diff options
Diffstat (limited to 'include/linux/math64.h')
| -rw-r--r-- | include/linux/math64.h | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/include/linux/math64.h b/include/linux/math64.h index c45c089bfdac..44282ec7b682 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -142,6 +142,13 @@ static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) } #endif /* mul_u64_u32_shr */ +#ifndef mul_u64_u64_shr +static inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int shift) +{ + return (u64)(((unsigned __int128)a * mul) >> shift); +} +#endif /* mul_u64_u64_shr */ + #else #ifndef mul_u64_u32_shr @@ -161,6 +168,50 @@ static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) } #endif /* mul_u64_u32_shr */ +#ifndef mul_u64_u64_shr +static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift) +{ + union { + u64 ll; + struct { +#ifdef __BIG_ENDIAN + u32 high, low; +#else + u32 low, high; +#endif + } l; + } rl, rm, rn, rh, a0, b0; + u64 c; + + a0.ll = a; + b0.ll = b; + + rl.ll = (u64)a0.l.low * b0.l.low; + rm.ll = (u64)a0.l.low * b0.l.high; + rn.ll = (u64)a0.l.high * b0.l.low; + rh.ll = (u64)a0.l.high * b0.l.high; + + /* + * Each of these lines computes a 64-bit intermediate result into "c", + * starting at bits 32-95. The low 32-bits go into the result of the + * multiplication, the high 32-bits are carried into the next step. + */ + rl.l.high = c = (u64)rl.l.high + rm.l.low + rn.l.low; + rh.l.low = c = (c >> 32) + rm.l.high + rn.l.high + rh.l.low; + rh.l.high = (c >> 32) + rh.l.high; + + /* + * The 128-bit result of the multiplication is in rl.ll and rh.ll, + * shift it right and throw away the high part of the result. + */ + if (shift == 0) + return rl.ll; + if (shift < 64) + return (rl.ll >> shift) | (rh.ll << (64 - shift)); + return rh.ll >> (shift & 63); +} +#endif /* mul_u64_u64_shr */ + #endif #endif /* _LINUX_MATH64_H */ |