 zend_basic_block *blocks = cfg->blocks;
779 int *entry_times, *exit_times;
780 zend_worklist work;
781 int flag = ZEND_FUNC_NO_LOOPS;
782 int *sorted_blocks;
783 ALLOCA_FLAG(list_use_heap)
784 ALLOCA_FLAG(tree_use_heap)
785
786 if (cfg->blocks_count == 1) {
787 cfg->flags |= flag;
788 return;
789 }
790
791 ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
792
793 /* We don't materialize the DJ spanning tree explicitly, as we are only interested in ancestor
794 * queries. These are implemented by checking entry/exit times of the DFS search. */
795 entry_times = do_alloca(3 * sizeof(int) * cfg->blocks_count, tree_use_heap);
796 exit_times = entry_times + cfg->blocks_count;
797 sorted_blocks = exit_times + cfg->blocks_count;
798 memset(entry_times, -1, 2 * sizeof(int) * cfg->blocks_count);
799
800 zend_worklist_push(&work, 0);
801 time = 0;
802 while (zend_worklist_len(&work)) {
803 next:
804 i = zend_worklist_peek(&work);
805 if (entry_times[i] == -1) {
806 entry_times[i] = time++;
807 }
808 /* Visit blocks immediately dominated by i. */
809 for (j = blocks[i].children; j >= 0; j = blocks[j].next_child) {
810 if (zend_worklist_push(&work, j)) {
811 goto next;
812 }
813 }
814 /* Visit join edges. */
815 for (j = 0; j < blocks[i].successors_count; j++) {
816 int succ = blocks[i].successors[j];
817 if (blocks[succ].idom == i) {
818 continue;
819 } else if (zend_worklist_push(&work, succ)) {
820 goto next;
821 }
822 }
823 exit_times[i] = time++;
824 zend_worklist_pop(&work);
825 }
826
827 /* Sort blocks by level, which is the opposite order in which we want to process them */
828 sorted_blocks[0] = 0;
829 j = 0;
830 n = 1;
831 while (j != n) {
832 i = j;
833 j = n;
834 for (; i < j; i++) {
835 int child;
836 for (child = blocks[sorted_blocks[i]].children; child >= 0; child = blocks[child].next_child) {
837 sorted_blocks[n++] = child;
838 }
839 }
840 }
841
842 /* Identify loops. See Sreedhar et al, "Identifying Loops Using DJ Graphs". */
843 while (n > 0) {
844 i = sorted_blocks[--n];
845
846 if (blocks[i].predecessors_count < 2) {
847 /* loop header has at least two input edges */
848 continue;
849 }
850
851 for (j = 0; j < blocks[i].predecessors_count; j++) {
852 int pred = cfg->predecessors[blocks[i].predecessor_offset + j];
853
854 /* A join edge is one for which the predecessor does not
855 immediately dominate the successor. */
856 if (blocks[i].idom == pred) {
857 continue;
858 }
859
860 /* In a loop back-edge (back-join edge), the successor dominates
861 the predecessor. */
862 if (dominates(blocks, i, pred)) {
863 blocks[i].flags |= ZEND_BB_LOOP_HEADER;
864 flag &= ~ZEND_FUNC_NO_LOOPS;
865 if (!zend_worklist_len(&work)) {
866 zend_bitset_clear(work.visited, zend_bitset_len(cfg->blocks_count));
867 }
868 zend_worklist_push(&work, pred);
869 } else {
870 /* Otherwise it's a cross-join edge. See if it's a branch
871 to an ancestor on the DJ spanning tree. */
872 if (entry_times[pred] > entry_times[i] && exit_times[pred] < exit_times[i]) {
873 blocks[i].flags |= ZEND_BB_IRREDUCIBLE_LOOP;
874 flag |= ZEND_FUNC_IRREDUCIBLE;
875 flag &= ~ZEND_FUNC_NO_LOOPS;
876 }
877 }
878 }
879 while (zend_worklist_len(&work)) {
880 j = zend_worklist_pop(&work);
881 while (blocks[j].loop_header >= 0) {
882 j = blocks[j].loop_header;
883 }
884 if (j != i) {
885 if (blocks[j].idom < 0 && j != 0) {
886 /* Ignore blocks that are unreachable or only abnormally reachable. */
887 continue;
888 }
889 blocks[j].loop_header = i;
890 for (k = 0; k < blocks[j].predecessors_count; k++) {
891 zend_worklist_push(&work, cfg->predecessors[blocks[j].predecessor_offset + k]);
892 }
893 }
894 }
895 }
896
897 free_alloca(entry_times, tree_use_heap);
898 ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
899
900 cfg->flags |= flag;
901 }
902 /* }}} */
903
