1 /*
2 +----------------------------------------------------------------------+
3 | Zend Engine, Removing unused variables |
4 +----------------------------------------------------------------------+
5 | Copyright (c) 1998-2018 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: Nikita Popov <nikic@php.net> |
16 +----------------------------------------------------------------------+
17 */
18
19 #include "ZendAccelerator.h"
20 #include "Optimizer/zend_optimizer_internal.h"
21 #include "zend_bitset.h"
22
23 /* This pass removes all CVs that are completely unused. It does *not* merge any CVs.
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_cvs_len = zend_bitset_len(op_array->last_var);
31 zend_bitset used_cvs = ZEND_BITSET_ALLOCA(used_cvs_len, use_heap1);
32 uint32_t *cv_map = do_alloca(op_array->last_var * sizeof(uint32_t), use_heap2);
33 uint32_t num_cvs, tmp_offset;
34
35 /* Determine which CVs are used */
36 zend_bitset_clear(used_cvs, used_cvs_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) {
40 zend_bitset_incl(used_cvs, VAR_NUM(opline->op1.var));
41 }
42 if (opline->op2_type == IS_CV) {
43 zend_bitset_incl(used_cvs, VAR_NUM(opline->op2.var));
44 }
45 if (opline->result_type == IS_CV) {
46 zend_bitset_incl(used_cvs, VAR_NUM(opline->result.var));
47 }
48 }
49
50 num_cvs = 0;
51 for (i = 0; i < op_array->last_var; i++) {
52 if (zend_bitset_in(used_cvs, i)) {
53 cv_map[i] = num_cvs++;
54 } else {
55 cv_map[i] = (uint32_t) -1;
56 }
57 }
58
59 free_alloca(used_cvs, use_heap1);
60 if (num_cvs == op_array->last_var) {
61 free_alloca(cv_map, use_heap2);
62 return;
63 }
64
65 ZEND_ASSERT(num_cvs < op_array->last_var);
66 tmp_offset = op_array->last_var - num_cvs;
67
68 /* Update CV and TMP references in opcodes */
69 for (i = 0; i < op_array->last; i++) {
70 zend_op *opline = &op_array->opcodes[i];
71 if (opline->op1_type == IS_CV) {
72 opline->op1.var = NUM_VAR(cv_map[VAR_NUM(opline->op1.var)]);
73 } else if (opline->op1_type & (IS_VAR|IS_TMP_VAR)) {
74 opline->op1.var -= sizeof(zval) * tmp_offset;
75 }
76 if (opline->op2_type == IS_CV) {
77 opline->op2.var = NUM_VAR(cv_map[VAR_NUM(opline->op2.var)]);
78 } else if (opline->op2_type & (IS_VAR|IS_TMP_VAR)) {
79 opline->op2.var -= sizeof(zval) * tmp_offset;
80 }
81 if (opline->result_type == IS_CV) {
82 opline->result.var = NUM_VAR(cv_map[VAR_NUM(opline->result.var)]);
83 } else if (opline->result_type & (IS_VAR|IS_TMP_VAR)) {
84 opline->result.var -= sizeof(zval) * tmp_offset;
85 }
86 }
87
88 /* Update TMP references in live ranges */
89 if (op_array->live_range) {
90 for (i = 0; i < op_array->last_live_range; i++) {
91 op_array->live_range[i].var -= sizeof(zval) * tmp_offset;
92 }
93 }
94
95 /* Update CV name table */
96 if (num_cvs) {
97 zend_string **names = safe_emalloc(sizeof(zend_string *), num_cvs, 0);
98 for (i = 0; i < op_array->last_var; i++) {
99 if (cv_map[i] != (uint32_t) -1) {
100 names[cv_map[i]] = op_array->vars[i];
101 } else {
102 zend_string_release(op_array->vars[i]);
103 }
104 }
105 efree(op_array->vars);
106 op_array->vars = names;
107 } else {
108 for (i = 0; i < op_array->last_var; i++) {
109 zend_string_release(op_array->vars[i]);
110 }
111 efree(op_array->vars);
112 op_array->vars = NULL;
113 }
114
115 op_array->last_var = num_cvs;
116
117 free_alloca(cv_map, use_heap2);
118 }
119
