JavaScriptCore-7600.1.4.9.tar.gz

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

diff --git a/dfg/DFGLoopPreHeaderCreationPhase.cpp b/dfg/DFGLoopPreHeaderCreationPhase.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 "DFGLoopPreHeaderCreationPhase.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 {
+
+BasicBlock* createPreHeader(Graph& graph, BlockInsertionSet& insertionSet, BasicBlock* block)
+{
+    // Don't bother to preserve execution frequencies for now.
+    BasicBlock* preHeader = insertionSet.insertBefore(block, PNaN);
+    preHeader->appendNode(
+        graph, SpecNone, Jump, block->at(0)->origin, OpInfo(block));
+    
+    for (unsigned predecessorIndex = 0; predecessorIndex < block->predecessors.size(); predecessorIndex++) {
+        BasicBlock* predecessor = block->predecessors[predecessorIndex];
+        if (graph.m_dominators.dominates(block, predecessor))
+            continue;
+        block->predecessors[predecessorIndex--] = block->predecessors.last();
+        block->predecessors.removeLast();
+        for (unsigned successorIndex = predecessor->numSuccessors(); successorIndex--;) {
+            BasicBlock*& successor = predecessor->successor(successorIndex);
+            if (successor != block)
+                continue;
+            successor = preHeader;
+            preHeader->predecessors.append(predecessor);
+        }
+    }
+    
+    block->predecessors.append(preHeader);
+    return preHeader;
+}
+
+class LoopPreHeaderCreationPhase : public Phase {
+public:
+    LoopPreHeaderCreationPhase(Graph& graph)
+        : Phase(graph, "loop pre-header creation")
+        , m_insertionSet(graph)
+    {
+    }
+    
+    bool run()
+    {
+        m_graph.m_dominators.computeIfNecessary(m_graph);
+        m_graph.m_naturalLoops.computeIfNecessary(m_graph);
+        
+        for (unsigned loopIndex = m_graph.m_naturalLoops.numLoops(); loopIndex--;) {
+            const NaturalLoop& loop = m_graph.m_naturalLoops.loop(loopIndex);
+            BasicBlock* existingPreHeader = 0;
+            bool needsNewPreHeader = false;
+            for (unsigned predecessorIndex = loop.header()->predecessors.size(); predecessorIndex--;) {
+                BasicBlock* predecessor = loop.header()->predecessors[predecessorIndex];
+                if (m_graph.m_dominators.dominates(loop.header(), predecessor))
+                    continue;
+                if (!existingPreHeader) {
+                    existingPreHeader = predecessor;
+                    continue;
+                }
+                if (existingPreHeader == predecessor)
+                    continue;
+                needsNewPreHeader = true;
+                break;
+            }
+            if (!needsNewPreHeader)
+                continue;
+            
+            createPreHeader(m_graph, m_insertionSet, loop.header());
+        }
+        
+        return m_insertionSet.execute();
+    }
+
+    BlockInsertionSet m_insertionSet;
+};
+
+bool performLoopPreHeaderCreation(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG Loop Pre-Header Creation Phase");
+    return runPhase<LoopPreHeaderCreationPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
+