MMIO: Lazy-initialize read/write handlers since most are not actually used

3 files changed, 51 insertions, 21 deletions

diff --git a/Source/Core/Core/HW/MMIO.cpp b/Source/Core/Core/HW/MMIO.cpp
index f8cbe9ee18..d1b37e5c54 100644
--- a/Source/Core/Core/HW/MMIO.cpp
+++ b/Source/Core/Core/HW/MMIO.cpp
@@ -224,8 +224,8 @@ ReadHandlingMethod<T>* ReadToSmaller(Mapping* mmio, u32 high_part_addr, u32 low_
 {
 	typedef typename SmallerAccessSize<T>::value ST;
 
-	const ReadHandler<ST>* high_part;
-	const ReadHandler<ST>* low_part;
+	ReadHandler<ST>* high_part;
+	ReadHandler<ST>* low_part;
 	mmio->GetHandlerForRead(high_part_addr, &high_part);
 	mmio->GetHandlerForRead(low_part_addr, &low_part);
 
@@ -241,8 +241,8 @@ WriteHandlingMethod<T>* WriteToSmaller(Mapping* mmio, u32 high_part_addr, u32 lo
 {
 	typedef typename SmallerAccessSize<T>::value ST;
 
-	const WriteHandler<ST>* high_part;
-	const WriteHandler<ST>* low_part;
+	WriteHandler<ST>* high_part;
+	WriteHandler<ST>* low_part;
 	mmio->GetHandlerForWrite(high_part_addr, &high_part);
 	mmio->GetHandlerForWrite(low_part_addr, &low_part);
 
@@ -258,7 +258,7 @@ ReadHandlingMethod<T>* ReadToLarger(Mapping* mmio, u32 larger_addr, u32 shift)
 {
 	typedef typename LargerAccessSize<T>::value LT;
 
-	const ReadHandler<LT>* large;
+	ReadHandler<LT>* large;
 	mmio->GetHandlerForRead(larger_addr, &large);
 
 	// TODO(delroth): optimize
@@ -271,9 +271,8 @@ ReadHandlingMethod<T>* ReadToLarger(Mapping* mmio, u32 larger_addr, u32 shift)
 // redundant code between these two classes but trying to abstract it away
 // brings more trouble than it fixes.
 template <typename T>
-ReadHandler<T>::ReadHandler() : m_Method(nullptr)
+ReadHandler<T>::ReadHandler()
 {
-	ResetMethod(InvalidRead<T>());
 }
 
 template <typename T>
@@ -289,8 +288,11 @@ ReadHandler<T>::~ReadHandler()
 }
 
 template <typename T>
-void ReadHandler<T>::Visit(ReadHandlingMethodVisitor<T>& visitor) const
+void ReadHandler<T>::Visit(ReadHandlingMethodVisitor<T>& visitor)
 {
+	if (!m_Method)
+		InitializeInvalid();
+
 	m_Method->AcceptReadVisitor(visitor);
 }
 
@@ -325,9 +327,8 @@ void ReadHandler<T>::ResetMethod(ReadHandlingMethod<T>* method)
 }
 
 template <typename T>
-WriteHandler<T>::WriteHandler() : m_Method(nullptr)
+WriteHandler<T>::WriteHandler()
 {
-	ResetMethod(InvalidWrite<T>());
 }
 
 template <typename T>
@@ -343,8 +344,11 @@ WriteHandler<T>::~WriteHandler()
 }
 
 template <typename T>
-void WriteHandler<T>::Visit(WriteHandlingMethodVisitor<T>& visitor) const
+void WriteHandler<T>::Visit(WriteHandlingMethodVisitor<T>& visitor)
 {
+	if (!m_Method)
+		InitializeInvalid();
+
 	m_Method->AcceptWriteVisitor(visitor);
 }
 
diff --git a/Source/Core/Core/HW/MMIO.h b/Source/Core/Core/HW/MMIO.h
index 28fe19ba5a..721689fb54 100644
--- a/Source/Core/Core/HW/MMIO.h
+++ b/Source/Core/Core/HW/MMIO.h
@@ -105,7 +105,7 @@ public:
 	// Note that for reads we cannot simply return the read value because C++
 	// allows overloading only with parameter types, not return types.
 #define READ_FUNC(Size) \
-	void Read(u32 addr, u##Size* val) const \
+	void Read(u32 addr, u##Size* val) \
 	{ \
 		u32 id = UniqueID(addr) / sizeof (u##Size); \
 		*val = m_Read##Size##Handlers[id].Read(addr); \
@@ -114,7 +114,7 @@ public:
 #undef READ_FUNC
 
 #define WRITE_FUNC(Size) \
-	void Write(u32 addr, u##Size val) const \
+	void Write(u32 addr, u##Size val) \
 	{ \
 		u32 id = UniqueID(addr) / sizeof (u##Size); \
 		m_Write##Size##Handlers[id].Write(addr, val); \
@@ -133,11 +133,11 @@ public:
 	// value. This second variant is needed because C++ doesn't do overloads
 	// based on return type but only based on argument types.
 #define GET_HANDLERS_FUNC(Type, Size) \
-	const Type##Handler<u##Size>& GetHandlerFor##Type##Size(u32 addr) const \
+	Type##Handler<u##Size>& GetHandlerFor##Type##Size(u32 addr) \
 	{ \
 		return m_##Type##Size##Handlers[UniqueID(addr) / sizeof (u##Size)]; \
 	} \
-	void GetHandlerFor##Type(u32 addr, const Type##Handler<u##Size>** h) const \
+	void GetHandlerFor##Type(u32 addr, Type##Handler<u##Size>** h) \
 	{ \
 		*h = &GetHandlerFor##Type##Size(addr); \
 	}
@@ -147,8 +147,8 @@ public:
 
 	// Dummy 64 bits variants of these functions. While 64 bits MMIO access is
 	// not supported, we need these in order to make the code compile.
-	void Read(u32 addr, u64* val) const { _dbg_assert_(MEMMAP, 0); }
-	void Write(u32 addr, u64 val) const { _dbg_assert_(MEMMAP, 0); }
+	void Read(u32 addr, u64* val) { _dbg_assert_(MEMMAP, 0); }
+	void Write(u32 addr, u64 val) { _dbg_assert_(MEMMAP, 0); }
 
 private:
 	// These arrays contain the handlers for each MMIO access type: read/write
diff --git a/Source/Core/Core/HW/MMIOHandlers.h b/Source/Core/Core/HW/MMIOHandlers.h
index 7afe9f60b5..8fc3c25e6d 100644
--- a/Source/Core/Core/HW/MMIOHandlers.h
+++ b/Source/Core/Core/HW/MMIOHandlers.h
@@ -115,10 +115,16 @@ public:
 	~ReadHandler();
 
 	// Entry point for read handling method visitors.
-	void Visit(ReadHandlingMethodVisitor<T>& visitor) const;
+	void Visit(ReadHandlingMethodVisitor<T>& visitor);
 
-	T Read(u32 addr) const
+	T Read(u32 addr)
 	{
+		// Check if the handler has already been initialized. For real
+		// handlers, this will always be the case, so this branch should be
+		// easily predictable.
+		if (!m_Method)
+			InitializeInvalid();
+
 		return m_ReadFunc(addr);
 	}
 
@@ -127,6 +133,13 @@ public:
 	void ResetMethod(ReadHandlingMethod<T>* method);
 
 private:
+	// Initialize this handler to an invalid handler. Done lazily to avoid
+	// useless initialization of thousands of unused handler objects.
+	void InitializeInvalid()
+	{
+		ResetMethod(InvalidRead<T>());
+	}
+
 	std::unique_ptr<ReadHandlingMethod<T>> m_Method;
 	std::function<T(u32)> m_ReadFunc;
 };
@@ -142,10 +155,16 @@ public:
 	~WriteHandler();
 
 	// Entry point for write handling method visitors.
-	void Visit(WriteHandlingMethodVisitor<T>& visitor) const;
+	void Visit(WriteHandlingMethodVisitor<T>& visitor);
 
-	void Write(u32 addr, T val) const
+	void Write(u32 addr, T val)
 	{
+		// Check if the handler has already been initialized. For real
+		// handlers, this will always be the case, so this branch should be
+		// easily predictable.
+		if (!m_Method)
+			InitializeInvalid();
+
 		m_WriteFunc(addr, val);
 	}
 
@@ -155,6 +174,13 @@ public:
 	void ResetMethod(WriteHandlingMethod<T>* method);
 
 private:
+	// Initialize this handler to an invalid handler. Done lazily to avoid
+	// useless initialization of thousands of unused handler objects.
+	void InitializeInvalid()
+	{
+		ResetMethod(InvalidWrite<T>());
+	}
+
 	std::unique_ptr<WriteHandlingMethod<T>> m_Method;
 	std::function<void(u32, T)> m_WriteFunc;
 };