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refactor sbc_bin

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This commit is contained in:
Franco Colmenarez
2022-11-21 18:26:55 -05:00
parent 6706daa872
commit 992112229e
2 changed files with 13 additions and 37 deletions
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snes-core/src/cpu/instructions.rs
+2 -2
View File
@@ -70,7 +70,7 @@ impl CPU {
let value = self.get_8bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero) = match is_decimal_mode {
true => alu::sbc8bcd(target as u8, value, carry_flag),
false => alu::sbc8bin(target as u8, value, carry_flag),
false => alu::sbc_bin(target as u8, value, carry_flag),
};
self.registers.set_low_a(result as u8);
self.registers.set_carry_flag(is_carry);
@@ -81,7 +81,7 @@ impl CPU {
let value = self.get_16bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero) = match is_decimal_mode {
true => alu::sbc16bcd(target, value, carry_flag),
false => alu::sbc16bin(target, value, carry_flag),
false => alu::sbc_bin(target, value, carry_flag),
};
self.registers.a = result;
self.registers.set_carry_flag(is_carry);
snes-core/src/utils/alu.rs
+11 -35
View File
@@ -46,35 +46,11 @@ pub fn adc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool)
(result, is_carry, is_negative, is_zero)
}
pub fn sbc8bin(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
let is_carry = match target.checked_sub(value) {
None => true,
Some(res) => match res.checked_sub(carry as u8) {
None => true,
Some(_) => false,
},
};
let result = target
.wrapping_sub(value)
.wrapping_sub(carry as u8);
let is_negative = (result >> 7) == 1;
let is_zero = result == 0;
(result, is_carry, is_negative, is_zero)
}
pub fn sbc16bin(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
let is_carry = match target.checked_sub(value) {
None => true,
Some(res) => match res.checked_sub(carry as u16) {
None => true,
Some(_) => false,
},
};
let result = target
.wrapping_sub(value)
.wrapping_sub(carry as u16);
let is_negative = (result >> 15) == 1;
let is_zero = result == 0;
pub fn sbc_bin<T: SnesNum>(target: T, value: T, carry: bool) -> (T, bool, bool, bool) {
let is_carry = target.sub_will_carry(value, carry);
let result = target.sub_snes(value, carry);
let is_negative = result.is_negative();
let is_zero = result.is_zero();
(result, is_carry, is_negative, is_zero)
}
@@ -321,19 +297,19 @@ mod alu_tests {
#[test]
fn test_dec8bin() {
let (result, carry, negative, zero) = sbc8bin(1, 1, false);
let (result, carry, negative, zero) = sbc_bin(1_u8, 1_u8, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = sbc8bin(0, 1, false);
let (result, carry, negative, zero) = sbc_bin(0_u8, 1_u8, false);
assert_eq!(result, 0b11111111);
assert_eq!(carry, true);
assert_eq!(negative, true);
assert_eq!(zero, false);
let (result, carry, negative, zero) = sbc8bin(0, 1, true);
let (result, carry, negative, zero) = sbc_bin(0_u8, 1_u8, true);
assert_eq!(result, 0b11111110);
assert_eq!(carry, true);
assert_eq!(negative, true);
@@ -342,19 +318,19 @@ mod alu_tests {
#[test]
fn test_dec16bin() {
let (result, carry, negative, zero) = sbc16bin(1, 1, false);
let (result, carry, negative, zero) = sbc_bin(1_u16, 1_u16, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = sbc16bin(0, 1, false);
let (result, carry, negative, zero) = sbc_bin(0_u16, 1_u16, false);
assert_eq!(result, 0b11111111_11111111);
assert_eq!(carry, true);
assert_eq!(negative, true);
assert_eq!(zero, false);
let (result, carry, negative, zero) = sbc16bin(0, 1, true);
let (result, carry, negative, zero) = sbc_bin(0_u16, 1_u16, true);
assert_eq!(result, 0b11111111_11111110);
assert_eq!(carry, true);
assert_eq!(negative, true);