--- /dev/null
+/*
+ * Copyright (C) 2011, 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 DFGVariableAccessData_h
+#define DFGVariableAccessData_h
+
+#include "DFGDoubleFormatState.h"
+#include "DFGNodeFlags.h"
+#include "Operands.h"
+#include "PredictedType.h"
+#include "VirtualRegister.h"
+#include <wtf/Platform.h>
+#include <wtf/UnionFind.h>
+#include <wtf/Vector.h>
+
+namespace JSC { namespace DFG {
+
+class VariableAccessData : public UnionFind<VariableAccessData> {
+public:
+ enum Ballot { VoteValue, VoteDouble };
+
+ VariableAccessData()
+ : m_local(static_cast<VirtualRegister>(std::numeric_limits<int>::min()))
+ , m_prediction(PredictNone)
+ , m_argumentAwarePrediction(PredictNone)
+ , m_flags(0)
+ , m_doubleFormatState(EmptyDoubleFormatState)
+ {
+ clearVotes();
+ }
+
+ VariableAccessData(VirtualRegister local)
+ : m_local(local)
+ , m_prediction(PredictNone)
+ , m_argumentAwarePrediction(PredictNone)
+ , m_flags(0)
+ , m_doubleFormatState(EmptyDoubleFormatState)
+ {
+ clearVotes();
+ }
+
+ VirtualRegister local()
+ {
+ ASSERT(m_local == find()->m_local);
+ return m_local;
+ }
+
+ int operand()
+ {
+ return static_cast<int>(local());
+ }
+
+ bool predict(PredictedType prediction)
+ {
+ VariableAccessData* self = find();
+ bool result = mergePrediction(self->m_prediction, prediction);
+ if (result)
+ mergePrediction(m_argumentAwarePrediction, m_prediction);
+ return result;
+ }
+
+ PredictedType nonUnifiedPrediction()
+ {
+ return m_prediction;
+ }
+
+ PredictedType prediction()
+ {
+ return find()->m_prediction;
+ }
+
+ PredictedType argumentAwarePrediction()
+ {
+ return find()->m_argumentAwarePrediction;
+ }
+
+ bool mergeArgumentAwarePrediction(PredictedType prediction)
+ {
+ return mergePrediction(find()->m_argumentAwarePrediction, prediction);
+ }
+
+ void clearVotes()
+ {
+ ASSERT(find() == this);
+ m_votes[VoteValue] = 0;
+ m_votes[VoteDouble] = 0;
+ }
+
+ void vote(Ballot ballot)
+ {
+ ASSERT(static_cast<unsigned>(ballot) < 2);
+ m_votes[ballot]++;
+ }
+
+ double doubleVoteRatio()
+ {
+ ASSERT(find() == this);
+ return static_cast<double>(m_votes[VoteDouble]) / m_votes[VoteValue];
+ }
+
+ bool shouldUseDoubleFormatAccordingToVote()
+ {
+ // We don't support this facility for arguments, yet.
+ // FIXME: make this work for arguments.
+ if (operandIsArgument(operand()))
+ return false;
+
+ // If the variable is not a number prediction, then this doesn't
+ // make any sense.
+ if (!isNumberPrediction(prediction()))
+ return false;
+
+ // If the variable is predicted to hold only doubles, then it's a
+ // no-brainer: it should be formatted as a double.
+ if (isDoublePrediction(prediction()))
+ return true;
+
+ // If the variable is known to be used as an integer, then be safe -
+ // don't force it to be a double.
+ if (flags() & NodeUsedAsInt)
+ return false;
+
+ // If the variable has been voted to become a double, then make it a
+ // double.
+ if (doubleVoteRatio() >= Options::doubleVoteRatioForDoubleFormat)
+ return true;
+
+ return false;
+ }
+
+ DoubleFormatState doubleFormatState()
+ {
+ return find()->m_doubleFormatState;
+ }
+
+ bool shouldUseDoubleFormat()
+ {
+ ASSERT(isRoot());
+ return m_doubleFormatState == UsingDoubleFormat;
+ }
+
+ bool tallyVotesForShouldUseDoubleFormat()
+ {
+ ASSERT(isRoot());
+
+ if (m_doubleFormatState == CantUseDoubleFormat)
+ return false;
+
+ bool newValueOfShouldUseDoubleFormat = shouldUseDoubleFormatAccordingToVote();
+ if (!newValueOfShouldUseDoubleFormat) {
+ // We monotonically convert to double. Hence, if the fixpoint leads us to conclude that we should
+ // switch back to int, we instead ignore this and stick with double.
+ return false;
+ }
+
+ if (m_doubleFormatState == UsingDoubleFormat)
+ return false;
+
+ return DFG::mergeDoubleFormatState(m_doubleFormatState, UsingDoubleFormat);
+ }
+
+ bool mergeDoubleFormatState(DoubleFormatState doubleFormatState)
+ {
+ return DFG::mergeDoubleFormatState(find()->m_doubleFormatState, doubleFormatState);
+ }
+
+ bool makePredictionForDoubleFormat()
+ {
+ ASSERT(isRoot());
+
+ if (m_doubleFormatState != UsingDoubleFormat)
+ return false;
+
+ return mergePrediction(m_prediction, PredictDouble);
+ }
+
+ NodeFlags flags() const { return m_flags; }
+
+ bool mergeFlags(NodeFlags newFlags)
+ {
+ newFlags |= m_flags;
+ if (newFlags == m_flags)
+ return false;
+ m_flags = newFlags;
+ return true;
+ }
+
+private:
+ // This is slightly space-inefficient, since anything we're unified with
+ // will have the same operand and should have the same prediction. But
+ // putting them here simplifies the code, and we don't expect DFG space
+ // usage for variable access nodes do be significant.
+
+ VirtualRegister m_local;
+ PredictedType m_prediction;
+ PredictedType m_argumentAwarePrediction;
+ NodeFlags m_flags;
+
+ float m_votes[2];
+ DoubleFormatState m_doubleFormatState;
+};
+
+} } // namespace JSC::DFG
+
+#endif // DFGVariableAccessData_h
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