From cf4565c36bb6cc81391be637f30e18fecbb00ae8 Mon Sep 17 00:00:00 2001
From: Lea <me@janderedev.xyz>
Date: Wed, 25 Jan 2023 16:24:39 +0100
Subject: [PATCH] Add ACI, DAD

---
 src/emulator/instructions/arithmetic.rs | 23 +++++++++++++++++++++++
 src/emulator/main.rs                    | 14 ++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/src/emulator/instructions/arithmetic.rs b/src/emulator/instructions/arithmetic.rs
index aa2df4e..2baf4dd 100644
--- a/src/emulator/instructions/arithmetic.rs
+++ b/src/emulator/instructions/arithmetic.rs
@@ -30,3 +30,26 @@ pub fn adc(register: Register, state: &mut EmulatorState) {
     set_cc(state, result, 0b1111);
     state.a = (result & 0xff) as u8;
 }
+
+/// Add values of input byte and `A` and add +1 if carry bit is set
+pub fn aci(byte: u8, state: &mut EmulatorState) {
+    let result = state.a as u16 + byte as u16 + if state.cc.c { 1 } else { 0 };
+    set_cc(state, result, 0b1111);
+    state.a = result as u8;
+}
+
+/// Double precision add - Add B&C, D&E or H&L to H&L
+pub fn dad(register: Register, state: &mut EmulatorState) {
+    let num = match register {
+        Register::B  => (state.b as u16) << 8 | state.c as u16,
+        Register::D  => (state.d as u16) << 8 | state.e as u16,
+        Register::H  => get_register(Register::M, state),
+        Register::SP => state.sp,
+        _ => panic!("Cannot perform DAD on register {:?}", register),
+    };
+
+    let result = num as u32 + get_register(Register::M, state) as u32;
+    state.cc.c = result > 0xffff;
+    state.h = (result >> 8) as u8;
+    state.l = result as u8;
+}
diff --git a/src/emulator/main.rs b/src/emulator/main.rs
index eed3021..e3b3e43 100644
--- a/src/emulator/main.rs
+++ b/src/emulator/main.rs
@@ -36,9 +36,11 @@ pub struct ConditionCodes {
 }
 
 #[derive(PartialEq)]
+#[derive(Debug)]
 pub enum Register {
     B, C, D, E,
     H, L, M, A,
+    SP,
 }
 
 /// Returns a Register enum based on the input number 0..7 in the order B,C,D,E,H,L,M,A
@@ -66,6 +68,7 @@ fn get_register(register: Register, state: &EmulatorState) -> u16 {
         Register::L => state.l as u16,
         Register::A => state.a as u16,
         Register::M => (state.memory[(state.h as usize)] as u16) << 8 | (state.memory[state.l as usize] as u16),
+        Register::SP => state.sp,
     }
 }
 
@@ -79,6 +82,7 @@ fn set_register(register: Register, value: u8, state: &mut EmulatorState) {
         Register::L => state.l = value,
         Register::A => state.a = value,
         Register::M => panic!("Cannot set pseudoregister 'M'"),
+        Register::SP => panic!("Cannot set 'SP' through set_register()"),
     };
 }
 
@@ -123,9 +127,19 @@ fn tick(state: &mut EmulatorState) {
 
     match instruction {
         0x00        => {} // NOP
+
+        /* ADD */
+
+        // DAD
+        0x09 => arithmetic::dad(Register::B, state),
+        0x19 => arithmetic::dad(Register::D, state),
+        0x29 => arithmetic::dad(Register::H, state),
+        0x39 => arithmetic::dad(Register::SP, state),
+
         0x80..=0x87 => arithmetic::add(register_from_num(instruction & 0xf), state), // ADD
         0x88..=0x8f => arithmetic::adc(register_from_num(instruction & 0xf), state), // ADC
         0xc6        => arithmetic::adi(next_byte(), state), // ADI
+        0xce        => arithmetic::aci(next_byte(), state), // ACI
         _           => not_implemented(state),
     }