vegorov@google.com
00bd7303e5
Make tags_ field be valid (i.e. encode size and class id) for free list elements. R=iposva@google.com BUG= TEST= Review URL: https://chromiumcodereview.appspot.com//10538022 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@8437 260f80e4-7a28-3924-810f-c04153c831b5
99 lines
2.6 KiB
C++
99 lines
2.6 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef VM_FREELIST_H_
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#define VM_FREELIST_H_
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#include "platform/assert.h"
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#include "vm/allocation.h"
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#include "vm/raw_object.h"
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namespace dart {
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// FreeListElement describes a freelist element. Smallest FreeListElement is
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// two words in size. Second word of the raw object is used to keep a next_
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// pointer to chain elements of the list together. For objects larger than the
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// object size encodable in tags field, the size of the element is embedded in
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// the element at the address following the next_ field.
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class FreeListElement {
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public:
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FreeListElement* next() const {
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return next_;
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}
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void set_next(FreeListElement* next) {
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next_ = next;
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}
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intptr_t Size() {
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intptr_t size = RawObject::SizeTag::decode(tags_);
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if (size != 0) return size;
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return *SizeAddress();
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}
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static FreeListElement* AsElement(uword addr, intptr_t size);
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static void InitOnce();
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// Used to allocate class for free list elements in Object::InitOnce.
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class FakeInstance {
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public:
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FakeInstance() { }
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static cpp_vtable vtable() { return 0; }
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static intptr_t InstanceSize() { return 0; }
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static const ObjectKind kInstanceKind = kFreeListElement;
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static bool IsInstance() { return true; }
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private:
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DISALLOW_ALLOCATION();
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DISALLOW_COPY_AND_ASSIGN(FakeInstance);
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};
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private:
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// This layout mirrors the layout of RawObject.
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uword tags_;
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FreeListElement* next_;
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// Returns the address of the embedded size.
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intptr_t* SizeAddress() const {
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uword addr = reinterpret_cast<uword>(&next_) + kWordSize;
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return reinterpret_cast<intptr_t*>(addr);
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}
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// FreeListElements cannot be allocated. Instead references to them are
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// created using the AsElement factory method.
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DISALLOW_ALLOCATION();
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DISALLOW_IMPLICIT_CONSTRUCTORS(FreeListElement);
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};
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class FreeList {
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public:
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FreeList();
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~FreeList();
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uword TryAllocate(intptr_t size);
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void Free(uword addr, intptr_t size);
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void Reset();
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private:
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static const int kNumLists = 128;
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static intptr_t IndexForSize(intptr_t size);
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void EnqueueElement(FreeListElement* element, intptr_t index);
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FreeListElement* DequeueElement(intptr_t index);
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void SplitElementAfterAndEnqueue(FreeListElement* element, intptr_t size);
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FreeListElement* free_lists_[kNumLists + 1];
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DISALLOW_COPY_AND_ASSIGN(FreeList);
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};
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} // namespace dart
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#endif // VM_FREELIST_H_
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