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Do not enter try-blocks in the goto removal algorithm

pull/70/head
David Srbecký 15 years ago
parent
commit
f0faaaf8d2
  1. 75
      ICSharpCode.Decompiler/ILAst/GotoRemoval.cs

75
ICSharpCode.Decompiler/ILAst/GotoRemoval.cs

@ -29,9 +29,13 @@ namespace ICSharpCode.Decompiler.ILAst @@ -29,9 +29,13 @@ namespace ICSharpCode.Decompiler.ILAst
}
// Simplify gotos
bool modified;
do {
modified = false;
foreach (ILExpression gotoExpr in method.GetSelfAndChildrenRecursive<ILExpression>().Where(e => e.Code == ILCode.Br || e.Code == ILCode.Leave)) {
TrySimplifyGoto(gotoExpr);
modified |= TrySimplifyGoto(gotoExpr);
}
} while(modified);
RemoveRedundantCode(method);
}
@ -58,20 +62,38 @@ namespace ICSharpCode.Decompiler.ILAst @@ -58,20 +62,38 @@ namespace ICSharpCode.Decompiler.ILAst
}
}
IEnumerable<ILNode> GetParents(ILNode node)
{
ILNode current = node;
while(true) {
current = parent[current];
if (current == null)
yield break;
yield return current;
}
}
bool TrySimplifyGoto(ILExpression gotoExpr)
{
Debug.Assert(gotoExpr.Code == ILCode.Br || gotoExpr.Code == ILCode.Leave);
Debug.Assert(gotoExpr.Prefixes == null);
Debug.Assert(gotoExpr.Operand != null);
ILExpression target = Enter(gotoExpr, new HashSet<ILNode>());
ILNode target = Enter(gotoExpr, new HashSet<ILNode>());
if (target == null)
return false;
// The gotoExper is marked as visited because we do not want to
// walk over node which we plan to modify
// The simulated path always has to start in the same try-block
// in other for the same finally blocks to be executed.
if (target == Exit(gotoExpr, new HashSet<ILNode>() { gotoExpr })) {
gotoExpr.Code = ILCode.Nop;
gotoExpr.Operand = null;
target.ILRanges.AddRange(gotoExpr.ILRanges);
if (target is ILExpression)
((ILExpression)target).ILRanges.AddRange(gotoExpr.ILRanges);
gotoExpr.ILRanges.Clear();
return true;
}
@ -100,9 +122,10 @@ namespace ICSharpCode.Decompiler.ILAst @@ -100,9 +122,10 @@ namespace ICSharpCode.Decompiler.ILAst
}
/// <summary>
/// Get the first expression to be excecuted if the instruction pointer is at the start of the given node
/// 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>
ILExpression Enter(ILNode node, HashSet<ILNode> visitedNodes)
ILNode Enter(ILNode node, HashSet<ILNode> visitedNodes)
{
if (node == null)
throw new ArgumentNullException();
@ -118,7 +141,35 @@ namespace ICSharpCode.Decompiler.ILAst @@ -118,7 +141,35 @@ namespace ICSharpCode.Decompiler.ILAst
ILExpression expr = node as ILExpression;
if (expr != null) {
if (expr.Code == ILCode.Br || expr.Code == ILCode.Leave) {
return Enter((ILLabel)expr.Operand, visitedNodes);
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 {
@ -153,7 +204,7 @@ namespace ICSharpCode.Decompiler.ILAst @@ -153,7 +204,7 @@ namespace ICSharpCode.Decompiler.ILAst
ILTryCatchBlock tryCatch = node as ILTryCatchBlock;
if (tryCatch != null) {
return Enter(tryCatch.TryBlock, visitedNodes);
return tryCatch;
}
ILSwitch ilSwitch = node as ILSwitch;
@ -167,7 +218,7 @@ namespace ICSharpCode.Decompiler.ILAst @@ -167,7 +218,7 @@ namespace ICSharpCode.Decompiler.ILAst
/// <summary>
/// Get the first expression to be excecuted if the instruction pointer is at the end of the given node
/// </summary>
ILExpression Exit(ILNode node, HashSet<ILNode> visitedNodes)
ILNode Exit(ILNode node, HashSet<ILNode> visitedNodes)
{
if (node == null)
throw new ArgumentNullException();
@ -185,7 +236,13 @@ namespace ICSharpCode.Decompiler.ILAst @@ -185,7 +236,13 @@ namespace ICSharpCode.Decompiler.ILAst
}
}
if (nodeParent is ILCondition || nodeParent is ILTryCatchBlock) {
if (nodeParent is ILCondition) {
return Exit(nodeParent, visitedNodes);
}
if (nodeParent is ILTryCatchBlock) {
// Finally blocks are completely ignored.
// We rely on the fact that try blocks can not be entered.
return Exit(nodeParent, visitedNodes);
}

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