include/qemu/host-utils.h

/*
 * Utility compute operations used by translated code.
 *
 * Copyright (c) 2007 Thiemo Seufer
 * Copyright (c) 2007 Jocelyn Mayer
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/* Portions of this work are licensed under the terms of the GNU GPL,
 * version 2 or later. See the COPYING file in the top-level directory.
 */

#ifndef HOST_UTILS_H
#define HOST_UTILS_H

#include "qemu/compiler.h"
#include "qemu/bswap.h"
#include "qemu/int128.h"

#ifdef CONFIG_INT128
static inline void mulu64(uint64_t *plow, uint64_t *phigh,
                          uint64_t a, uint64_t b)
{
    __uint128_t r = (__uint128_t)a * b;
    *plow = r;
    *phigh = r >> 64;
}

static inline void muls64(uint64_t *plow, uint64_t *phigh,
                          int64_t a, int64_t b)
{
    __int128_t r = (__int128_t)a * b;
    *plow = r;
    *phigh = r >> 64;
}

/* compute with 96 bit intermediate result: (a*b)/c */
static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
{
    return (__int128_t)a * b / c;
}

static inline uint64_t divu128(uint64_t *plow, uint64_t *phigh,
                               uint64_t divisor)
{
    __uint128_t dividend = ((__uint128_t)*phigh << 64) | *plow;
    __uint128_t result = dividend / divisor;

    *plow = result;
    *phigh = result >> 64;
    return dividend % divisor;
}

static inline int64_t divs128(uint64_t *plow, int64_t *phigh,
                              int64_t divisor)
{
    __int128_t dividend = ((__int128_t)*phigh << 64) | *plow;
    __int128_t result = dividend / divisor;

    *plow = result;
    *phigh = result >> 64;
    return dividend % divisor;
}
#else
void muls64(uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b);
void mulu64(uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b);
uint64_t divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor);
int64_t divs128(uint64_t *plow, int64_t *phigh, int64_t divisor);

static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
{
    union {
        uint64_t ll;
        struct {
#if HOST_BIG_ENDIAN
            uint32_t high, low;
#else
            uint32_t low, high;
#endif
        } l;
    } u, res;
    uint64_t rl, rh;

    u.ll = a;
    rl = (uint64_t)u.l.low * (uint64_t)b;
    rh = (uint64_t)u.l.high * (uint64_t)b;
    rh += (rl >> 32);
    res.l.high = rh / c;
    res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
    return res.ll;
}
#endif

/**
 * clz32 - count leading zeros in a 32-bit value.
 * @val: The value to search
 *
 * Returns 32 if the value is zero.  Note that the GCC builtin is
 * undefined if the value is zero.
 */
static inline int clz32(uint32_t val)
{
    return val ? __builtin_clz(val) : 32;
}

/**
 * clo32 - count leading ones in a 32-bit value.
 * @val: The value to search
 *
 * Returns 32 if the value is -1.
 */
static inline int clo32(uint32_t val)
{
    return clz32(~val);
}

/**
 * clz64 - count leading zeros in a 64-bit value.
 * @val: The value to search
 *
 * Returns 64 if the value is zero.  Note that the GCC builtin is
 * undefined if the value is zero.
 */
static inline int clz64(uint64_t val)
{
    return val ? __builtin_clzll(val) : 64;
}

/**
 * clo64 - count leading ones in a 64-bit value.
 * @val: The value to search
 *
 * Returns 64 if the value is -1.
 */
static inline int clo64(uint64_t val)
{
    return clz64(~val);
}

/**
 * ctz32 - count trailing zeros in a 32-bit value.
 * @val: The value to search
 *
 * Returns 32 if the value is zero.  Note that the GCC builtin is
 * undefined if the value is zero.
 */
static inline int ctz32(uint32_t val)
{
    return val ? __builtin_ctz(val) : 32;
}

/**
 * cto32 - count trailing ones in a 32-bit value.
 * @val: The value to search
 *
 * Returns 32 if the value is -1.
 */
static inline int cto32(uint32_t val)
{
    return ctz32(~val);
}

/**
 * ctz64 - count trailing zeros in a 64-bit value.
 * @val: The value to search
 *
 * Returns 64 if the value is zero.  Note that the GCC builtin is
 * undefined if the value is zero.
 */
static inline int ctz64(uint64_t val)
{
    return val ? __builtin_ctzll(val) : 64;
}

/**
 * cto64 - count trailing ones in a 64-bit value.
 * @val: The value to search
 *
 * Returns 64 if the value is -1.
 */
static inline int cto64(uint64_t val)
{
    return ctz64(~val);
}

/**
 * clrsb32 - count leading redundant sign bits in a 32-bit value.
 * @val: The value to search
 *
 * Returns the number of bits following the sign bit that are equal to it.
 * No special cases; output range is [0-31].
 */
static inline int clrsb32(uint32_t val)
{
#if __has_builtin(__builtin_clrsb) || !defined(__clang__)
    return __builtin_clrsb(val);
#else
    return clz32(val ^ ((int32_t)val >> 1)) - 1;
#endif
}

/**
 * clrsb64 - count leading redundant sign bits in a 64-bit value.
 * @val: The value to search
 *
 * Returns the number of bits following the sign bit that are equal to it.
 * No special cases; output range is [0-63].
 */
static inline int clrsb64(uint64_t val)
{
#if __has_builtin(__builtin_clrsbll) || !defined(__clang__)
    return __builtin_clrsbll(val);
#else
    return clz64(val ^ ((int64_t)val >> 1)) - 1;
#endif
}

/**
 * ctpop8 - count the population of one bits in an 8-bit value.
 * @val: The value to search
 */
static inline int ctpop8(uint8_t val)
{
    return __builtin_popcount(val);
}

/**
 * ctpop16 - count the population of one bits in a 16-bit value.
 * @val: The value to search
 */
static inline int ctpop16(uint16_t val)
{
    return __builtin_popcount(val);
}

/**
 * ctpop32 - count the population of one bits in a 32-bit value.
 * @val: The value to search
 */
static inline int ctpop32(uint32_t val)
{
    return __builtin_popcount(val);
}

/**
 * ctpop64 - count the population of one bits in a 64-bit value.
 * @val: The value to search
 */
static inline int ctpop64(uint64_t val)
{
    return __builtin_popcountll(val);
}

/**
 * revbit8 - reverse the bits in an 8-bit value.
 * @x: The value to modify.
 */
static inline uint8_t revbit8(uint8_t x)
{
#if __has_builtin(__builtin_bitreverse8)
    return __builtin_bitreverse8(x);
#else
    /* Assign the correct nibble position.  */
    x = ((x & 0xf0) >> 4)
      | ((x & 0x0f) << 4);
    /* Assign the correct bit position.  */
    x = ((x & 0x88) >> 3)
      | ((x & 0x44) >> 1)
      | ((x & 0x22) << 1)
      | ((x & 0x11) << 3);
    return x;
#endif
}

/**
 * revbit16 - reverse the bits in a 16-bit value.
 * @x: The value to modify.
 */
static inline uint16_t revbit16(uint16_t x)
{
#if __has_builtin(__builtin_bitreverse16)
    return __builtin_bitreverse16(x);
#else
    /* Assign the correct byte position.  */
    x = bswap16(x);
    /* Assign the correct nibble position.  */
    x = ((x & 0xf0f0) >> 4)
      | ((x & 0x0f0f) << 4);
    /* Assign the correct bit position.  */
    x = ((x & 0x8888) >> 3)
      | ((x & 0x4444) >> 1)
      | ((x & 0x2222) << 1)
      | ((x & 0x1111) << 3);
    return x;
#endif
}

/**
 * revbit32 - reverse the bits in a 32-bit value.
 * @x: The value to modify.
 */
static inline uint32_t revbit32(uint32_t x)
{
#if __has_builtin(__builtin_bitreverse32)
    return __builtin_bitreverse32(x);
#else
    /* Assign the correct byte position.  */
    x = bswap32(x);
    /* Assign the correct nibble position.  */
    x = ((x & 0xf0f0f0f0u) >> 4)
      | ((x & 0x0f0f0f0fu) << 4);
    /* Assign the correct bit position.  */
    x = ((x & 0x88888888u) >> 3)
      | ((x & 0x44444444u) >> 1)
      | ((x & 0x22222222u) << 1)
      | ((x & 0x11111111u) << 3);
    return x;
#endif
}

/**
 * revbit64 - reverse the bits in a 64-bit value.
 * @x: The value to modify.
 */
static inline uint64_t revbit64(uint64_t x)
{
#if __has_builtin(__builtin_bitreverse64)
    return __builtin_bitreverse64(x);
#else
    /* Assign the correct byte position.  */
    x = bswap64(x);
    /* Assign the correct nibble position.  */
    x = ((x & 0xf0f0f0f0f0f0f0f0ull) >> 4)
      | ((x & 0x0f0f0f0f0f0f0f0full) << 4);
    /* Assign the correct bit position.  */
    x = ((x & 0x8888888888888888ull) >> 3)
      | ((x & 0x4444444444444444ull) >> 1)
      | ((x & 0x2222222222222222ull) << 1)
      | ((x & 0x1111111111111111ull) << 3);
    return x;
#endif
}

/**
 * Return the absolute value of a 64-bit integer as an unsigned 64-bit value
 */
static inline uint64_t uabs64(int64_t v)
{
    return v < 0 ? -v : v;
}

/**
 * sadd32_overflow - addition with overflow indication
 * @x, @y: addends
 * @ret: Output for sum
 *
 * Computes *@ret = @x + @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool sadd32_overflow(int32_t x, int32_t y, int32_t *ret)
{
#if __has_builtin(__builtin_add_overflow) || __GNUC__ >= 5
    return __builtin_add_overflow(x, y, ret);
#else
    *ret = x + y;
    return ((*ret ^ x) & ~(x ^ y)) < 0;
#endif
}

/**
 * sadd64_overflow - addition with overflow indication
 * @x, @y: addends
 * @ret: Output for sum
 *
 * Computes *@ret = @x + @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool sadd64_overflow(int64_t x, int64_t y, int64_t *ret)
{
#if __has_builtin(__builtin_add_overflow) || __GNUC__ >= 5
    return __builtin_add_overflow(x, y, ret);
#else
    *ret = x + y;
    return ((*ret ^ x) & ~(x ^ y)) < 0;
#endif
}

/**
 * uadd32_overflow - addition with overflow indication
 * @x, @y: addends
 * @ret: Output for sum
 *
 * Computes *@ret = @x + @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool uadd32_overflow(uint32_t x, uint32_t y, uint32_t *ret)
{
#if __has_builtin(__builtin_add_overflow) || __GNUC__ >= 5
    return __builtin_add_overflow(x, y, ret);
#else
    *ret = x + y;
    return *ret < x;
#endif
}

/**
 * uadd64_overflow - addition with overflow indication
 * @x, @y: addends
 * @ret: Output for sum
 *
 * Computes *@ret = @x + @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool uadd64_overflow(uint64_t x, uint64_t y, uint64_t *ret)
{
#if __has_builtin(__builtin_add_overflow) || __GNUC__ >= 5
    return __builtin_add_overflow(x, y, ret);
#else
    *ret = x + y;
    return *ret < x;
#endif
}

/**
 * ssub32_overflow - subtraction with overflow indication
 * @x: Minuend
 * @y: Subtrahend
 * @ret: Output for difference
 *
 * Computes *@ret = @x - @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool ssub32_overflow(int32_t x, int32_t y, int32_t *ret)
{
#if __has_builtin(__builtin_sub_overflow) || __GNUC__ >= 5
    return __builtin_sub_overflow(x, y, ret);
#else
    *ret = x - y;
    return ((*ret ^ x) & (x ^ y)) < 0;
#endif
}

/**
 * ssub64_overflow - subtraction with overflow indication
 * @x: Minuend
 * @y: Subtrahend
 * @ret: Output for sum
 *
 * Computes *@ret = @x - @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool ssub64_overflow(int64_t x, int64_t y, int64_t *ret)
{
#if __has_builtin(__builtin_sub_overflow) || __GNUC__ >= 5
    return __builtin_sub_overflow(x, y, ret);
#else
    *ret = x - y;
    return ((*ret ^ x) & (x ^ y)) < 0;
#endif
}

/**
 * usub32_overflow - subtraction with overflow indication
 * @x: Minuend
 * @y: Subtrahend
 * @ret: Output for sum
 *
 * Computes *@ret = @x - @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool usub32_overflow(uint32_t x, uint32_t y, uint32_t *ret)
{
#if __has_builtin(__builtin_sub_overflow) || __GNUC__ >= 5
    return __builtin_sub_overflow(x, y, ret);
#else
    *ret = x - y;
    return x < y;
#endif
}

/**
 * usub64_overflow - subtraction with overflow indication
 * @x: Minuend
 * @y: Subtrahend
 * @ret: Output for sum
 *
 * Computes *@ret = @x - @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool usub64_overflow(uint64_t x, uint64_t y, uint64_t *ret)
{
#if __has_builtin(__builtin_sub_overflow) || __GNUC__ >= 5
    return __builtin_sub_overflow(x, y, ret);
#else
    *ret = x - y;
    return x < y;
#endif
}

/**
 * smul32_overflow - multiplication with overflow indication
 * @x, @y: Input multipliers
 * @ret: Output for product
 *
 * Computes *@ret = @x * @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool smul32_overflow(int32_t x, int32_t y, int32_t *ret)
{
#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
    return __builtin_mul_overflow(x, y, ret);
#else
    int64_t z = (int64_t)x * y;
    *ret = z;
    return *ret != z;
#endif
}

/**
 * smul64_overflow - multiplication with overflow indication
 * @x, @y: Input multipliers
 * @ret: Output for product
 *
 * Computes *@ret = @x * @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool smul64_overflow(int64_t x, int64_t y, int64_t *ret)
{
#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
    return __builtin_mul_overflow(x, y, ret);
#else
    uint64_t hi, lo;
    muls64(&lo, &hi, x, y);
    *ret = lo;
    return hi != ((int64_t)lo >> 63);
#endif
}

/**
 * umul32_overflow - multiplication with overflow indication
 * @x, @y: Input multipliers
 * @ret: Output for product
 *
 * Computes *@ret = @x * @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool umul32_overflow(uint32_t x, uint32_t y, uint32_t *ret)
{
#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
    return __builtin_mul_overflow(x, y, ret);
#else
    uint64_t z = (uint64_t)x * y;
    *ret = z;
    return z > UINT32_MAX;
#endif
}

/**
 * umul64_overflow - multiplication with overflow indication
 * @x, @y: Input multipliers
 * @ret: Output for product
 *
 * Computes *@ret = @x * @y, and returns true if and only if that
 * value has been truncated.
 */
static inline bool umul64_overflow(uint64_t x, uint64_t y, uint64_t *ret)
{
#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
    return __builtin_mul_overflow(x, y, ret);
#else
    uint64_t hi;
    mulu64(ret, &hi, x, y);
    return hi != 0;
#endif
}

/*
 * Unsigned 128x64 multiplication.
 * Returns true if the result got truncated to 128 bits.
 * Otherwise, returns false and the multiplication result via plow and phigh.
 */
static inline bool mulu128(uint64_t *plow, uint64_t *phigh, uint64_t factor)
{
#if defined(CONFIG_INT128) && \
    (__has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5)
    bool res;
    __uint128_t r;
    __uint128_t f = ((__uint128_t)*phigh << 64) | *plow;
    res = __builtin_mul_overflow(f, factor, &r);

    *plow = r;
    *phigh = r >> 64;

    return res;
#else
    uint64_t dhi = *phigh;
    uint64_t dlo = *plow;
    uint64_t ahi;
    uint64_t blo, bhi;

    if (dhi == 0) {
        mulu64(plow, phigh, dlo, factor);
        return false;
    }

    mulu64(plow, &ahi, dlo, factor);
    mulu64(&blo, &bhi, dhi, factor);

    return uadd64_overflow(ahi, blo, phigh) || bhi != 0;
#endif
}

/**
 * uadd64_carry - addition with carry-in and carry-out
 * @x, @y: addends
 * @pcarry: in-out carry value
 *
 * Computes @x + @y + *@pcarry, placing the carry-out back
 * into *@pcarry and returning the 64-bit sum.
 */
static inline uint64_t uadd64_carry(uint64_t x, uint64_t y, bool *pcarry)
{
#if __has_builtin(__builtin_addcll)
    unsigned long long c = *pcarry;
    x = __builtin_addcll(x, y, c, &c);
    *pcarry = c & 1;
    return x;
#else
    bool c = *pcarry;
    /* This is clang's internal expansion of __builtin_addc. */
    c = uadd64_overflow(x, c, &x);
    c |= uadd64_overflow(x, y, &x);
    *pcarry = c;
    return x;
#endif
}

/**
 * usub64_borrow - subtraction with borrow-in and borrow-out
 * @x, @y: addends
 * @pborrow: in-out borrow value
 *
 * Computes @x - @y - *@pborrow, placing the borrow-out back
 * into *@pborrow and returning the 64-bit sum.
 */
static inline uint64_t usub64_borrow(uint64_t x, uint64_t y, bool *pborrow)
{
#if __has_builtin(__builtin_subcll)
    unsigned long long b = *pborrow;
    x = __builtin_subcll(x, y, b, &b);
    *pborrow = b & 1;
    return x;
#else
    bool b = *pborrow;
    b = usub64_overflow(x, b, &x);
    b |= usub64_overflow(x, y, &x);
    *pborrow = b;
    return x;
#endif
}

/* Host type specific sizes of these routines.  */

#if ULONG_MAX == UINT32_MAX
# define clzl   clz32
# define ctzl   ctz32
# define clol   clo32
# define ctol   cto32
# define ctpopl ctpop32
# define revbitl revbit32
#elif ULONG_MAX == UINT64_MAX
# define clzl   clz64
# define ctzl   ctz64
# define clol   clo64
# define ctol   cto64
# define ctpopl ctpop64
# define revbitl revbit64
#else
# error Unknown sizeof long
#endif

static inline bool is_power_of_2(uint64_t value)
{
    if (!value) {
        return false;
    }

    return !(value & (value - 1));
}

/**
 * Return @value rounded down to the nearest power of two or zero.
 */
static inline uint64_t pow2floor(uint64_t value)
{
    if (!value) {
        /* Avoid undefined shift by 64 */
        return 0;
    }
    return 0x8000000000000000ull >> clz64(value);
}

/*
 * Return @value rounded up to the nearest power of two modulo 2^64.
 * This is *zero* for @value > 2^63, so be careful.
 */
static inline uint64_t pow2ceil(uint64_t value)
{
    int n = clz64(value - 1);

    if (!n) {
        /*
         * @value - 1 has no leading zeroes, thus @value - 1 >= 2^63
         * Therefore, either @value == 0 or @value > 2^63.
         * If it's 0, return 1, else return 0.
         */
        return !value;
    }
    return 0x8000000000000000ull >> (n - 1);
}

static inline uint32_t pow2roundup32(uint32_t x)
{
    x |= (x >> 1);
    x |= (x >> 2);
    x |= (x >> 4);
    x |= (x >> 8);
    x |= (x >> 16);
    return x + 1;
}

/**
 * urshift - 128-bit Unsigned Right Shift.
 * @plow: in/out - lower 64-bit integer.
 * @phigh: in/out - higher 64-bit integer.
 * @shift: in - bytes to shift, between 0 and 127.
 *
 * Result is zero-extended and stored in plow/phigh, which are
 * input/output variables. Shift values outside the range will
 * be mod to 128. In other words, the caller is responsible to
 * verify/assert both the shift range and plow/phigh pointers.
 */
void urshift(uint64_t *plow, uint64_t *phigh, int32_t shift);

/**
 * ulshift - 128-bit Unsigned Left Shift.
 * @plow: in/out - lower 64-bit integer.
 * @phigh: in/out - higher 64-bit integer.
 * @shift: in - bytes to shift, between 0 and 127.
 * @overflow: out - true if any 1-bit is shifted out.
 *
 * Result is zero-extended and stored in plow/phigh, which are
 * input/output variables. Shift values outside the range will
 * be mod to 128. In other words, the caller is responsible to
 * verify/assert both the shift range and plow/phigh pointers.
 */
void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow);

/* From the GNU Multi Precision Library - longlong.h __udiv_qrnnd
 * (https://gmplib.org/repo/gmp/file/tip/longlong.h)
 *
 * Licensed under the GPLv2/LGPLv3
 */
static inline uint64_t udiv_qrnnd(uint64_t *r, uint64_t n1,
                                  uint64_t n0, uint64_t d)
{
#if defined(__x86_64__)
    uint64_t q;
    asm("divq %4" : "=a"(q), "=d"(*r) : "0"(n0), "1"(n1), "rm"(d));
    return q;
#elif defined(__s390x__) && !defined(__clang__)
    /* Need to use a TImode type to get an even register pair for DLGR.  */
    unsigned __int128 n = (unsigned __int128)n1 << 64 | n0;
    asm("dlgr %0, %1" : "+r"(n) : "r"(d));
    *r = n >> 64;
    return n;
#elif defined(_ARCH_PPC64) && defined(_ARCH_PWR7)
    /* From Power ISA 2.06, programming note for divdeu.  */
    uint64_t q1, q2, Q, r1, r2, R;
    asm("divdeu %0,%2,%4; divdu %1,%3,%4"
        : "=&r"(q1), "=r"(q2)
        : "r"(n1), "r"(n0), "r"(d));
    r1 = -(q1 * d);         /* low part of (n1<<64) - (q1 * d) */
    r2 = n0 - (q2 * d);
    Q = q1 + q2;
    R = r1 + r2;
    if (R >= d || R < r2) { /* overflow implies R > d */
        Q += 1;
        R -= d;
    }
    *r = R;
    return Q;
#else
    uint64_t d0, d1, q0, q1, r1, r0, m;

    d0 = (uint32_t)d;
    d1 = d >> 32;

    r1 = n1 % d1;
    q1 = n1 / d1;
    m = q1 * d0;
    r1 = (r1 << 32) | (n0 >> 32);
    if (r1 < m) {
        q1 -= 1;
        r1 += d;
        if (r1 >= d) {
            if (r1 < m) {
                q1 -= 1;
                r1 += d;
            }
        }
    }
    r1 -= m;

    r0 = r1 % d1;
    q0 = r1 / d1;
    m = q0 * d0;
    r0 = (r0 << 32) | (uint32_t)n0;
    if (r0 < m) {
        q0 -= 1;
        r0 += d;
        if (r0 >= d) {
            if (r0 < m) {
                q0 -= 1;
                r0 += d;
            }
        }
    }
    r0 -= m;

    *r = r0;
    return (q1 << 32) | q0;
#endif
}

Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor);
#endif