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//===--- Allocator.cpp - Simple memory allocation abstraction -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the BumpPtrAllocator interface.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/Allocator.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Streams.h"
#include <ostream>
using namespace llvm;
//===----------------------------------------------------------------------===//
// MemRegion class implementation
//===----------------------------------------------------------------------===//
namespace {
/// MemRegion - This is one chunk of the BumpPtrAllocator.
class MemRegion {
unsigned RegionSize;
MemRegion *Next;
char *NextPtr;
public:
void Init(unsigned size, unsigned Alignment, MemRegion *next) {
RegionSize = size;
Next = next;
NextPtr = (char*)(this+1);
// Align NextPtr.
NextPtr = (char*)((intptr_t)(NextPtr+Alignment-1) &
~(intptr_t)(Alignment-1));
}
const MemRegion *getNext() const { return Next; }
unsigned getNumBytesAllocated() const {
return NextPtr-(const char*)this;
}
/// Allocate - Allocate and return at least the specified number of bytes.
///
void *Allocate(unsigned AllocSize, unsigned Alignment, MemRegion **RegPtr) {
// Round size up to an even multiple of the alignment.
AllocSize = (AllocSize+Alignment-1) & ~(Alignment-1);
// If there is space in this region, return it.
if (unsigned(NextPtr+AllocSize-(char*)this) <= RegionSize) {
void *Result = NextPtr;
NextPtr += AllocSize;
return Result;
}
// Otherwise, we have to allocate a new chunk. Create one twice as big as
// this one.
MemRegion *NewRegion = (MemRegion *)malloc(RegionSize*2);
NewRegion->Init(RegionSize*2, Alignment, this);
// Update the current "first region" pointer to point to the new region.
*RegPtr = NewRegion;
// Try allocating from it now.
return NewRegion->Allocate(AllocSize, Alignment, RegPtr);
}
/// Deallocate - Recursively release all memory for this and its next regions
/// to the system.
void Deallocate() {
MemRegion *next = Next;
free(this);
if (next)
next->Deallocate();
}
/// DeallocateAllButLast - Recursively release all memory for this and its
/// next regions to the system stopping at the last region in the list.
/// Returns the pointer to the last region.
MemRegion *DeallocateAllButLast() {
MemRegion *next = Next;
if (!next)
return this;
free(this);
return next->DeallocateAllButLast();
}
};
}
//===----------------------------------------------------------------------===//
// BumpPtrAllocator class implementation
//===----------------------------------------------------------------------===//
BumpPtrAllocator::BumpPtrAllocator() {
TheMemory = malloc(4096);
((MemRegion*)TheMemory)->Init(4096, 1, 0);
}
BumpPtrAllocator::~BumpPtrAllocator() {
((MemRegion*)TheMemory)->Deallocate();
}
void BumpPtrAllocator::Reset() {
MemRegion *MRP = (MemRegion*)TheMemory;
MRP = MRP->DeallocateAllButLast();
MRP->Init(4096, 1, 0);
TheMemory = MRP;
}
void *BumpPtrAllocator::Allocate(unsigned Size, unsigned Align) {
MemRegion *MRP = (MemRegion*)TheMemory;
void *Ptr = MRP->Allocate(Size, Align, &MRP);
TheMemory = MRP;
return Ptr;
}
void BumpPtrAllocator::PrintStats() const {
unsigned BytesUsed = 0;
unsigned NumRegions = 0;
const MemRegion *R = (MemRegion*)TheMemory;
for (; R; R = R->getNext(), ++NumRegions)
BytesUsed += R->getNumBytesAllocated();
cerr << "\nNumber of memory regions: " << NumRegions << "\n";
cerr << "Bytes allocated: " << BytesUsed << "\n";
}
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