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 case ZEND_JMP_FRAMELESS:
374 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
375 BB_START(i + 1);
376 break;
377 case ZEND_CATCH:
378 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
379 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
380 }
381 BB_START(i + 1);
382 break;
383 case ZEND_FE_FETCH_R:
384 case ZEND_FE_FETCH_RW:
385 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
386 BB_START(i + 1);
387 break;
388 case ZEND_FE_RESET_R:
389 case ZEND_FE_RESET_RW:
390 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
391 BB_START(i + 1);
392 break;
393 case ZEND_SWITCH_LONG:
394 case ZEND_SWITCH_STRING:
395 case ZEND_MATCH:
396 {
397 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
398 zval *zv;
399 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
400 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv)));
401 } ZEND_HASH_FOREACH_END();
402 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
403 BB_START(i + 1);
404 break;
405 }
406 case ZEND_FETCH_R:
407 case ZEND_FETCH_W:
408 case ZEND_FETCH_RW:
409 case ZEND_FETCH_FUNC_ARG:
410 case ZEND_FETCH_IS:
411 case ZEND_FETCH_UNSET:
412 case ZEND_UNSET_VAR:
413 case ZEND_ISSET_ISEMPTY_VAR:
414 if (opline->extended_value & ZEND_FETCH_LOCAL) {
415 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
416 } else if ((opline->extended_value & (ZEND_FETCH_GLOBAL | ZEND_FETCH_GLOBAL_LOCK)) &&
417 !op_array->function_name) {
418 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
419 }
420 break;
421 case ZEND_FUNC_GET_ARGS:
422 flags |= ZEND_FUNC_VARARG;
423 break;
424 case ZEND_EXT_STMT:
425 flags |= ZEND_FUNC_HAS_EXTENDED_STMT;
426 break;
427 case ZEND_EXT_FCALL_BEGIN:
428 case ZEND_EXT_FCALL_END:
429 flags |= ZEND_FUNC_HAS_EXTENDED_FCALL;
430 break;
431 case ZEND_FREE:
432 case ZEND_FE_FREE:
433 if (zend_optimizer_is_loop_var_free(opline)
434 && ((opline-1)->opcode != ZEND_MATCH_ERROR
435 || (opline-1)->extended_value != ZEND_THROW_IS_EXPR)) {
436 BB_START(i);
437 flags |= ZEND_FUNC_FREE_LOOP_VAR;
438 }
439 break;
440 }
441 }
442
443 /* If the entry block has predecessors, we may need to split it */
444 if ((build_flags & ZEND_CFG_NO_ENTRY_PREDECESSORS)
445 && op_array->last > 0 && block_map[0] > 1) {
446 extra_entry_block = 1;
447 }
448
449 if (op_array->last_try_catch) {
450 for (j = 0; j < op_array->last_try_catch; j++) {
451 BB_START(op_array->try_catch_array[j].try_op);
452 if (op_array->try_catch_array[j].catch_op) {
453 BB_START(op_array->try_catch_array[j].catch_op);
454 }
455 if (op_array->try_catch_array[j].finally_op) {
456 BB_START(op_array->try_catch_array[j].finally_op);
457 }
458 if (op_array->try_catch_array[j].finally_end) {
459 BB_START(op_array->try_catch_array[j].finally_end);
460 }
461 }
462 }
463
464 blocks_count += extra_entry_block;
465 cfg->blocks_count = blocks_count;
466
467 /* Build CFG, Step 2: Build Array of Basic Blocks */
468 cfg->blocks = blocks = zend_arena_calloc(arena, sizeof(zend_basic_block), blocks_count);
469
470 blocks_count = -1;
471
472 if (extra_entry_block) {
473 initialize_block(&blocks[0]);
474 blocks[0].start = 0;
475 blocks[0].len = 0;
476 blocks_count++;
477 }
478
479 for (i = 0; i < op_array->last; i++) {
480 if (block_map[i]) {
481 if (blocks_count >= 0) {
482 blocks[blocks_count].len = i - blocks[blocks_count].start;
483 }
484 blocks_count++;
485 initialize_block(&blocks[blocks_count]);
486 blocks[blocks_count].start = i;
487 }
488 block_map[i] = blocks_count;
489 }
490
491 blocks[blocks_count].len = i - blocks[blocks_count].start;
492 blocks_count++;
493
494 /* Build CFG, Step 3: Calculate successors */
495 for (j = 0; j < blocks_count; j++) {
496 zend_basic_block *block = &blocks[j];
497 zend_op *opline;
498 if (block->len == 0) {
499 block->successors_count = 1;
500 block->successors[0] = j + 1;
501 continue;
502 }
503
504 opline = op_array->opcodes + block->start + block->len - 1;
505 switch (opline->opcode) {
506 case ZEND_FAST_RET:
507 case ZEND_RETURN:
508 case ZEND_RETURN_BY_REF:
509 case ZEND_GENERATOR_RETURN:
510 case ZEND_EXIT:
511 case ZEND_THROW:
512 case ZEND_MATCH_ERROR:
513 case ZEND_VERIFY_NEVER_TYPE:
514 break;
515 case ZEND_JMP:
516 block->successors_count = 1;
517 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
518 break;
519 case ZEND_JMPZ:
520 case ZEND_JMPNZ:
521 case ZEND_JMPZ_EX:
522 case ZEND_JMPNZ_EX:
523 case ZEND_JMP_SET:
524 case ZEND_COALESCE:
525 case ZEND_ASSERT_CHECK:
526 case ZEND_JMP_NULL:
527 case ZEND_BIND_INIT_STATIC_OR_JMP:
528 case ZEND_JMP_FRAMELESS:
529 block->successors_count = 2;
530 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
531 block->successors[1] = j + 1;
532 break;
533 case ZEND_CATCH:
534 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
535 block->successors_count = 2;
536 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
537 block->successors[1] = j + 1;
538 } else {
539 block->successors_count = 1;
540 block->successors[0] = j + 1;
541 }
542 break;
543 case ZEND_FE_FETCH_R:
544 case ZEND_FE_FETCH_RW:
545 block->successors_count = 2;
546 block->successors[0] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
547 block->successors[1] = j + 1;
548 break;
549 case ZEND_FE_RESET_R:
550 case ZEND_FE_RESET_RW:
551 block->successors_count = 2;
552 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
553 block->successors[1] = j + 1;
554 break;
555 case ZEND_FAST_CALL:
556 block->successors_count = 2;
557 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
558 block->successors[1] = j + 1;
559 break;
560 case ZEND_SWITCH_LONG:
561 case ZEND_SWITCH_STRING:
562 case ZEND_MATCH:
563 {
564 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
565 zval *zv;
566 uint32_t s = 0;
567
568 block->successors_count = (opline->opcode == ZEND_MATCH ? 1 : 2) + zend_hash_num_elements(jumptable);
569 block->successors = zend_arena_calloc(arena, block->successors_count, sizeof(int));
570
571 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
572 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv))];
573 } ZEND_HASH_FOREACH_END();
574
575 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
576 if (opline->opcode != ZEND_MATCH) {
577 block->successors[s++] = j + 1;
578 }
579 break;
580 }
581 default:
582 block->successors_count = 1;
583 block->successors[0] = j + 1;
584 break;
585 }
586 }
587
588 /* Build CFG, Step 4, Mark Reachable Basic Blocks */
589 cfg->flags |= flags;
590 zend_mark_reachable_blocks(op_array, cfg, 0);
591 }
592 /* }}} */
593
zend_cfg_build_predecessors(zend_arena ** arena,zend_cfg * cfg)594 ZEND_API void zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
595 {
596 int j, s, edges;
597 zend_basic_block *b;
598 zend_basic_block *blocks = cfg->blocks;
599 zend_basic_block *end = blocks + cfg->blocks_count;
600 int *predecessors;
601
602 edges = 0;
603 for (b = blocks; b < end; b++) {
604 b->predecessors_count = 0;
605 }
606 for (b = blocks; b < end; b++) {
607 if (!(b->flags & ZEND_BB_REACHABLE)) {
608 b->successors_count = 0;
609 b->predecessors_count = 0;
610 } else {
611 for (s = 0; s < b->successors_count; s++) {
612 edges++;
613 blocks[b->successors[s]].predecessors_count++;
614 }
615 }
616 }
617
618 cfg->edges_count = edges;
619 cfg->predecessors = predecessors = (int*)zend_arena_calloc(arena, sizeof(int), edges);
620
621 edges = 0;
622 for (b = blocks; b < end; b++) {
623 if (b->flags & ZEND_BB_REACHABLE) {
624 b->predecessor_offset = edges;
625 edges += b->predecessors_count;
626 b->predecessors_count = 0;
627 }
628 }
629
630 for (j = 0; j < cfg->blocks_count; j++) {
631 if (blocks[j].flags & ZEND_BB_REACHABLE) {
632 /* SWITCH_STRING/LONG may have few identical successors */
633 for (s = 0; s < blocks[j].successors_count; s++) {
634 int duplicate = 0;
635 int p;
636
637 for (p = 0; p < s; p++) {
638 if (blocks[j].successors[p] == blocks[j].successors[s]) {
639 duplicate = 1;
640 break;
641 }
642 }
643 if (!duplicate) {
644 zend_basic_block *b = blocks + blocks[j].successors[s];
645
646 predecessors[b->predecessor_offset + b->predecessors_count] = j;
647 b->predecessors_count++;
648 }
649 }
650 }
651 }
652 }
653 /* }}} */
654
655 /* Computes a postorder numbering of the CFG */
compute_postnum_recursive(int * postnum,int * cur,const zend_cfg * cfg,int block_num)656 static void compute_postnum_recursive(
657 int *postnum, int *cur, const zend_cfg *cfg, int block_num) /* {{{ */
658 {
659 int s;
660 zend_basic_block *block = &cfg->blocks[block_num];
661 if (postnum[block_num] != -1) {
662 return;
663 }
664
665 postnum[block_num] = -2; /* Marker for "currently visiting" */
666 for (s = 0; s < block->successors_count; s++) {
667 compute_postnum_recursive(postnum, cur, cfg, block->successors[s]);
668 }
669 postnum[block_num] = (*cur)++;
670 }
671 /* }}} */
672
673 /* Computes dominator tree using algorithm from "A Simple, Fast Dominance Algorithm" by
674 * Cooper, Harvey and Kennedy. */
zend_cfg_compute_dominators_tree(const zend_op_array * op_array,zend_cfg * cfg)675 ZEND_API void zend_cfg_compute_dominators_tree(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
676 {
677 zend_basic_block *blocks = cfg->blocks;
678 int blocks_count = cfg->blocks_count;
679 int j, k, changed;
680
681 if (cfg->blocks_count == 1) {
682 blocks[0].level = 0;
683 return;
684 }
685
686 ALLOCA_FLAG(use_heap)
687 int *postnum = do_alloca(sizeof(int) * cfg->blocks_count, use_heap);
688 memset(postnum, -1, sizeof(int) * cfg->blocks_count);
689 j = 0;
690 compute_postnum_recursive(postnum, &j, cfg, 0);
691
692 /* FIXME: move declarations */
693 blocks[0].idom = 0;
694 do {
695 changed = 0;
696 /* Iterating in RPO here would converge faster */
697 for (j = 1; j < blocks_count; j++) {
698 int idom = -1;
699
700 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
701 continue;
702 }
703 for (k = 0; k < blocks[j].predecessors_count; k++) {
704 int pred = cfg->predecessors[blocks[j].predecessor_offset + k];
705
706 if (blocks[pred].idom >= 0) {
707 if (idom < 0) {
708 idom = pred;
709 } else {
710 while (idom != pred) {
711 while (postnum[pred] < postnum[idom]) pred = blocks[pred].idom;
712 while (postnum[idom] < postnum[pred]) idom = blocks[idom].idom;
713 }
714 }
715 }
716 }
717
718 if (idom >= 0 && blocks[j].idom != idom) {
719 blocks[j].idom = idom;
720 changed = 1;
721 }
722 }
723 } while (changed);
724 blocks[0].idom = -1;
725
726 for (j = 1; j < blocks_count; j++) {
727 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
728 continue;
729 }
730 if (blocks[j].idom >= 0) {
731 /* Sort by block number to traverse children in pre-order */
732 if (blocks[blocks[j].idom].children < 0 ||
733 j < blocks[blocks[j].idom].children) {
734 blocks[j].next_child = blocks[blocks[j].idom].children;
735 blocks[blocks[j].idom].children = j;
736 } else {
737 int k = blocks[blocks[j].idom].children;
738 while (blocks[k].next_child >=0 && j > blocks[k].next_child) {
739 k = blocks[k].next_child;
740 }
741 blocks[j].next_child = blocks[k].next_child;
742 blocks[k].next_child = j;
743 }
744 }
745 }
746
747 for (j = 0; j < blocks_count; j++) {
748 int idom = blocks[j].idom, level = 0;
749 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
750 continue;
751 }
752 while (idom >= 0) {
753 level++;
754 if (blocks[idom].level >= 0) {
755 level += blocks[idom].level;
756 break;
757 } else {
758 idom = blocks[idom].idom;
759 }
760 }
761 blocks[j].level = level;
762 }
763
764 free_alloca(postnum, use_heap);
765 }
766 /* }}} */
767
dominates(zend_basic_block * blocks,int a,int b)768 static bool dominates(zend_basic_block *blocks, int a, int b) /* {{{ */
769 {
770 while (blocks[b].level > blocks[a].level) {
771 b = blocks[b].idom;
772 }
773 return a == b;
774 }
775 /* }}} */
776
zend_cfg_identify_loops(const zend_op_array * op_array,zend_cfg * cfg)777 ZEND_API void zend_cfg_identify_loops(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
778 {
779 int i, j, k, n;
780 int time;
781 zend_basic_block *blocks = cfg->blocks;
782 int *entry_times, *exit_times;
783 zend_worklist work;
784 int flag = ZEND_FUNC_NO_LOOPS;
785 int *sorted_blocks;
786 ALLOCA_FLAG(list_use_heap)
787 ALLOCA_FLAG(tree_use_heap)
788
789 if (cfg->blocks_count == 1) {
790 cfg->flags |= flag;
791 return;
792 }
793
794 ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
795
796 /* We don't materialize the DJ spanning tree explicitly, as we are only interested in ancestor
797 * queries. These are implemented by checking entry/exit times of the DFS search. */
798 entry_times = do_alloca(3 * sizeof(int) * cfg->blocks_count, tree_use_heap);
799 exit_times = entry_times + cfg->blocks_count;
800 sorted_blocks = exit_times + cfg->blocks_count;
801 memset(entry_times, -1, 2 * sizeof(int) * cfg->blocks_count);
802
803 zend_worklist_push(&work, 0);
804 time = 0;
805 while (zend_worklist_len(&work)) {
806 next:
807 i = zend_worklist_peek(&work);
808 if (entry_times[i] == -1) {
809 entry_times[i] = time++;
810 }
811 /* Visit blocks immediately dominated by i. */
812 for (j = blocks[i].children; j >= 0; j = blocks[j].next_child) {
813 if (zend_worklist_push(&work, j)) {
814 goto next;
815 }
816 }
817 /* Visit join edges. */
818 for (j = 0; j < blocks[i].successors_count; j++) {
819 int succ = blocks[i].successors[j];
820 if (blocks[succ].idom == i) {
821 continue;
822 } else if (zend_worklist_push(&work, succ)) {
823 goto next;
824 }
825 }
826 exit_times[i] = time++;
827 zend_worklist_pop(&work);
828 }
829
830 /* Sort blocks by level, which is the opposite order in which we want to process them */
831 sorted_blocks[0] = 0;
832 j = 0;
833 n = 1;
834 while (j != n) {
835 i = j;
836 j = n;
837 for (; i < j; i++) {
838 int child;
839 for (child = blocks[sorted_blocks[i]].children; child >= 0; child = blocks[child].next_child) {
840 sorted_blocks[n++] = child;
841 }
842 }
843 }
844
845 /* Identify loops. See Sreedhar et al, "Identifying Loops Using DJ Graphs". */
846 while (n > 0) {
847 i = sorted_blocks[--n];
848
849 if (blocks[i].predecessors_count < 2) {
850 /* loop header has at least two input edges */
851 continue;
852 }
853
854 for (j = 0; j < blocks[i].predecessors_count; j++) {
855 int pred = cfg->predecessors[blocks[i].predecessor_offset + j];
856
857 /* A join edge is one for which the predecessor does not
858 immediately dominate the successor. */
859 if (blocks[i].idom == pred) {
860 continue;
861 }
862
863 /* In a loop back-edge (back-join edge), the successor dominates
864 the predecessor. */
865 if (dominates(blocks, i, pred)) {
866 blocks[i].flags |= ZEND_BB_LOOP_HEADER;
867 flag &= ~ZEND_FUNC_NO_LOOPS;
868 if (!zend_worklist_len(&work)) {
869 zend_bitset_clear(work.visited, zend_bitset_len(cfg->blocks_count));
870 }
871 zend_worklist_push(&work, pred);
872 } else {
873 /* Otherwise it's a cross-join edge. See if it's a branch
874 to an ancestor on the DJ spanning tree. */
875 if (entry_times[pred] > entry_times[i] && exit_times[pred] < exit_times[i]) {
876 blocks[i].flags |= ZEND_BB_IRREDUCIBLE_LOOP;
877 flag |= ZEND_FUNC_IRREDUCIBLE;
878 flag &= ~ZEND_FUNC_NO_LOOPS;
879 }
880 }
881 }
882 while (zend_worklist_len(&work)) {
883 j = zend_worklist_pop(&work);
884 while (blocks[j].loop_header >= 0) {
885 j = blocks[j].loop_header;
886 }
887 if (j != i) {
888 if (blocks[j].idom < 0 && j != 0) {
889 /* Ignore blocks that are unreachable or only abnormally reachable. */
890 continue;
891 }
892 blocks[j].loop_header = i;
893 for (k = 0; k < blocks[j].predecessors_count; k++) {
894 zend_worklist_push(&work, cfg->predecessors[blocks[j].predecessor_offset + k]);
895 }
896 }
897 }
898 }
899
900 free_alloca(entry_times, tree_use_heap);
901 ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
902
903 cfg->flags |= flag;
904 }
905 /* }}} */
906