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Improve __float128 support

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Victor Zverovich 2022-03-19 09:33:40 -07:00
parent 71778e8b90
commit 3f9b7433a3
2 changed files with 13 additions and 6 deletions
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8
include/fmt/format-inl.h
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@ -217,8 +217,10 @@ template <typename F> struct basic_fp {
template <typename Float> FMT_CONSTEXPR basic_fp(Float n) { assign(n); } template <typename Float> FMT_CONSTEXPR basic_fp(Float n) { assign(n); }
template <typename Float> template <typename Float>
using is_supported = bool_constant<std::numeric_limits<Float>::is_iec559 && using is_supported =
std::numeric_limits<Float>::digits <= 113>; bool_constant<(std::numeric_limits<Float>::is_iec559 &&
std::numeric_limits<Float>::digits <= 113) ||
is_float128<Float>::value>;
// Assigns d to this and return true iff predecessor is closer than successor. // Assigns d to this and return true iff predecessor is closer than successor.
template <typename Float, FMT_ENABLE_IF(is_supported<Float>::value)> template <typename Float, FMT_ENABLE_IF(is_supported<Float>::value)>
@ -229,7 +231,7 @@ template <typename F> struct basic_fp {
<< detail::num_significand_bits<Float>(); << detail::num_significand_bits<Float>();
const carrier_uint significand_mask = implicit_bit - 1; const carrier_uint significand_mask = implicit_bit - 1;
auto u = bit_cast<carrier_uint>(n); auto u = bit_cast<carrier_uint>(n);
f = static_cast<uint64_t>(u & significand_mask); f = static_cast<F>(u & significand_mask);
int biased_e = static_cast<int>((u & exponent_mask<Float>()) >> int biased_e = static_cast<int>((u & exponent_mask<Float>()) >>
detail::num_significand_bits<Float>()); detail::num_significand_bits<Float>());
// The predecessor is closer if n is a normalized power of 2 (f == 0) other // The predecessor is closer if n is a normalized power of 2 (f == 0) other

11
include/fmt/format.h
View File

@ -1286,14 +1286,19 @@ template <typename T> struct decimal_fp {
template <typename T> FMT_API auto to_decimal(T x) noexcept -> decimal_fp<T>; template <typename T> FMT_API auto to_decimal(T x) noexcept -> decimal_fp<T>;
} // namespace dragonbox } // namespace dragonbox
// Returns true iff Float has the implicit bit which is not stored.
template <typename Float> constexpr bool has_implicit_bit() { template <typename Float> constexpr bool has_implicit_bit() {
// An 80-bit FP number has a 64-bit significand an no implicit bit.
return std::numeric_limits<Float>::digits != 64; return std::numeric_limits<Float>::digits != 64;
} }
// Returns the number of significand bits in Float excluding the implicit bit. // Returns the number of significand bits stored in Float. The implicit bit is
// not counted since it is not stored.
template <typename Float> constexpr int num_significand_bits() { template <typename Float> constexpr int num_significand_bits() {
return std::numeric_limits<Float>::digits - // std::numeric_limits may not support __float128.
(has_implicit_bit<Float>() ? 1 : 0); return is_float128<Float>() ? 112
: (std::numeric_limits<Float>::digits -
(has_implicit_bit<Float>() ? 1 : 0));
} }
template <typename Float> template <typename Float>