include/asm-mn10300/unaligned.h

   1 /* MN10300 Unaligned memory access handling
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #ifndef _ASM_UNALIGNED_H
  12 #define _ASM_UNALIGNED_H
  13
  14 #include <asm/types.h>
  15
  16 #if 0
  17 extern int __bug_unaligned_x(void *ptr);
  18
  19 /*
  20  * What is the most efficient way of loading/storing an unaligned value?
  21  *
  22  * That is the subject of this file.  Efficiency here is defined as
  23  * minimum code size with minimum register usage for the common cases.
  24  * It is currently not believed that long longs are common, so we
  25  * trade efficiency for the chars, shorts and longs against the long
  26  * longs.
  27  *
  28  * Current stats with gcc 2.7.2.2 for these functions:
  29  *
  30  *      ptrsize get:    code    regs    put:    code    regs
  31  *      1               1       1               1       2
  32  *      2               3       2               3       2
  33  *      4               7       3               7       3
  34  *      8               20      6               16      6
  35  *
  36  * gcc 2.95.1 seems to code differently:
  37  *
  38  *      ptrsize get:    code    regs    put:    code    regs
  39  *      1               1       1               1       2
  40  *      2               3       2               3       2
  41  *      4               7       4               7       4
  42  *      8               19      8               15      6
  43  *
  44  * which may or may not be more efficient (depending upon whether
  45  * you can afford the extra registers).  Hopefully the gcc 2.95
  46  * is inteligent enough to decide if it is better to use the
  47  * extra register, but evidence so far seems to suggest otherwise.
  48  *
  49  * Unfortunately, gcc is not able to optimise the high word
  50  * out of long long >> 32, or the low word from long long << 32
  51  */
  52
  53 #define __get_unaligned_2(__p)                                  \
  54         (__p[0] | __p[1] << 8)
  55
  56 #define __get_unaligned_4(__p)                                  \
  57         (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
  58
  59 #define get_unaligned(ptr)                                      \
  60 ({                                                              \
  61         unsigned int __v1, __v2;                                \
  62         __typeof__(*(ptr)) __v;                                 \
  63         __u8 *__p = (__u8 *)(ptr);                              \
  64                                                                 \
  65         switch (sizeof(*(ptr))) {                               \
  66         case 1: __v = *(ptr);                   break;          \
  67         case 2: __v = __get_unaligned_2(__p);   break;          \
  68         case 4: __v = __get_unaligned_4(__p);   break;          \
  69         case 8:                                                 \
  70                 __v2 = __get_unaligned_4((__p+4));              \
  71                 __v1 = __get_unaligned_4(__p);                  \
  72                 __v = ((unsigned long long)__v2 << 32 | __v1);  \
  73                 break;                                          \
  74         default: __v = __bug_unaligned_x(__p);  break;          \
  75         }                                                       \
  76         __v;                                                    \
  77 })
  78
  79
  80 static inline void __put_unaligned_2(__u32 __v, register __u8 *__p)
  81 {
  82         *__p++ = __v;
  83         *__p++ = __v >> 8;
  84 }
  85
  86 static inline void __put_unaligned_4(__u32 __v, register __u8 *__p)
  87 {
  88         __put_unaligned_2(__v >> 16, __p + 2);
  89         __put_unaligned_2(__v, __p);
  90 }
  91
  92 static inline void __put_unaligned_8(const unsigned long long __v, __u8 *__p)
  93 {
  94         /*
  95          * tradeoff: 8 bytes of stack for all unaligned puts (2
  96          * instructions), or an extra register in the long long
  97          * case - go for the extra register.
  98          */
  99         __put_unaligned_4(__v >> 32, __p + 4);
 100         __put_unaligned_4(__v, __p);
 101 }
 102
 103 /*
 104  * Try to store an unaligned value as efficiently as possible.
 105  */
 106 #define put_unaligned(val, ptr)                                         \
 107         ({                                                              \
 108                 switch (sizeof(*(ptr))) {                               \
 109                 case 1:                                                 \
 110                         *(ptr) = (val);                                 \
 111                         break;                                          \
 112                 case 2:                                                 \
 113                         __put_unaligned_2((val), (__u8 *)(ptr));        \
 114                         break;                                          \
 115                 case 4:                                                 \
 116                         __put_unaligned_4((val), (__u8 *)(ptr));        \
 117                         break;                                          \
 118                 case 8:                                                 \
 119                         __put_unaligned_8((val), (__u8 *)(ptr));        \
 120                         break;                                          \
 121                 default:                                                \
 122                         __bug_unaligned_x(ptr);                         \
 123                         break;                                          \
 124                 }                                                       \
 125                 (void) 0;                                               \
 126         })
 127
 128
 129 #else
 130
 131 #define get_unaligned(ptr) (*(ptr))
 132 #define put_unaligned(val, ptr) ({ *(ptr) = (val); (void) 0; })
 133
 134 #endif
 135
 136 #endif