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Refactor BCD operations

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This commit is contained in:
Franco Colmenarez
2022-11-23 21:07:57 -05:00
parent d0e02cd9cd
commit fa230e4a52
3 changed files with 103 additions and 101 deletions
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snes-core/src/cpu/instructions.rs
+4 -4
View File
@@ -35,7 +35,7 @@ impl CPU {
true => {
let value = self.get_8bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero, is_overflow) = match is_decimal_mode {
true => alu::adc8bcd(target as u8, value, carry_flag),
true => alu::adc_bcd(target as u8, value, carry_flag),
false => alu::adc_bin(target as u8, value, carry_flag),
};
self.registers.set_low_a(result as u8);
@@ -47,7 +47,7 @@ impl CPU {
false => {
let value = self.get_16bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero, is_overflow) = match is_decimal_mode {
true => alu::adc16bcd(target, value, carry_flag),
true => alu::adc_bcd(target, value, carry_flag),
false => alu::adc_bin(target, value, carry_flag),
};
self.registers.a = result;
@@ -71,7 +71,7 @@ impl CPU {
true => {
let value = self.get_8bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero, is_overflow) = match is_decimal_mode {
true => alu::sbc8bcd(target as u8, value, carry_flag),
true => alu::sbc_bcd(target as u8, value, carry_flag),
false => alu::sbc_bin(target as u8, value, carry_flag),
};
self.registers.set_low_a(result as u8);
@@ -83,7 +83,7 @@ impl CPU {
false => {
let value = self.get_16bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero, is_overflow) = match is_decimal_mode {
true => alu::sbc16bcd(target, value, carry_flag),
true => alu::sbc_bcd(target, value, carry_flag),
false => alu::sbc_bin(target, value, carry_flag),
};
self.registers.a = result;
snes-core/src/utils/alu.rs
+76 -94
View File
@@ -9,41 +9,39 @@ pub fn adc_bin<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool,
(result, is_carry, is_negative, is_zero, is_overflow)
}
pub fn adc8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool, bool) {
pub fn adc_bcd<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool, bool, bool) {
let original_target = value;
let original_value = value;
let nibble_bytes = target.bytes() * 2;
let mut is_carry = carry;
let mut result = (target & 0xF) + (value & 0xF) + (is_carry as u8);
if result > 9 {
result += 6;
}
result += (target & 0xF0) + (value & 0xF0);
if result > 0x9F {
result += 0x60;
}
is_carry = result > 0x9F;
let is_negative = (result >> 7) == 1;
let is_zero = result == 0;
let is_overflow = target.is_overflow(value, result);
(result, is_carry, is_negative, is_zero, is_overflow)
}
let target = target.to_u32();
let value = value.to_u32();
let mut result = 0;
pub fn adc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool, bool) {
let mut is_carry = carry;
let mut result = (target & 0xF) + (value & 0xF) + (is_carry as u16);
if result > 9 {
result += 6;
let mut value_mask = 0x0F;
let mut result_mask = 0x00;
let mut carry_compare = 0x09;
let mut bcd_six_add = 0x06;
let mut carry_shift = 0;
for _ in 0..nibble_bytes {
result = (target & value_mask) + (value & value_mask) + ((is_carry as u32) << carry_shift) + (result & result_mask);
if result > carry_compare {
result = result.wrapping_add(bcd_six_add);
}
is_carry = result > carry_compare;
value_mask <<= 4;
bcd_six_add <<= 4;
carry_shift += 4;
result_mask = (result_mask << 4) | 0xF;
carry_compare = (carry_compare << 4) | 0xF;
}
result += (target & 0xF0) + (value & 0xF0);
if result > 0x9F {
result += 0x60;
}
result += (target & 0xF00) + (value & 0xF00);
if result > 0x9FF {
result += 0x600;
}
is_carry = result > 0x9FFF;
let is_negative = (result >> 15) == 1;
let is_zero = result == 0;
(result, is_carry, is_negative, is_zero, false) // TODO: return overflow
let result = T::from_u32(result);
let is_negative = result.is_negative();
let is_zero = result.is_zero();
let is_overflow = original_target.is_overflow(original_value, result);
(result, is_carry, is_negative, is_zero, is_overflow)
}
pub fn sbc_bin<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool, bool, bool) {
@@ -55,55 +53,39 @@ pub fn sbc_bin<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool,
(result, is_carry, is_negative, is_zero, is_overflow)
}
pub fn sbc8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool, bool) {
pub fn sbc_bcd<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool, bool, bool) {
let original_target = value;
let original_value = value;
let nibble_bytes = target.bytes() * 2;
let mut is_carry = carry;
let target = target as u16;
let value = !(value as u16);
let mut result = (target & 0x0F) + (value & 0x0F) + (is_carry as u16);
if result <= 0x0F {
result = result.wrapping_sub(0x06);
}
is_carry = result > 0x0F;
result = (target & 0xF0) + (value & 0xF0) + ((is_carry as u16) << 4) + (result & 0x0F);
if result <= 0xFF {
result = result.wrapping_sub(0x60);
}
is_carry = result > 0xFF;
let result = result as u8;
let is_negative = (result >> 7) == 1;
let is_zero = result == 0;
(result, is_carry, is_negative, is_zero, false) // TODO: return overflow
}
let target = target.to_u32();
let value = value.invert().to_u32();
let mut result = 0;
pub fn sbc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool, bool) {
let mut is_carry = carry;
let target = target as u32;
let value = !(value as u32);
let mut result = ((target & 0x0F) + (value & 0x0F) + (is_carry as u32)) as u32;
if result <= 0x0F {
result = result.wrapping_sub(0x06);
}
is_carry = result > 0xF;
result = (target & 0xF0) + (value & 0xF0) + ((is_carry as u32) << 4) + (result & 0xF);
if result <= 0xFF {
result = result.wrapping_sub(0x60);
}
is_carry = result > 0xFF;
result = (target & 0xF00) + (value & 0xF00) + ((is_carry as u32) << 8) + (result & 0xFF);
if result <= 0xFFF {
result = result.wrapping_sub(0x600);
}
is_carry = result > 0xFFF;
result = (target & 0xF000) + (value & 0xF000) + ((is_carry as u32) << 12) + (result & 0xFFF);
if result <= 0xFFFF {
result = result.wrapping_sub(0x6000);
let mut value_mask = 0x0F;
let mut result_mask = 0x00;
let mut carry_compare = 0x0F;
let mut bcd_six_sub = 0x06;
let mut carry_shift = 0;
for _ in 0..nibble_bytes {
result = (target & value_mask) + (value & value_mask) + ((is_carry as u32) << carry_shift) + (result & result_mask);
if result <= carry_compare {
result = result.wrapping_sub(bcd_six_sub);
}
is_carry = result > carry_compare;
value_mask <<= 4;
bcd_six_sub <<= 4;
carry_shift += 4;
result_mask = (result_mask << 4) | 0xF;
carry_compare = (carry_compare << 4) | 0xF;
}
is_carry = result > 0xFFFF;
let result = result as u16;
let is_negative = (result >> 15) == 1;
let is_zero = result == 0;
(result, is_carry, is_negative, is_zero, false) // TODO: return overflow
let result = T::from_u32(result);
let is_negative = result.is_negative();
let is_zero = result.is_zero();
let is_overflow = original_target.is_overflow(original_value, result);
(result, is_carry, is_negative, is_zero, is_overflow)
}
pub fn and<T: SnesNum>(target: T, value: T) -> (T, bool, bool) {
@@ -210,42 +192,42 @@ mod alu_tests {
#[test]
fn test_adc_bcd() {
// 8 bits
let (result, carry, negative, zero, overflow) = adc8bcd(5, 5, false);
let (result, carry, negative, zero, overflow) = adc_bcd(5_u8, 5_u8, false);
assert_eq!(result, 0b0001_0000);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc8bcd(7, 9, false);
let (result, carry, negative, zero, overflow) = adc_bcd(7_u8, 9_u8, false);
assert_eq!(result, 0b0001_0110);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc8bcd(5, 4, true);
let (result, carry, negative, zero, overflow) = adc_bcd(5_u8, 4_u8, true);
assert_eq!(result, 0b0001_0000);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc8bcd(7, 8, true);
let (result, carry, negative, zero, overflow) = adc_bcd(7_u8, 8_u8, true);
assert_eq!(result, 0b0001_0110);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc8bcd(0, 0, false);
let (result, carry, negative, zero, overflow) = adc_bcd(0_u8, 0_u8, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc8bcd(0b0001_1001, 0b0010_1000, false);
let (result, carry, negative, zero, overflow) = adc_bcd(0b0001_1001_u8, 0b0010_1000_u8, false);
assert_eq!(result, 0b0100_0111);
assert_eq!(carry, false);
assert_eq!(negative, false);
@@ -253,49 +235,49 @@ mod alu_tests {
assert_eq!(overflow, false);
// 16 bits
let (result, carry, negative, zero, overflow) = adc16bcd(5, 5, false);
let (result, carry, negative, zero, overflow) = adc_bcd(5_u16, 5_u16, false);
assert_eq!(result, 0b0001_0000);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(7, 9, false);
let (result, carry, negative, zero, overflow) = adc_bcd(7_u16, 9_u16, false);
assert_eq!(result, 0b0001_0110);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(5, 4, true);
let (result, carry, negative, zero, overflow) = adc_bcd(5_u16, 4_u16, true);
assert_eq!(result, 0b0001_0000);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(7, 8, true);
let (result, carry, negative, zero, overflow) = adc_bcd(7_u16, 8_u16, true);
assert_eq!(result, 0b0001_0110);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(0, 0, false);
let (result, carry, negative, zero, overflow) = adc_bcd(0_u16, 0_u16, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(0x0500, 0x0500, false);
let (result, carry, negative, zero, overflow) = adc_bcd(0x0500_u16, 0x0500_u16, false);
assert_eq!(result, 0b0001_0000_0000_0000);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = adc16bcd(0b0001_1001, 0b0010_1000, false);
let (result, carry, negative, zero, overflow) = adc_bcd(0b0001_1001_u16, 0b0010_1000_u16, false);
assert_eq!(result, 0b0100_0111);
assert_eq!(carry, false);
assert_eq!(negative, false);
@@ -353,14 +335,14 @@ mod alu_tests {
#[test]
fn test_dec_bcd() {
// 8 bit
let (result, carry, negative, zero, overflow) = sbc8bcd(0x49, 0x48, false);
let (result, carry, negative, zero, overflow) = sbc_bcd(0x49_u8, 0x48_u8, false);
assert_eq!(result, 0x00);
assert_eq!(carry, true);
assert_eq!(negative, false);
assert_eq!(zero, true);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = sbc8bcd(0x49, 0x50, true);
let (result, carry, negative, zero, overflow) = sbc_bcd(0x49_u8, 0x50_u8, true);
assert_eq!(result, 0x99);
assert_eq!(carry, false);
assert_eq!(negative, true);
@@ -368,14 +350,14 @@ mod alu_tests {
assert_eq!(overflow, false);
// 16 bit
let (result, carry, negative, zero, overflow) = sbc16bcd(0x4999, 0x4998, false);
let (result, carry, negative, zero, overflow) = sbc_bcd(0x4999_u16, 0x4998_u16, false);
assert_eq!(result, 0x0000);
assert_eq!(carry, true);
assert_eq!(negative, false);
assert_eq!(zero, true);
assert_eq!(overflow, false);
let (result, carry, negative, zero, overflow) = sbc16bcd(0x4999, 0x5000, true);
let (result, carry, negative, zero, overflow) = sbc_bcd(0x4999_u16, 0x5000_u16, true);
assert_eq!(result, 0x9999);
assert_eq!(carry, false);
assert_eq!(negative, true);
snes-core/src/utils/num_trait.rs
+23 -3
View File
@@ -8,6 +8,10 @@ pub trait SnesNum: Copy + Clone + Sized + Eq + PartialEq {
fn asl(&self) -> Self;
fn is_negative(&self) -> bool;
fn is_zero(&self) -> bool;
fn to_u32(&self) -> u32;
fn from_u32(v: u32) -> Self;
fn invert(&self) -> Self;
fn bytes(&self) -> usize;
}
macro_rules! define_will_carry {
@@ -44,7 +48,7 @@ macro_rules! define_is_overflow {
}
macro_rules! define_impl {
($t:ty) => {
($t:ty, $bytes:literal) => {
impl SnesNum for $t {
define_will_carry!($t, add_will_carry, checked_add);
define_will_carry!($t, sbc_will_carry, checked_sub);
@@ -69,9 +73,25 @@ macro_rules! define_impl {
fn is_zero(&self) -> bool {
(*self) == 0
}
fn to_u32(&self) -> u32 {
(* self) as u32
}
fn from_u32(v: u32) -> $t {
v as $t
}
fn invert(&self) -> $t {
!(* self)
}
fn bytes(&self) -> usize {
$bytes
}
}
};
}
define_impl!(u8);
define_impl!(u16);
define_impl!(u8, 1);
define_impl!(u16, 2);