From bf8bd66389251640d9ee441a44d7b0e5a3ed5bd0 Mon Sep 17 00:00:00 2001
From: Riyyi <riyyi3@gmail.com>
Date: Sun, 28 Aug 2022 22:09:15 +0200
Subject: [PATCH] Emulator: Implement 8-bit ADD opcodes

---
 src/cpu.cpp | 50 +++++++++++++++++++++++++++++++++++++++-----------
 src/cpu.h   |  2 +-
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/src/cpu.cpp b/src/cpu.cpp
index 8dc7164..561f726 100644
--- a/src/cpu.cpp
+++ b/src/cpu.cpp
@@ -192,6 +192,14 @@ void CPU::update()
 		case 0x7d: ldr8(); break;
 		case 0x7e: ldr8(); break;
 		case 0x7f: ldr8(); break;
+		case 0x80: add8(); break;
+		case 0x81: add8(); break;
+		case 0x82: add8(); break;
+		case 0x83: add8(); break;
+		case 0x84: add8(); break;
+		case 0x85: add8(); break;
+		case 0x86: add8(); break;
+		case 0x87: add8(); break;
 		case 0xa0: and8(); break;
 		case 0xa1: and8(); break;
 		case 0xa2: and8(); break;
@@ -214,7 +222,7 @@ void CPU::update()
 		case 0xc3: jp16(); break;
 		case 0xc4: call(); break;
 		case 0xc5: push(); break;
-		case 0xc6: addi8(); break;
+		case 0xc6: add8(); break;
 		case 0xc7: rst(); break;
 		case 0xcb: prefix(); break;
 		case 0xcc: call(); break;
@@ -269,25 +277,45 @@ void CPU::update()
 
 // -------------------------------------
 
-void CPU::addi8()
+void CPU::add8()
 {
-	uint8_t opcode = pcRead();
-	uint8_t immediate = pcRead();
-	switch (opcode) {
-	case 0xc6: // ADD A,i8, flags: Z 0 H C
-		m_wait_cycles += 8;
+	auto add = [this](uint8_t register_) -> void {
+		// ADD A,r8, flags: Z 0 H C
+		m_wait_cycles += 4;
 
 		// Set flags
 		m_nf = 0;
-		m_hf = isCarry(m_a, immediate, 0x10);
-		m_cf = isCarry(m_a, immediate, 0x100);
+		m_hf = isCarry(m_a, register_, 0x10);
+		m_cf = isCarry(m_a, register_, 0x100);
 
-		// A = A + r
-		m_a = (m_a + immediate) & 0xff;
+		// Add the value in r8 to A
+		m_a = (m_a + register_) & 0xff;
 
 		// Zero flag
 		m_zf = m_a == 0;
+	};
+
+	uint8_t opcode = pcRead();
+	switch (opcode) {
+	case 0x80: /* ADD A,B */ add(m_b); break;
+	case 0x81: /* ADD A,C */ add(m_c); break;
+	case 0x82: /* ADD A,D */ add(m_d); break;
+	case 0x83: /* ADD A,E */ add(m_e); break;
+	case 0x84: /* ADD A,H */ add(m_h); break;
+	case 0x85: /* ADD A,L */ add(m_l); break;
+	case 0x86: /* ADD A,(HL) */ {
+		m_wait_cycles += 4; // + 4 = 8 total
+
+		add(read(hl()));
 		break;
+	}
+	case 0x87: /* ADD A,A */ add(m_a); break;
+	case 0xc6: /* ADD A,i8 */ {
+		m_wait_cycles += 4; // + 4 = 8 total
+
+		add(pcRead());
+		break;
+	}
 	default:
 		VERIFY_NOT_REACHED();
 	}
diff --git a/src/cpu.h b/src/cpu.h
index 7d6fb3a..b505dae 100644
--- a/src/cpu.h
+++ b/src/cpu.h
@@ -28,7 +28,7 @@ public:
 	// Arithmetic and Logic Instructions
 
 	// 8-bit
-	void addi8();
+	void add8();
 	void and8();
 	void dec8();
 	void inc8();