109 lines
2.2 KiB
C++
109 lines
2.2 KiB
C++
#include "stdafx.h"
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#include "AluMulDiv.h"
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#include "Cpu.h"
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#include "../Utilities/Serializer.h"
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void AluMulDiv::Initialize(Cpu* cpu)
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{
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_cpu = cpu;
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}
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void AluMulDiv::Run(bool isRead)
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{
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uint64_t cpuCycle = _cpu->GetCycleCount();
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if(isRead) {
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//Run 1 cycle less for read operations, since they occur earlier within the CPU cycle, compared to a write
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cpuCycle--;
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}
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if(_multCounter != 0 || _divCounter != 0) {
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uint64_t cyclesToRun = cpuCycle - _prevCpuCycle;
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while(cyclesToRun--) {
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if(!_multCounter && !_divCounter) {
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break;
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}
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if(_multCounter > 0) {
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_multCounter--;
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if(_divResult & 0x01) {
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_multOrRemainderResult += _shift;
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}
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_shift <<= 1;
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_divResult >>= 1;
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}
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if(_divCounter > 0) {
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_divCounter--;
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_shift >>= 1;
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_divResult <<= 1;
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if(_multOrRemainderResult >= _shift) {
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_multOrRemainderResult -= _shift;
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_divResult |= 1;
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}
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}
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}
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}
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_prevCpuCycle = cpuCycle;
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}
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uint8_t AluMulDiv::Read(uint16_t addr)
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{
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Run(true);
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switch(addr) {
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case 0x4214: return (uint8_t)_divResult;
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case 0x4215: return (uint8_t)(_divResult >> 8);
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case 0x4216: return (uint8_t)_multOrRemainderResult;
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case 0x4217: return (uint8_t)(_multOrRemainderResult >> 8);
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}
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throw std::runtime_error("ALU: invalid address");
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}
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void AluMulDiv::Write(uint16_t addr, uint8_t value)
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{
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Run(false);
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switch(addr) {
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case 0x4202: _multOperand1 = value; break;
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case 0x4203:
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_multOrRemainderResult = 0;
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if(!_divCounter && !_multCounter) {
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_multCounter = 8;
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_multOperand2 = value;
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_divResult = (value << 8) | _multOperand1;
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_shift = value;
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}
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break;
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case 0x4204: _dividend = (_dividend & 0xFF00) | value; break;
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case 0x4205: _dividend = (_dividend & 0xFF) | (value << 8); break;
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case 0x4206:
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_multOrRemainderResult = _dividend;
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if(!_divCounter && !_multCounter) {
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_divCounter = 16;
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_divisor = value;
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_shift = (value << 16);
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}
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break;
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default: throw std::runtime_error("ALU: invalid address");
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}
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}
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void AluMulDiv::Serialize(Serializer &s)
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{
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s.Stream(
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_multOperand1, _multOperand2, _multOrRemainderResult, _dividend, _divisor, _divResult,
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_divCounter, _multCounter, _shift, _prevCpuCycle
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);
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}
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