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ARM: fix ffs/fls implementations to match x86

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ARMs ffs/fls implementations are not type compatible with x86, so when
they're used in combination with min()/max(), they provoke warnings.
Change these to be inline functions with the correct types, providing
the clz as a separate documentation, and document their individual
behaviours.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2014-01-13 23:34:56 +00:00
parent d6e0a2dd12
commit 23f6620a36
1 changed files with 46 additions and 12 deletions
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58
arch/arm/include/asm/bitops.h
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@ -254,25 +254,59 @@ static inline int constant_fls(int x)
} }
/* /*
* On ARMv5 and above those functions can be implemented around * On ARMv5 and above those functions can be implemented around the
* the clz instruction for much better code efficiency. * clz instruction for much better code efficiency. __clz returns
* the number of leading zeros, zero input will return 32, and
* 0x80000000 will return 0.
*/ */
static inline unsigned int __clz(unsigned int x)
static inline int fls(int x)
{ {
int ret; unsigned int ret;
if (__builtin_constant_p(x))
return constant_fls(x);
asm("clz\t%0, %1" : "=r" (ret) : "r" (x)); asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
ret = 32 - ret;
return ret; return ret;
} }
#define __fls(x) (fls(x) - 1) /*
#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); }) * fls() returns zero if the input is zero, otherwise returns the bit
#define __ffs(x) (ffs(x) - 1) * position of the last set bit, where the LSB is 1 and MSB is 32.
*/
static inline int fls(int x)
{
if (__builtin_constant_p(x))
return constant_fls(x);
return 32 - __clz(x);
}
/*
* __fls() returns the bit position of the last bit set, where the
* LSB is 0 and MSB is 31. Zero input is undefined.
*/
static inline unsigned long __fls(unsigned long x)
{
return fls(x) - 1;
}
/*
* ffs() returns zero if the input was zero, otherwise returns the bit
* position of the first set bit, where the LSB is 1 and MSB is 32.
*/
static inline int ffs(int x)
{
return fls(x & -x);
}
/*
* __ffs() returns the bit position of the first bit set, where the
* LSB is 0 and MSB is 31. Zero input is undefined.
*/
static inline unsigned long __ffs(unsigned long x)
{
return ffs(x) - 1;
}
#define ffz(x) __ffs( ~(x) ) #define ffz(x) __ffs( ~(x) )
#endif #endif