mcs/class/Mono.CodeContracts/Mono.CodeContracts.Static.DataFlowAnalysis/ForwardDataFlowAnalysisBase.cs

   1 //
   2 // ForwardDataFlowAnalysisBase.cs
   3 //
   4 // Authors:
   5 //      Alexander Chebaturkin (chebaturkin@gmail.com)
   6 //
   7 // Copyright (C) 2011 Alexander Chebaturkin
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining
  10 // a copy of this software and associated documentation files (the
  11 // "Software"), to deal in the Software without restriction, including
  12 // without limitation the rights to use, copy, modify, merge, publish,
  13 // distribute, sublicense, and/or sell copies of the Software, and to
  14 // permit persons to whom the Software is furnished to do so, subject to
  15 // the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be
  18 // included in all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27 //
  28
  29 using System.Collections.Generic;
  30 using Mono.CodeContracts.Static.ControlFlow;
  31 using Mono.CodeContracts.Static.DataStructures;
  32
  33 namespace Mono.CodeContracts.Static.DataFlowAnalysis {
  34         abstract class ForwardDataFlowAnalysisBase<AState> : DataFlowAnalysisBase<AState> {
  35                 private readonly Dictionary<APC, AState> post_state = new Dictionary<APC, AState> ();
  36
  37                 protected ForwardDataFlowAnalysisBase (ICFG cfg) : base (cfg)
  38                 {
  39                 }
  40
  41                 public bool GetPreState (APC pc, out AState state)
  42                 {
  43                         bool noInfo;
  44                         state = GetPreState (pc, default(AState), out noInfo);
  45                         return !noInfo;
  46                 }
  47
  48                 public AState GetPreStateWithDefault (APC apc, AState ifMissing)
  49                 {
  50                         bool noInfo;
  51                         AState preState = GetPreState (apc, default(AState), out noInfo);
  52                         return noInfo ? ifMissing : preState;
  53                 }
  54
  55                 private AState GetPreState (APC apc, AState ifMissing, out bool noInfo)
  56                 {
  57                         LispList<APC> rest = null;
  58                         APC tmp = apc;
  59                         APC singlePredecessor;
  60                         AState state;
  61                         bool weHaveState;
  62                         while (!(weHaveState = this.JoinState.TryGetValue (tmp, out state)) &&
  63                                !RequiresJoining (tmp) && this.CFG.HasSinglePredecessor (tmp, out singlePredecessor)) {
  64                                 tmp = singlePredecessor;
  65
  66                                 rest = rest.Cons (tmp);
  67                         }
  68
  69                         if (!weHaveState) {
  70                                 noInfo = true;
  71                                 return ifMissing;
  72                         }
  73
  74                         bool listWasNotEmpty = rest != null;
  75                         while (rest != null) {
  76                                 if (IsBottom (rest.Head, state)) {
  77                                         noInfo = false;
  78                                         return state;
  79                                 }
  80                                 state = MutableVersion (state, rest.Head);
  81                                 state = Transfer (rest.Head, state);
  82                                 if (IsBottom (rest.Head, state)) {
  83                                         noInfo = false;
  84                                         return state;
  85                                 }
  86
  87                                 rest = rest.Tail;
  88                                 if (rest != null)
  89                                         this.JoinState.Add (rest.Head, ImmutableVersion (state, rest.Head));
  90                         }
  91
  92                         if (listWasNotEmpty)
  93                                 this.JoinState.Add (apc, ImmutableVersion (state, apc));
  94
  95                         noInfo = false;
  96                         return state;
  97                 }
  98
  99                 public bool GetPostState (APC apc, out AState result)
 100                 {
 101                         if (this.post_state.TryGetValue (apc, out result))
 102                                 return true;
 103
 104                         APC singleSuccessor;
 105                         if (apc.Block.Count <= apc.Index)
 106                                 return GetPreState (apc, out result);
 107
 108                         if (this.CFG.HasSingleSuccessor (apc, out singleSuccessor) && !RequiresJoining (singleSuccessor))
 109                                 return GetPreState (singleSuccessor, out result);
 110
 111                         AState ifFound;
 112                         if (!GetPreState (apc, out ifFound))
 113                                 return false;
 114
 115                         result = MutableVersion (ifFound, apc);
 116                         result = Transfer (apc, result);
 117
 118                         this.post_state.Add (apc, result);
 119                         return true;
 120                 }
 121
 122                 public void Run (AState startState)
 123                 {
 124                         Initialize (this.CFG.Entry, startState);
 125                         ComputeFixPoint ();
 126                 }
 127
 128                 protected override int WorkingListComparer (APC a, APC b)
 129                 {
 130                         return b.Block.ReversePostOrderIndex - a.Block.ReversePostOrderIndex;
 131                 }
 132
 133                 protected override bool RequiresJoining (APC pc)
 134                 {
 135                         return this.CFG.IsJoinPoint (pc);
 136                 }
 137
 138                 protected override bool HasSingleSuccessor (APC pc, out APC next)
 139                 {
 140                         return this.CFG.HasSingleSuccessor (pc, out next);
 141                 }
 142
 143                 protected override IEnumerable<APC> Successors (APC pc)
 144                 {
 145                         return this.CFG.Successors (pc);
 146                 }
 147
 148                 protected override bool IsBackEdge (APC from, APC to)
 149                 {
 150                         //todo: implement this
 151                         //can't be false, because back edges means having cycles, so we definitely have to widen
 152                         return true;
 153                 }
 154         }
 155 }