JavaScriptCore-1218.tar.gz

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

diff --git a/dfg/DFGDominators.cpp b/dfg/DFGDominators.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 "DFGDominators.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGGraph.h"
+
+namespace JSC { namespace DFG {
+
+Dominators::Dominators()
+    : m_valid(false)
+{
+}
+
+Dominators::~Dominators()
+{
+}
+
+void Dominators::compute(Graph& graph)
+{
+    // This implements a naive dominator solver.
+    
+    ASSERT(graph.m_blocks[0]->m_predecessors.isEmpty());
+    
+    unsigned numBlocks = graph.m_blocks.size();
+    
+    if (numBlocks > m_results.size()) {
+        m_results.grow(numBlocks);
+        for (unsigned i = numBlocks; i--;)
+            m_results[i].resize(numBlocks);
+        m_scratch.resize(numBlocks);
+    }
+    
+    m_results[0].clearAll();
+    m_results[0].set(0);
+    
+    m_scratch.clearAll();
+    for (unsigned i = numBlocks; i--;) {
+        if (!graph.m_blocks[i])
+            continue;
+        m_scratch.set(i);
+    }
+    
+    for (unsigned i = numBlocks; i-- > 1;) {
+        if (!graph.m_blocks[i] || graph.m_blocks[i]->m_predecessors.isEmpty())
+            m_results[i].clearAll();
+        else
+            m_results[i].set(m_scratch);
+    }
+    
+    bool changed;
+    do {
+        changed = false;
+        for (unsigned i = 1; i < numBlocks; ++i)
+            changed |= iterateForBlock(graph, i);
+        if (!changed)
+            break;
+        
+        changed = false;
+        for (unsigned i = numBlocks; i-- > 1;)
+            changed |= iterateForBlock(graph, i);
+    } while (changed);
+    
+    m_valid = true;
+}
+
+bool Dominators::iterateForBlock(Graph& graph, BlockIndex i)
+{
+    BasicBlock* block = graph.m_blocks[i].get();
+    if (!block)
+        return false;
+    if (block->m_predecessors.isEmpty())
+        return false;
+    m_scratch.set(m_results[block->m_predecessors[0]]);
+    for (unsigned j = block->m_predecessors.size(); j-- > 1;)
+        m_scratch.filter(m_results[block->m_predecessors[j]]);
+    m_scratch.set(i);
+    return m_results[i].setAndCheck(m_scratch);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+