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9f617d64c5
I'm about to add. This is similar to, but necessarily different than, the STL allocator class. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31285 91177308-0d34-0410-b5e6-96231b3b80d8
107 lines
3.3 KiB
C++
107 lines
3.3 KiB
C++
//===--- Allocator.cpp - Simple memory allocation abstraction -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the BumpPtrAllocator interface.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/Allocator.h"
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#include <iostream>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// MemRegion class implementation
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//===----------------------------------------------------------------------===//
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namespace {
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/// MemRegion - This is one chunk of the BumpPtrAllocator.
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class MemRegion {
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unsigned RegionSize;
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MemRegion *Next;
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char *NextPtr;
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public:
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void Init(unsigned size, unsigned Alignment, MemRegion *next) {
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RegionSize = size;
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Next = next;
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NextPtr = (char*)(this+1);
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// Align NextPtr.
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NextPtr = (char*)((intptr_t)(NextPtr+Alignment-1) &
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~(intptr_t)(Alignment-1));
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}
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const MemRegion *getNext() const { return Next; }
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unsigned getNumBytesAllocated() const {
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return NextPtr-(const char*)this;
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}
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/// Allocate - Allocate and return at least the specified number of bytes.
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///
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void *Allocate(unsigned AllocSize, unsigned Alignment, MemRegion **RegPtr) {
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// Round size up to an even multiple of the alignment.
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AllocSize = (AllocSize+Alignment-1) & ~(Alignment-1);
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// If there is space in this region, return it.
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if (unsigned(NextPtr+AllocSize-(char*)this) <= RegionSize) {
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void *Result = NextPtr;
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NextPtr += AllocSize;
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return Result;
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}
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// Otherwise, we have to allocate a new chunk. Create one twice as big as
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// this one.
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MemRegion *NewRegion = (MemRegion *)malloc(RegionSize*2);
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NewRegion->Init(RegionSize*2, Alignment, this);
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// Update the current "first region" pointer to point to the new region.
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*RegPtr = NewRegion;
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// Try allocating from it now.
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return NewRegion->Allocate(AllocSize, Alignment, RegPtr);
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}
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/// Deallocate - Release all memory for this region to the system.
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///
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void Deallocate() {
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MemRegion *next = Next;
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free(this);
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if (next)
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next->Deallocate();
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}
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};
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}
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//===----------------------------------------------------------------------===//
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// BumpPtrAllocator class implementation
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//===----------------------------------------------------------------------===//
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BumpPtrAllocator::BumpPtrAllocator() {
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TheMemory = malloc(4096);
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((MemRegion*)TheMemory)->Init(4096, 1, 0);
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}
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BumpPtrAllocator::~BumpPtrAllocator() {
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((MemRegion*)TheMemory)->Deallocate();
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}
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void *BumpPtrAllocator::Allocate(unsigned Size, unsigned Align) {
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return ((MemRegion*)TheMemory)->Allocate(Size, Align,(MemRegion**)&TheMemory);
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}
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void BumpPtrAllocator::PrintStats() const {
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unsigned BytesUsed = 0;
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unsigned NumRegions = 0;
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const MemRegion *R = (MemRegion*)TheMemory;
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for (; R; R = R->getNext(), ++NumRegions)
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BytesUsed += R->getNumBytesAllocated();
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std::cerr << "\nNumber of memory regions: " << NumRegions << "\n";
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std::cerr << "Bytes allocated: " << BytesUsed << "\n";
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}
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