diff options
Diffstat (limited to 'lib/div64.c')
| -rw-r--r-- | lib/div64.c | 52 |
1 files changed, 42 insertions, 10 deletions
diff --git a/lib/div64.c b/lib/div64.c index a111eb8de9cf..5b4919191778 100644 --- a/lib/div64.c +++ b/lib/div64.c @@ -77,26 +77,58 @@ s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) EXPORT_SYMBOL(div_s64_rem); #endif -/* 64bit divisor, dividend and result. dynamic precision */ +/** + * div64_u64 - unsigned 64bit divide with 64bit divisor + * @dividend: 64bit dividend + * @divisor: 64bit divisor + * + * This implementation is a modified version of the algorithm proposed + * by the book 'Hacker's Delight'. The original source and full proof + * can be found here and is available for use without restriction. + * + * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c' + */ #ifndef div64_u64 u64 div64_u64(u64 dividend, u64 divisor) { - u32 high, d; + u32 high = divisor >> 32; + u64 quot; - high = divisor >> 32; - if (high) { - unsigned int shift = fls(high); + if (high == 0) { + quot = div_u64(dividend, divisor); + } else { + int n = 1 + fls(high); + quot = div_u64(dividend >> n, divisor >> n); - d = divisor >> shift; - dividend >>= shift; - } else - d = divisor; + if (quot != 0) + quot--; + if ((dividend - quot * divisor) >= divisor) + quot++; + } - return div_u64(dividend, d); + return quot; } EXPORT_SYMBOL(div64_u64); #endif +/** + * div64_s64 - signed 64bit divide with 64bit divisor + * @dividend: 64bit dividend + * @divisor: 64bit divisor + */ +#ifndef div64_s64 +s64 div64_s64(s64 dividend, s64 divisor) +{ + s64 quot, t; + + quot = div64_u64(abs64(dividend), abs64(divisor)); + t = (dividend ^ divisor) >> 63; + + return (quot ^ t) - t; +} +EXPORT_SYMBOL(div64_s64); +#endif + #endif /* BITS_PER_LONG == 32 */ /* |