dfg/DFGSafepoint.cpp

   1 /*
   2  * Copyright (C) 2014 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_plan(plan)
  51     , m_didCallBegin(false)
  52     , m_result(result)
  53 {
  54     RELEASE_ASSERT(result.m_wasChecked);
  55     result.m_wasChecked = false;
  56     result.m_didGetCancelled = false;
  57 }
  58
  59 Safepoint::~Safepoint()
  60 {
  61     RELEASE_ASSERT(m_didCallBegin);
  62     if (ThreadData* data = m_plan.threadData) {
  63         RELEASE_ASSERT(data->m_safepoint == this);
  64         data->m_rightToRun.lock();
  65         data->m_safepoint = nullptr;
  66     }
  67 }
  68
  69 void Safepoint::add(Scannable* scannable)
  70 {
  71     RELEASE_ASSERT(!m_didCallBegin);
  72     m_scannables.append(scannable);
  73 }
  74
  75 void Safepoint::begin()
  76 {
  77     RELEASE_ASSERT(!m_didCallBegin);
  78     m_didCallBegin = true;
  79     if (ThreadData* data = m_plan.threadData) {
  80         RELEASE_ASSERT(!data->m_safepoint);
  81         data->m_safepoint = this;
  82         data->m_rightToRun.unlock();
  83     }
  84 }
  85
  86 void Safepoint::checkLivenessAndVisitChildren(SlotVisitor& visitor)
  87 {
  88     RELEASE_ASSERT(m_didCallBegin);
  89
  90     if (m_result.m_didGetCancelled)
  91         return; // We were cancelled during a previous GC!
  92
  93     if (!isKnownToBeLiveDuringGC())
  94         return;
  95
  96     for (unsigned i = m_scannables.size(); i--;)
  97         m_scannables[i]->visitChildren(visitor);
  98 }
  99
 100 bool Safepoint::isKnownToBeLiveDuringGC()
 101 {
 102     RELEASE_ASSERT(m_didCallBegin);
 103
 104     if (m_result.m_didGetCancelled)
 105         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.
 106
 107     return m_plan.isKnownToBeLiveDuringGC();
 108 }
 109
 110 void Safepoint::cancel()
 111 {
 112     RELEASE_ASSERT(m_didCallBegin);
 113     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.
 114
 115     m_plan.cancel();
 116     m_result.m_didGetCancelled = true;
 117 }
 118
 119 VM& Safepoint::vm() const
 120 {
 121     return m_plan.vm;
 122 }
 123
 124 } } // namespace JSC::DFG
 125
 126 #endif // ENABLE(DFG_JIT)
 127