dfg/DFGConstantHoistingPhase.cpp

   1 /*
   2  * Copyright (C) 2015 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "DFGConstantHoistingPhase.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGGraph.h"
  32 #include "DFGInsertionSet.h"
  33 #include "DFGPhase.h"
  34 #include "DFGPredictionPropagationPhase.h"
  35 #include "DFGVariableAccessDataDump.h"
  36 #include "JSCInlines.h"
  37
  38 namespace JSC { namespace DFG {
  39
  40 namespace {
  41
  42 class ConstantHoistingPhase : public Phase {
  43 public:
  44     ConstantHoistingPhase(Graph& graph)
  45         : Phase(graph, "constant hoisting")
  46     {
  47     }
  48
  49     bool run()
  50     {
  51         DFG_ASSERT(m_graph, nullptr, m_graph.m_form == SSA);
  52
  53         m_graph.clearReplacements();
  54
  55         HashMap<FrozenValue*, Node*> jsValues;
  56         HashMap<FrozenValue*, Node*> doubleValues;
  57         HashMap<FrozenValue*, Node*> int52Values;
  58
  59         auto valuesFor = [&] (NodeType op) -> HashMap<FrozenValue*, Node*>& {
  60             // Use a roundabout approach because clang thinks that this closure returning a
  61             // reference to a stack-allocated value in outer scope is a bug. It's not.
  62             HashMap<FrozenValue*, Node*>* result;
  63
  64             switch (op) {
  65             case JSConstant:
  66                 result = &jsValues;
  67                 break;
  68             case DoubleConstant:
  69                 result = &doubleValues;
  70                 break;
  71             case Int52Constant:
  72                 result = &int52Values;
  73                 break;
  74             default:
  75                 DFG_CRASH(m_graph, nullptr, "Invalid node type in valuesFor()");
  76                 result = nullptr;
  77                 break;
  78             }
  79
  80             return *result;
  81         };
  82
  83         Vector<Node*> toFree;
  84
  85         for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
  86             unsigned sourceIndex = 0;
  87             unsigned targetIndex = 0;
  88             while (sourceIndex < block->size()) {
  89                 Node* node = block->at(sourceIndex++);
  90                 switch (node->op()) {
  91                 case JSConstant:
  92                 case DoubleConstant:
  93                 case Int52Constant: {
  94                     HashMap<FrozenValue*, Node*>& values = valuesFor(node->op());
  95                     auto result = values.add(node->constant(), node);
  96                     if (result.isNewEntry)
  97                         node->origin = NodeOrigin();
  98                     else {
  99                         node->setReplacement(result.iterator->value);
 100                         toFree.append(node);
 101                     }
 102                     break;
 103                 }
 104                 default:
 105                     block->at(targetIndex++) = node;
 106                     break;
 107                 }
 108             }
 109             block->resize(targetIndex);
 110         }
 111
 112         // Insert the constants into the root block.
 113         InsertionSet insertionSet(m_graph);
 114         auto insertConstants = [&] (const HashMap<FrozenValue*, Node*>& values) {
 115             for (auto& entry : values)
 116                 insertionSet.insert(0, entry.value);
 117         };
 118         insertConstants(jsValues);
 119         insertConstants(doubleValues);
 120         insertConstants(int52Values);
 121         insertionSet.execute(m_graph.block(0));
 122
 123         // Perform all of the substitutions. We want all instances of the removed constants to
 124         // point at their replacements.
 125         for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
 126             for (Node* node : *block)
 127                 m_graph.performSubstitution(node);
 128         }
 129
 130         // And finally free the constants that we removed.
 131         for (Node* node : toFree)
 132             m_graph.m_allocator.free(node);
 133
 134         return true;
 135     }
 136 };
 137
 138 } // anonymous namespace
 139
 140 bool performConstantHoisting(Graph& graph)
 141 {
 142     SamplingRegion samplingRegion("DFG Constant Hoisting Phase");
 143     return runPhase<ConstantHoistingPhase>(graph);
 144 }
 145
 146 } } // namespace JSC::DFG
 147
 148 #endif // ENABLE(DFG_JIT)
 149