/// <summary>
/// Flattens all nested basic blocks, except the the top level 'node' argument
/// </summary>
void FlattenBasicBlocks(ILNode node)
{
ILBlock block = node as ILBlock;
if (block != null)
{
List <ILNode> flatBody = new List <ILNode>();
foreach (ILNode child in block.GetChildren())
{
FlattenBasicBlocks(child);
ILBasicBlock childAsBB = child as ILBasicBlock;
if (childAsBB != null)
{
if (!(childAsBB.Body.FirstOrDefault() is ILLabel))
{
throw new Exception("Basic block has to start with a label. \n" + childAsBB.ToString());
}
if (childAsBB.Body.LastOrDefault() is ILExpression && !childAsBB.Body.LastOrDefault().IsUnconditionalControlFlow())
{
throw new Exception("Basci block has to end with unconditional control flow. \n" + childAsBB.ToString());
}
flatBody.AddRange(childAsBB.GetChildren());
}
else
{
flatBody.Add(child);
}
}
block.EntryGoto = null;
block.Body = flatBody;
}
else if (node is ILExpression)
{
// Optimization - no need to check expressions
}
else if (node != null)
{
// Recursively find all ILBlocks
foreach (ILNode child in node.GetChildren())
{
FlattenBasicBlocks(child);
}
}
}
public bool InlineAllInBlock(ILBlock block)
{
bool modified = false;
List <ILNode> body = block.Body;
if (block is ILTryCatchBlock.CatchBlock && body.Count > 1)
{
ILVariable v = ((ILTryCatchBlock.CatchBlock)block).ExceptionVariable;
if (v != null && v.IsGenerated)
{
if (numLdloca.GetOrDefault(v) == 0 && numStloc.GetOrDefault(v) == 1 && numLdloc.GetOrDefault(v) == 1)
{
ILVariable v2;
ILExpression ldException;
if (body[0].Match(ILCode.Stloc, out v2, out ldException) && ldException.MatchLdloc(v))
{
body.RemoveAt(0);
((ILTryCatchBlock.CatchBlock)block).ExceptionVariable = v2;
modified = true;
}
}
}
}
for (int i = 0; i < body.Count - 1;)
{
ILVariable locVar;
ILExpression expr;
if (body[i].Match(ILCode.Stloc, out locVar, out expr) && InlineOneIfPossible(block.Body, i, aggressive: false))
{
modified = true;
i = Math.Max(0, i - 1); // Go back one step
}
else
{
i++;
}
}
foreach (ILBasicBlock bb in body.OfType <ILBasicBlock>())
{
modified |= InlineAllInBasicBlock(bb);
}
return(modified);
}
/// <summary>
/// Looks at the enumerator's get_Current method and figures out which of the fields holds the current value.
/// </summary>
void AnalyzeCurrentProperty()
{
MethodDefinition getCurrentMethod = enumeratorType.Methods.FirstOrDefault(
m => m.Name.StartsWith("System.Collections.Generic.IEnumerator", StringComparison.Ordinal) &&
m.Name.EndsWith(".get_Current", StringComparison.Ordinal));
ILBlock method = CreateILAst(getCurrentMethod);
if (method.Body.Count == 1)
{
// release builds directly return the current field
ILExpression retExpr;
FieldReference field;
ILExpression ldFromObj;
if (method.Body[0].Match(ILCode.Ret, out retExpr) &&
retExpr.Match(ILCode.Ldfld, out field, out ldFromObj) &&
ldFromObj.MatchThis())
{
currentField = GetFieldDefinition(field);
}
}
else if (method.Body.Count == 2)
{
ILVariable v, v2;
ILExpression stExpr;
FieldReference field;
ILExpression ldFromObj;
ILExpression retExpr;
if (method.Body[0].Match(ILCode.Stloc, out v, out stExpr) &&
stExpr.Match(ILCode.Ldfld, out field, out ldFromObj) &&
ldFromObj.MatchThis() &&
method.Body[1].Match(ILCode.Ret, out retExpr) &&
retExpr.Match(ILCode.Ldloc, out v2) &&
v == v2)
{
currentField = GetFieldDefinition(field);
}
}
if (currentField == null)
{
throw new SymbolicAnalysisFailedException();
}
}
void ConstructExceptionTable()
{
disposeMethod = enumeratorType.Methods.FirstOrDefault(m => m.Name == "System.IDisposable.Dispose");
ILBlock ilMethod = CreateILAst(disposeMethod);
var rangeAnalysis = new StateRangeAnalysis(ilMethod.Body[0], StateRangeAnalysisMode.IteratorDispose, stateField);
rangeAnalysis.AssignStateRanges(ilMethod.Body, ilMethod.Body.Count);
finallyMethodToStateInterval = rangeAnalysis.finallyMethodToStateInterval;
// Now look at the finally blocks:
foreach (var tryFinally in ilMethod.GetSelfAndChildrenRecursive <ILTryCatchBlock>())
{
Interval interval = rangeAnalysis.ranges[tryFinally.TryBlock.Body[0]].ToEnclosingInterval();
var finallyBody = tryFinally.FinallyBlock.Body;
if (finallyBody.Count != 2)
{
throw new SymbolicAnalysisFailedException();
}
ILExpression call = finallyBody[0] as ILExpression;
if (call == null || call.Code != ILCode.Call || call.Arguments.Count != 1)
{
throw new SymbolicAnalysisFailedException();
}
if (!call.Arguments[0].MatchThis())
{
throw new SymbolicAnalysisFailedException();
}
if (!finallyBody[1].Match(ILCode.Endfinally))
{
throw new SymbolicAnalysisFailedException();
}
MethodDefinition mdef = GetMethodDefinition(call.Operand as MethodReference);
if (mdef == null || finallyMethodToStateInterval.ContainsKey(mdef))
{
throw new SymbolicAnalysisFailedException();
}
finallyMethodToStateInterval.Add(mdef, interval);
}
rangeAnalysis = null;
}
public static void Run(DecompilerContext context, ILBlock method)
{
if (!context.Settings.YieldReturn)
{
return; // abort if enumerator decompilation is disabled
}
var yrd = new YieldReturnDecompiler();
yrd.context = context;
if (!yrd.MatchEnumeratorCreationPattern(method))
{
return;
}
yrd.enumeratorType = yrd.enumeratorCtor.DeclaringType;
#if DEBUG
if (Debugger.IsAttached)
{
yrd.Run();
}
else
{
#endif
try {
yrd.Run();
} catch (SymbolicAnalysisFailedException) {
return;
}
#if DEBUG
}
#endif
method.Body.Clear();
method.EntryGoto = null;
method.Body.AddRange(yrd.newBody);
// Repeat the inlining/copy propagation optimization because the conversion of field access
// to local variables can open up additional inlining possibilities.
ILInlining inlining = new ILInlining(method);
inlining.InlineAllVariables();
inlining.CopyPropagation();
}
public void RemoveGotos(ILBlock method)
{
// Build the navigation data
parent[method] = null;
foreach (ILNode node in method.GetSelfAndChildrenRecursive <ILNode>())
{
ILNode previousChild = null;
foreach (ILNode child in node.GetChildren())
{
if (parent.ContainsKey(child))
{
throw new Exception("The following expression is linked from several locations: " + child.ToString());
}
parent[child] = node;
if (previousChild != null)
{
nextSibling[previousChild] = child;
}
previousChild = child;
}
if (previousChild != null)
{
nextSibling[previousChild] = null;
}
}
// Simplify gotos
bool modified;
do
{
modified = false;
foreach (ILExpression gotoExpr in method.GetSelfAndChildrenRecursive <ILExpression>(e => e.Code == ILCode.Br || e.Code == ILCode.Leave))
{
modified |= TrySimplifyGoto(gotoExpr);
}
} while(modified);
RemoveRedundantCode(method);
}
/// <summary>
/// Replace endfinally with jump to the end of the finally block
/// </summary>
void RemoveEndFinally(ILBlock method)
{
// Go thought the list in reverse so that we do the nested blocks first
foreach (var tryCatch in method.GetSelfAndChildrenRecursive <ILTryCatchBlock>(tc => tc.FinallyBlock != null).Reverse())
{
ILLabel label = new ILLabel()
{
Name = "EndFinally_" + nextLabelIndex++
};
tryCatch.FinallyBlock.Body.Add(label);
foreach (var block in tryCatch.FinallyBlock.GetSelfAndChildrenRecursive <ILBlock>())
{
for (int i = 0; i < block.Body.Count; i++)
{
if (block.Body[i].Match(ILCode.Endfinally))
{
block.Body[i] = new ILExpression(ILCode.Br, label).WithILRanges(((ILExpression)block.Body[i]).ILRanges);
}
}
}
}
}
void RecombineVariables(ILBlock method)
{
// Recombine variables that were split when the ILAst was created
// This ensures that a single IL variable is a single C# variable (gets assigned only one name)
// The DeclareVariables transformation might then split up the C# variable again if it is used indendently in two separate scopes.
Dictionary <VariableDefinition, ILVariable> dict = new Dictionary <VariableDefinition, ILVariable>();
ReplaceVariables(
method,
delegate(ILVariable v) {
if (v.OriginalVariable == null)
{
return(v);
}
ILVariable combinedVariable;
if (!dict.TryGetValue(v.OriginalVariable, out combinedVariable))
{
dict.Add(v.OriginalVariable, v);
combinedVariable = v;
}
return(combinedVariable);
});
}
/// <summary>
/// Looks at the enumerator's ctor and figures out which of the fields holds the state.
/// </summary>
void AnalyzeCtor()
{
ILBlock method = CreateILAst(enumeratorCtor);
foreach (ILNode node in method.Body)
{
FieldReference field;
ILExpression instExpr;
ILExpression stExpr;
ILVariable arg;
if (node.Match(ILCode.Stfld, out field, out instExpr, out stExpr) &&
instExpr.MatchThis() &&
stExpr.Match(ILCode.Ldloc, out arg) &&
arg.IsParameter && arg.OriginalParameter.Index == 0)
{
stateField = GetFieldDefinition(field);
}
}
if (stateField == null)
{
throw new SymbolicAnalysisFailedException();
}
}
public static void RunStep1(DecompilerContext context, ILBlock method)
{
if (!context.Settings.AsyncAwait)
{
return; // abort if async decompilation is disabled
}
var yrd = new AsyncDecompiler();
yrd.context = context;
if (!yrd.MatchTaskCreationPattern(method))
{
return;
}
#if DEBUG
if (Debugger.IsAttached)
{
yrd.Run();
}
else
{
#endif
try {
yrd.Run();
} catch (SymbolicAnalysisFailedException) {
return;
}
#if DEBUG
}
#endif
context.CurrentMethodIsAsync = true;
method.Body.Clear();
method.EntryGoto = null;
method.Body.AddRange(yrd.newTopLevelBody);
ILAstOptimizer.RemoveRedundantCode(method);
}
void AnalyzeStateMachine(ILBlock block)
{
var body = block.Body;
if (body.Count == 0)
{
throw new SymbolicAnalysisFailedException();
}
if (DetectDoFinallyBodies(body))
{
body.RemoveAt(0);
if (body.Count == 0)
{
throw new SymbolicAnalysisFailedException();
}
}
StateRangeAnalysis rangeAnalysis = new StateRangeAnalysis(body[0], StateRangeAnalysisMode.AsyncMoveNext, stateField);
int bodyLength = block.Body.Count;
int pos = rangeAnalysis.AssignStateRanges(body, bodyLength);
rangeAnalysis.EnsureLabelAtPos(body, ref pos, ref bodyLength);
var labelStateRangeMapping = rangeAnalysis.CreateLabelRangeMapping(body, pos, bodyLength);
newTopLevelBody = ConvertBody(body, pos, bodyLength, labelStateRangeMapping);
newTopLevelBody.Insert(0, MakeGoTo(labelStateRangeMapping, initialState));
newTopLevelBody.Add(setResultAndExitLabel);
if (methodType == AsyncMethodType.TaskOfT)
{
newTopLevelBody.Add(new ILExpression(ILCode.Ret, null, resultExpr));
}
else
{
newTopLevelBody.Add(new ILExpression(ILCode.Ret, null));
}
}
ILBlock ConvertFinallyBlock(MethodDefinition finallyMethod)
{
ILBlock block = CreateILAst(finallyMethod);
// Get rid of assignment to state
FieldReference stfld;
List <ILExpression> args;
if (block.Body.Count > 0 && block.Body[0].Match(ILCode.Stfld, out stfld, out args))
{
if (GetFieldDefinition(stfld) == stateField && args[0].MatchThis())
{
block.Body.RemoveAt(0);
}
}
// Convert ret to endfinally
foreach (ILExpression expr in block.GetSelfAndChildrenRecursive <ILExpression>())
{
if (expr.Code == ILCode.Ret)
{
expr.Code = ILCode.Endfinally;
}
}
return(block);
}
void ResolveIEnumerableIEnumeratorFieldMapping()
{
MethodDefinition getEnumeratorMethod = enumeratorType.Methods.FirstOrDefault(
m => m.Name.StartsWith("System.Collections.Generic.IEnumerable", StringComparison.Ordinal) &&
m.Name.EndsWith(".GetEnumerator", StringComparison.Ordinal));
if (getEnumeratorMethod == null)
{
return; // no mappings (maybe it's just an IEnumerator implementation?)
}
ILBlock method = CreateILAst(getEnumeratorMethod);
foreach (ILNode node in method.Body)
{
FieldReference stField;
ILExpression stToObj;
ILExpression stExpr;
FieldReference ldField;
ILExpression ldFromObj;
if (node.Match(ILCode.Stfld, out stField, out stToObj, out stExpr) &&
stExpr.Match(ILCode.Ldfld, out ldField, out ldFromObj) &&
ldFromObj.MatchThis())
{
FieldDefinition storedField = GetFieldDefinition(stField);
FieldDefinition loadedField = GetFieldDefinition(ldField);
if (storedField != null && loadedField != null)
{
ILVariable mappedParameter;
if (fieldToParameterMap.TryGetValue(loadedField, out mappedParameter))
{
fieldToParameterMap[storedField] = mappedParameter;
}
}
}
}
}
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);
}
/// <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;
}
}
}
}
/// <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;
}
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);
}
}
}
}
}
}
bool MatchEnumeratorCreationPattern(ILBlock method)
{
if (method.Body.Count == 0)
{
return(false);
}
ILExpression newObj;
if (method.Body.Count == 1)
{
// ret(newobj(...))
if (method.Body[0].Match(ILCode.Ret, out newObj))
{
return(MatchEnumeratorCreationNewObj(newObj, out enumeratorCtor));
}
else
{
return(false);
}
}
// stloc(var_1, newobj(..)
ILVariable var1;
if (!method.Body[0].Match(ILCode.Stloc, out var1, out newObj))
{
return(false);
}
if (!MatchEnumeratorCreationNewObj(newObj, out enumeratorCtor))
{
return(false);
}
int i;
for (i = 1; i < method.Body.Count; i++)
{
// stfld(..., ldloc(var_1), ldloc(parameter))
FieldReference storedField;
ILExpression ldloc, loadParameter;
if (!method.Body[i].Match(ILCode.Stfld, out storedField, out ldloc, out loadParameter))
{
break;
}
ILVariable loadedVar, loadedArg;
if (!ldloc.Match(ILCode.Ldloc, out loadedVar) || !loadParameter.Match(ILCode.Ldloc, out loadedArg))
{
return(false);
}
storedField = GetFieldDefinition(storedField);
if (loadedVar != var1 || storedField == null || !loadedArg.IsParameter)
{
return(false);
}
fieldToParameterMap[(FieldDefinition)storedField] = loadedArg;
}
ILVariable var2;
ILExpression ldlocForStloc2;
if (i < method.Body.Count && method.Body[i].Match(ILCode.Stloc, out var2, out ldlocForStloc2))
{
// stloc(var_2, ldloc(var_1))
if (ldlocForStloc2.Code != ILCode.Ldloc || ldlocForStloc2.Operand != var1)
{
return(false);
}
i++;
}
else
{
// the compiler might skip the above instruction in release builds; in that case, it directly returns stloc.Operand
var2 = var1;
}
ILExpression retArg;
if (i < method.Body.Count && method.Body[i].Match(ILCode.Ret, out retArg))
{
// ret(ldloc(var_2))
if (retArg.Code == ILCode.Ldloc && retArg.Operand == var2)
{
return(true);
}
}
return(false);
}
public static void RemoveRedundantCode(ILBlock method)
{
// Remove dead lables and nops
HashSet <ILLabel> liveLabels = new HashSet <ILLabel>(method.GetSelfAndChildrenRecursive <ILExpression>(e => e.IsBranch()).SelectMany(e => e.GetBranchTargets()));
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
block.Body = block.Body.Where(n => !n.Match(ILCode.Nop) && !(n is ILLabel && !liveLabels.Contains((ILLabel)n))).ToList();
}
// Remove redundant continue
foreach (ILWhileLoop loop in method.GetSelfAndChildrenRecursive <ILWhileLoop>())
{
var body = loop.BodyBlock.Body;
if (body.Count > 0 && body.Last().Match(ILCode.LoopContinue))
{
body.RemoveAt(body.Count - 1);
}
}
// Remove redundant break at the end of case
// Remove redundant case blocks altogether
foreach (ILSwitch ilSwitch in method.GetSelfAndChildrenRecursive <ILSwitch>())
{
foreach (ILBlock ilCase in ilSwitch.CaseBlocks)
{
Debug.Assert(ilCase.EntryGoto == null);
int count = ilCase.Body.Count;
if (count >= 2)
{
if (ilCase.Body[count - 2].IsUnconditionalControlFlow() &&
ilCase.Body[count - 1].Match(ILCode.LoopOrSwitchBreak))
{
ilCase.Body.RemoveAt(count - 1);
}
}
}
var defaultCase = ilSwitch.CaseBlocks.SingleOrDefault(cb => cb.Values == null);
// If there is no default block, remove empty case blocks
if (defaultCase == null || (defaultCase.Body.Count == 1 && defaultCase.Body.Single().Match(ILCode.LoopOrSwitchBreak)))
{
ilSwitch.CaseBlocks.RemoveAll(b => b.Body.Count == 1 && b.Body.Single().Match(ILCode.LoopOrSwitchBreak));
}
}
// Remove redundant return at the end of method
if (method.Body.Count > 0 && method.Body.Last().Match(ILCode.Ret) && ((ILExpression)method.Body.Last()).Arguments.Count == 0)
{
method.Body.RemoveAt(method.Body.Count - 1);
}
// Remove unreachable return statements
bool modified = false;
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
for (int i = 0; i < block.Body.Count - 1;)
{
if (block.Body[i].IsUnconditionalControlFlow() && block.Body[i + 1].Match(ILCode.Ret))
{
modified = true;
block.Body.RemoveAt(i + 1);
}
else
{
i++;
}
}
}
if (modified)
{
// More removals might be possible
new GotoRemoval().RemoveGotos(method);
}
}
public void Optimize(DecompilerContext context, ILBlock method, ILAstOptimizationStep abortBeforeStep = ILAstOptimizationStep.None)
{
this.context = context;
this.typeSystem = context.CurrentMethod.Module.TypeSystem;
this.method = method;
if (abortBeforeStep == ILAstOptimizationStep.RemoveRedundantCode)
{
return;
}
RemoveRedundantCode(method);
if (abortBeforeStep == ILAstOptimizationStep.ReduceBranchInstructionSet)
{
return;
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
ReduceBranchInstructionSet(block);
}
// ReduceBranchInstructionSet runs before inlining because the non-aggressive inlining heuristic
// looks at which type of instruction consumes the inlined variable.
if (abortBeforeStep == ILAstOptimizationStep.InlineVariables)
{
return;
}
// Works better after simple goto removal because of the following debug pattern: stloc X; br Next; Next:; ldloc X
ILInlining inlining1 = new ILInlining(method);
inlining1.InlineAllVariables();
if (abortBeforeStep == ILAstOptimizationStep.CopyPropagation)
{
return;
}
inlining1.CopyPropagation();
if (abortBeforeStep == ILAstOptimizationStep.YieldReturn)
{
return;
}
YieldReturnDecompiler.Run(context, method);
AsyncDecompiler.RunStep1(context, method);
if (abortBeforeStep == ILAstOptimizationStep.AsyncAwait)
{
return;
}
AsyncDecompiler.RunStep2(context, method);
if (abortBeforeStep == ILAstOptimizationStep.PropertyAccessInstructions)
{
return;
}
IntroducePropertyAccessInstructions(method);
if (abortBeforeStep == ILAstOptimizationStep.SplitToMovableBlocks)
{
return;
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
SplitToBasicBlocks(block);
}
if (abortBeforeStep == ILAstOptimizationStep.TypeInference)
{
return;
}
// Types are needed for the ternary operator optimization
TypeAnalysis.Run(context, method);
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
bool modified;
do
{
modified = false;
if (abortBeforeStep == ILAstOptimizationStep.SimplifyShortCircuit)
{
return;
}
modified |= block.RunOptimization(new SimpleControlFlow(context, method).SimplifyShortCircuit);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyTernaryOperator)
{
return;
}
modified |= block.RunOptimization(new SimpleControlFlow(context, method).SimplifyTernaryOperator);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyNullCoalescing)
{
return;
}
modified |= block.RunOptimization(new SimpleControlFlow(context, method).SimplifyNullCoalescing);
if (abortBeforeStep == ILAstOptimizationStep.JoinBasicBlocks)
{
return;
}
modified |= block.RunOptimization(new SimpleControlFlow(context, method).JoinBasicBlocks);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyLogicNot)
{
return;
}
modified |= block.RunOptimization(SimplifyLogicNot);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyShiftOperators)
{
return;
}
modified |= block.RunOptimization(SimplifyShiftOperators);
if (abortBeforeStep == ILAstOptimizationStep.TypeConversionSimplifications)
{
return;
}
modified |= block.RunOptimization(TypeConversionSimplifications);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyLdObjAndStObj)
{
return;
}
modified |= block.RunOptimization(SimplifyLdObjAndStObj);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyCustomShortCircuit)
{
return;
}
modified |= block.RunOptimization(new SimpleControlFlow(context, method).SimplifyCustomShortCircuit);
if (abortBeforeStep == ILAstOptimizationStep.SimplifyLiftedOperators)
{
return;
}
modified |= block.RunOptimization(SimplifyLiftedOperators);
if (abortBeforeStep == ILAstOptimizationStep.TransformArrayInitializers)
{
return;
}
modified |= block.RunOptimization(TransformArrayInitializers);
if (abortBeforeStep == ILAstOptimizationStep.TransformMultidimensionalArrayInitializers)
{
return;
}
modified |= block.RunOptimization(TransformMultidimensionalArrayInitializers);
if (abortBeforeStep == ILAstOptimizationStep.TransformObjectInitializers)
{
return;
}
modified |= block.RunOptimization(TransformObjectInitializers);
if (abortBeforeStep == ILAstOptimizationStep.MakeAssignmentExpression)
{
return;
}
if (context.Settings.MakeAssignmentExpressions)
{
modified |= block.RunOptimization(MakeAssignmentExpression);
}
modified |= block.RunOptimization(MakeCompoundAssignments);
if (abortBeforeStep == ILAstOptimizationStep.IntroducePostIncrement)
{
return;
}
if (context.Settings.IntroduceIncrementAndDecrement)
{
modified |= block.RunOptimization(IntroducePostIncrement);
}
if (abortBeforeStep == ILAstOptimizationStep.InlineExpressionTreeParameterDeclarations)
{
return;
}
if (context.Settings.ExpressionTrees)
{
modified |= block.RunOptimization(InlineExpressionTreeParameterDeclarations);
}
if (abortBeforeStep == ILAstOptimizationStep.InlineVariables2)
{
return;
}
modified |= new ILInlining(method).InlineAllInBlock(block);
new ILInlining(method).CopyPropagation();
} while(modified);
}
if (abortBeforeStep == ILAstOptimizationStep.FindLoops)
{
return;
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
new LoopsAndConditions(context).FindLoops(block);
}
if (abortBeforeStep == ILAstOptimizationStep.FindConditions)
{
return;
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
new LoopsAndConditions(context).FindConditions(block);
}
if (abortBeforeStep == ILAstOptimizationStep.FlattenNestedMovableBlocks)
{
return;
}
FlattenBasicBlocks(method);
if (abortBeforeStep == ILAstOptimizationStep.RemoveEndFinally)
{
return;
}
RemoveEndFinally(method);
if (abortBeforeStep == ILAstOptimizationStep.RemoveRedundantCode2)
{
return;
}
RemoveRedundantCode(method);
if (abortBeforeStep == ILAstOptimizationStep.GotoRemoval)
{
return;
}
new GotoRemoval().RemoveGotos(method);
if (abortBeforeStep == ILAstOptimizationStep.DuplicateReturns)
{
return;
}
DuplicateReturnStatements(method);
if (abortBeforeStep == ILAstOptimizationStep.GotoRemoval2)
{
return;
}
new GotoRemoval().RemoveGotos(method);
if (abortBeforeStep == ILAstOptimizationStep.ReduceIfNesting)
{
return;
}
ReduceIfNesting(method);
if (abortBeforeStep == ILAstOptimizationStep.InlineVariables3)
{
return;
}
// The 2nd inlining pass is necessary because DuplicateReturns and the introduction of ternary operators
// open up additional inlining possibilities.
new ILInlining(method).InlineAllVariables();
if (abortBeforeStep == ILAstOptimizationStep.CachedDelegateInitialization)
{
return;
}
if (context.Settings.AnonymousMethods)
{
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
for (int i = 0; i < block.Body.Count; i++)
{
// TODO: Move before loops
CachedDelegateInitializationWithField(block, ref i);
CachedDelegateInitializationWithLocal(block, ref i);
}
}
}
if (abortBeforeStep == ILAstOptimizationStep.IntroduceFixedStatements)
{
return;
}
// we need post-order traversal, not pre-order, for "fixed" to work correctly
foreach (ILBlock block in TreeTraversal.PostOrder <ILNode>(method, n => n.GetChildren()).OfType <ILBlock>())
{
for (int i = block.Body.Count - 1; i >= 0; i--)
{
// TODO: Move before loops
if (i < block.Body.Count)
{
IntroduceFixedStatements(block.Body, i);
}
}
}
if (abortBeforeStep == ILAstOptimizationStep.RecombineVariables)
{
return;
}
RecombineVariables(method);
if (abortBeforeStep == ILAstOptimizationStep.TypeInference2)
{
return;
}
TypeAnalysis.Reset(method);
TypeAnalysis.Run(context, method);
if (abortBeforeStep == ILAstOptimizationStep.RemoveRedundantCode3)
{
return;
}
GotoRemoval.RemoveRedundantCode(method);
// ReportUnassignedILRanges(method);
}
/// <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());
}
public ILInlining(ILBlock method)
{
this.method = method;
AnalyzeMethod();
}
bool MatchTaskCreationPattern(ILBlock method)
{
if (method.Body.Count < 5)
{
return(false);
}
// Check the second-to-last instruction (the start call) first, as we can get the most information from that
MethodReference startMethod;
ILExpression loadStartTarget, loadStartArgument;
// call(AsyncTaskMethodBuilder::Start, ldloca(builder), ldloca(stateMachine))
if (!method.Body[method.Body.Count - 2].Match(ILCode.Call, out startMethod, out loadStartTarget, out loadStartArgument))
{
return(false);
}
if (startMethod.Name != "Start" || startMethod.DeclaringType == null || startMethod.DeclaringType.Namespace != "System.Runtime.CompilerServices")
{
return(false);
}
switch (startMethod.DeclaringType.Name)
{
case "AsyncTaskMethodBuilder`1":
methodType = AsyncMethodType.TaskOfT;
break;
case "AsyncTaskMethodBuilder":
methodType = AsyncMethodType.Task;
break;
case "AsyncVoidMethodBuilder":
methodType = AsyncMethodType.Void;
break;
default:
return(false);
}
ILVariable stateMachineVar, builderVar;
if (!loadStartTarget.Match(ILCode.Ldloca, out builderVar))
{
return(false);
}
if (!loadStartArgument.Match(ILCode.Ldloca, out stateMachineVar))
{
return(false);
}
stateMachineStruct = stateMachineVar.Type.ResolveWithinSameModule();
if (stateMachineStruct == null || !stateMachineStruct.IsValueType)
{
return(false);
}
moveNextMethod = stateMachineStruct.Methods.FirstOrDefault(f => f.Name == "MoveNext");
if (moveNextMethod == null)
{
return(false);
}
// Check third-to-last instruction (copy of builder):
// stloc(builder, ldfld(StateMachine::<>t__builder, ldloca(stateMachine)))
ILExpression loadBuilderExpr;
if (!method.Body[method.Body.Count - 3].MatchStloc(builderVar, out loadBuilderExpr))
{
return(false);
}
FieldReference builderFieldRef;
ILExpression loadStateMachineForBuilderExpr;
if (!loadBuilderExpr.Match(ILCode.Ldfld, out builderFieldRef, out loadStateMachineForBuilderExpr))
{
return(false);
}
if (!loadStateMachineForBuilderExpr.MatchLdloca(stateMachineVar))
{
return(false);
}
builderField = builderFieldRef.ResolveWithinSameModule();
if (builderField == null)
{
return(false);
}
// Check the last instruction (ret)
if (methodType == AsyncMethodType.Void)
{
if (!method.Body[method.Body.Count - 1].Match(ILCode.Ret))
{
return(false);
}
}
else
{
// ret(call(AsyncTaskMethodBuilder::get_Task, ldflda(StateMachine::<>t__builder, ldloca(stateMachine))))
ILExpression returnValue;
if (!method.Body[method.Body.Count - 1].Match(ILCode.Ret, out returnValue))
{
return(false);
}
MethodReference getTaskMethod;
ILExpression builderExpr;
if (!returnValue.Match(ILCode.Call, out getTaskMethod, out builderExpr))
{
return(false);
}
ILExpression loadStateMachineForBuilderExpr2;
FieldReference builderField2;
if (!builderExpr.Match(ILCode.Ldflda, out builderField2, out loadStateMachineForBuilderExpr2))
{
return(false);
}
if (builderField2.ResolveWithinSameModule() != builderField || !loadStateMachineForBuilderExpr2.MatchLdloca(stateMachineVar))
{
return(false);
}
}
// Check the last field assignment - this should be the state field
ILExpression initialStateExpr;
if (!MatchStFld(method.Body[method.Body.Count - 4], stateMachineVar, out stateField, out initialStateExpr))
{
return(false);
}
if (!initialStateExpr.Match(ILCode.Ldc_I4, out initialState))
{
return(false);
}
if (initialState != -1)
{
return(false);
}
// Check the second-to-last field assignment - this should be the builder field
FieldDefinition builderField3;
ILExpression builderInitialization;
if (!MatchStFld(method.Body[method.Body.Count - 5], stateMachineVar, out builderField3, out builderInitialization))
{
return(false);
}
MethodReference createMethodRef;
if (builderField3 != builderField || !builderInitialization.Match(ILCode.Call, out createMethodRef))
{
return(false);
}
if (createMethodRef.Name != "Create")
{
return(false);
}
for (int i = 0; i < method.Body.Count - 5; i++)
{
FieldDefinition field;
ILExpression fieldInit;
if (!MatchStFld(method.Body[i], stateMachineVar, out field, out fieldInit))
{
return(false);
}
ILVariable v;
if (!fieldInit.Match(ILCode.Ldloc, out v))
{
return(false);
}
if (!v.IsParameter)
{
return(false);
}
fieldToParameterMap[field] = v;
}
return(true);
}
