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Fix bcd additions

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This commit is contained in:
Franco Colmenarez
2022-10-13 12:07:58 -05:00
parent e1f9542cca
commit 391e29c365
1 changed files with 20 additions and 20 deletions
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snes-core/src/utils/alu.rs
+20 -20
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@@ -33,15 +33,14 @@ pub fn adc16bin(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool)
pub fn adc8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
let mut is_carry = carry;
let mut result = (target & 0xF) + (value & 0xF) + (is_carry as u8);
is_carry = result > 9;
if is_carry {
if result > 9 {
result += 6;
}
result = (result & 0xF0) + (target & 0xF0) + (value & 0xF0) + ((is_carry as u8) << 4);
is_carry = result > 0x9F;
if is_carry {
result = result.wrapping_add(0x60);
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;
(result, is_carry, is_negative, is_zero)
@@ -50,29 +49,18 @@ pub fn adc8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
pub fn adc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
let mut is_carry = carry;
let mut result = (target & 0xF) + (value & 0xF) + (is_carry as u16);
is_carry = false;
if result > 9 {
result += 6;
is_carry = true;
}
result = (result & 0xF0) + (target & 0xF0) + (value & 0xF0) + ((is_carry as u16) << 4);
is_carry = false;
result += (target & 0xF0) + (value & 0xF0);
if result > 0x9F {
result += 0x60;
is_carry = true;
}
result = (result & 0xF00) + (target & 0xF00) + (value & 0xF00) + ((is_carry as u16) << 8);
is_carry = false;
result += (target & 0xF00) + (value & 0xF00);
if result > 0x9FF {
result += 0x600;
is_carry = true;
}
result = (result & 0xF000) + (target & 0xF000) + (target & 0xF000) + ((is_carry as u16) << 12);
is_carry = false;
if result > 0x9FFF {
result += 0x6000;
is_carry = true;
}
is_carry = result > 0x9FFF;
let is_negative = (result >> 15) == 1;
let is_zero = result == 0;
(result, is_carry, is_negative, is_zero)
@@ -180,6 +168,12 @@ mod alu_tests {
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = adc8bcd(0b0001_1001, 0b0010_1000, false);
assert_eq!(result, 0b0100_0111);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
}
#[test]
@@ -219,5 +213,11 @@ mod alu_tests {
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
let (result, carry, negative, zero) = adc16bcd(0b0001_1001, 0b0010_1000, false);
assert_eq!(result, 0b0100_0111);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, false);
}
}