heap/WeakBlock.cpp

   1 /*
   2  * Copyright (C) 2012 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "WeakBlock.h"
  28
  29 #include "Heap.h"
  30 #include "HeapRootVisitor.h"
  31 #include "JSObject.h"
  32 #include "JSCInlines.h"
  33 #include "Structure.h"
  34
  35 namespace JSC {
  36
  37 WeakBlock* WeakBlock::create(MarkedBlock& markedBlock)
  38 {
  39     return new (NotNull, fastMalloc(blockSize)) WeakBlock(markedBlock);
  40 }
  41
  42 void WeakBlock::destroy(WeakBlock* block)
  43 {
  44     block->~WeakBlock();
  45     fastFree(block);
  46 }
  47
  48 WeakBlock::WeakBlock(MarkedBlock& markedBlock)
  49     : DoublyLinkedListNode<WeakBlock>()
  50     , m_markedBlock(&markedBlock)
  51 {
  52     for (size_t i = 0; i < weakImplCount(); ++i) {
  53         WeakImpl* weakImpl = &weakImpls()[i];
  54         new (NotNull, weakImpl) WeakImpl;
  55         addToFreeList(&m_sweepResult.freeList, weakImpl);
  56     }
  57
  58     ASSERT(isEmpty());
  59 }
  60
  61 void WeakBlock::lastChanceToFinalize()
  62 {
  63     for (size_t i = 0; i < weakImplCount(); ++i) {
  64         WeakImpl* weakImpl = &weakImpls()[i];
  65         if (weakImpl->state() >= WeakImpl::Finalized)
  66             continue;
  67         weakImpl->setState(WeakImpl::Dead);
  68         finalize(weakImpl);
  69     }
  70 }
  71
  72 void WeakBlock::sweep()
  73 {
  74     // If a block is completely empty, a sweep won't have any effect.
  75     if (isEmpty())
  76         return;
  77
  78     SweepResult sweepResult;
  79     for (size_t i = 0; i < weakImplCount(); ++i) {
  80         WeakImpl* weakImpl = &weakImpls()[i];
  81         if (weakImpl->state() == WeakImpl::Dead)
  82             finalize(weakImpl);
  83         if (weakImpl->state() == WeakImpl::Deallocated)
  84             addToFreeList(&sweepResult.freeList, weakImpl);
  85         else {
  86             sweepResult.blockIsFree = false;
  87             if (weakImpl->state() == WeakImpl::Live)
  88                 sweepResult.blockIsLogicallyEmpty = false;
  89         }
  90     }
  91
  92     m_sweepResult = sweepResult;
  93     ASSERT(!m_sweepResult.isNull());
  94 }
  95
  96 void WeakBlock::visit(HeapRootVisitor& heapRootVisitor)
  97 {
  98     // If a block is completely empty, a visit won't have any effect.
  99     if (isEmpty())
 100         return;
 101
 102     // If this WeakBlock doesn't belong to a MarkedBlock, we won't even be here.
 103     ASSERT(m_markedBlock);
 104
 105     if (m_markedBlock->isAllocated())
 106         return;
 107
 108     SlotVisitor& visitor = heapRootVisitor.visitor();
 109
 110     for (size_t i = 0; i < weakImplCount(); ++i) {
 111         WeakImpl* weakImpl = &weakImpls()[i];
 112         if (weakImpl->state() != WeakImpl::Live)
 113             continue;
 114
 115         const JSValue& jsValue = weakImpl->jsValue();
 116         if (m_markedBlock->isMarkedOrNewlyAllocated(jsValue.asCell()))
 117             continue;
 118
 119         WeakHandleOwner* weakHandleOwner = weakImpl->weakHandleOwner();
 120         if (!weakHandleOwner)
 121             continue;
 122
 123         if (!weakHandleOwner->isReachableFromOpaqueRoots(Handle<Unknown>::wrapSlot(&const_cast<JSValue&>(jsValue)), weakImpl->context(), visitor))
 124             continue;
 125
 126         heapRootVisitor.visit(&const_cast<JSValue&>(jsValue));
 127     }
 128 }
 129
 130 void WeakBlock::reap()
 131 {
 132     // If a block is completely empty, a reaping won't have any effect.
 133     if (isEmpty())
 134         return;
 135
 136     // If this WeakBlock doesn't belong to a MarkedBlock, we won't even be here.
 137     ASSERT(m_markedBlock);
 138
 139     if (m_markedBlock->isAllocated())
 140         return;
 141
 142     for (size_t i = 0; i < weakImplCount(); ++i) {
 143         WeakImpl* weakImpl = &weakImpls()[i];
 144         if (weakImpl->state() > WeakImpl::Dead)
 145             continue;
 146
 147         if (m_markedBlock->isMarkedOrNewlyAllocated(weakImpl->jsValue().asCell())) {
 148             ASSERT(weakImpl->state() == WeakImpl::Live);
 149             continue;
 150         }
 151
 152         weakImpl->setState(WeakImpl::Dead);
 153     }
 154 }
 155
 156 } // namespace JSC