llvm-6502/include/llvm/Support/Allocator.h
2009-07-23 18:34:13 +00:00

179 lines
5.6 KiB
C++

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