// Emit the end cases for a short-circuit
private static void EmitTerminals(ShortCircuitInfo info, FleeILGenerator ilg, Label endLabel)
{
// Emit the false case if it was used
if (info.Branches.HasLabel(OurFalseTerminalKey) == true)
{
Label falseLabel = info.Branches.FindLabel(OurFalseTerminalKey);
// Mark the label and note its position
ilg.MarkLabel(falseLabel);
MarkBranchTarget(info, falseLabel, ilg);
ilg.Emit(OpCodes.Ldc_I4_0);
// If we also have a true terminal, then skip over it
if (info.Branches.HasLabel(OurTrueTerminalKey) == true)
{
ilg.Emit(OpCodes.Br_S, endLabel);
}
}
// Emit the true case if it was used
if (info.Branches.HasLabel(OurTrueTerminalKey) == true)
{
Label trueLabel = info.Branches.FindLabel(OurTrueTerminalKey);
// Mark the label and note its position
ilg.MarkLabel(trueLabel);
MarkBranchTarget(info, trueLabel, ilg);
ilg.Emit(OpCodes.Ldc_I4_1);
}
}
// Visit the nodes of the tree (right then left) and populate some data structures
private void PopulateData(ShortCircuitInfo info)
{
// Is our right child a leaf or another And/Or expression?
AndOrElement andOrChild = MyRightChild as AndOrElement;
if (andOrChild == null)
{
// Leaf so push it on the stack
info.Operands.Push(MyRightChild);
}
else
{
// Another And/Or expression so recurse
andOrChild.PopulateData(info);
}
// Add ourselves as an operator
info.Operators.Push(this);
// Do the same thing for the left child
andOrChild = MyLeftChild as AndOrElement;
if (andOrChild == null)
{
info.Operands.Push(MyLeftChild);
}
else
{
andOrChild.PopulateData(info);
}
}
// Note a label's position if we are in mark mode
private static void MarkBranchTarget(ShortCircuitInfo info, Label target, FleeILGenerator ilg)
{
if (ilg.IsTemp == true)
{
info.Branches.MarkLabel(ilg, target);
}
}
// Emit a short-circuited logical operation sequence
// The idea: Store all the leaf operands in a stack with the leftmost at the top and rightmost at the bottom.
// For each operand, emit it and try to find an end point for when it short-circuits. This means we go up through
// the stack of operators (ignoring siblings) until we find a different operation (then emit a branch to its right operand)
// or we reach the root (emit a branch to a true/false).
// Repeat the process for all operands and then emit the true/false/last operand end cases.
private void EmitLogical(FleeILGenerator ilg, ShortCircuitInfo info, IServiceProvider services)
{
// We always have an end label
info.Branches.GetLabel(OurEndLabelKey, ilg);
// Populate our data structures
this.PopulateData(info);
// Emit the sequence
EmitLogicalShortCircuit(ilg, info, services);
// Get the last operand
ExpressionElement terminalOperand = info.Operands.Pop() as ExpressionElement;
// Emit it
EmitOperand(terminalOperand, info, ilg, services);
// And jump to the end
Label endLabel = info.Branches.FindLabel(OurEndLabelKey);
ilg.Emit(OpCodes.Br_S, endLabel);
// Emit our true/false terminals
EmitTerminals(info, ilg, endLabel);
// Mark the end
ilg.MarkLabel(endLabel);
}
private static void EmitOperand(ExpressionElement operand, ShortCircuitInfo info, FleeILGenerator ilg, IServiceProvider services)
{
// Is this operand the target of a label?
if (info.Branches.HasLabel(operand) == true)
{
// Yes, so mark it
Label leftLabel = info.Branches.FindLabel(operand);
ilg.MarkLabel(leftLabel);
// Note the label's position
MarkBranchTarget(info, leftLabel, ilg);
}
// Emit the operand
operand.Emit(ilg, services);
}
// Emit a sequence of and/or expressions with short-circuiting
private static void EmitLogicalShortCircuit(FleeILGenerator ilg, ShortCircuitInfo info, IServiceProvider services)
{
while (info.Operators.Count != 0)
{
// Get the operator
AndOrElement op = info.Operators.Pop() as AndOrElement;
// Get the left operand
ExpressionElement leftOperand = info.Operands.Pop() as ExpressionElement;
// Emit the left
EmitOperand(leftOperand, info, ilg, services);
// Get the label for the short-circuit case
Label l = GetShortCircuitLabel(op, info, ilg);
// Emit the branch
EmitBranch(op, ilg, l, info);
}
}
private void DoEmitLogical(FleeILGenerator ilg, IServiceProvider services)
{
// We have to do a 'fake' emit so we can get the positions of the labels
ShortCircuitInfo info = new ShortCircuitInfo();
// Create a temporary IL generator
FleeILGenerator ilgTemp = this.CreateTempFleeILGenerator(ilg);
// We have to make sure that the label count for the temp FleeILGenerator matches our real FleeILGenerator
Utility.SyncFleeILGeneratorLabels(ilg, ilgTemp);
// Do the fake emit
this.EmitLogical(ilgTemp, info, services);
// Clear everything except the label positions
info.ClearTempState();
info.Branches.ComputeBranches();
Utility.SyncFleeILGeneratorLabels(ilgTemp, ilg);
// Do the real emit
this.EmitLogical(ilg, info, services);
}
// Get the label for a short-circuit
private static Label GetShortCircuitLabel(AndOrElement current, ShortCircuitInfo info, FleeILGenerator ilg)
{
// We modify the given stacks so we need to clone them
Stack cloneOperands = info.Operands.Clone() as Stack;
Stack cloneOperators = info.Operators.Clone() as Stack;
// Pop all siblings
current.PopRightChild(cloneOperands, cloneOperators);
// Go until we run out of operators
while (cloneOperators.Count > 0)
{
// Get the top operator
AndOrElement top = cloneOperators.Pop() as AndOrElement;
// Is is a different operation?
if (top.MyOperation != current.MyOperation)
{
// Yes, so return a label to its right operand
object nextOperand = cloneOperands.Pop();
return(GetLabel(nextOperand, ilg, info));
}
else
{
// No, so keep going up the stack
top.PopRightChild(cloneOperands, cloneOperators);
}
}
// We've reached the end of the stack so return the label for the appropriate true/false terminal
if (current.MyOperation == AndOrOperation.And)
{
return(GetLabel(OurFalseTerminalKey, ilg, info));
}
else
{
return(GetLabel(OurTrueTerminalKey, ilg, info));
}
}
private static Label GetLabel(object key, FleeILGenerator ilg, ShortCircuitInfo info)
{
return(info.Branches.GetLabel(key, ilg));
}
private static void EmitBranch(AndOrElement op, FleeILGenerator ilg, Label target, ShortCircuitInfo info)
{
if (ilg.IsTemp == true)
{
info.Branches.AddBranch(ilg, target);
// Temp mode; just emit a short branch and return
OpCode shortBranch = GetBranchOpcode(op, false);
ilg.Emit(shortBranch, target);
return;
}
// Emit the proper branch opcode
// Determine if it is a long branch
bool longBranch = info.Branches.IsLongBranch(ilg, target);
// Get the branch opcode
OpCode brOpcode = GetBranchOpcode(op, longBranch);
// Emit the branch
ilg.Emit(brOpcode, target);
}
