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Duplicate return statements

pull/70/head
David Srbecký 15 years ago
parent
1bc30662b0
commit
effe892409
2 changed files with 70 additions and 96 deletions
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  1. 26
      ICSharpCode.Decompiler/ILAst/GotoRemoval.cs
  2. 140
      ICSharpCode.Decompiler/ILAst/ILAstOptimizer.cs

26
ICSharpCode.Decompiler/ILAst/GotoRemoval.cs
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@ -12,7 +12,7 @@ namespace Decompiler @@ -12,7 +12,7 @@ namespace Decompiler
Dictionary<ILNode, ILNode> parent = new Dictionary<ILNode, ILNode>();
Dictionary<ILNode, ILNode> nextSibling = new Dictionary<ILNode, ILNode>();
public bool RemoveGotos(ILBlock method)
public void RemoveGotos(ILBlock method)
{
// Build the navigation data
parent[method] = null;
@ -30,33 +30,33 @@ namespace Decompiler @@ -30,33 +30,33 @@ namespace Decompiler
}
// Simplify gotos
bool modified = false;
foreach (ILExpression gotoExpr in method.GetSelfAndChildrenRecursive<ILExpression>().Where(e => e.Code == ILCode.Br || e.Code == ILCode.Leave)) {
modified |= TrySimplifyGoto(gotoExpr);
TrySimplifyGoto(gotoExpr);
}
// Remove dead lables and nops
HashSet<ILLabel> liveLabels = new HashSet<ILLabel>(method.GetSelfAndChildrenRecursive<ILExpression>().SelectMany(e => e.GetBranchTargets()));
foreach(ILBlock block in method.GetSelfAndChildrenRecursive<ILBlock>().ToList()) {
int oldBodyCount = block.Body.Count;
block.Body = block.Body.Where(n => !n.Matches(ILCode.Nop) && !(n is ILLabel && !liveLabels.Contains((ILLabel)n))).ToList();
modified |= block.Body.Count < oldBodyCount;
}
RemoveDeadLabels(method);
// Remove redundant continue
foreach(ILWhileLoop loop in method.GetSelfAndChildrenRecursive<ILWhileLoop>()) {
var body = loop.BodyBlock.Body;
if (body.Count > 0 && body.Last().Matches(ILCode.LoopContinue)) {
if (body.Count > 0 && body.Last().Match(ILCode.LoopContinue)) {
body.RemoveAt(body.Count - 1);
}
}
// Remove redundant return
if (method.Body.Count > 0 && method.Body.Last().Matches(ILCode.Ret) && ((ILExpression)method.Body.Last()).Arguments.Count == 0) {
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);
}
return modified;
}
public static void RemoveDeadLabels(ILNode method)
{
HashSet<ILLabel> liveLabels = new HashSet<ILLabel>(method.GetSelfAndChildrenRecursive<ILExpression>().SelectMany(e => e.GetBranchTargets()));
foreach(ILBlock block in method.GetSelfAndChildrenRecursive<ILBlock>().ToList()) {
block.Body = block.Body.Where(n => !n.Match(ILCode.Nop) && !(n is ILLabel && !liveLabels.Contains((ILLabel)n))).ToList();
}
}
bool TrySimplifyGoto(ILExpression gotoExpr)

140
ICSharpCode.Decompiler/ILAst/ILAstOptimizer.cs
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@ -17,6 +17,7 @@ namespace Decompiler.ControlFlow @@ -17,6 +17,7 @@ namespace Decompiler.ControlFlow
FindConditions,
FlattenNestedMovableBlocks,
GotoRemoval,
DuplicateReturns,
HandleArrayInitializers,
TypeInference,
None
@ -62,17 +63,16 @@ namespace Decompiler.ControlFlow @@ -62,17 +63,16 @@ namespace Decompiler.ControlFlow
block.Body = FindConditions(new HashSet<ControlFlowNode>(graph.Nodes.Skip(3)), graph.EntryPoint);
}
// AnalyseLabels(method);
// foreach(ILBlock block in method.GetSelfAndChildrenRecursive<ILBlock>().ToList()) {
// ReturnOptimizations(block);
// }
if (abortBeforeStep == ILAstOptimizationStep.FlattenNestedMovableBlocks) return;
FlattenBasicBlocks(method);
if (abortBeforeStep == ILAstOptimizationStep.GotoRemoval) return;
new GotoRemoval().RemoveGotos(method);
if (abortBeforeStep == ILAstOptimizationStep.DuplicateReturns) return;
DuplicateReturnStatements(method);
GotoRemoval.RemoveDeadLabels(method);
if (abortBeforeStep == ILAstOptimizationStep.HandleArrayInitializers) return;
ArrayInitializers.Transform(method);
@ -325,92 +325,48 @@ namespace Decompiler.ControlFlow @@ -325,92 +325,48 @@ namespace Decompiler.ControlFlow
return false;
}
void ReturnOptimizations(ILBlock block)
{
bool modified;
do {
modified = false;
for (int i = 0; i < block.Body.Count;) {
ILBasicBlock bb = block.Body[i] as ILBasicBlock;
// TODO: Isn't basicblock?
if (bb != null && TryDuplicateFollowingReturn(block.Body, bb)) {
modified = true;
continue;
}
i++;
}
} while(modified);
}
bool TryDuplicateFollowingReturn(List<ILNode> scope, ILBasicBlock head)
void DuplicateReturnStatements(ILBlock method)
{
bool modified = false;
if (head.FallthoughGoto != null) {
ILLabel fallLabel = (ILLabel)head.FallthoughGoto.Operand;
ILLabel dupLabel = null;
if (labelGlobalRefCount[fallLabel] > 1 &&
TryDuplicateReturn(scope, fallLabel, ref dupLabel)) {
labelGlobalRefCount[fallLabel]--;
labelGlobalRefCount[dupLabel] = 1;
head.FallthoughGoto.Operand = dupLabel;
modified = true;
}
}
if (head.Body.Count == 1) {
ILExpression brExpr = head.Body[0] as ILExpression;
if (brExpr != null && brExpr.Operand is ILLabel) {
ILLabel brLabel = (ILLabel)brExpr.Operand;
ILLabel dupLabel = null;
if (labelGlobalRefCount[brLabel] > 1 &&
TryDuplicateReturn(scope, brLabel, ref dupLabel)) {
labelGlobalRefCount[brLabel]--;
labelGlobalRefCount[dupLabel] = 1;
brExpr.Operand = dupLabel;
modified = true;
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];
}
}
}
return modified;
}
bool TryDuplicateReturn(List<ILNode> scope, ILLabel head, ref ILLabel newHead)
{
ILBasicBlock bb;
// TODO: mapping missing?
if (labelToBasicBlock.TryGetValue(head, out bb) && bb.Body.Count == 1 && !scope.Contains(bb)) {
ILExpression retExpr = bb.Body[0] as ILExpression;
if (retExpr != null &&
retExpr.Prefixes == null &&
retExpr.Code == ILCode.Ret)
{
if (retExpr.Arguments.Count == 0) {
newHead = new ILLabel() { Name = "Return_" + (nextLabelIndex++) };
ILBasicBlock newBB = new ILBasicBlock() {
EntryLabel = newHead,
Body = { new ILExpression(ILCode.Ret, null) }
};
scope.Add(newBB);
labelToBasicBlock[newHead] = newBB;
return true;
} else {
ILExpression argExpr = retExpr.Arguments[0] as ILExpression;
if (argExpr != null &&
argExpr.Prefixes == null &&
argExpr.Code == ILCode.Ldloc)
// 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;
ILExpression retExpr;
ILVariable locVar = null;
if (nextSibling.TryGetValue(targetLabel, out target) &&
target.Match(ILCode.Ret, out retExpr) &&
(retExpr.Arguments.Count == 0 || retExpr.Arguments.Single().Match(ILCode.Ldloc, out locVar)))
{
newHead = new ILLabel() { Name = "Return_" + (nextLabelIndex++) };
ILBasicBlock newBB = new ILBasicBlock() {
EntryLabel = newHead,
Body = { new ILExpression(ILCode.Ret, null, new ILExpression(ILCode.Ldloc, argExpr.Operand)) }
};
scope.Add(newBB);
labelToBasicBlock[newHead] = newBB;
return true;
ILExpression dup = new ILExpression(ILCode.Ret, null);
if (locVar != null)
dup.Arguments = new List<ILExpression>() { new ILExpression(ILCode.Ldloc, locVar) };
block.Body[i] = dup;
}
}
}
}
return false;
}
ControlFlowGraph BuildGraph(List<ILNode> nodes, ILLabel entryLabel)
@ -798,10 +754,28 @@ namespace Decompiler.ControlFlow @@ -798,10 +754,28 @@ namespace Decompiler.ControlFlow
public static class ILAstOptimizerExtensionMethods
{
public static bool Matches(this ILNode node, ILCode code)
public static bool Match(this ILNode node, ILCode code)
{
ILExpression expr = node as ILExpression;
return expr != null && expr.Prefixes == null && expr.Code == code;
}
public static bool Match(this ILNode node, ILCode code, out ILExpression expr)
{
expr = node as ILExpression;
return expr != null && expr.Prefixes == null && expr.Code == code;
}
public static bool Match<T>(this ILNode node, ILCode code, out T operand)
{
ILExpression expr = node as ILExpression;
if (expr != null && expr.Prefixes == null && expr.Code == code) {
operand = (T)expr.Operand;
return true;
} else {
operand = default(T);
return false;
}
}
}
}

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