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

   1 //
   2 // DataFlowAnalysisBase.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;
  30 using System.Collections.Generic;
  31 using System.IO;
  32 using Mono.CodeContracts.Static.ControlFlow;
  33 using Mono.CodeContracts.Static.DataStructures;
  34
  35 namespace Mono.CodeContracts.Static.DataFlowAnalysis {
  36         abstract class DataFlowAnalysisBase<AState> :
  37                 IEqualityComparer<APC> {
  38                 protected ICFG CFG;
  39                 protected Dictionary<APC, AState> JoinState;
  40                 protected PriorityQueue<APC> pending;
  41                 private IWidenStrategy widen_strategy;
  42
  43                 protected DataFlowAnalysisBase (ICFG cfg)
  44                 {
  45                         this.CFG = cfg;
  46                         this.pending = new PriorityQueue<APC> (WorkingListComparer);
  47                         this.JoinState = new Dictionary<APC, AState> (this);
  48                         this.widen_strategy = null;
  49                 }
  50
  51                 #region IEqualityComparer<APC> Members
  52                 bool IEqualityComparer<APC>.Equals (APC x, APC y)
  53                 {
  54                         return x.Equals (y);
  55                 }
  56
  57                 int IEqualityComparer<APC>.GetHashCode (APC obj)
  58                 {
  59                         return obj.GetHashCode ();
  60                 }
  61                 #endregion
  62
  63                 public void Initialize (APC entryPoint, AState state)
  64                 {
  65                         this.JoinState.Add (entryPoint, state);
  66                         this.pending.Enqueue (entryPoint);
  67                 }
  68
  69                 public virtual void ComputeFixPoint ()
  70                 {
  71                         this.widen_strategy = new EdgeBasedWidening (20);
  72
  73                         while (this.pending.Count > 0) {
  74                                 APC next = this.pending.Dequeue ();
  75                                 AState state = MutableVersion (this.JoinState [next], next);
  76
  77                                 APC cur;
  78                                 bool repeatOuter = false;
  79                                 do {
  80                                         cur = next;
  81                                         if (!IsBottom (cur, state)) {
  82                                                 state = Transfer (cur, state);
  83                                         } else {
  84                                                 repeatOuter = true;
  85                                                 break;
  86                                         }
  87                                 } while (HasSingleSuccessor (cur, out next) && !RequiresJoining (next));
  88
  89                                 if (repeatOuter)
  90                                         continue;
  91
  92                                 foreach (APC successorAPC in Successors (cur)) {
  93                                         if (!IsBottom (successorAPC, state))
  94                                                 PushState (cur, successorAPC, state);
  95                                 }
  96                         }
  97                 }
  98
  99                 protected virtual void Dump (AState state)
 100                 {
 101                 }
 102
 103                 public IEnumerable<KeyValuePair<APC, AState>> States ()
 104                 {
 105                         return this.JoinState;
 106                 }
 107
 108                 protected abstract IEnumerable<APC> Successors (APC pc);
 109
 110                 protected virtual void PushState (APC current, APC next, AState state)
 111                 {
 112                         state = ImmutableVersion (state, next);
 113                         if (RequiresJoining (next)) {
 114                                 if (!JoinStateAtBlock (new Pair<APC, APC> (current, next), state))
 115                                         return;
 116                                 this.pending.Enqueue (next);
 117                         } else {
 118                                 this.JoinState [next] = state;
 119                                 this.pending.Enqueue (next);
 120                         }
 121                 }
 122
 123                 private bool JoinStateAtBlock (Pair<APC, APC> edge, AState state)
 124                 {
 125                         AState existingState;
 126                         if (this.JoinState.TryGetValue (edge.Value, out existingState)) {
 127                                 bool widen = this.widen_strategy.WantToWiden (edge.Key, edge.Value, IsBackEdge (edge.Key, edge.Value));
 128                                 AState joinedState;
 129                                 bool result = Join (edge, state, existingState, out joinedState, widen);
 130                                 if (result)
 131                                         this.JoinState [edge.Value] = ImmutableVersion (joinedState, edge.Value);
 132                                 return result;
 133                         }
 134
 135                         this.JoinState.Add (edge.Value, state);
 136                         return true;
 137                 }
 138
 139                 protected abstract bool IsBackEdge (APC from, APC to);
 140
 141                 protected abstract int WorkingListComparer (APC a, APC b);
 142
 143                 protected abstract bool Join (Pair<APC, APC> edge, AState newState, AState existingState, out AState joinedState, bool widen);
 144
 145                 protected abstract bool RequiresJoining (APC pc);
 146
 147                 protected abstract bool HasSingleSuccessor (APC pc, out APC next);
 148
 149                 protected abstract bool IsBottom (APC pc, AState state);
 150
 151                 protected abstract AState Transfer (APC pc, AState state);
 152
 153                 protected abstract AState MutableVersion (AState state, APC at);
 154                 protected abstract AState ImmutableVersion (AState state, APC at);
 155
 156                 public void PrintStatesAtJoinPoints (TextWriter tw)
 157                 {
 158                         foreach (APC apc in this.JoinState.Keys) {
 159                                 string str = this.JoinState [apc].ToString ().Replace (Environment.NewLine, Environment.NewLine + "   ");
 160                                 tw.WriteLine ("Block {0}, PC {1}: {2}", apc.Block, apc.Index, str);
 161                         }
 162                 }
 163         }
 164 }