private void CreateSwitchConstruct(CFGBlockLogicalConstruct switchBlock, ILogicalConstruct parentConstruct,
SwitchData switchData, DominatorTree dominatorTree)
{
List<KeyValuePair<CFGBlockLogicalConstruct, List<int>>> cfgSuccessorToLabelsMap = GetOrderedCFGSuccessorToLabelsMap(switchData);
Dictionary<ILogicalConstruct, HashSet<ISingleEntrySubGraph>> validCaseEntryToDominatedNodesMap = GetValidCases(dominatorTree, switchBlock);
List<CaseLogicalConstruct> orderedCaseConstructs = new List<CaseLogicalConstruct>();
PairList<List<int>, CFGBlockLogicalConstruct> labelsToCFGSuccessorsList = new PairList<List<int>, CFGBlockLogicalConstruct>();
foreach (KeyValuePair<CFGBlockLogicalConstruct, List<int>> cfgSuccessorToLabelsPair in cfgSuccessorToLabelsMap)
{
ILogicalConstruct successor;
HashSet<ISingleEntrySubGraph> dominatedNodes;
if (LogicalFlowUtilities.TryGetParentConstructWithGivenParent(cfgSuccessorToLabelsPair.Key, parentConstruct, out successor) &&
validCaseEntryToDominatedNodesMap.TryGetValue(successor, out dominatedNodes))
{
CaseLogicalConstruct newCaseConstruct = new CaseLogicalConstruct(successor);
newCaseConstruct.CaseNumbers.AddRange(cfgSuccessorToLabelsPair.Value);
newCaseConstruct.Body.UnionWith(dominatedNodes.Cast<ILogicalConstruct>());
newCaseConstruct.AttachCaseConstructToGraph();
orderedCaseConstructs.Add(newCaseConstruct);
}
else
{
labelsToCFGSuccessorsList.Add(cfgSuccessorToLabelsPair.Value, cfgSuccessorToLabelsPair.Key);
}
}
CaseLogicalConstruct defaultCase = null;
CFGBlockLogicalConstruct defaultCFGSuccessor = GetCFGLogicalConstructFromBlock(switchData.DefaultCase);
ILogicalConstruct defaultSuccessor;
HashSet<ISingleEntrySubGraph> defaultCaseNodes;
if (LogicalFlowUtilities.TryGetParentConstructWithGivenParent(defaultCFGSuccessor, parentConstruct, out defaultSuccessor) &&
validCaseEntryToDominatedNodesMap.TryGetValue(defaultSuccessor, out defaultCaseNodes))
{
defaultCase = new CaseLogicalConstruct(defaultSuccessor);
if (HasSuccessors(defaultCaseNodes))
{
defaultCase.Body.UnionWith(defaultCaseNodes.Cast<ILogicalConstruct>());
}
defaultCase.AttachCaseConstructToGraph();
}
SwitchLogicalConstruct theSwitch = SwitchLogicalConstruct.GroupInSwitchConstruct(switchBlock, orderedCaseConstructs, labelsToCFGSuccessorsList, defaultCase, defaultCFGSuccessor);
UpdateDominatorTree(dominatorTree, theSwitch);
}
private void CreateControllerSwitchData()
{
V_0 = this.GetIndexOfLastNonNullElement(this.stateToStartBlock);
stackVariable6 = V_0 + 1;
V_0 = stackVariable6;
V_1 = new InstructionBlock[stackVariable6];
V_2 = 0;
while (V_2 < V_0)
{
if (!InstructionBlock.op_Equality(this.stateToStartBlock[V_2], null))
{
V_1[V_2] = this.stateToStartBlock[V_2];
}
else
{
V_1[V_2] = this.defaultStateEntry;
}
V_2 = V_2 + 1;
}
this.switchData = new Telerik.JustDecompiler.Cil.SwitchData(null, this.defaultStateEntry, V_1);
return;
}
public StateMachineCFGCleaner(ControlFlowGraph theCFG, SwitchData controllerSwitchData, InstructionBlock newEntryBlock)
{
this.theCFG = theCFG;
this.controllerSwitchData = controllerSwitchData;
this.newEntryBlock = newEntryBlock;
}
/// <summary>
/// Process each switch block to determine which cases lead to try/finally constructs.
/// </summary>
/// <remarks>
/// E.g.: If the cases from 3 to 5 lead to the same try/finally construct then there is a try/finally construct in the MoveNext method
/// that covers states 3, 4 and 5.
/// </remarks>
/// <param name="switchBlockInfo"></param>
private bool DetermineExceptionHandlingIntervalsFromSwitchData(SwitchData switchBlockInfo)
{
//Since the first try/finally that this switch covers can start at state 20, the complier will optimize this by subtracting 20 from the value of
//the state field.
int stateOffset = 0;
Instruction currentInstruction = switchBlockInfo.SwitchBlock.Last.Previous;
if (currentInstruction.OpCode.Code == Code.Sub)
{
currentInstruction = currentInstruction.Previous;
if (!StateMachineUtilities.TryGetOperandOfLdc(currentInstruction, out stateOffset))
{
return false;
}
currentInstruction = currentInstruction.Previous;
}
//The switch instruction block usually looks like this:
//
//ldarg.0 <- this
//ldfld stateField
//stloc.0
//ldloc.0 <- currentInstruction
//(ldc.i4 stateOffset)
//(sub)
//switch ....
currentInstruction = currentInstruction.Previous.Previous;
if (currentInstruction.OpCode.Code != Code.Ldfld || !(currentInstruction.Operand is FieldReference) ||
!CheckAndSaveStateField(currentInstruction.Operand as FieldReference))
{
//sanity check - the state field used by the Dispose method should be the same as the field used by the MoveNext method
return false;
}
//The algorithm works with the presumption that a try/finally construct contains a consecutive sequence of states.
InstructionBlock[] orderedCases = switchBlockInfo.OrderedCasesArray;
InstructionBlock currentBlock = null;
int intervalStart = -1;
int intervalEnd = -1;
ExceptionHandler exceptionHandler = null;
for (int i = 0; i < orderedCases.Length; i++)
{
InstructionBlock currentCase = GetActualCase(orderedCases[i]);
if (currentBlock != null && currentCase == currentBlock) //Current block will be null, if we still haven't found an exception handler.
{
intervalEnd = i + stateOffset;
continue;
}
ExceptionHandler theHandler;
if (!TryGetExceptionHandler(currentCase, out theHandler))
{
//There are cases where a state is never reached (i.e. the state field is never assigned this state number).
//This can create holes in the exception handlers, but since the states are never reached we can add them to the handler.
//(We work with the assumption that if state 3 and state 6 are handled by the same try/finally construct and 4 and 5 are not handled by
//any exception handler, then 4 and 5 are unreachable. True in general, but obfuscation can break this assumption.)
continue;
}
//We've found an exception handler.
if (currentBlock != null) //If currentBlock != null, then currentBlock != currentCase. This means that we have found a new exception
//handler, so we must store the data for the old one.
{
if (!TryCreateYieldExceptionHandler(intervalStart, intervalEnd, exceptionHandler))
{
return false;
}
}
else //Otherwise this is the first handler found for the switch block.
{
currentBlock = currentCase;
}
intervalStart = i + stateOffset;
exceptionHandler = theHandler;
}
return currentBlock == null ||
TryCreateYieldExceptionHandler(intervalStart, intervalEnd, exceptionHandler); //Store the data for the last found exception handler.
}
/// <summary>
/// Creates the controller switch data using the information gathered during the traversal of the state controller blocks.
/// </summary>
private void CreateControllerSwitchData()
{
int index = GetIndexOfLastNonNullElement(stateToStartBlock);
InstructionBlock[] finalCasesArray = new InstructionBlock[++index];
//Trim the excess elements of the cases array.
for (int i = 0; i < index; i++)
{
if (stateToStartBlock[i] == null)
{
finalCasesArray[i] = defaultStateEntry;
}
else
{
finalCasesArray[i] = stateToStartBlock[i];
}
}
this.switchData = new SwitchData(null, defaultStateEntry, finalCasesArray);
}
public YieldStateMachineControlFlowRebuilder(MethodSpecificContext moveNextMethodContext, SwitchData controllerSwitchData, FieldDefinition stateField)
{
this.moveNextMethodContext = moveNextMethodContext;
this.switchData = controllerSwitchData;
this.stateField = stateField;
}
/// <summary>
/// Process each switch block to determine which cases lead to try/finally constructs.
/// </summary>
/// <param name="switchBlockInfo"></param>
private bool DetermineExceptionHandlingStatesFromSwitchData(SwitchData switchBlockInfo)
{
//Since the first try/finally that this switch covers can start at state 20, the complier will optimize this by subtracting 20 from the value of
//the state field.
int stateOffset = 0;
Instruction currentInstruction = switchBlockInfo.SwitchBlock.Last.Previous;
if (currentInstruction.OpCode.Code == Code.Sub)
{
currentInstruction = currentInstruction.Previous;
if (!StateMachineUtilities.TryGetOperandOfLdc(currentInstruction, out stateOffset))
{
return false;
}
currentInstruction = currentInstruction.Previous;
}
InstructionBlock[] orderedCases = switchBlockInfo.OrderedCasesArray;
for (int i = 0; i < orderedCases.Length; i++)
{
InstructionBlock currentCase = GetActualCase(orderedCases[i]);
ExceptionHandler theHandler;
if (!TryGetExceptionHandler(currentCase, out theHandler))
{
continue;
}
//We've found an exception handler.
if (!this.handlerToStatesMap.ContainsKey(theHandler))
{
this.handlerToStatesMap.Add(theHandler, new HashSet<int>());
}
this.handlerToStatesMap[theHandler].Add(i + stateOffset);
}
return true;
}
private PairList<CFGBlockLogicalConstruct, List<int>> GetOrderedCFGSuccessorToLabelsMap(SwitchData switchData)
{
//Ugly but effective. Sorry
PairList<CFGBlockLogicalConstruct, List<int>> result = new PairList<CFGBlockLogicalConstruct, List<int>>();
Dictionary<InstructionBlock, KeyValuePair<int, List<int>>> blockSuccessorToResultPositionMap =
new Dictionary<InstructionBlock, KeyValuePair<int, List<int>>>();
for (int i = 0; i < switchData.OrderedCasesArray.Length; i++)
{
InstructionBlock instructionBlock = switchData.OrderedCasesArray[i];
if (instructionBlock != switchData.DefaultCase)
{
KeyValuePair<int, List<int>> positionToLabelListPair;
if (!blockSuccessorToResultPositionMap.TryGetValue(instructionBlock, out positionToLabelListPair))
{
positionToLabelListPair = new KeyValuePair<int, List<int>>(result.Count, new List<int>());
result.Add(GetCFGLogicalConstructFromBlock(instructionBlock), positionToLabelListPair.Value);
blockSuccessorToResultPositionMap.Add(instructionBlock, positionToLabelListPair);
}
positionToLabelListPair.Value.Add(i);
}
}
return result;
}
