void AnalyzeMoveNext()
{
MethodDefinition moveNextMethod = enumeratorType.Methods.FirstOrDefault(m => m.Name == "MoveNext");
ILBlock ilMethod = CreateILAst(moveNextMethod);
if (ilMethod.Body.Count == 0)
{
throw new SymbolicAnalysisFailedException();
}
ILExpression lastReturnArg;
if (!ilMethod.Body.Last().Match(ILCode.Ret, out lastReturnArg))
{
throw new SymbolicAnalysisFailedException();
}
// There are two possibilities:
if (lastReturnArg.Code == ILCode.Ldloc)
{
// a) the compiler uses a variable for returns (in debug builds, or when there are try-finally blocks)
returnVariable = (ILVariable)lastReturnArg.Operand;
returnLabel = ilMethod.Body.ElementAtOrDefault(ilMethod.Body.Count - 2) as ILLabel;
if (returnLabel == null)
{
throw new SymbolicAnalysisFailedException();
}
}
else
{
// b) the compiler directly returns constants
returnVariable = null;
returnLabel = null;
// In this case, the last return must return false.
if (lastReturnArg.Code != ILCode.Ldc_I4 || (int)lastReturnArg.Operand != 0)
{
throw new SymbolicAnalysisFailedException();
}
}
ILTryCatchBlock tryFaultBlock = ilMethod.Body[0] as ILTryCatchBlock;
List <ILNode> body;
int bodyLength;
if (tryFaultBlock != null)
{
// there are try-finally blocks
if (returnVariable == null) // in this case, we must use a return variable
{
throw new SymbolicAnalysisFailedException();
}
// must be a try-fault block:
if (tryFaultBlock.CatchBlocks.Count != 0 || tryFaultBlock.FinallyBlock != null || tryFaultBlock.FaultBlock == null)
{
throw new SymbolicAnalysisFailedException();
}
ILBlock faultBlock = tryFaultBlock.FaultBlock;
// Ensure the fault block contains the call to Dispose().
if (faultBlock.Body.Count != 2)
{
throw new SymbolicAnalysisFailedException();
}
MethodReference disposeMethodRef;
ILExpression disposeArg;
if (!faultBlock.Body[0].Match(ILCode.Call, out disposeMethodRef, out disposeArg))
{
throw new SymbolicAnalysisFailedException();
}
if (GetMethodDefinition(disposeMethodRef) != disposeMethod || !disposeArg.MatchThis())
{
throw new SymbolicAnalysisFailedException();
}
if (!faultBlock.Body[1].Match(ILCode.Endfinally))
{
throw new SymbolicAnalysisFailedException();
}
body = tryFaultBlock.TryBlock.Body;
bodyLength = body.Count;
}
else
{
// no try-finally blocks
body = ilMethod.Body;
if (returnVariable == null)
{
bodyLength = body.Count - 1; // all except for the return statement
}
else
{
bodyLength = body.Count - 2; // all except for the return label and statement
}
}
// Now verify that the last instruction in the body is 'ret(false)'
if (returnVariable != null)
{
// If we don't have a return variable, we already verified that above.
// If we do have one, check for 'stloc(returnVariable, ldc.i4(0))'
// Maybe might be a jump to the return label after the stloc:
ILExpression leave = body.ElementAtOrDefault(bodyLength - 1) as ILExpression;
if (leave != null && (leave.Code == ILCode.Br || leave.Code == ILCode.Leave) && leave.Operand == returnLabel)
{
bodyLength--;
}
ILExpression store0 = body.ElementAtOrDefault(bodyLength - 1) as ILExpression;
if (store0 == null || store0.Code != ILCode.Stloc || store0.Operand != returnVariable)
{
throw new SymbolicAnalysisFailedException();
}
if (store0.Arguments[0].Code != ILCode.Ldc_I4 || (int)store0.Arguments[0].Operand != 0)
{
throw new SymbolicAnalysisFailedException();
}
bodyLength--; // don't conside the stloc instruction to be part of the body
}
// verify that the last element in the body is a label pointing to the 'ret(false)'
returnFalseLabel = body.ElementAtOrDefault(bodyLength - 1) as ILLabel;
if (returnFalseLabel == null)
{
throw new SymbolicAnalysisFailedException();
}
var rangeAnalysis = new StateRangeAnalysis(body[0], StateRangeAnalysisMode.IteratorMoveNext, stateField);
int pos = rangeAnalysis.AssignStateRanges(body, bodyLength);
rangeAnalysis.EnsureLabelAtPos(body, ref pos, ref bodyLength);
var labels = rangeAnalysis.CreateLabelRangeMapping(body, pos, bodyLength);
ConvertBody(body, pos, bodyLength, labels);
}
void ConvertBody(List <ILNode> body, int startPos, int bodyLength, List <KeyValuePair <ILLabel, StateRange> > labels)
{
newBody = new List <ILNode>();
newBody.Add(MakeGoTo(labels, 0));
List <SetState> stateChanges = new List <SetState>();
int currentState = -1;
// Copy all instructions from the old body to newBody.
for (int pos = startPos; pos < bodyLength; pos++)
{
ILExpression expr = body[pos] as ILExpression;
if (expr != null && expr.Code == ILCode.Stfld && expr.Arguments[0].MatchThis())
{
// Handle stores to 'state' or 'current'
if (GetFieldDefinition(expr.Operand as FieldReference) == stateField)
{
if (expr.Arguments[1].Code != ILCode.Ldc_I4)
{
throw new SymbolicAnalysisFailedException();
}
currentState = (int)expr.Arguments[1].Operand;
stateChanges.Add(new SetState(newBody.Count, currentState));
}
else if (GetFieldDefinition(expr.Operand as FieldReference) == currentField)
{
newBody.Add(new ILExpression(ILCode.YieldReturn, null, expr.Arguments[1]));
}
else
{
newBody.Add(body[pos]);
}
}
else if (returnVariable != null && expr != null && expr.Code == ILCode.Stloc && expr.Operand == returnVariable)
{
// handle store+branch to the returnVariable
ILExpression br = body.ElementAtOrDefault(++pos) as ILExpression;
if (br == null || !(br.Code == ILCode.Br || br.Code == ILCode.Leave) || br.Operand != returnLabel || expr.Arguments[0].Code != ILCode.Ldc_I4)
{
throw new SymbolicAnalysisFailedException();
}
int val = (int)expr.Arguments[0].Operand;
if (val == 0)
{
newBody.Add(MakeGoTo(returnFalseLabel));
}
else if (val == 1)
{
newBody.Add(MakeGoTo(labels, currentState));
}
else
{
throw new SymbolicAnalysisFailedException();
}
}
else if (expr != null && expr.Code == ILCode.Ret)
{
if (expr.Arguments.Count != 1 || expr.Arguments[0].Code != ILCode.Ldc_I4)
{
throw new SymbolicAnalysisFailedException();
}
// handle direct return (e.g. in release builds)
int val = (int)expr.Arguments[0].Operand;
if (val == 0)
{
newBody.Add(MakeGoTo(returnFalseLabel));
}
else if (val == 1)
{
newBody.Add(MakeGoTo(labels, currentState));
}
else
{
throw new SymbolicAnalysisFailedException();
}
}
else if (expr != null && expr.Code == ILCode.Call && expr.Arguments.Count == 1 && expr.Arguments[0].MatchThis())
{
MethodDefinition method = GetMethodDefinition(expr.Operand as MethodReference);
if (method == null)
{
throw new SymbolicAnalysisFailedException();
}
Interval interval;
if (method == disposeMethod)
{
// Explicit call to dispose is used for "yield break;" within the method.
ILExpression br = body.ElementAtOrDefault(++pos) as ILExpression;
if (br == null || !(br.Code == ILCode.Br || br.Code == ILCode.Leave) || br.Operand != returnFalseLabel)
{
throw new SymbolicAnalysisFailedException();
}
newBody.Add(MakeGoTo(returnFalseLabel));
}
else if (finallyMethodToStateInterval.TryGetValue(method, out interval))
{
// Call to Finally-method
int index = stateChanges.FindIndex(ss => ss.NewState >= interval.Start && ss.NewState <= interval.End);
if (index < 0)
{
throw new SymbolicAnalysisFailedException();
}
ILLabel label = new ILLabel();
label.Name = "JumpOutOfTryFinally" + interval.Start + "_" + interval.End;
newBody.Add(new ILExpression(ILCode.Leave, label));
SetState stateChange = stateChanges[index];
// Move all instructions from stateChange.Pos to newBody.Count into a try-block
stateChanges.RemoveRange(index, stateChanges.Count - index); // remove all state changes up to the one we found
ILTryCatchBlock tryFinally = new ILTryCatchBlock();
tryFinally.TryBlock = new ILBlock(newBody.GetRange(stateChange.NewBodyPos, newBody.Count - stateChange.NewBodyPos));
newBody.RemoveRange(stateChange.NewBodyPos, newBody.Count - stateChange.NewBodyPos); // remove all nodes that we just moved into the try block
tryFinally.CatchBlocks = new List <ILTryCatchBlock.CatchBlock>();
tryFinally.FinallyBlock = ConvertFinallyBlock(method);
newBody.Add(tryFinally);
newBody.Add(label);
}
}
else
{
newBody.Add(body[pos]);
}
}
newBody.Add(new ILExpression(ILCode.YieldBreak, null));
}
ControlFlowGraph BuildGraph(List <ILNode> nodes, ILLabel entryLabel)
{
int index = 0;
List <ControlFlowNode> cfNodes = new List <ControlFlowNode>();
ControlFlowNode entryPoint = new ControlFlowNode(index++, 0, ControlFlowNodeType.EntryPoint);
cfNodes.Add(entryPoint);
ControlFlowNode regularExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.RegularExit);
cfNodes.Add(regularExit);
ControlFlowNode exceptionalExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.ExceptionalExit);
cfNodes.Add(exceptionalExit);
// Create graph nodes
labelToCfNode = new Dictionary <ILLabel, ControlFlowNode>();
Dictionary <ILNode, ControlFlowNode> astNodeToCfNode = new Dictionary <ILNode, ControlFlowNode>();
foreach (ILBasicBlock node in nodes)
{
ControlFlowNode cfNode = new ControlFlowNode(index++, -1, ControlFlowNodeType.Normal);
cfNodes.Add(cfNode);
astNodeToCfNode[node] = cfNode;
cfNode.UserData = node;
// Find all contained labels
foreach (ILLabel label in node.GetSelfAndChildrenRecursive <ILLabel>())
{
labelToCfNode[label] = cfNode;
}
}
// Entry endge
ControlFlowNode entryNode = labelToCfNode[entryLabel];
ControlFlowEdge entryEdge = new ControlFlowEdge(entryPoint, entryNode, JumpType.Normal);
entryPoint.Outgoing.Add(entryEdge);
entryNode.Incoming.Add(entryEdge);
// Create edges
foreach (ILBasicBlock node in nodes)
{
ControlFlowNode source = astNodeToCfNode[node];
// Find all branches
foreach (ILLabel target in node.GetSelfAndChildrenRecursive <ILExpression>(e => e.IsBranch()).SelectMany(e => e.GetBranchTargets()))
{
ControlFlowNode destination;
// Labels which are out of out scope will not be in the collection
// Insert self edge only if we are sure we are a loop
if (labelToCfNode.TryGetValue(target, out destination) && (destination != source || target == node.Body.FirstOrDefault()))
{
ControlFlowEdge edge = new ControlFlowEdge(source, destination, JumpType.Normal);
source.Outgoing.Add(edge);
destination.Incoming.Add(edge);
}
}
}
return(new ControlFlowGraph(cfNodes.ToArray()));
}
/// <summary>
/// Get the first expression to be excecuted if the instruction pointer is at the start of the given node.
/// Try blocks may not be entered in any way. If possible, the try block is returned as the node to be executed.
/// </summary>
ILNode Enter(ILNode node, HashSet <ILNode> visitedNodes)
{
if (node == null)
{
throw new ArgumentNullException();
}
if (!visitedNodes.Add(node))
{
return(null); // Infinite loop
}
ILLabel label = node as ILLabel;
if (label != null)
{
return(Exit(label, visitedNodes));
}
ILExpression expr = node as ILExpression;
if (expr != null)
{
if (expr.Code == ILCode.Br || expr.Code == ILCode.Leave)
{
ILLabel target = (ILLabel)expr.Operand;
// Early exit - same try-block
if (GetParents(expr).OfType <ILTryCatchBlock>().FirstOrDefault() == GetParents(target).OfType <ILTryCatchBlock>().FirstOrDefault())
{
return(Enter(target, visitedNodes));
}
// Make sure we are not entering any try-block
var srcTryBlocks = GetParents(expr).OfType <ILTryCatchBlock>().Reverse().ToList();
var dstTryBlocks = GetParents(target).OfType <ILTryCatchBlock>().Reverse().ToList();
// Skip blocks that we are already in
int i = 0;
while (i < srcTryBlocks.Count && i < dstTryBlocks.Count && srcTryBlocks[i] == dstTryBlocks[i])
{
i++;
}
if (i == dstTryBlocks.Count)
{
return(Enter(target, visitedNodes));
}
else
{
ILTryCatchBlock dstTryBlock = dstTryBlocks[i];
// Check that the goto points to the start
ILTryCatchBlock current = dstTryBlock;
while (current != null)
{
foreach (ILNode n in current.TryBlock.Body)
{
if (n is ILLabel)
{
if (n == target)
{
return(dstTryBlock);
}
}
else if (!n.Match(ILCode.Nop))
{
current = n as ILTryCatchBlock;
break;
}
}
}
return(null);
}
}
else if (expr.Code == ILCode.Nop)
{
return(Exit(expr, visitedNodes));
}
else if (expr.Code == ILCode.LoopOrSwitchBreak)
{
ILNode breakBlock = GetParents(expr).First(n => n is ILWhileLoop || n is ILSwitch);
return(Exit(breakBlock, new HashSet <ILNode>()
{
expr
}));
}
else if (expr.Code == ILCode.LoopContinue)
{
ILNode continueBlock = GetParents(expr).First(n => n is ILWhileLoop);
return(Enter(continueBlock, new HashSet <ILNode>()
{
expr
}));
}
else
{
return(expr);
}
}
ILBlock block = node as ILBlock;
if (block != null)
{
if (block.EntryGoto != null)
{
return(Enter(block.EntryGoto, visitedNodes));
}
else if (block.Body.Count > 0)
{
return(Enter(block.Body[0], visitedNodes));
}
else
{
return(Exit(block, visitedNodes));
}
}
ILCondition cond = node as ILCondition;
if (cond != null)
{
return(cond.Condition);
}
ILWhileLoop loop = node as ILWhileLoop;
if (loop != null)
{
if (loop.Condition != null)
{
return(loop.Condition);
}
else
{
return(Enter(loop.BodyBlock, visitedNodes));
}
}
ILTryCatchBlock tryCatch = node as ILTryCatchBlock;
if (tryCatch != null)
{
return(tryCatch);
}
ILSwitch ilSwitch = node as ILSwitch;
if (ilSwitch != null)
{
return(ilSwitch.Condition);
}
throw new NotSupportedException(node.GetType().ToString());
}
List <ILNode> FindLoops(HashSet <ControlFlowNode> scope, ControlFlowNode entryPoint, bool excludeEntryPoint)
{
List <ILNode> result = new List <ILNode>();
// Do not modify entry data
scope = new HashSet <ControlFlowNode>(scope);
Queue <ControlFlowNode> agenda = new Queue <ControlFlowNode>();
agenda.Enqueue(entryPoint);
while (agenda.Count > 0)
{
ControlFlowNode node = agenda.Dequeue();
// If the node is a loop header
if (scope.Contains(node) &&
node.DominanceFrontier.Contains(node) &&
(node != entryPoint || !excludeEntryPoint))
{
HashSet <ControlFlowNode> loopContents = FindLoopContent(scope, node);
// If the first expression is a loop condition
ILBasicBlock basicBlock = (ILBasicBlock)node.UserData;
ILExpression condExpr;
ILLabel trueLabel;
ILLabel falseLabel;
// It has to be just brtrue - any preceding code would introduce goto
if (basicBlock.MatchSingleAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel))
{
ControlFlowNode trueTarget;
labelToCfNode.TryGetValue(trueLabel, out trueTarget);
ControlFlowNode falseTarget;
labelToCfNode.TryGetValue(falseLabel, out falseTarget);
// If one point inside the loop and the other outside
if ((!loopContents.Contains(trueTarget) && loopContents.Contains(falseTarget)) ||
(loopContents.Contains(trueTarget) && !loopContents.Contains(falseTarget)))
{
loopContents.RemoveOrThrow(node);
scope.RemoveOrThrow(node);
// If false means enter the loop
if (loopContents.Contains(falseTarget) || falseTarget == node)
{
// Negate the condition
condExpr = new ILExpression(ILCode.LogicNot, null, condExpr);
ILLabel tmp = trueLabel;
trueLabel = falseLabel;
falseLabel = tmp;
}
ControlFlowNode postLoopTarget;
labelToCfNode.TryGetValue(falseLabel, out postLoopTarget);
if (postLoopTarget != null)
{
// Pull more nodes into the loop
HashSet <ControlFlowNode> postLoopContents = FindDominatedNodes(scope, postLoopTarget);
var pullIn = scope.Except(postLoopContents).Where(n => node.Dominates(n));
loopContents.UnionWith(pullIn);
}
// Use loop to implement the brtrue
basicBlock.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
basicBlock.Body.Add(new ILWhileLoop()
{
Condition = condExpr,
BodyBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, trueLabel),
Body = FindLoops(loopContents, node, false)
}
});
basicBlock.Body.Add(new ILExpression(ILCode.Br, falseLabel));
result.Add(basicBlock);
scope.ExceptWith(loopContents);
}
}
// Fallback method: while(true)
if (scope.Contains(node))
{
result.Add(new ILBasicBlock()
{
Body = new List <ILNode>()
{
new ILLabel()
{
Name = "Loop_" + (nextLabelIndex++)
},
new ILWhileLoop()
{
BodyBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, (ILLabel)basicBlock.Body.First()),
Body = FindLoops(loopContents, node, true)
}
},
},
});
scope.ExceptWith(loopContents);
}
}
// Using the dominator tree should ensure we find the the widest loop first
foreach (var child in node.DominatorTreeChildren)
{
agenda.Enqueue(child);
}
}
// Add whatever is left
foreach (var node in scope)
{
result.Add((ILNode)node.UserData);
}
scope.Clear();
return(result);
}
List <ILNode> FindConditions(HashSet <ControlFlowNode> scope, ControlFlowNode entryNode)
{
List <ILNode> result = new List <ILNode>();
// Do not modify entry data
scope = new HashSet <ControlFlowNode>(scope);
Stack <ControlFlowNode> agenda = new Stack <ControlFlowNode>();
agenda.Push(entryNode);
while (agenda.Count > 0)
{
ControlFlowNode node = agenda.Pop();
// Find a block that represents a simple condition
if (scope.Contains(node))
{
ILBasicBlock block = (ILBasicBlock)node.UserData;
{
// Switch
ILLabel[] caseLabels;
ILExpression switchArg;
ILLabel fallLabel;
if (block.MatchLastAndBr(ILCode.Switch, out caseLabels, out switchArg, out fallLabel))
{
// Replace the switch code with ILSwitch
ILSwitch ilSwitch = new ILSwitch()
{
Condition = switchArg
};
block.Body.RemoveTail(ILCode.Switch, ILCode.Br);
block.Body.Add(ilSwitch);
block.Body.Add(new ILExpression(ILCode.Br, fallLabel));
result.Add(block);
// Remove the item so that it is not picked up as content
scope.RemoveOrThrow(node);
// Find the switch offset
int addValue = 0;
List <ILExpression> subArgs;
if (ilSwitch.Condition.Match(ILCode.Sub, out subArgs) && subArgs[1].Match(ILCode.Ldc_I4, out addValue))
{
ilSwitch.Condition = subArgs[0];
}
// Pull in code of cases
ControlFlowNode fallTarget = null;
labelToCfNode.TryGetValue(fallLabel, out fallTarget);
HashSet <ControlFlowNode> frontiers = new HashSet <ControlFlowNode>();
if (fallTarget != null)
{
frontiers.UnionWith(fallTarget.DominanceFrontier.Except(new [] { fallTarget }));
}
foreach (ILLabel condLabel in caseLabels)
{
ControlFlowNode condTarget = null;
labelToCfNode.TryGetValue(condLabel, out condTarget);
if (condTarget != null)
{
frontiers.UnionWith(condTarget.DominanceFrontier.Except(new [] { condTarget }));
}
}
for (int i = 0; i < caseLabels.Length; i++)
{
ILLabel condLabel = caseLabels[i];
// Find or create new case block
ILSwitch.CaseBlock caseBlock = ilSwitch.CaseBlocks.FirstOrDefault(b => b.EntryGoto.Operand == condLabel);
if (caseBlock == null)
{
caseBlock = new ILSwitch.CaseBlock()
{
Values = new List <int>(),
EntryGoto = new ILExpression(ILCode.Br, condLabel)
};
ilSwitch.CaseBlocks.Add(caseBlock);
ControlFlowNode condTarget = null;
labelToCfNode.TryGetValue(condLabel, out condTarget);
if (condTarget != null && !frontiers.Contains(condTarget))
{
HashSet <ControlFlowNode> content = FindDominatedNodes(scope, condTarget);
scope.ExceptWith(content);
caseBlock.Body.AddRange(FindConditions(content, condTarget));
// Add explicit break which should not be used by default, but the goto removal might decide to use it
caseBlock.Body.Add(new ILBasicBlock()
{
Body =
{
new ILLabel()
{
Name = "SwitchBreak_" + (nextLabelIndex++)
},
new ILExpression(ILCode.LoopOrSwitchBreak, null)
}
});
}
}
caseBlock.Values.Add(i + addValue);
}
// Heuristis to determine if we want to use fallthough as default case
if (fallTarget != null && !frontiers.Contains(fallTarget))
{
HashSet <ControlFlowNode> content = FindDominatedNodes(scope, fallTarget);
if (content.Any())
{
var caseBlock = new ILSwitch.CaseBlock()
{
EntryGoto = new ILExpression(ILCode.Br, fallLabel)
};
ilSwitch.CaseBlocks.Add(caseBlock);
block.Body.RemoveTail(ILCode.Br);
scope.ExceptWith(content);
caseBlock.Body.AddRange(FindConditions(content, fallTarget));
// Add explicit break which should not be used by default, but the goto removal might decide to use it
caseBlock.Body.Add(new ILBasicBlock()
{
Body =
{
new ILLabel()
{
Name = "SwitchBreak_" + (nextLabelIndex++)
},
new ILExpression(ILCode.LoopOrSwitchBreak, null)
}
});
}
}
}
// Two-way branch
ILExpression condExpr;
ILLabel trueLabel;
ILLabel falseLabel;
if (block.MatchLastAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel))
{
// Swap bodies since that seems to be the usual C# order
ILLabel temp = trueLabel;
trueLabel = falseLabel;
falseLabel = temp;
condExpr = new ILExpression(ILCode.LogicNot, null, condExpr);
// Convert the brtrue to ILCondition
ILCondition ilCond = new ILCondition()
{
Condition = condExpr,
TrueBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, trueLabel)
},
FalseBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, falseLabel)
}
};
block.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
block.Body.Add(ilCond);
result.Add(block);
// Remove the item immediately so that it is not picked up as content
scope.RemoveOrThrow(node);
ControlFlowNode trueTarget = null;
labelToCfNode.TryGetValue(trueLabel, out trueTarget);
ControlFlowNode falseTarget = null;
labelToCfNode.TryGetValue(falseLabel, out falseTarget);
// Pull in the conditional code
if (trueTarget != null && HasSingleEdgeEnteringBlock(trueTarget))
{
HashSet <ControlFlowNode> content = FindDominatedNodes(scope, trueTarget);
scope.ExceptWith(content);
ilCond.TrueBlock.Body.AddRange(FindConditions(content, trueTarget));
}
if (falseTarget != null && HasSingleEdgeEnteringBlock(falseTarget))
{
HashSet <ControlFlowNode> content = FindDominatedNodes(scope, falseTarget);
scope.ExceptWith(content);
ilCond.FalseBlock.Body.AddRange(FindConditions(content, falseTarget));
}
}
}
// Add the node now so that we have good ordering
if (scope.Contains(node))
{
result.Add((ILNode)node.UserData);
scope.Remove(node);
}
}
// depth-first traversal of dominator tree
for (int i = node.DominatorTreeChildren.Count - 1; i >= 0; i--)
{
agenda.Push(node.DominatorTreeChildren[i]);
}
}
// Add whatever is left
foreach (var node in scope)
{
result.Add((ILNode)node.UserData);
}
return(result);
}
void DuplicateReturnStatements(ILBlock method)
{
Dictionary <ILLabel, ILNode> nextSibling = new Dictionary <ILLabel, ILNode>();
// Build navigation data
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
for (int i = 0; i < block.Body.Count - 1; i++)
{
ILLabel curr = block.Body[i] as ILLabel;
if (curr != null)
{
nextSibling[curr] = block.Body[i + 1];
}
}
}
// Duplicate returns
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
for (int i = 0; i < block.Body.Count; i++)
{
ILLabel targetLabel;
if (block.Body[i].Match(ILCode.Br, out targetLabel) || block.Body[i].Match(ILCode.Leave, out targetLabel))
{
// Skip extra labels
while (nextSibling.ContainsKey(targetLabel) && nextSibling[targetLabel] is ILLabel)
{
targetLabel = (ILLabel)nextSibling[targetLabel];
}
// Inline return statement
ILNode target;
List <ILExpression> retArgs;
if (nextSibling.TryGetValue(targetLabel, out target))
{
if (target.Match(ILCode.Ret, out retArgs))
{
ILVariable locVar;
object constValue;
if (retArgs.Count == 0)
{
block.Body[i] = new ILExpression(ILCode.Ret, null)
{
Original = new List <ILExpression> {
(ILExpression)block.Body[i]
}
};
}
else if (retArgs.Single().Match(ILCode.Ldloc, out locVar))
{
block.Body[i] = new ILExpression(ILCode.Ret, null, new ILExpression(ILCode.Ldloc, locVar))
{
Original = new List <ILExpression> {
(ILExpression)block.Body[i]
}
};
}
else if (retArgs.Single().Match(ILCode.Ldc_I4, out constValue))
{
block.Body[i] = new ILExpression(ILCode.Ret, null, new ILExpression(ILCode.Ldc_I4, constValue))
{
Original = new List <ILExpression> {
(ILExpression)block.Body[i]
}
};
}
}
}
else
{
if (method.Body.Count > 0 && method.Body.Last() == targetLabel)
{
// It exits the main method - so it is same as return;
block.Body[i] = new ILExpression(ILCode.Ret, null);
}
}
}
}
}
}
/// <summary>
/// Group input into a set of blocks that can be later arbitraliby schufled.
/// The method adds necessary branches to make control flow between blocks
/// explicit and thus order independent.
/// </summary>
void SplitToBasicBlocks(ILBlock block)
{
List <ILNode> basicBlocks = new List <ILNode>();
ILLabel entryLabel = block.Body.FirstOrDefault() as ILLabel ?? new ILLabel()
{
Name = "Block_" + (nextLabelIndex++)
};
ILBasicBlock basicBlock = new ILBasicBlock();
basicBlocks.Add(basicBlock);
basicBlock.Body.Add(entryLabel);
block.EntryGoto = new ILExpression(ILCode.Br, entryLabel);
if (block.Body.Count > 0)
{
if (block.Body[0] != entryLabel)
{
basicBlock.Body.Add(block.Body[0]);
}
for (int i = 1; i < block.Body.Count; i++)
{
ILNode lastNode = block.Body[i - 1];
ILNode currNode = block.Body[i];
// Start a new basic block if necessary
if (currNode is ILLabel ||
currNode is ILTryCatchBlock || // Counts as label
lastNode.IsConditionalControlFlow() ||
lastNode.IsUnconditionalControlFlow())
{
// Try to reuse the label
ILLabel label = currNode as ILLabel ?? new ILLabel()
{
Name = "Block_" + (nextLabelIndex++).ToString()
};
// Terminate the last block
if (!lastNode.IsUnconditionalControlFlow())
{
// Explicit branch from one block to other
basicBlock.Body.Add(new ILExpression(ILCode.Br, label));
}
// Start the new block
basicBlock = new ILBasicBlock();
basicBlocks.Add(basicBlock);
basicBlock.Body.Add(label);
// Add the node to the basic block
if (currNode != label)
{
basicBlock.Body.Add(currNode);
}
}
else
{
basicBlock.Body.Add(currNode);
}
}
}
block.Body = basicBlocks;
return;
}
/// <summary>
/// Removes redundatant Br, Nop, Dup, Pop
/// Ignore arguments of 'leave'
/// </summary>
/// <param name="method"></param>
internal static void RemoveRedundantCode(ILBlock method)
{
Dictionary <ILLabel, int> labelRefCount = new Dictionary <ILLabel, int>();
foreach (ILLabel target in method.GetSelfAndChildrenRecursive <ILExpression>(e => e.IsBranch()).SelectMany(e => e.GetBranchTargets()))
{
labelRefCount[target] = labelRefCount.GetOrDefault(target) + 1;
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
List <ILNode> body = block.Body;
List <ILNode> newBody = new List <ILNode>(body.Count);
for (int i = 0; i < body.Count; i++)
{
ILLabel target;
ILExpression popExpr;
if (body[i].Match(ILCode.Br, out target) && i + 1 < body.Count && body[i + 1] == target)
{
// Ignore the branch
if (labelRefCount[target] == 1)
{
i++; // Ignore the label as well
}
}
else if (body[i].Match(ILCode.Nop))
{
// Ignore nop
}
else if (body[i].Match(ILCode.Pop, out popExpr))
{
ILVariable v;
if (!popExpr.Match(ILCode.Ldloc, out v))
{
throw new Exception("Pop should have just ldloc at this stage");
}
// Best effort to move the ILRange to previous statement
ILVariable prevVar;
ILExpression prevExpr;
if (i - 1 >= 0 && body[i - 1].Match(ILCode.Stloc, out prevVar, out prevExpr) && prevVar == v)
{
prevExpr.ILRanges.AddRange(((ILExpression)body[i]).ILRanges);
}
// Ignore pop
}
else
{
ILLabel label = body[i] as ILLabel;
if (label != null)
{
if (labelRefCount.GetOrDefault(label) > 0)
{
newBody.Add(label);
}
}
else
{
newBody.Add(body[i]);
}
}
}
block.Body = newBody;
}
// Ignore arguments of 'leave'
foreach (ILExpression expr in method.GetSelfAndChildrenRecursive <ILExpression>(e => e.Code == ILCode.Leave))
{
if (expr.Arguments.Any(arg => !arg.Match(ILCode.Ldloc)))
{
throw new Exception("Leave should have just ldloc at this stage");
}
expr.Arguments.Clear();
}
// 'dup' removal
foreach (ILExpression expr in method.GetSelfAndChildrenRecursive <ILExpression>())
{
for (int i = 0; i < expr.Arguments.Count; i++)
{
ILExpression child;
if (expr.Arguments[i].Match(ILCode.Dup, out child))
{
child.ILRanges.AddRange(expr.Arguments[i].ILRanges);
expr.Arguments[i] = child;
}
}
}
}
public static bool MatchLastAndBr <T>(this ILBasicBlock bb, ILCode code, out T operand, out ILExpression arg, out ILLabel brLabel)
{
if (bb.Body.ElementAtOrDefault(bb.Body.Count - 2).Match(code, out operand, out arg) &&
bb.Body.LastOrDefault().Match(ILCode.Br, out brLabel))
{
return(true);
}
operand = default(T);
arg = null;
brLabel = null;
return(false);
}
public static bool MatchSingleAndBr <T>(this ILBasicBlock bb, ILCode code, out T operand, out ILExpression arg, out ILLabel brLabel)
{
if (bb.Body.Count == 3 &&
bb.Body[0] is ILLabel &&
bb.Body[1].Match(code, out operand, out arg) &&
bb.Body[2].Match(ILCode.Br, out brLabel))
{
return(true);
}
operand = default(T);
arg = null;
brLabel = null;
return(false);
}