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Merge pull request #56 from mre/incdec 

Sort out increments and decrements
This commit is contained in:
omarandlorraine 2022-10-21 09:15:05 +01:00 committed by GitHub
parent 8850934023 32f925feb2
commit a28ae7e584
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 115 additions and 53 deletions
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164
src/cpu.rs
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@ -207,10 +207,19 @@ impl CPU {
self.compare_with_y_register(val);
}
(Instruction::DEC, OpInput::UseAddress(addr)) => self.decrement_memory(addr),
(Instruction::DEC, OpInput::UseAddress(addr)) => {
CPU::decrement(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
}
(Instruction::DEY, OpInput::UseImplied) => {
CPU::decrement(&mut self.registers.index_y, &mut self.registers.status);
}
(Instruction::DEX, OpInput::UseImplied) => {
self.dec_x();
CPU::decrement(&mut self.registers.index_x, &mut self.registers.status);
}
(Instruction::EOR, OpInput::UseImmediate(val)) => {
@ -222,19 +231,16 @@ impl CPU {
}
(Instruction::INC, OpInput::UseAddress(addr)) => {
let m = self.memory.get_byte(addr);
let m = m + 1;
self.memory.set_byte(addr, m);
let i = m as i8;
CPU::set_flags_from_i8(&mut self.registers.status, i);
CPU::increment(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
}
(Instruction::INX, OpInput::UseImplied) => {
let x = self.registers.index_x + 1;
self.load_x_register(x);
CPU::increment(&mut self.registers.index_x, &mut self.registers.status);
}
(Instruction::INY, OpInput::UseImplied) => {
let y = self.registers.index_y + 1;
self.load_y_register(y);
CPU::increment(&mut self.registers.index_x, &mut self.registers.status);
}
(Instruction::JMP, OpInput::UseAddress(addr)) => self.jump(addr),
@ -251,22 +257,22 @@ impl CPU {
(Instruction::LDX, OpInput::UseImmediate(val)) => {
debug!("load X immediate: {}", val);
self.load_x_register(val as i8);
self.load_x_register(val);
}
(Instruction::LDX, OpInput::UseAddress(addr)) => {
let val = self.memory.get_byte(addr);
debug!("load X. address: {:?}. value: {}", addr, val);
self.load_x_register(val as i8);
self.load_x_register(val);
}
(Instruction::LDY, OpInput::UseImmediate(val)) => {
debug!("load Y immediate: {}", val);
self.load_y_register(val as i8);
self.load_y_register(val);
}
(Instruction::LDY, OpInput::UseAddress(addr)) => {
let val = self.memory.get_byte(addr);
debug!("load Y. address: {:?}. value: {}", addr, val);
self.load_y_register(val as i8);
self.load_y_register(val);
}
(Instruction::LSR, OpInput::UseImplied) => {
@ -371,20 +377,19 @@ impl CPU {
(Instruction::TAX, OpInput::UseImplied) => {
let val = self.registers.accumulator;
self.load_x_register(val);
self.load_x_register(val as u8);
}
(Instruction::TAY, OpInput::UseImplied) => {
let val = self.registers.accumulator;
self.load_y_register(val);
self.load_y_register(val as u8);
}
(Instruction::TSX, OpInput::UseImplied) => {
let StackPointer(val) = self.registers.stack_pointer;
let val = val as i8;
self.load_x_register(val);
}
(Instruction::TXA, OpInput::UseImplied) => {
let val = self.registers.index_x;
self.load_accumulator(val);
self.load_accumulator(val as i8);
}
(Instruction::TXS, OpInput::UseImplied) => {
// Note that this is the only 'transfer' instruction that does
@ -395,7 +400,7 @@ impl CPU {
}
(Instruction::TYA, OpInput::UseImplied) => {
let val = self.registers.index_y;
self.load_accumulator(val);
self.load_accumulator(val as i8);
}
(Instruction::NOP, OpInput::UseImplied) => {
@ -430,6 +435,20 @@ impl CPU {
);
}
fn set_flags_from_u8(status: &mut Status, value: u8) {
let is_zero = value == 0;
let is_negative = value > 127;
status.set_with_mask(
Status::PS_ZERO | Status::PS_NEGATIVE,
Status::new(StatusArgs {
zero: is_zero,
negative: is_negative,
..StatusArgs::none()
}),
);
}
fn shift_left_with_flags(p_val: &mut u8, status: &mut Status) {
let mask = 1 << 7;
let is_bit_7_set = (*p_val & mask) == mask;
@ -491,21 +510,26 @@ impl CPU {
CPU::set_flags_from_i8(status, *p_val as i8);
}
fn set_u8_with_flags(mem: &mut u8, status: &mut Status, value: u8) {
*mem = value;
CPU::set_flags_from_u8(status, value);
}
fn set_i8_with_flags(mem: &mut i8, status: &mut Status, value: i8) {
*mem = value;
CPU::set_flags_from_i8(status, value);
}
fn load_x_register(&mut self, value: i8) {
CPU::set_i8_with_flags(
fn load_x_register(&mut self, value: u8) {
CPU::set_u8_with_flags(
&mut self.registers.index_x,
&mut self.registers.status,
value,
);
}
fn load_y_register(&mut self, value: i8) {
CPU::set_i8_with_flags(
fn load_y_register(&mut self, value: u8) {
CPU::set_u8_with_flags(
&mut self.registers.index_y,
&mut self.registers.status,
value,
@ -648,15 +672,14 @@ impl CPU {
self.load_accumulator(result);
}
fn decrement_memory(&mut self, addr: u16) {
let value_new = self.memory.get_byte(addr).wrapping_sub(1);
self.memory.set_byte(addr, value_new);
fn increment(val: &mut u8, flags: &mut Status) {
let value_new = val.wrapping_add(1);
*val = value_new;
let is_negative = (value_new as i8) < 0;
let is_zero = value_new == 0;
self.registers.status.set_with_mask(
flags.set_with_mask(
Status::PS_NEGATIVE | Status::PS_ZERO,
Status::new(StatusArgs {
negative: is_negative,
@ -666,9 +689,21 @@ impl CPU {
);
}
fn dec_x(&mut self) {
let val = self.registers.index_x;
self.load_x_register(val - 1);
fn decrement(val: &mut u8, flags: &mut Status) {
let value_new = val.wrapping_sub(1);
*val = value_new;
let is_negative = (value_new as i8) < 0;
let is_zero = value_new == 0;
flags.set_with_mask(
Status::PS_NEGATIVE | Status::PS_ZERO,
Status::new(StatusArgs {
negative: is_negative,
zero: is_zero,
..StatusArgs::none()
}),
);
}
fn jump(&mut self, addr: u16) {
@ -754,12 +789,12 @@ impl CPU {
debug!("compare_with_x_register");
let x = self.registers.index_x;
self.compare(x, val);
self.compare(x as i8, val);
}
fn compare_with_y_register(&mut self, val: u8) {
let y = self.registers.index_y;
self.compare(y, val);
self.compare(y as i8, val);
}
fn exclusive_or(&mut self, val: u8) {
@ -1026,27 +1061,54 @@ mod tests {
cpu.memory.set_byte(addr, 5);
cpu.decrement_memory(addr);
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
assert_eq!(cpu.memory.get_byte(addr), 4);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
cpu.decrement_memory(addr);
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
assert_eq!(cpu.memory.get_byte(addr), 3);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
cpu.decrement_memory(addr);
cpu.decrement_memory(addr);
cpu.decrement_memory(addr);
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
assert_eq!(cpu.memory.get_byte(addr), 0);
assert!(cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
cpu.decrement_memory(addr);
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
assert_eq!(cpu.memory.get_byte(addr) as i8, -1);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(cpu.registers.status.contains(Status::PS_NEGATIVE));
cpu.memory.set_byte(addr, 0);
cpu.execute_instruction((Instruction::DEC, OpInput::UseAddress(addr)));
assert_eq!(cpu.memory.get_byte(addr), 0xff);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(cpu.registers.status.contains(Status::PS_NEGATIVE));
}
#[test]
fn decrement_x_test() {
let mut cpu = CPU::new();
cpu.registers.index_x = 0x80;
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 127);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
}
#[test]
fn decrement_y_test() {
let mut cpu = CPU::new();
cpu.registers.index_y = 0x80;
cpu.execute_instruction((Instruction::DEY, OpInput::UseImplied));
assert_eq!(cpu.registers.index_y, 127);
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
}
#[test]
@ -1091,32 +1153,32 @@ mod tests {
fn dec_x_test() {
let mut cpu = CPU::new();
cpu.dec_x();
assert_eq!(cpu.registers.index_x, -1);
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 0xff);
assert!(!cpu.registers.status.contains(Status::PS_CARRY));
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(cpu.registers.status.contains(Status::PS_NEGATIVE));
assert!(!cpu.registers.status.contains(Status::PS_OVERFLOW));
cpu.dec_x();
assert_eq!(cpu.registers.index_x, -2);
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 0xfe);
assert!(!cpu.registers.status.contains(Status::PS_CARRY));
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(cpu.registers.status.contains(Status::PS_NEGATIVE));
assert!(!cpu.registers.status.contains(Status::PS_OVERFLOW));
cpu.load_x_register(5);
cpu.dec_x();
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 4);
assert!(!cpu.registers.status.contains(Status::PS_CARRY));
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
assert!(!cpu.registers.status.contains(Status::PS_OVERFLOW));
cpu.dec_x();
cpu.dec_x();
cpu.dec_x();
cpu.dec_x();
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 0);
assert!(!cpu.registers.status.contains(Status::PS_CARRY));
@ -1124,8 +1186,8 @@ mod tests {
assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE));
assert!(!cpu.registers.status.contains(Status::PS_OVERFLOW));
cpu.dec_x();
assert_eq!(cpu.registers.index_x, -1);
cpu.execute_instruction((Instruction::DEX, OpInput::UseImplied));
assert_eq!(cpu.registers.index_x, 0xff);
assert!(!cpu.registers.status.contains(Status::PS_CARRY));
assert!(!cpu.registers.status.contains(Status::PS_ZERO));
assert!(cpu.registers.status.contains(Status::PS_NEGATIVE));

4
src/registers.rs
View File

@ -161,8 +161,8 @@ impl StackPointer {
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct Registers {
pub accumulator: i8,
pub index_x: i8,
pub index_y: i8,
pub index_x: u8,
pub index_y: u8,
pub stack_pointer: StackPointer,
pub program_counter: u16,
pub status: Status,