EightBit/inc/IntelProcessor.h
Adrian.Conlon beca76d733 Share instruction decoding mechanism between Intel derived processors.
Signed-off-by: Adrian.Conlon <adrian.conlon@gmail.com>
2017-07-21 13:33:17 +01:00

236 lines
5.2 KiB
C++

#pragma once
#include <cstdint>
#include <array>
#include "Processor.h"
namespace EightBit {
class IntelProcessor : public Processor
{
public:
struct opcode_decoded_t {
int x;
int y;
int z;
int p;
int q;
opcode_decoded_t() {
x = y = z = p = q = 0;
}
opcode_decoded_t(uint8_t opcode) {
x = (opcode & 0b11000000) >> 6; // 0 - 3
y = (opcode & 0b00111000) >> 3; // 0 - 7
z = (opcode & 0b00000111); // 0 - 7
p = (y & 0b110) >> 1; // 0 - 3
q = (y & 1); // 0 - 1
}
};
const opcode_decoded_t& getDecodedOpcode(const int i) const {
return m_decodedOpcodes[i];
}
register16_t& MEMPTR() { return m_memptr; }
virtual void initialise();
register16_t& SP() { return sp; }
virtual register16_t& AF() = 0;
uint8_t& A() { return AF().high; }
uint8_t& F() { return AF().low; }
virtual register16_t& BC() = 0;
uint8_t& B() { return BC().high; }
uint8_t& C() { return BC().low; }
virtual register16_t& DE() = 0;
uint8_t& D() { return DE().high; }
uint8_t& E() { return DE().low; }
virtual register16_t& HL() = 0;
uint8_t& H() { return HL().high; }
uint8_t& L() { return HL().low; }
protected:
IntelProcessor(Memory& memory);
template<class T> static void adjustSign(uint8_t& f, uint8_t value) {
setFlag(f, T::SF, value & T::SF);
}
template<class T> static void adjustZero(uint8_t& f, uint8_t value) {
clearFlag(f, T::ZF, value);
}
template<class T> static void adjustParity(uint8_t& f, uint8_t value) {
static const int lookup[0x10] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
auto set = lookup[highNibble(value)] + lookup[lowNibble(value)];
clearFlag(f, T::PF, set % 2);
}
template<class T> static void adjustSZ(uint8_t& f, uint8_t value) {
adjustSign<T>(f, value);
adjustZero<T>(f, value);
}
template<class T> static void adjustSZP(uint8_t& f, uint8_t value) {
adjustSZ<T>(f, value);
adjustParity<T>(f, value);
}
template<class T> static void adjustXY(uint8_t& f, uint8_t value) {
setFlag(f, T::XF, value & T::XF);
setFlag(f, T::YF, value & T::YF);
}
template<class T> static void adjustSZPXY(uint8_t& f, uint8_t value) {
adjustSZP<T>(f, value);
adjustXY<T>(f, value);
}
template<class T> static void adjustSZXY(uint8_t& f, uint8_t value) {
adjustSZ<T>(f, value);
adjustXY<T>(f, value);
}
//
static int buildHalfCarryIndex(uint8_t before, uint8_t value, int calculation) {
__assume(calculation < 0x1ffff);
return ((before & 0x88) >> 1) | ((value & 0x88) >> 2) | ((calculation & 0x88) >> 3);
}
static bool calculateHalfCarryAdd(uint8_t before, uint8_t value, int calculation) {
__assume(calculation < 0x1ffff);
static std::array<bool, 8> m_halfCarryTableAdd = { { false, false, true, false, true, false, true, true } };
auto index = buildHalfCarryIndex(before, value, calculation);
return m_halfCarryTableAdd[index & Mask3];
}
static bool calculateHalfCarrySub(uint8_t before, uint8_t value, int calculation) {
__assume(calculation < 0x1ffff);
std::array<bool, 8> m_halfCarryTableSub = { { false, true, true, true, false, false, false, true } };
auto index = buildHalfCarryIndex(before, value, calculation);
return m_halfCarryTableSub[index & Mask3];
}
virtual uint8_t fetchByte() {
m_memory.ADDRESS().word = PC().word++;
return m_memory.reference();
}
void fetchWord(register16_t& output) {
output.low = fetchByte();
output.high = fetchByte();
}
virtual void push(uint8_t value) {
m_memory.ADDRESS().word = --SP().word;
m_memory.reference() = value;
}
void pushWord(const register16_t& value) {
push(value.high);
push(value.low);
}
virtual uint8_t pop() {
m_memory.ADDRESS().word = SP().word++;
return m_memory.reference();
}
void popWord(register16_t& output) {
output.low = pop();
output.high = pop();
}
void fetchWord() {
fetchWord(MEMPTR());
}
//
uint8_t& memptrReference() {
m_memory.ADDRESS() = MEMPTR();
MEMPTR().word++;
return m_memory.reference();
}
virtual void getWordViaMemptr(register16_t& value) {
value.low = memptrReference();
m_memory.ADDRESS().word++;
value.high = m_memory.reference();
}
virtual void setWordViaMemptr(register16_t value) {
memptrReference() = value.low;
m_memory.ADDRESS().word++;
m_memory.reference() = value.high;
}
//
void jump() {
PC() = MEMPTR();
}
void call() {
pushWord(PC());
jump();
}
void restart(uint8_t address) {
MEMPTR().low = address;
MEMPTR().high = 0;
call();
}
bool callConditional(int condition) {
fetchWord();
if (condition)
call();
return condition != 0;
}
bool jumpConditional(int conditional) {
fetchWord();
if (conditional)
jump();
return conditional != 0;
}
void ret() {
popWord(MEMPTR());
jump();
}
bool returnConditional(int condition) {
if (condition)
ret();
return condition != 0;
}
void jr(int8_t offset) {
MEMPTR().word = PC().word + offset;
jump();
}
bool jrConditional(int conditional) {
auto offset = fetchByte();
if (conditional)
jr(offset);
return conditional != 0;
}
private:
std::array<opcode_decoded_t, 0x100> m_decodedOpcodes;
register16_t m_memptr;
register16_t sp;
};
}