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         (__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_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