From d785b1eae770e89692d8190d578b369edd0fe321 Mon Sep 17 00:00:00 2001
From: Adrian Conlon <adrian.conlon@gmail.com>
Date: Fri, 13 Nov 2020 17:28:35 +0000
Subject: [PATCH] Simplify LR35902 machine timing.

---
 LR35902/inc/LR35902.h   | 21 +++++++++++++--------
 LR35902/src/LR35902.cpp | 22 ++++++++++------------
 2 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/LR35902/inc/LR35902.h b/LR35902/inc/LR35902.h
index 93d8353..a8009a4 100644
--- a/LR35902/inc/LR35902.h
+++ b/LR35902/inc/LR35902.h
@@ -37,6 +37,11 @@ namespace EightBit {
 			[[nodiscard]] uint8_t flaggedInterrupts();
 			[[nodiscard]] uint8_t maskedInterrupts();
 
+			Signal<EventArgs> MachineTicked;
+
+			void tickMachine(const int extra) { for (int i = 0; i < extra; ++i) tickMachine(); }
+			void tickMachine() { tick(4); MachineTicked.fire(EventArgs::empty()); }
+
 		protected:
 			virtual int execute() final;
 			virtual int step() final;
@@ -45,46 +50,46 @@ namespace EightBit {
 			void handleINT() final;
 
 			void memoryWrite() final {
-				tick(4);
+				tickMachine();
 				IntelProcessor::memoryWrite();
 			}
 
 			uint8_t memoryRead() final {
-				tick(4);
+				tickMachine();
 				return IntelProcessor::memoryRead();
 			}
 
 			void pushWord(register16_t value) final {
-				tick(4);
+				tickMachine();
 				IntelProcessor::pushWord(value);
 			}
 
 			void jr(int8_t offset) final {
 				IntelProcessor::jr(offset);
-				tick(4);
+				tickMachine();
 			}
 
 			int jumpConditional(const int condition) final {
 				if (IntelProcessor::jumpConditional(condition))
-					tick(4);
+					tickMachine();
 				return condition;
 			}
 
 			int returnConditional(const int condition) final {
 				IntelProcessor::returnConditional(condition);
-				tick(4);
+				tickMachine();
 				return condition;
 			}
 
 			int jrConditional(const int condition) final {
 				if (!IntelProcessor::jrConditional(condition))
-					tick(4);
+					tickMachine();
 				return condition;
 			}
 
 			void ret() final {
 				IntelProcessor::ret();
-				tick(4);
+				tickMachine();
 			}
 
 		private:
diff --git a/LR35902/src/LR35902.cpp b/LR35902/src/LR35902.cpp
index 2b10635..b50f15d 100644
--- a/LR35902/src/LR35902.cpp
+++ b/LR35902/src/LR35902.cpp
@@ -7,11 +7,9 @@
 EightBit::GameBoy::LR35902::LR35902(Bus& memory)
 : IntelProcessor(memory),
   m_bus(memory) {
-	Ticked.connect([this](EventArgs) {
-		if ((cycles() % 4) == 0) {
-			m_bus.IO().incrementTimers();
-			m_bus.IO().transferDma();
-		}
+	MachineTicked.connect([this](EventArgs) {
+		m_bus.IO().incrementTimers();
+		m_bus.IO().transferDma();
 	});
 }
 
@@ -36,7 +34,7 @@ void EightBit::GameBoy::LR35902::handleRESET() {
 	IntelProcessor::handleRESET();
 	di();
 	SP() = Mask16 - 1;
-	tick(4 * 4);
+	tickMachine(4);
 }
 
 void EightBit::GameBoy::LR35902::handleINT() {
@@ -110,7 +108,7 @@ void EightBit::GameBoy::LR35902::reti() {
 
 EightBit::register16_t EightBit::GameBoy::LR35902::add(uint8_t& f, const register16_t operand, const register16_t value) {
 
-	tick(4);
+	tickMachine();
 
 	const int addition = operand.word + value.word;
 	const register16_t result = addition;
@@ -508,7 +506,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
 			default:
 				UNREACHABLE;
 			}
-			tick(4);
+			tickMachine();
 			break;
 		case 4: { // 8-bit INC
 			auto operand = R(y);
@@ -608,7 +606,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
 			case 5: { // GB: ADD SP,dd
 					const auto before = SP().word;
 					const int8_t value = fetchByte();
-					tick(2 * 4);
+					tickMachine(2);
 					const auto result = before + value;
 					SP() = result;
 					const auto carried = before ^ value ^ (result & Mask16);
@@ -623,7 +621,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
 			case 7: { // GB: LD HL,SP + dd
 					const auto before = SP().word;
 					const int8_t value = fetchByte();
-					tick(4);
+					tickMachine();
 					const auto result = before + value;
 					HL() = result;
 					const auto carried = before ^ value ^ (result & Mask16);
@@ -654,7 +652,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
 					break;
 				case 3:	// LD SP,HL
 					SP() = HL();
-					tick(4);
+					tickMachine();
 					break;
 				default:
 					UNREACHABLE;
@@ -694,7 +692,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
 			switch (y) {
 			case 0:	// JP nn
 				jump(MEMPTR() = fetchWord());
-				tick(4);
+				tickMachine();
 				break;
 			case 1:	// CB prefix
 				m_prefixCB = true;