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/*
* Copyright (C) 2012 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 Watchpoint_h
#define Watchpoint_h
#include <wtf/RefCounted.h>
#include <wtf/SentinelLinkedList.h>
namespace JSC {
class Watchpoint : public BasicRawSentinelNode<Watchpoint> {
public:
Watchpoint()
{
}
virtual ~Watchpoint();
void fire() { fireInternal(); }
protected:
virtual void fireInternal() = 0;
};
enum InitialWatchpointSetMode { InitializedWatching, InitializedBlind };
class InlineWatchpointSet;
class WatchpointSet : public RefCounted<WatchpointSet> {
public:
WatchpointSet(InitialWatchpointSetMode);
~WatchpointSet();
bool isStillValid() const { return !m_isInvalidated; }
bool hasBeenInvalidated() const { return m_isInvalidated; }
// As a convenience, this will ignore 0. That's because code paths in the DFG
// that create speculation watchpoints may choose to bail out if speculation
// had already been terminated.
void add(Watchpoint*);
// Force the watchpoint set to behave as if it was being watched even if no
// watchpoints have been installed. This will result in invalidation if the
// watchpoint would have fired. That's a pretty good indication that you
// probably don't want to set watchpoints, since we typically don't want to
// set watchpoints that we believe will actually be fired.
void startWatching() { m_isWatched = true; }
void notifyWrite()
{
if (!m_isWatched)
return;
notifyWriteSlow();
}
bool* addressOfIsWatched() { return &m_isWatched; }
void notifyWriteSlow(); // Call only if you've checked isWatched.
private:
void fireAllWatchpoints();
friend class InlineWatchpointSet;
SentinelLinkedList<Watchpoint, BasicRawSentinelNode<Watchpoint> > m_set;
bool m_isWatched;
bool m_isInvalidated;
};
// InlineWatchpointSet is a low-overhead, non-copyable watchpoint set in which
// it is not possible to quickly query whether it is being watched in a single
// branch. There is a fairly simple tradeoff between WatchpointSet and
// InlineWatchpointSet:
//
// Do you have to emit JIT code that rapidly tests whether the watchpoint set
// is being watched? If so, use WatchpointSet.
//
// Do you need multiple parties to have pointers to the same WatchpointSet?
// If so, use WatchpointSet.
//
// Do you have to allocate a lot of watchpoint sets? If so, use
// InlineWatchpointSet unless you answered "yes" to the previous questions.
//
// InlineWatchpointSet will use just one pointer-width word of memory unless
// you actually add watchpoints to it, in which case it internally inflates
// to a pointer to a WatchpointSet, and transfers its state to the
// WatchpointSet.
class InlineWatchpointSet {
WTF_MAKE_NONCOPYABLE(InlineWatchpointSet);
public:
InlineWatchpointSet(InitialWatchpointSetMode mode)
: m_data((mode == InitializedWatching ? IsWatchedFlag : 0) | IsThinFlag)
{
}
~InlineWatchpointSet()
{
if (isThin())
return;
freeFat();
}
bool hasBeenInvalidated() const
{
if (isFat())
return fat()->hasBeenInvalidated();
return m_data & IsInvalidatedFlag;
}
bool isStillValid() const
{
return !hasBeenInvalidated();
}
void add(Watchpoint*);
void startWatching()
{
if (isFat()) {
fat()->startWatching();
return;
}
m_data |= IsWatchedFlag;
}
void notifyWrite()
{
if (isFat()) {
fat()->notifyWrite();
return;
}
if (!(m_data & IsWatchedFlag))
return;
m_data |= IsInvalidatedFlag;
}
private:
static const uintptr_t IsThinFlag = 1;
static const uintptr_t IsInvalidatedFlag = 2;
static const uintptr_t IsWatchedFlag = 4;
bool isThin() const { return m_data & IsThinFlag; }
bool isFat() const { return !isThin(); };
WatchpointSet* fat()
{
ASSERT(isFat());
return bitwise_cast<WatchpointSet*>(m_data);
}
const WatchpointSet* fat() const
{
ASSERT(isFat());
return bitwise_cast<WatchpointSet*>(m_data);
}
WatchpointSet* inflate()
{
if (LIKELY(isFat()))
return fat();
return inflateSlow();
}
JS_EXPORT_PRIVATE WatchpointSet* inflateSlow();
JS_EXPORT_PRIVATE void freeFat();
uintptr_t m_data;
};
} // namespace JSC
#endif // Watchpoint_h
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