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Minimize the usage of built-in 128-bit ints

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It usually generates slower code than manual handling.
This commit is contained in:
Junekey Jeon 2022-01-12 15:00:44 -08:00 committed by Victor Zverovich
parent cdf1a3b530
commit 70561ed13e
1 changed files with 23 additions and 34 deletions
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57
include/fmt/format-inl.h
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@ -789,48 +789,36 @@ FMT_INLINE FMT_CONSTEXPR20 digits::result grisu_gen_digits(
struct uint128_wrapper {
uint128_wrapper() = default;
#if FMT_USE_INT128
uint128_t internal_;
constexpr uint128_wrapper(uint64_t high, uint64_t low) FMT_NOEXCEPT
: internal_{static_cast<uint128_t>(low) |
(static_cast<uint128_t>(high) << 64)} {}
constexpr uint128_wrapper(uint128_t u) : internal_{u} {}
constexpr uint64_t high() const FMT_NOEXCEPT {
return uint64_t(internal_ >> 64);
}
constexpr uint64_t low() const FMT_NOEXCEPT { return uint64_t(internal_); }
uint128_wrapper& operator+=(uint64_t n) FMT_NOEXCEPT {
internal_ += n;
return *this;
}
#else
uint64_t high_;
uint64_t low_;
constexpr uint128_wrapper(uint64_t high, uint64_t low) FMT_NOEXCEPT
: high_{high},
low_{low} {}
constexpr uint128_wrapper(uint64_t high, uint64_t low) noexcept
: high_{high}, low_{low} {}
constexpr uint64_t high() const FMT_NOEXCEPT { return high_; }
constexpr uint64_t low() const FMT_NOEXCEPT { return low_; }
constexpr uint64_t high() const noexcept { return high_; }
constexpr uint64_t low() const noexcept { return low_; }
uint128_wrapper& operator+=(uint64_t n) FMT_NOEXCEPT {
# if defined(_MSC_VER) && defined(_M_X64)
unsigned char carry = _addcarry_u64(0, low_, n, &low_);
uint128_wrapper& operator+=(uint64_t n) & noexcept {
#if FMT_HAS_BUILTIN(__builtin_addcll)
unsigned long long carry;
low_ = __builtin_addcll(low_, n, 0, &carry);
high_ = __builtin_addcll(high_, 0, carry, &carry);
#elif FMT_HAS_BUILTIN(__builtin_ia32_addcarryx_u64)
unsigned long long result;
auto carry = __builtin_ia32_addcarryx_u64(0, low_, n, &result);
low_ = result;
__builtin_ia32_addcarryx_u64(carry, high_, 0, &result);
high_ = result;
#elif defined(_MSC_VER) && defined(_M_X64)
auto carry = _addcarry_u64(0, low_, n, &low_);
_addcarry_u64(carry, high_, 0, &high_);
return *this;
# else
uint64_t sum = low_ + n;
#else
auto sum = low_ + n;
high_ += (sum < low_ ? 1 : 0);
low_ = sum;
return *this;
# endif
}
#endif
return *this;
}
};
// Implementation of Dragonbox algorithm: https://github.com/jk-jeon/dragonbox.
@ -838,7 +826,8 @@ namespace dragonbox {
// Computes 128-bit result of multiplication of two 64-bit unsigned integers.
inline uint128_wrapper umul128(uint64_t x, uint64_t y) FMT_NOEXCEPT {
#if FMT_USE_INT128
return static_cast<uint128_t>(x) * static_cast<uint128_t>(y);
auto p = static_cast<uint128_t>(x) * static_cast<uint128_t>(y);
return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)};
#elif defined(_MSC_VER) && defined(_M_X64)
uint128_wrapper result;
result.low_ = _umul128(x, y, &result.high_);