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Simplification of M6502 flag set/reset code

This commit is contained in:
Adrian Conlon 2024-01-07 14:04:41 +00:00
parent 7eca073a6e
commit 4f4bc5355d
3 changed files with 57 additions and 57 deletions
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36
M6502/inc/mos6502.h
View File

@ -137,8 +137,8 @@ namespace EightBit {
// Flag adjustment
constexpr void adjustZero(const uint8_t datum) noexcept { P() = clearBit(P(), ZF, datum); }
constexpr void adjustNegative(const uint8_t datum) noexcept { P() = setBit(P(), NF, negative(datum)); }
constexpr void adjustZero(const uint8_t datum) noexcept { reset_flag(ZF, datum); }
constexpr void adjustNegative(const uint8_t datum) noexcept { set_flag(NF, negative(datum)); }
constexpr void adjustNZ(const uint8_t datum) noexcept {
adjustZero(datum);
@ -166,6 +166,14 @@ namespace EightBit {
BUS().ADDRESS() = address;
}
// Status flag operations
constexpr void set_flag(int which, int condition) noexcept { P() = setBit(P(), which, condition); }
constexpr void set_flag(int which) noexcept { P() = setBit(P(), which); }
constexpr void reset_flag(int which, int condition) noexcept { P() = clearBit(P(), which, condition); }
constexpr void reset_flag(int which) noexcept { P() = clearBit(P(), which); }
// Chew up a cycle
void swallow() noexcept { memoryRead(PC()); }
void swallow_stack() noexcept { getBytePaged(1, S()); }
@ -174,22 +182,38 @@ namespace EightBit {
// Instruction implementations
[[nodiscard]] uint8_t andr(uint8_t operand, uint8_t data) noexcept;
[[nodiscard]] uint8_t asl(uint8_t value) noexcept;
void bit(uint8_t operand, uint8_t data) noexcept;
void cmp(uint8_t first, uint8_t second) noexcept;
[[nodiscard]] uint8_t dec(uint8_t value) noexcept;
[[nodiscard]] uint8_t eorr(uint8_t operand, uint8_t data) noexcept;
[[nodiscard]] uint8_t inc(uint8_t value) noexcept;
void jsr() noexcept;
[[nodiscard]] uint8_t lsr(uint8_t value) noexcept;
[[nodiscard]] uint8_t orr(uint8_t operand, uint8_t data) noexcept;
void php() noexcept;
void plp() noexcept;
[[nodiscard]] uint8_t rol(uint8_t operand) noexcept;
[[nodiscard]] uint8_t ror(uint8_t operand) noexcept;
void rti() noexcept;
void rts() noexcept;
[[nodiscard]] constexpr uint8_t asl(uint8_t value) noexcept {
set_flag(CF, value & Bit7);
return through(value << 1);
}
[[nodiscard]] constexpr uint8_t rol(uint8_t operand) noexcept {
const auto carryIn = carry();
return through(asl(operand) | carryIn);
}
[[nodiscard]] constexpr uint8_t lsr(uint8_t value) noexcept {
set_flag(CF, value & Bit0);
return through(value >> 1);
}
[[nodiscard]] constexpr uint8_t ror(uint8_t operand) noexcept {
const auto carryIn = carry();
return through(lsr(operand) | (carryIn << 7));
}
// Undocumented compound instructions
void anc(uint8_t value) noexcept;

74
M6502/src/mos6502.cpp
View File

@ -100,7 +100,7 @@ void EightBit::MOS6502::interrupt() noexcept {
pushWord(PC());
push(P() | (software ? BF : 0));
}
P() = setBit(P(), IF); // Disable IRQ
set_flag(IF); // Disable IRQ
const uint8_t vector = reset ? RSTvector : (nmi ? NMIvector : IRQvector);
jump(getWordPaged(0xff, vector));
m_handlingRESET = m_handlingNMI = m_handlingINT = false;
@ -153,7 +153,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0x15: A() = orr(A(), AM_ZeroPageX()); break; // ORA (zero page, X)
case 0x16: memoryReadModifyWrite(asl(AM_ZeroPageX())); break; // ASL (zero page, X)
case 0x17: slo(AM_ZeroPageX()); break; // *SLO (zero page, X)
case 0x18: swallow(); P() = clearBit(P(), CF); break; // CLC (implied)
case 0x18: swallow(); reset_flag(CF); break; // CLC (implied)
case 0x19: A() = orr(A(), AM_AbsoluteY()); break; // ORA (absolute, Y)
case 0x1a: swallow(); break; // *NOP (implied)
case 0x1b: slo_AbsoluteY(); break; // *SLO (absolute, Y)
@ -170,7 +170,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0x25: A() = andr(A(), AM_ZeroPage()); break; // AND (zero page)
case 0x26: memoryReadModifyWrite(rol(AM_ZeroPage())); break; // ROL (zero page)
case 0x27: rla(AM_ZeroPage()); break; // *RLA (zero page)
case 0x28: swallow(); swallow_stack(); plp(); break; // PLP (implied)
case 0x28: swallow(); plp(); break; // PLP (implied)
case 0x29: A() = andr(A(), AM_Immediate()); break; // AND (immediate)
case 0x2a: swallow(); A() = rol(A()); break; // ROL A (implied)
case 0x2b: anc(AM_Immediate()); break; // *ANC (immediate)
@ -187,7 +187,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0x35: A() = andr(A(), AM_ZeroPageX()); break; // AND (zero page, X)
case 0x36: memoryReadModifyWrite(rol(AM_ZeroPageX())); break; // ROL (zero page, X)
case 0x37: rla(AM_ZeroPageX()); break; // *RLA (zero page, X)
case 0x38: swallow(); P() = setBit(P(), CF); break; // SEC (implied)
case 0x38: swallow(); set_flag(CF); break; // SEC (implied)
case 0x39: A() = andr(A(), AM_AbsoluteY()); break; // AND (absolute, Y)
case 0x3a: swallow(); break; // *NOP (implied)
case 0x3b: rla_AbsoluteY(); break; // *RLA (absolute, Y)
@ -221,7 +221,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0x55: A() = eorr(A(), AM_ZeroPageX()); break; // EOR (zero page, X)
case 0x56: memoryReadModifyWrite(lsr(AM_ZeroPageX())); break; // LSR (zero page, X)
case 0x57: sre(AM_ZeroPageX()); break; // *SRE (zero page, X)
case 0x58: swallow(); P() = clearBit(P(), IF); break; // CLI (implied)
case 0x58: swallow(); reset_flag(IF); break; // CLI (implied)
case 0x59: A() = eorr(A(), AM_AbsoluteY()); break; // EOR (absolute, Y)
case 0x5a: swallow(); break; // *NOP (implied)
case 0x5b: sre_AbsoluteY(); break; // *SRE (absolute, Y)
@ -255,7 +255,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0x75: A() = adc(A(), AM_ZeroPageX()); break; // ADC (zero page, X)
case 0x76: memoryReadModifyWrite(ror(AM_ZeroPageX())); break; // ROR (zero page, X)
case 0x77: rra(AM_ZeroPageX()); break; // *RRA (zero page, X)
case 0x78: swallow(); P() = setBit(P(), IF); break; // SEI (implied)
case 0x78: swallow(); set_flag(IF); break; // SEI (implied)
case 0x79: A() = adc(A(), AM_AbsoluteY()); break; // ADC (absolute, Y)
case 0x7a: swallow(); break; // *NOP (implied)
case 0x7b: rra_AbsoluteY(); break; // *RRA (absolute, Y)
@ -323,7 +323,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0xb5: A() = through(AM_ZeroPageX()); break; // LDA (zero page, X)
case 0xb6: X() = through(AM_ZeroPageY()); break; // LDX (zero page, Y)
case 0xb7: A() = X() = through(AM_ZeroPageY()); break; // *LAX (zero page, Y)
case 0xb8: swallow(); P() = clearBit(P(), VF); break; // CLV (implied)
case 0xb8: swallow(); reset_flag(VF); break; // CLV (implied)
case 0xb9: A() = through(AM_AbsoluteY()); break; // LDA (absolute, Y)
case 0xba: swallow(); X() = through(S()); break; // TSX (implied)
case 0xbb: break;
@ -357,7 +357,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0xd5: cmp(A(), AM_ZeroPageX()); break; // CMP (zero page, X)
case 0xd6: memoryReadModifyWrite(dec(AM_ZeroPageX())); break; // DEC (zero page, X)
case 0xd7: dcp(AM_ZeroPageX()); break; // *DCP (zero page, X)
case 0xd8: swallow(); P() = clearBit(P(), DF); break; // CLD (implied)
case 0xd8: swallow(); reset_flag(DF); break; // CLD (implied)
case 0xd9: cmp(A(), AM_AbsoluteY()); break; // CMP (absolute, Y)
case 0xda: swallow(); break; // *NOP (implied)
case 0xdb: dcp_AbsoluteY(); break; // *DCP (absolute, Y)
@ -391,7 +391,7 @@ int EightBit::MOS6502::execute() noexcept {
case 0xf5: A() = sbc(A(), AM_ZeroPageX()); break; // SBC (zero page, X)
case 0xf6: memoryReadModifyWrite(inc(AM_ZeroPageX())); break; // INC (zero page, X)
case 0xf7: isb(AM_ZeroPageX()); break; // *ISB (zero page, X)
case 0xf8: swallow(); P() = setBit(P(), DF); break; // SED (implied)
case 0xf8: swallow(); set_flag(DF); break; // SED (implied)
case 0xf9: A() = sbc(A(), AM_AbsoluteY()); break; // SBC (absolute, Y)
case 0xfa: swallow(); break; // *NOP (implied)
case 0xfb: isb_AbsoluteY(); break; // *ISB (absolute, Y)
@ -549,8 +549,8 @@ uint8_t EightBit::MOS6502::sbc(const uint8_t operand, const uint8_t data) noexce
const auto difference = m_intermediate;
adjustNZ(difference.low);
P() = setBit(P(), VF, (operand ^ data) & (operand ^ difference.low) & NF);
P() = clearBit(P(), CF, difference.high);
set_flag(VF, negative((operand ^ data) & (operand ^ difference.low)));
reset_flag(CF, difference.high);
return returned;
}
@ -591,8 +591,8 @@ uint8_t EightBit::MOS6502::add(uint8_t operand, uint8_t data, int carrying) noex
uint8_t EightBit::MOS6502::add_b(uint8_t operand, uint8_t data, int carrying) noexcept {
m_intermediate.word = operand + data + carrying;
P() = setBit(P(), VF, ~(operand ^ data) & (operand ^ m_intermediate.low) & NF);
P() = setBit(P(), CF, carry(m_intermediate.high));
set_flag(VF, negative(~(operand ^ data) & (operand ^ m_intermediate.low)));
set_flag(CF, carry(m_intermediate.high));
adjustNZ(m_intermediate.low);
@ -604,7 +604,7 @@ uint8_t EightBit::MOS6502::add_d(uint8_t operand, uint8_t data, int carry) noexc
register16_t low = lowerNibble(operand) + lowerNibble(data) + carry;
register16_t high = higherNibble(operand) + higherNibble(data);
P() = clearBit(P(), ZF, (low + high).low);
adjustZero((low + high).low);
if (low.word > 0x09) {
high += 0x10;
@ -612,12 +612,12 @@ uint8_t EightBit::MOS6502::add_d(uint8_t operand, uint8_t data, int carry) noexc
}
adjustNegative(high.low);
P() = setBit(P(), VF, ~(operand ^ data) & (operand ^ high.low) & NF);
set_flag(VF, negative(~(operand ^ data) & (operand ^ high.low)));
if (high.word > 0x90)
high += 0x60;
P() = setBit(P(), CF, high.high);
set_flag(CF, high.high);
return lowerNibble(low.low) | higherNibble(high.low);
}
@ -626,13 +626,8 @@ uint8_t EightBit::MOS6502::andr(const uint8_t operand, const uint8_t data) noexc
return through(operand & data);
}
uint8_t EightBit::MOS6502::asl(const uint8_t value) noexcept {
P() = setBit(P(), CF, value & Bit7);
return through(value << 1);
}
void EightBit::MOS6502::bit(const uint8_t operand, const uint8_t data) noexcept {
P() = setBit(P(), VF, overflow(data));
set_flag(VF, overflow(data));
adjustZero(operand & data);
adjustNegative(data);
}
@ -640,7 +635,7 @@ void EightBit::MOS6502::bit(const uint8_t operand, const uint8_t data) noexcept
void EightBit::MOS6502::cmp(const uint8_t first, const uint8_t second) noexcept {
const register16_t result = first - second;
adjustNZ(result.low);
P() = clearBit(P(), CF, result.high);
reset_flag(CF, result.high);
}
uint8_t EightBit::MOS6502::dec(const uint8_t value) noexcept {
@ -663,11 +658,6 @@ void EightBit::MOS6502::jsr() noexcept {
PC().low = low;
}
uint8_t EightBit::MOS6502::lsr(const uint8_t value) noexcept {
P() = setBit(P(), CF, value & Bit0);
return through(value >> 1);
}
uint8_t EightBit::MOS6502::orr(const uint8_t operand, const uint8_t data) noexcept {
return through(operand | data);
}
@ -677,25 +667,11 @@ void EightBit::MOS6502::php() noexcept {
}
void EightBit::MOS6502::plp() noexcept {
swallow_stack();
P() = (pop() | RF) & ~BF;
}
uint8_t EightBit::MOS6502::rol(const uint8_t operand) noexcept {
const auto carryIn = carry();
P() = setBit(P(), CF, operand & Bit7);
const uint8_t result = (operand << 1) | carryIn;
return through(result);
}
uint8_t EightBit::MOS6502::ror(const uint8_t operand) noexcept {
const auto carryIn = carry();
P() = setBit(P(), CF, operand & Bit0);
const uint8_t result = (operand >> 1) | (carryIn << 7);
return through(result);
}
void EightBit::MOS6502::rti() noexcept {
swallow_stack();
plp();
ret();
}
@ -710,7 +686,7 @@ void EightBit::MOS6502::rts() noexcept {
void EightBit::MOS6502::anc(const uint8_t value) noexcept {
A() = andr(A(), value);
P() = setBit(P(), CF, A() & Bit7);
set_flag(CF, A() & Bit7);
}
void EightBit::MOS6502::arr(const uint8_t value) noexcept {
@ -725,12 +701,12 @@ void EightBit::MOS6502::arr_d(const uint8_t value) noexcept {
A() &= value;
auto unshiftedA = A();
A() = through((A() >> 1) | (carry() << 7));
P() = setBit(P(), VF, (A() ^ (A() << 1)) & VF);
set_flag(VF, overflow((A() ^ (A() << 1))));
if (lowerNibble(unshiftedA) + (unshiftedA & 0x1) > 5)
A() = lowerNibble(A() + 6) | higherNibble(A());
P() = setBit(P(), CF, higherNibble(unshiftedA) + (unshiftedA & 0x10) > 0x50);
set_flag(CF, higherNibble(unshiftedA) + (unshiftedA & 0x10) > 0x50);
if (carry())
A() += 0x60;
@ -739,8 +715,8 @@ void EightBit::MOS6502::arr_d(const uint8_t value) noexcept {
void EightBit::MOS6502::arr_b(const uint8_t value) noexcept {
A() &= value;
A() = through((A() >> 1) | (carry() << 7));
P() = setBit(P(), CF, A() & Bit6);
P() = setBit(P(), VF, (A() ^ (A() << 1)) & VF);
set_flag(CF, A() & Bit6);
set_flag(VF, overflow((A() ^ (A() << 1))));
}
void EightBit::MOS6502::asr(const uint8_t value) noexcept {
@ -750,7 +726,7 @@ void EightBit::MOS6502::asr(const uint8_t value) noexcept {
void EightBit::MOS6502::axs(const uint8_t value) noexcept {
X() = through(sub_b(A() & X(), value));
P() = clearBit(P(), CF, m_intermediate.high);
reset_flag(CF, m_intermediate.high);
}
void EightBit::MOS6502::dcp(const uint8_t value) noexcept {

4
src/Processor.cpp
View File

@ -13,8 +13,8 @@ EightBit::Processor::Processor(const Processor& rhs)
PC() = rhs.PC();
}
DEFINE_PIN_LEVEL_CHANGERS(RESET, Processor);
DEFINE_PIN_LEVEL_CHANGERS(INT, Processor);
DEFINE_PIN_LEVEL_CHANGERS(RESET, Processor)
DEFINE_PIN_LEVEL_CHANGERS(INT, Processor)
void EightBit::Processor::handleRESET() noexcept {
raiseRESET();