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Commit b1cb7e2b authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
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s390/bitops: use flogr instruction to implement __ffs, ffs, __fls, fls and fls64 



Since z9 109 we have the flogr instruction which can be used to implement
optimized versions of __ffs, ffs, __fls, fls and fls64.
So implement and use them, instead of the generic variants.
This reduces the size of the kernel image (defconfig, -march=z9-109)
by 19,648 bytes.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 746479cd

arch/s390/include/asm/bitops.h

+125 −0
Original line number Diff line number Diff line
@@ -307,11 +307,136 @@ unsigned long find_first_bit_left(const unsigned long *addr, unsigned long size) 
unsigned long find_next_bit_left(const unsigned long *addr, unsigned long size,

				 unsigned long offset);



#ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES



/**

 * __flogr - find leftmost one

 * @word - The word to search

 *

 * Returns the bit number of the most significant bit set,

 * where the most significant bit has bit number 0.

 * If no bit is set this function returns 64.

 */

static inline unsigned char __flogr(unsigned long word)

{

	if (__builtin_constant_p(word)) {

		unsigned long bit = 0;



		if (!word)

			return 64;

		if (!(word & 0xffffffff00000000UL)) {

			word <<= 32;

			bit += 32;

		}

		if (!(word & 0xffff000000000000UL)) {

			word <<= 16;

			bit += 16;

		}

		if (!(word & 0xff00000000000000UL)) {

			word <<= 8;

			bit += 8;

		}

		if (!(word & 0xf000000000000000UL)) {

			word <<= 4;

			bit += 4;

		}

		if (!(word & 0xc000000000000000UL)) {

			word <<= 2;

			bit += 2;

		}

		if (!(word & 0x8000000000000000UL)) {

			word <<= 1;

			bit += 1;

		}

		return bit;

	} else {

		register unsigned long bit asm("4") = word;

		register unsigned long out asm("5");



		asm volatile(

			"       flogr   %[bit],%[bit]\n"

			: [bit] "+d" (bit), [out] "=d" (out) : : "cc");

		return bit;

	}

}



/**

 * __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)

{

	return __flogr(-word & word) ^ (BITS_PER_LONG - 1);

}



/**

 * ffs - find first bit set

 * @word: the word to search

 *

 * This is defined the same way as the libc and

 * compiler builtin ffs routines (man ffs).

 */

static inline int ffs(int word)

{

	unsigned long mask = 2 * BITS_PER_LONG - 1;

	unsigned int val = (unsigned int)word;



	return (1 + (__flogr(-val & val) ^ (BITS_PER_LONG - 1))) & mask;

}



/**

 * __fls - find last (most-significant) set bit in a long word

 * @word: the word to search

 *

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

 */

static inline unsigned long __fls(unsigned long word)

{

	return __flogr(word) ^ (BITS_PER_LONG - 1);

}



/**

 * fls64 - find last set bit in a 64-bit word

 * @word: the word to search

 *

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

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

 *

 * fls64(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 64.

 */

static inline int fls64(unsigned long word)

{

	unsigned long mask = 2 * BITS_PER_LONG - 1;



	return (1 + (__flogr(word) ^ (BITS_PER_LONG - 1))) & mask;

}



/**

 * fls - find last (most-significant) bit set

 * @word: the word to search

 *

 * This is defined the same way as ffs.

 * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.

 */

static inline int fls(int word)

{

	return fls64((unsigned int)word);

}



#else /* CONFIG_HAVE_MARCH_Z9_109_FEATURES */



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

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

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

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

#include <asm-generic/bitops/fls64.h>



#endif /* CONFIG_HAVE_MARCH_Z9_109_FEATURES */



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

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

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