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 uint8_t 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 case ZEND_BIND_INIT_STATIC_OR_JMP:
373 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
374 BB_START(i + 1);
375 break;
376 case ZEND_CATCH:
377 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
378 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
379 }
380 BB_START(i + 1);
381 break;
382 case ZEND_FE_FETCH_R:
383 case ZEND_FE_FETCH_RW:
384 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
385 BB_START(i + 1);
386 break;
387 case ZEND_FE_RESET_R:
388 case ZEND_FE_RESET_RW:
389 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
390 BB_START(i + 1);
391 break;
392 case ZEND_SWITCH_LONG:
393 case ZEND_SWITCH_STRING:
394 case ZEND_MATCH:
395 {
396 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
397 zval *zv;
398 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
399 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv)));
400 } ZEND_HASH_FOREACH_END();
401 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
402 BB_START(i + 1);
403 break;
404 }
405 case ZEND_FETCH_R:
406 case ZEND_FETCH_W:
407 case ZEND_FETCH_RW:
408 case ZEND_FETCH_FUNC_ARG:
409 case ZEND_FETCH_IS:
410 case ZEND_FETCH_UNSET:
411 case ZEND_UNSET_VAR:
412 case ZEND_ISSET_ISEMPTY_VAR:
413 if (opline->extended_value & ZEND_FETCH_LOCAL) {
414 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
415 } else if ((opline->extended_value & (ZEND_FETCH_GLOBAL | ZEND_FETCH_GLOBAL_LOCK)) &&
416 !op_array->function_name) {
417 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
418 }
419 break;
420 case ZEND_FUNC_GET_ARGS:
421 flags |= ZEND_FUNC_VARARG;
422 break;
423 case ZEND_EXT_STMT:
424 flags |= ZEND_FUNC_HAS_EXTENDED_STMT;
425 break;
426 case ZEND_EXT_FCALL_BEGIN:
427 case ZEND_EXT_FCALL_END:
428 flags |= ZEND_FUNC_HAS_EXTENDED_FCALL;
429 break;
430 case ZEND_FREE:
431 case ZEND_FE_FREE:
432 if (zend_optimizer_is_loop_var_free(opline)
433 && ((opline-1)->opcode != ZEND_MATCH_ERROR
434 || (opline-1)->extended_value != ZEND_THROW_IS_EXPR)) {
435 BB_START(i);
436 flags |= ZEND_FUNC_FREE_LOOP_VAR;
437 }
438 break;
439 }
440 }
441
442 /* If the entry block has predecessors, we may need to split it */
443 if ((build_flags & ZEND_CFG_NO_ENTRY_PREDECESSORS)
444 && op_array->last > 0 && block_map[0] > 1) {
445 extra_entry_block = 1;
446 }
447
448 if (op_array->last_try_catch) {
449 for (j = 0; j < op_array->last_try_catch; j++) {
450 BB_START(op_array->try_catch_array[j].try_op);
451 if (op_array->try_catch_array[j].catch_op) {
452 BB_START(op_array->try_catch_array[j].catch_op);
453 }
454 if (op_array->try_catch_array[j].finally_op) {
455 BB_START(op_array->try_catch_array[j].finally_op);
456 }
457 if (op_array->try_catch_array[j].finally_end) {
458 BB_START(op_array->try_catch_array[j].finally_end);
459 }
460 }
461 }
462
463 blocks_count += extra_entry_block;
464 cfg->blocks_count = blocks_count;
465
466 /* Build CFG, Step 2: Build Array of Basic Blocks */
467 cfg->blocks = blocks = zend_arena_calloc(arena, sizeof(zend_basic_block), blocks_count);
468
469 blocks_count = -1;
470
471 if (extra_entry_block) {
472 initialize_block(&blocks[0]);
473 blocks[0].start = 0;
474 blocks[0].len = 0;
475 blocks_count++;
476 }
477
478 for (i = 0; i < op_array->last; i++) {
479 if (block_map[i]) {
480 if (blocks_count >= 0) {
481 blocks[blocks_count].len = i - blocks[blocks_count].start;
482 }
483 blocks_count++;
484 initialize_block(&blocks[blocks_count]);
485 blocks[blocks_count].start = i;
486 }
487 block_map[i] = blocks_count;
488 }
489
490 blocks[blocks_count].len = i - blocks[blocks_count].start;
491 blocks_count++;
492
493 /* Build CFG, Step 3: Calculate successors */
494 for (j = 0; j < blocks_count; j++) {
495 zend_basic_block *block = &blocks[j];
496 zend_op *opline;
497 if (block->len == 0) {
498 block->successors_count = 1;
499 block->successors[0] = j + 1;
500 continue;
501 }
502
503 opline = op_array->opcodes + block->start + block->len - 1;
504 switch (opline->opcode) {
505 case ZEND_FAST_RET:
506 case ZEND_RETURN:
507 case ZEND_RETURN_BY_REF:
508 case ZEND_GENERATOR_RETURN:
509 case ZEND_EXIT:
510 case ZEND_THROW:
511 case ZEND_MATCH_ERROR:
512 case ZEND_VERIFY_NEVER_TYPE:
513 break;
514 case ZEND_JMP:
515 block->successors_count = 1;
516 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
517 break;
518 case ZEND_JMPZ:
519 case ZEND_JMPNZ:
520 case ZEND_JMPZ_EX:
521 case ZEND_JMPNZ_EX:
522 case ZEND_JMP_SET:
523 case ZEND_COALESCE:
524 case ZEND_ASSERT_CHECK:
525 case ZEND_JMP_NULL:
526 case ZEND_BIND_INIT_STATIC_OR_JMP:
527 block->successors_count = 2;
528 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
529 block->successors[1] = j + 1;
530 break;
531 case ZEND_CATCH:
532 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
533 block->successors_count = 2;
534 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
535 block->successors[1] = j + 1;
536 } else {
537 block->successors_count = 1;
538 block->successors[0] = j + 1;
539 }
540 break;
541 case ZEND_FE_FETCH_R:
542 case ZEND_FE_FETCH_RW:
543 block->successors_count = 2;
544 block->successors[0] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
545 block->successors[1] = j + 1;
546 break;
547 case ZEND_FE_RESET_R:
548 case ZEND_FE_RESET_RW:
549 block->successors_count = 2;
550 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
551 block->successors[1] = j + 1;
552 break;
553 case ZEND_FAST_CALL:
554 block->successors_count = 2;
555 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
556 block->successors[1] = j + 1;
557 break;
558 case ZEND_SWITCH_LONG:
559 case ZEND_SWITCH_STRING:
560 case ZEND_MATCH:
561 {
562 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
563 zval *zv;
564 uint32_t s = 0;
565
566 block->successors_count = (opline->opcode == ZEND_MATCH ? 1 : 2) + zend_hash_num_elements(jumptable);
567 block->successors = zend_arena_calloc(arena, block->successors_count, sizeof(int));
568
569 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
570 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv))];
571 } ZEND_HASH_FOREACH_END();
572
573 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
574 if (opline->opcode != ZEND_MATCH) {
575 block->successors[s++] = j + 1;
576 }
577 break;
578 }
579 default:
580 block->successors_count = 1;
581 block->successors[0] = j + 1;
582 break;
583 }
584 }
585
586 /* Build CFG, Step 4, Mark Reachable Basic Blocks */
587 cfg->flags |= flags;
588 zend_mark_reachable_blocks(op_array, cfg, 0);
589 }
590 /* }}} */
591
zend_cfg_build_predecessors(zend_arena ** arena,zend_cfg * cfg)592 ZEND_API void zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
593 {
594 int j, s, edges;
595 zend_basic_block *b;
596 zend_basic_block *blocks = cfg->blocks;
597 zend_basic_block *end = blocks + cfg->blocks_count;
598 int *predecessors;
599
600 edges = 0;
601 for (b = blocks; b < end; b++) {
602 b->predecessors_count = 0;
603 }
604 for (b = blocks; b < end; b++) {
605 if (!(b->flags & ZEND_BB_REACHABLE)) {
606 b->successors_count = 0;
607 b->predecessors_count = 0;
608 } else {
609 for (s = 0; s < b->successors_count; s++) {
610 edges++;
611 blocks[b->successors[s]].predecessors_count++;
612 }
613 }
614 }
615
616 cfg->edges_count = edges;
617 cfg->predecessors = predecessors = (int*)zend_arena_calloc(arena, sizeof(int), edges);
618
619 edges = 0;
620 for (b = blocks; b < end; b++) {
621 if (b->flags & ZEND_BB_REACHABLE) {
622 b->predecessor_offset = edges;
623 edges += b->predecessors_count;
624 b->predecessors_count = 0;
625 }
626 }
627
628 for (j = 0; j < cfg->blocks_count; j++) {
629 if (blocks[j].flags & ZEND_BB_REACHABLE) {
630 /* SWITCH_STRING/LONG may have few identical successors */
631 for (s = 0; s < blocks[j].successors_count; s++) {
632 int duplicate = 0;
633 int p;
634
635 for (p = 0; p < s; p++) {
636 if (blocks[j].successors[p] == blocks[j].successors[s]) {
637 duplicate = 1;
638 break;
639 }
640 }
641 if (!duplicate) {
642 zend_basic_block *b = blocks + blocks[j].successors[s];
643
644 predecessors[b->predecessor_offset + b->predecessors_count] = j;
645 b->predecessors_count++;
646 }
647 }
648 }
649 }
650 }
651 /* }}} */
652
653 /* Computes a postorder numbering of the CFG */
compute_postnum_recursive(int * postnum,int * cur,const zend_cfg * cfg,int block_num)654 static void compute_postnum_recursive(
655 int *postnum, int *cur, const zend_cfg *cfg, int block_num) /* {{{ */
656 {
657 int s;
658 zend_basic_block *block = &cfg->blocks[block_num];
659 if (postnum[block_num] != -1) {
660 return;
661 }
662
663 postnum[block_num] = -2; /* Marker for "currently visiting" */
664 for (s = 0; s < block->successors_count; s++) {
665 compute_postnum_recursive(postnum, cur, cfg, block->successors[s]);
666 }
667 postnum[block_num] = (*cur)++;
668 }
669 /* }}} */
670
671 /* Computes dominator tree using algorithm from "A Simple, Fast Dominance Algorithm" by
672 * Cooper, Harvey and Kennedy. */
zend_cfg_compute_dominators_tree(const zend_op_array * op_array,zend_cfg * cfg)673 ZEND_API void zend_cfg_compute_dominators_tree(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
674 {
675 zend_basic_block *blocks = cfg->blocks;
676 int blocks_count = cfg->blocks_count;
677 int j, k, changed;
678
679 if (cfg->blocks_count == 1) {
680 blocks[0].level = 0;
681 return;
682 }
683
684 ALLOCA_FLAG(use_heap)
685 int *postnum = do_alloca(sizeof(int) * cfg->blocks_count, use_heap);
686 memset(postnum, -1, sizeof(int) * cfg->blocks_count);
687 j = 0;
688 compute_postnum_recursive(postnum, &j, cfg, 0);
689
690 /* FIXME: move declarations */
691 blocks[0].idom = 0;
692 do {
693 changed = 0;
694 /* Iterating in RPO here would converge faster */
695 for (j = 1; j < blocks_count; j++) {
696 int idom = -1;
697
698 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
699 continue;
700 }
701 for (k = 0; k < blocks[j].predecessors_count; k++) {
702 int pred = cfg->predecessors[blocks[j].predecessor_offset + k];
703
704 if (blocks[pred].idom >= 0) {
705 if (idom < 0) {
706 idom = pred;
707 } else {
708 while (idom != pred) {
709 while (postnum[pred] < postnum[idom]) pred = blocks[pred].idom;
710 while (postnum[idom] < postnum[pred]) idom = blocks[idom].idom;
711 }
712 }
713 }
714 }
715
716 if (idom >= 0 && blocks[j].idom != idom) {
717 blocks[j].idom = idom;
718 changed = 1;
719 }
720 }
721 } while (changed);
722 blocks[0].idom = -1;
723
724 for (j = 1; j < blocks_count; j++) {
725 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
726 continue;
727 }
728 if (blocks[j].idom >= 0) {
729 /* Sort by block number to traverse children in pre-order */
730 if (blocks[blocks[j].idom].children < 0 ||
731 j < blocks[blocks[j].idom].children) {
732 blocks[j].next_child = blocks[blocks[j].idom].children;
733 blocks[blocks[j].idom].children = j;
734 } else {
735 int k = blocks[blocks[j].idom].children;
736 while (blocks[k].next_child >=0 && j > blocks[k].next_child) {
737 k = blocks[k].next_child;
738 }
739 blocks[j].next_child = blocks[k].next_child;
740 blocks[k].next_child = j;
741 }
742 }
743 }
744
745 for (j = 0; j < blocks_count; j++) {
746 int idom = blocks[j].idom, level = 0;
747 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
748 continue;
749 }
750 while (idom >= 0) {
751 level++;
752 if (blocks[idom].level >= 0) {
753 level += blocks[idom].level;
754 break;
755 } else {
756 idom = blocks[idom].idom;
757 }
758 }
759 blocks[j].level = level;
760 }
761
762 free_alloca(postnum, use_heap);
763 }
764 /* }}} */
765
dominates(zend_basic_block * blocks,int a,int b)766 static bool dominates(zend_basic_block *blocks, int a, int b) /* {{{ */
767 {
768 while (blocks[b].level > blocks[a].level) {
769 b = blocks[b].idom;
770 }
771 return a == b;
772 }
773 /* }}} */
774
zend_cfg_identify_loops(const zend_op_array * op_array,zend_cfg * cfg)775 ZEND_API void zend_cfg_identify_loops(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
776 {
777 int i, j, k, n;
778 int time;
779 zend_basic_block *blocks = cfg->blocks;
780 int *entry_times, *exit_times;
781 zend_worklist work;
782 int flag = ZEND_FUNC_NO_LOOPS;
783 int *sorted_blocks;
784 ALLOCA_FLAG(list_use_heap)
785 ALLOCA_FLAG(tree_use_heap)
786
787 if (cfg->blocks_count == 1) {
788 cfg->flags |= flag;
789 return;
790 }
791
792 ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
793
794 /* We don't materialize the DJ spanning tree explicitly, as we are only interested in ancestor
795 * queries. These are implemented by checking entry/exit times of the DFS search. */
796 entry_times = do_alloca(3 * sizeof(int) * cfg->blocks_count, tree_use_heap);
797 exit_times = entry_times + cfg->blocks_count;
798 sorted_blocks = exit_times + cfg->blocks_count;
799 memset(entry_times, -1, 2 * sizeof(int) * cfg->blocks_count);
800
801 zend_worklist_push(&work, 0);
802 time = 0;
803 while (zend_worklist_len(&work)) {
804 next:
805 i = zend_worklist_peek(&work);
806 if (entry_times[i] == -1) {
807 entry_times[i] = time++;
808 }
809 /* Visit blocks immediately dominated by i. */
810 for (j = blocks[i].children; j >= 0; j = blocks[j].next_child) {
811 if (zend_worklist_push(&work, j)) {
812 goto next;
813 }
814 }
815 /* Visit join edges. */
816 for (j = 0; j < blocks[i].successors_count; j++) {
817 int succ = blocks[i].successors[j];
818 if (blocks[succ].idom == i) {
819 continue;
820 } else if (zend_worklist_push(&work, succ)) {
821 goto next;
822 }
823 }
824 exit_times[i] = time++;
825 zend_worklist_pop(&work);
826 }
827
828 /* Sort blocks by level, which is the opposite order in which we want to process them */
829 sorted_blocks[0] = 0;
830 j = 0;
831 n = 1;
832 while (j != n) {
833 i = j;
834 j = n;
835 for (; i < j; i++) {
836 int child;
837 for (child = blocks[sorted_blocks[i]].children; child >= 0; child = blocks[child].next_child) {
838 sorted_blocks[n++] = child;
839 }
840 }
841 }
842
843 /* Identify loops. See Sreedhar et al, "Identifying Loops Using DJ Graphs". */
844 while (n > 0) {
845 i = sorted_blocks[--n];
846
847 if (blocks[i].predecessors_count < 2) {
848 /* loop header has at least two input edges */
849 continue;
850 }
851
852 for (j = 0; j < blocks[i].predecessors_count; j++) {
853 int pred = cfg->predecessors[blocks[i].predecessor_offset + j];
854
855 /* A join edge is one for which the predecessor does not
856 immediately dominate the successor. */
857 if (blocks[i].idom == pred) {
858 continue;
859 }
860
861 /* In a loop back-edge (back-join edge), the successor dominates
862 the predecessor. */
863 if (dominates(blocks, i, pred)) {
864 blocks[i].flags |= ZEND_BB_LOOP_HEADER;
865 flag &= ~ZEND_FUNC_NO_LOOPS;
866 if (!zend_worklist_len(&work)) {
867 zend_bitset_clear(work.visited, zend_bitset_len(cfg->blocks_count));
868 }
869 zend_worklist_push(&work, pred);
870 } else {
871 /* Otherwise it's a cross-join edge. See if it's a branch
872 to an ancestor on the DJ spanning tree. */
873 if (entry_times[pred] > entry_times[i] && exit_times[pred] < exit_times[i]) {
874 blocks[i].flags |= ZEND_BB_IRREDUCIBLE_LOOP;
875 flag |= ZEND_FUNC_IRREDUCIBLE;
876 flag &= ~ZEND_FUNC_NO_LOOPS;
877 }
878 }
879 }
880 while (zend_worklist_len(&work)) {
881 j = zend_worklist_pop(&work);
882 while (blocks[j].loop_header >= 0) {
883 j = blocks[j].loop_header;
884 }
885 if (j != i) {
886 if (blocks[j].idom < 0 && j != 0) {
887 /* Ignore blocks that are unreachable or only abnormally reachable. */
888 continue;
889 }
890 blocks[j].loop_header = i;
891 for (k = 0; k < blocks[j].predecessors_count; k++) {
892 zend_worklist_push(&work, cfg->predecessors[blocks[j].predecessor_offset + k]);
893 }
894 }
895 }
896 }
897
898 free_alloca(entry_times, tree_use_heap);
899 ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
900
901 cfg->flags |= flag;
902 }
903 /* }}} */
904
