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Implement missing Compare Instructions

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Palindromic Bread Loaf
2025-07-23 19:28:35 -04:00
parent c0bfc265d0
commit 3414d11723
2 changed files with 98 additions and 11 deletions
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104
src/cpu.cpp
View File

@@ -356,17 +356,21 @@ void CPU::ExecuteInstruction() {
case 0xB8: CLV(); break; // CLV
// CMP - Compare Accumulator
case 0xC9: CMP_Immediate(); break; // CMP #$nn or #$nnnn
case 0xCD: CMP_Absolute(); break; // CMP $nnnn
case 0xDD: CMP_AbsoluteX(); break; // CMP $nnnn,X
case 0xD9: CMP_AbsoluteY(); break; // CMP $nnnn,Y
case 0xC5: CMP_DirectPage(); break; // CMP $nn
case 0xD5: CMP_DirectPageX(); break; // CMP $nn,X
case 0xD2: CMP_IndirectDirectPage(); break; // CMP ($nn)
case 0xD1: CMP_IndirectDirectPageY(); break; // CMP ($nn),Y
case 0xC1: CMP_DirectPageIndirectX(); break; // CMP ($nn,X)
case 0xCF: CMP_Long(); break; // CMP $nnnnnn
case 0xDF: CMP_LongX(); break; // CMP $nnnnnn,X
case 0xC9: CMP_Immediate(); break; // CMP #$nn or #$nnnn
case 0xCD: CMP_Absolute(); break; // CMP $nnnn
case 0xDD: CMP_AbsoluteX(); break; // CMP $nnnn,X
case 0xD9: CMP_AbsoluteY(); break; // CMP $nnnn,Y
case 0xC5: CMP_DirectPage(); break; // CMP $nn
case 0xD5: CMP_DirectPageX(); break; // CMP $nn,X
case 0xD2: CMP_IndirectDirectPage(); break; // CMP ($nn)
case 0xD1: CMP_IndirectDirectPageY(); break; // CMP ($nn),Y
case 0xC1: CMP_DirectPageIndirectX(); break; // CMP ($nn,X)
case 0xCF: CMP_Long(); break; // CMP $nnnnnn
case 0xDF: CMP_LongX(); break; // CMP $nnnnnn,X
case 0xC3: CMP_StackRelative(); break; // CMP sr,S
case 0xC7: CMP_IndirectDirectPageLong(); break; // CMP [dp]
case 0xD3: CMP_StackRelativeIndirectY(); break; // CMP (sr,S),Y
case 0xD7: CMP_IndirectDirectPageLongY(); break; // CMP [dp],Y
// CPX - Compare X Register
case 0xE0: CPX_Immediate(); break; // CPX #$nn or #$nnnn
@@ -2821,3 +2825,81 @@ void CPU::CLV() {
P &= ~FLAG_V;
cycles += 2;
}
void CPU::CMP_StackRelative() {
const uint8_t offset = ReadByte(PC++);
const uint32_t address = SP + offset;
if (P & FLAG_M) { // 8-bit mode
const uint8_t operand = ReadByte(address);
UpdateCompareFlags8(A & 0xFF, operand);
cycles += 4;
} else { // 16-bit mode
const uint16_t operand = ReadWord(address);
UpdateCompareFlags16(A, operand);
cycles += 5;
}
}
void CPU::CMP_IndirectDirectPageLong() {
const uint8_t offset = ReadByte(PC++);
const uint32_t pointer_address = D + offset;
const uint32_t full_address = ReadByte(pointer_address) |
(ReadByte(pointer_address + 1) << 8) |
(ReadByte(pointer_address + 2) << 16);
if (P & FLAG_M) { // 8-bit mode
const uint8_t operand = ReadByte(full_address);
UpdateCompareFlags8(A & 0xFF, operand);
cycles += 6;
if (D & 0xFF) cycles++;
} else { // 16-bit mode
const uint16_t operand = ReadWord(full_address);
UpdateCompareFlags16(A, operand);
cycles += 7;
if (D & 0xFF) cycles++;
}
}
void CPU::CMP_StackRelativeIndirectY() {
const uint8_t offset = ReadByte(PC++);
const uint32_t pointer_address = SP + offset;
const uint16_t base_address = ReadWord(pointer_address);
const uint32_t full_address = (DB << 16) | (base_address + Y);
if (P & FLAG_M) { // 8-bit mode
const uint8_t operand = ReadByte(full_address);
UpdateCompareFlags8(A & 0xFF, operand);
cycles += 7;
} else { // 16-bit mode
const uint16_t operand = ReadWord(full_address);
UpdateCompareFlags16(A, operand);
cycles += 8;
}
}
void CPU::CMP_IndirectDirectPageLongY() {
const uint8_t offset = ReadByte(PC++);
const uint32_t pointer_address = D + offset;
const uint32_t base_address = ReadByte(pointer_address) |
(ReadByte(pointer_address + 1) << 8) |
(ReadByte(pointer_address + 2) << 16);
const uint32_t full_address = base_address + Y;
if (P & FLAG_M) { // 8-bit mode
const uint8_t operand = ReadByte(full_address);
UpdateCompareFlags8(A & 0xFF, operand);
cycles += 6;
if (D & 0xFF) cycles++;
} else { // 16-bit mode
const uint16_t operand = ReadWord(full_address);
UpdateCompareFlags16(A, operand);
cycles += 7;
if (D & 0xFF) cycles++;
}
}

5
src/cpu.h
View File

@@ -256,6 +256,11 @@ public:
void CLD();
void CLI();
void CLV();
void CMP_StackRelative();
void CMP_IndirectDirectPageLong();
void CMP_StackRelativeIndirectY();
void CMP_IndirectDirectPageLongY();
};
#endif //CPU_H