lib/Support/Allocator.cpp

   1 //===--- Allocator.cpp - Simple memory allocation abstraction -------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by Chris Lattner and is distributed under
   6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the BumpPtrAllocator interface.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/Allocator.h"
  15 #include "llvm/Support/DataTypes.h"
  16 #include "llvm/Support/Streams.h"
  17 #include <ostream>
  18 using namespace llvm;
  19
  20 //===----------------------------------------------------------------------===//
  21 // MemRegion class implementation
  22 //===----------------------------------------------------------------------===//
  23
  24 namespace {
  25 /// MemRegion - This is one chunk of the BumpPtrAllocator.
  26 class MemRegion {
  27   unsigned RegionSize;
  28   MemRegion *Next;
  29   char *NextPtr;
  30 public:
  31   void Init(unsigned size, unsigned Alignment, MemRegion *next) {
  32     RegionSize = size;
  33     Next = next;
  34     NextPtr = (char*)(this+1);
  35
  36     // Align NextPtr.
  37     NextPtr = (char*)((intptr_t)(NextPtr+Alignment-1) &
  38                       ~(intptr_t)(Alignment-1));
  39   }
  40
  41   const MemRegion *getNext() const { return Next; }
  42   unsigned getNumBytesAllocated() const {
  43     return NextPtr-(const char*)this;
  44   }
  45
  46   /// Allocate - Allocate and return at least the specified number of bytes.
  47   ///
  48   void *Allocate(unsigned AllocSize, unsigned Alignment, MemRegion **RegPtr) {
  49     // Round size up to an even multiple of the alignment.
  50     AllocSize = (AllocSize+Alignment-1) & ~(Alignment-1);
  51
  52     // If there is space in this region, return it.
  53     if (unsigned(NextPtr+AllocSize-(char*)this) <= RegionSize) {
  54       void *Result = NextPtr;
  55       NextPtr += AllocSize;
  56       return Result;
  57     }
  58
  59     // Otherwise, we have to allocate a new chunk.  Create one twice as big as
  60     // this one.
  61     MemRegion *NewRegion = (MemRegion *)malloc(RegionSize*2);
  62     NewRegion->Init(RegionSize*2, Alignment, this);
  63
  64     // Update the current "first region" pointer  to point to the new region.
  65     *RegPtr = NewRegion;
  66
  67     // Try allocating from it now.
  68     return NewRegion->Allocate(AllocSize, Alignment, RegPtr);
  69   }
  70
  71   /// Deallocate - Release all memory for this region to the system.
  72   ///
  73   void Deallocate() {
  74     MemRegion *next = Next;
  75     free(this);
  76     if (next)
  77       next->Deallocate();
  78   }
  79 };
  80 }
  81
  82 //===----------------------------------------------------------------------===//
  83 // BumpPtrAllocator class implementation
  84 //===----------------------------------------------------------------------===//
  85
  86 BumpPtrAllocator::BumpPtrAllocator() {
  87   TheMemory = malloc(4096);
  88   ((MemRegion*)TheMemory)->Init(4096, 1, 0);
  89 }
  90
  91 BumpPtrAllocator::~BumpPtrAllocator() {
  92   ((MemRegion*)TheMemory)->Deallocate();
  93 }
  94
  95 void *BumpPtrAllocator::Allocate(unsigned Size, unsigned Align) {
  96   MemRegion *MRP = (MemRegion*)TheMemory;
  97   void *Ptr = MRP->Allocate(Size, Align, &MRP);
  98   TheMemory = MRP;
  99   return Ptr;
 100 }
 101
 102 void BumpPtrAllocator::PrintStats() const {
 103   unsigned BytesUsed = 0;
 104   unsigned NumRegions = 0;
 105   const MemRegion *R = (MemRegion*)TheMemory;
 106   for (; R; R = R->getNext(), ++NumRegions)
 107     BytesUsed += R->getNumBytesAllocated();
 108
 109   cerr << "\nNumber of memory regions: " << NumRegions << "\n";
 110   cerr << "Bytes allocated: " << BytesUsed << "\n";
 111 }