sys/gnu/vfs/ext2fs/i386-bitops.h

   1 /*
   2  * $FreeBSD: src/sys/gnu/ext2fs/i386-bitops.h,v 1.5 1999/11/15 23:16:06 obrien Exp $
   3  */
   4 /*
   5  * this is mixture of i386/bitops.h and asm/string.h
   6  * taken from the Linux source tree
   7  *
   8  * XXX replace with Mach routines or reprogram in C
   9  */
  10 #ifndef _VFS_GNU_EXT2FS_I386_BITOPS_H_
  11 #define _VFS_GNU_EXT2FS_I386_BITOPS_H_
  12
  13 /*
  14  * Copyright 1992, Linus Torvalds.
  15  */
  16
  17 /*
  18  * These have to be done with inline assembly: that way the bit-setting
  19  * is guaranteed to be atomic. All bit operations return 0 if the bit
  20  * was cleared before the operation and != 0 if it was not.
  21  *
  22  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  23  */
  24
  25 /*
  26  * Some hacks to defeat gcc over-optimizations..
  27  */
  28 struct __dummy { unsigned long a[100]; };
  29 #define ADDR (*(struct __dummy *) addr)
  30
  31 static __inline__ int
  32 set_bit(int nr, void *addr)
  33 {
  34         int oldbit;
  35
  36         __asm__ __volatile__("btsl %2,%1\n\tsbbl %0,%0"
  37                 :"=r" (oldbit),"=m" (ADDR)
  38                 :"ir" (nr));
  39         return oldbit;
  40 }
  41
  42 static __inline__ int
  43 clear_bit(int nr, void *addr)
  44 {
  45         int oldbit;
  46
  47         __asm__ __volatile__("btrl %2,%1\n\tsbbl %0,%0"
  48                 :"=r" (oldbit),"=m" (ADDR)
  49                 :"ir" (nr));
  50         return oldbit;
  51 }
  52
  53 static __inline__ int
  54 change_bit(int nr, void *addr)
  55 {
  56         int oldbit;
  57
  58         __asm__ __volatile__("btcl %2,%1\n\tsbbl %0,%0"
  59                 :"=r" (oldbit),"=m" (ADDR)
  60                 :"ir" (nr));
  61         return oldbit;
  62 }
  63
  64 /*
  65  * This routine doesn't need to be atomic, but it's faster to code it
  66  * this way.
  67  */
  68 static __inline__ int
  69 test_bit(int nr, void *addr)
  70 {
  71         int oldbit;
  72
  73         __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
  74                 :"=r" (oldbit)
  75                 :"m" (ADDR),"ir" (nr));
  76         return oldbit;
  77 }
  78
  79 /*
  80  * Find-bit routines..
  81  */
  82 static __inline__ int
  83 find_first_zero_bit(void *addr, unsigned size)
  84 {
  85         int res;
  86         int _count = (size + 31) >> 5;
  87
  88         if (!size)
  89                 return 0;
  90         __asm__("                       \n\
  91                 cld                     \n\
  92                 movl $-1,%%eax          \n\
  93                 xorl %%edx,%%edx        \n\
  94                 repe; scasl             \n\
  95                 je 1f                   \n\
  96                 xorl -4(%%edi),%%eax    \n\
  97                 subl $4,%%edi           \n\
  98                 bsfl %%eax,%%edx        \n\
  99 1:              subl %%ebx,%%edi        \n\
 100                 shll $3,%%edi           \n\
 101                 addl %%edi,%%edx"
 102                 : "=c" (_count), "=D" (addr), "=d" (res)
 103                 : "0" (_count), "1" (addr), "b" (addr)
 104                 : "ax");
 105         return res;
 106 }
 107
 108 static __inline__ int
 109 find_next_zero_bit(void *addr, int size, int offset)
 110 {
 111         unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
 112         int set = 0, bit = offset & 31, res;
 113
 114         if (bit) {
 115                 /*
 116                  * Look for zero in first byte
 117                  */
 118                 __asm__("                       \n\
 119                         bsfl %1,%0              \n\
 120                         jne 1f                  \n\
 121                         movl $32, %0            \n\
 122 1:                      "
 123                         : "=r" (set)
 124                         : "r" (~(*p >> bit)));
 125                 if (set < (32 - bit))
 126                         return set + offset;
 127                 set = 32 - bit;
 128                 p++;
 129         }
 130         /*
 131          * No zero yet, search remaining full bytes for a zero
 132          */
 133         res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
 134         return (offset + set + res);
 135 }
 136
 137 /*
 138  * ffz = Find First Zero in word. Undefined if no zero exists,
 139  * so code should check against ~0UL first..
 140  */
 141 static __inline__ unsigned long
 142 ffz(unsigned long word)
 143 {
 144         __asm__("bsfl %1,%0"
 145                 :"=r" (word)
 146                 :"r" (~word));
 147         return word;
 148 }
 149
 150 /*
 151  * memscan() taken from linux asm/string.h
 152  */
 153 /*
 154  * find the first occurrence of byte 'c', or 1 past the area if none
 155  */
 156 static __inline__ char *
 157 memscan(void *addr, unsigned char c, int size)
 158 {
 159         if (!size)
 160                 return addr;
 161         __asm__("                       \n\
 162                 cld                     \n\
 163                 repnz; scasb            \n\
 164                 jnz 1f                  \n\
 165                 dec %%edi               \n\
 166 1:              "
 167                 : "=D" (addr), "=c" (size)
 168                 : "0" (addr), "1" (size), "a" (c));
 169         return addr;
 170 }
 171
 172 #endif /* _VFS_GNU_EXT2FS_I386_BITOPS_H_ */