public override ScopeInfo OpenScope(
ScopeType scopeType,
Microsoft.Cci.ITypeReference exceptionType,
ExceptionHandlerScope currentExceptionHandler
)
{
Debug.Assert(
((_handlers.Count == 0) && (scopeType == ScopeType.Try)) ||
(
(_handlers.Count > 0) &&
(
(scopeType == ScopeType.Catch) ||
(scopeType == ScopeType.Filter) ||
(scopeType == ScopeType.Finally) ||
(scopeType == ScopeType.Fault)
)
)
);
Debug.Assert(currentExceptionHandler == _containingHandler);
var handler = new ExceptionHandlerScope(this, scopeType, exceptionType);
_handlers.Add(handler);
return(handler);
}
public BasicBlockWithHandlerScope(
ILBuilder builder,
ExceptionHandlerScope enclosingHandler
) : base(builder)
{
this.enclosingHandler = enclosingHandler;
}
private bool ForwardLabelsAllowLeaving()
{
bool madeChanges = false;
SmallDictionary <object, LabelInfo> .KeyCollection labels = _labelInfos.Keys;
bool done;
do
{
done = true;
foreach (object label in labels)
{
LabelInfo labelInfo = _labelInfos[label];
if (labelInfo.targetOfConditionalBranches)
{
// only unconditional labels can be forwarded as a leave
continue;
}
BasicBlock targetBlock = labelInfo.bb;
Debug.Assert(!IsSpecialEndHandlerBlock(targetBlock));
if (targetBlock.HasNoRegularInstructions)
{
BasicBlock targetsTarget = null;
switch (targetBlock.BranchCode)
{
case ILOpCode.Br:
targetsTarget = targetBlock.BranchBlock;
break;
case ILOpCode.Nop:
targetsTarget = targetBlock.NextBlock;
break;
}
if ((targetsTarget != null) && (targetsTarget != targetBlock))
{
ExceptionHandlerScope currentHandler = targetBlock.EnclosingHandler;
ExceptionHandlerScope newHandler = targetsTarget.EnclosingHandler;
// can skip the jump if it is in the same try scope
if (CanMoveLabelToAnotherHandler(currentHandler, newHandler))
{
_labelInfos[label] = labelInfo.WithNewTarget(targetsTarget);
madeChanges = true;
// since we modified at least one label we want to try again.
done = false;
}
}
}
}
} while (!done);
return(madeChanges);
}
public ExceptionHandlerLeaderBlock(
ILBuilder builder,
ExceptionHandlerScope enclosingHandler,
BlockType type
) : base(builder, enclosingHandler)
{
_type = type;
}
private static ScopeBounds GetBounds(ExceptionHandlerScope scope)
{
var scopes = ArrayBuilder <Cci.LocalScope> .GetInstance();
var result = scope.GetLocalScopes(scopes, edgeInclusive: false);
scopes.Free();
return(result);
}
private static ScopeBounds GetBounds(ExceptionHandlerScope scope)
{
ArrayBuilder <Cci.LocalScope> scopes = ArrayBuilder <Cci.LocalScope> .GetInstance();
ScopeBounds result = scope.GetLocalScopes(scopes);
scopes.Free();
return(result);
}
public virtual BasicBlock CreateBlock(ILBuilder builder)
{
ExceptionHandlerScope enclosingHandler = builder.EnclosingExceptionHandler;
BasicBlock block = enclosingHandler == null?
AllocatePooledBlock(builder) :
new BasicBlockWithHandlerScope(builder, enclosingHandler);
AddBlock(block);
return(block);
}
private bool ForwardLabelsNoLeaving()
{
bool madeChanges = false;
SmallDictionary <object, LabelInfo> .KeyCollection labels = _labelInfos.Keys;
bool done;
do
{
done = true;
foreach (object label in labels)
{
LabelInfo labelInfo = _labelInfos[label];
BasicBlock targetBlock = labelInfo.bb;
Debug.Assert(!IsSpecialEndHandlerBlock(targetBlock));
if (targetBlock.HasNoRegularInstructions)
{
BasicBlock targetsTarget = null;
switch (targetBlock.BranchCode)
{
case ILOpCode.Br:
targetsTarget = targetBlock.BranchBlock;
break;
case ILOpCode.Nop:
targetsTarget = targetBlock.NextBlock;
break;
}
if ((targetsTarget != null) && (targetsTarget != targetBlock))
{
ExceptionHandlerScope currentHandler = targetBlock.EnclosingHandler;
ExceptionHandlerScope newHandler = targetsTarget.EnclosingHandler;
// forward the label if can be done without leaving current handler
if (currentHandler == newHandler)
{
_labelInfos[label] = labelInfo.WithNewTarget(targetsTarget);
madeChanges = true;
// since we modified at least one label we want to try again.
done = false;
}
}
}
}
} while (!done);
return(madeChanges);
}
// if branch is blocked by a nonterminating finally,
// returns label for a landing block used as a target of blocked branches
// Otherwise returns null
private static object BlockedBranchDestination(BasicBlock src, BasicBlock dest)
{
ExceptionHandlerScope srcHandler = src.EnclosingHandler;
// most common case - we are not in an exception handler.
if (srcHandler == null)
{
return(null);
}
return(BlockedBranchDestinationSlow(dest.EnclosingHandler, srcHandler));
}
internal void CloseScope(ILBuilder builder)
{
ScopeInfo scope = _scopes.Pop();
scope.CloseScope(builder);
if (scope.IsExceptionHandler)
{
_enclosingExceptionHandler = GetEnclosingExceptionHandler();
}
Debug.Assert(_enclosingExceptionHandler == GetEnclosingExceptionHandler());
}
internal void CloseScope(ILBuilder builder)
{
var scope = scopes.Pop();
scope.CloseScope(builder);
if (scope.IsExceptionHandler)
{
this.enclosingExceptionHandler = GetEnclosingExceptionHandler();
}
Debug.Assert(this.enclosingExceptionHandler == GetEnclosingExceptionHandler());
}
private static bool CanMoveLabelToAnotherHandler(
ExceptionHandlerScope currentHandler,
ExceptionHandlerScope newHandler
)
{
// Generally, assuming already valid code that contains "LABEL1: goto LABEL2"
// we can substitute LABEL1 for LABEL2 so that the branches go directly to
// the final destination.
// Technically we can allow "moving" a label to any scope that contains the current one
// However we should be careful with the cases when current label is protected by a
// catch clause.
//
// [COMPAT]
// If we move a label out of catch-protected try clause, we could be forcing JIT to inject
// it back since, in the case of Thread.Abort, the re-throwing of the exception needs
// to happen around this leave instruction which we would be removing.
// In addition to just extra work on the JIT side, handling of this case appears to be
// very delicate and there are known cases where JITs did not handle this particular
// scenario correctly resulting in various violations of Thread.Abort behavior.
// We cannot rely on these JIT issues being fixed in the end user environment.
//
// Considering that we are only winning a single LEAVE here, it seems reasonable to
// just disallow labels to move outside of a catch-protected regions.
// no handler means outermost scope (method level)
if (newHandler == null && currentHandler.ContainingExceptionScope.FinallyOnly())
{
return(true);
}
// check if the target handler contains current handler.
do
{
if (currentHandler == newHandler)
{
return(true);
}
var containerScope = currentHandler.ContainingExceptionScope;
if (!containerScope.FinallyOnly())
{
// this may move the label outside of catch-protected region
// we will disallow that.
return(false);
}
currentHandler = containerScope.ContainingHandler;
} while (currentHandler != null);
return(false);
}
internal ScopeInfo OpenScope(ScopeType scopeType, Cci.ITypeReference exceptionType)
{
ScopeInfo scope = CurrentScope.OpenScope(scopeType, exceptionType, _enclosingExceptionHandler);
_scopes.Push(scope);
if (scope.IsExceptionHandler)
{
_enclosingExceptionHandler = (ExceptionHandlerScope)scope;
}
Debug.Assert(_enclosingExceptionHandler == GetEnclosingExceptionHandler());
return(scope);
}
public override ScopeInfo OpenScope(
ScopeType scopeType,
Cci.ITypeReference exceptionType,
ExceptionHandlerScope currentExceptionHandler)
{
ScopeInfo scope = base.OpenScope(scopeType, exceptionType, currentExceptionHandler);
if (_nestedScopes == null)
{
_nestedScopes = ImmutableArray.CreateBuilder <ScopeInfo>(1);
}
_nestedScopes.Add(scope);
return(scope);
}
public virtual ScopeInfo OpenScope(ScopeType scopeType,
Microsoft.Cci.ITypeReference exceptionType,
ExceptionHandlerScope currentHandler)
{
if (scopeType == ScopeType.TryCatchFinally)
{
return(new ExceptionHandlerContainerScope(currentHandler));
}
else
{
Debug.Assert(scopeType == ScopeType.Variable || scopeType == ScopeType.StateMachineVariable);
return(new LocalScopeInfo());
}
}
internal ScopeInfo OpenScope(ScopeType scopeType, Microsoft.Cci.ITypeReference exceptionType)
{
var scope = CurrentScope.OpenScope(scopeType, exceptionType, this.enclosingExceptionHandler);
scopes.Push(scope);
if (scope.IsExceptionHandler)
{
this.enclosingExceptionHandler = (ExceptionHandlerScope)scope;
}
Debug.Assert(this.enclosingExceptionHandler == GetEnclosingExceptionHandler());
return(scope);
}
/// <summary>
/// Marks blocks that are recursively reachable from the given block.
/// </summary>
private static void MarkReachableFrom(ArrayBuilder <BasicBlock> reachableBlocks, BasicBlock block)
{
tryAgain:
if (block != null && block.Reachability == Reachability.NotReachable)
{
block.Reachability = Reachability.Reachable;
ILOpCode branchCode = block.BranchCode;
if (branchCode == ILOpCode.Nop && block.Type == BlockType.Normal)
{
block = block.NextBlock;
goto tryAgain;
}
if (branchCode.CanFallThrough())
{
PushReachableBlockToProcess(reachableBlocks, block.NextBlock);
}
else
{
// If this block is an "endfinally" block, then clear
// the reachability of the following special block.
if (branchCode == ILOpCode.Endfinally)
{
ExceptionHandlerScope enclosingFinally = block.EnclosingHandler;
enclosingFinally?.UnblockFinally();
}
}
switch (block.Type)
{
case BlockType.Switch:
MarkReachableFromSwitch(reachableBlocks, block);
break;
case BlockType.Try:
MarkReachableFromTry(reachableBlocks, block);
break;
default:
MarkReachableFromBranch(reachableBlocks, block);
break;
}
}
}
private static object BlockedBranchDestinationSlow(
ExceptionHandlerScope destHandler,
ExceptionHandlerScope srcHandler
)
{
ScopeInfo destHandlerScope = null;
if (destHandler != null)
{
destHandlerScope = destHandler.ContainingExceptionScope;
}
// go from the source out until no longer crossing any finally blocks
// between source and destination
// if any finally blocks found in the process, check if they are blocking
while (srcHandler != destHandler)
{
// branches within same ContainingExceptionScope do not go through finally.
// only checking that source and destination are within the same handler would miss the case
// of branching from catch into corresponding try.
if (srcHandler.ContainingExceptionScope == destHandlerScope)
{
break;
}
if (srcHandler.Type == ScopeType.Try)
{
var handlerBlock = srcHandler.LeaderBlock.NextExceptionHandler;
if (handlerBlock.Type == BlockType.Finally)
{
var blockedDest = handlerBlock.EnclosingHandler.BlockedByFinallyDestination;
if (blockedDest != null)
{
return(blockedDest);
}
}
}
srcHandler = srcHandler.ContainingExceptionScope.ContainingHandler;
}
return(null);
}
private static bool InSameOrOuterHandler(ExceptionHandlerScope currentHandler,
ExceptionHandlerScope newHandler)
{
// no handler means outermost scope (method level)
if (newHandler == null)
{
return(true);
}
// check if the target handler contains current handler.
do
{
if (currentHandler == newHandler)
{
return(true);
}
currentHandler = currentHandler.ContainingExceptionScope.ContainingHandler;
} while (currentHandler != null);
return(false);
}
public override void CloseScope(ILBuilder builder)
{
Debug.Assert(_handlers.Count > 1);
// Fix up the NextExceptionHandler reference of each leader block.
ExceptionHandlerScope tryScope = _handlers[0];
ExceptionHandlerLeaderBlock previousBlock = tryScope.LeaderBlock;
for (int i = 1; i < _handlers.Count; i++)
{
ExceptionHandlerScope handlerScope = _handlers[i];
ExceptionHandlerLeaderBlock nextBlock = handlerScope.LeaderBlock;
previousBlock.NextExceptionHandler = nextBlock;
previousBlock = nextBlock;
}
// Generate label for try/catch "leave" target.
builder.MarkLabel(_endLabel);
// hide the following code, since it could be reached through the label above.
builder.DefineHiddenSequencePoint();
Debug.Assert(builder._currentBlock == builder._labelInfos[_endLabel].bb);
if (_handlers[1].Type == ScopeType.Finally)
{
// Generate "nop" branch to itself. If this block is unreachable
// (because the finally block does not complete), the "nop" will be
// replaced by Br_s. On the other hand, if this block is reachable,
// the "nop" will be skipped so any "leave" instructions jumping
// to this block will jump to the next instead.
builder.EmitBranch(ILOpCode.Nop, _endLabel);
_handlers[1].SetBlockedByFinallyDestination(_endLabel);
}
}
private static bool InSameOrOuterHandler(ExceptionHandlerScope currentHandler,
ExceptionHandlerScope newHandler)
{
// no handler means outermost scope (method level)
if (newHandler == null)
{
return true;
}
// check if the target handler contains current handler.
do
{
if (currentHandler == newHandler)
{
return true;
}
currentHandler = currentHandler.ContainingExceptionScope.ContainingHandler;
} while (currentHandler != null);
return false;
}
internal override void GetExceptionHandlerRegions(ArrayBuilder <Cci.ExceptionHandlerRegion> regions)
{
Debug.Assert(_handlers.Count > 1);
ExceptionHandlerScope tryScope = null;
ScopeBounds tryBounds = new ScopeBounds();
foreach (ExceptionHandlerScope handlerScope in _handlers)
{
// Partition I, section 12.4.2.5:
// The ordering of the exception clauses in the Exception Handler Table is important. If handlers are nested,
// the most deeply nested try blocks shall come before the try blocks that enclose them.
//
// so we collect the inner regions first.
handlerScope.GetExceptionHandlerRegions(regions);
ScopeBounds handlerBounds = GetBounds(handlerScope);
if (tryScope == null)
{
// the first scope that we see should be Try.
Debug.Assert(handlerScope.Type == ScopeType.Try);
tryScope = handlerScope;
tryBounds = handlerBounds;
Reachability reachability = tryScope.LeaderBlock.Reachability;
Debug.Assert((reachability == Reachability.Reachable) || (reachability == Reachability.NotReachable));
// All handler blocks should have same reachability.
Debug.Assert(_handlers.All(h => (h.LeaderBlock.Reachability == reachability)));
if (reachability != Reachability.Reachable)
{
return;
}
}
else
{
Cci.ExceptionHandlerRegion region;
switch (handlerScope.Type)
{
case ScopeType.Finally:
region = new Cci.ExceptionHandlerRegionFinally(tryBounds.Begin, tryBounds.End, handlerBounds.Begin, handlerBounds.End);
break;
case ScopeType.Fault:
region = new Cci.ExceptionHandlerRegionFault(tryBounds.Begin, tryBounds.End, handlerBounds.Begin, handlerBounds.End);
break;
case ScopeType.Catch:
region = new Cci.ExceptionHandlerRegionCatch(tryBounds.Begin, tryBounds.End, handlerBounds.Begin, handlerBounds.End, handlerScope.ExceptionType);
break;
case ScopeType.Filter:
region = new Cci.ExceptionHandlerRegionFilter(tryBounds.Begin, tryBounds.End, handlerScope.FilterHandlerStart, handlerBounds.End, handlerBounds.Begin);
break;
default:
throw ExceptionUtilities.UnexpectedValue(handlerScope.Type);
}
regions.Add(region);
}
}
}
public ExceptionHandlerContainerScope(ExceptionHandlerScope containingHandler)
{
_handlers = ImmutableArray.CreateBuilder <ExceptionHandlerScope>(2);
_containingHandler = containingHandler;
_endLabel = new object();
}
private static object BlockedBranchDestinationSlow(ExceptionHandlerScope destHandler, ExceptionHandlerScope srcHandler)
{
ScopeInfo destHandlerScope = null;
if (destHandler != null)
{
destHandlerScope = destHandler.ContainingExceptionScope;
}
// go from the source out until we no longer crossing any finallies
// between source and destination
// if any finallies found in the process, check if they are blocking
while (srcHandler != destHandler)
{
// branches within same ContainingExceptionScope do not go through finally.
// only checking that source and destination are within the same handler would miss the case
// of branching from catch into corresponding try.
if (srcHandler.ContainingExceptionScope == destHandlerScope)
{
break;
}
if (srcHandler.Type == ScopeType.Try)
{
var handlerBlock = srcHandler.LeaderBlock.NextExceptionHandler;
if (handlerBlock.Type == BlockType.Finally)
{
var blockedDest = handlerBlock.EnclosingHandler.BlockedByFinallyDestination;
if (blockedDest != null)
{
return blockedDest;
}
}
}
srcHandler = srcHandler.ContainingExceptionScope.ContainingHandler;
}
return null;
}
private static bool CanMoveLabelToAnotherHandler(ExceptionHandlerScope currentHandler,
ExceptionHandlerScope newHandler)
{
// Generally, assuming already valid code that contains "LABEL1: goto LABEL2"
// we can substitute LABEL1 for LABEL2 so that the branches go directly to
// the final destination.
// Technically we can allow "moving" a label to any scope that contains the current one
// However we should be careful with the cases when current label is protected by a
// catch clause.
//
// [COMPAT]
// If we move a label out of catch-protected try clause, we could be forcing JIT to inject
// it back since, in the case of Thread.Abort, the re-throwing of the exception needs
// to happen around this leave instruction which we would be removing.
// In addition to just extra work on the JIT side, handling of this case appears to be
// very delicate and there are known cases where JITs did not handle this particular
// scenario correctly resulting in various violations of Thread.Abort behavior.
// We cannot rely on these JIT issues being fixed in the end user environment.
//
// Considering that we are only winning a single LEAVE here, it seems reasonable to
// just disallow labels to move outside of a catch-protected regions.
// no handler means outermost scope (method level)
if (newHandler == null && currentHandler.ContainingExceptionScope.FinallyOnly())
{
return true;
}
// check if the target handler contains current handler.
do
{
if (currentHandler == newHandler)
{
return true;
}
var containerScope = currentHandler.ContainingExceptionScope;
if (!containerScope.FinallyOnly())
{
// this may move the label outside of catch-protected region
// we will disallow that.
return false;
}
currentHandler = containerScope.ContainingHandler;
} while (currentHandler != null);
return false;
}
public BasicBlockWithHandlerScope(ILBuilder builder, ExceptionHandlerScope enclosingHandler)
: base(builder)
{
this.enclosingHandler = enclosingHandler;
}
public ExceptionHandlerLeaderBlock(ILBuilder builder, ExceptionHandlerScope enclosingHandler, BlockType type) :
base(builder, enclosingHandler)
{
_type = type;
}
public SwitchBlock(ILBuilder builder, ExceptionHandlerScope enclosingHandler) :
base(builder, enclosingHandler)
{
this.SetBranchCode(ILOpCode.Switch);
}
public SwitchBlock(ILBuilder builder, ExceptionHandlerScope enclosingHandler) :
base(builder, enclosingHandler)
{
this.SetBranchCode(ILOpCode.Switch);
}
public ExceptionHandlerAttribute(Type ExceptionType, ExceptionHandlerScope Scope = ExceptionHandlerScope.Global)
{
this.Scope = Scope;
this.ExceptionType = ExceptionType;
}
