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);
}
}
}
static void FixAllIfStatements(ILBlock expr)
{
bool modified = false;
do
{
modified = false;
var list = expr.GetSelfAndChildrenRecursive <ILCondition>().ToList();
foreach (var ifs in list)
{
modified |= SimplifyLogicNot(ref ifs.Condition);
}
} while (modified);
do
{
modified = false;
var list = expr.GetSelfAndChildrenRecursive <ILWhileLoop>().ToList();
foreach (var loop in list)
{
modified |= SimplifyLogicNot(ref loop.Condition);
}
} while (modified);
// return;
do
{
modified = false;
// combine ifstatements to logic ands
List <ILCondition> test = expr.GetSelfAndChildrenRecursive <ILCondition>(x => x.FalseBlock == null && x.TrueBlock.Body.Count == 1 && x.TrueBlock.Body[0] is ILCondition).ToList();
if (test == null || test.Count > 0)
{
modified = true;
}
foreach (var ifs in test)
{
var leftIf = (ifs.TrueBlock.Body[0] as ILCondition);
ifs.TrueBlock = leftIf.TrueBlock;
ifs.Condition = new ILExpression(GMCode.LogicAnd, null, ifs.Condition, leftIf.Condition);
}
}while (modified);
}
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 == GMCode.B))
{
modified |= TrySimplifyGoto(gotoExpr);
}
} while (modified);
RemoveRedundantCode(method);
}
/// <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>
public static void SplitToBasicBlocks(ILBlock block)
{
int nextLabelIndex = 0;
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(GMCode.B, 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 ||
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(GMCode.B, 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;
}
public ILBlock Build(SortedList <int, Instruction> code, bool optimize, GMContext context) // List<string> StringList, List<string> InstanceList = null) //DecompilerContext context)
{
if (code.Count == 0)
{
return(new ILBlock());
}
this.context = context;
_method = code;
this.optimize = optimize;
List <ILNode> ast = BuildPreAst();
ILBlock method = new ILBlock();
method.Body = ast;
if (context.Debug)
{
method.DebugSave("raw_body.txt");
}
betteribttest.Dissasembler.Optimize.RemoveRedundantCode(method);
foreach (var block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
Optimize.SplitToBasicBlocks(block);
}
if (context.Debug)
{
method.DebugSave("basic_blocks.txt");
}
new BuildFullAst(method, context).ProcessAllExpressions(method);
if (context.Debug)
{
method.DebugSave("basic_blocks2.txt");
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
bool modified;
do
{
modified = false;
modified |= block.RunOptimization(new SimpleControlFlow(method, context).PushEnviromentFix);
modified |= block.RunOptimization(new SimpleControlFlow(method, context).SimplifyShortCircuit);
modified |= block.RunOptimization(new SimpleControlFlow(method, context).SimplifyTernaryOperator);
modified |= block.RunOptimization(new SimpleControlFlow(method, context).JoinBasicBlocks);
modified |= block.RunOptimization(Optimize.SimplifyLogicNot);
} while (modified);
}
if (context.Debug)
{
method.DebugSave("before_loop.txt");
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
new LoopsAndConditions().FindLoops(block);
}
if (context.Debug)
{
method.DebugSave("before_conditions.txt");
}
foreach (ILBlock block in method.GetSelfAndChildrenRecursive <ILBlock>())
{
new LoopsAndConditions().FindConditions(block);
}
FlattenBasicBlocks(method);
if (context.Debug)
{
method.DebugSave("before_gotos.txt");
}
Optimize.RemoveRedundantCode(method);
new GotoRemoval().RemoveGotos(method);
Optimize.RemoveRedundantCode(method);
new GotoRemoval().RemoveGotos(method);
GotoRemoval.RemoveRedundantCode(method);
new GotoRemoval().RemoveGotos(method);
if (context.Debug)
{
method.DebugSave("final.cpp");
}
return(method);
}
public static void RemoveRedundantCode(ILBlock method)
{
// Remove dead lables and nops and any popzs left
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(GMCode.BadOp) && !n.Match(GMCode.Popz) && !(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(GMCode.LoopContinue))
{
body.RemoveAt(body.Count - 1);
}
}
// Remove redundant continue
foreach (ILWithStatement with in method.GetSelfAndChildrenRecursive <ILWithStatement>())
{
var body = with.Body.Body;
if (body.Count > 0 && body.Last().Match(GMCode.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(GMCode.LoopOrSwitchBreak))
{
ilCase.Body.RemoveAt(count - 1);
}
}
}
// fix case block
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(GMCode.LoopOrSwitchBreak)))
{
ilSwitch.CaseBlocks.RemoveAll(b => b.Body.Count == 1 && b.Body.Single().Match(GMCode.LoopOrSwitchBreak));
}
}
// Remove redundant return at the end of method
if (method.Body.Count > 0 && (method.Body.Last().Match(GMCode.Ret) || method.Body.Last().Match(GMCode.Exit)) && ((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(GMCode.Ret) || block.Body[i + 1].Match(GMCode.Exit)))
{
modified = true;
block.Body.RemoveAt(i + 1);
}
else
{
i++;
}
}
}
// Remove empty falseBlocks
foreach (ILCondition condition in method.GetSelfAndChildrenRecursive <ILCondition>().Where(x => x.FalseBlock != null && x.FalseBlock.Body.Count == 0))
{
condition.FalseBlock = null;
modified = true;
}
if (modified)
{
// More removals might be possible
new GotoRemoval().RemoveGotos(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 == GMCode.B)
{
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(GMCode.BadOp))
{
current = n as ILTryCatchBlock;
break;
}
}
}
return(null);
}
}
else if (expr.Code == GMCode.BadOp)
{
return(Exit(expr, visitedNodes));
}
else if (expr.Code == GMCode.LoopOrSwitchBreak)
{
ILNode breakBlock = GetParents(expr).First(n => n is ILWhileLoop || n is ILSwitch || n is ILWithStatement);
return(Exit(breakBlock, new HashSet <ILNode>()
{
expr
}));
}
else if (expr.Code == GMCode.LoopContinue)
{
ILNode continueBlock = GetParents(expr).First(n => n is ILWhileLoop || n is ILWithStatement);
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);
}
ILWithStatement with = node as ILWithStatement;
if (with != null)
{
if (with.Enviroment != null)
{
return(with.Enviroment);
}
else
{
return(Enter(with.Body, visitedNodes));
}
}
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());
}