intx/test/experimental/add.cpp

// intx: extended precision integer library.
// Copyright 2019 Pawel Bylica.
// Licensed under the Apache License, Version 2.0.

/// @file
/// In this file we have 256-bit add procedures to inspect how good are
/// compilers at optimizing these.

#if INTX_EXPERIMENTAL
    #include "add.hpp"
#else
    #include <cstdint>

struct uint128
{
    uint64_t lo;
    uint64_t hi;
};

struct uint256
{
    uint128 lo;
    uint128 hi;
};
#endif

struct uint192
{
    uint64_t lo;
    uint64_t mi;
    uint64_t hi;
};

namespace intx::experimental
{
#ifndef INTX_EXPERIMENTAL
bool uaddo(uint64_t al, uint64_t ah, uint64_t bl, uint64_t bh, uint128* res) noexcept
{
    const auto ll = al + bl;
    auto carry = ll < al;

    auto s = ah + bh;
    auto k1 = s < ah;
    auto lh = s + carry;
    auto k2 = lh < s;
    carry = k1 | k2;

    *res = uint128{lh, ll};
    return carry;
}

uint192 add_waterfall(
    uint64_t all, uint64_t alh, uint64_t ahl, uint64_t bll, uint64_t blh, uint64_t bhl) noexcept
{
    const auto ll = all + bll;
    auto carry = ll < all;

    auto s = alh + blh;
    auto k1 = s < alh;
    auto lh = s + carry;
    auto k2 = lh < s;
    carry = k1 | k2;

    auto hl = ahl + bhl + carry;

    return {hl, lh, ll};
}
#endif
}  // namespace intx::experimental