mirror of
https://github.com/torvalds/linux.git
synced 2024-12-26 21:02:19 +00:00
aacf29bf1b
Provide count_leading/trailing_zeros() macros based on extant arch bit scanning functions rather than reimplementing from scratch in MPILIB. Whilst we're at it, turn count_foo_zeros(n, x) into n = count_foo_zeros(x). Also move the definition to asm-generic as other people may be interested in using it. Signed-off-by: David Howells <dhowells@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com> Cc: Arnd Bergmann <arnd@arndb.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
/* Count leading and trailing zeros functions
|
|
*
|
|
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
|
|
* Written by David Howells (dhowells@redhat.com)
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public Licence
|
|
* as published by the Free Software Foundation; either version
|
|
* 2 of the Licence, or (at your option) any later version.
|
|
*/
|
|
|
|
#ifndef _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_
|
|
#define _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_
|
|
|
|
#include <asm/bitops.h>
|
|
|
|
/**
|
|
* count_leading_zeros - Count the number of zeros from the MSB back
|
|
* @x: The value
|
|
*
|
|
* Count the number of leading zeros from the MSB going towards the LSB in @x.
|
|
*
|
|
* If the MSB of @x is set, the result is 0.
|
|
* If only the LSB of @x is set, then the result is BITS_PER_LONG-1.
|
|
* If @x is 0 then the result is COUNT_LEADING_ZEROS_0.
|
|
*/
|
|
static inline int count_leading_zeros(unsigned long x)
|
|
{
|
|
if (sizeof(x) == 4)
|
|
return BITS_PER_LONG - fls(x);
|
|
else
|
|
return BITS_PER_LONG - fls64(x);
|
|
}
|
|
|
|
#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG
|
|
|
|
/**
|
|
* count_trailing_zeros - Count the number of zeros from the LSB forwards
|
|
* @x: The value
|
|
*
|
|
* Count the number of trailing zeros from the LSB going towards the MSB in @x.
|
|
*
|
|
* If the LSB of @x is set, the result is 0.
|
|
* If only the MSB of @x is set, then the result is BITS_PER_LONG-1.
|
|
* If @x is 0 then the result is COUNT_TRAILING_ZEROS_0.
|
|
*/
|
|
static inline int count_trailing_zeros(unsigned long x)
|
|
{
|
|
#define COUNT_TRAILING_ZEROS_0 (-1)
|
|
|
|
if (sizeof(x) == 4)
|
|
return ffs(x);
|
|
else
|
|
return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0;
|
|
}
|
|
|
|
#endif /* _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ */
|