dolphin/Source/Core/Common/CodeBlock.h

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// Copyright 2014 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <cstddef>
#include <vector>
#include "Common/Assert.h"
#include "Common/CommonTypes.h"
#include "Common/MemoryUtil.h"
namespace Common
{
// 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>
Remove NonCopyable The class NonCopyable is, like the name says, supposed to disallow copying. But should it allow moving? For a long time, NonCopyable used to not allow moving. (It declared a deleted copy constructor and assigment operator without declaring a move constructor and assignment operator, making the compiler implicitly delete the move constructor and assignment operator.) That's fine if the classes that inherit from NonCopyable don't need to be movable or if writing the move constructor and assignment operator by hand is fine, but that's not the case for all classes, as I discovered when I was working on the DirectoryBlob PR. Because of that, I decided to make NonCopyable movable in c7602cc, allowing me to use NonCopyable in DirectoryBlob.h. That was however an unfortunate decision, because some of the classes that inherit from NonCopyable have incorrect behavior when moved by default- generated move constructors and assignment operators, and do not explicitly delete the move constructors and assignment operators, relying on NonCopyable being non-movable. So what can we do about this? There are four solutions that I can think of: 1. Make NonCopyable non-movable and tell DirectoryBlob to suck it. 2. Keep allowing moving NonCopyable, and expect that classes that don't support moving will delete the move constructor and assignment operator manually. Not only is this inconsistent (having classes disallow copying one way and disallow moving another way), but deleting the move constructor and assignment operator manually is too easy to forget compared to how tricky the resulting problems are. 3. Have one "MovableNonCopyable" and one "NonMovableNonCopyable". It works, but it feels rather silly... 4. Don't have a NonCopyable class at all. Considering that deleting the copy constructor and assignment operator only takes two lines of code, I don't see much of a reason to keep NonCopyable. I suppose that there was more of a point in having NonCopyable back in the pre-C++11 days, when it wasn't possible to use "= delete". I decided to go with the fourth one (like the commit title says). The implementation of the commit is fairly straight-forward, though I would like to point out that I skipped adding "= delete" lines for classes whose only reason for being uncopyable is that they contain uncopyable classes like File::IOFile and std::unique_ptr, because the compiler makes such classes uncopyable automatically.
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class CodeBlock : public T
{
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 = nullptr;
// Size of region we can use.
size_t region_size = 0;
// Original size of the region we allocated.
size_t total_region_size = 0;
bool m_is_child = false;
std::vector<CodeBlock*> m_children;
public:
Remove NonCopyable The class NonCopyable is, like the name says, supposed to disallow copying. But should it allow moving? For a long time, NonCopyable used to not allow moving. (It declared a deleted copy constructor and assigment operator without declaring a move constructor and assignment operator, making the compiler implicitly delete the move constructor and assignment operator.) That's fine if the classes that inherit from NonCopyable don't need to be movable or if writing the move constructor and assignment operator by hand is fine, but that's not the case for all classes, as I discovered when I was working on the DirectoryBlob PR. Because of that, I decided to make NonCopyable movable in c7602cc, allowing me to use NonCopyable in DirectoryBlob.h. That was however an unfortunate decision, because some of the classes that inherit from NonCopyable have incorrect behavior when moved by default- generated move constructors and assignment operators, and do not explicitly delete the move constructors and assignment operators, relying on NonCopyable being non-movable. So what can we do about this? There are four solutions that I can think of: 1. Make NonCopyable non-movable and tell DirectoryBlob to suck it. 2. Keep allowing moving NonCopyable, and expect that classes that don't support moving will delete the move constructor and assignment operator manually. Not only is this inconsistent (having classes disallow copying one way and disallow moving another way), but deleting the move constructor and assignment operator manually is too easy to forget compared to how tricky the resulting problems are. 3. Have one "MovableNonCopyable" and one "NonMovableNonCopyable". It works, but it feels rather silly... 4. Don't have a NonCopyable class at all. Considering that deleting the copy constructor and assignment operator only takes two lines of code, I don't see much of a reason to keep NonCopyable. I suppose that there was more of a point in having NonCopyable back in the pre-C++11 days, when it wasn't possible to use "= delete". I decided to go with the fourth one (like the commit title says). The implementation of the commit is fairly straight-forward, though I would like to point out that I skipped adding "= delete" lines for classes whose only reason for being uncopyable is that they contain uncopyable classes like File::IOFile and std::unique_ptr, because the compiler makes such classes uncopyable automatically.
2017-08-04 23:57:12 +02:00
CodeBlock() = default;
virtual ~CodeBlock()
{
if (region)
FreeCodeSpace();
}
Remove NonCopyable The class NonCopyable is, like the name says, supposed to disallow copying. But should it allow moving? For a long time, NonCopyable used to not allow moving. (It declared a deleted copy constructor and assigment operator without declaring a move constructor and assignment operator, making the compiler implicitly delete the move constructor and assignment operator.) That's fine if the classes that inherit from NonCopyable don't need to be movable or if writing the move constructor and assignment operator by hand is fine, but that's not the case for all classes, as I discovered when I was working on the DirectoryBlob PR. Because of that, I decided to make NonCopyable movable in c7602cc, allowing me to use NonCopyable in DirectoryBlob.h. That was however an unfortunate decision, because some of the classes that inherit from NonCopyable have incorrect behavior when moved by default- generated move constructors and assignment operators, and do not explicitly delete the move constructors and assignment operators, relying on NonCopyable being non-movable. So what can we do about this? There are four solutions that I can think of: 1. Make NonCopyable non-movable and tell DirectoryBlob to suck it. 2. Keep allowing moving NonCopyable, and expect that classes that don't support moving will delete the move constructor and assignment operator manually. Not only is this inconsistent (having classes disallow copying one way and disallow moving another way), but deleting the move constructor and assignment operator manually is too easy to forget compared to how tricky the resulting problems are. 3. Have one "MovableNonCopyable" and one "NonMovableNonCopyable". It works, but it feels rather silly... 4. Don't have a NonCopyable class at all. Considering that deleting the copy constructor and assignment operator only takes two lines of code, I don't see much of a reason to keep NonCopyable. I suppose that there was more of a point in having NonCopyable back in the pre-C++11 days, when it wasn't possible to use "= delete". I decided to go with the fourth one (like the commit title says). The implementation of the commit is fairly straight-forward, though I would like to point out that I skipped adding "= delete" lines for classes whose only reason for being uncopyable is that they contain uncopyable classes like File::IOFile and std::unique_ptr, because the compiler makes such classes uncopyable automatically.
2017-08-04 23:57:12 +02:00
CodeBlock(const CodeBlock&) = delete;
CodeBlock& operator=(const CodeBlock&) = delete;
CodeBlock(CodeBlock&&) = delete;
CodeBlock& operator=(CodeBlock&&) = delete;
// Call this before you generate any code.
void AllocCodeSpace(size_t size)
{
region_size = size;
total_region_size = size;
region = static_cast<u8*>(Common::AllocateExecutableMemory(total_region_size));
T::SetCodePtr(region, region + size);
}
// 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()
{
ASSERT(!m_is_child);
Common::FreeMemoryPages(region, total_region_size);
region = nullptr;
region_size = 0;
total_region_size = 0;
for (CodeBlock* child : m_children)
{
child->region = nullptr;
child->region_size = 0;
child->total_region_size = 0;
}
}
bool IsInSpace(const u8* ptr) const { 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()).
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void WriteProtect() { Common::WriteProtectMemory(region, region_size, true); }
void ResetCodePtr() { T::SetCodePtr(region, region + region_size); }
size_t GetSpaceLeft() const
{
ASSERT(static_cast<size_t>(T::GetCodePtr() - region) < region_size);
return region_size - (T::GetCodePtr() - region);
}
bool IsAlmostFull() const
{
// This should be bigger than the biggest block ever.
return GetSpaceLeft() < 0x10000;
}
bool HasChildren() const { return region_size != total_region_size; }
u8* AllocChildCodeSpace(size_t child_size)
{
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ASSERT_MSG(DYNA_REC, child_size < GetSpaceLeft(), "Insufficient space for child allocation.");
u8* child_region = region + region_size - child_size;
region_size -= child_size;
return child_region;
}
void AddChildCodeSpace(CodeBlock* child, size_t child_size)
{
u8* child_region = AllocChildCodeSpace(child_size);
child->m_is_child = true;
child->region = child_region;
child->region_size = child_size;
child->total_region_size = child_size;
child->ResetCodePtr();
m_children.emplace_back(child);
}
};
} // namespace Common