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add powers_of_ten/max_mantissa for float16_t/bfloat16_t

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This commit is contained in:
Anders Dalvander 2024-12-01 20:03:47 +01:00
parent 6f8fd6728d
commit 8cee025082
1 changed files with 29 additions and 8 deletions
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37
include/fast_float/float_common.h
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@ -713,8 +713,17 @@ inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
// credit: Jakub Jelínek
#ifdef __STDCPP_FLOAT16_T__
template <typename U> struct binary_format_lookup_tables<std::float16_t, U> {
static constexpr std::float16_t powers_of_ten[] = {1}; // todo: fix this
static constexpr uint64_t max_mantissa[] = {1}; // todo: fix this
static constexpr std::float16_t powers_of_ten[] = {1e0f16, 1e1f16, 1e2f16,
1e3f16, 1e4f16};
// Largest integer value v so that (5**index * v) <= 1<<11.
// 0x800 == 1<<11
static constexpr uint64_t max_mantissa[] = {0x800,
0x800 / 5,
0x800 / (5 * 5),
0x800 / (5 * 5 * 5),
0x800 / (5 * 5 * 5 * 5),
0x800 / (constant_55555)};
};
#if FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE
@ -756,18 +765,21 @@ binary_format<std::float16_t>::hidden_bit_mask() {
template <>
inline constexpr int binary_format<std::float16_t>::max_exponent_fast_path() {
return 0;
return 4;
}
template <>
inline constexpr uint64_t
binary_format<std::float16_t>::max_mantissa_fast_path() {
return 0;
return uint64_t(2) << mantissa_explicit_bits();
}
template <>
inline constexpr uint64_t
binary_format<std::float16_t>::max_mantissa_fast_path(int64_t power) {
// caller is responsible to ensure that
// power >= 0 && power <= 4
//
// Work around clang bug https://godbolt.org/z/zedh7rrhc
return (void)max_mantissa[0], max_mantissa[power];
}
@ -823,8 +835,14 @@ template <> constexpr size_t binary_format<std::float16_t>::max_digits() {
// credit: Jakub Jelínek
#ifdef __STDCPP_BFLOAT16_T__
template <typename U> struct binary_format_lookup_tables<std::bfloat16_t, U> {
static constexpr std::bfloat16_t powers_of_ten[] = {1}; // todo: fix this
static constexpr uint64_t max_mantissa[] = {1}; // todo: fix this
static constexpr std::bfloat16_t powers_of_ten[] = {1e0bf16, 1e1bf16, 1e2bf16,
1e3bf16};
// Largest integer value v so that (5**index * v) <= 1<<8.
// 0x100 == 1<<8
static constexpr uint64_t max_mantissa[] = {0x100, 0x100 / 5, 0x100 / (5 * 5),
0x100 / (5 * 5 * 5),
0x100 / (5 * 5 * 5 * 5)};
};
#if FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE
@ -848,7 +866,7 @@ binary_format<std::bfloat16_t>::exact_power_of_ten(int64_t power) {
template <>
inline constexpr int binary_format<std::bfloat16_t>::max_exponent_fast_path() {
return 0;
return 3;
}
template <>
@ -872,12 +890,15 @@ binary_format<std::bfloat16_t>::hidden_bit_mask() {
template <>
inline constexpr uint64_t
binary_format<std::bfloat16_t>::max_mantissa_fast_path() {
return 0;
return uint64_t(2) << mantissa_explicit_bits();
}
template <>
inline constexpr uint64_t
binary_format<std::bfloat16_t>::max_mantissa_fast_path(int64_t power) {
// caller is responsible to ensure that
// power >= 0 && power <= 3
//
// Work around clang bug https://godbolt.org/z/zedh7rrhc
return (void)max_mantissa[0], max_mantissa[power];
}