/// <summary>
/// Return the boolean expression to be evaluated for the given test. Returns `null` if the test is trivially true.
/// </summary>
protected BoundExpression LowerTest(BoundDagTest test)
{
_factory.Syntax = test.Syntax;
BoundExpression input = _tempAllocator.GetTemp(test.Input);
switch (test)
{
case BoundDagNonNullTest d:
return(_localRewriter.MakeNullCheck(d.Syntax, input, input.Type.IsNullableType() ? BinaryOperatorKind.NullableNullNotEqual : BinaryOperatorKind.NotEqual));
case BoundDagTypeTest d:
// Note that this tests for non-null as a side-effect. We depend on that to sometimes avoid the null check.
return(_factory.Is(input, d.Type));
case BoundDagNullTest d:
return(_localRewriter.MakeNullCheck(d.Syntax, input, input.Type.IsNullableType() ? BinaryOperatorKind.NullableNullEqual : BinaryOperatorKind.Equal));
case BoundDagValueTest d:
Debug.Assert(!input.Type.IsNullableType());
return(MakeEqual(_localRewriter.MakeLiteral(d.Syntax, d.Value, input.Type), input));
default:
throw ExceptionUtilities.UnexpectedValue(test);
}
}
private BoundStatement LowerNonprimitiveSwitch(BoundSwitchStatement switchStatement)
{
// Here we handle "other" types, such as float, double, and decimal, by
// lowering the BoundSwitchStatement.
// We compare the constant values using value.Equals(input), using ordinary
// overload resolution. Note that we cannot and do not rely on switching
// on the hash code, as it may not be consistent with the behavior of Equals;
// see https://github.com/dotnet/coreclr/issues/6237. Also, the hash code is
// not guaranteed to be the same on the compilation platform as the runtime
// platform.
// CONSIDER: can we improve the quality of the code using comparisons, like
// we do for other numeric types, by generating a series of tests
// that use divide-and-conquer to efficiently find a matching value?
// If so, we should use the BoundSwitchStatement and do that in emit.
// Moreover, we should be able to use `==` rather than `.Equals`
// for cases (such as non-NaN) where we know the result to be the same.
var rewrittenSections = switchStatement.SwitchSections;
var expression = switchStatement.Expression;
var noValueMatches = switchStatement.BreakLabel;
Debug.Assert(switchStatement.LoweredPreambleOpt == null);
Debug.Assert(switchStatement.InnerLocals.IsDefaultOrEmpty);
Debug.Assert(switchStatement.InnerLocalFunctions.IsDefaultOrEmpty);
Debug.Assert(switchStatement.StringEquality == null);
LabelSymbol nextLabel = null;
var builder = ArrayBuilder <BoundStatement> .GetInstance();
foreach (var section in rewrittenSections)
{
foreach (var boundSwitchLabel in section.SwitchLabels)
{
if (nextLabel != null)
{
builder.Add(_factory.Label(nextLabel));
}
nextLabel = _factory.GenerateLabel("failcase+" + section.SwitchLabels[0].ConstantValueOpt.Value);
Debug.Assert(boundSwitchLabel.ConstantValueOpt != null);
// generate (if (value.Equals(input)) goto label;
var literal = _localRewriter.MakeLiteral(_factory.Syntax, boundSwitchLabel.ConstantValueOpt, expression.Type);
var condition = _factory.InstanceCall(literal, "Equals", expression);
if (!condition.HasErrors && condition.Type.SpecialType != SpecialType.System_Boolean)
{
var call = (BoundCall)condition;
// '{1} {0}' has the wrong return type
_factory.Diagnostics.Add(ErrorCode.ERR_BadRetType, boundSwitchLabel.Syntax.GetLocation(), call.Method, call.Type);
}
builder.Add(_factory.ConditionalGoto(condition, boundSwitchLabel.Label, true));
builder.Add(_factory.Goto(nextLabel));
}
foreach (var boundSwitchLabel in section.SwitchLabels)
{
builder.Add(_factory.Label(boundSwitchLabel.Label));
}
builder.Add(_factory.Block(section.Statements));
// this location in the generated code in builder should not be reachable.
}
Debug.Assert(nextLabel != null);
builder.Add(_factory.Label(nextLabel));
builder.Add(_factory.Label(noValueMatches));
return(_factory.Block(builder.ToImmutableAndFree()));
}