189 lines
5.8 KiB
C++
189 lines
5.8 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 is distributed under the University of Illinois Open Source
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// 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 "llvm/Support/DataTypes.h"
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#include "llvm/Support/Recycler.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/Memory.h"
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#include <cstring>
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namespace llvm {
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BumpPtrAllocator::BumpPtrAllocator(size_t size, size_t threshold,
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SlabAllocator &allocator)
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: SlabSize(size), SizeThreshold(threshold), Allocator(allocator),
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CurSlab(0), BytesAllocated(0) { }
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BumpPtrAllocator::~BumpPtrAllocator() {
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DeallocateSlabs(CurSlab);
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}
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/// AlignPtr - Align Ptr to Alignment bytes, rounding up. Alignment should
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/// be a power of two. This method rounds up, so AlignPtr(7, 4) == 8 and
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/// AlignPtr(8, 4) == 8.
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char *BumpPtrAllocator::AlignPtr(char *Ptr, size_t Alignment) {
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assert(Alignment && (Alignment & (Alignment - 1)) == 0 &&
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"Alignment is not a power of two!");
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// Do the alignment.
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return (char*)(((uintptr_t)Ptr + Alignment - 1) &
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~(uintptr_t)(Alignment - 1));
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}
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/// StartNewSlab - Allocate a new slab and move the bump pointers over into
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/// the new slab. Modifies CurPtr and End.
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void BumpPtrAllocator::StartNewSlab() {
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// If we allocated a big number of slabs already it's likely that we're going
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// to allocate more. Increase slab size to reduce mallocs and possibly memory
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// overhead. The factors are chosen conservatively to avoid overallocation.
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if (BytesAllocated >= SlabSize * 128)
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SlabSize *= 2;
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MemSlab *NewSlab = Allocator.Allocate(SlabSize);
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NewSlab->NextPtr = CurSlab;
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CurSlab = NewSlab;
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CurPtr = (char*)(CurSlab + 1);
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End = ((char*)CurSlab) + CurSlab->Size;
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}
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/// DeallocateSlabs - Deallocate all memory slabs after and including this
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/// one.
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void BumpPtrAllocator::DeallocateSlabs(MemSlab *Slab) {
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while (Slab) {
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MemSlab *NextSlab = Slab->NextPtr;
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#ifndef NDEBUG
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// Poison the memory so stale pointers crash sooner. Note we must
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// preserve the Size and NextPtr fields at the beginning.
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sys::Memory::setRangeWritable(Slab + 1, Slab->Size - sizeof(MemSlab));
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memset(Slab + 1, 0xCD, Slab->Size - sizeof(MemSlab));
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#endif
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Allocator.Deallocate(Slab);
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Slab = NextSlab;
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}
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}
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/// Reset - Deallocate all but the current slab and reset the current pointer
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/// to the beginning of it, freeing all memory allocated so far.
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void BumpPtrAllocator::Reset() {
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if (!CurSlab)
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return;
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DeallocateSlabs(CurSlab->NextPtr);
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CurSlab->NextPtr = 0;
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CurPtr = (char*)(CurSlab + 1);
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End = ((char*)CurSlab) + CurSlab->Size;
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}
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/// Allocate - Allocate space at the specified alignment.
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///
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void *BumpPtrAllocator::Allocate(size_t Size, size_t Alignment) {
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if (!CurSlab) // Start a new slab if we haven't allocated one already.
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StartNewSlab();
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// Keep track of how many bytes we've allocated.
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BytesAllocated += Size;
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// 0-byte alignment means 1-byte alignment.
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if (Alignment == 0) Alignment = 1;
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// Allocate the aligned space, going forwards from CurPtr.
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char *Ptr = AlignPtr(CurPtr, Alignment);
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// Check if we can hold it.
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if (Ptr + Size <= End) {
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CurPtr = Ptr + Size;
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return Ptr;
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}
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// If Size is really big, allocate a separate slab for it.
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size_t PaddedSize = Size + sizeof(MemSlab) + Alignment - 1;
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if (PaddedSize > SizeThreshold) {
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MemSlab *NewSlab = Allocator.Allocate(PaddedSize);
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// Put the new slab after the current slab, since we are not allocating
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// into it.
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NewSlab->NextPtr = CurSlab->NextPtr;
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CurSlab->NextPtr = NewSlab;
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Ptr = AlignPtr((char*)(NewSlab + 1), Alignment);
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assert((uintptr_t)Ptr + Size <= (uintptr_t)NewSlab + NewSlab->Size);
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return Ptr;
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}
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// Otherwise, start a new slab and try again.
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StartNewSlab();
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Ptr = AlignPtr(CurPtr, Alignment);
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CurPtr = Ptr + Size;
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assert(CurPtr <= End && "Unable to allocate memory!");
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return Ptr;
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}
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unsigned BumpPtrAllocator::GetNumSlabs() const {
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unsigned NumSlabs = 0;
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for (MemSlab *Slab = CurSlab; Slab != 0; Slab = Slab->NextPtr) {
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++NumSlabs;
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}
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return NumSlabs;
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}
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size_t BumpPtrAllocator::getTotalMemory() const {
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size_t TotalMemory = 0;
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for (MemSlab *Slab = CurSlab; Slab != 0; Slab = Slab->NextPtr) {
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TotalMemory += Slab->Size;
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}
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return TotalMemory;
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}
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void BumpPtrAllocator::PrintStats() const {
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unsigned NumSlabs = 0;
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size_t TotalMemory = 0;
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for (MemSlab *Slab = CurSlab; Slab != 0; Slab = Slab->NextPtr) {
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TotalMemory += Slab->Size;
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++NumSlabs;
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}
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errs() << "\nNumber of memory regions: " << NumSlabs << '\n'
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<< "Bytes used: " << BytesAllocated << '\n'
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<< "Bytes allocated: " << TotalMemory << '\n'
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<< "Bytes wasted: " << (TotalMemory - BytesAllocated)
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<< " (includes alignment, etc)\n";
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}
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MallocSlabAllocator BumpPtrAllocator::DefaultSlabAllocator =
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MallocSlabAllocator();
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SlabAllocator::~SlabAllocator() { }
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MallocSlabAllocator::~MallocSlabAllocator() { }
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MemSlab *MallocSlabAllocator::Allocate(size_t Size) {
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MemSlab *Slab = (MemSlab*)Allocator.Allocate(Size, 0);
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Slab->Size = Size;
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Slab->NextPtr = 0;
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return Slab;
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}
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void MallocSlabAllocator::Deallocate(MemSlab *Slab) {
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Allocator.Deallocate(Slab);
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}
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void PrintRecyclerStats(size_t Size,
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size_t Align,
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size_t FreeListSize) {
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errs() << "Recycler element size: " << Size << '\n'
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<< "Recycler element alignment: " << Align << '\n'
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<< "Number of elements free for recycling: " << FreeListSize << '\n';
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}
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}
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