2 * $FreeBSD: src/sys/gnu/ext2fs/i386-bitops.h,v 1.5 1999/11/15 23:16:06 obrien Exp $
5 * this is mixture of i386/bitops.h and asm/string.h
6 * taken from the Linux source tree
8 * XXX replace with Mach routines or reprogram in C
10 #ifndef _VFS_GNU_EXT2FS_I386_BITOPS_H_
11 #define _VFS_GNU_EXT2FS_I386_BITOPS_H_
14 * Copyright 1992, Linus Torvalds.
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.
22 * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
26 * Some hacks to defeat gcc over-optimizations..
28 struct __dummy { unsigned long a[100]; };
29 #define ADDR (*(struct __dummy *) addr)
32 set_bit(int nr, void *addr)
36 __asm__ __volatile__("btsl %2,%1\n\tsbbl %0,%0"
37 :"=r" (oldbit),"=m" (ADDR)
43 clear_bit(int nr, void *addr)
47 __asm__ __volatile__("btrl %2,%1\n\tsbbl %0,%0"
48 :"=r" (oldbit),"=m" (ADDR)
54 change_bit(int nr, void *addr)
58 __asm__ __volatile__("btcl %2,%1\n\tsbbl %0,%0"
59 :"=r" (oldbit),"=m" (ADDR)
65 * This routine doesn't need to be atomic, but it's faster to code it
69 test_bit(int nr, void *addr)
73 __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
75 :"m" (ADDR),"ir" (nr));
83 find_first_zero_bit(void *addr, unsigned size)
86 int _count = (size + 31) >> 5;
96 xorl -4(%%edi),%%eax \n\
99 1: subl %%ebx,%%edi \n\
102 : "=c" (_count), "=D" (addr), "=d" (res)
103 : "0" (_count), "1" (addr), "b" (addr)
108 static __inline__ int
109 find_next_zero_bit(void *addr, int size, int offset)
111 unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
112 int set = 0, bit = offset & 31, res;
116 * Look for zero in first byte
124 : "r" (~(*p >> bit)));
125 if (set < (32 - bit))
131 * No zero yet, search remaining full bytes for a zero
133 res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
134 return (offset + set + res);
138 * ffz = Find First Zero in word. Undefined if no zero exists,
139 * so code should check against ~0UL first..
141 static __inline__ unsigned long
142 ffz(unsigned long word)
151 * memscan() taken from linux asm/string.h
154 * find the first occurrence of byte 'c', or 1 past the area if none
156 static __inline__ char *
157 memscan(void *addr, unsigned char c, int size)
167 : "=D" (addr), "=c" (size)
168 : "0" (addr), "1" (size), "a" (c));
172 #endif /* _VFS_GNU_EXT2FS_I386_BITOPS_H_ */