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//
// DataFlowAnalysisBase.cs
//
// Authors:
// Alexander Chebaturkin (chebaturkin@gmail.com)
//
// Copyright (C) 2011 Alexander Chebaturkin
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections.Generic;
using System.IO;
using Mono.CodeContracts.Static.ControlFlow;
using Mono.CodeContracts.Static.DataStructures;
namespace Mono.CodeContracts.Static.DataFlowAnalysis {
abstract class DataFlowAnalysisBase<AState> :
IEqualityComparer<APC> {
protected ICFG CFG;
protected Dictionary<APC, AState> JoinState;
protected PriorityQueue<APC> pending;
private IWidenStrategy widen_strategy;
protected DataFlowAnalysisBase (ICFG cfg)
{
this.CFG = cfg;
this.pending = new PriorityQueue<APC> (WorkingListComparer);
this.JoinState = new Dictionary<APC, AState> (this);
this.widen_strategy = null;
}
#region IEqualityComparer<APC> Members
bool IEqualityComparer<APC>.Equals (APC x, APC y)
{
return x.Equals (y);
}
int IEqualityComparer<APC>.GetHashCode (APC obj)
{
return obj.GetHashCode ();
}
#endregion
public void Initialize (APC entryPoint, AState state)
{
this.JoinState.Add (entryPoint, state);
this.pending.Enqueue (entryPoint);
}
public virtual void ComputeFixPoint ()
{
this.widen_strategy = new EdgeBasedWidening (20);
while (this.pending.Count > 0) {
APC next = this.pending.Dequeue ();
AState state = MutableVersion (this.JoinState [next], next);
APC cur;
bool repeatOuter = false;
do {
cur = next;
if (!IsBottom (cur, state)) {
state = Transfer (cur, state);
} else {
repeatOuter = true;
break;
}
} while (HasSingleSuccessor (cur, out next) && !RequiresJoining (next));
if (repeatOuter)
continue;
foreach (APC successorAPC in Successors (cur)) {
if (!IsBottom (successorAPC, state))
PushState (cur, successorAPC, state);
}
}
}
protected virtual void Dump (AState state)
{
}
public IEnumerable<KeyValuePair<APC, AState>> States ()
{
return this.JoinState;
}
protected abstract IEnumerable<APC> Successors (APC pc);
protected virtual void PushState (APC current, APC next, AState state)
{
state = ImmutableVersion (state, next);
if (RequiresJoining (next)) {
if (!JoinStateAtBlock (new Pair<APC, APC> (current, next), state))
return;
this.pending.Enqueue (next);
} else {
this.JoinState [next] = state;
this.pending.Enqueue (next);
}
}
private bool JoinStateAtBlock (Pair<APC, APC> edge, AState state)
{
AState existingState;
if (this.JoinState.TryGetValue (edge.Value, out existingState)) {
bool widen = this.widen_strategy.WantToWiden (edge.Key, edge.Value, IsBackEdge (edge.Key, edge.Value));
AState joinedState;
bool result = Join (edge, state, existingState, out joinedState, widen);
if (result)
this.JoinState [edge.Value] = ImmutableVersion (joinedState, edge.Value);
return result;
}
this.JoinState.Add (edge.Value, state);
return true;
}
protected abstract bool IsBackEdge (APC from, APC to);
protected abstract int WorkingListComparer (APC a, APC b);
protected abstract bool Join (Pair<APC, APC> edge, AState newState, AState existingState, out AState joinedState, bool widen);
protected abstract bool RequiresJoining (APC pc);
protected abstract bool HasSingleSuccessor (APC pc, out APC next);
protected abstract bool IsBottom (APC pc, AState state);
protected abstract AState Transfer (APC pc, AState state);
protected abstract AState MutableVersion (AState state, APC at);
protected abstract AState ImmutableVersion (AState state, APC at);
public void PrintStatesAtJoinPoints (TextWriter tw)
{
foreach (APC apc in this.JoinState.Keys) {
string str = this.JoinState [apc].ToString ().Replace (Environment.NewLine, Environment.NewLine + " ");
tw.WriteLine ("Block {0}, PC {1}: {2}", apc.Block, apc.Index, str);
}
}
}
}
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