[PATCH] include: <linux/math64.h>: sync with upstream
Sascha Hauer
sha at pengutronix.de
Tue Jan 5 08:38:12 EST 2021
On Tue, Dec 29, 2020 at 01:32:54PM +0100, Ahmad Fatoum wrote:
> The header implements definitions for the 64-bit division helpers
> on 64-bit builds only. For 32-bit builds, it can only provide prototypes
> and the actual implementation will need to come from elsewhere.
>
> We didn't have any out-of-line definitions in barebox with the result
> that functions like div_s64_rem() were so far only usable in
> 64-bit barebox builds. On 32-bit builds, they would result in a linker
> error.
>
> Import the Linux v5.11-rc1 generic out-of-line 64-bit math on 32-bit
> implementation to fix this. While at it, synchronize the header to
> reduce diff to upstream.
>
> Signed-off-by: Ahmad Fatoum <ahmad at a3f.at>
> ---
> include/linux/math64.h | 211 +++++++++++++++++++++++++++++++++++-
> lib/Makefile | 1 +
> lib/math/Makefile | 1 +
> lib/math/div64.c | 235 +++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 443 insertions(+), 5 deletions(-)
> create mode 100644 lib/math/Makefile
> create mode 100644 lib/math/div64.c
Applied, thanks
Sascha
>
> diff --git a/include/linux/math64.h b/include/linux/math64.h
> index 71dd6d7109b7..e8b737e70e50 100644
> --- a/include/linux/math64.h
> +++ b/include/linux/math64.h
> @@ -1,3 +1,4 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> #ifndef _LINUX_MATH64_H
> #define _LINUX_MATH64_H
>
> @@ -6,10 +7,16 @@
>
> #if BITS_PER_LONG == 64
>
> -#define div64_long(x,y) div64_s64((x),(y))
> +#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
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 32bit divisor
> + * @remainder: pointer to unsigned 32bit remainder
> + *
> + * Return: sets ``*remainder``, then returns dividend / divisor
> *
> * This is commonly provided by 32bit archs to provide an optimized 64bit
> * divide.
> @@ -20,8 +27,13 @@ static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
> return dividend / divisor;
> }
>
> -/**
> +/*
> * div_s64_rem - signed 64bit divide with 32bit divisor with remainder
> + * @dividend: signed 64bit dividend
> + * @divisor: signed 32bit divisor
> + * @remainder: pointer to signed 32bit remainder
> + *
> + * Return: sets ``*remainder``, then returns dividend / divisor
> */
> static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
> {
> @@ -29,16 +41,38 @@ static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
> return dividend / divisor;
> }
>
> -/**
> +/*
> + * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 64bit divisor
> + * @remainder: pointer to unsigned 64bit remainder
> + *
> + * Return: sets ``*remainder``, then returns dividend / divisor
> + */
> +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
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 64bit divisor
> + *
> + * Return: dividend / divisor
> */
> static inline u64 div64_u64(u64 dividend, u64 divisor)
> {
> return dividend / divisor;
> }
>
> -/**
> +/*
> * div64_s64 - signed 64bit divide with 64bit divisor
> + * @dividend: signed 64bit dividend
> + * @divisor: signed 64bit divisor
> + *
> + * Return: dividend / divisor
> */
> static inline s64 div64_s64(s64 dividend, s64 divisor)
> {
> @@ -47,7 +81,8 @@ static inline s64 div64_s64(s64 dividend, s64 divisor)
>
> #elif BITS_PER_LONG == 32
>
> -#define div64_long(x,y) div_s64((x),(y))
> +#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)
> @@ -61,6 +96,10 @@ 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
> @@ -73,6 +112,8 @@ extern s64 div64_s64(s64 dividend, s64 divisor);
>
> /**
> * div_u64 - unsigned 64bit divide with 32bit divisor
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 32bit divisor
> *
> * This is the most common 64bit divide and should be used if possible,
> * as many 32bit archs can optimize this variant better than a full 64bit
> @@ -88,6 +129,8 @@ static inline u64 div_u64(u64 dividend, u32 divisor)
>
> /**
> * div_s64 - signed 64bit divide with 32bit divisor
> + * @dividend: signed 64bit dividend
> + * @divisor: signed 32bit divisor
> */
> #ifndef div_s64
> static inline s64 div_s64(s64 dividend, s32 divisor)
> @@ -99,6 +142,164 @@ static inline s64 div_s64(s64 dividend, s32 divisor)
>
> u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
>
> +#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 */
> +
> +u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div);
> +
> +#define DIV64_U64_ROUND_UP(ll, d) \
> + ({ u64 _tmp = (d); div64_u64((ll) + _tmp - 1, _tmp); })
> +
> +/**
> + * DIV64_U64_ROUND_CLOSEST - unsigned 64bit divide with 64bit divisor rounded to nearest integer
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 64bit divisor
> + *
> + * Divide unsigned 64bit dividend by unsigned 64bit divisor
> + * and round to closest integer.
> + *
> + * Return: dividend / divisor rounded to nearest integer
> + */
> +#define DIV64_U64_ROUND_CLOSEST(dividend, divisor) \
> + ({ u64 _tmp = (divisor); div64_u64((dividend) + _tmp / 2, _tmp); })
> +
> +/*
> + * DIV_S64_ROUND_CLOSEST - signed 64bit divide with 32bit divisor rounded to nearest integer
> + * @dividend: signed 64bit dividend
> + * @divisor: signed 32bit divisor
> + *
> + * Divide signed 64bit dividend by signed 32bit divisor
> + * and round to closest integer.
> + *
> + * Return: dividend / divisor rounded to nearest integer
> + */
> +#define DIV_S64_ROUND_CLOSEST(dividend, divisor)( \
> +{ \
> + s64 __x = (dividend); \
> + s32 __d = (divisor); \
> + ((__x > 0) == (__d > 0)) ? \
> + div_s64((__x + (__d / 2)), __d) : \
> + div_s64((__x - (__d / 2)), __d); \
> +} \
> +)
> +
> static __always_inline u32
> __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
> {
> diff --git a/lib/Makefile b/lib/Makefile
> index ba6af6f2ab24..9c6f4133d77c 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -25,6 +25,7 @@ obj-y += cmdlinepart.o
> obj-y += recursive_action.o
> obj-y += make_directory.o
> obj-y += math.o
> +obj-y += math/
> obj-$(CONFIG_XXHASH) += xxhash.o
> obj-$(CONFIG_BZLIB) += decompress_bunzip2.o
> obj-$(CONFIG_ZLIB) += decompress_inflate.o zlib_inflate/
> diff --git a/lib/math/Makefile b/lib/math/Makefile
> new file mode 100644
> index 000000000000..3341a8e4744b
> --- /dev/null
> +++ b/lib/math/Makefile
> @@ -0,0 +1 @@
> +obj-y += div64.o
> diff --git a/lib/math/div64.c b/lib/math/div64.c
> new file mode 100644
> index 000000000000..507de8216a3e
> --- /dev/null
> +++ b/lib/math/div64.c
> @@ -0,0 +1,235 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2003 Bernardo Innocenti <bernie at develer.com>
> + *
> + * Based on former do_div() implementation from asm-parisc/div64.h:
> + * Copyright (C) 1999 Hewlett-Packard Co
> + * Copyright (C) 1999 David Mosberger-Tang <davidm at hpl.hp.com>
> + *
> + *
> + * Generic C version of 64bit/32bit division and modulo, with
> + * 64bit result and 32bit remainder.
> + *
> + * The fast case for (n>>32 == 0) is handled inline by do_div().
> + *
> + * 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/ppc/lib/div64.S and arch/sh/lib/div64.S
> + * or by defining a preprocessor macro in arch/include/asm/div64.h.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/export.h>
> +#include <linux/kernel.h>
> +#include <linux/math64.h>
> +#include <linux/log2.h>
> +
> +/* 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;
> + uint64_t res, d = 1;
> + uint32_t high = rem >> 32;
> +
> + /* Reduce the thing a bit first */
> + res = 0;
> + if (high >= base) {
> + high /= base;
> + res = (uint64_t) high << 32;
> + rem -= (uint64_t) (high*base) << 32;
> + }
> +
> + while ((int64_t)b > 0 && b < rem) {
> + b = b+b;
> + d = d+d;
> + }
> +
> + do {
> + if (rem >= b) {
> + rem -= b;
> + res += d;
> + }
> + b >>= 1;
> + d >>= 1;
> + } while (d);
> +
> + *n = res;
> + return rem;
> +}
> +EXPORT_SYMBOL(__div64_32);
> +#endif
> +
> +/**
> + * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
> + * @dividend: 64bit dividend
> + * @divisor: 64bit divisor
> + * @remainder: 64bit remainder
> + */
> +#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 = 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 = 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);
> +
> +#ifndef mul_u64_u64_div_u64
> +u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
> +{
> + u64 res = 0, div, rem;
> + int shift;
> +
> + /* can a * b overflow ? */
> + if (ilog2(a) + ilog2(b) > 62) {
> + /*
> + * (b * a) / c is equal to
> + *
> + * (b / c) * a +
> + * (b % c) * a / c
> + *
> + * if nothing overflows. Can the 1st multiplication
> + * overflow? Yes, but we do not care: this can only
> + * happen if the end result can't fit in u64 anyway.
> + *
> + * So the code below does
> + *
> + * res = (b / c) * a;
> + * b = b % c;
> + */
> + div = div64_u64_rem(b, c, &rem);
> + res = div * a;
> + b = rem;
> +
> + shift = ilog2(a) + ilog2(b) - 62;
> + if (shift > 0) {
> + /* drop precision */
> + b >>= shift;
> + c >>= shift;
> + if (!c)
> + return res;
> + }
> + }
> +
> + return res + div64_u64(a * b, c);
> +}
> +#endif
> --
> 2.29.2
>
>
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