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