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instructions.cpp
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instructions.cpp
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#include "instructions.h"
#include "log.h"
#include "utils.h"
#include <bits/stdint-uintn.h>
#include <memory>
#define DECODE(X) \
if (!instr) \
instr = X::decode(opcode)
Halt::Halt() { finished = true; }
std::unique_ptr<Instruction> Halt::decode(uint8_t opcode) {
if (opcode == 0b01110110)
return std::make_unique<Halt>();
return nullptr;
}
bool Halt::execute(CPU *cpu) {
cpu->setHalted();
return true;
}
std::string Halt::getName() { return "Halt"; }
int Halt::getType() { return instruction::HALT; }
DAA::DAA() { finished = true; }
std::unique_ptr<Instruction> DAA::decode(uint8_t opcode) {
if (opcode == 0b00100111)
return std::make_unique<DAA>();
return nullptr;
}
bool DAA::execute(CPU *cpu) {
uint8_t &flags = cpu->getRegisters().f;
uint8_t correction = 0;
uint8_t daa = cpu->getRegisters().a;
bool shouldSetCarry = false;
if (flags & (1 << 5) || (!(flags & (1 << 6)) && (daa & 0xF) > 9)) {
correction |= 0x6;
}
if ((flags & (1 << 4)) || (!(flags & (1 << 6)) && daa > 0x99)) {
correction |= 0x60;
shouldSetCarry = true;
}
daa += (flags & (1 << 6)) ? -correction : correction;
daa &= 0xFF;
flags &= 0b01001111;
if (shouldSetCarry)
flags |= 1 << 4;
if (daa == 0)
flags |= 1 << 7;
cpu->getRegisters().a = daa;
return true;
}
std::string DAA::getName() { return "DAA"; }
int DAA::getType() { return instruction::DAA; }
Complement::Complement() { finished = true; }
std::unique_ptr<Instruction> Complement::decode(uint8_t opcode) {
if (opcode == 0b00101111)
return std::make_unique<Complement>();
return nullptr;
}
bool Complement::execute(CPU *cpu) {
cpu->getRegisters().a = ~cpu->getRegisters().a;
cpu->getRegisters().f |= 0b01100000;
return true;
}
std::string Complement::getName() { return "Complement"; }
int Complement::getType() { return instruction::CPL; }
SetClearCarryFlag::SetClearCarryFlag(bool shouldSet) : shouldSet(shouldSet) {
finished = true;
}
std::unique_ptr<Instruction> SetClearCarryFlag::decode(uint8_t opcode) {
if (opcode == 0b00110111)
return std::make_unique<SetClearCarryFlag>(true);
if (opcode == 0b00111111)
return std::make_unique<SetClearCarryFlag>(false);
return nullptr;
}
bool SetClearCarryFlag::execute(CPU *cpu) {
uint8_t &flags = cpu->getRegisters().f;
flags &= 0b10011111;
if (shouldSet) {
flags |= 1 << 4;
} else {
if (flags & (1 << 4)) {
flags &= 0b10001111;
} else {
flags |= 1 << 4;
}
}
return true;
}
std::string SetClearCarryFlag::getName() {
return shouldSet ? "Set Carry" : "Clear Carry";
}
int SetClearCarryFlag::getType() { return instruction::SetClearCarryFlag; }
SpecialAdd::SpecialAdd(uint8_t reg) : reg(reg), immediate(0), wastedCycles(0) {
finished = reg != 0xFF;
}
void SpecialAdd::amend(uint8_t val) {
immediate = val;
finished = true;
}
std::unique_ptr<Instruction> SpecialAdd::decode(uint8_t opcode) {
if (((opcode >> 6) & 0x3) == 0b00 && (opcode & 0xF) == 0b1001)
return std::make_unique<SpecialAdd>((opcode >> 4) & 0x3);
if (opcode == 0b11101000)
return std::make_unique<SpecialAdd>(0xFF);
return nullptr;
}
bool SpecialAdd::execute(CPU *cpu) {
uint8_t &flags = cpu->getRegisters().f;
if (reg != 0xFF) {
if (wastedCycles != 1) {
wastedCycles++;
return false;
}
uint16_t *registerMapping[]{
&cpu->getRegisters().bc, &cpu->getRegisters().de,
&cpu->getRegisters().hl, &cpu->getRegisters().sp};
flags &= 0b10001111;
if (((uint32_t)cpu->getRegisters().hl) +
((uint32_t)(*(registerMapping[reg]))) >
0xFFFF)
flags |= 1 << 4;
if ((cpu->getRegisters().hl & 0x0FFF) + (*(registerMapping[reg]) & 0x0FFF) >
0x0FFF)
flags |= 1 << 5;
cpu->getRegisters().hl += *(registerMapping[reg]);
} else {
if (wastedCycles != 2) {
wastedCycles++;
return false;
}
int8_t relativeAddress = immediate;
flags &= 0b00001111;
if ((cpu->getRegisters().sp ^ relativeAddress ^
(cpu->getRegisters().sp + relativeAddress)) &
0x100)
flags |= 1 << 4;
if ((cpu->getRegisters().sp ^ relativeAddress ^
(cpu->getRegisters().sp + relativeAddress)) &
0x10)
flags |= 1 << 5;
cpu->getRegisters().sp += relativeAddress;
}
return true;
}
std::string SpecialAdd::getName() { return "Special Add"; }
int SpecialAdd::getType() { return instruction::SpecialAdd; }
EnableDisableInterrupts::EnableDisableInterrupts(bool enable) : enable(enable) {
finished = true;
}
std::unique_ptr<Instruction> EnableDisableInterrupts::decode(uint8_t opcode) {
if (opcode == 0b11110011)
return std::make_unique<EnableDisableInterrupts>(false);
if (opcode == 0b11111011)
return std::make_unique<EnableDisableInterrupts>(true);
return nullptr;
}
bool EnableDisableInterrupts::execute(CPU *cpu) {
cpu->setInterruptEnable(enable);
return true;
}
std::string EnableDisableInterrupts::getName() { return enable ? "EI" : "DI"; }
int EnableDisableInterrupts::getType() {
return instruction::EnableDisableInterrupts;
}
Ret::Ret(Condition condition, bool enableInterrupts)
: condition(condition), enableInterrupts(enableInterrupts), currentByte(0) {
finished = true;
}
std::unique_ptr<Instruction> Ret::decode(uint8_t opcode) {
Condition conditions[] = {Condition::NotZero, Condition::Zero,
Condition::NotCarry, Condition::Carry};
if (((opcode >> 5) & 0x7) == 0b110 && (opcode & 0x7) == 0b000)
return std::make_unique<Ret>(conditions[(opcode >> 3) & 0x3], false);
if (opcode == 0b11001001)
return std::make_unique<Ret>(Condition::Unconditional, false);
if (opcode == 0b11011001)
return std::make_unique<Ret>(Condition::Unconditional, true);
return nullptr;
}
bool Ret::execute(CPU *cpu) {
uint8_t flags = cpu->getRegisters().f;
if (condition != Condition::Unconditional) {
if (!wastedCycle) {
wastedCycle = true;
return false;
}
if (!checkedCondition) {
if (condition == Condition::NotZero &&
(flags & (1 << 7)) != 0) // Not Zero
return true;
if (condition == Condition::Zero && (flags & (1 << 7)) == 0) // Zero
return true;
if (condition == Condition::NotCarry &&
(flags & (1 << 4)) != 0) // Not Carry
return true;
if (condition == Condition::Carry && (flags & (1 << 4)) == 0) // Carry
return true;
checkedCondition = true;
return false;
}
}
if (currentByte != 2) {
address = (address >> 8) | (cpu->read(cpu->getRegisters().sp) << 8);
cpu->getRegisters().sp += 1;
currentByte++;
return false;
}
cpu->getRegisters().pc = address;
if (enableInterrupts)
cpu->setInterruptEnable(true);
return true;
}
std::string Ret::getName() {
return enableInterrupts
? "Reti"
: (condition == Condition::Unconditional ? "Ret" : "Ret F");
}
int Ret::getType() { return instruction::Ret; }
RotateA::RotateA(bool isLeft, bool throughCarry)
: isLeft(isLeft), throughCarry(throughCarry) {
finished = true;
}
std::unique_ptr<Instruction> RotateA::decode(uint8_t opcode) {
if (((opcode >> 5) & 0x7) == 0b000 && (opcode & 0x7) == 0b111)
return std::make_unique<RotateA>(((opcode >> 3) & 0x1) == 0,
(opcode >> 4) & 0x1);
return nullptr;
}
bool RotateA::execute(CPU *cpu) {
uint8_t &result = cpu->getRegisters().a;
uint8_t &flags = cpu->getRegisters().f;
if (throughCarry) {
if (isLeft) {
LOG("Rotate A left\n");
bool carrySet = (flags & (1 << 4)) == (1 << 4);
flags &= 0b00001111;
if (result & 0x80)
flags |= 1 << 4;
result = result << 1;
if (carrySet)
result |= 1;
} else {
LOG("Rotate A right\n");
bool carrySet = (flags & (1 << 4)) == (1 << 4);
flags &= 0b00001111;
if (result & 0x1)
flags |= 1 << 4;
result = result >> 1;
if (carrySet)
result |= 0x80;
}
} else {
if (isLeft) {
LOG("Rotate A left (without carry)\n");
flags &= 0b00001111;
bool carrySet = (result & 0x80) == 0x80;
if (carrySet)
flags |= 1 << 4;
result = result << 1;
if (carrySet)
result |= 1;
} else {
LOG("Rotate A right (without carry)\n");
flags &= 0b00001111;
bool carrySet = (result & 0x1) == 0x1;
if (carrySet)
flags |= 1 << 4;
result = result >> 1;
if (carrySet)
result |= 0x80;
}
}
return true;
}
std::string RotateA::getName() { return throughCarry ? "RdA" : "RdCA"; }
int RotateA::getType() { return instruction::RotateA; }
PopPush::PopPush(uint8_t reg, bool isPop)
: reg(reg), isPop(isPop), currentByte(0), hasWastedCycle(isPop) {
finished = true;
}
std::unique_ptr<Instruction> PopPush::decode(uint8_t opcode) {
if (((opcode >> 6) & 0x3) == 0b11 && ((opcode >> 3) & 1) == 0b0 &&
(opcode & 0x3) == 0b01)
return std::make_unique<PopPush>((opcode >> 4) & 0x3,
((opcode >> 2) & 1) == 0);
return nullptr;
}
bool PopPush::execute(CPU *cpu) {
uint16_t *registerMapping[]{&cpu->getRegisters().bc, &cpu->getRegisters().de,
&cpu->getRegisters().hl, &cpu->getRegisters().af};
std::string registerNames[2][4] = {{"C", "E", "L", "F"},
{"B", "D", "H", "A"}};
if (!hasWastedCycle) {
hasWastedCycle = true;
return false;
}
if (isPop) {
((uint8_t *)registerMapping[reg])[currentByte] =
cpu->read(cpu->getRegisters().sp);
LOG("POP %s (%02X from %04X)\n", registerNames[currentByte][reg].c_str(),
((uint8_t *)registerMapping[reg])[currentByte], cpu->getRegisters().sp);
cpu->getRegisters().sp++;
cpu->getRegisters().f &= 0b11110000;
} else {
cpu->getRegisters().sp--;
cpu->write(cpu->getRegisters().sp,
((uint8_t *)registerMapping[reg])[1 - currentByte]);
LOG("PUSH %s (%02X to %04X)\n", registerNames[1 - currentByte][reg].c_str(),
((uint8_t *)registerMapping[reg])[1 - currentByte],
cpu->getRegisters().sp);
}
currentByte++;
if (currentByte != 2)
return false;
return true;
}
std::string PopPush::getName() { return isPop ? "Pop" : "Push"; }
int PopPush::getType() { return instruction::PopPush; }
Call::Call(Condition condition)
: needsBytes(2), address(0), condition(condition), storedPCCount(0),
movedSP(false) {
finished = false;
}
std::unique_ptr<Instruction> Call::decode(uint8_t opcode) {
Condition conditions[] = {Condition::NotZero, Condition::Zero,
Condition::NotCarry, Condition::Carry};
if (((opcode >> 5) & 0x7) == 0b110 && (opcode & 0x7) == 0b100)
return std::make_unique<Call>(conditions[(opcode >> 3) & 0x3]);
if (opcode == 0b11001101)
return std::make_unique<Call>(Condition::Unconditional);
return nullptr;
}
void Call::amend(uint8_t val) {
needsBytes--;
address = (address >> 8) | (val << 8);
finished = needsBytes == 0;
}
bool Call::execute(CPU *cpu) {
uint8_t flags = cpu->getRegisters().f;
if (condition == Condition::NotZero && (flags & (1 << 7)) != 0) // Not Zero
return true;
if (condition == Condition::Zero && (flags & (1 << 7)) == 0) // Zero
return true;
if (condition == Condition::NotCarry && (flags & (1 << 4)) != 0) // Not Carry
return true;
if (condition == Condition::Carry && (flags & (1 << 4)) == 0) // Carry
return true;
if (storedPCCount != 2) {
cpu->write(cpu->getRegisters().sp - storedPCCount - 1,
(cpu->getRegisters().pc >> (8 * (1 - storedPCCount))) & 0xFF);
LOG("WROTE %02X to %04X\n",
(cpu->getRegisters().pc >> (8 * (1 - storedPCCount))) & 0xFF,
cpu->getRegisters().sp - storedPCCount - 1);
storedPCCount++;
if (storedPCCount != 2)
return false;
}
if (!movedSP) {
cpu->getRegisters().sp -= 2;
movedSP = true;
return false;
}
cpu->getRegisters().pc = address;
LOG("Call jump to %04X\n", address);
return true;
}
std::string Call::getName() { return "Call"; }
int Call::getType() { return instruction::Call; }
IncDec::IncDec(bool increment, uint8_t destination, bool isBigRegister)
: increment(increment), destination(destination),
isBigRegister(isBigRegister) {
finished = true;
address = 0;
gotAddress = false;
storedValue = 0;
retrievedStoredValue = false;
}
std::unique_ptr<Instruction> IncDec::decode(uint8_t opcode) {
if ((opcode >> 6) == 0b00 && (opcode & 0x7) == 0b011)
return std::make_unique<IncDec>(((opcode >> 3) & 1) == 0,
(opcode >> 4) & 0x3, true);
if ((opcode >> 6) == 0b00 && ((opcode >> 1) & 0x3) == 0b10)
return std::make_unique<IncDec>((opcode & 1) == 0, (opcode >> 3) & 0x7,
false);
return nullptr;
}
bool IncDec::execute(CPU *cpu) {
uint8_t &flags = cpu->getRegisters().f;
if (isBigRegister) {
uint16_t *registerMapping[]{
&cpu->getRegisters().bc, &cpu->getRegisters().de,
&cpu->getRegisters().hl, &cpu->getRegisters().sp};
uint16_t *dest = registerMapping[destination];
if (increment)
*dest = *dest + 1;
else
*dest = *dest - 1;
} else {
uint8_t *registerMapping[] = {&cpu->getRegisters().b,
&cpu->getRegisters().c,
&cpu->getRegisters().d,
&cpu->getRegisters().e,
&cpu->getRegisters().h,
&cpu->getRegisters().l,
nullptr,
&cpu->getRegisters().a};
uint8_t *dest = registerMapping[destination];
if (dest == nullptr) {
if (!gotAddress) {
address = cpu->getRegisters().hl;
gotAddress = true;
return false;
}
if (!retrievedStoredValue) {
storedValue = cpu->read(address);
retrievedStoredValue = true;
return false;
}
flags &= 0b00010000;
if (increment && ((storedValue)&0xF) == 0xF)
flags |= 1 << 5;
if (!increment && ((storedValue)&0xF) == 0x0)
flags |= 1 << 5;
if (increment)
cpu->write(address, storedValue + 1);
else
cpu->write(address, storedValue - 1);
if (!increment)
flags |= 0b01000000;
if (increment && ((storedValue + 1) & 0xFF) == 0)
flags |= 0b10000000;
if (!increment && ((storedValue - 1) & 0xFF) == 0)
flags |= 0b10000000;
} else {
flags &= 0b00010000;
if (increment && ((*dest) & 0xF) == 0xF)
flags |= 1 << 5;
if (!increment && ((*dest) & 0xF) == 0x0)
flags |= 1 << 5;
if (increment)
*dest = *dest + 1;
else
*dest = *dest - 1;
if (!increment)
flags |= 0b01000000;
if (*dest == 0)
flags |= 0b10000000;
}
}
return true;
}
std::string IncDec::getName() { return increment ? "Inc" : "Dec"; }
int IncDec::getType() {
return increment ? instruction::Inc : instruction::Dec;
}
ExtendedInstruction::ExtendedInstruction()
: instruction(0), valueAtHL(0), gotValueAtHL(false), result(0),
shouldWrite(false) {
finished = false;
}
std::unique_ptr<Instruction> ExtendedInstruction::decode(uint8_t opcode) {
if (opcode == 0xCB)
return std::make_unique<ExtendedInstruction>();
return nullptr;
}
void ExtendedInstruction::amend(uint8_t val) {
instruction = val;
finished = true;
LOG("\tCB Instruction: %02X | ", val);
// util::printfBits("", val, 8);
}
bool ExtendedInstruction::execute(CPU *cpu) {
uint8_t *registerMapping[] = {&cpu->getRegisters().b,
&cpu->getRegisters().c,
&cpu->getRegisters().d,
&cpu->getRegisters().e,
&cpu->getRegisters().h,
&cpu->getRegisters().l,
nullptr,
&cpu->getRegisters().a};
if ((instruction & 0x7) == 0b110 && !gotValueAtHL) {
valueAtHL = cpu->read(cpu->getRegisters().hl);
gotValueAtHL = true;
return false;
}
if (shouldWrite) {
cpu->write(cpu->getRegisters().hl, result);
return true;
}
result = gotValueAtHL ? valueAtHL : *registerMapping[instruction & 0x7];
uint8_t &flags = cpu->getRegisters().f;
if (instruction >> 4 == 0b0000) { // RdC D
bool isLeft = ((instruction >> 3) & 1) == 0;
if (isLeft) {
LOG("Rotate left (without carry\n");
flags &= 0b00001111;
bool carrySet = (result & 0x80) == 0x80;
if (carrySet)
flags |= 1 << 4;
result = result << 1;
if (carrySet)
result |= 1;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else {
LOG("Rotate right (without carry\n");
flags &= 0b00001111;
bool carrySet = (result & 0x1) == 0x1;
if (carrySet)
flags |= 1 << 4;
result = result >> 1;
if (carrySet)
result |= 0x80;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
}
} else if (instruction >> 4 == 0b0001) { // Rd D
bool isLeft = ((instruction >> 3) & 1) == 0;
if (isLeft) {
LOG("Rotate left\n");
bool carrySet = (flags & (1 << 4)) == (1 << 4);
flags &= 0b00001111;
if (result & 0x80)
flags |= 1 << 4;
result = result << 1;
if (carrySet)
result |= 1;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else {
LOG("Rotate right\n");
bool carrySet = (flags & (1 << 4)) == (1 << 4);
flags &= 0b00001111;
if (result & 0x1)
flags |= 1 << 4;
result = result >> 1;
if (carrySet)
result |= 0x80;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
}
} else if (instruction >> 4 == 0b0010) { // sdA D
bool isLeft = ((instruction >> 3) & 1) == 0;
if (isLeft) {
LOG("Shift left\n");
flags &= 0b00001111;
bool carrySet = (result & 0x80) == 0x80;
if (carrySet)
flags |= 1 << 4;
result = result << 1;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else {
LOG("Arithmetic shift right\n");
flags &= 0b00001111;
bool carrySet = (result & 0x1) == 0x1;
if (carrySet)
flags |= 1 << 4;
result = result >> 1;
if (result & 0b01000000)
result |= 0x80;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
}
} else if (instruction >> 3 == 0b00110) { // SWAP D
LOG("SWAP\n");
result = (result << 4) | (result >> 4);
flags &= 0b00001111;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else if (instruction >> 3 == 0b00111) { // SRL D
LOG("Logical shift right\n");
flags &= 0b00001111;
bool carrySet = (result & 0x1) == 0x1;
if (carrySet)
flags |= 1 << 4;
result = result >> 1;
if (result == 0)
flags |= 1 << 7;
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else if (instruction >> 6 == 0b01) { // BIT N,D
LOG("Testing BIT\n");
uint8_t n = (instruction >> 3) & 0x7;
flags &= 0b00010000;
flags |= 1 << 5;
if (((result) & (1 << n)) == 0)
flags |= 1 << 7;
} else if (instruction >> 6 == 0b10) { // RES N,D
LOG("Resetting BIT\n");
uint8_t n = (instruction >> 3) & 0x7;
result &= ~(1 << n);
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
} else if (instruction >> 6 == 0b11) { // SET N,D
LOG("Setting BIT\n");
uint8_t n = (instruction >> 3) & 0x7;
result |= (1 << n);
if (registerMapping[instruction & 0x7] != nullptr) {
*registerMapping[instruction & 0x7] = result;
} else {
shouldWrite = true;
return false;
}
}
return true;
}
std::string ExtendedInstruction::getName() { return "CB extended instruction"; }
int ExtendedInstruction::getType() { return instruction::CB; }
RST::RST(uint8_t n) : n(n), state(3) { finished = true; }
std::unique_ptr<Instruction> RST::decode(uint8_t opcode) {
if ((opcode >> 6) == 0b11 && (opcode & 0x7) == 0b111)
return std::make_unique<RST>(opcode & 0x38);
return nullptr;
}
bool RST::execute(CPU *cpu) {
switch (state) {
case 3: {
state--;
return false;
}
case 2: {
cpu->getRegisters().sp--;
cpu->write(cpu->getRegisters().sp, (cpu->getRegisters().pc >> 8) & 0xFF);
state--;
return false;
}
case 1: {
cpu->getRegisters().sp--;
cpu->write(cpu->getRegisters().sp, cpu->getRegisters().pc & 0xFF);
state--;
return false;
}
case 0: {
cpu->getRegisters().pc = n;
}
}
return true;
}
std::string RST::getName() { return "RST"; }
int RST::getType() { return instruction::RST; }
ALU::ALU(bool takesImmediate, uint8_t operation, uint8_t source)
: takesImmediate(takesImmediate), operation(operation), source(source),
address(0) {
finished = !takesImmediate;
}
std::unique_ptr<Instruction> ALU::decode(uint8_t opcode) {
if ((opcode >> 7) == 0b1 &&
(((opcode >> 6) & 1) == 0 || (opcode & 0x7) == 0b110))
return std::make_unique<ALU>(((opcode >> 6) & 1) == 1, (opcode >> 3) & 0x7,
opcode & 0x7);
return nullptr;
}
void ALU::amend(uint8_t val) {
immediate = val;
LOG("Got immediate\n");
finished = true;
}
bool ALU::execute(CPU *cpu) {
uint8_t *registerMapping[] = {&cpu->getRegisters().b,
&cpu->getRegisters().c,
&cpu->getRegisters().d,
&cpu->getRegisters().e,
&cpu->getRegisters().h,
&cpu->getRegisters().l,
nullptr,
&cpu->getRegisters().a};
uint8_t *dest = &cpu->getRegisters().a;
if (!takesImmediate && source == 0b110 && !address) {
address = cpu->getRegisters().hl;
return false;
}
uint8_t &flags = cpu->getRegisters().f;
uint8_t src = address
? cpu->read(address)
: (takesImmediate ? immediate : *(registerMapping[source]));
uint8_t carry = (flags >> 4) & 1;
flags = 0;
// TODO: implement H flag and make sure it's right
switch (operation) {
case 0b000 /*ADD*/: {
if (((uint32_t)*dest) + ((uint32_t)src) > 0xFF)
flags |= 1 << 4;
if (((*dest) & 0xF) + (src & 0xF) > 0xF)
flags |= 1 << 5;
*dest += src;
if (*dest == 0)
flags |= 1 << 7;
break;
}
case 0b001 /*ADC*/: {
if (((uint32_t)*dest) + ((uint32_t)src) + (uint32_t)carry > 0xFF)
flags |= 1 << 4;
if (((*dest) & 0xF) + (src & 0xF) + carry > 0xF)
flags |= 1 << 5;
*dest += src + carry;
if (*dest == 0)
flags |= 1 << 7;
break;
}
case 0b010 /*SUB*/: {
if (*dest < src)
flags |= 1 << 4;
if (((*dest) & 0xF) < (src & 0xF))
flags |= 1 << 5;
*dest -= src;
if (*dest == 0)
flags |= 1 << 7;
flags |= 0b01000000;
break;
}
case 0b011 /*SBC*/: {
if (((int32_t)*dest) < ((int32_t)src) + (int32_t)carry)
flags |= 1 << 4;
if (((*dest) & 0xF) < (src & 0xF) + carry)
flags |= 1 << 5;
*dest += -src - carry;
if (*dest == 0)
flags |= 1 << 7;
flags |= 0b01000000;
break;
}
case 0b100 /*AND*/: {
*dest &= src;
if (*dest == 0)
flags |= 1 << 7;
flags |= 1 << 5;
break;
}
case 0b101 /*XOR*/: {
*dest ^= src;
if (*dest == 0)
flags |= 1 << 7;
break;
}
case 0b110 /*OR */: {
*dest |= src;
if (*dest == 0)
flags |= 1 << 7;
break;
}
case 0b111 /*CP */: {
flags |= 0b01000000;
if (*dest < src)
flags |= 1 << 4;
if (((*dest) & 0xF) < (src & 0xF))
flags |= 1 << 5;
if (*dest == src)
flags |= 1 << 7;
break;
}
default:
break;
}
return true;
}
std::string ALU::getName() {
switch (operation) {
case 0b000:
return "ADD";
case 0b001:
return "ADC";
case 0b010:
return "SUB";
case 0b011:
return "SBC";
case 0b100:
return "AND";
case 0b101:
return "XOR";
case 0b110:
return "OR";
case 0b111:
return "CP";
}
return "ALU";
}
int ALU::getType() { return instruction::ALU; }