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Merge branch 'master' of git://github.com/icsharpcode/ILSpy into Debu…
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…gger
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@eusebiu
eusebiu committed Mar 6, 2011
2 parents a0a4637 + de6d657 commit 45d3767
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Showing 7 changed files with 473 additions and 366 deletions.
432 changes: 197 additions & 235 deletions ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs
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129 changes: 105 additions & 24 deletions ICSharpCode.Decompiler/ILAst/GotoRemoval.cs
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Expand Up @@ -29,9 +29,13 @@ public void RemoveGotos(ILBlock method)
}

// Simplify gotos
foreach (ILExpression gotoExpr in method.GetSelfAndChildrenRecursive<ILExpression>().Where(e => e.Code == ILCode.Br || e.Code == ILCode.Leave)) {
TrySimplifyGoto(gotoExpr);
}
bool modified;
do {
modified = false;
foreach (ILExpression gotoExpr in method.GetSelfAndChildrenRecursive<ILExpression>().Where(e => e.Code == ILCode.Br || e.Code == ILCode.Leave)) {
modified |= TrySimplifyGoto(gotoExpr);
}
} while(modified);

RemoveRedundantCode(method);
}
Expand All @@ -52,44 +56,79 @@ public static void RemoveRedundantCode(ILBlock method)
}
}

// 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].CanFallThough() &&
ilCase.Body[count - 1].Match(ILCode.LoopOrSwitchBreak)) {
ilCase.Body.RemoveAt(count - 1);
}
}
}

var defaultCase = ilSwitch.CaseBlocks.Where(cb => cb.Values == null).SingleOrDefault();
// 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
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);
}
}

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;
}

ILWhileLoop loop = null;
ILNode current = gotoExpr;
while(loop == null && current != null) {
current = parent[current];
loop = current as ILWhileLoop;
}

if (loop != null && target == Exit(loop, new HashSet<ILNode>() { gotoExpr })) {
gotoExpr.Code = ILCode.LoopBreak;
ILNode breakBlock = GetParents(gotoExpr).Where(n => n is ILWhileLoop || n is ILSwitch).FirstOrDefault();
if (breakBlock != null && target == Exit(breakBlock, new HashSet<ILNode>() { gotoExpr })) {
gotoExpr.Code = ILCode.LoopOrSwitchBreak;
gotoExpr.Operand = null;
return true;
}

if (loop != null && target == Enter(loop, new HashSet<ILNode>() { gotoExpr })) {
ILNode continueBlock = GetParents(gotoExpr).Where(n => n is ILWhileLoop).FirstOrDefault();
if (continueBlock != null && target == Enter(continueBlock, new HashSet<ILNode>() { gotoExpr })) {
gotoExpr.Code = ILCode.LoopContinue;
gotoExpr.Operand = null;
return true;
Expand All @@ -99,9 +138,10 @@ bool TrySimplifyGoto(ILExpression gotoExpr)
}

/// <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();
Expand All @@ -117,9 +157,43 @@ ILExpression Enter(ILNode node, HashSet<ILNode> visitedNodes)
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 if (expr.Code == ILCode.LoopOrSwitchBreak) {
ILNode breakBlock = GetParents(expr).Where(n => n is ILWhileLoop || n is ILSwitch).First();
return Exit(breakBlock, new HashSet<ILNode>() { expr });
} else if (expr.Code == ILCode.LoopContinue) {
ILNode continueBlock = GetParents(expr).Where(n => n is ILWhileLoop).First();
return Enter(continueBlock, new HashSet<ILNode>() { expr });
} else {
return expr;
}
Expand Down Expand Up @@ -152,7 +226,7 @@ ILExpression Enter(ILNode node, HashSet<ILNode> visitedNodes)

ILTryCatchBlock tryCatch = node as ILTryCatchBlock;
if (tryCatch != null) {
return Enter(tryCatch.TryBlock, visitedNodes);
return tryCatch;
}

ILSwitch ilSwitch = node as ILSwitch;
Expand All @@ -166,7 +240,7 @@ ILExpression Enter(ILNode node, HashSet<ILNode> visitedNodes)
/// <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();
Expand All @@ -184,13 +258,20 @@ ILExpression Exit(ILNode node, HashSet<ILNode> visitedNodes)
}
}

if (nodeParent is ILCondition ||
nodeParent is ILTryCatchBlock ||
nodeParent is ILSwitch)
{
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);
}

if (nodeParent is ILSwitch) {
return null; // Implicit exit from switch is not allowed
}

if (nodeParent is ILWhileLoop) {
return Enter(nodeParent, visitedNodes);
}
Expand Down

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