include/asm-v850/unaligned.h

   1 /*
   2  * include/asm-v850/unaligned.h -- Unaligned memory access
   3  *
   4  *  Copyright (C) 2001  NEC Corporation
   5  *  Copyright (C) 2001  Miles Bader <miles@gnu.org>
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file COPYING in the main directory of this
   9  * archive for more details.
  10  *
  11  * This file is a copy of the arm version, include/asm-arm/unaligned.h
  12  *
  13  * Note that some v850 chips support unaligned access, but it seems too
  14  * annoying to use.
  15  */
  16
  17 #ifndef __V850_UNALIGNED_H__
  18 #define __V850_UNALIGNED_H__
  19
  20 #include <asm/types.h>
  21
  22 extern int __bug_unaligned_x(void *ptr);
  23
  24 /*
  25  * What is the most efficient way of loading/storing an unaligned value?
  26  *
  27  * That is the subject of this file.  Efficiency here is defined as
  28  * minimum code size with minimum register usage for the common cases.
  29  * It is currently not believed that long longs are common, so we
  30  * trade efficiency for the chars, shorts and longs against the long
  31  * longs.
  32  *
  33  * Current stats with gcc 2.7.2.2 for these functions:
  34  *
  35  *      ptrsize get:    code    regs    put:    code    regs
  36  *      1               1       1               1       2
  37  *      2               3       2               3       2
  38  *      4               7       3               7       3
  39  *      8               20      6               16      6
  40  *
  41  * gcc 2.95.1 seems to code differently:
  42  *
  43  *      ptrsize get:    code    regs    put:    code    regs
  44  *      1               1       1               1       2
  45  *      2               3       2               3       2
  46  *      4               7       4               7       4
  47  *      8               19      8               15      6
  48  *
  49  * which may or may not be more efficient (depending upon whether
  50  * you can afford the extra registers).  Hopefully the gcc 2.95
  51  * is inteligent enough to decide if it is better to use the
  52  * extra register, but evidence so far seems to suggest otherwise.
  53  *
  54  * Unfortunately, gcc is not able to optimise the high word
  55  * out of long long >> 32, or the low word from long long << 32
  56  */
  57
  58 #define __get_unaligned_2(__p)                                  \
  59         (__p[0] | __p[1] << 8)
  60
  61 #define __get_unaligned_4(__p)                                  \
  62         (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
  63
  64 #define get_unaligned(ptr)                                      \
  65         ({                                                      \
  66                 __typeof__(*(ptr)) __v;                         \
  67                 __u8 *__p = (__u8 *)(ptr);                      \
  68                 switch (sizeof(*(ptr))) {                       \
  69                 case 1: __v = *(ptr);                   break;  \
  70                 case 2: __v = __get_unaligned_2(__p);   break;  \
  71                 case 4: __v = __get_unaligned_4(__p);   break;  \
  72                 case 8: {                                       \
  73                                 unsigned int __v1, __v2;        \
  74                                 __v2 = __get_unaligned_4((__p+4)); \
  75                                 __v1 = __get_unaligned_4(__p);  \
  76                                 __v = ((unsigned long long)__v2 << 32 | __v1);  \
  77                         }                                       \
  78                         break;                                  \
  79                 default: __v = __bug_unaligned_x(__p);  break;  \
  80                 }                                               \
  81                 __v;                                            \
  82         })
  83
  84
  85 extern inline void __put_unaligned_2(__u32 __v, register __u8 *__p)
  86 {
  87         *__p++ = __v;
  88         *__p++ = __v >> 8;
  89 }
  90
  91 extern inline void __put_unaligned_4(__u32 __v, register __u8 *__p)
  92 {
  93         __put_unaligned_2(__v >> 16, __p + 2);
  94         __put_unaligned_2(__v, __p);
  95 }
  96
  97 extern inline void __put_unaligned_8(const unsigned long long __v, register __u8 *__p)
  98 {
  99         /*
 100          * tradeoff: 8 bytes of stack for all unaligned puts (2
 101          * instructions), or an extra register in the long long
 102          * case - go for the extra register.
 103          */
 104         __put_unaligned_4(__v >> 32, __p+4);
 105         __put_unaligned_4(__v, __p);
 106 }
 107
 108 /*
 109  * Try to store an unaligned value as efficiently as possible.
 110  */
 111 #define put_unaligned(val,ptr)                                  \
 112         ({                                                      \
 113                 switch (sizeof(*(ptr))) {                       \
 114                 case 1:                                         \
 115                         *(ptr) = (val);                         \
 116                         break;                                  \
 117                 case 2: __put_unaligned_2((val),(__u8 *)(ptr)); \
 118                         break;                                  \
 119                 case 4: __put_unaligned_4((val),(__u8 *)(ptr)); \
 120                         break;                                  \
 121                 case 8: __put_unaligned_8((val),(__u8 *)(ptr)); \
 122                         break;                                  \
 123                 default: __bug_unaligned_x(ptr);                \
 124                         break;                                  \
 125                 }                                               \
 126                 (void) 0;                                       \
 127         })
 128
 129
 130 #endif /* __V850_UNALIGNED_H__ */