| #ifndef _LINUX_RECIPROCAL_DIV_H |
| #define _LINUX_RECIPROCAL_DIV_H |
| * This file describes reciprocical division. |
| * This optimizes the (A/B) problem, when A and B are two u32 |
| * and B is a known value (but not known at compile time) |
| * The math principle used is : |
| * Let RECIPROCAL_VALUE(B) be (((1LL << 32) + (B - 1))/ B) |
| * Then A / B = (u32)(((u64)(A) * (R)) >> 32) |
| * This replaces a divide by a multiply (and a shift), and |
| * is generally less expensive in CPU cycles. |
| * Computes the reciprocal value (R) for the value B of the divisor. |
| * Should not be called before each reciprocal_divide(), |
| * or else the performance is slower than a normal divide. |
| extern u32 reciprocal_value(u32 B); |
| static inline u32 reciprocal_divide(u32 A, u32 R) |
| return (u32)(((u64)A * R) >> 32); |