JavaScriptCore-7600.1.4.9.tar.gz

[apple/javascriptcore.git] / dfg / DFGCriticalEdgeBreakingPhase.cpp

diff --git a/dfg/DFGCriticalEdgeBreakingPhase.cpp b/dfg/DFGCriticalEdgeBreakingPhase.cpp
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+/*
+ * Copyright (C) 2013 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. 
+ */
+
+#include "config.h"
+#include "DFGCriticalEdgeBreakingPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlockInlines.h"
+#include "DFGBlockInsertionSet.h"
+#include "DFGGraph.h"
+#include "DFGPhase.h"
+#include "JSCInlines.h"
+#include <wtf/HashMap.h>
+
+namespace JSC { namespace DFG {
+
+class CriticalEdgeBreakingPhase : public Phase {
+public:
+    CriticalEdgeBreakingPhase(Graph& graph)
+        : Phase(graph, "critical edge breaking")
+        , m_insertionSet(graph)
+    {
+    }
+    
+    bool run()
+    {
+        for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
+            BasicBlock* block = m_graph.block(blockIndex);
+            if (!block)
+                continue;
+            
+            // An edge A->B is critical if A has multiple successor and B has multiple
+            // predecessors. Thus we fail early if we don't have multiple successors.
+            
+            if (block->numSuccessors() <= 1)
+                continue;
+            
+            for (unsigned i = block->numSuccessors(); i--;) {
+                BasicBlock** successor = &block->successor(i);
+                if ((*successor)->predecessors.size() <= 1)
+                    continue;
+                
+                breakCriticalEdge(block, successor); 
+            }
+        }
+        
+        return m_insertionSet.execute();
+    }
+
+private:
+    void breakCriticalEdge(BasicBlock* predecessor, BasicBlock** successor)
+    {
+        // Note that we pass NaN for the count of the critical edge block, because we honestly
+        // don't know its execution frequency.
+        BasicBlock* pad = m_insertionSet.insertBefore(*successor, PNaN);
+        pad->appendNode(
+            m_graph, SpecNone, Jump, (*successor)->at(0)->origin, OpInfo(*successor));
+        pad->predecessors.append(predecessor);
+        (*successor)->replacePredecessor(predecessor, pad);
+        
+        *successor = pad;
+    }
+    
+    BlockInsertionSet m_insertionSet;
+};
+
+bool performCriticalEdgeBreaking(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG Critical Edge Breaking Phase");
+    return runPhase<CriticalEdgeBreakingPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
+