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x86: generic versions of find_first_(zero_)bit, convert i386

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Generic versions of __find_first_bit and __find_first_zero_bit
are introduced as simplified versions of __find_next_bit and
__find_next_zero_bit. Their compilation and use are guarded by
a new config variable GENERIC_FIND_FIRST_BIT.

The generic versions of find_first_bit and find_first_zero_bit
are implemented in terms of the newly introduced __find_first_bit
and __find_first_zero_bit.

This patch does not remove the i386-specific implementation,
but it does switch i386 to use the generic functions by setting
GENERIC_FIND_FIRST_BIT=y for X86_32.

Signed-off-by: Alexander van Heukelum <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Alexander van Heukelum 2008-04-01 11:46:19 +02:00 • committed by Ingo Molnar
commit 77b9bd9c49
5 changed files with 98 additions and 0 deletions
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1
lib/Makefile
View file

@ -29,6 +29,7 @@ obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o

58
lib/find_next_bit.c
View file

@ -16,6 +16,7 @@
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
#ifdef CONFIG_GENERIC_FIND_NEXT_BIT
/*
* Find the next set bit in a memory region.
*/
@ -102,6 +103,63 @@ found_middle:
return result + ffz(tmp);
}
EXPORT_SYMBOL(__find_next_zero_bit);
#endif /* CONFIG_GENERIC_FIND_NEXT_BIT */
#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
/*
* Find the first set bit in a memory region.
*/
unsigned long __find_first_bit(const unsigned long *addr,
unsigned long size)
{
const unsigned long *p = addr;
unsigned long result = 0;
unsigned long tmp;
while (size & ~(BITS_PER_LONG-1)) {
if ((tmp = *(p++)))
goto found;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
}
if (!size)
return result;
tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
if (tmp == 0UL) /* Are any bits set? */
return result + size; /* Nope. */
found:
return result + __ffs(tmp);
}
EXPORT_SYMBOL(__find_first_bit);
/*
* Find the first cleared bit in a memory region.
*/
unsigned long __find_first_zero_bit(const unsigned long *addr,
unsigned long size)
{
const unsigned long *p = addr;
unsigned long result = 0;
unsigned long tmp;
while (size & ~(BITS_PER_LONG-1)) {
if (~(tmp = *(p++)))
goto found;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
}
if (!size)
return result;
tmp = (*p) | (~0UL << size);
if (tmp == ~0UL) /* Are any bits zero? */
return result + size; /* Nope. */
found:
return result + ffz(tmp);
}
EXPORT_SYMBOL(__find_first_zero_bit);
#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
#ifdef __BIG_ENDIAN