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bitops: unify bitops_ffsl with the one in host-utils.h, call it bitops_ctzl

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We had two copies of a ffs function for longs with subtly different
semantics and, for the one in bitops.h, a confusing name: the result
was off-by-one compared to the library function ffsl.

Unify the functions into one, and solve the name problem by calling
the 0-based functions "bitops_ctzl" and "bitops_ctol" respectively.

This also fixes the build on platforms with ffsl, including Mac OS X
and Windows.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Andreas Färber <afaerber@suse.de>
Tested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Paolo Bonzini 2013-02-01 23:03:16 +01:00 • committed by Blue Swirl
parent 7b2d977981
commit fbeadf50f2
6 changed files with 28 additions and 65 deletions
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55
include/qemu/bitops.h
View file

@ -13,6 +13,7 @@
#define BITOPS_H
#include "qemu-common.h"
#include "host-utils.h"
#define BITS_PER_BYTE CHAR_BIT
#define BITS_PER_LONG (sizeof (unsigned long) * BITS_PER_BYTE)
@ -23,41 +24,29 @@
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
/**
* bitops_ffs - find first bit in word.
* bitops_ctzl - count trailing zeroes in word.
* @word: The word to search
*
* Undefined if no bit exists, so code should check against 0 first.
* Returns -1 if no bit exists. Note that compared to the C library
* routine ffsl, this one returns one less.
*/
static unsigned long bitops_ffsl(unsigned long word)
static unsigned long bitops_ctzl(unsigned long word)
{
int num = 0;
#if QEMU_GNUC_PREREQ(3, 4)
return __builtin_ffsl(word) - 1;
#else
if (!word) {
return -1;
}
#if LONG_MAX > 0x7FFFFFFF
if ((word & 0xffffffff) == 0) {
num += 32;
word >>= 32;
}
if (sizeof(long) == 4) {
return ctz32(word);
} else if (sizeof(long) == 8) {
return ctz64(word);
} else {
abort();
}
#endif
if ((word & 0xffff) == 0) {
num += 16;
word >>= 16;
}
if ((word & 0xff) == 0) {
num += 8;
word >>= 8;
}
if ((word & 0xf) == 0) {
num += 4;
word >>= 4;
}
if ((word & 0x3) == 0) {
num += 2;
word >>= 2;
}
if ((word & 0x1) == 0) {
num += 1;
}
return num;
}
/**
@ -99,14 +88,14 @@ static inline unsigned long bitops_flsl(unsigned long word)
}
/**
* ffz - find first zero in word.
* cto - count trailing ones in word.
* @word: The word to search
*
* Undefined if no zero exists, so code should check against ~0UL first.
* Returns -1 if all bit are set.
*/
static inline unsigned long ffz(unsigned long word)
static inline unsigned long bitops_ctol(unsigned long word)
{
return bitops_ffsl(~word);
return bitops_ctzl(~word);
}
/**