1 #ifndef __ASM_ARM_UNALIGNED_H
2 #define __ASM_ARM_UNALIGNED_H
4 #include <linux/types.h>
6 extern int __bug_unaligned_x(void *ptr
);
9 * What is the most efficient way of loading/storing an unaligned value?
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
17 * Current stats with gcc 2.7.2.2 for these functions:
19 * ptrsize get: code regs put: code regs
25 * gcc 2.95.1 seems to code differently:
27 * ptrsize get: code regs put: code regs
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.
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
42 #define __get_unaligned_2(__p) \
43 (__p[0] | __p[1] << 8)
45 #define __get_unaligned_4(__p) \
46 (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
48 #define get_unaligned(ptr) \
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(__p); break; \
55 case 4: __v = __get_unaligned_4(__p); break; \
57 unsigned int __v1, __v2; \
58 __v2 = __get_unaligned_4((__p+4)); \
59 __v1 = __get_unaligned_4(__p); \
60 __v = ((unsigned long long)__v2 << 32 | __v1); \
63 default: __v = __bug_unaligned_x(__p); break; \
69 static inline void __put_unaligned_2(__u32 __v
, register __u8
*__p
)
75 static inline void __put_unaligned_4(__u32 __v
, register __u8
*__p
)
77 __put_unaligned_2(__v
>> 16, __p
+ 2);
78 __put_unaligned_2(__v
, __p
);
81 static inline void __put_unaligned_8(const unsigned long long __v
, register __u8
*__p
)
84 * tradeoff: 8 bytes of stack for all unaligned puts (2
85 * instructions), or an extra register in the long long
86 * case - go for the extra register.
88 __put_unaligned_4(__v
>> 32, __p
+4);
89 __put_unaligned_4(__v
, __p
);
93 * Try to store an unaligned value as efficiently as possible.
95 #define put_unaligned(val,ptr) \
97 switch (sizeof(*(ptr))) { \
101 case 2: __put_unaligned_2((val),(__u8 *)(ptr)); \
103 case 4: __put_unaligned_4((val),(__u8 *)(ptr)); \
105 case 8: __put_unaligned_8((val),(__u8 *)(ptr)); \
107 default: __bug_unaligned_x(ptr); \