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Commit 12d9c842 authored by Alexander van Heukelum's avatar Alexander van Heukelum Committed by Ingo Molnar
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x86: merge the simple bitops and move them to bitops.h 



Some of those can be written in such a way that the same
inline assembly can be used to generate both 32 bit and
64 bit code.

For ffs and fls, x86_64 unconditionally used the cmov
instruction and i386 unconditionally used a conditional
branch over a mov instruction. In the current patch I
chose to select the version based on the availability
of the cmov instruction instead. A small detail here is
that x86_64 did not previously set CONFIG_X86_CMOV=y.

Improved comments for ffs, ffz, fls and variations.

Signed-off-by: default avatarAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 64970b68

arch/x86/Kconfig.cpu

+1 −1
Original line number Diff line number Diff line
@@ -398,7 +398,7 @@ config X86_TSC 
# generates cmov.

config X86_CMOV

	def_bool y

	depends on (MK7 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7)

	depends on (MK7 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || X86_64)



config X86_MINIMUM_CPU_FAMILY

	int

include/asm-x86/bitops.h

+98 −1
Original line number Diff line number Diff line
@@ -67,7 +67,6 @@ static inline void __set_bit(int nr, volatile void *addr) 
		     : "Ir" (nr) : "memory");

}





/**

 * clear_bit - Clears a bit in memory

 * @nr: Bit to clear
@@ -304,6 +303,104 @@ static int test_bit(int nr, const volatile unsigned long *addr); 


#undef BASE_ADDR

#undef BIT_ADDR

/**

 * __ffs - find first set bit in word

 * @word: The word to search

 *

 * Undefined if no bit exists, so code should check against 0 first.

 */

static inline unsigned long __ffs(unsigned long word)

{

	__asm__("bsf %1,%0"

		:"=r" (word)

		:"rm" (word));

	return word;

}



/**

 * ffz - find first zero bit in word

 * @word: The word to search

 *

 * Undefined if no zero exists, so code should check against ~0UL first.

 */

static inline unsigned long ffz(unsigned long word)

{

	__asm__("bsf %1,%0"

		:"=r" (word)

		:"r" (~word));

	return word;

}



/*

 * __fls: find last set bit in word

 * @word: The word to search

 *

 * Undefined if no zero exists, so code should check against ~0UL first.

 */

static inline unsigned long __fls(unsigned long word)

{

	__asm__("bsr %1,%0"

		:"=r" (word)

		:"rm" (word));

	return word;

}



#ifdef __KERNEL__

/**

 * ffs - find first set bit in word

 * @x: the word to search

 *

 * This is defined the same way as the libc and compiler builtin ffs

 * routines, therefore differs in spirit from the other bitops.

 *

 * ffs(value) returns 0 if value is 0 or the position of the first

 * set bit if value is nonzero. The first (least significant) bit

 * is at position 1.

 */

static inline int ffs(int x)

{

	int r;

#ifdef CONFIG_X86_CMOV

	__asm__("bsfl %1,%0\n\t"

		"cmovzl %2,%0"

		: "=r" (r) : "rm" (x), "r" (-1));

#else

	__asm__("bsfl %1,%0\n\t"

		"jnz 1f\n\t"

		"movl $-1,%0\n"

		"1:" : "=r" (r) : "rm" (x));

#endif

	return r + 1;

}



/**

 * fls - find last set bit in word

 * @x: the word to search

 *

 * This is defined in a similar way as the libc and compiler builtin

 * ffs, but returns the position of the most significant set bit.

 *

 * fls(value) returns 0 if value is 0 or the position of the last

 * set bit if value is nonzero. The last (most significant) bit is

 * at position 32.

 */

static inline int fls(int x)

{

	int r;

#ifdef CONFIG_X86_CMOV

	__asm__("bsrl %1,%0\n\t"

		"cmovzl %2,%0"

		: "=&r" (r) : "rm" (x), "rm" (-1));

#else

	__asm__("bsrl %1,%0\n\t"

		"jnz 1f\n\t"

		"movl $-1,%0\n"

		"1:" : "=r" (r) : "rm" (x));

#endif

	return r + 1;

}

#endif /* __KERNEL__ */



#undef ADDR



#ifdef CONFIG_X86_32

include/asm-x86/bitops_32.h

+0 −64
Original line number Diff line number Diff line
@@ -39,20 +39,6 @@ static inline int find_first_zero_bit(const unsigned long *addr, unsigned size) 
	return res;

}



/**

 * __ffs - find first bit in word.

 * @word: The word to search

 *

 * Undefined if no bit exists, so code should check against 0 first.

 */

static inline unsigned long __ffs(unsigned long word)

{

	__asm__("bsfl %1,%0"

		:"=r" (word)

		:"rm" (word));

	return word;

}



/**

 * find_first_bit - find the first set bit in a memory region

 * @addr: The address to start the search at
@@ -74,60 +60,10 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size) 
	return x;

}



/**

 * ffz - find first zero in word.

 * @word: The word to search

 *

 * Undefined if no zero exists, so code should check against ~0UL first.

 */

static inline unsigned long ffz(unsigned long word)

{

	__asm__("bsfl %1,%0"

		:"=r" (word)

		:"r" (~word));

	return word;

}



#ifdef __KERNEL__



#include <asm-generic/bitops/sched.h>



/**

 * ffs - find first bit set

 * @x: the word to search

 *

 * This is defined the same way as

 * the libc and compiler builtin ffs routines, therefore

 * differs in spirit from the above ffz() (man ffs).

 */

static inline int ffs(int x)

{

	int r;



	__asm__("bsfl %1,%0\n\t"

		"jnz 1f\n\t"

		"movl $-1,%0\n"

		"1:" : "=r" (r) : "rm" (x));

	return r+1;

}



/**

 * fls - find last bit set

 * @x: the word to search

 *

 * This is defined the same way as ffs().

 */

static inline int fls(int x)

{

	int r;



	__asm__("bsrl %1,%0\n\t"

		"jnz 1f\n\t"

		"movl $-1,%0\n"

		"1:" : "=r" (r) : "rm" (x));

	return r+1;

}



#include <asm-generic/bitops/hweight.h>



#endif /* __KERNEL__ */

include/asm-x86/bitops_64.h

+0 −76
Original line number Diff line number Diff line
@@ -35,70 +35,10 @@ static inline void set_bit_string(unsigned long *bitmap, unsigned long i, 
	}

}



/**

 * ffz - find first zero in word.

 * @word: The word to search

 *

 * Undefined if no zero exists, so code should check against ~0UL first.

 */

static inline unsigned long ffz(unsigned long word)

{

	__asm__("bsfq %1,%0"

		:"=r" (word)

		:"r" (~word));

	return word;

}



/**

 * __ffs - find first bit in word.

 * @word: The word to search

 *

 * Undefined if no bit exists, so code should check against 0 first.

 */

static inline unsigned long __ffs(unsigned long word)

{

	__asm__("bsfq %1,%0"

		:"=r" (word)

		:"rm" (word));

	return word;

}



/*

 * __fls: find last bit set.

 * @word: The word to search

 *

 * Undefined if no zero exists, so code should check against ~0UL first.

 */

static inline unsigned long __fls(unsigned long word)

{

	__asm__("bsrq %1,%0"

		:"=r" (word)

		:"rm" (word));

	return word;

}



#ifdef __KERNEL__



#include <asm-generic/bitops/sched.h>



/**

 * ffs - find first bit set

 * @x: the word to search

 *

 * This is defined the same way as

 * the libc and compiler builtin ffs routines, therefore

 * differs in spirit from the above ffz (man ffs).

 */

static inline int ffs(int x)

{

	int r;



	__asm__("bsfl %1,%0\n\t"

		"cmovzl %2,%0" 

		: "=r" (r) : "rm" (x), "r" (-1));

	return r+1;

}



/**

 * fls64 - find last bit set in 64 bit word

 * @x: the word to search
@@ -112,22 +52,6 @@ static inline int fls64(__u64 x) 
	return __fls(x) + 1;

}



/**

 * fls - find last bit set

 * @x: the word to search

 *

 * This is defined the same way as ffs.

 */

static inline int fls(int x)

{

	int r;



	__asm__("bsrl %1,%0\n\t"

		"cmovzl %2,%0"

		: "=&r" (r) : "rm" (x), "rm" (-1));

	return r+1;

}



#define ARCH_HAS_FAST_MULTIPLIER 1



#include <asm-generic/bitops/hweight.h>