dfg/DFGMayExit.cpp

   1 /*
   2  * Copyright (C) 2014, 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,
  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 "DFGMayExit.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGGraph.h"
  32 #include "DFGNode.h"
  33 #include "Operations.h"
  34
  35 namespace JSC { namespace DFG {
  36
  37 namespace {
  38
  39 class EdgeMayExit {
  40 public:
  41     EdgeMayExit()
  42         : m_result(false)
  43     {
  44     }
  45
  46     void operator()(Node*, Edge edge)
  47     {
  48         if (edge.willHaveCheck()) {
  49             m_result = true;
  50             return;
  51         }
  52
  53         switch (edge.useKind()) {
  54         // These are shady because nodes that have these use kinds will typically exit for
  55         // unrelated reasons. For example CompareEq doesn't usually exit, but if it uses ObjectUse
  56         // then it will.
  57         case ObjectUse:
  58         case ObjectOrOtherUse:
  59             m_result = true;
  60             break;
  61
  62         // These are shady because they check the structure even if the type of the child node
  63         // passes the StringObject type filter.
  64         case StringObjectUse:
  65         case StringOrStringObjectUse:
  66             m_result = true;
  67             break;
  68
  69         default:
  70             break;
  71         }
  72     }
  73
  74     bool result() const { return m_result; }
  75
  76 private:
  77     bool m_result;
  78 };
  79
  80 } // anonymous namespace
  81
  82 bool mayExit(Graph& graph, Node* node)
  83 {
  84     switch (node->op()) {
  85     // This is a carefully curated list of nodes that definitely do not exit. We try to be very
  86     // conservative when maintaining this list, because adding new node types to it doesn't
  87     // generally make things a lot better but it might introduce insanely subtle bugs.
  88     case SetArgument:
  89     case JSConstant:
  90     case DoubleConstant:
  91     case Int52Constant:
  92     case MovHint:
  93     case SetLocal:
  94     case Flush:
  95     case Phantom:
  96     case Check:
  97     case GetLocal:
  98     case LoopHint:
  99     case Phi:
 100     case Upsilon:
 101     case ZombieHint:
 102     case BottomValue:
 103     case PutHint:
 104     case PhantomNewObject:
 105     case PutStack:
 106     case KillStack:
 107     case GetStack:
 108     case GetCallee:
 109     case GetArgumentCount:
 110     case GetScope:
 111     case PhantomLocal:
 112     case CountExecution:
 113     case Jump:
 114     case Branch:
 115     case Unreachable:
 116     case DoubleRep:
 117     case Int52Rep:
 118     case ValueRep:
 119         break;
 120
 121     default:
 122         // If in doubt, return true.
 123         return true;
 124     }
 125
 126     EdgeMayExit functor;
 127     DFG_NODE_DO_TO_CHILDREN(graph, node, functor);
 128     return functor.result();
 129 }
 130
 131 } } // namespace JSC::DFG
 132
 133 #endif // ENABLE(DFG_JIT)