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);
}
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);
}
private bool TryOptimizeSameAsNext(BasicBlock next, ref int delta)
{
if (next.HasNoRegularInstructions &&
next.BranchCode == this.BranchCode &&
next.BranchBlock.Start == this.BranchBlock.Start)
{
if (next.EnclosingHandler == this.EnclosingHandler)
{
int diff = this.BranchCode.Size() + this.BranchCode.GetBranchOperandSize();
delta -= diff;
this.SetBranch(null, ILOpCode.Nop);
// If current block has no regular instructions the resulting block is a trivial noop
// TryOptimizeBranchOverUncondBranch relies on an invariant that
// trivial blocks are not targeted by branches,
// make sure we are not breaking this condition.
if (this.HasNoRegularInstructions)
{
SmallDictionary <object, LabelInfo> labelInfos = builder._labelInfos;
SmallDictionary <object, LabelInfo> .KeyCollection labels = labelInfos.Keys;
foreach (object label in labels)
{
LabelInfo info = labelInfos[label];
if (info.bb == this)
{
// move the label from "this" to "next"
labelInfos[label] = info.WithNewTarget(next);
}
}
}
return(true);
}
}
return(false);
}