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58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
/* This file is part of the dynarmic project.
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* Copyright (c) 2018 MerryMage
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* SPDX-License-Identifier: 0BSD
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*/
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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/FPRSqrtEstimate.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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#include "common/safe_ops.h"
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namespace Dynarmic::FP {
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template<typename FPT>
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FPT FPRSqrtEstimate(FPT op, FPCR fpcr, FPSR& fpsr) {
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const auto [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::Zero) {
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FPProcessException(FPExc::DivideByZero, fpcr, fpsr);
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return FPInfo<FPT>::Infinity(sign);
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}
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if (sign) {
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FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
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return FPInfo<FPT>::DefaultNaN();
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}
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if (type == FPType::Infinity) {
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// Note: Just +Inf reaches here, negatives are handled in the case above.
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return FPInfo<FPT>::Zero(false);
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}
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const int result_exponent = (-(value.exponent + 1)) >> 1;
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const bool was_exponent_odd = (value.exponent) % 2 == 0;
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const u64 scaled = Safe::LogicalShiftRight(value.mantissa, normalized_point_position - (was_exponent_odd ? 7 : 8));
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const u64 estimate = Common::RecipSqrtEstimate(scaled);
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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 << (FPInfo<FPT>::explicit_mantissa_width - 8));
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return (bits_exponent << FPInfo<FPT>::explicit_mantissa_width) | (bits_mantissa & FPInfo<FPT>::mantissa_mask);
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}
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template u16 FPRSqrtEstimate<u16>(u16 op, FPCR fpcr, FPSR& fpsr);
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template u32 FPRSqrtEstimate<u32>(u32 op, FPCR fpcr, FPSR& fpsr);
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template u64 FPRSqrtEstimate<u64>(u64 op, FPCR fpcr, FPSR& fpsr);
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} // namespace Dynarmic::FP
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