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memory.h
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memory.h
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/*!
* \file tvm/runtime/memory.h
* \brief Runtime memory management.
*/
#ifndef TVM_RUNTIME_MEMORY_H_
#define TVM_RUNTIME_MEMORY_H_
#include <cstdlib>
#include <utility>
#include <type_traits>
#include "object.h"
namespace tvm {
namespace runtime {
/*!
* \brief Allocate an object using default allocator.
* \param args arguments to the constructor.
* \tparam T the node type.
* \return The ObjectPtr to the allocated object.
*/
template<typename T, typename... Args>
inline ObjectPtr<T> make_object(Args&&... args);
// Detail implementations after this
//
// The current design allows swapping the
// allocator pattern when necessary.
//
// Possible future allocator optimizations:
// - Arena allocator that gives ownership of memory to arena (deleter_= nullptr)
// - Thread-local object pools: one pool per size and alignment requirement.
// - Can specialize by type of object to give the specific allocator to each object.
/*!
* \brief Base class of object allocators that implements make.
* Use curiously recurring template pattern.
*
* \tparam Derived The derived class.
*/
template<typename Derived>
class ObjAllocatorBase {
public:
/*!
* \tparam T The type to be allocated.
* \tparam Args The constructor signature.
* \param args The arguments.
*/
template<typename T, typename... Args>
inline ObjectPtr<T> make(Args&&... args) {
using Handler = typename Derived::template Handler<T>;
static_assert(std::is_base_of<Object, T>::value,
"make_node can only be used to create NodeBase");
T* ptr = Handler::New(static_cast<Derived*>(this),
std::forward<Args>(args)...);
ptr->type_index_ = T::RuntimeTypeIndex();
ptr->deleter_ = Handler::Deleter();
return ObjectPtr<T>(ptr);
}
/*!
* \tparam T The type to be allocated.
* \tparam ElemType The type to array element.
* \tparam Args The constructor signature.
* \param num_elems The number of array elements.
* \param args The arguments.
*/
template<typename T, typename ElemType, typename... Args>
inline ObjectPtr<T> make_array(size_t num_elems, Args&&... args) {
using Handler = typename Derived::template Handler<T, ElemType>;
static_assert(std::is_base_of<Object, T>::value,
"make_node can only be used to create NodeBase");
T* ptr = Handler::New(static_cast<Derived*>(this),
num_elems,
std::forward<Args>(args)...);
ptr->type_index_ = T::RuntimeTypeIndex();
ptr->deleter_ = Handler::Deleter();
return ObjectPtr<T>(ptr);
}
};
// Simple allocator that uses new/delete.
class SimpleObjAllocator :
public ObjAllocatorBase<SimpleObjAllocator> {
public:
template<typename T>
class Handler {
public:
using StorageType = typename std::aligned_storage<sizeof(T), alignof(T)>::type;
template<typename... Args>
static T* New(SimpleObjAllocator*, Args&&... args) {
// NOTE: the first argument is not needed for SimpleObjAllocator
// It is reserved for special allocators that needs to recycle
// the object to itself (e.g. in the case of object pool).
//
// In the case of an object pool, an allocator needs to create
// a special chunk memory that hides reference to the allocator
// and call allocator's release function in the deleter.
// NOTE2: Use inplace new to allocate
// This is used to get rid of warning when deleting a virtual
// class with non-virtual destructor.
// We are fine here as we captured the right deleter during construction.
// This is also the right way to get storage type for an object pool.
StorageType* data = new StorageType();
new (data) T(std::forward<Args>(args)...);
return reinterpret_cast<T*>(data);
}
static Object::FDeleter Deleter() {
return Deleter_;
}
private:
static void Deleter_(Object* objptr) {
// NOTE: this is important to cast back to T*
// because objptr and tptr may not be the same
// depending on how sub-class allocates the space.
T* tptr = static_cast<T*>(objptr);
// It is important to do tptr->T::~T(),
// so that we explicitly call the specific destructor
// instead of tptr->~T(), which could mean the intention
// call a virtual destructor(which may not be available and is not required).
tptr->T::~T();
delete reinterpret_cast<StorageType*>(tptr);
}
};
};
// Array allocator that uses new/delete.
class ArrayObjAllocator :
public ObjAllocatorBase<ArrayObjAllocator> {
public:
template<typename ArrayType, typename ElemType>
class Handler {
public:
using StorageType = typename std::aligned_union<sizeof(ArrayType), ArrayType, ElemType>::type;
template<typename... Args>
static ArrayType* New(ArrayObjAllocator*, size_t num_elems, Args&&... args) {
// NOTE: the first argument is not needed for ArrayObjAllocator
// It is reserved for special allocators that needs to recycle
// the object to itself (e.g. in the case of object pool).
//
// In the case of an object pool, an allocator needs to create
// a special chunk memory that hides reference to the allocator
// and call allocator's release function in the deleter.
// NOTE2: Use inplace new to allocate
// This is used to get rid of warning when deleting a virtual
// class with non-virtual destructor.
// We are fine here as we captured the right deleter during construction.
// This is also the right way to get storage type for an object pool.
size_t factor = sizeof(ArrayType) / sizeof(ElemType);
num_elems = (num_elems + factor - 1) / factor;
StorageType* data = new StorageType[num_elems+1];
new (data) ArrayType(std::forward<Args>(args)...);
return reinterpret_cast<ArrayType*>(data);
}
static Object::FDeleter Deleter() {
return Deleter_;
}
private:
static void Deleter_(Object* objptr) {
// NOTE: this is important to cast back to ArrayType*
// because objptr and tptr may not be the same
// depending on how sub-class allocates the space.
ArrayType* tptr = static_cast<ArrayType*>(objptr);
// It is important to do tptr->ArrayType::~ArrayType(),
// so that we explicitly call the specific destructor
// instead of tptr->~ArrayType(), which could mean the intention
// call a virtual destructor(which may not be available and is not required).
tptr->ArrayType::~ArrayType();
StorageType* p = reinterpret_cast<StorageType*>(tptr);
delete []p;
}
};
};
template<typename T, typename... Args>
inline ObjectPtr<T> make_object(Args&&... args) {
return SimpleObjAllocator().make<T>(std::forward<Args>(args)...);
}
template<typename T, typename ElemType, typename... Args>
inline ObjectPtr<T> make_array(size_t num_elems, Args&&... args) {
return ArrayObjAllocator().make_array<T, ElemType>(num_elems, std::forward<Args>(args)...);
}
} // namespace runtime
} // namespace tvm
#endif // TVM_RUNTIME_MEMORY_H_