Remove dumb CodeBlock duplication in the emitters.

Fixes issue 6990.
This uses a bit of templating to remove the duplicate code that is the CodeBlocks in each emitter headers.
No actual functionality change in this.

Source/Core/Common/CodeBlock.h

@@ -0,0 +1,76 @@
+// Copyright 2013 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "Common/Common.h"
+#include "Common/MemoryUtil.h"
+
+// Everything that needs to generate code should inherit from this.
+// You get memory management for free, plus, you can use all emitter functions without
+// having to prefix them with gen-> or something similar.
+// Example implementation:
+// class JIT : public CodeBlock<ARMXEmitter> {}
+template<class T> class CodeBlock : public T, NonCopyable
+{
+private:
+	// A privately used function to set the executable RAM space to something invalid.
+	// For debugging usefulness it should be used to set the RAM to a host specific breakpoint instruction
+	virtual void PoisonMemory() = 0;
+
+protected:
+	u8 *region;
+	size_t region_size;
+
+public:
+	CodeBlock() : region(nullptr), region_size(0) {}
+	virtual ~CodeBlock() { if (region) FreeCodeSpace(); }
+
+	// Call this before you generate any code.
+	void AllocCodeSpace(int size)
+	{
+		region_size = size;
+		region = (u8*)AllocateExecutableMemory(region_size);
+		T::SetCodePtr(region);
+	}
+
+	// Always clear code space with breakpoints, so that if someone accidentally executes
+	// uninitialized, it just breaks into the debugger.
+	void ClearCodeSpace()
+	{
+		PoisonMemory();
+		ResetCodePtr();
+	}
+
+	// Call this when shutting down. Don't rely on the destructor, even though it'll do the job.
+	void FreeCodeSpace()
+	{
+		FreeMemoryPages(region, region_size);
+		region = nullptr;
+		region_size = 0;
+	}
+
+	bool IsInSpace(u8 *ptr)
+	{
+		return (ptr >= region) && (ptr < (region + region_size));
+	}
+
+	// Cannot currently be undone. Will write protect the entire code region.
+	// Start over if you need to change the code (call FreeCodeSpace(), AllocCodeSpace()).
+	void WriteProtect()
+	{
+		WriteProtectMemory(region, region_size, true);
+	}
+
+	void ResetCodePtr()
+	{
+		T::SetCodePtr(region);
+	}
+
+	size_t GetSpaceLeft() const
+	{
+		return region_size - (T::GetCodePtr() - region);
+	}
+};
+