mirror of
https://github.com/azahar-emu/dynarmic
synced 2025-11-07 23:50:00 +01:00
c9777ef997
While initially done to potentially prevent creating bugs due to C++ having a silly type-promotion mechanism involving types < sizeof(int) and unsignedness, given that the bulk of these functions' usages are on exit paths, these can return the correct type to avoid the need to cast at every usage point.
118 lines
4.6 KiB
C++
118 lines
4.6 KiB
C++
/* This file is part of the dynarmic project.
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* Copyright (c) 2018 MerryMage
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* This software may be used and distributed according to the terms of the GNU
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* General Public License version 2 or any later version.
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*/
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#pragma once
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#include "common/bit_util.h"
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#include "common/common_types.h"
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namespace Dynarmic::FP {
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template<typename FPT>
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struct FPInfo {};
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template<>
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struct FPInfo<u16> {
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static constexpr size_t total_width = 16;
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static constexpr size_t exponent_width = 5;
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static constexpr size_t explicit_mantissa_width = 10;
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static constexpr size_t mantissa_width = explicit_mantissa_width + 1;
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static constexpr u32 implicit_leading_bit = u32(1) << explicit_mantissa_width;
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static constexpr u32 sign_mask = 0x8000;
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static constexpr u32 exponent_mask = 0x7C00;
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static constexpr u32 mantissa_mask = 0x3FF;
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static constexpr u32 mantissa_msb = 0x200;
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static constexpr int exponent_min = -14;
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static constexpr int exponent_max = 15;
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static constexpr int exponent_bias = 15;
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static constexpr u16 Zero(bool sign) {
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return sign ? static_cast<u16>(sign_mask) : u16{0};
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}
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static constexpr u16 Infinity(bool sign) {
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return static_cast<u16>(exponent_mask | Zero(sign));
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}
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static constexpr u16 MaxNormal(bool sign) {
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return static_cast<u16>((exponent_mask - 1) | Zero(sign));
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}
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static constexpr u16 DefaultNaN() {
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return static_cast<u16>(exponent_mask | (u32(1) << (explicit_mantissa_width - 1)));
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}
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};
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template<>
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struct FPInfo<u32> {
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static constexpr size_t total_width = 32;
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static constexpr size_t exponent_width = 8;
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static constexpr size_t explicit_mantissa_width = 23;
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static constexpr size_t mantissa_width = explicit_mantissa_width + 1;
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static constexpr u32 implicit_leading_bit = u32(1) << explicit_mantissa_width;
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static constexpr u32 sign_mask = 0x80000000;
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static constexpr u32 exponent_mask = 0x7F800000;
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static constexpr u32 mantissa_mask = 0x007FFFFF;
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static constexpr u32 mantissa_msb = 0x00400000;
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static constexpr int exponent_min = -126;
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static constexpr int exponent_max = 127;
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static constexpr int exponent_bias = 127;
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static constexpr u32 Zero(bool sign) { return sign ? sign_mask : 0; }
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static constexpr u32 Infinity(bool sign) { return exponent_mask | Zero(sign); }
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static constexpr u32 MaxNormal(bool sign) { return (exponent_mask - 1) | Zero(sign); }
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static constexpr u32 DefaultNaN() { return exponent_mask | (u32(1) << (explicit_mantissa_width - 1)); }
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};
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template<>
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struct FPInfo<u64> {
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static constexpr size_t total_width = 64;
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static constexpr size_t exponent_width = 11;
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static constexpr size_t explicit_mantissa_width = 52;
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static constexpr size_t mantissa_width = explicit_mantissa_width + 1;
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static constexpr u64 implicit_leading_bit = u64(1) << explicit_mantissa_width;
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static constexpr u64 sign_mask = 0x8000'0000'0000'0000;
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static constexpr u64 exponent_mask = 0x7FF0'0000'0000'0000;
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static constexpr u64 mantissa_mask = 0x000F'FFFF'FFFF'FFFF;
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static constexpr u64 mantissa_msb = 0x0008'0000'0000'0000;
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static constexpr int exponent_min = -1022;
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static constexpr int exponent_max = 1023;
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static constexpr int exponent_bias = 1023;
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static constexpr u64 Zero(bool sign) { return sign ? sign_mask : 0; }
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static constexpr u64 Infinity(bool sign) { return exponent_mask | Zero(sign); }
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static constexpr u64 MaxNormal(bool sign) { return (exponent_mask - 1) | Zero(sign); }
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static constexpr u64 DefaultNaN() { return exponent_mask | (u64(1) << (explicit_mantissa_width - 1)); }
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};
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/// value = (sign ? -1 : +1) * 2^exponent * value
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/// @note We do not handle denormals. Denormals will static_assert.
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template<typename FPT, bool sign, int exponent, FPT value>
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constexpr FPT FPValue() {
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if constexpr (value == 0) {
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return FPInfo<FPT>::Zero(sign);
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}
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constexpr int point_position = static_cast<int>(FPInfo<FPT>::explicit_mantissa_width);
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constexpr int highest_bit = Common::HighestSetBit(value);
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constexpr int offset = point_position - highest_bit;
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constexpr int normalized_exponent = exponent - offset + point_position;
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static_assert(offset >= 0);
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static_assert(normalized_exponent >= FPInfo<FPT>::exponent_min && normalized_exponent <= FPInfo<FPT>::exponent_max);
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constexpr FPT mantissa = (value << offset) & FPInfo<FPT>::mantissa_mask;
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constexpr FPT biased_exponent = static_cast<FPT>(normalized_exponent + FPInfo<FPT>::exponent_bias);
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return FPT(FPInfo<FPT>::Zero(sign) | mantissa | (biased_exponent << FPInfo<FPT>::explicit_mantissa_width));
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}
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} // namespace Dynarmic::FP
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