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Move basic_fp to format.h for compile-time formatting

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This commit is contained in:
Victor Zverovich 2022-05-29 07:20:37 -07:00
parent 542785ccbf
commit 2b9037a190
2 changed files with 53 additions and 53 deletions
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57
include/fmt/format-inl.h
View File

@ -197,57 +197,6 @@ template <typename T> constexpr int16_t basic_impl_data<T>::pow10_exponents[];
template <typename T> constexpr uint64_t basic_impl_data<T>::power_of_10_64[];
#endif
// A floating-point number f * pow(2, e) where F is an unsigned type.
template <typename F> struct basic_fp {
F f;
int e;
static constexpr const int num_significand_bits =
static_cast<int>(sizeof(F) * num_bits<unsigned char>());
constexpr basic_fp() : f(0), e(0) {}
constexpr basic_fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
// Constructs fp from an IEEE754 floating-point number.
template <typename Float> FMT_CONSTEXPR basic_fp(Float n) { assign(n); }
// Assigns n to this and return true iff predecessor is closer than successor.
template <typename Float,
FMT_ENABLE_IF(std::numeric_limits<Float>::is_iec559)>
FMT_CONSTEXPR auto assign(Float n) -> bool {
static_assert(std::numeric_limits<Float>::digits <= 113, "unsupported FP");
// Assume Float is in the format [sign][exponent][significand].
using carrier_uint = typename dragonbox::float_info<Float>::carrier_uint;
const auto num_float_significand_bits =
detail::num_significand_bits<Float>();
const auto implicit_bit = carrier_uint(1) << num_float_significand_bits;
const auto significand_mask = implicit_bit - 1;
auto u = bit_cast<carrier_uint>(n);
f = static_cast<F>(u & significand_mask);
auto biased_e = static_cast<int>((u & exponent_mask<Float>()) >>
num_float_significand_bits);
// The predecessor is closer if n is a normalized power of 2 (f == 0)
// other than the smallest normalized number (biased_e > 1).
auto is_predecessor_closer = f == 0 && biased_e > 1;
if (biased_e == 0)
biased_e = 1; // Subnormals use biased exponent 1 (min exponent).
else if (has_implicit_bit<Float>())
f += static_cast<F>(implicit_bit);
e = biased_e - exponent_bias<Float>() - num_float_significand_bits;
if (!has_implicit_bit<Float>()) ++e;
return is_predecessor_closer;
}
template <typename Float,
FMT_ENABLE_IF(!std::numeric_limits<Float>::is_iec559)>
FMT_CONSTEXPR auto assign(Float n) -> bool {
static_assert(std::numeric_limits<double>::is_iec559, "unsupported FP");
return assign(static_cast<double>(n));
}
};
using fp = basic_fp<unsigned long long>;
// Normalizes the value converted from double and multiplied by (1 << SHIFT).
template <int SHIFT = 0, typename F>
FMT_CONSTEXPR basic_fp<F> normalize(basic_fp<F> value) {
@ -259,8 +208,8 @@ FMT_CONSTEXPR basic_fp<F> normalize(basic_fp<F> value) {
--value.e;
}
// Subtract 1 to account for hidden bit.
const auto offset =
fp::num_significand_bits - num_significand_bits<double>() - SHIFT - 1;
const auto offset = basic_fp<F>::num_significand_bits -
num_significand_bits<double>() - SHIFT - 1;
value.f <<= offset;
value.e -= offset;
return value;
@ -288,6 +237,8 @@ FMT_CONSTEXPR inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
#endif
}
using fp = basic_fp<unsigned long long>;
FMT_CONSTEXPR inline fp operator*(fp x, fp y) {
return {multiply(x.f, y.f), x.e + y.e + 64};
}

49
include/fmt/format.h
View File

@ -1361,6 +1361,55 @@ FMT_CONSTEXPR auto write_exponent(int exp, It it) -> It {
return it;
}
// A floating-point number f * pow(2, e) where F is an unsigned type.
template <typename F> struct basic_fp {
F f;
int e;
static constexpr const int num_significand_bits =
static_cast<int>(sizeof(F) * num_bits<unsigned char>());
constexpr basic_fp() : f(0), e(0) {}
constexpr basic_fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
// Constructs fp from an IEEE754 floating-point number.
template <typename Float> FMT_CONSTEXPR basic_fp(Float n) { assign(n); }
// Assigns n to this and return true iff predecessor is closer than successor.
template <typename Float,
FMT_ENABLE_IF(std::numeric_limits<Float>::is_iec559)>
FMT_CONSTEXPR auto assign(Float n) -> bool {
static_assert(std::numeric_limits<Float>::digits <= 113, "unsupported FP");
// Assume Float is in the format [sign][exponent][significand].
using carrier_uint = typename dragonbox::float_info<Float>::carrier_uint;
const auto num_float_significand_bits =
detail::num_significand_bits<Float>();
const auto implicit_bit = carrier_uint(1) << num_float_significand_bits;
const auto significand_mask = implicit_bit - 1;
auto u = bit_cast<carrier_uint>(n);
f = static_cast<F>(u & significand_mask);
auto biased_e = static_cast<int>((u & exponent_mask<Float>()) >>
num_float_significand_bits);
// The predecessor is closer if n is a normalized power of 2 (f == 0)
// other than the smallest normalized number (biased_e > 1).
auto is_predecessor_closer = f == 0 && biased_e > 1;
if (biased_e == 0)
biased_e = 1; // Subnormals use biased exponent 1 (min exponent).
else if (has_implicit_bit<Float>())
f += static_cast<F>(implicit_bit);
e = biased_e - exponent_bias<Float>() - num_float_significand_bits;
if (!has_implicit_bit<Float>()) ++e;
return is_predecessor_closer;
}
template <typename Float,
FMT_ENABLE_IF(!std::numeric_limits<Float>::is_iec559)>
FMT_CONSTEXPR auto assign(Float n) -> bool {
static_assert(std::numeric_limits<double>::is_iec559, "unsupported FP");
return assign(static_cast<double>(n));
}
};
template <typename T>
FMT_HEADER_ONLY_CONSTEXPR20 auto format_float(T value, int precision,
float_specs specs,