implement more inc/dec variants and conditional jump

src/emu.rs

@@ -21,6 +21,44 @@ pub struct GameBoy {
     bp_manager: BreakPointManager,
 }
 
+fn add(a: u8, b: u8) -> u8 {
+    if std::u8::MAX - b < a {
+        ((a as u16 + b as u16) - std::u8::MAX as u16) as u8 - 1
+    } else {
+        a + b
+    }
+}
+
+fn sub(a: u8, b: u8) -> u8 {
+    if a < b {
+        std::u8::MAX - (b - a) + 1
+    } else {
+        a - b
+    }
+}
+
+fn add_inplace(a: &mut u8, b: u8) {
+    *a = add(*a, b)
+}
+
+fn sub_inplace(a: &mut u8, b: u8) {
+    *a = sub(*a, b)
+}
+
+enum Flag {
+    Z, N, H ,CY
+}
+
+fn flag_set(f: Flag, v: u8) -> bool {
+    use Flag::*;
+    match f {
+        Z  => v << 0 >> 7 == 1,
+        N  => v << 1 >> 6 == 1,
+        H  => v << 2 >> 5 == 1,
+        CY => v << 3 >> 4 == 1,
+    }
+}
+
 impl GameBoy {
     pub fn new() -> GameBoy {
         GameBoy {
@@ -34,10 +72,23 @@ impl GameBoy {
         }
     }
 
+
     fn set(adr: u16, val: u8) {
         // check for special registers
     }
 
+    fn set_flag(&mut self, f: Flag, v: bool) {
+        let r = &mut self.reg[Register::F];
+        let v = v as u8;
+        use Flag::*;
+        match f {
+            Z  => *r = v << 7,
+            N  => *r = v << 6,
+            H  => *r = v << 5,
+            CY => *r = v << 4
+        }
+    }
+
     fn set_fast(adr: u16, val: u8) {
         // no checks for special registers
     }
@@ -157,8 +208,8 @@ impl GameBoy {
 
         match postOp {
             PostOp::None => (),
-            PostOp::Inc(reg) => self.reg[reg] += 1,
-            PostOp::Dec(reg) => self.reg[reg] -= 1,
+            PostOp::Inc(reg) => add_inplace(&mut self.reg[reg], 1),
+            PostOp::Dec(reg) => sub_inplace(&mut self.reg[reg], 1),
         }
     }
 
@@ -241,16 +292,34 @@ impl GameBoy {
                 let new_pc = self.read16(pc+1);
                 self.pc = new_pc;
                 println!("jp {pc:#06x}->{new_pc:#06x}");
+                // TODO remember cycle count!
                 return;
             }
-            Jr => {
+            Jr(cond) => {
+                let jump = match cond {
+                    JmpCond::None => true,
+                    JmpCond::Flags(f) => {
+                        let reg_f = self.reg[Register::F];
+                        match f {
+                            0b00 => !flag_set(Flag::Z,  reg_f),
+                            0b01 =>  flag_set(Flag::Z,  reg_f),
+                            0b10 => !flag_set(Flag::CY, reg_f),
+                            0b11 =>  flag_set(Flag::CY, reg_f),
+                            _ => panic!("invalid jump condition")
+                        }
+                    }
+                };
+
+                if jump {
                     let e = self.mem[pc + 1] as i8 + 2;
                     let old_pc = self.pc;
                     let new_pc = (old_pc as i16 + e as i16) as u16;
                     self.pc = new_pc;
                     println!("jr {new_pc:#06x} <- {old_pc:#06x} + {e}");
+                    // TODO remember cycle count 3 for jump, 2 for not!!!
                     return;
                 }
+            }
             Call => {
                 let sp = self.sp as usize;
                 self.mem[sp - 1] = ((pc+op.offs) >> 8) as u8;
@@ -284,15 +353,21 @@ impl GameBoy {
                 self.sp += 2;
                 println!("pop Reg({reg:#04b})");
             }
-            Inc(reg) => { 
-                self.reg[reg] += 1;
-                println!("Inc Reg({reg:#04b})");
+            Inc(dst) => { 
+                match dst {
+                    ValSrc::Reg(reg) => add_inplace(&mut self.reg[reg], 1),
+                    _ => todo!()
                 }
-            Dec(reg) => {
-                self.reg[reg as usize] -= 1;
-                println!("Dec Reg({reg:#04b})");
+                println!("Inc {dst:?}");
             }
-            Ld(dst, src, postOp) => self.op_ld(dst, src, postOp),
+            Dec(dst) => {
+                match dst {
+                    ValSrc::Reg(reg) => sub_inplace(&mut self.reg[reg], 1),
+                    _ => todo!()
+                }
+                println!("Dec {dst:?}");
+            }
+            Ld(dst, src, post_op) => self.op_ld(dst, src, post_op),
             Ld16(dst, src) => self.op_ld16(dst, src),
             Bit(bit_op, src) => {
                 let v = match src {
@@ -324,3 +399,28 @@ impl GameBoy {
         self.pc = pc as u16;
     }
 }
+
+#[cfg(test)]
+mod tests {
+    // #[test]
+    // fn add_overflow() {
+    //     use crate::emu::add;
+    //     assert_eq!(add(1, 1), 2);
+
+    //     assert_eq!(add(std::u8::MAX, 1), 0);
+    //     assert_eq!(add(std::u8::MAX, 2), 1);
+    //     assert_eq!(add(1, std::u8::MAX), 0);
+
+    //     assert_eq!(add(std::u8::MAX - 3, 3), std::u8::MAX);
+    //     assert_eq!(add(3, std::u8::MAX - 3), std::u8::MAX);
+    // }
+
+    // #[test]
+    // fn sub_underflow() {
+    //     use crate::emu::sub;
+    //     assert_eq!(sub(1, 1), 0);
+    //     assert_eq!(sub(1, 2), std::u8::MAX);
+    //     assert_eq!(sub(1, 3), std::u8::MAX - 1);
+    // }
+}
+

src/op.rs

@@ -26,8 +26,8 @@ pub enum Instr {
 
     // Arith
     // TODO can we do Inc16/Inc8 with one via Register::WIDE
-    Inc(Register),
-    Dec(Register),
+    Inc(ValSrc),
+    Dec(ValSrc),
     Bit(BitOp, ValSrc),
 
     // CPU ctl
@@ -35,7 +35,7 @@ pub enum Instr {
 
     // Jump
     Jp,
-    Jr,
+    Jr(JmpCond),
     Call,
     Ret,
 }
@@ -61,6 +61,12 @@ pub enum ValSrc {
     Direct,
 }
 
+#[derive(Debug)]
+pub enum JmpCond {
+    None,
+    Flags(u8)
+}
+
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub enum Register {
     A, F,
@@ -195,7 +201,7 @@ impl TryFrom<u8> for Operation {
         let (inst, cycl, offs) = match value {
             0b00_000_000 => (Nop, 1, 1),
             0b11_000_011 => (Jp, 4, 3),
-            0b00_011_000 => (Jr, 3, 2),
+            0b00_011_000 => (Jr(JmpCond::None), 3, 2),
             0b11_001_101 => (Call, 6, 3),
             0b11_001_001 => (Ret, 4, 1),
             0b11_110_011 => (Di, 1, 1),
@@ -217,6 +223,10 @@ impl TryFrom<u8> for Operation {
             0b11_110_110 => (Bit(Or, Direct), 2, 2), // TODO can bit be grouped via HD & T2?
             0b11_101_110 => (Bit(Xor, Direct), 2, 2),
             0b11_100_110 => (Bit(And, Direct), 2, 2),
+            _ if value & (HD_MSK | 0b100_000 | T2_MSK) == 0b00_100_000 => {
+                let cc = (value & 0b11_000) >> 3;
+                (Jr(JmpCond::Flags(cc)), 3, 2) // TODO cycle can be 2 or 3!
+            }
             _ if (value & (HD_MSK | T1_MSK) == 0b10_110_000) => {
                 (Bit(Or, Reg(Register::try_from(value & 0b111)?)), 1, 1)
             }
@@ -227,10 +237,24 @@ impl TryFrom<u8> for Operation {
                 (Bit(And, Reg(Register::try_from(value & 0b111)?)), 1, 1)
             }
             _ if (value & (HD_MSK | 0b1_000 | T2_MSK) == 0b00_000_011) => {
-                (Inc(Register::from16_rep(payload(value))), 2, 1)
+                (Inc(Reg(Register::from16_rep(payload(value)))), 2, 1)
             }
             _ if (value & (HD_MSK | 0b1_000 | T2_MSK) == 0b00_001_011) => {
-                (Dec(Register::from16_rep(payload(value))), 2, 1)
+                (Dec(Reg(Register::from16_rep(payload(value)))), 2, 1)
+            }
+            _ if (value & (HD_MSK | T2_MSK) == 0b00_000_100) => {
+                if (T1_MSK & value) == 0b110_000 {
+                    (Inc(Mem(AddrLoc::Reg(HL))), 3, 1)
+                } else {
+                    (Inc(Reg(Register::try_from((value & T1_MSK) >> 3)?)), 1, 1)
+                }
+            }
+            _ if (value & (HD_MSK | T2_MSK) == 0b00_000_101) => {
+                if (T1_MSK & value) == 0b110_000 {
+                    (Dec(Mem(AddrLoc::Reg(HL))), 3, 1)
+                } else {
+                    (Dec(Reg(Register::try_from((value & T1_MSK) >> 3)?)), 1, 1)
+                }
             }
             _ if (value & (HD_MSK | 0b1_000 | T2_MSK) == 0b11_000_101) => {
                 (Psh(Register::repr_psh(payload(value))), 4, 1)