Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
[linux-2.6] / include / asm-arm26 / 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(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_4_le(__p)                                       \
46         (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
47
48 #define __get_unaligned_le(ptr)                                 \
49         ({                                                      \
50                 __typeof__(*(ptr)) __v;                         \
51                 __u8 *__p = (__u8 *)(ptr);                      \
52                 switch (sizeof(*(ptr))) {                       \
53                 case 1: __v = *(ptr);                   break;  \
54                 case 2: __v = __get_unaligned_2_le(__p);        break;  \
55                 case 4: __v = __get_unaligned_4_le(__p);        break;  \
56                 case 8: {                                       \
57                                 unsigned int __v1, __v2;        \
58                                 __v2 = __get_unaligned_4_le((__p+4)); \
59                                 __v1 = __get_unaligned_4_le(__p);       \
60                                 __v = ((unsigned long long)__v2 << 32 | __v1);  \
61                         }                                       \
62                         break;                                  \
63                 default: __v = __bug_unaligned_x(__p);  break;  \
64                 }                                               \
65                 __v;                                            \
66         })
67
68 static inline void __put_unaligned_2_le(__u32 __v, register __u8 *__p)
69 {
70         *__p++ = __v;
71         *__p++ = __v >> 8;
72 }
73
74 static inline void __put_unaligned_4_le(__u32 __v, register __u8 *__p)
75 {
76         __put_unaligned_2_le(__v >> 16, __p + 2);
77         __put_unaligned_2_le(__v, __p);
78 }
79
80 static inline void __put_unaligned_8_le(const unsigned long long __v, register __u8 *__p)
81 {
82         /*
83          * tradeoff: 8 bytes of stack for all unaligned puts (2
84          * instructions), or an extra register in the long long
85          * case - go for the extra register.
86          */
87         __put_unaligned_4_le(__v >> 32, __p+4);
88         __put_unaligned_4_le(__v, __p);
89 }
90
91 /*
92  * Try to store an unaligned value as efficiently as possible.
93  */
94 #define __put_unaligned_le(val,ptr)                                     \
95         ({                                                      \
96                 switch (sizeof(*(ptr))) {                       \
97                 case 1:                                         \
98                         *(ptr) = (val);                         \
99                         break;                                  \
100                 case 2: __put_unaligned_2_le((val),(__u8 *)(ptr));      \
101                         break;                                  \
102                 case 4: __put_unaligned_4_le((val),(__u8 *)(ptr));      \
103                         break;                                  \
104                 case 8: __put_unaligned_8_le((val),(__u8 *)(ptr)); \
105                         break;                                  \
106                 default: __bug_unaligned_x(ptr);                \
107                         break;                                  \
108                 }                                               \
109                 (void) 0;                                       \
110         })
111
112 /*
113  * Select endianness
114  */
115 #define get_unaligned   __get_unaligned_le
116 #define put_unaligned   __put_unaligned_le
117
118 #endif