5db03cf3b90525d2164175288bd0f5a28f3efe7a
[linux-3.10.git] / include / asm-arm / unaligned.h
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(const 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         (unsigned int)(__p[0] | __p[1] << 8)
44
45 #define __get_unaligned_2_be(__p)                                       \
46         (unsigned int)(__p[0] << 8 | __p[1])
47
48 #define __get_unaligned_4_le(__p)                                       \
49         (unsigned int)(__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
50
51 #define __get_unaligned_4_be(__p)                                       \
52         (unsigned int)(__p[0] << 24 | __p[1] << 16 | __p[2] << 8 | __p[3])
53
54 #define __get_unaligned_8_le(__p)                                       \
55         ((unsigned long long)__get_unaligned_4_le((__p+4)) << 32 |      \
56                 __get_unaligned_4_le(__p))
57
58 #define __get_unaligned_8_be(__p)                                       \
59         ((unsigned long long)__get_unaligned_4_be(__p) << 32 |          \
60                 __get_unaligned_4_be((__p+4)))
61
62 #define __get_unaligned_le(ptr)                                         \
63         ((__force typeof(*(ptr)))({                                     \
64                 const __u8 *__p = (const __u8 *)(ptr);                  \
65                 __builtin_choose_expr(sizeof(*(ptr)) == 1, *__p,        \
66                   __builtin_choose_expr(sizeof(*(ptr)) == 2, __get_unaligned_2_le(__p), \
67                   __builtin_choose_expr(sizeof(*(ptr)) == 4, __get_unaligned_4_le(__p), \
68                   __builtin_choose_expr(sizeof(*(ptr)) == 8, __get_unaligned_8_le(__p), \
69                     (void)__bug_unaligned_x(__p)))));                   \
70         }))
71
72 #define __get_unaligned_be(ptr)                                         \
73         ((__force typeof(*(ptr)))({                                     \
74                 const __u8 *__p = (const __u8 *)(ptr);                  \
75                 __builtin_choose_expr(sizeof(*(ptr)) == 1, *__p,        \
76                   __builtin_choose_expr(sizeof(*(ptr)) == 2, __get_unaligned_2_be(__p), \
77                   __builtin_choose_expr(sizeof(*(ptr)) == 4, __get_unaligned_4_be(__p), \
78                   __builtin_choose_expr(sizeof(*(ptr)) == 8, __get_unaligned_8_be(__p), \
79                     (void)__bug_unaligned_x(__p)))));                   \
80         }))
81
82
83 static inline void __put_unaligned_2_le(__u32 __v, register __u8 *__p)
84 {
85         *__p++ = __v;
86         *__p++ = __v >> 8;
87 }
88
89 static inline void __put_unaligned_2_be(__u32 __v, register __u8 *__p)
90 {
91         *__p++ = __v >> 8;
92         *__p++ = __v;
93 }
94
95 static inline void __put_unaligned_4_le(__u32 __v, register __u8 *__p)
96 {
97         __put_unaligned_2_le(__v >> 16, __p + 2);
98         __put_unaligned_2_le(__v, __p);
99 }
100
101 static inline void __put_unaligned_4_be(__u32 __v, register __u8 *__p)
102 {
103         __put_unaligned_2_be(__v >> 16, __p);
104         __put_unaligned_2_be(__v, __p + 2);
105 }
106
107 static inline void __put_unaligned_8_le(const unsigned long long __v, register __u8 *__p)
108 {
109         /*
110          * tradeoff: 8 bytes of stack for all unaligned puts (2
111          * instructions), or an extra register in the long long
112          * case - go for the extra register.
113          */
114         __put_unaligned_4_le(__v >> 32, __p+4);
115         __put_unaligned_4_le(__v, __p);
116 }
117
118 static inline void __put_unaligned_8_be(const unsigned long long __v, register __u8 *__p)
119 {
120         /*
121          * tradeoff: 8 bytes of stack for all unaligned puts (2
122          * instructions), or an extra register in the long long
123          * case - go for the extra register.
124          */
125         __put_unaligned_4_be(__v >> 32, __p);
126         __put_unaligned_4_be(__v, __p+4);
127 }
128
129 /*
130  * Try to store an unaligned value as efficiently as possible.
131  */
132 #define __put_unaligned_le(val,ptr)                                     \
133         ({                                                      \
134                 (void)sizeof(*(ptr) = (val));                   \
135                 switch (sizeof(*(ptr))) {                       \
136                 case 1:                                         \
137                         *(ptr) = (val);                         \
138                         break;                                  \
139                 case 2: __put_unaligned_2_le((__force u16)(val),(__u8 *)(ptr)); \
140                         break;                                  \
141                 case 4: __put_unaligned_4_le((__force u32)(val),(__u8 *)(ptr)); \
142                         break;                                  \
143                 case 8: __put_unaligned_8_le((__force u64)(val),(__u8 *)(ptr)); \
144                         break;                                  \
145                 default: __bug_unaligned_x(ptr);                \
146                         break;                                  \
147                 }                                               \
148                 (void) 0;                                       \
149         })
150
151 #define __put_unaligned_be(val,ptr)                                     \
152         ({                                                      \
153                 (void)sizeof(*(ptr) = (val));                   \
154                 switch (sizeof(*(ptr))) {                       \
155                 case 1:                                         \
156                         *(ptr) = (val);                         \
157                         break;                                  \
158                 case 2: __put_unaligned_2_be((__force u16)(val),(__u8 *)(ptr)); \
159                         break;                                  \
160                 case 4: __put_unaligned_4_be((__force u32)(val),(__u8 *)(ptr)); \
161                         break;                                  \
162                 case 8: __put_unaligned_8_be((__force u64)(val),(__u8 *)(ptr)); \
163                         break;                                  \
164                 default: __bug_unaligned_x(ptr);                \
165                         break;                                  \
166                 }                                               \
167                 (void) 0;                                       \
168         })
169
170 /*
171  * Select endianness
172  */
173 #ifndef __ARMEB__
174 #define get_unaligned   __get_unaligned_le
175 #define put_unaligned   __put_unaligned_le
176 #else
177 #define get_unaligned   __get_unaligned_be
178 #define put_unaligned   __put_unaligned_be
179 #endif
180
181 #endif