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179 lines
5.6 KiB
C++
179 lines
5.6 KiB
C++
//===--- Allocator.h - Simple memory allocation abstraction -----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MallocAllocator and BumpPtrAllocator interfaces.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_ALLOCATOR_H
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#define LLVM_SUPPORT_ALLOCATOR_H
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#include "llvm/Support/AlignOf.h"
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#include "llvm/System/DataTypes.h"
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#include <cassert>
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#include <cstdlib>
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namespace llvm {
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class MallocAllocator {
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public:
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MallocAllocator() {}
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~MallocAllocator() {}
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void Reset() {}
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void *Allocate(size_t Size, size_t /*Alignment*/) { return malloc(Size); }
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template <typename T>
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T *Allocate() { return static_cast<T*>(malloc(sizeof(T))); }
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template <typename T>
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T *Allocate(size_t Num) {
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return static_cast<T*>(malloc(sizeof(T)*Num));
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}
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void Deallocate(const void *Ptr) { free(const_cast<void*>(Ptr)); }
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void PrintStats() const {}
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};
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/// MemSlab - This structure lives at the beginning of every slab allocated by
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/// the bump allocator.
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class MemSlab {
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public:
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size_t Size;
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MemSlab *NextPtr;
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};
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/// SlabAllocator - This class can be used to parameterize the underlying
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/// allocation strategy for the bump allocator. In particular, this is used
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/// by the JIT to allocate contiguous swathes of executable memory. The
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/// interface uses MemSlab's instead of void *'s so that the allocator
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/// doesn't have to remember the size of the pointer it allocated.
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class SlabAllocator {
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public:
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virtual ~SlabAllocator();
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virtual MemSlab *Allocate(size_t Size) = 0;
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virtual void Deallocate(MemSlab *Slab) = 0;
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};
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/// MallocSlabAllocator - The default slab allocator for the bump allocator
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/// is an adapter class for MallocAllocator that just forwards the method
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/// calls and translates the arguments.
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class MallocSlabAllocator : public SlabAllocator {
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/// Allocator - The underlying allocator that we forward to.
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///
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MallocAllocator Allocator;
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public:
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MallocSlabAllocator() : Allocator() { }
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virtual ~MallocSlabAllocator();
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virtual MemSlab *Allocate(size_t Size);
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virtual void Deallocate(MemSlab *Slab);
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};
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/// BumpPtrAllocator - This allocator is useful for containers that need
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/// very simple memory allocation strategies. In particular, this just keeps
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/// allocating memory, and never deletes it until the entire block is dead. This
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/// makes allocation speedy, but must only be used when the trade-off is ok.
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class BumpPtrAllocator {
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BumpPtrAllocator(const BumpPtrAllocator &); // do not implement
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void operator=(const BumpPtrAllocator &); // do not implement
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/// SlabSize - Allocate data into slabs of this size unless we get an
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/// allocation above SizeThreshold.
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size_t SlabSize;
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/// SizeThreshold - For any allocation larger than this threshold, we should
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/// allocate a separate slab.
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size_t SizeThreshold;
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/// Allocator - The underlying allocator we use to get slabs of memory. This
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/// defaults to MallocSlabAllocator, which wraps malloc, but it could be
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/// changed to use a custom allocator.
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SlabAllocator &Allocator;
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/// CurSlab - The slab that we are currently allocating into.
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///
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MemSlab *CurSlab;
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/// CurPtr - The current pointer into the current slab. This points to the
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/// next free byte in the slab.
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char *CurPtr;
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/// End - The end of the current slab.
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///
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char *End;
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/// BytesAllocated - This field tracks how many bytes we've allocated, so
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/// that we can compute how much space was wasted.
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size_t BytesAllocated;
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/// AlignPtr - Align Ptr to Alignment bytes, rounding up. Alignment should
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/// be a power of two. This method rounds up, so AlignPtr(7, 4) == 8 and
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/// AlignPtr(8, 4) == 8.
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static char *AlignPtr(char *Ptr, size_t Alignment);
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/// StartNewSlab - Allocate a new slab and move the bump pointers over into
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/// the new slab. Modifies CurPtr and End.
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void StartNewSlab();
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/// DeallocateSlabs - Deallocate all memory slabs after and including this
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/// one.
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void DeallocateSlabs(MemSlab *Slab);
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static MallocSlabAllocator DefaultSlabAllocator;
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public:
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BumpPtrAllocator(size_t size = 4096, size_t threshold = 4096,
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SlabAllocator &allocator = DefaultSlabAllocator);
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~BumpPtrAllocator();
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/// Reset - Deallocate all but the current slab and reset the current pointer
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/// to the beginning of it, freeing all memory allocated so far.
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void Reset();
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/// Allocate - Allocate space at the specified alignment.
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///
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void *Allocate(size_t Size, size_t Alignment);
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/// Allocate space, but do not construct, one object.
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///
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template <typename T>
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T *Allocate() {
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return static_cast<T*>(Allocate(sizeof(T),AlignOf<T>::Alignment));
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}
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/// Allocate space for an array of objects. This does not construct the
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/// objects though.
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template <typename T>
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T *Allocate(size_t Num) {
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return static_cast<T*>(Allocate(Num * sizeof(T), AlignOf<T>::Alignment));
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}
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/// Allocate space for a specific count of elements and with a specified
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/// alignment.
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template <typename T>
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T *Allocate(size_t Num, size_t Alignment) {
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// Round EltSize up to the specified alignment.
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size_t EltSize = (sizeof(T)+Alignment-1)&(-Alignment);
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return static_cast<T*>(Allocate(Num * EltSize, Alignment));
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}
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void Deallocate(const void * /*Ptr*/) {}
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unsigned GetNumSlabs() const;
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void PrintStats() const;
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};
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} // end namespace llvm
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#endif // LLVM_SUPPORT_ALLOCATOR_H
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