asm-generic/bitops/__ffs.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
0003 #define _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
0004
0005 #include <asm/types.h>
0006 #include <asm/bitsperlong.h>
0007
0008 /**
0009  * __ffs - find first bit in word.
0010  * @word: The word to search
0011  *
0012  * Undefined if no bit exists, so code should check against 0 first.
0013  */
0014 static __always_inline unsigned long __ffs(unsigned long word)
0015 {
0016     int num = 0;
0017
0018 #if __BITS_PER_LONG == 64
0019     if ((word & 0xffffffff) == 0) {
0020         num += 32;
0021         word >>= 32;
0022     }
0023 #endif
0024     if ((word & 0xffff) == 0) {
0025         num += 16;
0026         word >>= 16;
0027     }
0028     if ((word & 0xff) == 0) {
0029         num += 8;
0030         word >>= 8;
0031     }
0032     if ((word & 0xf) == 0) {
0033         num += 4;
0034         word >>= 4;
0035     }
0036     if ((word & 0x3) == 0) {
0037         num += 2;
0038         word >>= 2;
0039     }
0040     if ((word & 0x1) == 0)
0041         num += 1;
0042     return num;
0043 }
0044
0045 #endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_ */