src/third_party/WebKit/Source/JavaScriptCore/interpreter/JSStack.cpp

/*
 * Copyright (C) 2008 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *     notice, this list of conditions and the following disclaimer in the
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 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 */

#include "config.h"
#include "JSStack.h"
#include "JSStackInlines.h"

#include "ConservativeRoots.h"
#include "Interpreter.h"

namespace JSC {

static size_t committedBytesCount = 0;

static Mutex& stackStatisticsMutex()
{
    DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());
    return staticMutex;
}    

JSStack::JSStack(JSGlobalData& globalData, size_t capacity)
    : m_end(0)
    , m_topCallFrame(globalData.topCallFrame)
{
#if defined(__LB_SHELL__) || OS(STARBOARD)
    // There is no reason for this to be page aligned.
    ASSERT(capacity);
    // However, commitSize should be page aligned
    ASSERT(isPageAligned(commitSize));
#else
    ASSERT(capacity && isPageAligned(capacity));
#endif
    m_reservation = PageReservation::reserve(roundUpAllocationSize(capacity * sizeof(Register), commitSize), OSAllocator::JSVMStackPages);
    m_end = static_cast<Register*>(m_reservation.base());
    m_commitEnd = static_cast<Register*>(m_reservation.base());

    disableErrorStackReserve();

    m_topCallFrame = 0;
}

JSStack::~JSStack()
{
    void* base = m_reservation.base();
    m_reservation.decommit(base, reinterpret_cast<intptr_t>(m_commitEnd) - reinterpret_cast<intptr_t>(base));
    addToCommittedByteCount(-(reinterpret_cast<intptr_t>(m_commitEnd) - reinterpret_cast<intptr_t>(base)));
    m_reservation.deallocate();
}

bool JSStack::growSlowCase(Register* newEnd)
{
    // If we have already committed enough memory to satisfy this request,
    // just update the end pointer and return.
    if (newEnd <= m_commitEnd) {
        m_end = newEnd;
        return true;
    }

    // Compute the chunk size of additional memory to commit, and see if we
    // have it is still within our budget. If not, we'll fail to grow and
    // return false.
    long delta = roundUpAllocationSize(reinterpret_cast<char*>(newEnd) - reinterpret_cast<char*>(m_commitEnd), commitSize);
    if (reinterpret_cast<char*>(m_commitEnd) + delta > reinterpret_cast<char*>(m_useableEnd))
        return false;

    // Otherwise, the growth is still within our budget. Go ahead and commit
    // it and return true.
    m_reservation.commit(m_commitEnd, delta);
    addToCommittedByteCount(delta);
    m_commitEnd = reinterpret_cast_ptr<Register*>(reinterpret_cast<char*>(m_commitEnd) + delta);
    m_end = newEnd;
    return true;
}

void JSStack::gatherConservativeRoots(ConservativeRoots& conservativeRoots)
{
    conservativeRoots.add(begin(), getTopOfStack());
}

#if ENABLE(JIT)
void JSStack::gatherConservativeRoots(ConservativeRoots& conservativeRoots, JITStubRoutineSet& jitStubRoutines, DFGCodeBlocks& dfgCodeBlocks)
{
    conservativeRoots.add(begin(), getTopOfStack(), jitStubRoutines, dfgCodeBlocks);
}
#endif

void JSStack::releaseExcessCapacity()
{
    ptrdiff_t delta = reinterpret_cast<uintptr_t>(m_commitEnd) - reinterpret_cast<uintptr_t>(m_reservation.base());
    m_reservation.decommit(m_reservation.base(), delta);
    addToCommittedByteCount(-delta);
    m_commitEnd = static_cast<Register*>(m_reservation.base());
}

void JSStack::initializeThreading()
{
    stackStatisticsMutex();
}

size_t JSStack::committedByteCount()
{
    MutexLocker locker(stackStatisticsMutex());
    return committedBytesCount;
}

void JSStack::addToCommittedByteCount(long byteCount)
{
    MutexLocker locker(stackStatisticsMutex());
    ASSERT(static_cast<long>(committedBytesCount) + byteCount > -1);
    committedBytesCount += byteCount;
}

void JSStack::enableErrorStackReserve()
{
    m_useableEnd = reservationEnd();
}

void JSStack::disableErrorStackReserve()
{
    char* useableEnd = reinterpret_cast<char*>(reservationEnd()) - commitSize;
    m_useableEnd = reinterpret_cast<Register*>(useableEnd);

    // By the time we get here, we are guaranteed to be destructing the last
    // Interpreter::ErrorHandlingMode that enabled this reserve in the first
    // place. That means the stack space beyond m_useableEnd before we
    // enabled the reserve was not previously in use. Hence, it is safe to
    // shrink back to that m_useableEnd.
    if (m_end > m_useableEnd) {
        ASSERT(m_topCallFrame->frameExtent() <= m_useableEnd);
        shrink(m_useableEnd);
    }
}

} // namespace JSC