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(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
  95 static inline void __put_unaligned_2_le(__u32 __v, register __u8 *__p)
  96 {
  97         *__p++ = __v;
  98         *__p++ = __v >> 8;
  99 }
 100
 101 static inline void __put_unaligned_2_be(__u32 __v, register __u8 *__p)
 102 {
 103         *__p++ = __v >> 8;
 104         *__p++ = __v;
 105 }
 106
 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
 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
 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
 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