This adds a macro to calculate the highest bit set. If used on constant values, no code will be generated.
Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> --- include/qemu/bitops.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h index 304c90c..98ba42a 100644 --- a/include/qemu/bitops.h +++ b/include/qemu/bitops.h @@ -23,6 +23,18 @@ #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) #define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long)) +#define __BITNR(m, n) ((m) == ((m) & (1<<(n)))) ? (n) : +#define BITNR(m) \ + __BITNR((m), 31) __BITNR((m), 30) __BITNR((m), 29) __BITNR((m), 28) \ + __BITNR((m), 27) __BITNR((m), 26) __BITNR((m), 25) __BITNR((m), 24) \ + __BITNR((m), 23) __BITNR((m), 22) __BITNR((m), 21) __BITNR((m), 20) \ + __BITNR((m), 19) __BITNR((m), 18) __BITNR((m), 17) __BITNR((m), 16) \ + __BITNR((m), 15) __BITNR((m), 14) __BITNR((m), 13) __BITNR((m), 12) \ + __BITNR((m), 11) __BITNR((m), 10) __BITNR((m), 9) __BITNR((m), 8) \ + __BITNR((m), 7) __BITNR((m), 6) __BITNR((m), 5) __BITNR((m), 4) \ + __BITNR((m), 3) __BITNR((m), 2) __BITNR((m), 1) __BITNR((m), 0) \ + -1 + /** * set_bit - Set a bit in memory * @nr: the bit to set -- 1.8.4.rc4
