public Leave(BlockContainer targetContainer, ILInstruction value = null) : base(OpCode.Leave)
{
// Note: ILReader will create Leave instructions with targetContainer==null to represent 'endfinally',
// the targetContainer will then be filled in by BlockBuilder
this.targetContainer = targetContainer;
this.Value = value ?? new Nop();
}
internal static bool GetExecutesFinallyBlock(ILInstruction inst, BlockContainer container)
{
for (; inst != container; inst = inst.Parent)
{
if (inst.Parent is TryFinally && inst.SlotInfo == TryFinally.TryBlockSlot)
{
return(true);
}
}
return(false);
}
public bool MatchLeave(out BlockContainer targetContainer)
{
var inst = this as Leave;
if (inst != null && inst.Value.MatchNop())
{
targetContainer = inst.TargetContainer;
return(true);
}
targetContainer = null;
return(false);
}
public bool MatchLeave(BlockContainer targetContainer, out ILInstruction value)
{
var inst = this as Leave;
if (inst != null && targetContainer == inst.TargetContainer)
{
value = inst.Value;
return(true);
}
value = null;
return(false);
}
private void Visit(BlockContainer container, Block continueTarget)
{
switch (container.Kind)
{
case ContainerKind.Loop:
case ContainerKind.While:
continueTarget = container.EntryPoint;
break;
case ContainerKind.DoWhile:
case ContainerKind.For:
continueTarget = container.Blocks.Last();
break;
}
for (int i = 0; i < container.Blocks.Count; i++)
{
var block = container.Blocks[i];
// Note: it's possible for additional blocks to be appended to the container
// by the Visit() call; but there should be no other changes to the Blocks collection.
Visit(block, continueTarget);
Debug.Assert(container.Blocks[i] == block);
}
}
public bool MatchLeave(BlockContainer targetContainer)
{
var inst = this as Leave;
return(inst != null && inst.TargetContainer == targetContainer && inst.Value.MatchNop());
}
/// <summary>
/// Reduce Nesting in switch statements by replacing break; in cases with the block exit, and extracting the default case
/// Does not affect IL order
/// </summary>
private bool ReduceSwitchNesting(Block parentBlock, BlockContainer switchContainer, ILInstruction exitInst)
{
// break; from outer container cannot be brought inside the switch as the meaning would change
if (exitInst is Leave leave && !leave.IsLeavingFunction)
{
return(false);
}
// find the default section, and ensure it has only one incoming edge
var switchInst = (SwitchInstruction)switchContainer.EntryPoint.Instructions.Single();
var defaultSection = switchInst.Sections.MaxBy(s => s.Labels.Count());
if (!defaultSection.Body.MatchBranch(out var defaultBlock) || defaultBlock.IncomingEdgeCount != 1)
{
return(false);
}
// tally stats for heuristic from each case block
int maxStatements = 0, maxDepth = 0;
foreach (var section in switchInst.Sections)
{
if (section != defaultSection && section.Body.MatchBranch(out var caseBlock) && caseBlock.Parent == switchContainer)
{
UpdateStats(caseBlock, ref maxStatements, ref maxDepth);
}
}
if (!ShouldReduceNesting(defaultBlock, maxStatements, maxDepth))
{
return(false);
}
Debug.Assert(defaultBlock.HasFlag(InstructionFlags.EndPointUnreachable));
// ensure the default case dominator tree has no exits (branches to other cases)
var cfg = new ControlFlowGraph(switchContainer, context.CancellationToken);
var defaultNode = cfg.GetNode(defaultBlock);
var defaultTree = TreeTraversal.PreOrder(defaultNode, n => n.DominatorTreeChildren).ToList();
if (defaultTree.SelectMany(n => n.Successors).Any(n => !defaultNode.Dominates(n)))
{
return(false);
}
if (defaultTree.Count > 1 && !(parentBlock.Parent is BlockContainer))
{
return(false);
}
context.Step("Extract default case of switch", switchContainer);
// replace all break; statements with the exitInst
var leaveInstructions = switchContainer.Descendants.Where(inst => inst.MatchLeave(switchContainer));
foreach (var leaveInst in leaveInstructions.ToArray())
{
leaveInst.ReplaceWith(exitInst.Clone());
}
// replace the default section branch with a break;
defaultSection.Body.ReplaceWith(new Leave(switchContainer));
// remove all default blocks from the switch container
var defaultBlocks = defaultTree.Select(c => (Block)c.UserData).ToList();
foreach (var block in defaultBlocks)
{
switchContainer.Blocks.Remove(block);
}
// replace the parent block exit with the default case instructions
if (parentBlock.Instructions.Last() == exitInst)
{
parentBlock.Instructions.RemoveLast();
}
// Note: even though we don't check that the switchContainer is near the end of the block,
// we know this must be the case because we know "exitInst" is a leave/branch and directly
// follows the switchContainer.
Debug.Assert(parentBlock.Instructions.Last() == switchContainer);
parentBlock.Instructions.AddRange(defaultBlock.Instructions);
// add any additional blocks from the default case to the parent container
Debug.Assert(defaultBlocks[0] == defaultBlock);
if (defaultBlocks.Count > 1)
{
var parentContainer = (BlockContainer)parentBlock.Parent;
int insertAt = parentContainer.Blocks.IndexOf(parentBlock) + 1;
foreach (var block in defaultBlocks.Skip(1))
{
parentContainer.Blocks.Insert(insertAt++, block);
}
}
return(true);
}
void CreateContainerStructure()
{
List <TryCatch> tryCatchList = new List <TryCatch>();
foreach (var eh in body.ExceptionRegions)
{
var tryRange = new Interval(eh.TryOffset, eh.TryOffset + eh.TryLength);
var handlerBlock = new BlockContainer();
handlerBlock.AddILRange(new Interval(eh.HandlerOffset, eh.HandlerOffset + eh.HandlerLength));
handlerBlock.Blocks.Add(new Block());
handlerContainers.Add(handlerBlock.StartILOffset, handlerBlock);
if (eh.Kind == ExceptionRegionKind.Fault || eh.Kind == ExceptionRegionKind.Finally)
{
var tryBlock = new BlockContainer();
tryBlock.AddILRange(tryRange);
if (eh.Kind == ExceptionRegionKind.Finally)
{
tryInstructionList.Add(new TryFinally(tryBlock, handlerBlock).WithILRange(tryRange));
}
else
{
tryInstructionList.Add(new TryFault(tryBlock, handlerBlock).WithILRange(tryRange));
}
continue;
}
//
var tryCatch = tryCatchList.FirstOrDefault(tc => tc.TryBlock.ILRanges.SingleOrDefault() == tryRange);
if (tryCatch == null)
{
var tryBlock = new BlockContainer();
tryBlock.AddILRange(tryRange);
tryCatch = new TryCatch(tryBlock);
tryCatch.AddILRange(tryRange);
tryCatchList.Add(tryCatch);
tryInstructionList.Add(tryCatch);
}
ILInstruction filter;
if (eh.Kind == System.Reflection.Metadata.ExceptionRegionKind.Filter)
{
var filterBlock = new BlockContainer(expectedResultType: StackType.I4);
filterBlock.AddILRange(new Interval(eh.FilterOffset, eh.HandlerOffset));
filterBlock.Blocks.Add(new Block());
handlerContainers.Add(filterBlock.StartILOffset, filterBlock);
filter = filterBlock;
}
else
{
filter = new LdcI4(1);
}
var handler = new TryCatchHandler(filter, handlerBlock, variableByExceptionHandler[eh]);
handler.AddILRange(filter);
handler.AddILRange(handlerBlock);
tryCatch.Handlers.Add(handler);
tryCatch.AddILRange(handler);
}
if (tryInstructionList.Count > 0)
{
tryInstructionList = tryInstructionList.OrderBy(tc => tc.TryBlock.StartILOffset).ThenByDescending(tc => tc.TryBlock.EndILOffset).ToList();
nextTry = tryInstructionList[0];
}
}
public void CreateBlocks(BlockContainer mainContainer, List <ILInstruction> instructions, BitArray incomingBranches, CancellationToken cancellationToken)
{
CreateContainerStructure();
mainContainer.SetILRange(new Interval(0, body.GetCodeSize()));
currentContainer = mainContainer;
if (instructions.Count == 0)
{
currentContainer.Blocks.Add(new Block {
Instructions =
{
new InvalidBranch("Empty body found. Decompiled assembly might be a reference assembly.")
}
});
return;
}
foreach (var inst in instructions)
{
cancellationToken.ThrowIfCancellationRequested();
int start = inst.StartILOffset;
if (currentBlock == null || (incomingBranches[start] && !IsStackAdjustment(inst)))
{
// Finish up the previous block
FinalizeCurrentBlock(start, fallthrough: true);
// Leave nested containers if necessary
while (start >= currentContainer.EndILOffset)
{
currentContainer = containerStack.Pop();
currentBlock = currentContainer.Blocks.Last();
// this container is skipped (i.e. the loop will execute again)
// set ILRange to the last instruction offset inside the block.
if (start >= currentContainer.EndILOffset)
{
Debug.Assert(currentBlock.HasILRange);
currentBlock.AddILRange(new Interval(currentBlock.StartILOffset, start));
}
}
// Enter a handler if necessary
BlockContainer handlerContainer;
if (handlerContainers.TryGetValue(start, out handlerContainer))
{
containerStack.Push(currentContainer);
currentContainer = handlerContainer;
currentBlock = handlerContainer.EntryPoint;
}
else
{
FinalizeCurrentBlock(start, fallthrough: false);
// Create the new block
currentBlock = new Block();
currentContainer.Blocks.Add(currentBlock);
}
currentBlock.SetILRange(new Interval(start, start));
}
while (nextTry != null && start == nextTry.TryBlock.StartILOffset)
{
currentBlock.Instructions.Add(nextTry);
containerStack.Push(currentContainer);
currentContainer = (BlockContainer)nextTry.TryBlock;
currentBlock = new Block();
currentContainer.Blocks.Add(currentBlock);
currentBlock.SetILRange(new Interval(start, start));
nextTry = tryInstructionList.ElementAtOrDefault(++currentTryIndex);
}
currentBlock.Instructions.Add(inst);
if (inst.HasFlag(InstructionFlags.EndPointUnreachable))
{
FinalizeCurrentBlock(inst.EndILOffset, fallthrough: false);
}
else if (!CreateExtendedBlocks && inst.HasFlag(InstructionFlags.MayBranch))
{
FinalizeCurrentBlock(inst.EndILOffset, fallthrough: true);
}
}
FinalizeCurrentBlock(mainContainer.EndILOffset, fallthrough: false);
// Finish up all containers
while (containerStack.Count > 0)
{
currentContainer = containerStack.Pop();
currentBlock = currentContainer.Blocks.Last();
FinalizeCurrentBlock(mainContainer.EndILOffset, fallthrough: false);
}
ConnectBranches(mainContainer, cancellationToken);
}
