1 /*
2 +----------------------------------------------------------------------+
3 | Zend Engine, Removing unused variables |
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: Nikita Popov <nikic@php.net> |
16 +----------------------------------------------------------------------+
17 */
18
19 #include "Optimizer/zend_optimizer_internal.h"
20 #include "zend_bitset.h"
21 #include "zend_observer.h"
22
23 /* This pass removes all CVs and temporaries that are completely unused. It does *not* merge any CVs or TMPs.
24 * This pass does not operate on SSA form anymore. */
zend_optimizer_compact_vars(zend_op_array * op_array)25 void zend_optimizer_compact_vars(zend_op_array *op_array) {
26 int i;
27
28 ALLOCA_FLAG(use_heap1);
29 ALLOCA_FLAG(use_heap2);
30 uint32_t used_vars_len = zend_bitset_len(op_array->last_var + op_array->T);
31 zend_bitset used_vars = ZEND_BITSET_ALLOCA(used_vars_len, use_heap1);
32 uint32_t *vars_map = do_alloca((op_array->last_var + op_array->T) * sizeof(uint32_t), use_heap2);
33 uint32_t num_cvs, num_tmps;
34
35 /* Determine which CVs are used */
36 zend_bitset_clear(used_vars, used_vars_len);
37 for (i = 0; i < op_array->last; i++) {
38 zend_op *opline = &op_array->opcodes[i];
39 if (opline->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
40 zend_bitset_incl(used_vars, VAR_NUM(opline->op1.var));
41 }
42 if (opline->op2_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
43 zend_bitset_incl(used_vars, VAR_NUM(opline->op2.var));
44 }
45 if (opline->result_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
46 zend_bitset_incl(used_vars, VAR_NUM(opline->result.var));
47 if (opline->opcode == ZEND_ROPE_INIT) {
48 uint32_t num = ((opline->extended_value * sizeof(zend_string*)) + (sizeof(zval) - 1)) / sizeof(zval);
49 while (num > 1) {
50 num--;
51 zend_bitset_incl(used_vars, VAR_NUM(opline->result.var) + num);
52 }
53 }
54 }
55 }
56
57 num_cvs = 0;
58 for (i = 0; i < op_array->last_var; i++) {
59 if (zend_bitset_in(used_vars, i)) {
60 vars_map[i] = num_cvs++;
61 } else {
62 vars_map[i] = (uint32_t) -1;
63 }
64 }
65
66 num_tmps = 0;
67 for (i = op_array->last_var; i < op_array->last_var + op_array->T; i++) {
68 if (zend_bitset_in(used_vars, i)) {
69 vars_map[i] = num_cvs + num_tmps++;
70 } else {
71 vars_map[i] = (uint32_t) -1;
72 }
73 }
74
75 free_alloca(used_vars, use_heap1);
76 if (num_cvs == op_array->last_var && num_tmps == op_array->T) {
77 free_alloca(vars_map, use_heap2);
78 return;
79 }
80
81 ZEND_ASSERT(num_cvs <= op_array->last_var);
82 ZEND_ASSERT(num_tmps <= op_array->T);
83
84 /* Update CV and TMP references in opcodes */
85 for (i = 0; i < op_array->last; i++) {
86 zend_op *opline = &op_array->opcodes[i];
87 if (opline->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
88 opline->op1.var = NUM_VAR(vars_map[VAR_NUM(opline->op1.var)]);
89 }
90 if (opline->op2_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
91 opline->op2.var = NUM_VAR(vars_map[VAR_NUM(opline->op2.var)]);
92 }
93 if (opline->result_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
94 opline->result.var = NUM_VAR(vars_map[VAR_NUM(opline->result.var)]);
95 }
96 }
97
98 /* Update CV name table */
99 if (num_cvs != op_array->last_var) {
100 if (num_cvs) {
101 zend_string **names = safe_emalloc(sizeof(zend_string *), num_cvs, 0);
102 for (i = 0; i < op_array->last_var; i++) {
103 if (vars_map[i] != (uint32_t) -1) {
104 names[vars_map[i]] = op_array->vars[i];
105 } else {
106 zend_string_release_ex(op_array->vars[i], 0);
107 }
108 }
109 efree(op_array->vars);
110 op_array->vars = names;
111 } else {
112 for (i = 0; i < op_array->last_var; i++) {
113 zend_string_release_ex(op_array->vars[i], 0);
114 }
115 efree(op_array->vars);
116 op_array->vars = NULL;
117 }
118 op_array->last_var = num_cvs;
119 }
120
121 op_array->T = num_tmps + ZEND_OBSERVER_ENABLED; // reserve last temporary for observers if enabled
122
123 free_alloca(vars_map, use_heap2);
124 }
125
