mirror of
https://github.com/azahar-emu/dynarmic
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101 lines
3.4 KiB
C++
101 lines
3.4 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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#include <tuple>
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#include "common/assert.h"
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#include "common/common_types.h"
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#include "common/fp/fpcr.h"
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#include "common/fp/fpsr.h"
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#include "common/fp/info.h"
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#include "common/fp/op/FPRecipEstimate.h"
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#include "common/fp/process_exception.h"
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#include "common/fp/process_nan.h"
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#include "common/fp/unpacked.h"
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#include "common/math_util.h"
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namespace Dynarmic::FP {
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template<typename FPT>
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FPT FPRecipEstimate(FPT op, FPCR fpcr, FPSR& fpsr) {
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FPType type;
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bool sign;
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FPUnpacked value;
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std::tie(type, sign, value) = FPUnpack<FPT>(op, fpcr, fpsr);
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if (type == FPType::SNaN || type == FPType::QNaN) {
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return FPProcessNaN(type, op, fpcr, fpsr);
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}
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if (type == FPType::Infinity) {
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return FPT(FPInfo<FPT>::Zero(sign));
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}
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if (type == FPType::Zero) {
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FPProcessException(FPExc::DivideByZero, fpcr, fpsr);
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return FPT(FPInfo<FPT>::Infinity(sign));
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}
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if (value.exponent < FPInfo<FPT>::exponent_min - 2) {
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const bool overflow_to_inf = [&]{
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switch (fpcr.RMode()) {
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case RoundingMode::ToNearest_TieEven:
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return true;
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case RoundingMode::TowardsPlusInfinity:
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return !sign;
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case RoundingMode::TowardsMinusInfinity:
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return sign;
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case RoundingMode::TowardsZero:
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return false;
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default:
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UNREACHABLE();
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}
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return false;
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}();
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FPProcessException(FPExc::Overflow, fpcr, fpsr);
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FPProcessException(FPExc::Inexact, fpcr, fpsr);
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return overflow_to_inf ? FPT(FPInfo<FPT>::Infinity(sign)) : FPT(FPInfo<FPT>::MaxNormal(sign));
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}
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if ((fpcr.FZ() && !std::is_same_v<FPT, u16>) || (fpcr.FZ16() && std::is_same_v<FPT, u16>)) {
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if (value.exponent >= -FPInfo<FPT>::exponent_min) {
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fpsr.UFC(true);
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return FPT(FPInfo<FPT>::Zero(sign));
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}
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}
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const u64 scaled = value.mantissa >> (normalized_point_position - 8);
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u64 estimate = static_cast<u64>(Common::RecipEstimate(scaled)) << (FPInfo<FPT>::explicit_mantissa_width - 8);
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int result_exponent = -(value.exponent + 1);
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if (result_exponent < FPInfo<FPT>::exponent_min) {
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switch (result_exponent) {
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case (FPInfo<FPT>::exponent_min - 1):
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estimate |= FPInfo<FPT>::implicit_leading_bit;
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estimate >>= 1;
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break;
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case (FPInfo<FPT>::exponent_min - 2):
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estimate |= FPInfo<FPT>::implicit_leading_bit;
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estimate >>= 2;
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result_exponent++;
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break;
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default:
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UNREACHABLE();
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}
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}
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const FPT bits_sign = FPT(FPInfo<FPT>::Zero(sign));
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const FPT bits_exponent = static_cast<FPT>(result_exponent + FPInfo<FPT>::exponent_bias);
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const FPT bits_mantissa = static_cast<FPT>(estimate);
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return FPT((bits_exponent << FPInfo<FPT>::explicit_mantissa_width) | (bits_mantissa & FPInfo<FPT>::mantissa_mask) | bits_sign);
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}
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template u16 FPRecipEstimate<u16>(u16 op, FPCR fpcr, FPSR& fpsr);
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template u32 FPRecipEstimate<u32>(u32 op, FPCR fpcr, FPSR& fpsr);
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template u64 FPRecipEstimate<u64>(u64 op, FPCR fpcr, FPSR& fpsr);
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} // namespace Dynarmic::FP
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