ComSquare/sources/CPU/Instructions/MathematicalOperations.cpp

//
// Created by anonymus-raccoon on 2/10/20.
//

#include <iostream>
#include "../CPU.hpp"

namespace ComSquare::CPU
{
	int CPU::ADC(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned value = this->_bus->read(valueAddr) + this->_registers.p.c;
		if (!this->_registers.p.m)
			value += this->_bus->read(valueAddr + 1) << 8u;
		unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
		unsigned maxValue = this->_registers.p.m ? UINT8_MAX : UINT16_MAX;

		this->_registers.p.c = static_cast<unsigned>(this->_registers.a) + value > maxValue;
		if ((this->_registers.a & negativeMask) == (value & negativeMask))
			this->_registers.p.v = (this->_registers.a & negativeMask) != ((this->_registers.a + value) & negativeMask);
		else
			this->_registers.p.v = false;
		this->_registers.a += value;
		if (this->_registers.p.m)
			this->_registers.a %= 0x100;
		this->_registers.p.z = this->_registers.a == 0;
		this->_registers.p.n = this->_registers.a & negativeMask;

		int cycles = !this->_registers.p.m;
		switch (mode) {
		case DirectPage:
		case DirectPageIndirect:
		case DirectPageIndirectLong:
		case DirectPageIndexedByX:
		case DirectPageIndirectIndexedByX:
		case DirectPageIndirectIndexedByYLong:
			cycles += this->_registers.dl != 0;
			break;
		case AbsoluteIndexedByX:
		case AbsoluteIndexedByY:
			cycles += this->_hasIndexCrossedPageBoundary;
			break;
		case DirectPageIndirectIndexedByY:
			cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
			break;
		default:
			break;
		}
		return cycles;
	}

	int CPU::SBC(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
		unsigned value = this->_bus->read(valueAddr);
		if (!this->_registers.p.m)
			value += this->_bus->read(valueAddr + 1) << 8u;
		bool oldCarry = this->_registers.p.c;

		this->_registers.p.c = this->_registers.a >= value;
		if ((this->_registers.a & negativeMask) == (value & negativeMask))
			this->_registers.p.v = (this->_registers.a & negativeMask) != ((this->_registers.a + value) & negativeMask);
		else
			this->_registers.p.v = false;
		this->_registers.a += ~value + oldCarry;
		if (this->_registers.p.m)
			this->_registers.a %= 0x100;
		this->_registers.p.z = this->_registers.a == 0;
		this->_registers.p.n = this->_registers.a & negativeMask;

		int cycles = !this->_registers.p.m;
		switch (mode) {
		case DirectPage:
		case DirectPageIndirect:
		case DirectPageIndirectLong:
		case DirectPageIndexedByX:
		case DirectPageIndirectIndexedByX:
		case DirectPageIndirectIndexedByYLong:
			cycles += this->_registers.dl != 0;
			break;
		case AbsoluteIndexedByX:
		case AbsoluteIndexedByY:
			cycles += this->_hasIndexCrossedPageBoundary;
			break;
		case DirectPageIndirectIndexedByY:
			cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
			break;
		default:
			break;
		}
		return cycles;
	}

	int CPU::ORA(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
		unsigned value = this->_bus->read(valueAddr);
		if (!this->_registers.p.m)
			value += this->_bus->read(valueAddr + 1) << 8u;
		this->_registers.a |= value;
		this->_registers.p.z = this->_registers.a == 0;
		this->_registers.p.n = this->_registers.a & negativeMask;

		int cycles = !this->_registers.p.m;
		switch (mode) {
		case DirectPage:
		case DirectPageIndirect:
		case DirectPageIndirectLong:
		case DirectPageIndexedByX:
		case DirectPageIndirectIndexedByX:
		case DirectPageIndirectIndexedByYLong:
			cycles += this->_registers.dl != 0;
			break;
		case AbsoluteIndexedByX:
		case AbsoluteIndexedByY:
			cycles += this->_hasIndexCrossedPageBoundary;
			break;
		case DirectPageIndirectIndexedByY:
			cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
			break;
		default:
			break;
		}
		return cycles;
	}

	int CPU::DEX(uint24_t, AddressingMode)
	{
		unsigned negativeMask = this->_registers.p.x_b ? 0x80 : 0x8000;

		this->_registers.x--;
		if (this->_registers.p.x_b)
			this->_registers.xh = 0;
		this->_registers.p.z = this->_registers.x == 0;
		this->_registers.p.n = this->_registers.x & negativeMask;
		return 0;
	}

	int CPU::DEY(uint24_t, AddressingMode)
	{
		unsigned negativeMask = this->_registers.p.x_b ? 0x80 : 0x8000;

		this->_registers.y--;
		if (this->_registers.p.x_b)
			this->_registers.yh = 0;
		this->_registers.p.z = this->_registers.y == 0;
		this->_registers.p.n = this->_registers.y & negativeMask;
		return 0;
	}

	int CPU::CMP(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
		unsigned value = this->_bus->read(valueAddr);
		if (!this->_registers.p.m)
			value += this->_bus->read(valueAddr + 1) << 8u;
		unsigned result = this->_registers.a - value;
		if (this->_registers.p.m)
			result %= 0x100;

		this->_registers.p.n = result & negativeMask;
		this->_registers.p.z = result == 0;
		this->_registers.p.c = this->_registers.a >= result;

		int cycles = !this->_registers.p.m;
		switch (mode) {
		case DirectPage:
		case DirectPageIndirect:
		case DirectPageIndirectLong:
		case DirectPageIndexedByX:
		case DirectPageIndirectIndexedByX:
		case DirectPageIndirectIndexedByYLong:
			cycles += this->_registers.dl != 0;
			break;
		case AbsoluteIndexedByX:
		case AbsoluteIndexedByY:
			cycles += this->_hasIndexCrossedPageBoundary;
			break;
		case DirectPageIndirectIndexedByY:
			cycles += this->_registers.dl != 0 + this->_hasIndexCrossedPageBoundary;
			break;
		default:
			break;
		}
		return cycles;
	}


	int CPU::INX(uint24_t, AddressingMode)
	{
		this->_registers.x++;

		if (this->_registers.p.x_b)
			this->_registers.x %= 0x100;

		unsigned negativeFlag = this->_registers.p.x_b ? 0x80u : 0x8000u;
		this->_registers.p.z = this->_registers.x == 0;
		this->_registers.p.n = this->_registers.x & negativeFlag;
		return 0;
	}

	int CPU::INY(uint24_t, AddressingMode)
	{
		this->_registers.y++;

		if (this->_registers.p.x_b)
			this->_registers.y %= 0x100;

		unsigned negativeFlag = this->_registers.p.x_b ? 0x80u : 0x8000u;
		this->_registers.p.z = this->_registers.y == 0;
		this->_registers.p.n = this->_registers.y & negativeFlag;
		return 0;
	}

	int CPU::CPX(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned value = this->_bus->read(valueAddr++);

		if (this->_registers.p.x_b) {
			uint8_t x = this->_registers.x;
			x -= value;
			this->_registers.p.z = x == 0;
			this->_registers.p.n = x & 0x80u;
		} else {
			value += this->_bus->read(valueAddr) << 8u;
			uint16_t x = this->_registers.x;
			x -= value;
			this->_registers.p.z = x == 0;
			this->_registers.p.n = x & 0x8000u;
		}
		this->_registers.p.c = this->_registers.x >= value;
		return !this->_registers.p.x_b + (mode == DirectPage && this->_registers.dl != 0);
	}

	int CPU::CPY(uint24_t valueAddr, AddressingMode mode)
	{
		unsigned value = this->_bus->read(valueAddr++);

		this->_registers.p.c = this->_registers.y >= value;
		if (this->_registers.p.x_b) {
			uint8_t y = this->_registers.y;
			y -= value;
			this->_registers.p.z = y == 0;
			this->_registers.p.n = y & 0x80u;
		} else {
			value += this->_bus->read(valueAddr) << 8u;
			uint16_t y = this->_registers.y;
			y -= value;
			this->_registers.p.z = y == 0;
			this->_registers.p.n = y & 0x8000u;
		}
		return !this->_registers.p.x_b + (mode == DirectPage && this->_registers.dl != 0);
	}
}