private DecisionTree AddByValue(DecisionTree.ByValue byValue, BoundConstantPattern value, DecisionMaker makeDecision)
{
Debug.Assert(value.Value.Type.Equals(byValue.Type, TypeCompareKind.IgnoreDynamicAndTupleNames));
if (byValue.Default != null)
{
return(AddByValue(byValue.Default, value, makeDecision));
}
// For error recovery, to avoid "unreachable code" diagnostics when there is a bad case
// label, we use the case label itself as the value key.
object valueKey = value.ConstantValue?.Value ?? value;
DecisionTree valueDecision;
if (byValue.ValueAndDecision.TryGetValue(valueKey, out valueDecision))
{
valueDecision = Add(valueDecision, makeDecision);
}
else
{
valueDecision = makeDecision(byValue.Expression, byValue.Type);
byValue.ValueAndDecision.Add(valueKey, valueDecision);
}
if (byValue.Type.SpecialType == SpecialType.System_Boolean &&
byValue.ValueAndDecision.Count == 2 &&
byValue.ValueAndDecision.Values.All(d => d.MatchIsComplete))
{
byValue.MatchIsComplete = true;
}
return(valueDecision);
}
private DecisionTree AddByValue(DecisionTree.ByValue byValue, BoundConstantPattern value, DecisionMaker makeDecision)
{
Debug.Assert(value.Value.Type.Equals(byValue.Type, TypeCompareKind.IgnoreDynamicAndTupleNames | TypeCompareKind.IgnoreNullableModifiersForReferenceTypes));
if (byValue.Default != null)
{
return(AddByValue(byValue.Default, value, makeDecision));
}
Debug.Assert(value.ConstantValue != null);
object valueKey = value.ConstantValue.Value;
DecisionTree valueDecision;
if (byValue.ValueAndDecision.TryGetValue(valueKey, out valueDecision))
{
valueDecision = Add(valueDecision, makeDecision);
}
else
{
valueDecision = makeDecision(byValue.Expression, byValue.Type);
byValue.ValueAndDecision.Add(valueKey, valueDecision);
}
if (byValue.Type.SpecialType == SpecialType.System_Boolean &&
byValue.ValueAndDecision.Count == 2 &&
byValue.ValueAndDecision.Values.All(d => d.MatchIsComplete))
{
byValue.MatchIsComplete = true;
}
return(valueDecision);
}
private void LowerConstantValueDecision(DecisionTree.ByValue byValue)
{
var value = byValue.Expression.ConstantValue.Value;
Debug.Assert(value != null);
// because we are switching on a constant, the decision tree builder does not produce a (nonempty) ByValue
Debug.Assert(byValue.ValueAndDecision.Count == 0);
LowerDecisionTree(byValue.Expression, byValue.Default);
}
private void LowerBooleanSwitch(DecisionTree.ByValue byValue)
{
switch (byValue.ValueAndDecision.Count)
{
case 0:
{
// this should have been handled in the caller.
throw ExceptionUtilities.Unreachable;
}
case 1:
{
DecisionTree decision;
bool onBoolean = byValue.ValueAndDecision.TryGetValue(true, out decision);
if (!onBoolean)
{
byValue.ValueAndDecision.TryGetValue(false, out decision);
}
Debug.Assert(decision != null);
var onOther = _factory.GenerateLabel("on" + !onBoolean);
_loweredDecisionTree.Add(_factory.ConditionalGoto(byValue.Expression, onOther, !onBoolean));
LowerDecisionTree(byValue.Expression, decision);
// if we fall through here, that means the match was not complete and we invoke the default part
_loweredDecisionTree.Add(_factory.Label(onOther));
LowerDecisionTree(byValue.Expression, byValue.Default);
break;
}
case 2:
{
DecisionTree trueDecision, falseDecision;
bool hasTrue = byValue.ValueAndDecision.TryGetValue(true, out trueDecision);
bool hasFalse = byValue.ValueAndDecision.TryGetValue(false, out falseDecision);
Debug.Assert(hasTrue && hasFalse);
var tryAnother = _factory.GenerateLabel("tryAnother");
var onFalse = _factory.GenerateLabel("onFalse");
_loweredDecisionTree.Add(_factory.ConditionalGoto(byValue.Expression, onFalse, false));
LowerDecisionTree(byValue.Expression, trueDecision);
_loweredDecisionTree.Add(_factory.Goto(tryAnother));
_loweredDecisionTree.Add(_factory.Label(onFalse));
LowerDecisionTree(byValue.Expression, falseDecision);
_loweredDecisionTree.Add(_factory.Label(tryAnother));
// if both true and false (i.e. all values) are fully handled, there should be no default.
Debug.Assert(!trueDecision.MatchIsComplete || !falseDecision.MatchIsComplete || byValue.Default == null);
LowerDecisionTree(byValue.Expression, byValue.Default);
break;
}
default:
throw ExceptionUtilities.UnexpectedValue(byValue.ValueAndDecision.Count);
}
}
private void LowerConstantValueDecision(DecisionTree.ByValue byValue)
{
var value = byValue.Expression.ConstantValue.Value;
Debug.Assert(value != null);
DecisionTree onValue;
if (byValue.ValueAndDecision.TryGetValue(value, out onValue))
{
LowerDecisionTree(byValue.Expression, onValue);
if (onValue.MatchIsComplete)
{
return;
}
}
LowerDecisionTree(byValue.Expression, byValue.Default);
}
private DecisionTree Add(DecisionTree.ByValue byValue, DecisionMaker makeDecision)
{
DecisionTree result;
if (byValue.Default != null)
{
result = Add(byValue.Default, makeDecision);
}
else
{
result = byValue.Default = makeDecision(byValue.Expression, byValue.Type);
}
if (byValue.Default.MatchIsComplete)
{
byValue.MatchIsComplete = true;
}
return(result);
}
private void LowerDecisionTree(DecisionTree.ByValue byValue)
{
if (byValue.Expression.ConstantValue != null)
{
LowerConstantValueDecision(byValue);
return;
}
if (byValue.ValueAndDecision.Count == 0)
{
LowerDecisionTree(byValue.Expression, byValue.Default);
return;
}
if (byValue.Type.SpecialType == SpecialType.System_Boolean)
{
LowerBooleanSwitch(byValue);
}
else
{
LowerBasicSwitch(byValue);
}
}
private DecisionTree AddByValue(DecisionTree.ByType byType, BoundConstantPattern value, DecisionMaker makeDecision)
{
if (byType.Default != null)
{
try
{
return(AddByValue(byType.Default, value, makeDecision));
}
finally
{
if (byType.Default.MatchIsComplete)
{
// This code may be unreachable due to https://github.com/dotnet/roslyn/issues/16878
byType.MatchIsComplete = true;
}
}
}
if (value.ConstantValue == ConstantValue.Null)
{
// This should not occur, as the caller will have invoked AddByNull instead.
throw ExceptionUtilities.Unreachable;
}
if ((object)value.Value.Type == null)
{
return(null);
}
foreach (var kvp in byType.TypeAndDecision)
{
var matchedType = kvp.Key;
var decision = kvp.Value;
// See if the test is already subsumed
switch (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics))
{
case true:
if (decision.MatchIsComplete)
{
return(null);
}
continue;
case false:
case null:
continue;
}
}
DecisionTree forType = null;
// This new type test should logically be last. However it might be the same type as the one that is already
// last. In that case we can produce better code by piggy-backing our new case on to the last decision.
// Also, the last one might be a non-overlapping type, in which case we can piggy-back onto the second-last
// type test.
for (int i = byType.TypeAndDecision.Count - 1; i >= 0; i--)
{
var kvp = byType.TypeAndDecision[i];
var matchedType = kvp.Key;
var decision = kvp.Value;
if (matchedType.Equals(value.Value.Type, TypeCompareKind.IgnoreDynamicAndTupleNames))
{
forType = decision;
break;
}
else if (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics) != false)
{
// because there is overlap, we cannot reuse some earlier entry
break;
}
}
// if we did not piggy-back, then create a new decision tree node for the type.
if (forType == null)
{
var type = value.Value.Type;
var localSymbol = new SynthesizedLocal(_enclosingSymbol as MethodSymbol, type, SynthesizedLocalKind.PatternMatching, Syntax, false, RefKind.None);
var narrowedExpression = new BoundLocal(Syntax, localSymbol, null, type);
forType = new DecisionTree.ByValue(narrowedExpression, value.Value.Type.TupleUnderlyingTypeOrSelf(), localSymbol);
byType.TypeAndDecision.Add(new KeyValuePair <TypeSymbol, DecisionTree>(value.Value.Type, forType));
}
return(AddByValue(forType, value, makeDecision));
}
// For switch statements, we have an option of completely rewriting the switch header
// and switch sections into simpler constructs, i.e. we can rewrite the switch header
// using bound conditional goto statements and the rewrite the switch sections into
// bound labeled statements.
//
// However, all the logic for emitting the switch jump tables is language agnostic
// and includes IL optimizations. Hence we delay the switch jump table generation
// till the emit phase. This way we also get additional benefit of sharing this code
// between both VB and C# compilers.
//
// For string switch statements, we need to determine if we are generating a hash
// table based jump table or a non hash jump table, i.e. linear string comparisons
// with each case label. We use the Dev10 Heuristic to determine this
// (see SwitchStringJumpTableEmitter.ShouldGenerateHashTableSwitch() for details).
// If we are generating a hash table based jump table, we use a simple
// hash function to hash the string constants corresponding to the case labels.
// See SwitchStringJumpTableEmitter.ComputeStringHash().
// We need to emit this same function to compute the hash value into the compiler generated
// <PrivateImplementationDetails> class.
// If we have at least one string switch statement in a module that needs a
// hash table based jump table, we generate a single public string hash synthesized method
// that is shared across the module.
private void LowerBasicSwitch(DecisionTree.ByValue byValue)
{
var switchSections = ArrayBuilder <BoundSwitchSection> .GetInstance();
var noValueMatches = _factory.GenerateLabel("noValueMatches");
var underlyingSwitchType = byValue.Type.IsEnumType() ? byValue.Type.GetEnumUnderlyingType() : byValue.Type;
foreach (var vd in byValue.ValueAndDecision)
{
var value = vd.Key;
var decision = vd.Value;
var constantValue = ConstantValue.Create(value, underlyingSwitchType.SpecialType);
var constantExpression = new BoundLiteral(_factory.Syntax, constantValue, underlyingSwitchType);
var label = _factory.GenerateLabel("case+" + value);
var switchLabel = new BoundSwitchLabel(_factory.Syntax, label, constantExpression, constantValue);
var forValue = ArrayBuilder <BoundStatement> .GetInstance();
LowerDecisionTree(byValue.Expression, decision, forValue);
if (!decision.MatchIsComplete)
{
forValue.Add(_factory.Goto(noValueMatches));
}
var section = new BoundSwitchSection(_factory.Syntax, ImmutableArray.Create(switchLabel), forValue.ToImmutableAndFree());
switchSections.Add(section);
}
var rewrittenSections = switchSections.ToImmutableAndFree();
MethodSymbol stringEquality = null;
if (underlyingSwitchType.SpecialType == SpecialType.System_String)
{
_localRewriter.EnsureStringHashFunction(rewrittenSections, _factory.Syntax);
stringEquality = _localRewriter.UnsafeGetSpecialTypeMethod(_factory.Syntax, SpecialMember.System_String__op_Equality);
}
// The BoundSwitchStatement requires a constant target when there are no sections, so we accomodate that here.
var constantTarget = rewrittenSections.IsEmpty ? noValueMatches : null;
var switchStatement = new BoundSwitchStatement(
_factory.Syntax, null, _factory.Convert(underlyingSwitchType, byValue.Expression),
constantTarget,
ImmutableArray <LocalSymbol> .Empty, ImmutableArray <LocalFunctionSymbol> .Empty,
rewrittenSections, noValueMatches, stringEquality);
// The bound switch statement implicitly defines the label noValueMatches at the end, so we do not add it explicitly.
switch (underlyingSwitchType.SpecialType)
{
case SpecialType.System_Boolean:
// boolean switch is handled in LowerBooleanSwitch, not here.
throw ExceptionUtilities.Unreachable;
case SpecialType.System_String:
case SpecialType.System_Byte:
case SpecialType.System_Char:
case SpecialType.System_Int16:
case SpecialType.System_Int32:
case SpecialType.System_Int64:
case SpecialType.System_SByte:
case SpecialType.System_UInt16:
case SpecialType.System_UInt32:
case SpecialType.System_UInt64:
{
// emit knows how to efficiently generate code for these kinds of switches.
_loweredDecisionTree.Add(switchStatement);
break;
}
default:
{
// other types, such as float, double, and decimal, are not currently
// handled by emit and must be lowered here.
_loweredDecisionTree.Add(LowerNonprimitiveSwitch(switchStatement));
break;
}
}
LowerDecisionTree(byValue.Expression, byValue.Default);
}
private DecisionTree AddByValue(DecisionTree.ByType byType, BoundConstantPattern value, DecisionMaker makeDecision)
{
if (byType.Default != null)
{
try
{
return(AddByValue(byType.Default, value, makeDecision));
}
finally
{
if (byType.Default.MatchIsComplete)
{
byType.MatchIsComplete = true;
}
}
}
if (value.ConstantValue == ConstantValue.Null)
{
return(byType.Expression.ConstantValue?.IsNull == false
? null : AddByNull((DecisionTree)byType, makeDecision));
}
foreach (var kvp in byType.TypeAndDecision)
{
var matchedType = kvp.Key;
var decision = kvp.Value;
// See if the test is already subsumed
switch (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics))
{
case true:
if (decision.MatchIsComplete)
{
return(null);
}
continue;
case false:
case null:
continue;
}
}
DecisionTree forType = null;
// Find an existing decision tree for the expression's type. Since this new test
// should logically be last, we look for the last one we can piggy-back it onto.
for (int i = byType.TypeAndDecision.Count - 1; i >= 0 && forType == null; i--)
{
var kvp = byType.TypeAndDecision[i];
var matchedType = kvp.Key;
var decision = kvp.Value;
if (matchedType.TupleUnderlyingTypeOrSelf() == value.Value.Type.TupleUnderlyingTypeOrSelf())
{
forType = decision;
break;
}
else if (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics) != false)
{
break;
}
}
if (forType == null)
{
var type = value.Value.Type;
var localSymbol = new SynthesizedLocal(_enclosingSymbol as MethodSymbol, type, SynthesizedLocalKind.PatternMatchingTemp, Syntax, false, RefKind.None);
var narrowedExpression = new BoundLocal(Syntax, localSymbol, null, type);
forType = new DecisionTree.ByValue(narrowedExpression, value.Value.Type.TupleUnderlyingTypeOrSelf(), localSymbol);
byType.TypeAndDecision.Add(new KeyValuePair <TypeSymbol, DecisionTree>(value.Value.Type, forType));
}
return(AddByValue(forType, value, makeDecision));
}
private DecisionTree AddByValue(DecisionTree.ByType byType, BoundConstantPattern value, DecisionMaker makeDecision)
{
if (byType.Default != null)
{
try
{
return(AddByValue(byType.Default, value, makeDecision));
}
finally
{
if (byType.Default.MatchIsComplete)
{
// This code may be unreachable due to https://github.com/dotnet/roslyn/issues/16878
byType.MatchIsComplete = true;
}
}
}
if (value.ConstantValue == ConstantValue.Null)
{
// This should not occur, as the caller will have invoked AddByNull instead.
throw ExceptionUtilities.Unreachable;
}
if ((object)value.Value.Type == null || value.ConstantValue == null)
{
return(null);
}
foreach (var kvp in byType.TypeAndDecision)
{
var matchedType = kvp.Key;
var decision = kvp.Value;
// See if the test is already subsumed
switch (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics))
{
case true:
if (decision.MatchIsComplete)
{
// Subsumed case have been eliminated by semantic analysis.
Debug.Assert(false);
return(null);
}
continue;
case false:
case null:
continue;
}
}
DecisionTree forType = null;
// This new type test should logically be last. However it might be the same type as the one that is already
// last. In that case we can produce better code by piggy-backing our new case on to the last decision.
// Also, the last one might be a non-overlapping type, in which case we can piggy-back onto the second-last
// type test.
for (int i = byType.TypeAndDecision.Count - 1; i >= 0; i--)
{
var kvp = byType.TypeAndDecision[i];
var matchedType = kvp.Key;
var decision = kvp.Value;
if (matchedType.Equals(value.Value.Type, TypeCompareKind.IgnoreDynamicAndTupleNames | TypeCompareKind.IgnoreNullableModifiersForReferenceTypes))
{
forType = decision;
break;
}
switch (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics))
{
case true:
if (decision.MatchIsComplete)
{
// we should have reported this case as subsumed already.
Debug.Assert(false);
return(null);
}
else
{
goto case null;
}
case false:
continue;
case null:
// because there is overlap, we cannot reuse some earlier entry
goto noReuse;
}
}
noReuse :;
// if we did not piggy-back, then create a new decision tree node for the type.
if (forType == null)
{
var type = value.Value.Type;
if (byType.Type.Equals(type, TypeCompareKind.AllIgnoreOptions))
{
// reuse the input expression when we have an equivalent type to reduce the number of generated temps
forType = new DecisionTree.ByValue(byType.Expression, type.TupleUnderlyingTypeOrSelf(), null);
}
else
{
var narrowedExpression = GetBoundPatternMatchingLocal(type);
forType = new DecisionTree.ByValue(narrowedExpression, type.TupleUnderlyingTypeOrSelf(), narrowedExpression.LocalSymbol);
}
byType.TypeAndDecision.Add(new KeyValuePair <TypeSymbol, DecisionTree>(type, forType));
}
return(AddByValue(forType, value, makeDecision));
}
private DecisionTree AddByValue(DecisionTree.ByType byType, BoundConstantPattern value, DecisionMaker makeDecision)
{
if (byType.Default != null)
{
try
{
return AddByValue(byType.Default, value, makeDecision);
}
finally
{
if (byType.Default.MatchIsComplete)
{
byType.MatchIsComplete = true;
}
}
}
if (value.ConstantValue == ConstantValue.Null)
{
return byType.Expression.ConstantValue?.IsNull == false
? null : AddByNull((DecisionTree)byType, makeDecision);
}
foreach (var kvp in byType.TypeAndDecision)
{
var matchedType = kvp.Key;
var decision = kvp.Value;
// See if the test is already subsumed
switch (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics))
{
case true:
if (decision.MatchIsComplete)
{
return null;
}
continue;
case false:
case null:
continue;
}
}
DecisionTree forType = null;
// Find an existing decision tree for the expression's type. Since this new test
// should logically be last, we look for the last one we can piggy-back it onto.
for (int i = byType.TypeAndDecision.Count - 1; i >= 0 && forType == null; i--)
{
var kvp = byType.TypeAndDecision[i];
var matchedType = kvp.Key;
var decision = kvp.Value;
if (matchedType.TupleUnderlyingTypeOrSelf() == value.Value.Type.TupleUnderlyingTypeOrSelf())
{
forType = decision;
break;
}
else if (ExpressionOfTypeMatchesPatternType(value.Value.Type, matchedType, ref _useSiteDiagnostics) != false)
{
break;
}
}
if (forType == null)
{
var type = value.Value.Type;
var localSymbol = new SynthesizedLocal(_enclosingSymbol as MethodSymbol, type, SynthesizedLocalKind.PatternMatchingTemp, Syntax, false, RefKind.None);
var narrowedExpression = new BoundLocal(Syntax, localSymbol, null, type);
forType = new DecisionTree.ByValue(narrowedExpression, value.Value.Type.TupleUnderlyingTypeOrSelf(), localSymbol);
byType.TypeAndDecision.Add(new KeyValuePair<TypeSymbol, DecisionTree>(value.Value.Type, forType));
}
return AddByValue(forType, value, makeDecision);
}
