JavaScriptCore-7600.1.4.9.tar.gz

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

diff --git a/dfg/DFGStaticExecutionCountEstimationPhase.cpp b/dfg/DFGStaticExecutionCountEstimationPhase.cpp
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+/*
+ * Copyright (C) 2014 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 "DFGStaticExecutionCountEstimationPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlockInlines.h"
+#include "DFGGraph.h"
+#include "DFGPhase.h"
+#include "JSCInlines.h"
+
+namespace JSC { namespace DFG {
+
+class StaticExecutionCountEstimationPhase : public Phase {
+public:
+    StaticExecutionCountEstimationPhase(Graph& graph)
+        : Phase(graph, "static execution count estimation")
+    {
+    }
+    
+    bool run()
+    {
+        m_graph.m_naturalLoops.computeIfNecessary(m_graph);
+        
+        // Estimate basic block execution counts based on loop depth.
+        for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
+            BasicBlock* block = m_graph.block(blockIndex);
+            if (!block)
+                continue;
+
+            block->executionCount = pow(10, m_graph.m_naturalLoops.loopDepth(block));
+        }
+        
+        // Estimate branch weights based on execution counts. This isn't quite correct. It'll
+        // assume that each block's conditional successor only has that block as its
+        // predecessor.
+        for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
+            BasicBlock* block = m_graph.block(blockIndex);
+            if (!block)
+                continue;
+            
+            switch (block->last()->op()) {
+            case Branch: {
+                BranchData* data = block->last()->branchData();
+                applyCounts(data->taken);
+                applyCounts(data->notTaken);
+                break;
+            }
+                
+            case Switch: {
+                SwitchData* data = block->last()->switchData();
+                for (unsigned i = data->cases.size(); i--;)
+                    applyCounts(data->cases[i].target);
+                applyCounts(data->fallThrough);
+                break;
+            }
+                
+            default:
+                break;
+            }
+        }
+        
+        return true;
+    }
+
+private:
+    void applyCounts(BranchTarget& target)
+    {
+        target.count = target.block->executionCount;
+    }
+};
+
+bool performStaticExecutionCountEstimation(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG Static Execution Count Estimation");
+    return runPhase<StaticExecutionCountEstimationPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
+