// codegen algorithm for unified try-catch-else-finally
// isTryYielded = false
// isCatchYielded = false
// isFinallyYielded = false
// isElseYielded = false
// Set up the labels for Try Yield Targets
// Set up the labels for Catch Yield Targets
// Set up the labels for Else Yield Targets
// Set up the labels for Finally Yield Targets
// returnVar = false
// isElseBlock = false
//TRY:
// if isCatchYielded :
// rethow storedException
// if finallyYielded :
// goto endOfTry
// if isElseYielded :
// goto beginElseBlock
// if isTryYielded:
// isTryYielded = false
// goto desired_label_in_TRY-BODY
// TRY-BODY
// beginElseBlock: # Note we are still under TRY
// isElseBlock = true
// if isElseYielded :
// isElseYielded = false
// goto desired_label_in_ELSE-BODY
// ELSE-BODY
// endOfTry:
//EXCEPT: # catches any exception
// if isElseBlock:
// rethrow
// pyExc = ExtractException()
// storedException = ExtractSysExcInfo()
// if pyExc == handler[0].Test :
// if isCatchYielded :
// isCatchYielded = false
// goto desired_label_in_HANDLER-BODY
// HANDLER-BODY
// ClearException()
// Leave afterFinally
// elif pyExc == handler[1].Test :
// if isCatchYielded :
// isCatchYielded = false
// goto desired_label_in_HANDLER-BODY
// HANDLER-BODY
// ClearException()
// Leave afterFinally
// .
// .
// .
// Rethrow
//FINALLY:
// if (isTryYielded or isCatchYielded or isElseYielded ):
// goto endOfFinally
// if isFinallyYielded :
// isFinallyYielded = false
// goto desired_label_in_FINALLY-BODY
// FINALLY-BODY
// endOfFinally:
// #try-cathch-finally ends here
// afterFinally:
// if not returnVar :
// goto noReturn
// if (finally may yield ):
// return 1
// else
// return appropriate_return_value
// noReturn:
internal override void Emit(CodeGen cg)
{
// environmental slots
Slot isTryYielded = null;
Slot isCatchYielded = null;
Slot isFinallyYielded = null;
Slot isElseYielded = null;
Slot storedException = null;
// local slots
Slot tryChoiceVar = null;
Slot catchChoiceVar = null;
Slot elseChoiceVar = null;
Slot finallyChoiceVar = null;
Slot flowControlVar = cg.GetLocalTmp(typeof(int));
Slot isElseBlock = null;
cg.EmitPosition(Start, header);
if (IsBlockYieldable(tryYieldTargets)) {
tryChoiceVar = cg.GetLocalTmp(typeof(int));
isTryYielded = cg.Names.GetTempSlot("is", typeof(object));
cg.EmitFieldGet(typeof(Ops).GetField("FALSE"));
isTryYielded.EmitSet(cg);
}
if (IsBlockYieldable(catchYieldTargets)) {
catchChoiceVar = cg.GetLocalTmp(typeof(int));
storedException = cg.Names.GetTempSlot("exc", typeof(object));
isCatchYielded = cg.Names.GetTempSlot("is", typeof(object));
cg.EmitFieldGet(typeof(Ops).GetField("FALSE"));
isCatchYielded.EmitSet(cg);
}
if (IsBlockYieldable(finallyYieldTargets)) {
finallyChoiceVar = cg.GetLocalTmp(typeof(int));
isFinallyYielded = cg.Names.GetTempSlot("is", typeof(object));
cg.EmitFieldGet(typeof(Ops).GetField("FALSE"));
isFinallyYielded.EmitSet(cg);
}
if (IsBlockYieldable(elseYieldTargets)) {
elseChoiceVar = cg.GetLocalTmp(typeof(int));
isElseYielded = cg.Names.GetTempSlot("is", typeof(object));
cg.EmitFieldGet(typeof(Ops).GetField("FALSE"));
isElseYielded.EmitSet(cg);
}
if (elseStmt != null) {
isElseBlock = cg.GetLocalTmp(typeof(bool));
cg.EmitInt(0);
isElseBlock.EmitSet(cg);
}
Slot exception = null;
bool foundLoopControl;
bool returnInFinally = ControlFlowFinder.FindControlFlow(FinallyStatement, out foundLoopControl);
if (IsBlockYieldable(finallyYieldTargets)) {
exception = cg.Names.GetTempSlot("exception", typeof(Exception));
cg.Emit(OpCodes.Ldnull);
exception.EmitSet(cg);
} else if (returnInFinally) {
exception = cg.GetLocalTmp(typeof(Exception));
cg.Emit(OpCodes.Ldnull);
exception.EmitSet(cg);
}
EmitTopYieldTargetLabels(tryYieldTargets, tryChoiceVar, cg);
EmitTopYieldTargetLabels(catchYieldTargets, catchChoiceVar, cg);
EmitTopYieldTargetLabels(elseYieldTargets, elseChoiceVar, cg);
EmitTopYieldTargetLabels(finallyYieldTargets, finallyChoiceVar, cg);
cg.EmitInt(CodeGen.FinallyExitsNormally);
flowControlVar.EmitSet(cg);
Label afterFinally = cg.DefineLabel();
cg.PushExceptionBlock(Targets.TargetBlockType.Try, flowControlVar, isTryYielded);
cg.BeginExceptionBlock();
// if catch yielded, rethow the storedException to be handled by Catch block
if (IsBlockYieldable(catchYieldTargets)) {
Label testFinally = cg.DefineLabel();
isCatchYielded.EmitGet(cg);
cg.EmitUnbox(typeof(bool));
cg.Emit(OpCodes.Brfalse, testFinally);
storedException.EmitGet(cg);
cg.EmitCall(typeof(Ops), "Raise", new Type[] { typeof(object) });
cg.MarkLabel(testFinally);
}
// if Finally yielded, Branch to the end of Try block
Label endOfTry = cg.DefineLabel();
EmitOnYieldBranchToLabel(finallyYieldTargets, isFinallyYielded, endOfTry, cg);
Label beginElseBlock = cg.DefineLabel();
if (IsBlockYieldable(elseYieldTargets)) {
// isElseYielded ?
Debug.Assert(isElseYielded != null);
isElseYielded.EmitGet(cg);
cg.EmitUnbox(typeof(bool));
cg.Emit(OpCodes.Brtrue, beginElseBlock);
}
EmitYieldDispatch(tryYieldTargets, isTryYielded, tryChoiceVar, cg);
// if finally block presents, but no exception handler, we add try-fault
// to update traceback; otherwise, we update the traceback inside exception handler.
if (finallyStmt != null && handlers == null) {
Slot dummySlot = cg.GetLocalTmp(typeof(object));
cg.EmitTraceBackTryBlockStart(dummySlot);
body.Emit(cg);
cg.FreeLocalTmp(dummySlot);
cg.EmitTraceBackFaultBlock();
} else {
body.Emit(cg);
}
if (elseStmt != null) {
if (IsBlockYieldable(elseYieldTargets)) {
cg.MarkLabel(beginElseBlock);
}
cg.PopTargets(Targets.TargetBlockType.Try);
cg.PushExceptionBlock(Targets.TargetBlockType.Else, flowControlVar, isElseYielded);
cg.EmitInt(1);
isElseBlock.EmitSet(cg);
EmitYieldDispatch(elseYieldTargets, isElseYielded, elseChoiceVar, cg);
elseStmt.Emit(cg);
cg.PopTargets(Targets.TargetBlockType.Else);
cg.PushExceptionBlock(Targets.TargetBlockType.Try, flowControlVar, isTryYielded);
}
cg.MarkLabel(endOfTry);
// get the exception if there is a yield / return in finally
if (IsBlockYieldable(finallyYieldTargets) || returnInFinally) {
cg.BeginCatchBlock(typeof(Exception));
exception.EmitSet(cg);
}
if (handlers != null) {
cg.PushExceptionBlock(Targets.TargetBlockType.Catch, flowControlVar, isCatchYielded);
if (IsBlockYieldable(finallyYieldTargets) || returnInFinally) {
exception.EmitGet(cg);
} else {
cg.BeginCatchBlock(typeof(Exception));
}
// if in Catch block due to exception in else block -> just rethrow
if (elseStmt != null) {
Label beginCatchBlock = cg.DefineLabel();
isElseBlock.EmitGet(cg);
cg.Emit(OpCodes.Brfalse, beginCatchBlock);
cg.Emit(OpCodes.Rethrow);
cg.MarkLabel(beginCatchBlock);
}
cg.EmitCallUpdateTraceBack();
// Extract state from the carrier exception
cg.EmitCallerContext();
cg.EmitCall(typeof(Ops), "ExtractException",
new Type[] { typeof(Exception), typeof(ICallerContext) });
Slot pyExc = cg.GetLocalTmp(typeof(object));
Slot tmpExc = cg.GetLocalTmp(typeof(object));
pyExc.EmitSet(cg);
if (IsBlockYieldable(catchYieldTargets)) {
cg.EmitCallerContext();
cg.EmitCall(typeof(Ops), "ExtractSysExcInfo");
storedException.EmitSet(cg);
}
foreach (TryStatementHandler handler in handlers) {
cg.EmitPosition(handler.Start, handler.Header);
Label next = cg.DefineLabel();
if (handler.Test != null) {
pyExc.EmitGet(cg);
handler.Test.Emit(cg);
cg.EmitCall(typeof(Ops), "CheckException");
if (handler.Target != null) {
tmpExc.EmitSet(cg);
tmpExc.EmitGet(cg);
}
cg.EmitPythonNone();
cg.Emit(OpCodes.Ceq);
cg.Emit(OpCodes.Brtrue, next);
}
if (handler.Target != null) {
tmpExc.EmitGet(cg);
handler.Target.EmitSet(cg);
}
if (IsBlockYieldable(finallyYieldTargets) || returnInFinally) {
cg.Emit(OpCodes.Ldnull);
exception.EmitSet(cg);
}
EmitYieldDispatch(catchYieldTargets, isCatchYielded, catchChoiceVar, cg);
handler.Body.Emit(cg);
cg.EmitCallerContext();
cg.EmitCall(typeof(Ops), "ClearException", new Type[] { typeof(ICallerContext) });
cg.EmitSetTraceBackUpdateStatus(false);
cg.Emit(OpCodes.Leave, afterFinally);
cg.MarkLabel(next);
}
cg.FreeLocalTmp(tmpExc);
cg.FreeLocalTmp(pyExc);
cg.Emit(OpCodes.Rethrow);
cg.PopTargets(Targets.TargetBlockType.Catch);
}
if (finallyStmt != null) {
cg.PushExceptionBlock(Targets.TargetBlockType.Finally, flowControlVar, isFinallyYielded);
cg.BeginFinallyBlock();
Label endOfFinally = cg.DefineLabel();
// if try yielded
EmitOnYieldBranchToLabel(tryYieldTargets, isTryYielded, endOfFinally, cg);
// if catch yielded
EmitOnYieldBranchToLabel(catchYieldTargets, isCatchYielded, endOfFinally, cg);
//if else yielded
EmitOnYieldBranchToLabel(elseYieldTargets, isElseYielded, endOfFinally, cg);
EmitYieldDispatch(finallyYieldTargets, isFinallyYielded, finallyChoiceVar, cg);
finallyStmt.Emit(cg);
if (IsBlockYieldable(finallyYieldTargets) || returnInFinally) {
Label nothrow = cg.DefineLabel();
exception.EmitGet(cg);
cg.Emit(OpCodes.Dup);
cg.Emit(OpCodes.Brfalse_S, nothrow);
cg.Emit(OpCodes.Throw);
cg.MarkLabel(nothrow);
cg.Emit(OpCodes.Pop);
}
cg.MarkLabel(endOfFinally);
cg.EndExceptionBlock();
cg.PopTargets(Targets.TargetBlockType.Finally);
} else {
cg.EndExceptionBlock();
}
cg.PopTargets(Targets.TargetBlockType.Try);
cg.MarkLabel(afterFinally);
Label noReturn = cg.DefineLabel();
flowControlVar.EmitGet(cg);
cg.EmitInt(CodeGen.BranchForReturn);
cg.Emit(OpCodes.Bne_Un, noReturn);
if (cg.IsGenerator()) {
// return true from the generator method
cg.Emit(OpCodes.Ldc_I4_1);
cg.EmitReturn();
} else if (returnInFinally) {
// return the actual value
cg.EmitReturnValue();
cg.EmitReturn();
}
cg.MarkLabel(noReturn);
if (foundLoopControl) {
noReturn = cg.DefineLabel();
flowControlVar.EmitGet(cg);
cg.EmitInt(CodeGen.BranchForBreak);
cg.Emit(OpCodes.Bne_Un, noReturn);
cg.EmitBreak();
cg.MarkLabel(noReturn);
noReturn = cg.DefineLabel();
flowControlVar.EmitGet(cg);
cg.EmitInt(CodeGen.BranchForContinue);
cg.Emit(OpCodes.Bne_Un, noReturn);
cg.EmitContinue();
cg.MarkLabel(noReturn);
}
// clean up
if (IsBlockYieldable(tryYieldTargets)) {
cg.FreeLocalTmp(tryChoiceVar);
tryYieldTargets.Clear();
}
if (IsBlockYieldable(catchYieldTargets)) {
cg.FreeLocalTmp(catchChoiceVar);
catchYieldTargets.Clear();
}
if (IsBlockYieldable(finallyYieldTargets)) {
cg.FreeLocalTmp(finallyChoiceVar);
finallyYieldTargets.Clear();
}
if (IsBlockYieldable(elseYieldTargets)) {
cg.FreeLocalTmp(elseChoiceVar);
elseYieldTargets.Clear();
}
if (elseStmt != null) {
cg.FreeLocalTmp(isElseBlock);
}
#if DEBUG
cg.EmitInt(-1);
flowControlVar.EmitSet(cg);
#endif
cg.FreeLocalTmp(flowControlVar);
}
