JavaScriptCore-7601.1.46.3.tar.gz

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

diff --git a/dfg/DFGConstantHoistingPhase.cpp b/dfg/DFGConstantHoistingPhase.cpp
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+/*
+ * Copyright (C) 2015 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 "DFGConstantHoistingPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGGraph.h"
+#include "DFGInsertionSet.h"
+#include "DFGPhase.h"
+#include "DFGPredictionPropagationPhase.h"
+#include "DFGVariableAccessDataDump.h"
+#include "JSCInlines.h"
+
+namespace JSC { namespace DFG {
+
+namespace {
+
+class ConstantHoistingPhase : public Phase {
+public:
+    ConstantHoistingPhase(Graph& graph)
+        : Phase(graph, "constant hoisting")
+    {
+    }
+    
+    bool run()
+    {
+        DFG_ASSERT(m_graph, nullptr, m_graph.m_form == SSA);
+        
+        m_graph.clearReplacements();
+        
+        HashMap<FrozenValue*, Node*> jsValues;
+        HashMap<FrozenValue*, Node*> doubleValues;
+        HashMap<FrozenValue*, Node*> int52Values;
+        
+        auto valuesFor = [&] (NodeType op) -> HashMap<FrozenValue*, Node*>& {
+            // Use a roundabout approach because clang thinks that this closure returning a
+            // reference to a stack-allocated value in outer scope is a bug. It's not.
+            HashMap<FrozenValue*, Node*>* result;
+            
+            switch (op) {
+            case JSConstant:
+                result = &jsValues;
+                break;
+            case DoubleConstant:
+                result = &doubleValues;
+                break;
+            case Int52Constant:
+                result = &int52Values;
+                break;
+            default:
+                DFG_CRASH(m_graph, nullptr, "Invalid node type in valuesFor()");
+                result = nullptr;
+                break;
+            }
+            
+            return *result;
+        };
+        
+        Vector<Node*> toFree;
+        
+        for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
+            unsigned sourceIndex = 0;
+            unsigned targetIndex = 0;
+            while (sourceIndex < block->size()) {
+                Node* node = block->at(sourceIndex++);
+                switch (node->op()) {
+                case JSConstant:
+                case DoubleConstant:
+                case Int52Constant: {
+                    HashMap<FrozenValue*, Node*>& values = valuesFor(node->op());
+                    auto result = values.add(node->constant(), node);
+                    if (result.isNewEntry)
+                        node->origin = NodeOrigin();
+                    else {
+                        node->setReplacement(result.iterator->value);
+                        toFree.append(node);
+                    }
+                    break;
+                }
+                default:
+                    block->at(targetIndex++) = node;
+                    break;
+                }
+            }
+            block->resize(targetIndex);
+        }
+        
+        // Insert the constants into the root block.
+        InsertionSet insertionSet(m_graph);
+        auto insertConstants = [&] (const HashMap<FrozenValue*, Node*>& values) {
+            for (auto& entry : values)
+                insertionSet.insert(0, entry.value);
+        };
+        insertConstants(jsValues);
+        insertConstants(doubleValues);
+        insertConstants(int52Values);
+        insertionSet.execute(m_graph.block(0));
+        
+        // Perform all of the substitutions. We want all instances of the removed constants to
+        // point at their replacements.
+        for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
+            for (Node* node : *block)
+                m_graph.performSubstitution(node);
+        }
+        
+        // And finally free the constants that we removed.
+        for (Node* node : toFree)
+            m_graph.m_allocator.free(node);
+        
+        return true;
+    }
+};
+
+} // anonymous namespace
+    
+bool performConstantHoisting(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG Constant Hoisting Phase");
+    return runPhase<ConstantHoistingPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+