Source/JavaScriptCore/dfg/DFGSafepoint.cpp

   1 /*
   2  * Copyright (C) 2014, 2016 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. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "DFGSafepoint.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGPlan.h"
  32 #include "DFGScannable.h"
  33 #include "DFGThreadData.h"
  34 #include "JSCInlines.h"
  35
  36 namespace JSC { namespace DFG {
  37
  38 Safepoint::Result::~Result()
  39 {
  40     RELEASE_ASSERT(m_wasChecked);
  41 }
  42
  43 bool Safepoint::Result::didGetCancelled()
  44 {
  45     m_wasChecked = true;
  46     return m_didGetCancelled;
  47 }
  48
  49 Safepoint::Safepoint(Plan& plan, Result& result)
  50     : m_vm(plan.vm)
  51     , m_plan(plan)
  52     , m_didCallBegin(false)
  53     , m_result(result)
  54 {
  55     RELEASE_ASSERT(result.m_wasChecked);
  56     result.m_wasChecked = false;
  57     result.m_didGetCancelled = false;
  58 }
  59
  60 Safepoint::~Safepoint()
  61 {
  62     RELEASE_ASSERT(m_didCallBegin);
  63     if (ThreadData* data = m_plan.threadData) {
  64         RELEASE_ASSERT(data->m_safepoint == this);
  65         data->m_rightToRun.lock();
  66         data->m_safepoint = nullptr;
  67     }
  68 }
  69
  70 void Safepoint::add(Scannable* scannable)
  71 {
  72     RELEASE_ASSERT(!m_didCallBegin);
  73     m_scannables.append(scannable);
  74 }
  75
  76 void Safepoint::begin()
  77 {
  78     RELEASE_ASSERT(!m_didCallBegin);
  79     m_didCallBegin = true;
  80     if (ThreadData* data = m_plan.threadData) {
  81         RELEASE_ASSERT(!data->m_safepoint);
  82         data->m_safepoint = this;
  83         data->m_rightToRun.unlock();
  84     }
  85 }
  86
  87 void Safepoint::checkLivenessAndVisitChildren(SlotVisitor& visitor)
  88 {
  89     RELEASE_ASSERT(m_didCallBegin);
  90
  91     if (m_result.m_didGetCancelled)
  92         return; // We were cancelled during a previous GC!
  93
  94     if (!isKnownToBeLiveDuringGC())
  95         return;
  96
  97     for (unsigned i = m_scannables.size(); i--;)
  98         m_scannables[i]->visitChildren(visitor);
  99 }
 100
 101 bool Safepoint::isKnownToBeLiveDuringGC()
 102 {
 103     RELEASE_ASSERT(m_didCallBegin);
 104
 105     if (m_result.m_didGetCancelled)
 106         return true; // We were cancelled during a previous GC, so let's not mess with it this time around - pretend it's live and move on.
 107
 108     return m_plan.isKnownToBeLiveDuringGC();
 109 }
 110
 111 void Safepoint::cancel()
 112 {
 113     RELEASE_ASSERT(m_didCallBegin);
 114     RELEASE_ASSERT(!m_result.m_didGetCancelled); // We cannot get cancelled twice because subsequent GCs will think that we're alive and they will not do anything to us.
 115
 116     m_plan.cancel();
 117     m_result.m_didGetCancelled = true;
 118     m_vm = nullptr;
 119 }
 120
 121 VM* Safepoint::vm() const
 122 {
 123     return m_vm;
 124 }
 125
 126 } } // namespace JSC::DFG
 127
 128 #endif // ENABLE(DFG_JIT)
 129