1
//===--- Allocator.cpp - Simple memory allocation abstraction -------------===//
3
// The LLVM Compiler Infrastructure
5
// This file is distributed under the University of Illinois Open Source
6
// License. See LICENSE.TXT for details.
8
//===----------------------------------------------------------------------===//
10
// This file implements the BumpPtrAllocator interface.
12
//===----------------------------------------------------------------------===//
14
#include "llvm/Support/Allocator.h"
15
#include "llvm/System/DataTypes.h"
16
#include "llvm/Support/Recycler.h"
17
#include "llvm/Support/raw_ostream.h"
18
#include "llvm/System/Memory.h"
23
BumpPtrAllocator::BumpPtrAllocator(size_t size, size_t threshold,
24
SlabAllocator &allocator)
25
: SlabSize(size), SizeThreshold(threshold), Allocator(allocator),
26
CurSlab(0), BytesAllocated(0) {
30
BumpPtrAllocator::~BumpPtrAllocator() {
31
DeallocateSlabs(CurSlab);
34
/// AlignPtr - Align Ptr to Alignment bytes, rounding up. Alignment should
35
/// be a power of two. This method rounds up, so AlignPtr(7, 4) == 8 and
36
/// AlignPtr(8, 4) == 8.
37
char *BumpPtrAllocator::AlignPtr(char *Ptr, size_t Alignment) {
38
assert(Alignment && (Alignment & (Alignment - 1)) == 0 &&
39
"Alignment is not a power of two!");
42
return (char*)(((uintptr_t)Ptr + Alignment - 1) &
43
~(uintptr_t)(Alignment - 1));
46
/// StartNewSlab - Allocate a new slab and move the bump pointers over into
47
/// the new slab. Modifies CurPtr and End.
48
void BumpPtrAllocator::StartNewSlab() {
49
MemSlab *NewSlab = Allocator.Allocate(SlabSize);
50
NewSlab->NextPtr = CurSlab;
52
CurPtr = (char*)(CurSlab + 1);
53
End = ((char*)CurSlab) + CurSlab->Size;
56
/// DeallocateSlabs - Deallocate all memory slabs after and including this
58
void BumpPtrAllocator::DeallocateSlabs(MemSlab *Slab) {
60
MemSlab *NextSlab = Slab->NextPtr;
62
// Poison the memory so stale pointers crash sooner. Note we must
63
// preserve the Size and NextPtr fields at the beginning.
64
sys::Memory::setRangeWritable(Slab + 1, Slab->Size - sizeof(MemSlab));
65
memset(Slab + 1, 0xCD, Slab->Size - sizeof(MemSlab));
67
Allocator.Deallocate(Slab);
72
/// Reset - Deallocate all but the current slab and reset the current pointer
73
/// to the beginning of it, freeing all memory allocated so far.
74
void BumpPtrAllocator::Reset() {
75
DeallocateSlabs(CurSlab->NextPtr);
77
CurPtr = (char*)(CurSlab + 1);
78
End = ((char*)CurSlab) + CurSlab->Size;
81
/// Allocate - Allocate space at the specified alignment.
83
void *BumpPtrAllocator::Allocate(size_t Size, size_t Alignment) {
84
// Keep track of how many bytes we've allocated.
85
BytesAllocated += Size;
87
// 0-byte alignment means 1-byte alignment.
88
if (Alignment == 0) Alignment = 1;
90
// Allocate the aligned space, going forwards from CurPtr.
91
char *Ptr = AlignPtr(CurPtr, Alignment);
93
// Check if we can hold it.
94
if (Ptr + Size <= End) {
99
// If Size is really big, allocate a separate slab for it.
100
size_t PaddedSize = Size + sizeof(MemSlab) + Alignment - 1;
101
if (PaddedSize > SizeThreshold) {
102
MemSlab *NewSlab = Allocator.Allocate(PaddedSize);
104
// Put the new slab after the current slab, since we are not allocating
106
NewSlab->NextPtr = CurSlab->NextPtr;
107
CurSlab->NextPtr = NewSlab;
109
Ptr = AlignPtr((char*)(NewSlab + 1), Alignment);
110
assert((uintptr_t)Ptr + Size <= (uintptr_t)NewSlab + NewSlab->Size);
114
// Otherwise, start a new slab and try again.
116
Ptr = AlignPtr(CurPtr, Alignment);
118
assert(CurPtr <= End && "Unable to allocate memory!");
122
unsigned BumpPtrAllocator::GetNumSlabs() const {
123
unsigned NumSlabs = 0;
124
for (MemSlab *Slab = CurSlab; Slab != 0; Slab = Slab->NextPtr) {
130
void BumpPtrAllocator::PrintStats() const {
131
unsigned NumSlabs = 0;
132
size_t TotalMemory = 0;
133
for (MemSlab *Slab = CurSlab; Slab != 0; Slab = Slab->NextPtr) {
134
TotalMemory += Slab->Size;
138
errs() << "\nNumber of memory regions: " << NumSlabs << '\n'
139
<< "Bytes used: " << BytesAllocated << '\n'
140
<< "Bytes allocated: " << TotalMemory << '\n'
141
<< "Bytes wasted: " << (TotalMemory - BytesAllocated)
142
<< " (includes alignment, etc)\n";
145
MallocSlabAllocator BumpPtrAllocator::DefaultSlabAllocator =
146
MallocSlabAllocator();
148
SlabAllocator::~SlabAllocator() { }
150
MallocSlabAllocator::~MallocSlabAllocator() { }
152
MemSlab *MallocSlabAllocator::Allocate(size_t Size) {
153
MemSlab *Slab = (MemSlab*)Allocator.Allocate(Size, 0);
159
void MallocSlabAllocator::Deallocate(MemSlab *Slab) {
160
Allocator.Deallocate(Slab);
163
void PrintRecyclerStats(size_t Size,
165
size_t FreeListSize) {
166
errs() << "Recycler element size: " << Size << '\n'
167
<< "Recycler element alignment: " << Align << '\n'
168
<< "Number of elements free for recycling: " << FreeListSize << '\n';