JavaScriptCore-1097.3.tar.gz

[apple/javascriptcore.git] / dfg / DFGAliasTracker.h

diff --git a/dfg/DFGAliasTracker.h b/dfg/DFGAliasTracker.h
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-/*
- * Copyright (C) 2011 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 DFGAliasTracker_h
-#define DFGAliasTracker_h
-
-#if ENABLE(DFG_JIT)
-
-#include <dfg/DFGGraph.h>
-#include <wtf/Vector.h>
-
-namespace JSC { namespace DFG {
-
-// === AliasTracker ===
-//
-// This class id used to detect aliasing property accesses, which we may
-// be able to speculatively optimize (for example removing redundant loads
-// where we know a getter will not be called, or optimizing puts to arrays
-// where we know the value being written to in within length and is not a
-// hole value). In time, this should be more than a 1-deep buffer!
-class AliasTracker {
-public:
-    AliasTracker(Graph& graph)
-        : m_graph(graph)
-        , m_candidateAliasGetByVal(NoNode)
-    {
-    }
-
-    NodeIndex lookupGetByVal(NodeIndex base, NodeIndex property)
-    {
-        // Try to detect situations where a GetByVal follows another GetByVal to the same
-        // property; in these cases, we may be able to omit the subsequent get on the
-        // speculative path, where we know conditions hold to make this safe (for example,
-        // on the speculative path we will not have allowed getter access).
-        if (m_candidateAliasGetByVal != NoNode) {
-            Node& possibleAlias = m_graph[m_candidateAliasGetByVal];
-            ASSERT(possibleAlias.op == GetByVal);
-            // This check ensures the accesses alias, provided that the subscript is an
-            // integer index (this is good enough; the speculative path will only generate
-            // optimized accesses to handle integer subscripts).
-            if (possibleAlias.child1 == base && equalIgnoringLaterNumericConversion(possibleAlias.child2, property))
-                return m_candidateAliasGetByVal;
-        }
-        return NoNode;
-    }
-
-    void recordGetByVal(NodeIndex getByVal)
-    {
-        m_candidateAliasGetByVal = getByVal;
-    }
-
-    void recordPutByVal(NodeIndex putByVal)
-    {
-        ASSERT_UNUSED(putByVal, m_graph[putByVal].op == PutByVal || m_graph[putByVal].op == PutByValAlias);
-        m_candidateAliasGetByVal = NoNode;
-    }
-
-    void recordGetById(NodeIndex getById)
-    {
-        ASSERT_UNUSED(getById, m_graph[getById].op == GetById);
-        m_candidateAliasGetByVal = NoNode;
-    }
-
-    void recordPutById(NodeIndex putById)
-    {
-        ASSERT_UNUSED(putById, m_graph[putById].op == PutById);
-        m_candidateAliasGetByVal = NoNode;
-    }
-
-    void recordPutByIdDirect(NodeIndex putByVal)
-    {
-        ASSERT_UNUSED(putByVal, m_graph[putByVal].op == PutByIdDirect);
-        m_candidateAliasGetByVal = NoNode;
-    }
-
-private:
-    // This method returns true for arguments:
-    //   - (X, X)
-    //   - (X, ValueToNumber(X))
-    //   - (X, ValueToInt32(X))
-    //   - (X, NumberToInt32(X))
-    bool equalIgnoringLaterNumericConversion(NodeIndex op1, NodeIndex op2)
-    {
-        if (op1 == op2)
-            return true;
-        Node& node2 = m_graph[op2];
-        return (node2.op == ValueToNumber || node2.op == ValueToInt32 || node2.op == NumberToInt32) && op1 == node2.child1;
-    }
-
-    // The graph, to look up potentially aliasing nodes.
-    Graph& m_graph;
-    // Currently a 1-deep buffer!
-    NodeIndex m_candidateAliasGetByVal;
-};
-
-} } // namespace JSC::DFG
-
-#endif
-#endif