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Commit 23f6620a authored by Russell King's avatar Russell King
Browse files

ARM: fix ffs/fls implementations to match x86 



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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent d6e0a2dd

arch/arm/include/asm/bitops.h

+44 −10
Original line number Diff line number Diff line
@@ -254,25 +254,59 @@ static inline int constant_fls(int x) 
}



/*

 * On ARMv5 and above those functions can be implemented around

 * the clz instruction for much better code efficiency.

 * On ARMv5 and above those functions can be implemented around the

 * 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)

{

	unsigned int ret;



	asm("clz\t%0, %1" : "=r" (ret) : "r" (x));



	return ret;

}



/*

 * fls() returns zero if the input is zero, otherwise returns the bit

 * position of the last set bit, where the LSB is 1 and MSB is 32.

 */

static inline int fls(int x)

{

	int ret;



	if (__builtin_constant_p(x))

	       return constant_fls(x);



	asm("clz\t%0, %1" : "=r" (ret) : "r" (x));

       	ret = 32 - ret;

	return ret;

	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 __fls(x) (fls(x) - 1)

#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); })

#define __ffs(x) (ffs(x) - 1)

#define ffz(x) __ffs( ~(x) )



#endif