diff options
Diffstat (limited to 'include/qemu/bitops.h')
-rw-r--r-- | include/qemu/bitops.h | 55 |
1 files changed, 22 insertions, 33 deletions
diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h index 74e14e5..8b88791 100644 --- a/include/qemu/bitops.h +++ b/include/qemu/bitops.h @@ -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); } /** |