dfg/DFGCriticalEdgeBreakingPhase.cpp

   1 /*
   2  * Copyright (C) 2013 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,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  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 "DFGCriticalEdgeBreakingPhase.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGBasicBlockInlines.h"
  32 #include "DFGBlockInsertionSet.h"
  33 #include "DFGGraph.h"
  34 #include "DFGPhase.h"
  35 #include "JSCInlines.h"
  36 #include <wtf/HashMap.h>
  37
  38 namespace JSC { namespace DFG {
  39
  40 class CriticalEdgeBreakingPhase : public Phase {
  41 public:
  42     CriticalEdgeBreakingPhase(Graph& graph)
  43         : Phase(graph, "critical edge breaking")
  44         , m_insertionSet(graph)
  45     {
  46     }
  47
  48     bool run()
  49     {
  50         for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
  51             BasicBlock* block = m_graph.block(blockIndex);
  52             if (!block)
  53                 continue;
  54
  55             // An edge A->B is critical if A has multiple successor and B has multiple
  56             // predecessors. Thus we fail early if we don't have multiple successors.
  57
  58             if (block->numSuccessors() <= 1)
  59                 continue;
  60
  61             for (unsigned i = block->numSuccessors(); i--;) {
  62                 BasicBlock** successor = &block->successor(i);
  63                 if ((*successor)->predecessors.size() <= 1)
  64                     continue;
  65
  66                 breakCriticalEdge(block, successor);
  67             }
  68         }
  69
  70         return m_insertionSet.execute();
  71     }
  72
  73 private:
  74     void breakCriticalEdge(BasicBlock* predecessor, BasicBlock** successor)
  75     {
  76         // Note that we pass NaN for the count of the critical edge block, because we honestly
  77         // don't know its execution frequency.
  78         BasicBlock* pad = m_insertionSet.insertBefore(*successor, PNaN);
  79         pad->appendNode(
  80             m_graph, SpecNone, Jump, (*successor)->at(0)->origin, OpInfo(*successor));
  81         pad->predecessors.append(predecessor);
  82         (*successor)->replacePredecessor(predecessor, pad);
  83
  84         *successor = pad;
  85     }
  86
  87     BlockInsertionSet m_insertionSet;
  88 };
  89
  90 bool performCriticalEdgeBreaking(Graph& graph)
  91 {
  92     SamplingRegion samplingRegion("DFG Critical Edge Breaking Phase");
  93     return runPhase<CriticalEdgeBreakingPhase>(graph);
  94 }
  95
  96 } } // namespace JSC::DFG
  97
  98 #endif // ENABLE(DFG_JIT)
  99
 100