1 /*
2 * Copyright (C) 2012 Oracle.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
16 */
17
18 #include "smatch.h"
19
20 static int my_id;
21
22 #if 0
23 static unsigned long long find_possible_bits(struct expression *expr)
24 {
25 sval_t sval;
26 unsigned long long ret;
27 int set;
28 int i;
29
30 expr = strip_expr(expr);
31
32 if (get_implied_value(expr, &sval))
33 return sval.uvalue;
34
35 if (expr->type == EXPR_BINOP && (expr->op == '&' || expr->op == '|')) {
36 unsigned long long left, right;
37
38 left = find_possible_bits(expr->left);
39 if (!left)
40 return 0;
41 right = find_possible_bits(expr->right);
42 if (!right)
43 return 0;
44
45 if (expr->op == '&')
46 return left & right;
47 return left | right;
48 }
49
50 get_absolute_max(expr, &sval);
51 ret = sval.value;
52
53 set = false;
54 for (i = 63; i >= 0; i--) {
55 if (ret & 1 << i)
56 set = true;
57 if (set)
58 ret |= 1 << i;
59 }
60 return ret;
61 }
62 #endif
63
get_possible_bits(struct expression * expr)64 static unsigned long long get_possible_bits(struct expression *expr)
65 {
66 sval_t sval;
67
68 expr = strip_expr(expr);
69 if (expr->type != EXPR_BINOP)
70 return 0;
71 if (expr->op != '&')
72 return 0;
73 if (!get_implied_value(expr->right, &sval))
74 return 0;
75
76 return sval.uvalue;
77 }
78
match_condition(struct expression * expr)79 static void match_condition(struct expression *expr)
80 {
81 struct symbol *type;
82 sval_t sval;
83 unsigned long long left_mask, right_mask;
84 char *str;
85
86 type = get_type(expr);
87 if (!type)
88 type = &int_ctype;
89
90 if (expr->type != EXPR_COMPARE)
91 return;
92 if (expr->op != SPECIAL_EQUAL && expr->op != SPECIAL_NOTEQUAL)
93 return;
94
95 if (!get_value(expr->right, &sval))
96 return;
97 right_mask = sval.uvalue;
98
99 left_mask = get_possible_bits(expr->left);
100 if (!left_mask)
101 return;
102
103 if (type_bits(type) < 64) {
104 left_mask &= (1ULL << type_bits(type)) - 1;
105 right_mask &= (1ULL << type_bits(type)) - 1;
106 }
107
108 if ((left_mask & right_mask) == right_mask)
109 return;
110
111 str = expr_to_str(expr);
112 sm_warning("masked condition '%s' is always %s.", str,
113 expr->op == SPECIAL_EQUAL ? "false" : "true");
114 free_string(str);
115 }
116
check_impossible_mask(int id)117 void check_impossible_mask(int id)
118 {
119 my_id = id;
120
121 add_hook(&match_condition, CONDITION_HOOK);
122 }
123