diff --git a/include/div64.h b/include/div64.h index d833144..cecb232 100644 --- a/include/div64.h +++ b/include/div64.h @@ -4,13 +4,16 @@ * Copyright (C) 2003 Bernardo Innocenti * Based on former asm-ppc/div64.h and asm-m68knommu/div64.h * + * Optimization for constant divisors on 32-bit machines: + * Copyright (C) 2006-2015 Nicolas Pitre + * * The semantics of do_div() are: * * uint32_t do_div(uint64_t *n, uint32_t base) * { - * uint32_t remainder = *n % base; - * *n = *n / base; - * return remainder; + * uint32_t remainder = *n % base; + * *n = *n / base; + * return remainder; * } * * NOTE: macro parameter n is evaluated multiple times, @@ -18,8 +21,182 @@ */ #include +#include + +#if BITS_PER_LONG == 64 + +# define do_div(n,base) ({ \ + uint32_t __base = (base); \ + uint32_t __rem; \ + __rem = ((uint64_t)(n)) % __base; \ + (n) = ((uint64_t)(n)) / __base; \ + __rem; \ + }) + +#elif BITS_PER_LONG == 32 + +#include + +/* + * If the divisor happens to be constant, we determine the appropriate + * inverse at compile time to turn the division into a few inline + * multiplications which ought to be much faster. And yet only if compiling + * with a sufficiently recent gcc version to perform proper 64-bit constant + * propagation. + * + * (It is unfortunate that gcc doesn't perform all this internally.) + */ + +#ifndef __div64_const32_is_OK +#define __div64_const32_is_OK (__GNUC__ >= 4) +#endif + +#define __div64_const32(n, ___b) \ +({ \ + /* \ + * Multiplication by reciprocal of b: n / b = n * (p / b) / p \ + * \ + * We rely on the fact that most of this code gets optimized \ + * away at compile time due to constant propagation and only \ + * a few multiplication instructions should remain. \ + * Hence this monstrous macro (static inline doesn't always \ + * do the trick here). \ + */ \ + uint64_t ___res, ___x, ___t, ___m, ___n = (n); \ + uint32_t ___p, ___bias; \ + \ + /* determine MSB of b */ \ + ___p = 1 << ilog2(___b); \ + \ + /* compute m = ((p << 64) + b - 1) / b */ \ + ___m = (~0ULL / ___b) * ___p; \ + ___m += (((~0ULL % ___b + 1) * ___p) + ___b - 1) / ___b; \ + \ + /* one less than the dividend with highest result */ \ + ___x = ~0ULL / ___b * ___b - 1; \ + \ + /* test our ___m with res = m * x / (p << 64) */ \ + ___res = ((___m & 0xffffffff) * (___x & 0xffffffff)) >> 32; \ + ___t = ___res += (___m & 0xffffffff) * (___x >> 32); \ + ___res += (___x & 0xffffffff) * (___m >> 32); \ + ___t = (___res < ___t) ? (1ULL << 32) : 0; \ + ___res = (___res >> 32) + ___t; \ + ___res += (___m >> 32) * (___x >> 32); \ + ___res /= ___p; \ + \ + /* Now sanitize and optimize what we've got. */ \ + if (~0ULL % (___b / (___b & -___b)) == 0) { \ + /* special case, can be simplified to ... */ \ + ___n /= (___b & -___b); \ + ___m = ~0ULL / (___b / (___b & -___b)); \ + ___p = 1; \ + ___bias = 1; \ + } else if (___res != ___x / ___b) { \ + /* \ + * We can't get away without a bias to compensate \ + * for bit truncation errors. To avoid it we'd need an \ + * additional bit to represent m which would overflow \ + * a 64-bit variable. \ + * \ + * Instead we do m = p / b and n / b = (n * m + m) / p. \ + */ \ + ___bias = 1; \ + /* Compute m = (p << 64) / b */ \ + ___m = (~0ULL / ___b) * ___p; \ + ___m += ((~0ULL % ___b + 1) * ___p) / ___b; \ + } else { \ + /* \ + * Reduce m / p, and try to clear bit 31 of m when \ + * possible, otherwise that'll need extra overflow \ + * handling later. \ + */ \ + uint32_t ___bits = -(___m & -___m); \ + ___bits |= ___m >> 32; \ + ___bits = (~___bits) << 1; \ + /* \ + * If ___bits == 0 then setting bit 31 is unavoidable. \ + * Simply apply the maximum possible reduction in that \ + * case. Otherwise the MSB of ___bits indicates the \ + * best reduction we should apply. \ + */ \ + if (!___bits) { \ + ___p /= (___m & -___m); \ + ___m /= (___m & -___m); \ + } else { \ + ___p >>= ilog2(___bits); \ + ___m >>= ilog2(___bits); \ + } \ + /* No bias needed. */ \ + ___bias = 0; \ + } \ + \ + /* \ + * Now we have a combination of 2 conditions: \ + * \ + * 1) whether or not we need to apply a bias, and \ + * \ + * 2) whether or not there might be an overflow in the cross \ + * product determined by (___m & ((1 << 63) | (1 << 31))). \ + * \ + * Select the best way to do (m_bias + m * n) / (1 << 64). \ + * From now on there will be actual runtime code generated. \ + */ \ + ___res = __arch_xprod_64(___m, ___n, ___bias); \ + \ + ___res /= ___p; \ +}) + +#ifndef __arch_xprod_64 +/* + * Default C implementation for __arch_xprod_64() + * + * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias) + * Semantic: retval = ((bias ? m : 0) + m * n) >> 64 + * + * The product is a 128-bit value, scaled down to 64 bits. + * Assuming constant propagation to optimize away unused conditional code. + * Architectures may provide their own optimized assembly implementation. + */ +static inline uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias) +{ + uint32_t m_lo = m; + uint32_t m_hi = m >> 32; + uint32_t n_lo = n; + uint32_t n_hi = n >> 32; + uint64_t res, tmp; + + if (!bias) { + res = ((uint64_t)m_lo * n_lo) >> 32; + } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) { + /* there can't be any overflow here */ + res = (m + (uint64_t)m_lo * n_lo) >> 32; + } else { + res = m + (uint64_t)m_lo * n_lo; + tmp = (res < m) ? (1ULL << 32) : 0; + res = (res >> 32) + tmp; + } + + if (!(m & ((1ULL << 63) | (1ULL << 31)))) { + /* there can't be any overflow here */ + res += (uint64_t)m_lo * n_hi; + res += (uint64_t)m_hi * n_lo; + res >>= 32; + } else { + tmp = res += (uint64_t)m_lo * n_hi; + res += (uint64_t)m_hi * n_lo; + tmp = (res < tmp) ? (1ULL << 32) : 0; + res = (res >> 32) + tmp; + } + res += (uint64_t)m_hi * n_hi; + + return res; +} +#endif + +#ifndef __div64_32 extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); +#endif /* The unnecessary pointer compare is there * to check for type safety (n must be 64bit) @@ -28,14 +205,32 @@ extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); uint32_t __base = (base); \ uint32_t __rem; \ (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ - if (((n) >> 32) == 0) { \ + if (__builtin_constant_p(__base) && \ + is_power_of_2(__base)) { \ + __rem = (n) & (__base - 1); \ + (n) >>= ilog2(__base); \ + } else if (__div64_const32_is_OK && \ + __builtin_constant_p(__base) && \ + __base != 0) { \ + uint32_t __res_lo, __n_lo = (n); \ + (n) = __div64_const32(n, __base); \ + /* the remainder can be computed with 32-bit regs */ \ + __res_lo = (n); \ + __rem = __n_lo - __res_lo * __base; \ + } else if (likely(((n) >> 32) == 0)) { \ __rem = (uint32_t)(n) % __base; \ (n) = (uint32_t)(n) / __base; \ - } else \ + } else \ __rem = __div64_32(&(n), __base); \ __rem; \ }) +#else /* BITS_PER_LONG == ?? */ + +# error do_div() does not yet support the C64 + +#endif /* BITS_PER_LONG */ + /* Wrapper for do_div(). Doesn't modify dividend and returns * the result, not reminder. */ diff --git a/include/linux/math64.h b/include/linux/math64.h index 6d760d7..08584c8 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -1,10 +1,15 @@ #ifndef _LINUX_MATH64_H #define _LINUX_MATH64_H +#include +#include #include #if BITS_PER_LONG == 64 +#define div64_long(x, y) div64_s64((x), (y)) +#define div64_ul(x, y) div64_u64((x), (y)) + /** * div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder * @@ -27,6 +32,15 @@ static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) } /** + * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder + */ +static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) +{ + *remainder = dividend % divisor; + return dividend / divisor; +} + +/** * div64_u64 - unsigned 64bit divide with 64bit divisor */ static inline u64 div64_u64(u64 dividend, u64 divisor) @@ -34,8 +48,19 @@ static inline u64 div64_u64(u64 dividend, u64 divisor) return dividend / divisor; } +/** + * div64_s64 - signed 64bit divide with 64bit divisor + */ +static inline s64 div64_s64(s64 dividend, s64 divisor) +{ + return dividend / divisor; +} + #elif BITS_PER_LONG == 32 +#define div64_long(x, y) div_s64((x), (y)) +#define div64_ul(x, y) div_u64((x), (y)) + #ifndef div_u64_rem static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) { @@ -48,10 +73,18 @@ static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder); #endif +#ifndef div64_u64_rem +extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder); +#endif + #ifndef div64_u64 extern u64 div64_u64(u64 dividend, u64 divisor); #endif +#ifndef div64_s64 +extern s64 div64_s64(s64 dividend, s64 divisor); +#endif + #endif /* BITS_PER_LONG */ /** @@ -82,4 +115,143 @@ static inline s64 div_s64(s64 dividend, s32 divisor) u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder); +static __always_inline u32 +__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) +{ + u32 ret = 0; + + while (dividend >= divisor) { + /* The following asm() prevents the compiler from + optimising this loop into a modulo operation. */ + asm("" : "+rm"(dividend)); + + dividend -= divisor; + ret++; + } + + *remainder = dividend; + + return ret; +} + +#ifndef mul_u32_u32 +/* + * Many a GCC version messes this up and generates a 64x64 mult :-( + */ +static inline u64 mul_u32_u32(u32 a, u32 b) +{ + return (u64)a * b; +} +#endif + +#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__) + +#ifndef mul_u64_u32_shr +static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) +{ + return (u64)(((unsigned __int128)a * mul) >> 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 +static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) +{ + u32 ah, al; + u64 ret; + + al = a; + ah = a >> 32; + + ret = mul_u32_u32(al, mul) >> shift; + if (ah) + ret += mul_u32_u32(ah, mul) << (32 - shift); + + return ret; +} +#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 = mul_u32_u32(a0.l.low, b0.l.low); + rm.ll = mul_u32_u32(a0.l.low, b0.l.high); + rn.ll = mul_u32_u32(a0.l.high, b0.l.low); + rh.ll = mul_u32_u32(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 + +#ifndef mul_u64_u32_div +static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor) +{ + union { + u64 ll; + struct { +#ifdef __BIG_ENDIAN + u32 high, low; +#else + u32 low, high; +#endif + } l; + } u, rl, rh; + + u.ll = a; + rl.ll = mul_u32_u32(u.l.low, mul); + rh.ll = mul_u32_u32(u.l.high, mul) + rl.l.high; + + /* Bits 32-63 of the result will be in rh.l.low. */ + rl.l.high = do_div(rh.ll, divisor); + + /* Bits 0-31 of the result will be in rl.l.low. */ + do_div(rl.ll, divisor); + + rl.l.high = rh.l.low; + return rl.ll; +} +#endif /* mul_u64_u32_div */ + #endif /* _LINUX_MATH64_H */ diff --git a/lib/div64.c b/lib/div64.c index 319fca5..206f582 100644 --- a/lib/div64.c +++ b/lib/div64.c @@ -13,14 +13,19 @@ * * Code generated for this function might be very inefficient * for some CPUs. __div64_32() can be overridden by linking arch-specific - * assembly versions such as arch/powerpc/lib/div64.S and arch/sh/lib/div64.S. + * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S + * or by defining a preprocessor macro in arch/include/asm/div64.h. */ -#include -#include -#include +#include +#include +#include -uint32_t notrace __div64_32(uint64_t *n, uint32_t base) +/* Not needed on 64bit architectures */ +#if BITS_PER_LONG == 32 + +#ifndef __div64_32 +uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) { uint64_t rem = *n; uint64_t b = base; @@ -52,3 +57,129 @@ uint32_t notrace __div64_32(uint64_t *n, uint32_t base) *n = res; return rem; } +EXPORT_SYMBOL(__div64_32); +#endif + +#ifndef div_s64_rem +s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) +{ + u64 quotient; + + if (dividend < 0) { + quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); + *remainder = -*remainder; + if (divisor > 0) + quotient = -quotient; + } else { + quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); + if (divisor < 0) + quotient = -quotient; + } + return quotient; +} +EXPORT_SYMBOL(div_s64_rem); +#endif + +/** + * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder + * @dividend: 64bit dividend + * @divisor: 64bit divisor + * @remainder: 64bit remainder + * + * This implementation is a comparable to algorithm used by div64_u64. + * But this operation, which includes math for calculating the remainder, + * is kept distinct to avoid slowing down the div64_u64 operation on 32bit + * systems. + */ +#ifndef div64_u64_rem +u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) +{ + u32 high = divisor >> 32; + u64 quot; + + if (high == 0) { + u32 rem32; + quot = div_u64_rem(dividend, divisor, &rem32); + *remainder = rem32; + } else { + int n = 1 + fls(high); + quot = div_u64(dividend >> n, divisor >> n); + + if (quot != 0) + quot--; + + *remainder = dividend - quot * divisor; + if (*remainder >= divisor) { + quot++; + *remainder -= divisor; + } + } + + return quot; +} +EXPORT_SYMBOL(div64_u64_rem); +#endif + +/** + * 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/hdcodetxt/divDouble.c.txt' + */ +#ifndef div64_u64 +u64 div64_u64(u64 dividend, u64 divisor) +{ + u32 high = divisor >> 32; + u64 quot; + + if (high == 0) { + quot = div_u64(dividend, divisor); + } else { + int n = 1 + fls(high); + quot = div_u64(dividend >> n, divisor >> n); + + if (quot != 0) + quot--; + if ((dividend - quot * divisor) >= divisor) + quot++; + } + + 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(abs(dividend), abs(divisor)); + t = (dividend ^ divisor) >> 63; + + return (quot ^ t) - t; +} +EXPORT_SYMBOL(div64_s64); +#endif + +#endif /* BITS_PER_LONG == 32 */ + +/* + * Iterative div/mod for use when dividend is not expected to be much + * bigger than divisor. + */ +u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) +{ + return __iter_div_u64_rem(dividend, divisor, remainder); +} +EXPORT_SYMBOL(iter_div_u64_rem);