3eb16fe4e9
Previously, the SpecificAllocator was a static local in the `make<T>` function template. Using static locals is nice because they are only constructed and registered if they are accessed. However, if there are multiple calls to make<> with different constructor parameters, we would get multiple static local variable instances. This is undesirable and leads to extra memory allocations. I noticed there were two sources of DefinedRegular allocations while checking heap profiles.
69 lines
2.4 KiB
C++
69 lines
2.4 KiB
C++
//===- Memory.h -------------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines arena allocators.
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//
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// Almost all large objects, such as files, sections or symbols, are
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// used for the entire lifetime of the linker once they are created.
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// This usage characteristic makes arena allocator an attractive choice
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// where the entire linker is one arena. With an arena, newly created
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// objects belong to the arena and freed all at once when everything is done.
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// Arena allocators are efficient and easy to understand.
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// Most objects are allocated using the arena allocators defined by this file.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_COMMON_MEMORY_H
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#define LLD_COMMON_MEMORY_H
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/StringSaver.h"
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#include <vector>
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namespace lld {
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// Use this arena if your object doesn't have a destructor.
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extern llvm::BumpPtrAllocator bAlloc;
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extern llvm::StringSaver saver;
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void freeArena();
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// These two classes are hack to keep track of all
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// SpecificBumpPtrAllocator instances.
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struct SpecificAllocBase {
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SpecificAllocBase() { instances.push_back(this); }
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virtual ~SpecificAllocBase() = default;
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virtual void reset() = 0;
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static std::vector<SpecificAllocBase *> instances;
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};
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template <class T> struct SpecificAlloc : public SpecificAllocBase {
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void reset() override { alloc.DestroyAll(); }
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llvm::SpecificBumpPtrAllocator<T> alloc;
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};
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// Use a static local for these singletons so they are only registered if an
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// object of this instance is ever constructed. Otherwise we will create and
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// register ELF allocators for COFF and the reverse.
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template <typename T>
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inline llvm::SpecificBumpPtrAllocator<T> &getSpecificAllocSingleton() {
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static SpecificAlloc<T> instance;
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return instance.alloc;
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}
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// Use this arena if your object has a destructor.
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// Your destructor will be invoked from freeArena().
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template <typename T, typename... U> T *make(U &&... args) {
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return new (getSpecificAllocSingleton<T>().Allocate())
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T(std::forward<U>(args)...);
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}
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} // namespace lld
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#endif
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