Debugger: Added option to evaluate all breakpoints on the first cycle of an instruction

Core/CPU.cpp

@@ -10,6 +10,7 @@
 CPU::CPU(shared_ptr<Console> console)
 {
 	_console = console;
+	_memoryManager = _console->GetMemoryManager();
 
 	Func opTable[] = { 
 	//	0				1				2				3				4				5				6						7				8				9				A						B				C						D				E						F
@@ -64,7 +65,7 @@ CPU::CPU(shared_ptr<Console> console)
 	_dmcCounter = 0;
 	_dmcDmaRunning = false;
 	_cpuWrite = false;
-	_writeAddr = false;
+	_writeAddr = 0;
 	_irqMask = 0;
 	_state = {};
 	_prevRunIrq = false;
@@ -73,7 +74,6 @@ CPU::CPU(shared_ptr<Console> console)
 
 void CPU::Reset(bool softReset, NesModel model)
 {
-	_memoryManager = _console->GetMemoryManager();
 	_state.NMIFlag = false;
 	_state.IRQFlag = 0;
 	_cycleCount = -1;
@@ -140,15 +140,19 @@ void CPU::IRQ()
 		SetPC(MemoryReadWord(CPU::NMIVector));
 		_state.NMIFlag = false;
 
+		#ifndef DUMMYCPU
 		_console->DebugAddTrace("NMI");
 		_console->DebugProcessInterrupt(originalPc, _state.PC, true);
+		#endif
 	} else {
 		Push((uint8_t)(PS() | PSFlags::Reserved));
 		SetFlags(PSFlags::Interrupt);
 		SetPC(MemoryReadWord(CPU::IRQVector));
 
+		#ifndef DUMMYCPU
 		_console->DebugAddTrace("IRQ");
 		_console->DebugProcessInterrupt(originalPc, _state.PC, false);
+		#endif
 	}
 }
 
@@ -162,14 +166,18 @@ void CPU::BRK() {
 
 		SetPC(MemoryReadWord(CPU::NMIVector));
 
+		#ifndef DUMMYCPU
 		_console->DebugAddTrace("NMI");
+		#endif
 	} else {
 		Push((uint8_t)flags);
 		SetFlags(PSFlags::Interrupt);
 
 		SetPC(MemoryReadWord(CPU::IRQVector));
 
+		#ifndef DUMMYCPU
 		_console->DebugAddTrace("IRQ");
+		#endif
 	}
 
 	//Since we just set the flag to prevent interrupts, do not run one right away after this (fixes nmi_and_brk & nmi_and_irq tests)
@@ -184,7 +192,17 @@ void CPU::MemoryWrite(uint16_t addr, uint8_t value, MemoryOperationType operatio
 	while(_dmcDmaRunning) {
 		IncCycleCount();
 	}
+
+#ifdef DUMMYCPU
+	if(operationType == MemoryOperationType::Write || operationType == MemoryOperationType::DummyWrite) {
+		_writeAddresses[_writeCounter] = addr;
+		_isDummyWrite[_writeCounter] = operationType == MemoryOperationType::DummyWrite;
+		_writeValue[_writeCounter] = value;
+		_writeCounter++;
+	}
+#else
 	_memoryManager->Write(addr, value, operationType);
+#endif
 
 	//DMA DMC might have started after a write to $4015, stall CPU if needed
 	while(_dmcDmaRunning) {
@@ -202,16 +220,31 @@ uint8_t CPU::MemoryRead(uint16_t addr, MemoryOperationType operationType) {
 			//Reads are only performed every other cycle? This fixes "dma_2007_read" test
 			//This behavior causes the $4016/7 data corruption when a DMC is running.
 			//When reading $4016/7, only the last read counts (because this only occurs to low-to-high transitions, i.e once in this case)
+			#ifdef DUMMYCPU
+			_memoryManager->DebugRead(addr);
+			#else
 			_memoryManager->Read(addr);
+			#endif
 		}
 		IncCycleCount();
 	}
+
+#ifdef DUMMYCPU
+	if(operationType == MemoryOperationType::Read || operationType == MemoryOperationType::DummyRead) {
+		_readAddresses[_readCounter] = addr;
+		_isDummyRead[_readCounter] = operationType == MemoryOperationType::DummyRead;
+		_readCounter++;
+	}
+
+	return _memoryManager->DebugRead(addr);
+#else 
 	if(operationType == MemoryOperationType::ExecOpCode) {
 		_state.DebugPC = _state.PC;
 	}
 
 	uint8_t value = _memoryManager->Read(addr, operationType);
 	return value;
+#endif
 }
 
 uint16_t CPU::FetchOperand()
@@ -236,7 +269,7 @@ uint16_t CPU::FetchOperand()
 		default: break;
 	}
 	
-#ifndef LIBRETRO
+#if !defined(LIBRETRO) && !defined(DUMMYCPU)
 	if(_warnOnCrash && _console->GetSettings()->CheckFlag(EmulationFlags::DeveloperMode)) {
 		MessageManager::DisplayMessage("Error", "GameCrash", "Invalid OP code - CPU crashed.");
 		_warnOnCrash = false;
@@ -270,12 +303,16 @@ void CPU::IncCycleCount()
 		if(_dmcCounter == 0) {
 			//Update the DMC buffer when the stall period is completed
 			_dmcDmaRunning = false;
+			#ifndef DUMMYCPU
 			_console->GetApu()->FillDmcReadBuffer();
 			_console->DebugAddTrace("DMC DMA End");
+			#endif
 		}
 	}
 
+	#ifndef DUMMYCPU
 	_console->ProcessCpuClock();
+	#endif
 
 	if(!_spriteDmaTransfer && !_dmcDmaRunning) {
 		//IRQ flags are ignored during Sprite DMA - fixes irq_and_dma

Core/CPU.h

@@ -1,4 +1,9 @@
-#pragma once
+#if (defined(DUMMYCPU) && !defined(__DUMMYCPU__H)) || (!defined(DUMMYCPU) && !defined(__CPU__H))
+#ifdef DUMMYCPU
+#define __DUMMYCPU__H
+#else
+#define __CPU__H
+#endif
 
 #include "stdafx.h"
 #include "Snapshotable.h"
@@ -7,24 +12,12 @@
 enum class NesModel;
 class Console;
 class MemoryManager;
-
+class DummyCpu;
-namespace PSFlags
-{
-	enum PSFlags : uint8_t
-	{
-		Carry = 0x01,
-		Zero = 0x02,
-		Interrupt = 0x04,
-		Decimal = 0x08,
-		Break = 0x10,
-		Reserved = 0x20,
-		Overflow = 0x40,
-		Negative = 0x80
-	};
-}
 
 class CPU : public Snapshotable
 {
+	friend DummyCpu;
+
 public:
 	static constexpr uint16_t NMIVector = 0xFFFA;
 	static constexpr uint16_t ResetVector = 0xFFFC;
@@ -62,6 +55,17 @@ private:
 
 	bool _warnOnCrash = true;
 
+#ifdef DUMMYCPU
+	uint32_t _writeCounter = 0;
+	uint16_t _writeAddresses[10];
+	uint8_t _writeValue[10];
+	bool _isDummyWrite[10];
+
+	uint32_t _readCounter = 0;
+	uint16_t _readAddresses[10];
+	bool _isDummyRead[10];
+#endif
+
 	void IncCycleCount();
 	uint16_t FetchOperand();
 	void IRQ();
@@ -818,4 +822,53 @@ public:
 		state.PC = originalPc;
 		state.DebugPC = originalDebugPc;
 	}
+
+#ifdef DUMMYCPU
+#undef CPU
+	void SetDummyState(CPU *c)
+	{
+#define CPU DummyCpu
+		_writeCounter = 0;
+		_readCounter = 0;
+
+		_state = c->_state;
+
+		_cycleCount = c->_cycleCount;
+		_operand = c->_operand;
+		_spriteDmaCounter = c->_spriteDmaCounter;
+		_spriteDmaTransfer = c->_spriteDmaTransfer;
+		_dmcCounter = c->_dmcCounter;
+		_dmcDmaRunning = c->_dmcDmaRunning;
+		_cpuWrite = c->_cpuWrite;
+		_irqMask = c->_irqMask;
+		_prevRunIrq = c->_prevRunIrq;
+		_runIrq = c->_runIrq;
+		_cycleCount = c->_cycleCount;
+	}
+
+	uint32_t GetWriteCount()
+	{
+		return _writeCounter;
+	}
+
+	uint32_t GetReadCount()
+	{
+		return _readCounter;
+	}
+
+	void GetWriteAddrValue(uint32_t index, uint16_t &addr, uint8_t &value, bool &isDummyWrite)
+	{
+		addr = _writeAddresses[index];
+		value = _writeValue[index];
+		isDummyWrite = _isDummyWrite[index];
+	}
+
+	void GetReadAddr(uint32_t index, uint16_t &addr, bool &isDummyRead)
+	{
+		addr = _readAddresses[index];
+		isDummyRead = _isDummyRead[index];
+	}
+#endif
 };
+
+#endif

Core/Core.vcxproj

@@ -533,6 +533,7 @@
     <ClInclude Include="Dance2000.h" />
     <ClInclude Include="DragonFighter.h" />
     <ClInclude Include="DrawScreenBufferCommand.h" />
+    <ClInclude Include="DummyCpu.h" />
     <ClInclude Include="FaridSlrom.h" />
     <ClInclude Include="FaridUnrom.h" />
     <ClInclude Include="FdsSystemActionManager.h" />

Core/Core.vcxproj.filters

@@ -1471,6 +1471,9 @@
     <ClInclude Include="ConsolePauseHelper.h">
       <Filter>Misc</Filter>
     </ClInclude>
+    <ClInclude Include="DummyCpu.h">
+      <Filter>Debugger</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="stdafx.cpp">

Core/Debugger.cpp

@@ -29,6 +29,7 @@
 #include "CodeDataLogger.h"
 #include "NotificationManager.h"
 #include "DebugHud.h"
+#include "DummyCpu.h"
 
 const int Debugger::BreakpointTypeCount;
 string Debugger::_disassemblerOutput = "";
@@ -42,6 +43,9 @@ Debugger::Debugger(shared_ptr<Console> console, shared_ptr<CPU> cpu, shared_ptr<
 	_memoryManager = memoryManager;
 	_mapper = mapper;
 
+	_dummyCpu.reset(new DummyCpu(console));
+	_breakOnFirstCycle = false;
+
 	_labelManager.reset(new LabelManager(_mapper));
 	_assembler.reset(new Assembler(_labelManager));
 	_disassembler.reset(new Disassembler(memoryManager.get(), mapper.get(), this));
@@ -177,6 +181,7 @@ void Debugger::SetFlags(uint32_t flags)
 {
 	bool needUpdate = ((flags ^ _flags) & (int)DebuggerFlags::DisplayOpCodesInLowerCase) != 0;
 	_flags = flags;
+	_breakOnFirstCycle = CheckFlag(DebuggerFlags::BreakOnFirstCycle);
 	if(needUpdate) {
 		_disassembler->BuildOpCodeTables(CheckFlag(DebuggerFlags::DisplayOpCodesInLowerCase));
 	}
@@ -298,11 +303,11 @@ void Debugger::SetBreakpoints(Breakpoint breakpoints[], uint32_t length)
 	}
 }
 
-void Debugger::ProcessBreakpoints(BreakpointType type, OperationInfo &operationInfo, bool allowBreak)
+bool Debugger::ProcessBreakpoints(BreakpointType type, OperationInfo &operationInfo, bool allowBreak, bool allowMark)
 {
 	if(_runToCycle != 0) {
 		//Disable all breakpoints while stepping backwards
-		return;
+		return false;
 	}
 
 	AddressTypeInfo info { -1, AddressType::InternalRam };
@@ -347,6 +352,11 @@ void Debugger::ProcessBreakpoints(BreakpointType type, OperationInfo &operationI
 
 	for(size_t i = 0, len = breakpoints.size(); i < len; i++) {
 		Breakpoint &breakpoint = breakpoints[i];
+		if(!((breakpoint.IsEnabled() && allowBreak) || (breakpoint.IsMarked() && allowMark))) {
+			//Skip breakpoints we don't need to process
+			continue;
+		}
+
 		if(
 			type == BreakpointType::Global ||
 			(!isPpuBreakpoint && breakpoint.Matches(operationInfo.Address, info, operationInfo.OperationType)) ||
@@ -365,20 +375,117 @@ void Debugger::ProcessBreakpoints(BreakpointType type, OperationInfo &operationI
 			}
 		}
 
-		if(needMark && needBreak) {
+		if((needMark || !allowMark) && (needBreak || !allowBreak)) {
 			//No need to process remaining breakpoints
 			break;
 		}
 	}
 
-	if(needMark) {
+	if(needMark && allowMark) {
 		AddDebugEvent(DebugEventType::Breakpoint, operationInfo.Address, (uint8_t)operationInfo.Value, markBreakpointId);
 	}
 
 	if(needBreak && allowBreak) {
 		//Found a matching breakpoint, stop execution
 		Step(1);
-		SleepUntilResume(BreakSource::Breakpoint, breakpointId, type, operationInfo.Address);
+		SleepUntilResume(BreakSource::Breakpoint, breakpointId, type, operationInfo.Address, operationInfo.OperationType);
+		return true;
+	} else {
+		return false;
+	}
+}
+
+void Debugger::ProcessAllBreakpoints(OperationInfo &operationInfo, AddressTypeInfo &addressInfo)
+{
+	if(_hasBreakpoint[BreakpointType::Execute]) {
+		ProcessBreakpoints(BreakpointType::Execute, operationInfo, true, true);
+	}
+
+	_dummyCpu->SetDummyState(_cpu.get());
+	_dummyCpu->Exec();
+
+	DebugState &state = _debugState;
+	uint32_t readCount = _dummyCpu->GetReadCount();
+	if(readCount > 0) {
+		uint16_t addr;
+		bool isDummyRead;
+		for(uint32_t i = 0; i < readCount; i++) {
+			_dummyCpu->GetReadAddr(i, addr, isDummyRead);
+
+			OperationInfo info;
+
+			if(addr >= 0x2000 && addr < 0x4000 && (addr & 0x07) == 0x07) {
+				//Reads to $2007 will trigger a PPU read
+				if(_hasBreakpoint[BreakpointType::ReadVram]) {
+					OperationInfo ppuInfo;
+					ppuInfo.OperationType = MemoryOperationType::Read;
+					if((state.PPU.State.VideoRamAddr & 0x3FFF) >= 0x3F00) {
+						ppuInfo.Address = state.PPU.State.VideoRamAddr;
+						ppuInfo.Value = _ppu->ReadPaletteRAM(ppuInfo.Address);
+					} else {
+						ppuInfo.Address = state.PPU.BusAddress;
+						ppuInfo.Value = _mapper->DebugReadVRAM(ppuInfo.Address);
+					}
+					if(ProcessBreakpoints(BreakpointType::ReadVram, ppuInfo, true, false)) {
+						return;
+					}
+				}
+
+				info.Value = state.PPU.MemoryReadBuffer;
+			} else {
+				if(_enableBreakOnUninitRead && CheckFlag(DebuggerFlags::BreakOnUninitMemoryRead)) {
+					//Break on uninit memory read
+					if(_memoryAccessCounter->IsAddressUninitialized(addressInfo)) {
+						Step(1);
+						SleepUntilResume(BreakSource::BreakOnUninitMemoryRead, 0, BreakpointType::ReadRam, addr);
+						return;
+					}
+				}
+
+				info.Value = _memoryManager->DebugRead(addr);
+			}
+
+			if(_hasBreakpoint[BreakpointType::ReadRam]) {
+				info.Address = addr;
+				info.OperationType = isDummyRead ? MemoryOperationType::DummyRead : MemoryOperationType::Read;
+				if(ProcessBreakpoints(BreakpointType::ReadRam, info, true, false)) {
+					return;
+				}
+			}
+		}
+	}
+	
+	uint32_t writeCount = _dummyCpu->GetWriteCount();
+	if(writeCount > 0 && (_hasBreakpoint[BreakpointType::WriteRam] || _hasBreakpoint[BreakpointType::WriteVram])) {
+		uint16_t addr;
+		uint8_t value;
+		bool isDummyWrite;
+		for(uint32_t i = 0; i < writeCount; i++) {
+			_dummyCpu->GetWriteAddrValue(i, addr, value, isDummyWrite);
+
+			if(_hasBreakpoint[BreakpointType::WriteRam]) {
+				OperationInfo info;
+				info.Address = addr;
+				info.Value = value;
+				info.OperationType = isDummyWrite ? MemoryOperationType::DummyWrite : MemoryOperationType::Write;
+				if(ProcessBreakpoints(BreakpointType::WriteRam, info, true, false)) {
+					return;
+				}
+			}
+
+			if(_hasBreakpoint[BreakpointType::WriteVram]) {
+				if(addr >= 0x2000 && addr < 0x4000 && (addr & 0x07) == 0x07) {
+					//Write to $2007 will trigger a PPU write
+					OperationInfo ppuInfo;
+					ppuInfo.Address = state.PPU.BusAddress;
+					ppuInfo.Value = value;
+					ppuInfo.OperationType = MemoryOperationType::Write;
+					if(ProcessBreakpoints(BreakpointType::WriteVram, ppuInfo, true, false)) {
+						return;
+					}
+				}
+			}
+		}
 	}
 }
 
@@ -592,7 +699,7 @@ bool Debugger::ProcessRamOperation(MemoryOperationType type, uint16_t &addr, uin
 			}
 		} else {
 			if(_memoryAccessCounter->ProcessMemoryAccess(addressInfo, type, _cpu->GetCycleCount())) {
-				if(_enableBreakOnUninitRead && CheckFlag(DebuggerFlags::BreakOnUninitMemoryRead)) {
+				if(!_breakOnFirstCycle && _enableBreakOnUninitRead && CheckFlag(DebuggerFlags::BreakOnUninitMemoryRead)) {
 					//Break on uninit memory read
 					Step(1);
 					breakDone = SleepUntilResume(BreakSource::BreakOnUninitMemoryRead);
@@ -691,8 +798,17 @@ bool Debugger::ProcessRamOperation(MemoryOperationType type, uint16_t &addr, uin
 		case MemoryOperationType::Write: breakpointType = BreakpointType::WriteRam; break;
 	}
 
-	if(_hasBreakpoint[breakpointType]) {
+	if(_breakOnFirstCycle) {
-		ProcessBreakpoints(breakpointType, operationInfo, !breakDone);
+		if(type == MemoryOperationType::ExecOpCode && !breakDone) {
+			ProcessAllBreakpoints(operationInfo, addressInfo);
+		}
+
+		//Process marked breakpoints
+		ProcessBreakpoints(breakpointType, operationInfo, false, true);
+	} else {
+		if(_hasBreakpoint[breakpointType]) {
+			ProcessBreakpoints(breakpointType, operationInfo, !breakDone, true);
+		}
 	}
 
 	_currentReadAddr = nullptr;
@@ -726,7 +842,7 @@ bool Debugger::ProcessRamOperation(MemoryOperationType type, uint16_t &addr, uin
 	return true;
 }
 
-bool Debugger::SleepUntilResume(BreakSource source, uint32_t breakpointId, BreakpointType bpType, uint16_t bpAddress)
+bool Debugger::SleepUntilResume(BreakSource source, uint32_t breakpointId, BreakpointType bpType, uint16_t bpAddress, MemoryOperationType bpMemOpType)
 {
 	int32_t stepCount = _stepCount.load();
 	if(stepCount > 0) {
@@ -753,7 +869,14 @@ bool Debugger::SleepUntilResume(BreakSource source, uint32_t breakpointId, Break
 			}
 			_breakSource = BreakSource::Unspecified;
 
-			uint64_t param = ((uint64_t)breakpointId << 32) | ((uint64_t)(bpAddress & 0xFFFF) << 16) | ((uint64_t)(bpType & 0xFF) << 8) | ((uint64_t)source & 0xFF);
+			uint64_t param = (
+				((uint64_t)breakpointId << 32) | 
+				((uint64_t)(bpAddress & 0xFFFF) << 16) | 
+				((uint64_t)((int)bpMemOpType & 0x0F) << 12) |
+				((uint64_t)(bpType & 0x0F) << 8) |
+				((uint64_t)source & 0xFF)
+			);
+
 			_console->GetNotificationManager()->SendNotification(ConsoleNotificationType::CodeBreak, (void*)(uint64_t)param);
 
 			ProcessEvent(EventType::CodeBreak);
@@ -784,7 +907,7 @@ void Debugger::ProcessVramReadOperation(MemoryOperationType type, uint16_t addr,
 	int32_t absoluteAddr = _mapper->ToAbsoluteChrAddress(addr);
 	_codeDataLogger->SetFlag(absoluteAddr, type == MemoryOperationType::Read ? CdlChrFlags::Read : CdlChrFlags::Drawn);
 
-	if(_hasBreakpoint[BreakpointType::ReadVram]) {
+	if(!_breakOnFirstCycle && _hasBreakpoint[BreakpointType::ReadVram]) {
 		OperationInfo operationInfo{ addr, value, type };
 		ProcessBreakpoints(BreakpointType::ReadVram, operationInfo);
 	}
@@ -794,7 +917,7 @@ void Debugger::ProcessVramReadOperation(MemoryOperationType type, uint16_t addr,
 
 void Debugger::ProcessVramWriteOperation(uint16_t addr, uint8_t &value)
 {
-	if(_hasBreakpoint[BreakpointType::WriteVram]) {
+	if(!_breakOnFirstCycle && _hasBreakpoint[BreakpointType::WriteVram]) {
 		OperationInfo operationInfo{ addr, value, MemoryOperationType::Write };
 		ProcessBreakpoints(BreakpointType::WriteVram, operationInfo);
 	}

Core/Debugger.h

@@ -29,6 +29,7 @@ class TraceLogger;
 class Breakpoint;
 class CodeDataLogger;
 class ExpressionEvaluator;
+class DummyCpu;
 struct ExpressionData;
 
 enum EvalResultType : int32_t;
@@ -59,6 +60,9 @@ private:
 	shared_ptr<MemoryManager> _memoryManager;
 	shared_ptr<BaseMapper> _mapper;
 	
+	shared_ptr<DummyCpu> _dummyCpu;
+	bool _breakOnFirstCycle;
+
 	bool _hasScript;
 	SimpleLock _scriptLock;
 	int _nextScriptId;
@@ -138,13 +142,14 @@ private:
 	vector<vector<int>> _debugEventMarkerRpn;
 
 private:
-	void ProcessBreakpoints(BreakpointType type, OperationInfo &operationInfo, bool allowBreak = true);
+	bool ProcessBreakpoints(BreakpointType type, OperationInfo &operationInfo, bool allowBreak = true, bool allowMark = true);
+	void ProcessAllBreakpoints(OperationInfo &operationInfo, AddressTypeInfo &addressInfo);
 	
 	void AddCallstackFrame(uint16_t source, uint16_t target, StackFrameFlags flags);
 	void UpdateCallstack(uint8_t currentInstruction, uint32_t addr);
 
 	void ProcessStepConditions(uint16_t addr);
-	bool SleepUntilResume(BreakSource source, uint32_t breakpointId = 0, BreakpointType bpType = BreakpointType::Global, uint16_t bpAddress = 0);
+	bool SleepUntilResume(BreakSource source, uint32_t breakpointId = 0, BreakpointType bpType = BreakpointType::Global, uint16_t bpAddress = 0, MemoryOperationType bpMemOpType = MemoryOperationType::Read);
 
 	void AddDebugEvent(DebugEventType type, uint16_t address = -1, uint8_t value = 0, int16_t breakpointId = -1, int8_t ppuLatch = -1);
 

Core/DebuggerTypes.h

@@ -36,6 +36,8 @@ enum class DebuggerFlags
 	BreakOnDecayedOamRead = 0x2000,
 	BreakOnInit = 0x4000,
 	BreakOnPlay = 0x8000,
+
+	BreakOnFirstCycle = 0x10000,
 };
 
 enum class BreakSource
@@ -117,6 +119,8 @@ struct PPUDebugState
 	uint32_t NmiScanline;
 	uint32_t ScanlineCount;
 	uint32_t SafeOamScanline;
+	uint16_t BusAddress;
+	uint8_t MemoryReadBuffer;
 };
 
 struct DebugState

Core/DummyCpu.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "stdafx.h"
+
+#define DUMMYCPU
+#define CPU DummyCpu
+#include "CPU.h"
+#include "CPU.cpp"
+#undef CPU
+#undef DUMMYCPU

Core/MemoryAccessCounter.cpp

@@ -42,6 +42,15 @@ vector<int32_t>& MemoryAccessCounter::GetArray(MemoryOperationType operationType
 	}
 }
 
+bool MemoryAccessCounter::IsAddressUninitialized(AddressTypeInfo &addressInfo)
+{
+	if(addressInfo.Type == AddressType::InternalRam || addressInfo.Type == AddressType::WorkRam) {
+		int index = (int)addressInfo.Type;
+		return !_initWrites[index][addressInfo.Address];
+	}
+	return false;
+}
+
 bool MemoryAccessCounter::ProcessMemoryAccess(AddressTypeInfo &addressInfo, MemoryOperationType operation, int32_t cpuCycle)
 {
 	int index = (int)addressInfo.Type;

Core/MemoryAccessCounter.h

@@ -28,6 +28,8 @@ public:
 	bool ProcessMemoryAccess(AddressTypeInfo &addressInfo, MemoryOperationType operation, int32_t cpuCycle);
 	void ResetCounts();
 
+	bool IsAddressUninitialized(AddressTypeInfo &addressInfo);
+	
 	void GetAccessCounts(AddressType memoryType, MemoryOperationType operationType, uint32_t counts[], bool forUninitReads);
 	void GetAccessCountsEx(uint32_t offset, uint32_t length, DebugMemoryType memoryType, MemoryOperationType operationType, int32_t counts[]);
 	void GetAccessStamps(uint32_t offset, uint32_t length, DebugMemoryType memoryType, MemoryOperationType operationType, uint32_t stamps[]);

Core/PPU.cpp

@@ -150,6 +150,8 @@ void PPU::GetState(PPUDebugState &state)
 	state.NmiScanline = _nmiScanline;
 	state.ScanlineCount = _vblankEnd + 2;
 	state.SafeOamScanline = _nesModel == NesModel::NTSC ? _nmiScanline + 19 : _palSpriteEvalScanline;
+	state.BusAddress = _ppuBusAddress;
+	state.MemoryReadBuffer = _memoryReadBuffer;
 }
 
 void PPU::SetState(PPUDebugState &state)

Core/Types.h

@@ -1,6 +1,21 @@
 #pragma once
 #include "stdafx.h"
 
+namespace PSFlags
+{
+	enum PSFlags : uint8_t
+	{
+		Carry = 0x01,
+		Zero = 0x02,
+		Interrupt = 0x04,
+		Decimal = 0x08,
+		Break = 0x10,
+		Reserved = 0x20,
+		Overflow = 0x40,
+		Negative = 0x80
+	};
+}
+
 enum class AddrMode
 {
 	None, Acc, Imp, Imm, Rel,

GUI.NET/Config/DebugInfo.cs

@@ -301,6 +301,7 @@ namespace Mesen.GUI.Config
 		public bool BreakOnUninitMemoryRead = false;
 		public bool BreakOnInit = true;
 		public bool BreakOnPlay = false;
+		public bool BreakOnFirstCycle = true;
 
 		public bool BringToFrontOnPause = false;
 		public bool BringToFrontOnBreak = true;

GUI.NET/Debugger/frmDebugger.Designer.cs

@@ -140,6 +140,7 @@ namespace Mesen.GUI.Debugger
 			this.toolStripMenuItem20 = new System.Windows.Forms.ToolStripSeparator();
 			this.mnuBringToFrontOnBreak = new System.Windows.Forms.ToolStripMenuItem();
 			this.mnuBringToFrontOnPause = new System.Windows.Forms.ToolStripMenuItem();
+			this.mnuEnableSubInstructionBreakpoints = new System.Windows.Forms.ToolStripMenuItem();
 			this.toolStripMenuItem12 = new System.Windows.Forms.ToolStripSeparator();
 			this.mnuShowOptions = new System.Windows.Forms.ToolStripMenuItem();
 			this.mnuShowToolbar = new System.Windows.Forms.ToolStripMenuItem();
@@ -174,6 +175,8 @@ namespace Mesen.GUI.Debugger
 			this.mnuPpuShowPreviousFrame = new System.Windows.Forms.ToolStripMenuItem();
 			this.toolStripMenuItem19 = new System.Windows.Forms.ToolStripSeparator();
 			this.mnuShowBreakNotifications = new System.Windows.Forms.ToolStripMenuItem();
+			this.mnuShowInstructionProgression = new System.Windows.Forms.ToolStripMenuItem();
+			this.toolStripMenuItem27 = new System.Windows.Forms.ToolStripSeparator();
 			this.mnuAlwaysScrollToCenter = new System.Windows.Forms.ToolStripMenuItem();
 			this.mnuRefreshWhileRunning = new System.Windows.Forms.ToolStripMenuItem();
 			this.toolStripMenuItem6 = new System.Windows.Forms.ToolStripSeparator();
@@ -211,8 +214,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlPpuMemoryMapping = new Mesen.GUI.Debugger.Controls.ctrlMemoryMapping();
 			this.ctrlCpuMemoryMapping = new Mesen.GUI.Debugger.Controls.ctrlMemoryMapping();
 			this.tsToolbar = new Mesen.GUI.Controls.ctrlMesenToolStrip();
-			this.mnuShowInstructionProgression = new System.Windows.Forms.ToolStripMenuItem();
+			this.toolStripMenuItem28 = new System.Windows.Forms.ToolStripSeparator();
-			this.toolStripMenuItem27 = new System.Windows.Forms.ToolStripSeparator();
 			((System.ComponentModel.ISupportInitialize)(this.splitContainer)).BeginInit();
 			this.splitContainer.Panel1.SuspendLayout();
 			this.splitContainer.Panel2.SuspendLayout();
@@ -257,7 +259,7 @@ namespace Mesen.GUI.Debugger
 			this.splitContainer.Panel2.Controls.Add(this.tableLayoutPanel10);
 			this.splitContainer.Panel2MinSize = 100;
 			this.splitContainer.Size = new System.Drawing.Size(1075, 570);
-			this.splitContainer.SplitterDistance = 416;
+			this.splitContainer.SplitterDistance = 410;
 			this.splitContainer.SplitterWidth = 7;
 			this.splitContainer.TabIndex = 1;
 			this.splitContainer.TabStop = false;
@@ -281,7 +283,7 @@ namespace Mesen.GUI.Debugger
 			// 
 			this.ctrlSplitContainerTop.Panel2.Controls.Add(this.tlpFunctionLabelLists);
 			this.ctrlSplitContainerTop.Panel2MinSize = 150;
-			this.ctrlSplitContainerTop.Size = new System.Drawing.Size(1075, 416);
+			this.ctrlSplitContainerTop.Size = new System.Drawing.Size(1075, 410);
 			this.ctrlSplitContainerTop.SplitterDistance = 750;
 			this.ctrlSplitContainerTop.SplitterWidth = 7;
 			this.ctrlSplitContainerTop.TabIndex = 3;
@@ -302,8 +304,8 @@ namespace Mesen.GUI.Debugger
 			this.tlpTop.Name = "tlpTop";
 			this.tlpTop.RowCount = 1;
 			this.tlpTop.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 100F));
-			this.tlpTop.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Absolute, 416F));
+			this.tlpTop.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Absolute, 410F));
-			this.tlpTop.Size = new System.Drawing.Size(750, 416);
+			this.tlpTop.Size = new System.Drawing.Size(750, 410);
 			this.tlpTop.TabIndex = 2;
 			// 
 			// panel1
@@ -314,7 +316,7 @@ namespace Mesen.GUI.Debugger
 			this.panel1.Location = new System.Drawing.Point(3, 0);
 			this.panel1.Margin = new System.Windows.Forms.Padding(3, 0, 3, 0);
 			this.panel1.Name = "panel1";
-			this.panel1.Size = new System.Drawing.Size(286, 416);
+			this.panel1.Size = new System.Drawing.Size(286, 410);
 			this.panel1.TabIndex = 5;
 			// 
 			// ctrlSourceViewer
@@ -323,7 +325,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlSourceViewer.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlSourceViewer.Location = new System.Drawing.Point(0, 0);
 			this.ctrlSourceViewer.Name = "ctrlSourceViewer";
-			this.ctrlSourceViewer.Size = new System.Drawing.Size(286, 416);
+			this.ctrlSourceViewer.Size = new System.Drawing.Size(286, 410);
 			this.ctrlSourceViewer.SymbolProvider = null;
 			this.ctrlSourceViewer.TabIndex = 7;
 			this.ctrlSourceViewer.Visible = false;
@@ -336,7 +338,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlDebuggerCode.Location = new System.Drawing.Point(0, 0);
 			this.ctrlDebuggerCode.Name = "ctrlDebuggerCode";
 			this.ctrlDebuggerCode.ShowMemoryValues = false;
-			this.ctrlDebuggerCode.Size = new System.Drawing.Size(286, 416);
+			this.ctrlDebuggerCode.Size = new System.Drawing.Size(286, 410);
 			this.ctrlDebuggerCode.SymbolProvider = null;
 			this.ctrlDebuggerCode.TabIndex = 2;
 			this.ctrlDebuggerCode.OnEditCode += new Mesen.GUI.Debugger.ctrlDebuggerCode.AssemblerEventHandler(this.ctrlDebuggerCode_OnEditCode);
@@ -350,7 +352,7 @@ namespace Mesen.GUI.Debugger
 			this.panel2.Location = new System.Drawing.Point(292, 0);
 			this.panel2.Margin = new System.Windows.Forms.Padding(0, 0, 3, 0);
 			this.panel2.Name = "panel2";
-			this.panel2.Size = new System.Drawing.Size(1, 416);
+			this.panel2.Size = new System.Drawing.Size(1, 410);
 			this.panel2.TabIndex = 6;
 			// 
 			// ctrlSourceViewerSplit
@@ -359,7 +361,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlSourceViewerSplit.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlSourceViewerSplit.Location = new System.Drawing.Point(0, 0);
 			this.ctrlSourceViewerSplit.Name = "ctrlSourceViewerSplit";
-			this.ctrlSourceViewerSplit.Size = new System.Drawing.Size(1, 416);
+			this.ctrlSourceViewerSplit.Size = new System.Drawing.Size(1, 410);
 			this.ctrlSourceViewerSplit.SymbolProvider = null;
 			this.ctrlSourceViewerSplit.TabIndex = 8;
 			this.ctrlSourceViewerSplit.Visible = false;
@@ -372,7 +374,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlDebuggerCodeSplit.Location = new System.Drawing.Point(0, 0);
 			this.ctrlDebuggerCodeSplit.Name = "ctrlDebuggerCodeSplit";
 			this.ctrlDebuggerCodeSplit.ShowMemoryValues = false;
-			this.ctrlDebuggerCodeSplit.Size = new System.Drawing.Size(1, 416);
+			this.ctrlDebuggerCodeSplit.Size = new System.Drawing.Size(1, 410);
 			this.ctrlDebuggerCodeSplit.SymbolProvider = null;
 			this.ctrlDebuggerCodeSplit.TabIndex = 4;
 			this.ctrlDebuggerCodeSplit.Visible = false;
@@ -392,7 +394,7 @@ namespace Mesen.GUI.Debugger
 			this.tableLayoutPanel1.RowCount = 2;
 			this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle());
 			this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 100F));
-			this.tableLayoutPanel1.Size = new System.Drawing.Size(458, 416);
+			this.tableLayoutPanel1.Size = new System.Drawing.Size(458, 410);
 			this.tableLayoutPanel1.TabIndex = 7;
 			// 
 			// ctrlConsoleStatus
@@ -416,7 +418,7 @@ namespace Mesen.GUI.Debugger
 			this.tlpVerticalLayout.Name = "tlpVerticalLayout";
 			this.tlpVerticalLayout.RowCount = 1;
 			this.tlpVerticalLayout.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 50F));
-			this.tlpVerticalLayout.Size = new System.Drawing.Size(458, 16);
+			this.tlpVerticalLayout.Size = new System.Drawing.Size(458, 10);
 			this.tlpVerticalLayout.TabIndex = 4;
 			// 
 			// tlpFunctionLabelLists
@@ -432,16 +434,16 @@ namespace Mesen.GUI.Debugger
 			this.tlpFunctionLabelLists.RowCount = 2;
 			this.tlpFunctionLabelLists.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 50F));
 			this.tlpFunctionLabelLists.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 50F));
-			this.tlpFunctionLabelLists.Size = new System.Drawing.Size(318, 416);
+			this.tlpFunctionLabelLists.Size = new System.Drawing.Size(318, 410);
 			this.tlpFunctionLabelLists.TabIndex = 5;
 			// 
 			// grpLabels
 			// 
 			this.grpLabels.Controls.Add(this.ctrlLabelList);
 			this.grpLabels.Dock = System.Windows.Forms.DockStyle.Fill;
-			this.grpLabels.Location = new System.Drawing.Point(3, 211);
+			this.grpLabels.Location = new System.Drawing.Point(3, 208);
 			this.grpLabels.Name = "grpLabels";
-			this.grpLabels.Size = new System.Drawing.Size(312, 202);
+			this.grpLabels.Size = new System.Drawing.Size(312, 199);
 			this.grpLabels.TabIndex = 6;
 			this.grpLabels.TabStop = false;
 			this.grpLabels.Text = "Labels";
@@ -451,7 +453,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlLabelList.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlLabelList.Location = new System.Drawing.Point(3, 16);
 			this.ctrlLabelList.Name = "ctrlLabelList";
-			this.ctrlLabelList.Size = new System.Drawing.Size(306, 183);
+			this.ctrlLabelList.Size = new System.Drawing.Size(306, 180);
 			this.ctrlLabelList.TabIndex = 0;
 			this.ctrlLabelList.OnFindOccurrence += new System.EventHandler(this.ctrlLabelList_OnFindOccurrence);
 			this.ctrlLabelList.OnLabelSelected += new System.EventHandler(this.ctrlLabelList_OnLabelSelected);
@@ -462,7 +464,7 @@ namespace Mesen.GUI.Debugger
 			this.grpFunctions.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.grpFunctions.Location = new System.Drawing.Point(3, 3);
 			this.grpFunctions.Name = "grpFunctions";
-			this.grpFunctions.Size = new System.Drawing.Size(312, 202);
+			this.grpFunctions.Size = new System.Drawing.Size(312, 199);
 			this.grpFunctions.TabIndex = 5;
 			this.grpFunctions.TabStop = false;
 			this.grpFunctions.Text = "Functions";
@@ -472,7 +474,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlFunctionList.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlFunctionList.Location = new System.Drawing.Point(3, 16);
 			this.ctrlFunctionList.Name = "ctrlFunctionList";
-			this.ctrlFunctionList.Size = new System.Drawing.Size(306, 183);
+			this.ctrlFunctionList.Size = new System.Drawing.Size(306, 180);
 			this.ctrlFunctionList.TabIndex = 0;
 			this.ctrlFunctionList.OnFindOccurrence += new System.EventHandler(this.ctrlFunctionList_OnFindOccurrence);
 			this.ctrlFunctionList.OnFunctionSelected += new System.EventHandler(this.ctrlFunctionList_OnFunctionSelected);
@@ -503,7 +505,7 @@ namespace Mesen.GUI.Debugger
 			this.tableLayoutPanel10.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 100F));
 			this.tableLayoutPanel10.RowStyles.Add(new System.Windows.Forms.RowStyle());
 			this.tableLayoutPanel10.RowStyles.Add(new System.Windows.Forms.RowStyle());
-			this.tableLayoutPanel10.Size = new System.Drawing.Size(1075, 147);
+			this.tableLayoutPanel10.Size = new System.Drawing.Size(1075, 153);
 			this.tableLayoutPanel10.TabIndex = 0;
 			// 
 			// grpWatch
@@ -512,7 +514,7 @@ namespace Mesen.GUI.Debugger
 			this.grpWatch.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.grpWatch.Location = new System.Drawing.Point(3, 3);
 			this.grpWatch.Name = "grpWatch";
-			this.grpWatch.Size = new System.Drawing.Size(352, 141);
+			this.grpWatch.Size = new System.Drawing.Size(352, 147);
 			this.grpWatch.TabIndex = 2;
 			this.grpWatch.TabStop = false;
 			this.grpWatch.Text = "Watch";
@@ -522,7 +524,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlWatch.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlWatch.Location = new System.Drawing.Point(3, 16);
 			this.ctrlWatch.Name = "ctrlWatch";
-			this.ctrlWatch.Size = new System.Drawing.Size(346, 122);
+			this.ctrlWatch.Size = new System.Drawing.Size(346, 128);
 			this.ctrlWatch.TabIndex = 0;
 			// 
 			// grpBreakpoints
@@ -531,7 +533,7 @@ namespace Mesen.GUI.Debugger
 			this.grpBreakpoints.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.grpBreakpoints.Location = new System.Drawing.Point(361, 3);
 			this.grpBreakpoints.Name = "grpBreakpoints";
-			this.grpBreakpoints.Size = new System.Drawing.Size(352, 141);
+			this.grpBreakpoints.Size = new System.Drawing.Size(352, 147);
 			this.grpBreakpoints.TabIndex = 3;
 			this.grpBreakpoints.TabStop = false;
 			this.grpBreakpoints.Text = "Breakpoints";
@@ -541,7 +543,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlBreakpoints.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlBreakpoints.Location = new System.Drawing.Point(3, 16);
 			this.ctrlBreakpoints.Name = "ctrlBreakpoints";
-			this.ctrlBreakpoints.Size = new System.Drawing.Size(346, 122);
+			this.ctrlBreakpoints.Size = new System.Drawing.Size(346, 128);
 			this.ctrlBreakpoints.TabIndex = 0;
 			this.ctrlBreakpoints.BreakpointNavigation += new System.EventHandler(this.ctrlBreakpoints_BreakpointNavigation);
 			// 
@@ -551,7 +553,7 @@ namespace Mesen.GUI.Debugger
 			this.grpCallstack.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.grpCallstack.Location = new System.Drawing.Point(719, 3);
 			this.grpCallstack.Name = "grpCallstack";
-			this.grpCallstack.Size = new System.Drawing.Size(353, 141);
+			this.grpCallstack.Size = new System.Drawing.Size(353, 147);
 			this.grpCallstack.TabIndex = 4;
 			this.grpCallstack.TabStop = false;
 			this.grpCallstack.Text = "Call Stack";
@@ -561,7 +563,7 @@ namespace Mesen.GUI.Debugger
 			this.ctrlCallstack.Dock = System.Windows.Forms.DockStyle.Fill;
 			this.ctrlCallstack.Location = new System.Drawing.Point(3, 16);
 			this.ctrlCallstack.Name = "ctrlCallstack";
-			this.ctrlCallstack.Size = new System.Drawing.Size(347, 122);
+			this.ctrlCallstack.Size = new System.Drawing.Size(347, 128);
 			this.ctrlCallstack.TabIndex = 0;
 			this.ctrlCallstack.FunctionSelected += new System.EventHandler(this.ctrlCallstack_FunctionSelected);
 			// 
@@ -1181,7 +1183,9 @@ namespace Mesen.GUI.Debugger
             this.mnuBreakOnDebuggerFocus,
             this.toolStripMenuItem20,
             this.mnuBringToFrontOnBreak,
-            this.mnuBringToFrontOnPause});
+            this.mnuBringToFrontOnPause,
+            this.toolStripMenuItem28,
+            this.mnuEnableSubInstructionBreakpoints});
 			this.mnuBreakOptions.Name = "mnuBreakOptions";
 			this.mnuBreakOptions.Size = new System.Drawing.Size(266, 22);
 			this.mnuBreakOptions.Text = "Break Options";
@@ -1303,6 +1307,14 @@ namespace Mesen.GUI.Debugger
 			this.mnuBringToFrontOnPause.Text = "Bring debugger to front on pause";
 			this.mnuBringToFrontOnPause.Click += new System.EventHandler(this.mnuBringToFrontOnPause_Click);
 			// 
+			// mnuBreakOnFirstCycle
+			// 
+			this.mnuEnableSubInstructionBreakpoints.CheckOnClick = true;
+			this.mnuEnableSubInstructionBreakpoints.Name = "mnuEnableSubInstructionBreakpoints";
+			this.mnuEnableSubInstructionBreakpoints.Size = new System.Drawing.Size(261, 22);
+			this.mnuEnableSubInstructionBreakpoints.Text = "Enable sub-instruction breakpoints";
+			this.mnuEnableSubInstructionBreakpoints.Click += new System.EventHandler(this.mnuBreakOnFirstCycle_Click);
+			// 
 			// toolStripMenuItem12
 			// 
 			this.toolStripMenuItem12.Name = "toolStripMenuItem12";
@@ -1572,6 +1584,19 @@ namespace Mesen.GUI.Debugger
 			this.mnuShowBreakNotifications.Text = "Show break notifications";
 			this.mnuShowBreakNotifications.Click += new System.EventHandler(this.mnuShowBreakNotifications_Click);
 			// 
+			// mnuShowInstructionProgression
+			// 
+			this.mnuShowInstructionProgression.CheckOnClick = true;
+			this.mnuShowInstructionProgression.Name = "mnuShowInstructionProgression";
+			this.mnuShowInstructionProgression.Size = new System.Drawing.Size(266, 22);
+			this.mnuShowInstructionProgression.Text = "Show instruction progression";
+			this.mnuShowInstructionProgression.Click += new System.EventHandler(this.mnuShowInstructionProgression_Click);
+			// 
+			// toolStripMenuItem27
+			// 
+			this.toolStripMenuItem27.Name = "toolStripMenuItem27";
+			this.toolStripMenuItem27.Size = new System.Drawing.Size(263, 6);
+			// 
 			// mnuAlwaysScrollToCenter
 			// 
 			this.mnuAlwaysScrollToCenter.CheckOnClick = true;
@@ -1874,18 +1899,10 @@ namespace Mesen.GUI.Debugger
 			this.tsToolbar.Text = "toolStrip1";
 			this.tsToolbar.Visible = false;
 			// 
-			// mnuShowInstructionProgression
+			// toolStripMenuItem28
 			// 
-			this.mnuShowInstructionProgression.CheckOnClick = true;
+			this.toolStripMenuItem28.Name = "toolStripMenuItem28";
-			this.mnuShowInstructionProgression.Name = "mnuShowInstructionProgression";
+			this.toolStripMenuItem28.Size = new System.Drawing.Size(258, 6);
-			this.mnuShowInstructionProgression.Size = new System.Drawing.Size(266, 22);
-			this.mnuShowInstructionProgression.Text = "Show instruction progression";
-			this.mnuShowInstructionProgression.Click += new System.EventHandler(this.mnuShowInstructionProgression_Click);
-			// 
-			// toolStripMenuItem27
-			// 
-			this.toolStripMenuItem27.Name = "toolStripMenuItem27";
-			this.toolStripMenuItem27.Size = new System.Drawing.Size(263, 6);
 			// 
 			// frmDebugger
 			// 
@@ -2120,5 +2137,7 @@ namespace Mesen.GUI.Debugger
 		private System.Windows.Forms.ToolStripMenuItem mnuShowBreakNotifications;
 		private System.Windows.Forms.ToolStripMenuItem mnuShowInstructionProgression;
 		private System.Windows.Forms.ToolStripSeparator toolStripMenuItem27;
+		private System.Windows.Forms.ToolStripMenuItem mnuEnableSubInstructionBreakpoints;
+		private System.Windows.Forms.ToolStripSeparator toolStripMenuItem28;
 	}
 }

GUI.NET/Debugger/frmDebugger.cs

@@ -102,6 +102,7 @@ namespace Mesen.GUI.Debugger
 			this.mnuShowPpuMemoryMapping.Checked = ConfigManager.Config.DebugInfo.ShowPpuMemoryMapping;
 			this.mnuAutoLoadDbgFiles.Checked = ConfigManager.Config.DebugInfo.AutoLoadDbgFiles;
 			this.mnuAutoLoadCdlFiles.Checked = ConfigManager.Config.DebugInfo.AutoLoadCdlFiles;
+			this.mnuEnableSubInstructionBreakpoints.Checked = !ConfigManager.Config.DebugInfo.BreakOnFirstCycle;
 			this.mnuBreakOnReset.Checked = ConfigManager.Config.DebugInfo.BreakOnReset;
 			this.mnuBreakOnInit.Checked = ConfigManager.Config.DebugInfo.BreakOnInit;
 			this.mnuBreakOnPlay.Checked = ConfigManager.Config.DebugInfo.BreakOnPlay;
@@ -484,6 +485,7 @@ namespace Mesen.GUI.Debugger
 			SetFlag(DebuggerFlags.BreakOnDecayedOamRead, config.BreakOnDecayedOamRead);
 			SetFlag(DebuggerFlags.BreakOnInit, config.BreakOnInit);
 			SetFlag(DebuggerFlags.BreakOnPlay, config.BreakOnPlay);
+			SetFlag(DebuggerFlags.BreakOnFirstCycle, config.BreakOnFirstCycle);
 			SetFlag(DebuggerFlags.HidePauseIcon, config.HidePauseIcon);
 			InteropEmu.SetFlag(EmulationFlags.DebuggerWindowEnabled, true);
 		}
@@ -497,7 +499,8 @@ namespace Mesen.GUI.Debugger
 				message = ResourceHelper.GetEnumText(source);
 				if(source == BreakSource.Breakpoint) {
 					int breakpointId = (int)(param >> 32);
-					BreakpointType bpType = (BreakpointType)(byte)(param >> 8);
+					BreakpointType bpType = (BreakpointType)(byte)((param >> 8) & 0x0F);
+					InteropMemoryOperationType memOpType = (InteropMemoryOperationType)(byte)((param >> 12) & 0x0F);
 					UInt16 bpAddress = (UInt16)(param >> 16);
 
 					ReadOnlyCollection<Breakpoint> breakpoints = BreakpointManager.Breakpoints;
@@ -506,9 +509,7 @@ namespace Mesen.GUI.Debugger
 						if(bpType != BreakpointType.Global) {
 							string prefix = "";
 							if(bpType == BreakpointType.ReadRam || bpType == BreakpointType.WriteRam) {
-								InstructionProgress progress = new InstructionProgress();
+								if(memOpType == InteropMemoryOperationType.DummyRead || memOpType == InteropMemoryOperationType.DummyWrite) {
-								InteropEmu.DebugGetInstructionProgress(ref progress);
-								if(progress.OpMemoryOperationType == InteropMemoryOperationType.DummyRead || progress.OpMemoryOperationType == InteropMemoryOperationType.DummyWrite) {
 									prefix = "(Dummy) ";
 								}
 							}
@@ -523,6 +524,9 @@ namespace Mesen.GUI.Debugger
 							}
 						}
 					}
+				} else if(source == BreakSource.BreakOnUninitMemoryRead) {
+					UInt16 address = (UInt16)(param >> 16);
+					message += " ($" + address.ToString("X4") + ")";
 				} else if(source == BreakSource.CpuStep || source == BreakSource.PpuStep) {
 					//Don't display anything when breaking due to stepping
 					message = null;
@@ -1190,6 +1194,13 @@ namespace Mesen.GUI.Debugger
 			ConfigManager.ApplyChanges();
 		}
 		
+		private void mnuBreakOnFirstCycle_Click(object sender, EventArgs e)
+		{
+			ConfigManager.Config.DebugInfo.BreakOnFirstCycle = !mnuEnableSubInstructionBreakpoints.Checked;
+			ConfigManager.ApplyChanges();
+			UpdateDebuggerFlags();
+		}
+
 		private void mnuBreakOnReset_Click(object sender, EventArgs e)
 		{
 			ConfigManager.Config.DebugInfo.BreakOnReset = mnuBreakOnReset.Checked;

GUI.NET/InteropEmu.cs

@@ -1322,6 +1322,8 @@ namespace Mesen.GUI
 		public UInt32 NmiScanline;
 		public UInt32 ScanlineCount;
 		public UInt32 SafeOamScanline;
+		public UInt16 BusAddress;
+		public byte MemoryReadBuffer;
 	}
 
 	public struct PPUState
@@ -1690,6 +1692,8 @@ namespace Mesen.GUI
 		BreakOnDecayedOamRead = 0x2000,
 		BreakOnInit = 0x4000,
 		BreakOnPlay = 0x8000,
+
+		BreakOnFirstCycle = 0x10000,
 	}
 
 	public struct InteropRomInfo