Source/JavaScriptCore/heap/CodeBlockSet.h

/*
 * Copyright (C) 2013, 2014 Apple Inc. All rights reserved.
 *
 * 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.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef CodeBlockSet_h
#define CodeBlockSet_h

#include "GCSegmentedArray.h"
#include "HeapOperation.h"
#include <wtf/HashSet.h>
#include <wtf/Noncopyable.h>
#include <wtf/PassRefPtr.h>
#include <wtf/PrintStream.h>
#include <wtf/RefPtr.h>

namespace JSC {

class CodeBlock;
class Heap;
class JSCell;
class SlotVisitor;

// CodeBlockSet tracks all CodeBlocks. Every CodeBlock starts out with one
// reference coming in from GC. The GC is responsible for freeing CodeBlocks
// once they hasOneRef() and nobody is running code from that CodeBlock.

class CodeBlockSet {
    WTF_MAKE_NONCOPYABLE(CodeBlockSet);

public:
    CodeBlockSet();
    ~CodeBlockSet();
    
    // Add a CodeBlock. This is only called by CodeBlock constructors.
    void add(PassRefPtr<CodeBlock>);
    
    // Clear mark bits for certain CodeBlocks depending on the type of collection.
    void clearMarksForEdenCollection(const Vector<const JSCell*>&);

    // Clear all mark bits for all CodeBlocks.
    void clearMarksForFullCollection();

    // Mark a pointer that may be a CodeBlock that belongs to the set of DFG
    // blocks. This is defined in CodeBlock.h.
    void mark(CodeBlock* candidateCodeBlock);
    void mark(void* candidateCodeBlock);
    
    // Delete all code blocks that are only referenced by this set (i.e. owned
    // by this set), and that have not been marked.
    void deleteUnmarkedAndUnreferenced(HeapOperation);
    
    void remove(CodeBlock*);
    
    // Trace all marked code blocks. The CodeBlock is free to make use of
    // mayBeExecuting.
    void traceMarked(SlotVisitor&);

    // Add all currently executing CodeBlocks to the remembered set to be 
    // re-scanned during the next collection.
    void rememberCurrentlyExecutingCodeBlocks(Heap*);

    // Visits each CodeBlock in the heap until the visitor function returns true
    // to indicate that it is done iterating, or until every CodeBlock has been
    // visited.
    template<typename Functor> void iterate(Functor& functor)
    {
        for (auto& codeBlock : m_oldCodeBlocks) {
            bool done = functor(codeBlock);
            if (done)
                return;
        }

        for (auto& codeBlock : m_newCodeBlocks) {
            bool done = functor(codeBlock);
            if (done)
                return;
        }
    }
    
    void dump(PrintStream&) const;

private:
    void clearMarksForCodeBlocksInRememberedExecutables(const Vector<const JSCell*>&);
    void promoteYoungCodeBlocks();

    // This is not a set of RefPtr<CodeBlock> because we need to be able to find
    // arbitrary bogus pointers. I could have written a thingy that had peek types
    // and all, but that seemed like overkill.
    HashSet<CodeBlock*> m_oldCodeBlocks;
    HashSet<CodeBlock*> m_newCodeBlocks;
    Vector<CodeBlock*> m_currentlyExecuting;
};

} // namespace JSC

#endif // CodeBlockSet_h