protected override void DoEmitCode(CompilerTarget target, StackSemantics stackSemantics)
{
if(stackSemantics == StackSemantics.Value)
throw new NotSupportedException("Foreach loops don't produce values and can thus not be emitted with value semantics.");
if (!IsInitialized)
throw new PrexoniteException("AstForeachLoop requires List and Element to be set.");
//Optimize expression
_OptimizeNode(target, ref List);
//Create the enumerator variable
var enumVar = Block.CreateLabel("enumerator");
target.Function.Variables.Add(enumVar);
//Create the element assignment statement
var element = Element.GetCopy();
AstExpr optElem;
if (element.TryOptimize(target, out optElem))
{
element = optElem as AstGetSet;
if (element == null)
{
target.Loader.ReportMessage(Message.Error(Resources.AstForeachLoop_DoEmitCode_ElementTooComplicated,Position,MessageClasses.ForeachElementTooComplicated));
return;
}
}
var ldEnumVar = target.Factory.Call(Position, EntityRef.Variable.Local.Create(enumVar));
var getCurrent =
new AstGetSetMemberAccess(File, Line, Column, ldEnumVar, "Current");
element.Arguments.Add(getCurrent);
element.Call = PCall.Set;
//Actual Code Generation
var moveNextAddr = -1;
var getCurrentAddr = -1;
var disposeAddr = -1;
//Get the enumerator
target.BeginBlock(Block);
List.EmitValueCode(target);
target.EmitGetCall(List.Position, 0, "GetEnumerator");
var castAddr = target.Code.Count;
target.Emit(List.Position, OpCode.cast_const, "Object(\"System.Collections.IEnumerator\")");
target.EmitStoreLocal(List.Position, enumVar);
//check whether an enhanced CIL implementation is possible
bool emitHint;
if (element.DefaultAdditionalArguments + element.Arguments.Count > 1)
//has additional arguments
emitHint = false;
else
emitHint = true;
var @try = new AstTryCatchFinally(Position, Block);
@try.TryBlock = new AstActionBlock
(
Position, @try,
delegate
{
target.EmitJump(Position, Block.ContinueLabel);
//Assignment (begin)
target.EmitLabel(Position, Block.BeginLabel);
getCurrentAddr = target.Code.Count;
element.EmitEffectCode(target);
//Code block
Block.EmitEffectCode(target);
//Condition (continue)
target.EmitLabel(Position, Block.ContinueLabel);
moveNextAddr = target.Code.Count;
target.EmitLoadLocal(List.Position, enumVar);
target.EmitGetCall(List.Position, 0, "MoveNext");
target.EmitJumpIfTrue(Position, Block.BeginLabel);
//Break
target.EmitLabel(Position, Block.BreakLabel);
});
@try.FinallyBlock = new AstActionBlock
(
Position, @try,
delegate
{
disposeAddr = target.Code.Count;
target.EmitLoadLocal(List.Position, enumVar);
target.EmitCommandCall(List.Position, 1, Engine.DisposeAlias, true);
});
@try.EmitEffectCode(target);
target.EndBlock();
if (getCurrentAddr < 0 || moveNextAddr < 0 || disposeAddr < 0)
throw new PrexoniteException(
"Could not capture addresses within foreach construct for CIL compiler hint.");
else if (emitHint)
{
var hint = new ForeachHint(enumVar, castAddr, getCurrentAddr, moveNextAddr,
disposeAddr);
Cil.Compiler.AddCilHint(target, hint);
Action<int, int> mkHook =
(index, original) =>
{
AddressChangeHook hook = null;
hook = new AddressChangeHook(
original,
newAddr =>
{
foreach (
var hintEntry in target.Meta[Loader.CilHintsKey].List)
{
var entry = hintEntry.List;
if (entry[0] == ForeachHint.Key &&
entry[index].Text == original.ToString(CultureInfo.InvariantCulture))
{
entry[index] = newAddr.ToString(CultureInfo.InvariantCulture);
// AddressChangeHook.ctor can be trusted not to call the closure.
// ReSharper disable PossibleNullReferenceException
// ReSharper disable AccessToModifiedClosure
hook.InstructionIndex = newAddr;
// ReSharper restore AccessToModifiedClosure
// ReSharper restore PossibleNullReferenceException
original = newAddr;
}
}
});
target.AddressChangeHooks.Add(hook);
};
mkHook(ForeachHint.CastAddressIndex + 1, castAddr);
mkHook(ForeachHint.GetCurrentAddressIndex + 1, getCurrentAddr);
mkHook(ForeachHint.MoveNextAddressIndex + 1, moveNextAddr);
mkHook(ForeachHint.DisposeAddressIndex + 1, disposeAddr);
} // else nothing
}
public override AstGetSet GetCopy()
{
var copy = new AstGetSetMemberAccess(File, Line, Column, Call, Subject, Id);
CopyBaseMembers(copy);
return copy;
}