mirror of
https://github.com/mre/mos6502.git
synced 2024-12-01 11:51:51 +00:00
Add tests for stack over- and underflow
This commit is contained in:
Sam M W
parent
ad40c72dfe
commit
34bbe55712
215
src/cpu.rs
215
src/cpu.rs
@ -37,6 +37,12 @@ pub struct CPU {
|
||||
pub memory: Memory,
|
||||
}
|
||||
|
||||
impl Default for CPU {
|
||||
fn default() -> Self {
|
||||
Self::new()
|
||||
}
|
||||
}
|
||||
|
||||
impl CPU {
|
||||
pub fn new() -> CPU {
|
||||
CPU {
|
||||
@ -515,115 +521,125 @@ impl CPU {
|
||||
);
|
||||
}
|
||||
|
||||
fn add_with_carry(&mut self, value: i8) {
|
||||
let a_before: i8 = self.registers.accumulator;
|
||||
let c_before: i8 = if self.registers.status.contains(Status::PS_CARRY) {
|
||||
1
|
||||
} else {
|
||||
0
|
||||
};
|
||||
let a_after: i8 = a_before.wrapping_add(c_before).wrapping_add(value);
|
||||
fn add_with_carry(&mut self, value: i8) {
|
||||
let a_before: i8 = self.registers.accumulator;
|
||||
let c_before: i8 = if self.registers.status.contains(Status::PS_CARRY) {
|
||||
1
|
||||
} else {
|
||||
0
|
||||
};
|
||||
let a_after: i8 = a_before.wrapping_add(c_before).wrapping_add(value);
|
||||
|
||||
debug_assert_eq!(
|
||||
a_after as u8,
|
||||
a_before.wrapping_add(c_before).wrapping_add(value) as u8
|
||||
);
|
||||
debug_assert_eq!(
|
||||
a_after as u8,
|
||||
a_before.wrapping_add(c_before).wrapping_add(value) as u8
|
||||
);
|
||||
|
||||
let bcd1: i8 = if (a_after & 0x0f) as u8 > 0x09 {
|
||||
0x06
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
let bcd1: i8 = if (a_after & 0x0f) as u8 > 0x09 {
|
||||
0x06
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
|
||||
let bcd2: i8 = if (a_after.wrapping_add(bcd1) as u8 & 0xf0) as u8 > 0x90 {
|
||||
0x60
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
let bcd2: i8 = if (a_after.wrapping_add(bcd1) as u8 & 0xf0) as u8 > 0x90 {
|
||||
0x60
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
|
||||
let result: i8 = if self.registers.status.contains(Status::PS_DECIMAL_MODE) {
|
||||
a_after.wrapping_add(bcd1).wrapping_add(bcd2)
|
||||
} else {
|
||||
a_after
|
||||
};
|
||||
let result: i8 = if self.registers.status.contains(Status::PS_DECIMAL_MODE) {
|
||||
a_after.wrapping_add(bcd1).wrapping_add(bcd2)
|
||||
} else {
|
||||
a_after
|
||||
};
|
||||
|
||||
let did_carry = (result as u8) < (a_before as u8);
|
||||
let did_carry = (result as u8) < (a_before as u8);
|
||||
|
||||
let did_overflow = (a_before < 0 && value < 0 && a_after >= 0)
|
||||
|| (a_before > 0 && value > 0 && a_after <= 0);
|
||||
let did_overflow = (a_before < 0 && value < 0 && a_after >= 0)
|
||||
|| (a_before > 0 && value > 0 && a_after <= 0);
|
||||
|
||||
let mask = Status::PS_CARRY | Status::PS_OVERFLOW;
|
||||
let mask = Status::PS_CARRY | Status::PS_OVERFLOW;
|
||||
|
||||
self.registers.status.set_with_mask( mask, Status::new(StatusArgs { carry: did_carry, overflow: did_overflow, ..StatusArgs::none() }),);
|
||||
self.registers.status.set_with_mask(
|
||||
mask,
|
||||
Status::new(StatusArgs {
|
||||
carry: did_carry,
|
||||
overflow: did_overflow,
|
||||
..StatusArgs::none()
|
||||
}),
|
||||
);
|
||||
|
||||
self.load_accumulator(result);
|
||||
self.load_accumulator(result);
|
||||
|
||||
debug!("accumulator: {}", self.registers.accumulator);
|
||||
}
|
||||
debug!("accumulator: {}", self.registers.accumulator);
|
||||
}
|
||||
|
||||
fn and(&mut self, value: i8) {
|
||||
let a_after = self.registers.accumulator & value;
|
||||
self.load_accumulator(a_after);
|
||||
}
|
||||
|
||||
fn subtract_with_carry(&mut self, value: i8) {
|
||||
// A - M - (1 - C)
|
||||
fn subtract_with_carry(&mut self, value: i8) {
|
||||
// A - M - (1 - C)
|
||||
|
||||
// nc -- 'not carry'
|
||||
let nc: i8 = if self.registers.status.contains(Status::PS_CARRY) {
|
||||
0
|
||||
} else {
|
||||
1
|
||||
};
|
||||
// nc -- 'not carry'
|
||||
let nc: i8 = if self.registers.status.contains(Status::PS_CARRY) {
|
||||
0
|
||||
} else {
|
||||
1
|
||||
};
|
||||
|
||||
let a_before: i8 = self.registers.accumulator;
|
||||
let a_before: i8 = self.registers.accumulator;
|
||||
|
||||
let a_after = a_before.wrapping_sub(value).wrapping_sub(nc);
|
||||
let a_after = a_before.wrapping_sub(value).wrapping_sub(nc);
|
||||
|
||||
// The overflow flag is set on two's-complement overflow.
|
||||
//
|
||||
// range of A is -128 to 127
|
||||
// range of - M - (1 - C) is -128 to 128
|
||||
// -(127 + 1) to -(-128 + 0)
|
||||
//
|
||||
let over =
|
||||
((nc == 0 && value < 0) || (nc == 1 && value < -1)) && a_before >= 0 && a_after < 0;
|
||||
// The overflow flag is set on two's-complement overflow.
|
||||
//
|
||||
// range of A is -128 to 127
|
||||
// range of - M - (1 - C) is -128 to 128
|
||||
// -(127 + 1) to -(-128 + 0)
|
||||
//
|
||||
let over =
|
||||
((nc == 0 && value < 0) || (nc == 1 && value < -1)) && a_before >= 0 && a_after < 0;
|
||||
|
||||
let under = (a_before < 0) && (-value - nc < 0) && a_after >= 0;
|
||||
let under = (a_before < 0) && (-value - nc < 0) && a_after >= 0;
|
||||
|
||||
let did_overflow = over || under;
|
||||
let did_overflow = over || under;
|
||||
|
||||
let mask = Status::PS_CARRY | Status::PS_OVERFLOW;
|
||||
let mask = Status::PS_CARRY | Status::PS_OVERFLOW;
|
||||
|
||||
let bcd1: i8 = if (a_before & 0x0f).wrapping_sub(nc) < (value & 0x0f) {
|
||||
0x06
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
let bcd1: i8 = if (a_before & 0x0f).wrapping_sub(nc) < (value & 0x0f) {
|
||||
0x06
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
|
||||
let bcd2: i8 = if (a_after.wrapping_sub(bcd1) as u8 & 0xf0) as u8 > 0x90 {
|
||||
0x60
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
let bcd2: i8 = if (a_after.wrapping_sub(bcd1) as u8 & 0xf0) as u8 > 0x90 {
|
||||
0x60
|
||||
} else {
|
||||
0x00
|
||||
};
|
||||
|
||||
let result: i8 = if self.registers.status.contains(Status::PS_DECIMAL_MODE) {
|
||||
a_after.wrapping_sub(bcd1).wrapping_sub(bcd2)
|
||||
} else {
|
||||
a_after
|
||||
};
|
||||
let result: i8 = if self.registers.status.contains(Status::PS_DECIMAL_MODE) {
|
||||
a_after.wrapping_sub(bcd1).wrapping_sub(bcd2)
|
||||
} else {
|
||||
a_after
|
||||
};
|
||||
|
||||
// The carry flag is set on unsigned overflow.
|
||||
let did_carry = (result as u8) > (a_before as u8);
|
||||
// The carry flag is set on unsigned overflow.
|
||||
let did_carry = (result as u8) > (a_before as u8);
|
||||
|
||||
self.registers.status.set_with_mask(
|
||||
mask,
|
||||
Status::new(StatusArgs { carry: did_carry, overflow: did_overflow, ..StatusArgs::none() }),
|
||||
);
|
||||
self.registers.status.set_with_mask(
|
||||
mask,
|
||||
Status::new(StatusArgs {
|
||||
carry: did_carry,
|
||||
overflow: did_overflow,
|
||||
..StatusArgs::none()
|
||||
}),
|
||||
);
|
||||
|
||||
|
||||
self.load_accumulator(result);
|
||||
}
|
||||
self.load_accumulator(result);
|
||||
}
|
||||
|
||||
fn decrement_memory(&mut self, addr: Address) {
|
||||
let value_new = self.memory.get_byte(addr).wrapping_sub(1);
|
||||
@ -779,51 +795,54 @@ mod tests {
|
||||
use super::*;
|
||||
use num::range_inclusive;
|
||||
|
||||
#[test]
|
||||
fn decimal_add_test() {
|
||||
let mut cpu = CPU::new();
|
||||
cpu.registers.status.or(Status::PS_DECIMAL_MODE);
|
||||
#[test]
|
||||
fn decimal_add_test() {
|
||||
let mut cpu = CPU::new();
|
||||
cpu.registers.status.or(Status::PS_DECIMAL_MODE);
|
||||
|
||||
cpu.add_with_carry(0x09);
|
||||
cpu.add_with_carry(0x09);
|
||||
assert_eq!(cpu.registers.accumulator, 0x09);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_CARRY), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_ZERO), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_NEGATIVE), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_OVERFLOW), false);
|
||||
|
||||
cpu.add_with_carry(0x43);
|
||||
cpu.add_with_carry(0x43);
|
||||
assert_eq!(cpu.registers.accumulator, 0x52);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_CARRY), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_ZERO), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_NEGATIVE), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_OVERFLOW), false);
|
||||
|
||||
cpu.add_with_carry(0x48);
|
||||
cpu.add_with_carry(0x48);
|
||||
assert_eq!(cpu.registers.accumulator, 0x00);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_CARRY), true);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_ZERO), true);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_NEGATIVE), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_OVERFLOW), true);
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn decimal_subtract_test() {
|
||||
let mut cpu = CPU::new();
|
||||
cpu.registers.status.or(Status::PS_DECIMAL_MODE);
|
||||
#[test]
|
||||
fn decimal_subtract_test() {
|
||||
let mut cpu = CPU::new();
|
||||
cpu.registers
|
||||
.status
|
||||
.or(Status::PS_DECIMAL_MODE | Status::PS_CARRY);
|
||||
cpu.registers.accumulator = 0;
|
||||
|
||||
cpu.subtract_with_carry(0x48);
|
||||
cpu.subtract_with_carry(0x48);
|
||||
assert_eq!(cpu.registers.accumulator as u8, 0x52);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_CARRY), true);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_ZERO), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_NEGATIVE), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_OVERFLOW), false);
|
||||
|
||||
cpu.subtract_with_carry(0x43);
|
||||
cpu.subtract_with_carry(0x43);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_CARRY), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_ZERO), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_NEGATIVE), false);
|
||||
assert_eq!(cpu.registers.status.contains(Status::PS_OVERFLOW), false);
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn add_with_carry_test() {
|
||||
@ -1342,5 +1361,11 @@ mod tests {
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn stack_underflow() {
|
||||
let mut cpu = CPU::new();
|
||||
let _val: u8 = cpu.pull_from_stack();
|
||||
}
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user