public void RemoveGotos(ILBlock method)
{
// Build the navigation data
parent[method] = null;
foreach (ILNode node in method.EnumerateSelfAndChildrenRecursive()) {
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;
var gotos =
from e in method.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
where e.Code == ILCode.Br || e.Code == ILCode.Leave
select e;
foreach (ILExpression gotoExpr in gotos)
{
modified |= TrySimplifyGoto(gotoExpr);
}
} while(modified);
RemoveRedundantCode(method);
}
public SimpleControlFlow(DecompilerContext context, ILBlock method)
{
this.context = context;
this.typeSystem = context.CurrentMethod.Module.TypeSystem;
var labelTargets =
from e in method.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
where e.IsBranch()
from t in e.GetBranchTargets()
select t;
foreach(ILLabel target in labelTargets) {
labelGlobalRefCount[target] = labelGlobalRefCount.GetOrDefault(target) + 1;
}
var basicBlocks = method.EnumerateSelfAndChildrenRecursive().OfType<ILBasicBlock>();
foreach(ILBasicBlock bb in basicBlocks) {
foreach(ILLabel label in bb.GetChildren().OfType<ILLabel>()) {
labelToBasicBlock[label] = bb;
}
}
}
string GenerateNameForVariable(ILVariable variable, ILBlock methodBody)
{
string proposedName = null;
if (variable.Type == context.CurrentType.Module.TypeSystem.Int32) {
// test whether the variable might be a loop counter
bool isLoopCounter = false;
foreach (ILWhileLoop loop in methodBody.EnumerateSelfAndChildrenRecursive().OfType<ILWhileLoop>())
{
ILExpression expr = loop.Condition;
while (expr != null && expr.Code == ILCode.LogicNot)
expr = expr.Arguments[0];
if (expr != null) {
switch (expr.Code) {
case ILCode.Clt:
case ILCode.Clt_Un:
case ILCode.Cgt:
case ILCode.Cgt_Un:
ILVariable loadVar;
if (expr.Arguments[0].Match(ILCode.Ldloc, out loadVar) && loadVar == variable) {
isLoopCounter = true;
}
break;
}
}
}
if (isLoopCounter) {
// For loop variables, use i,j,k,l,m,n
for (char c = 'i'; c <= maxLoopVariableName; c++) {
if (!typeNames.ContainsKey(c.ToString())) {
proposedName = c.ToString();
break;
}
}
}
}
if (string.IsNullOrEmpty(proposedName)) {
var proposedNameForStores =
(from expr in methodBody.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
where expr.Code == ILCode.Stloc && expr.Operand == variable
select GetNameFromExpression(expr.Arguments.Single())
).Except(fieldNamesInCurrentType).ToList();
if (proposedNameForStores.Count == 1) {
proposedName = proposedNameForStores[0];
}
}
if (string.IsNullOrEmpty(proposedName)) {
var proposedNameForLoads =
(from expr in methodBody.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
from i in Enumerable.Range(0, expr.Arguments.Count)
let arg = expr.Arguments[i]
where arg.Code == ILCode.Ldloc && arg.Operand == variable
select GetNameForArgument(expr, i)
).Except(fieldNamesInCurrentType).ToList();
if (proposedNameForLoads.Count == 1) {
proposedName = proposedNameForLoads[0];
}
}
if (string.IsNullOrEmpty(proposedName)) {
proposedName = GetNameByType(variable.Type);
}
// remove any numbers from the proposed name
int number;
proposedName = SplitName(proposedName, out number);
if (!typeNames.ContainsKey(proposedName)) {
typeNames.Add(proposedName, 0);
}
int count = ++typeNames[proposedName];
if (count > 1) {
return proposedName + count.ToString();
} else {
return proposedName;
}
}
string GenerateNameForVariable(ILVariable variable, ILBlock methodBody)
{
string proposedName = null;
if (variable.Type == context.CurrentType.Module.TypeSystem.Int32)
{
// test whether the variable might be a loop counter
bool isLoopCounter = false;
foreach (ILWhileLoop loop in methodBody.EnumerateSelfAndChildrenRecursive().OfType <ILWhileLoop>())
{
ILExpression expr = loop.Condition;
while (expr != null && expr.Code == ILCode.LogicNot)
{
expr = expr.Arguments[0];
}
if (expr != null)
{
switch (expr.Code)
{
case ILCode.Clt:
case ILCode.Clt_Un:
case ILCode.Cgt:
case ILCode.Cgt_Un:
ILVariable loadVar;
if (expr.Arguments[0].Match(ILCode.Ldloc, out loadVar) && loadVar == variable)
{
isLoopCounter = true;
}
break;
}
}
}
if (isLoopCounter)
{
// For loop variables, use i,j,k,l,m,n
for (char c = 'i'; c <= maxLoopVariableName; c++)
{
if (!typeNames.ContainsKey(c.ToString()))
{
proposedName = c.ToString();
break;
}
}
}
}
if (string.IsNullOrEmpty(proposedName))
{
var proposedNameForStores =
(from expr in methodBody.EnumerateSelfAndChildrenRecursive().OfType <ILExpression>()
where expr.Code == ILCode.Stloc && expr.Operand == variable
select GetNameFromExpression(expr.Arguments.Single())
).Except(fieldNamesInCurrentType).ToList();
if (proposedNameForStores.Count == 1)
{
proposedName = proposedNameForStores[0];
}
}
if (string.IsNullOrEmpty(proposedName))
{
var proposedNameForLoads =
(from expr in methodBody.EnumerateSelfAndChildrenRecursive().OfType <ILExpression>()
from i in Enumerable.Range(0, expr.Arguments.Count)
let arg = expr.Arguments[i]
where arg.Code == ILCode.Ldloc && arg.Operand == variable
select GetNameForArgument(expr, i)
).Except(fieldNamesInCurrentType).ToList();
if (proposedNameForLoads.Count == 1)
{
proposedName = proposedNameForLoads[0];
}
}
if (string.IsNullOrEmpty(proposedName))
{
proposedName = GetNameByType(variable.Type);
}
// remove any numbers from the proposed name
int number;
proposedName = SplitName(proposedName, out number);
if (!typeNames.ContainsKey(proposedName))
{
typeNames.Add(proposedName, 0);
}
int count = ++typeNames[proposedName];
if (count > 1)
{
return(proposedName + count.ToString());
}
else
{
return(proposedName);
}
}
public static void RemoveRedundantCode(ILBlock method)
{
// Remove dead lables and nops
var liveLabels = new HashSet<ILLabel>(
from e in method.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
where e.IsBranch()
from t in e.GetBranchTargets()
select t);
foreach(ILBlock block in method.EnumerateSelfAndChildrenRecursive().OfType<ILBlock>()) {
var liveBlockNodes =
from n in block.Body
where !n.Match(ILCode.Nop) &&
!(n is ILLabel
&& !liveLabels.Contains((ILLabel)n))
select n;
block.Body = liveBlockNodes.ToList();
}
// Remove redundant continue
foreach(ILWhileLoop loop in method.EnumerateSelfAndChildrenRecursive().OfType<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.EnumerateSelfAndChildrenRecursive().OfType<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.EnumerateSelfAndChildrenRecursive().OfType<ILBlock>().ToList()) {
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 BlockStatement CreateMethodBody(IEnumerable<ParameterDeclaration> parameters,
/*Concurrent*/Dictionary<int, IEnumerable<ILVariable>> localVariables)
{
if (methodDef.Body == null) return null;
if (localVariables == null)
throw new ArgumentException("localVariables must be instantiated");
context.VerifyProgress();
ILBlock ilMethod = new ILBlock();
var astBuilder = ILMethodAstBuilder.Build(methodDef, true);
ilMethod.Body = astBuilder.Nodes.ToList();
context.VerifyProgress();
ILAstOptimizer bodyGraph = new ILAstOptimizer();
bodyGraph.Optimize(context, ilMethod);
context.VerifyProgress();
var allVariables =
(from e in ilMethod.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()
let v = e.Operand as ILVariable
where v!=null && !v.IsParameter
select v).Distinct();
Debug.Assert(context.CurrentMethod == methodDef);
NameVariables.AssignNamesToVariables(context, astBuilder.Parameters, allVariables, ilMethod);
if (parameters != null) {
foreach (var pair in (from p in parameters
join v in astBuilder.Parameters on p.Annotation<ParameterDefinition>() equals v.OriginalParameter
select new { p, v.Name }))
{
pair.p.Name = pair.Name;
}
}
context.VerifyProgress();
BlockStatement astBlock = TransformBlock(ilMethod);
CommentStatement.ReplaceAll(astBlock); // convert CommentStatements to Comments
Statement insertionPoint = astBlock.Statements.FirstOrDefault();
foreach (ILVariable v in localVariablesToDefine) {
AstType type;
if (v.Type.ContainsAnonymousType())
type = new SimpleType("var");
else
type = AstBuilder.ConvertType(v.Type);
var newVarDecl = new VariableDeclarationStatement(type, v.Name);
astBlock.Statements.InsertBefore(insertionPoint, newVarDecl);
}
// store the variables - used for debugger
int token = methodDef.MetadataToken.ToInt32();
localVariables[token] = allVariables;
return astBlock;
}
/// <summary>
/// Clears the type inference data on the method.
/// </summary>
public static void Reset(ILBlock method)
{
foreach (ILExpression expr in method.EnumerateSelfAndChildrenRecursive().OfType<ILExpression>()) {
expr.InferredType = null;
expr.ExpectedType = null;
ILVariable v = expr.Operand as ILVariable;
if (v != null && v.IsGenerated)
v.Type = null;
}
}
