/// <summary>
/// Transform local exception variable.
/// </summary>
void TransformCatchVariable(TryCatchHandler handler, Block entryPoint)
{
if (!entryPoint.Instructions[0].MatchStLoc(out var exceptionVar, out var exceptionSlotLoad))
{
return;
}
if (!exceptionVar.IsSingleDefinition || exceptionVar.Kind != VariableKind.Local)
{
return;
}
if (!exceptionSlotLoad.MatchLdLoc(handler.Variable) || !handler.Variable.IsSingleDefinition || handler.Variable.LoadCount != 1)
{
return;
}
handler.Variable = exceptionVar;
exceptionVar.Kind = VariableKind.Exception;
entryPoint.Instructions.RemoveAt(0);
}
/// <summary>
/// catch ex : TException when (...) BlockContainer {
/// Block entryPoint (incoming: 1) {
/// stloc v(ldloc ex)
/// ...
/// }
/// }
/// =>
/// catch v : TException when (...) BlockContainer {
/// Block entryPoint (incoming: 1) {
/// ...
/// }
/// }
/// </summary>
void TransformCatchVariable(TryCatchHandler handler, Block entryPoint, bool isCatchBlock)
{
if (!handler.Variable.IsSingleDefinition || handler.Variable.LoadCount != 1)
{
return; // handle.Variable already has non-trivial uses
}
if (!entryPoint.Instructions[0].MatchStLoc(out var exceptionVar, out var exceptionSlotLoad))
{
// Not the pattern with a second exceptionVar.
// However, it is still possible that we need to remove a pointless UnboxAny:
if (handler.Variable.LoadInstructions.Single().Parent is UnboxAny inlinedUnboxAny)
{
if (inlinedUnboxAny.Type.Equals(handler.Variable.Type))
{
context.Step("TransformCatchVariable - remove inlined UnboxAny", inlinedUnboxAny);
inlinedUnboxAny.ReplaceWith(inlinedUnboxAny.Argument);
foreach (var range in inlinedUnboxAny.ILRanges)
{
handler.AddExceptionSpecifierILRange(range);
}
}
}
return;
}
if (exceptionVar.Kind != VariableKind.Local && exceptionVar.Kind != VariableKind.StackSlot)
{
return;
}
if (exceptionSlotLoad is UnboxAny unboxAny)
{
// When catching a type parameter, csc emits an unbox.any instruction
if (!unboxAny.Type.Equals(handler.Variable.Type))
{
return;
}
exceptionSlotLoad = unboxAny.Argument;
}
if (!exceptionSlotLoad.MatchLdLoc(handler.Variable))
{
return;
}
// Check that exceptionVar is only used within the catch block:
var allUses = exceptionVar.LoadInstructions
.Concat(exceptionVar.StoreInstructions.Cast <ILInstruction>())
.Concat(exceptionVar.AddressInstructions);
foreach (var inst in allUses)
{
if (!inst.IsDescendantOf(handler))
{
return;
}
}
context.Step("TransformCatchVariable", entryPoint.Instructions[0]);
exceptionVar.Kind = VariableKind.ExceptionLocal;
exceptionVar.Type = handler.Variable.Type;
handler.Variable = exceptionVar;
if (isCatchBlock)
{
foreach (var offset in entryPoint.Instructions[0].Descendants.SelectMany(o => o.ILRanges))
{
handler.AddExceptionSpecifierILRange(offset);
}
}
entryPoint.Instructions.RemoveAt(0);
}
protected override void BeginTryCatchHandler(TryCatchHandler inst)
{
HandleStore(inst.Variable);
base.BeginTryCatchHandler(inst);
}
/// <summary>
/// TryCatchHandler is handled directly in VisitTryCatch
/// </summary>
protected internal override sealed void VisitTryCatchHandler(TryCatchHandler inst)
{
throw new NotSupportedException();
}
protected virtual void BeginTryCatchHandler(TryCatchHandler inst)
{
}
