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 | http://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 "php.h"
20 #include "zend_compile.h"
21 #include "zend_cfg.h"
22 #include "zend_func_info.h"
23 #include "zend_worklist.h"
24 #include "zend_optimizer.h"
25 #include "zend_optimizer_internal.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 || opcode == ZEND_JMPZNZ) {
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 int 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 zend_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_EXIT:
301 case ZEND_MATCH_ERROR:
302 if (i + 1 < op_array->last) {
303 BB_START(i + 1);
304 }
305 break;
306 case ZEND_THROW:
307 /* Don't treat THROW as terminator if it's used in expression context,
308 * as we may lose live ranges when eliminating unreachable code. */
309 if (opline->extended_value != ZEND_THROW_IS_EXPR && i + 1 < op_array->last) {
310 BB_START(i + 1);
311 }
312 break;
313 case ZEND_INCLUDE_OR_EVAL:
314 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
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_JMPZNZ:
363 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
364 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
365 if (i + 1 < op_array->last) {
366 BB_START(i + 1);
367 }
368 break;
369 case ZEND_JMPZ:
370 case ZEND_JMPNZ:
371 case ZEND_JMPZ_EX:
372 case ZEND_JMPNZ_EX:
373 case ZEND_JMP_SET:
374 case ZEND_COALESCE:
375 case ZEND_ASSERT_CHECK:
376 case ZEND_JMP_NULL:
377 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
378 BB_START(i + 1);
379 break;
380 case ZEND_CATCH:
381 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
382 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
383 }
384 BB_START(i + 1);
385 break;
386 case ZEND_FE_FETCH_R:
387 case ZEND_FE_FETCH_RW:
388 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
389 BB_START(i + 1);
390 break;
391 case ZEND_FE_RESET_R:
392 case ZEND_FE_RESET_RW:
393 BB_START(OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes);
394 BB_START(i + 1);
395 break;
396 case ZEND_SWITCH_LONG:
397 case ZEND_SWITCH_STRING:
398 case ZEND_MATCH:
399 {
400 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
401 zval *zv;
402 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
403 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv)));
404 } ZEND_HASH_FOREACH_END();
405 BB_START(ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value));
406 BB_START(i + 1);
407 break;
408 }
409 case ZEND_FETCH_R:
410 case ZEND_FETCH_W:
411 case ZEND_FETCH_RW:
412 case ZEND_FETCH_FUNC_ARG:
413 case ZEND_FETCH_IS:
414 case ZEND_FETCH_UNSET:
415 case ZEND_UNSET_VAR:
416 case ZEND_ISSET_ISEMPTY_VAR:
417 if (opline->extended_value & ZEND_FETCH_LOCAL) {
418 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
419 } else if ((opline->extended_value & (ZEND_FETCH_GLOBAL | ZEND_FETCH_GLOBAL_LOCK)) &&
420 !op_array->function_name) {
421 flags |= ZEND_FUNC_INDIRECT_VAR_ACCESS;
422 }
423 break;
424 case ZEND_FUNC_GET_ARGS:
425 flags |= ZEND_FUNC_VARARG;
426 break;
427 case ZEND_EXT_STMT:
428 flags |= ZEND_FUNC_HAS_EXTENDED_STMT;
429 break;
430 case ZEND_EXT_FCALL_BEGIN:
431 case ZEND_EXT_FCALL_END:
432 flags |= ZEND_FUNC_HAS_EXTENDED_FCALL;
433 break;
434 case ZEND_FREE:
435 case ZEND_FE_FREE:
436 if (zend_optimizer_is_loop_var_free(opline)) {
437 BB_START(i);
438 flags |= ZEND_FUNC_FREE_LOOP_VAR;
439 }
440 break;
441 }
442 }
443
444 /* If the entry block has predecessors, we may need to split it */
445 if ((build_flags & ZEND_CFG_NO_ENTRY_PREDECESSORS)
446 && op_array->last > 0 && block_map[0] > 1) {
447 extra_entry_block = 1;
448 }
449
450 if (op_array->last_try_catch) {
451 for (j = 0; j < op_array->last_try_catch; j++) {
452 BB_START(op_array->try_catch_array[j].try_op);
453 if (op_array->try_catch_array[j].catch_op) {
454 BB_START(op_array->try_catch_array[j].catch_op);
455 }
456 if (op_array->try_catch_array[j].finally_op) {
457 BB_START(op_array->try_catch_array[j].finally_op);
458 }
459 if (op_array->try_catch_array[j].finally_end) {
460 BB_START(op_array->try_catch_array[j].finally_end);
461 }
462 }
463 }
464
465 blocks_count += extra_entry_block;
466 cfg->blocks_count = blocks_count;
467
468 /* Build CFG, Step 2: Build Array of Basic Blocks */
469 cfg->blocks = blocks = zend_arena_calloc(arena, sizeof(zend_basic_block), blocks_count);
470
471 blocks_count = -1;
472
473 if (extra_entry_block) {
474 initialize_block(&blocks[0]);
475 blocks[0].start = 0;
476 blocks[0].len = 0;
477 blocks_count++;
478 }
479
480 for (i = 0; i < op_array->last; i++) {
481 if (block_map[i]) {
482 if (blocks_count >= 0) {
483 blocks[blocks_count].len = i - blocks[blocks_count].start;
484 }
485 blocks_count++;
486 initialize_block(&blocks[blocks_count]);
487 blocks[blocks_count].start = i;
488 }
489 block_map[i] = blocks_count;
490 }
491
492 blocks[blocks_count].len = i - blocks[blocks_count].start;
493 blocks_count++;
494
495 /* Build CFG, Step 3: Calculate successors */
496 for (j = 0; j < blocks_count; j++) {
497 zend_basic_block *block = &blocks[j];
498 zend_op *opline;
499 if (block->len == 0) {
500 block->successors_count = 1;
501 block->successors[0] = j + 1;
502 continue;
503 }
504
505 opline = op_array->opcodes + block->start + block->len - 1;
506 switch (opline->opcode) {
507 case ZEND_FAST_RET:
508 case ZEND_RETURN:
509 case ZEND_RETURN_BY_REF:
510 case ZEND_GENERATOR_RETURN:
511 case ZEND_EXIT:
512 case ZEND_THROW:
513 case ZEND_MATCH_ERROR:
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_JMPZNZ:
520 block->successors_count = 2;
521 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
522 block->successors[1] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
523 break;
524 case ZEND_JMPZ:
525 case ZEND_JMPNZ:
526 case ZEND_JMPZ_EX:
527 case ZEND_JMPNZ_EX:
528 case ZEND_JMP_SET:
529 case ZEND_COALESCE:
530 case ZEND_ASSERT_CHECK:
531 case ZEND_JMP_NULL:
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 break;
536 case ZEND_CATCH:
537 if (!(opline->extended_value & ZEND_LAST_CATCH)) {
538 block->successors_count = 2;
539 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
540 block->successors[1] = j + 1;
541 } else {
542 block->successors_count = 1;
543 block->successors[0] = j + 1;
544 }
545 break;
546 case ZEND_FE_FETCH_R:
547 case ZEND_FE_FETCH_RW:
548 block->successors_count = 2;
549 block->successors[0] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
550 block->successors[1] = j + 1;
551 break;
552 case ZEND_FE_RESET_R:
553 case ZEND_FE_RESET_RW:
554 block->successors_count = 2;
555 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op2) - op_array->opcodes];
556 block->successors[1] = j + 1;
557 break;
558 case ZEND_FAST_CALL:
559 block->successors_count = 2;
560 block->successors[0] = block_map[OP_JMP_ADDR(opline, opline->op1) - op_array->opcodes];
561 block->successors[1] = j + 1;
562 break;
563 case ZEND_SWITCH_LONG:
564 case ZEND_SWITCH_STRING:
565 case ZEND_MATCH:
566 {
567 HashTable *jumptable = Z_ARRVAL_P(CRT_CONSTANT(opline->op2));
568 zval *zv;
569 uint32_t s = 0;
570
571 block->successors_count = (opline->opcode == ZEND_MATCH ? 1 : 2) + zend_hash_num_elements(jumptable);
572 block->successors = zend_arena_calloc(arena, block->successors_count, sizeof(int));
573
574 ZEND_HASH_FOREACH_VAL(jumptable, zv) {
575 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, Z_LVAL_P(zv))];
576 } ZEND_HASH_FOREACH_END();
577
578 block->successors[s++] = block_map[ZEND_OFFSET_TO_OPLINE_NUM(op_array, opline, opline->extended_value)];
579 if (opline->opcode != ZEND_MATCH) {
580 block->successors[s++] = j + 1;
581 }
582 break;
583 }
584 default:
585 block->successors_count = 1;
586 block->successors[0] = j + 1;
587 break;
588 }
589 }
590
591 /* Build CFG, Step 4, Mark Reachable Basic Blocks */
592 cfg->flags |= flags;
593 zend_mark_reachable_blocks(op_array, cfg, 0);
594
595 return SUCCESS;
596 }
597 /* }}} */
598
zend_cfg_build_predecessors(zend_arena ** arena,zend_cfg * cfg)599 int zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
600 {
601 int j, s, edges;
602 zend_basic_block *b;
603 zend_basic_block *blocks = cfg->blocks;
604 zend_basic_block *end = blocks + cfg->blocks_count;
605 int *predecessors;
606
607 edges = 0;
608 for (b = blocks; b < end; b++) {
609 b->predecessors_count = 0;
610 }
611 for (b = blocks; b < end; b++) {
612 if (!(b->flags & ZEND_BB_REACHABLE)) {
613 b->successors_count = 0;
614 b->predecessors_count = 0;
615 } else {
616 for (s = 0; s < b->successors_count; s++) {
617 edges++;
618 blocks[b->successors[s]].predecessors_count++;
619 }
620 }
621 }
622
623 cfg->edges_count = edges;
624 cfg->predecessors = predecessors = (int*)zend_arena_calloc(arena, sizeof(int), edges);
625
626 edges = 0;
627 for (b = blocks; b < end; b++) {
628 if (b->flags & ZEND_BB_REACHABLE) {
629 b->predecessor_offset = edges;
630 edges += b->predecessors_count;
631 b->predecessors_count = 0;
632 }
633 }
634
635 for (j = 0; j < cfg->blocks_count; j++) {
636 if (blocks[j].flags & ZEND_BB_REACHABLE) {
637 /* SWITCH_STRING/LONG may have few identical successors */
638 for (s = 0; s < blocks[j].successors_count; s++) {
639 int duplicate = 0;
640 int p;
641
642 for (p = 0; p < s; p++) {
643 if (blocks[j].successors[p] == blocks[j].successors[s]) {
644 duplicate = 1;
645 break;
646 }
647 }
648 if (!duplicate) {
649 zend_basic_block *b = blocks + blocks[j].successors[s];
650
651 predecessors[b->predecessor_offset + b->predecessors_count] = j;
652 b->predecessors_count++;
653 }
654 }
655 }
656 }
657
658 return SUCCESS;
659 }
660 /* }}} */
661
662 /* Computes a postorder numbering of the CFG */
compute_postnum_recursive(int * postnum,int * cur,const zend_cfg * cfg,int block_num)663 static void compute_postnum_recursive(
664 int *postnum, int *cur, const zend_cfg *cfg, int block_num) /* {{{ */
665 {
666 int s;
667 zend_basic_block *block = &cfg->blocks[block_num];
668 if (postnum[block_num] != -1) {
669 return;
670 }
671
672 postnum[block_num] = -2; /* Marker for "currently visiting" */
673 for (s = 0; s < block->successors_count; s++) {
674 compute_postnum_recursive(postnum, cur, cfg, block->successors[s]);
675 }
676 postnum[block_num] = (*cur)++;
677 }
678 /* }}} */
679
680 /* Computes dominator tree using algorithm from "A Simple, Fast Dominance Algorithm" by
681 * Cooper, Harvey and Kennedy. */
zend_cfg_compute_dominators_tree(const zend_op_array * op_array,zend_cfg * cfg)682 int zend_cfg_compute_dominators_tree(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
683 {
684 zend_basic_block *blocks = cfg->blocks;
685 int blocks_count = cfg->blocks_count;
686 int j, k, changed;
687
688 ALLOCA_FLAG(use_heap)
689 int *postnum = do_alloca(sizeof(int) * cfg->blocks_count, use_heap);
690 memset(postnum, -1, sizeof(int) * cfg->blocks_count);
691 j = 0;
692 compute_postnum_recursive(postnum, &j, cfg, 0);
693
694 /* FIXME: move declarations */
695 blocks[0].idom = 0;
696 do {
697 changed = 0;
698 /* Iterating in RPO here would converge faster */
699 for (j = 1; j < blocks_count; j++) {
700 int idom = -1;
701
702 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
703 continue;
704 }
705 for (k = 0; k < blocks[j].predecessors_count; k++) {
706 int pred = cfg->predecessors[blocks[j].predecessor_offset + k];
707
708 if (idom < 0) {
709 if (blocks[pred].idom >= 0)
710 idom = pred;
711 continue;
712 }
713
714 if (blocks[pred].idom >= 0) {
715 while (idom != pred) {
716 while (postnum[pred] < postnum[idom]) pred = blocks[pred].idom;
717 while (postnum[idom] < postnum[pred]) idom = blocks[idom].idom;
718 }
719 }
720 }
721
722 if (idom >= 0 && blocks[j].idom != idom) {
723 blocks[j].idom = idom;
724 changed = 1;
725 }
726 }
727 } while (changed);
728 blocks[0].idom = -1;
729
730 for (j = 1; j < blocks_count; j++) {
731 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
732 continue;
733 }
734 if (blocks[j].idom >= 0) {
735 /* Sort by block number to traverse children in pre-order */
736 if (blocks[blocks[j].idom].children < 0 ||
737 j < blocks[blocks[j].idom].children) {
738 blocks[j].next_child = blocks[blocks[j].idom].children;
739 blocks[blocks[j].idom].children = j;
740 } else {
741 int k = blocks[blocks[j].idom].children;
742 while (blocks[k].next_child >=0 && j > blocks[k].next_child) {
743 k = blocks[k].next_child;
744 }
745 blocks[j].next_child = blocks[k].next_child;
746 blocks[k].next_child = j;
747 }
748 }
749 }
750
751 for (j = 0; j < blocks_count; j++) {
752 int idom = blocks[j].idom, level = 0;
753 if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
754 continue;
755 }
756 while (idom >= 0) {
757 level++;
758 if (blocks[idom].level >= 0) {
759 level += blocks[idom].level;
760 break;
761 } else {
762 idom = blocks[idom].idom;
763 }
764 }
765 blocks[j].level = level;
766 }
767
768 free_alloca(postnum, use_heap);
769 return SUCCESS;
770 }
771 /* }}} */
772
dominates(zend_basic_block * blocks,int a,int b)773 static int dominates(zend_basic_block *blocks, int a, int b) /* {{{ */
774 {
775 while (blocks[b].level > blocks[a].level) {
776 b = blocks[b].idom;
777 }
778 return a == b;
779 }
780 /* }}} */
781
782 typedef struct {
783 int id;
784 int level;
785 } block_info;
compare_block_level(const block_info * a,const block_info * b)786 static int compare_block_level(const block_info *a, const block_info *b) {
787 return b->level - a->level;
788 }
swap_blocks(block_info * a,block_info * b)789 static void swap_blocks(block_info *a, block_info *b) {
790 block_info tmp = *a;
791 *a = *b;
792 *b = tmp;
793 }
794
zend_cfg_identify_loops(const zend_op_array * op_array,zend_cfg * cfg)795 int zend_cfg_identify_loops(const zend_op_array *op_array, zend_cfg *cfg) /* {{{ */
796 {
797 int i, j, k, n;
798 int time;
799 zend_basic_block *blocks = cfg->blocks;
800 int *entry_times, *exit_times;
801 zend_worklist work;
802 int flag = ZEND_FUNC_NO_LOOPS;
803 block_info *sorted_blocks;
804 ALLOCA_FLAG(list_use_heap)
805 ALLOCA_FLAG(tree_use_heap)
806 ALLOCA_FLAG(sorted_blocks_use_heap)
807
808 ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);
809
810 /* We don't materialize the DJ spanning tree explicitly, as we are only interested in ancestor
811 * queries. These are implemented by checking entry/exit times of the DFS search. */
812 entry_times = do_alloca(2 * sizeof(int) * cfg->blocks_count, tree_use_heap);
813 exit_times = entry_times + cfg->blocks_count;
814 memset(entry_times, -1, 2 * sizeof(int) * cfg->blocks_count);
815
816 zend_worklist_push(&work, 0);
817 time = 0;
818 while (zend_worklist_len(&work)) {
819 next:
820 i = zend_worklist_peek(&work);
821 if (entry_times[i] == -1) {
822 entry_times[i] = time++;
823 }
824 /* Visit blocks immediately dominated by i. */
825 for (j = blocks[i].children; j >= 0; j = blocks[j].next_child) {
826 if (zend_worklist_push(&work, j)) {
827 goto next;
828 }
829 }
830 /* Visit join edges. */
831 for (j = 0; j < blocks[i].successors_count; j++) {
832 int succ = blocks[i].successors[j];
833 if (blocks[succ].idom == i) {
834 continue;
835 } else if (zend_worklist_push(&work, succ)) {
836 goto next;
837 }
838 }
839 exit_times[i] = time++;
840 zend_worklist_pop(&work);
841 }
842
843 /* Sort blocks by decreasing level, which is the order in which we want to process them */
844 sorted_blocks = do_alloca(sizeof(block_info) * cfg->blocks_count, sorted_blocks_use_heap);
845 for (i = 0; i < cfg->blocks_count; i++) {
846 sorted_blocks[i].id = i;
847 sorted_blocks[i].level = blocks[i].level;
848 }
849 zend_sort(sorted_blocks, cfg->blocks_count, sizeof(block_info),
850 (compare_func_t) compare_block_level, (swap_func_t) swap_blocks);
851
852 /* Identify loops. See Sreedhar et al, "Identifying Loops Using DJ
853 Graphs". */
854
855 for (n = 0; n < cfg->blocks_count; n++) {
856 i = sorted_blocks[n].id;
857
858 zend_bitset_clear(work.visited, zend_bitset_len(cfg->blocks_count));
859 for (j = 0; j < blocks[i].predecessors_count; j++) {
860 int pred = cfg->predecessors[blocks[i].predecessor_offset + j];
861
862 /* A join edge is one for which the predecessor does not
863 immediately dominate the successor. */
864 if (blocks[i].idom == pred) {
865 continue;
866 }
867
868 /* In a loop back-edge (back-join edge), the successor dominates
869 the predecessor. */
870 if (dominates(blocks, i, pred)) {
871 blocks[i].flags |= ZEND_BB_LOOP_HEADER;
872 flag &= ~ZEND_FUNC_NO_LOOPS;
873 zend_worklist_push(&work, pred);
874 } else {
875 /* Otherwise it's a cross-join edge. See if it's a branch
876 to an ancestor on the DJ spanning tree. */
877 if (entry_times[pred] > entry_times[i] && exit_times[pred] < exit_times[i]) {
878 blocks[i].flags |= ZEND_BB_IRREDUCIBLE_LOOP;
879 flag |= ZEND_FUNC_IRREDUCIBLE;
880 flag &= ~ZEND_FUNC_NO_LOOPS;
881 }
882 }
883 }
884 while (zend_worklist_len(&work)) {
885 j = zend_worklist_pop(&work);
886 while (blocks[j].loop_header >= 0) {
887 j = blocks[j].loop_header;
888 }
889 if (j != i) {
890 if (blocks[j].idom < 0 && j != 0) {
891 /* Ignore blocks that are unreachable or only abnormally reachable. */
892 continue;
893 }
894 blocks[j].loop_header = i;
895 for (k = 0; k < blocks[j].predecessors_count; k++) {
896 zend_worklist_push(&work, cfg->predecessors[blocks[j].predecessor_offset + k]);
897 }
898 }
899 }
900 }
901
902 free_alloca(sorted_blocks, sorted_blocks_use_heap);
903 free_alloca(entry_times, tree_use_heap);
904 ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
905
906 cfg->flags |= flag;
907
908 return SUCCESS;
909 }
910 /* }}} */
911
