JavaScriptCore-1097.3.tar.gz

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

diff --git a/dfg/DFGCFAPhase.cpp b/dfg/DFGCFAPhase.cpp
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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. 
+ */
+
+#include "config.h"
+#include "DFGCFAPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGAbstractState.h"
+#include "DFGGraph.h"
+#include "DFGPhase.h"
+
+namespace JSC { namespace DFG {
+
+class CFAPhase : public Phase {
+public:
+    CFAPhase(Graph& graph)
+        : Phase(graph, "control flow analysis")
+        , m_state(graph)
+    {
+    }
+    
+    void run()
+    {
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        m_count = 0;
+#endif
+        
+        // This implements a pseudo-worklist-based forward CFA, except that the visit order
+        // of blocks is the bytecode program order (which is nearly topological), and
+        // instead of a worklist we just walk all basic blocks checking if cfaShouldRevisit
+        // is set to true. This is likely to balance the efficiency properties of both
+        // worklist-based and forward fixpoint-based approaches. Like a worklist-based
+        // approach, it won't visit code if it's meaningless to do so (nothing changed at
+        // the head of the block or the predecessors have not been visited). Like a forward
+        // fixpoint-based approach, it has a high probability of only visiting a block
+        // after all predecessors have been visited. Only loops will cause this analysis to
+        // revisit blocks, and the amount of revisiting is proportional to loop depth.
+        
+        AbstractState::initialize(m_graph);
+        
+        do {
+            m_changed = false;
+            performForwardCFA();
+        } while (m_changed);
+    }
+    
+private:
+    void performBlockCFA(BlockIndex blockIndex)
+    {
+        BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+        if (!block->cfaShouldRevisit)
+            return;
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        dataLog("   Block #%u (bc#%u):\n", blockIndex, block->bytecodeBegin);
+#endif
+        m_state.beginBasicBlock(block);
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        dataLog("      head vars: ");
+        dumpOperands(block->valuesAtHead, WTF::dataFile());
+        dataLog("\n");
+#endif
+        for (unsigned i = 0; i < block->size(); ++i) {
+            NodeIndex nodeIndex = block->at(i);
+            if (!m_graph[nodeIndex].shouldGenerate())
+                continue;
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+            dataLog("      %s @%u: ", Graph::opName(m_graph[nodeIndex].op()), nodeIndex);
+            m_state.dump(WTF::dataFile());
+            dataLog("\n");
+#endif
+            if (!m_state.execute(i))
+                break;
+        }
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        dataLog("      tail regs: ");
+        m_state.dump(WTF::dataFile());
+        dataLog("\n");
+#endif
+        m_changed |= m_state.endBasicBlock(AbstractState::MergeToSuccessors);
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        dataLog("      tail vars: ");
+        dumpOperands(block->valuesAtTail, WTF::dataFile());
+        dataLog("\n");
+#endif
+    }
+    
+    void performForwardCFA()
+    {
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+        dataLog("CFA [%u]\n", ++m_count);
+#endif
+        
+        for (BlockIndex block = 0; block < m_graph.m_blocks.size(); ++block)
+            performBlockCFA(block);
+    }
+
+private:
+    AbstractState m_state;
+    
+    bool m_changed;
+#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
+    unsigned m_count;
+#endif
+};
+
+void performCFA(Graph& graph)
+{
+    runPhase<CFAPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)