47 lines
1.2 KiB
C
47 lines
1.2 KiB
C
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/* 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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#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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enum class ResidualError {
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Zero,
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LessThanHalf,
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Half,
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GreaterThanHalf,
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};
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inline ResidualError ResidualErrorOnRightShift(u64 mantissa, int shift_amount) {
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if (shift_amount <= 0 || mantissa == 0) {
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return ResidualError::Zero;
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}
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if (shift_amount > static_cast<int>(Common::BitSize<u64>())) {
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return Common::MostSignificantBit(mantissa) ? ResidualError::GreaterThanHalf : ResidualError::LessThanHalf;
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}
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const size_t half_bit_position = static_cast<size_t>(shift_amount - 1);
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const u64 half = static_cast<u64>(1) << half_bit_position;
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const u64 error_mask = Common::Ones<u64>(static_cast<size_t>(shift_amount));
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const u64 error = mantissa & error_mask;
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if (error == 0) {
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return ResidualError::Zero;
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}
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if (error < half) {
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return ResidualError::LessThanHalf;
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}
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if (error == half) {
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return ResidualError::Half;
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}
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return ResidualError::GreaterThanHalf;
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}
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} // namespace Dynarmic::FP
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