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s390/bitops: use flogr instruction to implement __ffs, ffs, __fls, fls and fls64

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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: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2013-09-19 11:05:32 +02:00 committed by Martin Schwidefsky
parent 746479cdcb
commit b1cb7e2b6c
1 changed files with 125 additions and 0 deletions
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125
arch/s390/include/asm/bitops.h
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@ -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>