1 #ifndef __ASM_ARM_UNALIGNED_H
2 #define __ASM_ARM_UNALIGNED_H
3
4 #include <asm/types.h>
5
6 extern int __bug_unaligned_x(void *ptr);
7
8 /*
9 * What is the most efficient way of loading/storing an unaligned value?
10 *
11 * That is the subject of this file. Efficiency here is defined as
12 * minimum code size with minimum register usage for the common cases.
13 * It is currently not believed that long longs are common, so we
14 * trade efficiency for the chars, shorts and longs against the long
15 * longs.
16 *
17 * Current stats with gcc 2.7.2.2 for these functions:
18 *
19 * ptrsize get: code regs put: code regs
20 * 1 1 1 1 2
21 * 2 3 2 3 2
22 * 4 7 3 7 3
23 * 8 20 6 16 6
24 *
25 * gcc 2.95.1 seems to code differently:
26 *
27 * ptrsize get: code regs put: code regs
28 * 1 1 1 1 2
29 * 2 3 2 3 2
30 * 4 7 4 7 4
31 * 8 19 8 15 6
32 *
33 * which may or may not be more efficient (depending upon whether
34 * you can afford the extra registers). Hopefully the gcc 2.95
35 * is inteligent enough to decide if it is better to use the
36 * extra register, but evidence so far seems to suggest otherwise.
37 *
38 * Unfortunately, gcc is not able to optimise the high word
39 * out of long long >> 32, or the low word from long long << 32
40 */
41
42 #define __get_unaligned_2_le(__p) \
43 (__p[0] | __p[1] << 8)
44
45 #define __get_unaligned_2_be(__p) \
46 (__p[0] << 8 | __p[1])
47
48 #define __get_unaligned_4_le(__p) \
49 (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
50
51 #define __get_unaligned_4_be(__p) \
52 (__p[0] << 24 | __p[1] << 16 | __p[2] << 8 | __p[3])
53
54 #define __get_unaligned_le(ptr) \
55 ({ \
56 __typeof__(*(ptr)) __v; \
57 __u8 *__p = (__u8 *)(ptr); \
58 switch (sizeof(*(ptr))) { \
59 case 1: __v = *(ptr); break; \
60 case 2: __v = __get_unaligned_2_le(__p); break; \
61 case 4: __v = __get_unaligned_4_le(__p); break; \
62 case 8: { \
63 unsigned int __v1, __v2; \
64 __v2 = __get_unaligned_4_le((__p+4)); \
65 __v1 = __get_unaligned_4_le(__p); \
66 __v = ((unsigned long long)__v2 << 32 | __v1); \
67 } \
68 break; \
69 default: __v = __bug_unaligned_x(__p); break; \
70 } \
71 __v; \
72 })
73
74 #define __get_unaligned_be(ptr) \
75 ({ \
76 __typeof__(*(ptr)) __v; \
77 __u8 *__p = (__u8 *)(ptr); \
78 switch (sizeof(*(ptr))) { \
79 case 1: __v = *(ptr); break; \
80 case 2: __v = __get_unaligned_2_be(__p); break; \
81 case 4: __v = __get_unaligned_4_be(__p); break; \
82 case 8: { \
83 unsigned int __v1, __v2; \
84 __v2 = __get_unaligned_4_be(__p); \
85 __v1 = __get_unaligned_4_be((__p+4)); \
86 __v = ((unsigned long long)__v2 << 32 | __v1); \
87 } \
88 break; \
89 default: __v = __bug_unaligned_x(__p); break; \
90 } \
91 __v; \
92 })
93
94
__put_unaligned_2_le(__u32 __v,register __u8 * __p)95 static inline void __put_unaligned_2_le(__u32 __v, register __u8 *__p)
96 {
97 *__p++ = __v;
98 *__p++ = __v >> 8;
99 }
100
__put_unaligned_2_be(__u32 __v,register __u8 * __p)101 static inline void __put_unaligned_2_be(__u32 __v, register __u8 *__p)
102 {
103 *__p++ = __v >> 8;
104 *__p++ = __v;
105 }
106
__put_unaligned_4_le(__u32 __v,register __u8 * __p)107 static inline void __put_unaligned_4_le(__u32 __v, register __u8 *__p)
108 {
109 __put_unaligned_2_le(__v >> 16, __p + 2);
110 __put_unaligned_2_le(__v, __p);
111 }
112
__put_unaligned_4_be(__u32 __v,register __u8 * __p)113 static inline void __put_unaligned_4_be(__u32 __v, register __u8 *__p)
114 {
115 __put_unaligned_2_be(__v >> 16, __p);
116 __put_unaligned_2_be(__v, __p + 2);
117 }
118
__put_unaligned_8_le(const unsigned long long __v,register __u8 * __p)119 static inline void __put_unaligned_8_le(const unsigned long long __v, register __u8 *__p)
120 {
121 /*
122 * tradeoff: 8 bytes of stack for all unaligned puts (2
123 * instructions), or an extra register in the long long
124 * case - go for the extra register.
125 */
126 __put_unaligned_4_le(__v >> 32, __p+4);
127 __put_unaligned_4_le(__v, __p);
128 }
129
__put_unaligned_8_be(const unsigned long long __v,register __u8 * __p)130 static inline void __put_unaligned_8_be(const unsigned long long __v, register __u8 *__p)
131 {
132 /*
133 * tradeoff: 8 bytes of stack for all unaligned puts (2
134 * instructions), or an extra register in the long long
135 * case - go for the extra register.
136 */
137 __put_unaligned_4_be(__v >> 32, __p);
138 __put_unaligned_4_be(__v, __p+4);
139 }
140
141 /*
142 * Try to store an unaligned value as efficiently as possible.
143 */
144 #define __put_unaligned_le(val,ptr) \
145 ({ \
146 switch (sizeof(*(ptr))) { \
147 case 1: \
148 *(ptr) = (val); \
149 break; \
150 case 2: __put_unaligned_2_le((val),(__u8 *)(ptr)); \
151 break; \
152 case 4: __put_unaligned_4_le((val),(__u8 *)(ptr)); \
153 break; \
154 case 8: __put_unaligned_8_le((val),(__u8 *)(ptr)); \
155 break; \
156 default: __bug_unaligned_x(ptr); \
157 break; \
158 } \
159 (void) 0; \
160 })
161
162 #define __put_unaligned_be(val,ptr) \
163 ({ \
164 switch (sizeof(*(ptr))) { \
165 case 1: \
166 *(ptr) = (val); \
167 break; \
168 case 2: __put_unaligned_2_be((val),(__u8 *)(ptr)); \
169 break; \
170 case 4: __put_unaligned_4_be((val),(__u8 *)(ptr)); \
171 break; \
172 case 8: __put_unaligned_8_be((val),(__u8 *)(ptr)); \
173 break; \
174 default: __bug_unaligned_x(ptr); \
175 break; \
176 } \
177 (void) 0; \
178 })
179
180 /*
181 * Select endianness
182 */
183 #ifndef __ARMEB__
184 #define get_unaligned __get_unaligned_le
185 #define put_unaligned __put_unaligned_le
186 #else
187 #define get_unaligned __get_unaligned_be
188 #define put_unaligned __put_unaligned_be
189 #endif
190
191 #endif
192