Commit 2cc7b6a4 authored by Yury Norov's avatar Yury Norov Committed by Linus Torvalds
Browse files

lib: add fast path for find_first_*_bit() and find_last_bit() 

Similarly to bitmap functions, users would benefit if we'll handle a case
of small-size bitmaps that fit into a single word.

While here, move the find_last_bit() declaration to bitops/find.h where
other find_*_bit() functions sit.

Link: https://lkml.kernel.org/r/20210401003153.97325-11-yury.norov@gmail.com


Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
Acked-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Cc: Alexey Klimov <aklimov@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Sterba <dsterba@suse.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jianpeng Ma <jianpeng.ma@intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Stefano Brivio <sbrivio@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 277a20a4

include/asm-generic/bitops/find.h

+46 −4
Original line number Diff line number Diff line
@@ -5,6 +5,9 @@ 
extern unsigned long _find_next_bit(const unsigned long *addr1,

		const unsigned long *addr2, unsigned long nbits,

		unsigned long start, unsigned long invert, unsigned long le);

extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);

extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);

extern unsigned long _find_last_bit(const unsigned long *addr, unsigned long size);



#ifndef find_next_bit

/**
@@ -102,8 +105,17 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, 
 * Returns the bit number of the first set bit.

 * If no bits are set, returns @size.

 */

extern unsigned long find_first_bit(const unsigned long *addr,

				    unsigned long size);

static inline

unsigned long find_first_bit(const unsigned long *addr, unsigned long size)

{

	if (small_const_nbits(size)) {

		unsigned long val = *addr & GENMASK(size - 1, 0);



		return val ? __ffs(val) : size;

	}



	return _find_first_bit(addr, size);

}



/**

 * find_first_zero_bit - find the first cleared bit in a memory region
@@ -113,8 +125,17 @@ extern unsigned long find_first_bit(const unsigned long *addr, 
 * Returns the bit number of the first cleared bit.

 * If no bits are zero, returns @size.

 */

extern unsigned long find_first_zero_bit(const unsigned long *addr,

					 unsigned long size);

static inline

unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)

{

	if (small_const_nbits(size)) {

		unsigned long val = *addr | ~GENMASK(size - 1, 0);



		return val == ~0UL ? size : ffz(val);

	}



	return _find_first_zero_bit(addr, size);

}

#else /* CONFIG_GENERIC_FIND_FIRST_BIT */



#ifndef find_first_bit
@@ -126,6 +147,27 @@ extern unsigned long find_first_zero_bit(const unsigned long *addr, 


#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */



#ifndef find_last_bit

/**

 * find_last_bit - find the last set bit in a memory region

 * @addr: The address to start the search at

 * @size: The number of bits to search

 *

 * Returns the bit number of the last set bit, or size.

 */

static inline

unsigned long find_last_bit(const unsigned long *addr, unsigned long size)

{

	if (small_const_nbits(size)) {

		unsigned long val = *addr & GENMASK(size - 1, 0);



		return val ? __fls(val) : size;

	}



	return _find_last_bit(addr, size);

}

#endif



/**

 * find_next_clump8 - find next 8-bit clump with set bits in a memory region

 * @clump: location to store copy of found clump

include/linux/bitops.h

+0 −12
Original line number Diff line number Diff line
@@ -286,17 +286,5 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr, 
})

#endif



#ifndef find_last_bit

/**

 * find_last_bit - find the last set bit in a memory region

 * @addr: The address to start the search at

 * @size: The number of bits to search

 *

 * Returns the bit number of the last set bit, or size.

 */

extern unsigned long find_last_bit(const unsigned long *addr,

				   unsigned long size);

#endif



#endif /* __KERNEL__ */

#endif

lib/find_bit.c

+6 −6
Original line number Diff line number Diff line
@@ -75,7 +75,7 @@ EXPORT_SYMBOL(_find_next_bit); 
/*

 * Find the first set bit in a memory region.

 */

unsigned long find_first_bit(const unsigned long *addr, unsigned long size)

unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)

{

	unsigned long idx;
@@ -86,14 +86,14 @@ unsigned long find_first_bit(const unsigned long *addr, unsigned long size) 


	return size;

}

EXPORT_SYMBOL(find_first_bit);

EXPORT_SYMBOL(_find_first_bit);

#endif



#ifndef find_first_zero_bit

/*

 * Find the first cleared bit in a memory region.

 */

unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)

unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)

{

	unsigned long idx;
@@ -104,11 +104,11 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size) 


	return size;

}

EXPORT_SYMBOL(find_first_zero_bit);

EXPORT_SYMBOL(_find_first_zero_bit);

#endif



#ifndef find_last_bit

unsigned long find_last_bit(const unsigned long *addr, unsigned long size)

unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)

{

	if (size) {

		unsigned long val = BITMAP_LAST_WORD_MASK(size);
@@ -124,7 +124,7 @@ unsigned long find_last_bit(const unsigned long *addr, unsigned long size) 
	}

	return size;

}

EXPORT_SYMBOL(find_last_bit);

EXPORT_SYMBOL(_find_last_bit);

#endif



unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,