// when two control points merge. Returns true if this state changed.
public bool Join(FlowAnalysisLocalState other)
{
this.Merge();
other.Merge();
this.Reachable |= other.Reachable;
return(this.Assigned.IntersectWith(other.Assigned));
}
/// <summary>
/// Visit a boolean condition expression, where we will be wanting AssignedWhenTrue and
/// AssignedWhenFalse.
/// </summary>
/// <param name="node"></param>
protected void VisitCondition(BoundExpression node)
{
Debug.Assert(!this.state.Assigned.IsNull);
Visit(node);
// We implement the foundational rules missing from the language specification:
// v is "definitely assigned when true" after a constant expression whose value is false.
// v is "definitely assigned when false" after a constant expression whose value is true.
// These rules are to be added to the language specification.
// It was the lack of these foundational rules that led to the invention of the concept
// of "unreachable expression" in the native compiler.
if (IsConstantTrue(node))
{
state.Merge();
this.state = new FlowAnalysisLocalState(this.state.Reachable, this.state.Assigned, BitArray.AllSet(nextVariableSlot));
}
else if (IsConstantFalse(node))
{
state.Merge();
this.state = new FlowAnalysisLocalState(this.state.Reachable, BitArray.AllSet(nextVariableSlot), this.state.Assigned);
}
else
{
state.Split();
}
}
public override object VisitConditionalOperator(BoundConditionalOperator node, object arg)
{
VisitCondition(node.Condition);
var consequenceState = new FlowAnalysisLocalState(this.state.Reachable, this.state.AssignedWhenTrue);
var alternativeState = new FlowAnalysisLocalState(this.state.Reachable, this.state.AssignedWhenFalse);
this.state = consequenceState;
Visit(node.Consequence);
consequenceState = this.state;
this.state = alternativeState;
Visit(node.Alternative);
alternativeState = this.state;
if (IsConstantTrue(node.Condition))
{
this.state = consequenceState;
// it may be a boolean state at this point.
}
else if (IsConstantFalse(node.Condition))
{
this.state = alternativeState;
// it may be a boolean state at this point.
}
else
{
// is may not be a boolean state at this point (5.3.3.28)
this.state = consequenceState;
this.state.Join(alternativeState);
}
return(null);
}
public override object VisitForStatement(BoundForStatement node, object arg)
{
VisitStatement(node.Initializer);
LoopHead(node);
bool isTrue;
bool isFalse;
if (node.Condition != null)
{
isFalse = IsConstantFalse(node.Condition);
isTrue = IsConstantTrue(node.Condition);
VisitCondition(node.Condition);
}
else
{
isTrue = true;
isFalse = false;
this.state = new FlowAnalysisLocalState(this.state.Reachable, this.state.Assigned, BitArray.AllSet(nextVariableSlot));
}
var bodyState = new FlowAnalysisLocalState(this.state.Reachable && !isFalse, this.state.AssignedWhenTrue);
var breakState = new FlowAnalysisLocalState(this.state.Reachable && !isTrue, this.state.AssignedWhenFalse);
var oldPendingBranches = this.pendingBranches;
this.pendingBranches = ArrayBuilder <PendingBranch> .GetInstance();
this.state = bodyState;
VisitStatement(node.Body);
ResolveContinues(node.ContinueLabel);
VisitStatement(node.Increment);
LoopTail(node);
ResolveBreaks(oldPendingBranches, breakState, node.BreakLabel);
return(null);
}
/// <summary>
/// Return the flow analysis state associated with a label.
/// </summary>
/// <param name="label"></param>
/// <returns></returns>
FlowAnalysisLocalState?LabelState(LabelSymbol label)
{
FlowAnalysisLocalState?result;
if (labels.TryGetValue(label, out result))
{
return(result);
}
result = FlowAnalysisLocalState.UnreachableState(nextVariableSlot);
labels.Add(label, result);
return(result);
}
public override object VisitWhileStatement(BoundWhileStatement node, object arg)
{
// while (node.Condition) { node.Body; node.ContinueLabel: } node.BreakLabel:
LoopHead(node);
VisitCondition(node.Condition);
var bodyState = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantFalse(node.Condition), this.state.AssignedWhenTrue);
var breakState = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantTrue(node.Condition), this.state.AssignedWhenFalse);
var oldPendingBranches = SavePending();
this.state = bodyState;
VisitStatement(node.Body);
ResolveContinues(node.ContinueLabel);
LoopTail(node);
ResolveBreaks(oldPendingBranches, breakState, node.BreakLabel);
return(null);
}
public override object VisitDoStatement(BoundDoStatement node, object arg)
{
// do { statements; node.ContinueLabel: } while (node.Condition) node.BreakLabel:
var oldPendingBranches = this.pendingBranches;
this.pendingBranches = ArrayBuilder <PendingBranch> .GetInstance();
LoopHead(node);
VisitStatement(node.Body);
ResolveContinues(node.ContinueLabel);
VisitCondition(node.Condition);
var breakState = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantTrue(node.Condition), this.state.AssignedWhenFalse);
this.state = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantFalse(node.Condition), this.state.AssignedWhenTrue);
LoopTail(node);
ResolveBreaks(oldPendingBranches, breakState, node.BreakLabel);
return(null);
}
public override object VisitIfStatement(BoundIfStatement node, object arg)
{
// 5.3.3.5 If statements
VisitCondition(node.Condition);
var trueState = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantFalse(node.Condition), state.AssignedWhenTrue);
var falseState = new FlowAnalysisLocalState(this.state.Reachable && !IsConstantTrue(node.Condition), state.AssignedWhenFalse);
this.state = trueState;
VisitStatement(node.Consequence);
trueState = this.state;
this.state = falseState;
if (node.Alternative != null)
{
VisitStatement(node.Alternative);
}
this.state.Join(trueState);
return(null);
}
/// <summary>
/// Used to resolve break statements in each statement form that has a break statement
/// (loops, switch).
/// </summary>
/// <param name="oldPendingBranches"></param>
/// <param name="breakState"></param>
/// <param name="breakLabel"></param>
private void ResolveBreaks(ArrayBuilder <PendingBranch> oldPendingBranches, FlowAnalysisLocalState breakState, LabelSymbol breakLabel)
{
foreach (var pending in this.pendingBranches)
{
switch (pending.Branch.Kind)
{
case BoundKind.BreakStatement:
Debug.Assert((pending.Branch as BoundBreakStatement).Label == breakLabel);
breakState.Join(pending.State);
break;
default:
oldPendingBranches.Add(pending);
break;
}
}
this.pendingBranches.Free();
this.pendingBranches = oldPendingBranches;
this.state = breakState;
}
/// <summary>
/// Set the current state to one that indicates that it is unreachable.
/// </summary>
protected void SetUnreachable()
{
this.state = FlowAnalysisLocalState.UnreachableState(this.nextVariableSlot);
}
/// <summary>
/// Perform a single pass of flow analysis. Note that after this pass,
/// this.backwardBranchChanged indicates if a further pass is required.
/// </summary>
protected virtual void Scan()
{
// the entry point of a method is assumed reachable
state = FlowAnalysisLocalState.ReachableState();
// label out parameters as not assigned.
foreach (var parameter in method.Parameters)
{
if (parameter.RefKind == RefKind.Out)
{
SetSlotState(MakeSlot(parameter), initiallyAssignedVariables != null && initiallyAssignedVariables.Contains(parameter));
}
else
{
// this code has no effect except in the region analysis APIs, which assign
// variable slots to all parameters.
int slot = VariableSlot(parameter);
SetSlotState(slot, true);
}
}
// TODO: if this is the body of an initial struct constructor, mark "this" as unassigned.
this.backwardBranchChanged = false;
if (this.Diagnostics != null)
{
this.Diagnostics.Free();
}
this.Diagnostics = DiagnosticBag.GetInstance(); // clear reported diagnostics
this.alreadyReported = BitArray.Empty; // no variables yet reported unassigned
VisitStatement(block);
// check that each local variable is used somewhere (or warn if it isn't)
foreach (var symbol in variableBySlot)
{
if (symbol != null && symbol.Kind == SymbolKind.Local && !readVariables.Contains(symbol))
{
Diagnostics.Add(writtenVariables.Contains(symbol) ? ErrorCode.WRN_UnreferencedVarAssg : ErrorCode.WRN_UnreferencedVar, symbol.Locations[0], symbol.Name);
}
}
// check that each out parameter is definitely assigned at the end of the method if
// there's more than one location, then the method is partial and we prefer to report an
// out parameter in partial method error
if (method.Locations.Count == 1)
{
foreach (ParameterSymbol parameter in method.Parameters)
{
if (parameter.RefKind == RefKind.Out)
{
var slot = VariableSlot(parameter);
if (!state.IsAssigned(slot))
{
ReportUnassignedOutParameter(parameter, null, method.Locations[0]);
}
foreach (PendingBranch returnBranch in pendingBranches)
{
if (!returnBranch.State.IsAssigned(slot))
{
ReportUnassignedOutParameter(parameter, returnBranch.Branch.Syntax, null);
}
}
}
}
}
// TODO: handle "this" in struct constructor.
}
// when two control points merge. Returns true if this state changed.
public bool Join(FlowAnalysisLocalState other)
{
this.Merge();
other.Merge();
this.Reachable |= other.Reachable;
return this.Assigned.IntersectWith(other.Assigned);
}
/// <summary>
/// Used to resolve break statements in each statement form that has a break statement
/// (loops, switch).
/// </summary>
/// <param name="oldPendingBranches"></param>
/// <param name="breakState"></param>
/// <param name="breakLabel"></param>
private void ResolveBreaks(ArrayBuilder<PendingBranch> oldPendingBranches, FlowAnalysisLocalState breakState, LabelSymbol breakLabel)
{
foreach (var pending in this.pendingBranches)
{
switch (pending.Branch.Kind)
{
case BoundKind.BreakStatement:
Debug.Assert((pending.Branch as BoundBreakStatement).Label == breakLabel);
breakState.Join(pending.State);
break;
default:
oldPendingBranches.Add(pending);
break;
}
}
this.pendingBranches.Free();
this.pendingBranches = oldPendingBranches;
this.state = breakState;
}
/// <summary>
/// Visit a boolean condition expression, where we will be wanting AssignedWhenTrue and
/// AssignedWhenFalse.
/// </summary>
/// <param name="node"></param>
protected void VisitCondition(BoundExpression node)
{
Debug.Assert(!this.state.Assigned.IsNull);
Visit(node);
// We implement the foundational rules missing from the language specification:
// v is "definitely assigned when true" after a constant expression whose value is false.
// v is "definitely assigned when false" after a constant expression whose value is true.
// These rules are to be added to the language specification.
// It was the lack of these foundational rules that led to the invention of the concept
// of "unreachable expression" in the native compiler.
if (IsConstantTrue(node))
{
state.Merge();
this.state = new FlowAnalysisLocalState(this.state.Reachable, this.state.Assigned, BitArray.AllSet(nextVariableSlot));
}
else if (IsConstantFalse(node))
{
state.Merge();
this.state = new FlowAnalysisLocalState(this.state.Reachable, BitArray.AllSet(nextVariableSlot), this.state.Assigned);
}
else
{
state.Split();
}
}
/// <summary>
/// Set the current state to one that indicates that it is unreachable.
/// </summary>
protected void SetUnreachable()
{
this.state = FlowAnalysisLocalState.UnreachableState(this.nextVariableSlot);
}
/// <summary>
/// Perform a single pass of flow analysis. Note that after this pass,
/// this.backwardBranchChanged indicates if a further pass is required.
/// </summary>
protected virtual void Scan()
{
// the entry point of a method is assumed reachable
state = FlowAnalysisLocalState.ReachableState();
// label out parameters as not assigned.
foreach (var parameter in method.Parameters)
{
if (parameter.RefKind == RefKind.Out)
{
SetSlotState(MakeSlot(parameter), initiallyAssignedVariables != null && initiallyAssignedVariables.Contains(parameter));
}
else
{
// this code has no effect except in the region analysis APIs, which assign
// variable slots to all parameters.
int slot = VariableSlot(parameter);
SetSlotState(slot, true);
}
}
// TODO: if this is the body of an initial struct constructor, mark "this" as unassigned.
this.backwardBranchChanged = false;
if (this.Diagnostics != null)
this.Diagnostics.Free();
this.Diagnostics = DiagnosticBag.GetInstance(); // clear reported diagnostics
this.alreadyReported = BitArray.Empty; // no variables yet reported unassigned
VisitStatement(block);
// check that each local variable is used somewhere (or warn if it isn't)
foreach (var symbol in variableBySlot)
{
if (symbol != null && symbol.Kind == SymbolKind.Local && !readVariables.Contains(symbol))
{
Diagnostics.Add(writtenVariables.Contains(symbol) ? ErrorCode.WRN_UnreferencedVarAssg : ErrorCode.WRN_UnreferencedVar, symbol.Locations[0], symbol.Name);
}
}
// check that each out parameter is definitely assigned at the end of the method if
// there's more than one location, then the method is partial and we prefer to report an
// out parameter in partial method error
if (method.Locations.Count == 1)
{
foreach (ParameterSymbol parameter in method.Parameters)
{
if (parameter.RefKind == RefKind.Out)
{
var slot = VariableSlot(parameter);
if (!state.IsAssigned(slot))
{
ReportUnassignedOutParameter(parameter, null, method.Locations[0]);
}
foreach (PendingBranch returnBranch in pendingBranches)
{
if (!returnBranch.State.IsAssigned(slot))
{
ReportUnassignedOutParameter(parameter, returnBranch.Branch.Syntax, null);
}
}
}
}
}
// TODO: handle "this" in struct constructor.
}
