squash some bugs and pass test rom #4

pcasaretto · Apr 26, 2024 · 1b17f77 · 1b17f77
1 parent 1badc3a
commit 1b17f77
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Showing 5 changed files with 119 additions and 24 deletions.
diff --git a/src/instructions/adc.rs b/src/instructions/adc.rs
@@ -21,18 +21,19 @@ pub fn adc(target: RegisterTarget) -> impl Fn(&mut Gameboy) -> u8 {
 }
 
 pub fn adc_n8(gameboy: &mut Gameboy) -> u8 {
-    let mut addend = gameboy.read_next_byte();
+    let addend = gameboy.read_next_byte();
     let current_value = gameboy.cpu.registers.a;
-    if gameboy.cpu.registers.f.carry {
-        addend += 1;
-    }
-    let (new_value, did_overflow) = current_value.overflowing_add(addend);
-    gameboy.cpu.registers.a = new_value;
 
-    gameboy.cpu.registers.f.carry = did_overflow;
+    let carry_in = if gameboy.cpu.registers.f.carry { 1 } else { 0 };
+    let new_value = current_value.wrapping_add(addend).wrapping_add(carry_in);
+    let carry = (current_value as u16 + addend as u16 + carry_in as u16) > 0xFF;
+    let half_carry = ((current_value & 0xF) + (addend & 0xF) + carry_in) > 0xF;
+
+    gameboy.cpu.registers.a = new_value;
+    gameboy.cpu.registers.f.carry = carry;
     gameboy.cpu.registers.f.subtract = false;
     gameboy.cpu.registers.f.zero = new_value == 0;
-    gameboy.cpu.registers.f.half_carry = (current_value & 0xF) + (addend & 0xF) > 0xF;
+    gameboy.cpu.registers.f.half_carry = half_carry;
     const TICKS: u8 = 8;
     TICKS
 }
@@ -307,4 +308,27 @@ mod tests {
         adc_mem_at_hl(&mut gameboy);
         assert!(gameboy.cpu.registers.f.half_carry);
     }
+
+    #[test]
+    fn test_adc_n8_half_carry_flag() {
+        let mut gameboy = Gameboy::default();
+        gameboy.cpu.registers.pc = 0xC050;
+        gameboy.cpu.registers.a = 0x00;
+        gameboy.bus.write_byte(0xC051, 0x0F);
+        gameboy.cpu.registers.f.carry = true;
+        adc_n8(&mut gameboy);
+        gameboy.cpu.registers.a = 0x10;
+        assert!(gameboy.cpu.registers.f.half_carry);
+    }
+
+    #[test]
+    fn test_adc_n8_half_carry_flag_2() {
+        let mut gameboy = Gameboy::default();
+        gameboy.cpu.registers.pc = 0xC050;
+        gameboy.cpu.registers.a = 0xFF;
+        gameboy.bus.write_byte(0xC051, 0x01);
+        adc_n8(&mut gameboy);
+        gameboy.cpu.registers.a = 0x00;
+        assert!(gameboy.cpu.registers.f.half_carry);
+    }
 }
diff --git a/src/instructions/add.rs b/src/instructions/add.rs
@@ -64,6 +64,31 @@ pub fn add_hl_r16(target: Register16bTarget) -> impl Fn(&mut Gameboy) -> u8 {
     }
 }
 
+pub fn add_sp_n8(gameboy: &mut Gameboy) -> u8 {
+    let n8 = gameboy.read_next_byte() as i8;
+    let sp = gameboy.cpu.registers.sp;
+
+    let (result, carry, half_carry) = if n8 < 0 {
+        let t = n8.abs() as u16;
+        let carry = false;
+        let half_carry = false;
+        (sp.wrapping_sub(t), carry, half_carry)
+    } else {
+        let carry = sp as u8 > 0xFF - n8 as u8;
+        let half_carry = sp as u8 & 0xF + n8 as u8 & 0xF > 0xF;
+        (sp.wrapping_add(n8 as u16), carry, half_carry)
+    };
+
+    gameboy.cpu.registers.sp = result;
+
+    gameboy.cpu.registers.f.zero = false;
+    gameboy.cpu.registers.f.subtract = false;
+    gameboy.cpu.registers.f.half_carry = half_carry;
+    gameboy.cpu.registers.f.carry = carry;
+    const TICKS: u8 = 16;
+    TICKS
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

diff --git a/src/instructions/ld.rs b/src/instructions/ld.rs
@@ -209,8 +209,8 @@ pub fn ld_hl_sp_n8(gameboy: &mut Gameboy) -> u8 {
 
     let (result, carry, half_carry) = if n < 0 {
         let t = n.abs() as u16;
-        let carry = sp <= t;
-        let half_carry = (sp & 0xF) <= (t & 0xF);
+        let carry = false;
+        let half_carry = false;
         (sp.wrapping_sub(t), carry, half_carry)
     } else {
         let carry = sp as u8 > 0xFF - n as u8;
@@ -261,6 +261,12 @@ mod tests {
 
         gameboy.cpu.registers.pc = 0xC050;
         gameboy.cpu.registers.sp = 0xDFFD;
+        gameboy.bus.write_byte(0xC051, 0x03);
+        ld_hl_sp_n8(&mut gameboy);
+        assert!(gameboy.cpu.registers.f.carry);
+
+        gameboy.cpu.registers.pc = 0xC050;
+        gameboy.cpu.registers.sp = 0xDF01;
         gameboy.bus.write_byte(0xC051, 0xFE);
         ld_hl_sp_n8(&mut gameboy);
         assert!(gameboy.cpu.registers.f.carry);

diff --git a/src/instructions/mod.rs b/src/instructions/mod.rs
@@ -308,6 +308,7 @@ pub fn from_byte(byte: u8) -> Box<Instruction> {
         0xF3 => Box::new(pai(int::di)),
         0xFB => Box::new(pai(int::ei)),
 
+        0xE8 => Box::new(pai(add::add_sp_n8)),
         0xF8 => Box::new(pai(ld::ld_hl_sp_n8)),
         0xF9 => Box::new(pai(ld::ld_sp_hl)),
 

diff --git a/src/instructions/sbc.rs b/src/instructions/sbc.rs
@@ -21,19 +21,20 @@ pub fn sbc_r_r_a(target: RegisterTarget) -> impl Fn(&mut Gameboy) -> u8 {
 }
 
 pub fn sbc_n8(gameboy: &mut Gameboy) -> u8 {
-    let addr = gameboy.cpu.registers.get_u16(Register16bTarget::PC);
-    let mut d8 = gameboy.bus.read_byte(addr);
-    if gameboy.cpu.registers.f.carry {
-        d8 += 1;
-    }
+    let operand = gameboy.read_next_byte();
     let current_value = gameboy.cpu.registers.get_u8(RegisterTarget::A);
-    let (new_value, did_overflow) = current_value.overflowing_sub(d8);
+
+    let borrow_in = if gameboy.cpu.registers.f.carry { 1 } else { 0 };
+    let (new_value, first_overflow) = current_value.overflowing_sub(operand);
+    let (new_value, second_overflow) = new_value.overflowing_sub(borrow_in);
+    let half_borrow = (current_value & 0xF) < (operand & 0xF) + borrow_in;
+
     gameboy.cpu.registers.a = new_value;
 
-    gameboy.cpu.registers.f.carry = did_overflow;
+    gameboy.cpu.registers.f.carry = first_overflow || second_overflow;
     gameboy.cpu.registers.f.zero = new_value == 0;
     gameboy.cpu.registers.f.subtract = true;
-    gameboy.cpu.registers.f.half_carry = (current_value & 0xF) < (d8 & 0xF);
+    gameboy.cpu.registers.f.half_carry = half_borrow;
     const TICKS: u8 = 8;
     TICKS
 }
@@ -178,7 +179,7 @@ mod tests {
             cpu: CPU {
                 registers: Registers {
                     a: 4,
-                    pc: 0xC051,
+                    pc: 0xC050,
                     f: FlagsRegister::from(0),
                     ..Default::default()
                 },
@@ -196,7 +197,7 @@ mod tests {
         let mut gameboy = Gameboy {
             cpu: CPU {
                 registers: Registers {
-                    pc: 0xC051,
+                    pc: 0xC050,
                     a: 4,
                     f: FlagsRegister::from(0),
                     ..Default::default()
@@ -216,7 +217,7 @@ mod tests {
             cpu: CPU {
                 registers: Registers {
                     a: 4,
-                    pc: 0xC051,
+                    pc: 0xC050,
                     f: FlagsRegister::from(0),
                     ..Default::default()
                 },
@@ -229,12 +230,50 @@ mod tests {
         assert!(gameboy.cpu.registers.f.carry);
     }
 
+    #[test]
+    fn test_sbc_n8_carry_flag_2() {
+        let mut gameboy = Gameboy {
+            cpu: CPU {
+                registers: Registers {
+                    a: 0,
+                    pc: 0xC050,
+                    f: FlagsRegister::from(0),
+                    ..Default::default()
+                },
+                ..Default::default()
+            },
+            ..Default::default()
+        };
+        gameboy.bus.memory[0xC051] = 0xF0;
+        sbc_n8(&mut gameboy);
+        assert!(gameboy.cpu.registers.f.carry);
+    }
+
+    #[test]
+    fn test_sbc_n8_carry_flag_3() {
+        let mut gameboy = Gameboy {
+            cpu: CPU {
+                registers: Registers {
+                    a: 0,
+                    pc: 0xC050,
+                    f: FlagsRegister::from(0b0010000),
+                    ..Default::default()
+                },
+                ..Default::default()
+            },
+            ..Default::default()
+        };
+        gameboy.bus.memory[0xC051] = 0xFF;
+        sbc_n8(&mut gameboy);
+        assert!(gameboy.cpu.registers.f.carry);
+    }
+
     #[test]
     fn test_sbc_n8_zero_flag() {
         let mut gameboy = Gameboy {
             cpu: CPU {
                 registers: Registers {
-                    pc: 0xC051,
+                    pc: 0xC050,
                     a: 5,
                     f: FlagsRegister::from(0),
                     ..Default::default()
@@ -253,7 +292,7 @@ mod tests {
         let mut gameboy = Gameboy {
             cpu: CPU {
                 registers: Registers {
-                    pc: 0xC051,
+                    pc: 0xC050,
                     a: 5,
                     f: FlagsRegister::from(0),
                     ..Default::default()
@@ -272,7 +311,7 @@ mod tests {
         let mut gameboy = Gameboy {
             cpu: CPU {
                 registers: Registers {
-                    pc: 0xC051,
+                    pc: 0xC050,
                     a: 0b00010000,
                     f: FlagsRegister::from(0),
                     ..Default::default()