ILInstruction Lift(IfInstruction ifInst, ILInstruction trueInst, ILInstruction falseInst)
{
ILInstruction condition = ifInst.Condition;
while (condition.MatchLogicNot(out var arg))
{
condition = arg;
Swap(ref trueInst, ref falseInst);
}
if (AnalyzeCondition(condition))
{
// (v1 != null && ... && vn != null) ? trueInst : falseInst
// => normal lifting
return(LiftNormal(trueInst, falseInst, ilrange: ifInst.ILRange));
}
if (condition is Comp comp && !comp.IsLifted && !comp.Kind.IsEqualityOrInequality())
{
// This might be a C#-style lifted comparison
// (C# checks the underlying value before checking the HasValue bits)
if (falseInst.MatchLdcI4(0) && AnalyzeCondition(trueInst))
{
// comp(lhs, rhs) ? (v1 != null && ... && vn != null) : false
// => comp.lifted[C#](lhs, rhs)
return(LiftCSharpComparison(comp, comp.Kind));
}
else if (trueInst.MatchLdcI4(0) && AnalyzeCondition(falseInst))
{
// comp(lhs, rhs) ? false : (v1 != null && ... && vn != null)
return(LiftCSharpComparison(comp, comp.Kind.Negate()));
}
}
return(null);
}
static bool IsNullOrZero(ILInstruction inst)
{
while (inst is Conv conv)
{
inst = conv.Argument;
}
return(inst.MatchLdcI4(0) || inst.MatchLdNull());
}
static bool IsNullOrZero(ILInstruction inst)
{
var conv = inst as Conv;
if (conv != null)
{
inst = conv.Argument;
}
return(inst.MatchLdcI4(0) || inst.MatchLdNull());
}
/// <summary>
/// Performs nullable lifting.
///
/// Produces a lifted instruction with semantics equivalent to:
/// (v1 != null && ... && vn != null) ? trueInst : falseInst,
/// where the v1,...,vn are the <c>this.nullableVars</c>.
/// If lifting fails, returns <c>null</c>.
/// </summary>
ILInstruction LiftNormal(ILInstruction trueInst, ILInstruction falseInst, Interval ilrange)
{
bool isNullCoalescingWithNonNullableFallback = false;
if (!MatchNullableCtor(trueInst, out var utype, out var exprToLift))
{
isNullCoalescingWithNonNullableFallback = true;
utype = context.TypeSystem.Compilation.FindType(trueInst.ResultType.ToKnownTypeCode());
exprToLift = trueInst;
if (nullableVars.Count == 1 && exprToLift.MatchLdLoc(nullableVars[0]))
{
// v.HasValue ? ldloc v : fallback
// => v ?? fallback
context.Step("v.HasValue ? v : fallback => v ?? fallback", trueInst);
return(new NullCoalescingInstruction(NullCoalescingKind.Nullable, trueInst, falseInst)
{
UnderlyingResultType = NullableType.GetUnderlyingType(nullableVars[0].Type).GetStackType(),
ILRange = ilrange
});
}
else if (trueInst is Call call && !call.IsLifted &&
CSharp.Resolver.CSharpOperators.IsComparisonOperator(call.Method) &&
call.Method.Name != "op_Equality" && call.Method.Name != "op_Inequality" &&
falseInst.MatchLdcI4(0))
{
// (v1 != null && ... && vn != null) ? call op_LessThan(lhs, rhs) : ldc.i4(0)
var liftedOperator = CSharp.Resolver.CSharpOperators.LiftUserDefinedOperator(call.Method);
if (liftedOperator != null)
{
var(left, right, bits) = DoLiftBinary(call.Arguments[0], call.Arguments[1]);
if (left != null && right != null && bits.All(0, nullableVars.Count))
{
return(new Call(liftedOperator)
{
Arguments = { left, right },
ConstrainedTo = call.ConstrainedTo,
ILRange = call.ILRange,
ILStackWasEmpty = call.ILStackWasEmpty,
IsTail = call.IsTail
});
}
}
}
}
ILInstruction lifted;
if (nullableVars.Count == 1 && MatchGetValueOrDefault(exprToLift, nullableVars[0]))
{
// v.HasValue ? call GetValueOrDefault(ldloca v) : fallback
// => conv.nop.lifted(ldloc v) ?? fallback
// This case is handled separately from DoLift() because
// that doesn't introduce nop-conversions.
context.Step("v.HasValue ? v.GetValueOrDefault() : fallback => v ?? fallback", trueInst);
var inputUType = NullableType.GetUnderlyingType(nullableVars[0].Type);
lifted = new LdLoc(nullableVars[0]);
if (!inputUType.Equals(utype) && utype.ToPrimitiveType() != PrimitiveType.None)
{
// While the ILAst allows implicit conversions between short and int
// (because both map to I4); it does not allow implicit conversions
// between short? and int? (structs of different types).
// So use 'conv.nop.lifted' to allow the conversion.
lifted = new Conv(
lifted,
inputUType.GetStackType(), inputUType.GetSign(), utype.ToPrimitiveType(),
checkForOverflow: false,
isLifted: true
)
{
ILRange = ilrange
};
}
}
else
{
context.Step("NullableLiftingTransform.DoLift", trueInst);
BitSet bits;
(lifted, bits) = DoLift(exprToLift);
if (lifted == null)
{
return(null);
}
if (!bits.All(0, nullableVars.Count))
{
// don't lift if a nullableVar doesn't contribute to the result
return(null);
}
Debug.Assert(lifted is ILiftableInstruction liftable && liftable.IsLifted &&
liftable.UnderlyingResultType == exprToLift.ResultType);
}
if (isNullCoalescingWithNonNullableFallback)
{
lifted = new NullCoalescingInstruction(NullCoalescingKind.NullableWithValueFallback, lifted, falseInst)
{
UnderlyingResultType = exprToLift.ResultType,
ILRange = ilrange
};
}
else if (!MatchNull(falseInst, utype))
{
// Normal lifting, but the falseInst isn't `default(utype?)`
// => use the `??` operator to provide the fallback value.
lifted = new NullCoalescingInstruction(NullCoalescingKind.Nullable, lifted, falseInst)
{
UnderlyingResultType = exprToLift.ResultType,
ILRange = ilrange
};
}
return(lifted);
}
ILInstruction Lift(IfInstruction ifInst, ILInstruction trueInst, ILInstruction falseInst)
{
ILInstruction condition = ifInst.Condition;
while (condition.MatchLogicNot(out var arg))
{
condition = arg;
Swap(ref trueInst, ref falseInst);
}
if (AnalyzeCondition(condition))
{
// (v1 != null && ... && vn != null) ? trueInst : falseInst
// => normal lifting
return(LiftNormal(trueInst, falseInst, ilrange: ifInst.ILRange));
}
if (condition is Comp comp && !comp.IsLifted)
{
// This might be a C#-style lifted comparison
// (C# checks the underlying value before checking the HasValue bits)
if (comp.Kind.IsEqualityOrInequality())
{
// for equality/inequality, the HasValue bits must also compare equal/inequal
if (comp.Kind == ComparisonKind.Inequality)
{
// handle inequality by swapping one last time
Swap(ref trueInst, ref falseInst);
}
if (falseInst.MatchLdcI4(0))
{
// (a.GetValueOrDefault() == b.GetValueOrDefault()) ? (a.HasValue == b.HasValue) : false
// => a == b
return(LiftCSharpEqualityComparison(comp, ComparisonKind.Equality, trueInst));
}
else if (falseInst.MatchLdcI4(1))
{
// (a.GetValueOrDefault() == b.GetValueOrDefault()) ? (a.HasValue != b.HasValue) : true
// => a != b
return(LiftCSharpEqualityComparison(comp, ComparisonKind.Inequality, trueInst));
}
else if (IsGenericNewPattern(condition, trueInst, falseInst))
{
// (default(T) == null) ? Activator.CreateInstance<T>() : default(T)
// => Activator.CreateInstance<T>()
return(trueInst);
}
}
else
{
// Not (in)equality, but one of < <= > >=.
// Returns false unless all HasValue bits are true.
if (falseInst.MatchLdcI4(0) && AnalyzeCondition(trueInst))
{
// comp(lhs, rhs) ? (v1 != null && ... && vn != null) : false
// => comp.lifted[C#](lhs, rhs)
return(LiftCSharpComparison(comp, comp.Kind));
}
else if (trueInst.MatchLdcI4(0) && AnalyzeCondition(falseInst))
{
// comp(lhs, rhs) ? false : (v1 != null && ... && vn != null)
return(LiftCSharpComparison(comp, comp.Kind.Negate()));
}
}
}
ILVariable v;
if (MatchGetValueOrDefault(condition, out v) &&
NullableType.GetUnderlyingType(v.Type).IsKnownType(KnownTypeCode.Boolean))
{
if (MatchHasValueCall(trueInst, v) && falseInst.MatchLdcI4(0))
{
// v.GetValueOrDefault() ? v.HasValue : false
// ==> v == true
context.Step("NullableLiftingTransform: v == true", ifInst);
return(new Comp(ComparisonKind.Equality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v)
{
ILRange = trueInst.ILRange
},
new LdcI4(1)
{
ILRange = falseInst.ILRange
}
)
{
ILRange = ifInst.ILRange
});
}
else if (trueInst.MatchLdcI4(0) && MatchHasValueCall(falseInst, v))
{
// v.GetValueOrDefault() ? false : v.HasValue
// ==> v == false
context.Step("NullableLiftingTransform: v == false", ifInst);
return(new Comp(ComparisonKind.Equality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v)
{
ILRange = falseInst.ILRange
},
trueInst // LdcI4(0)
)
{
ILRange = ifInst.ILRange
});
}
else if (MatchNegatedHasValueCall(trueInst, v) && falseInst.MatchLdcI4(1))
{
// v.GetValueOrDefault() ? !v.HasValue : true
// ==> v != true
context.Step("NullableLiftingTransform: v != true", ifInst);
return(new Comp(ComparisonKind.Inequality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v)
{
ILRange = trueInst.ILRange
},
falseInst // LdcI4(1)
)
{
ILRange = ifInst.ILRange
});
}
else if (trueInst.MatchLdcI4(1) && MatchNegatedHasValueCall(falseInst, v))
{
// v.GetValueOrDefault() ? true : !v.HasValue
// ==> v != false
context.Step("NullableLiftingTransform: v != false", ifInst);
return(new Comp(ComparisonKind.Inequality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v)
{
ILRange = falseInst.ILRange
},
new LdcI4(0)
{
ILRange = trueInst.ILRange
}
)
{
ILRange = ifInst.ILRange
});
}
}
if (trueInst.MatchLdLoc(out v))
{
if (MatchNullableCtor(falseInst, out var utype, out var arg) &&
utype.IsKnownType(KnownTypeCode.Boolean) && arg.MatchLdcI4(0))
{
// condition ? v : (bool?)false
// => condition & v
context.Step("NullableLiftingTransform: 3vl.logic.and(bool, bool?)", ifInst);
return(new ThreeValuedLogicAnd(condition, trueInst)
{
ILRange = ifInst.ILRange
});
}
if (falseInst.MatchLdLoc(out var v2))
{
// condition ? v : v2
if (MatchThreeValuedLogicConditionPattern(condition, out var nullable1, out var nullable2))
{
// (nullable1.GetValueOrDefault() || (!nullable2.GetValueOrDefault() && !nullable1.HasValue)) ? v : v2
if (v == nullable1 && v2 == nullable2)
{
context.Step("NullableLiftingTransform: 3vl.logic.or(bool?, bool?)", ifInst);
return(new ThreeValuedLogicOr(trueInst, falseInst)
{
ILRange = ifInst.ILRange
});
}
else if (v == nullable2 && v2 == nullable1)
{
context.Step("NullableLiftingTransform: 3vl.logic.and(bool?, bool?)", ifInst);
return(new ThreeValuedLogicAnd(falseInst, trueInst)
{
ILRange = ifInst.ILRange
});
}
}
}
}
else if (falseInst.MatchLdLoc(out v))
{
if (MatchNullableCtor(trueInst, out var utype, out var arg) &&
utype.IsKnownType(KnownTypeCode.Boolean) && arg.MatchLdcI4(1))
{
// condition ? (bool?)true : v
// => condition | v
context.Step("NullableLiftingTransform: 3vl.logic.or(bool, bool?)", ifInst);
return(new ThreeValuedLogicOr(condition, falseInst)
{
ILRange = ifInst.ILRange
});
}
}
return(null);
}
/// <summary>
/// Main entry point for lifting; called by both the expression-transform
/// and the block transform.
/// </summary>
ILInstruction Lift(ILInstruction ifInst, ILInstruction condition, ILInstruction trueInst, ILInstruction falseInst)
{
// ifInst is usually the IfInstruction to which condition belongs;
// but can also be a BinaryNumericInstruction.
while (condition.MatchLogicNot(out var arg))
{
condition = arg;
ExtensionMethods.Swap(ref trueInst, ref falseInst);
}
if (context.Settings.NullPropagation && !NullPropagationTransform.IsProtectedIfInst(ifInst as IfInstruction))
{
var nullPropagated = new NullPropagationTransform(context)
.Run(condition, trueInst, falseInst)?.WithILRange(ifInst);
if (nullPropagated != null)
{
return(nullPropagated);
}
}
if (!context.Settings.LiftNullables)
{
return(null);
}
if (AnalyzeCondition(condition))
{
// (v1 != null && ... && vn != null) ? trueInst : falseInst
// => normal lifting
return(LiftNormal(trueInst, falseInst)?.WithILRange(ifInst));
}
if (MatchCompOrDecimal(condition, out var comp))
{
// This might be a C#-style lifted comparison
// (C# checks the underlying value before checking the HasValue bits)
if (comp.Kind.IsEqualityOrInequality())
{
// for equality/inequality, the HasValue bits must also compare equal/inequal
if (comp.Kind == ComparisonKind.Inequality)
{
// handle inequality by swapping one last time
ExtensionMethods.Swap(ref trueInst, ref falseInst);
}
if (falseInst.MatchLdcI4(0))
{
// (a.GetValueOrDefault() == b.GetValueOrDefault()) ? (a.HasValue == b.HasValue) : false
// => a == b
return(LiftCSharpEqualityComparison(comp, ComparisonKind.Equality, trueInst)
?? LiftCSharpUserEqualityComparison(comp, ComparisonKind.Equality, trueInst));
}
else if (falseInst.MatchLdcI4(1))
{
// (a.GetValueOrDefault() == b.GetValueOrDefault()) ? (a.HasValue != b.HasValue) : true
// => a != b
return(LiftCSharpEqualityComparison(comp, ComparisonKind.Inequality, trueInst)
?? LiftCSharpUserEqualityComparison(comp, ComparisonKind.Inequality, trueInst));
}
else if (IsGenericNewPattern(comp.Left, comp.Right, trueInst, falseInst))
{
// (default(T) == null) ? Activator.CreateInstance<T>() : default(T)
// => Activator.CreateInstance<T>()
return(trueInst);
}
}
else
{
// Not (in)equality, but one of < <= > >=.
// Returns false unless all HasValue bits are true.
if (falseInst.MatchLdcI4(0) && AnalyzeCondition(trueInst))
{
// comp(lhs, rhs) ? (v1 != null && ... && vn != null) : false
// => comp.lifted[C#](lhs, rhs)
return(LiftCSharpComparison(comp, comp.Kind));
}
else if (trueInst.MatchLdcI4(0) && AnalyzeCondition(falseInst))
{
// comp(lhs, rhs) ? false : (v1 != null && ... && vn != null)
return(LiftCSharpComparison(comp, comp.Kind.Negate()));
}
}
}
ILVariable v;
// Handle equality comparisons with bool?:
if (MatchGetValueOrDefault(condition, out v) &&
NullableType.GetUnderlyingType(v.Type).IsKnownType(KnownTypeCode.Boolean))
{
if (MatchHasValueCall(trueInst, v) && falseInst.MatchLdcI4(0))
{
// v.GetValueOrDefault() ? v.HasValue : false
// ==> v == true
context.Step("NullableLiftingTransform: v == true", ifInst);
return(new Comp(ComparisonKind.Equality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v).WithILRange(trueInst),
new LdcI4(1).WithILRange(falseInst)
).WithILRange(ifInst));
}
else if (trueInst.MatchLdcI4(0) && MatchHasValueCall(falseInst, v))
{
// v.GetValueOrDefault() ? false : v.HasValue
// ==> v == false
context.Step("NullableLiftingTransform: v == false", ifInst);
return(new Comp(ComparisonKind.Equality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v).WithILRange(falseInst),
trueInst // LdcI4(0)
).WithILRange(ifInst));
}
else if (MatchNegatedHasValueCall(trueInst, v) && falseInst.MatchLdcI4(1))
{
// v.GetValueOrDefault() ? !v.HasValue : true
// ==> v != true
context.Step("NullableLiftingTransform: v != true", ifInst);
return(new Comp(ComparisonKind.Inequality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v).WithILRange(trueInst),
falseInst // LdcI4(1)
).WithILRange(ifInst));
}
else if (trueInst.MatchLdcI4(1) && MatchNegatedHasValueCall(falseInst, v))
{
// v.GetValueOrDefault() ? true : !v.HasValue
// ==> v != false
context.Step("NullableLiftingTransform: v != false", ifInst);
return(new Comp(ComparisonKind.Inequality, ComparisonLiftingKind.CSharp,
StackType.I4, Sign.None,
new LdLoc(v).WithILRange(falseInst),
new LdcI4(0).WithILRange(trueInst)
).WithILRange(ifInst));
}
}
// Handle & and | on bool?:
if (trueInst.MatchLdLoc(out v))
{
if (MatchNullableCtor(falseInst, out var utype, out var arg) &&
utype.IsKnownType(KnownTypeCode.Boolean) && arg.MatchLdcI4(0))
{
// condition ? v : (bool?)false
// => condition & v
context.Step("NullableLiftingTransform: 3vl.bool.and(bool, bool?)", ifInst);
return(new ThreeValuedBoolAnd(condition, trueInst).WithILRange(ifInst));
}
if (falseInst.MatchLdLoc(out var v2))
{
// condition ? v : v2
if (MatchThreeValuedLogicConditionPattern(condition, out var nullable1, out var nullable2))
{
// (nullable1.GetValueOrDefault() || (!nullable2.GetValueOrDefault() && !nullable1.HasValue)) ? v : v2
if (v == nullable1 && v2 == nullable2)
{
context.Step("NullableLiftingTransform: 3vl.bool.or(bool?, bool?)", ifInst);
return(new ThreeValuedBoolOr(trueInst, falseInst).WithILRange(ifInst));
}
else if (v == nullable2 && v2 == nullable1)
{
context.Step("NullableLiftingTransform: 3vl.bool.and(bool?, bool?)", ifInst);
return(new ThreeValuedBoolAnd(falseInst, trueInst).WithILRange(ifInst));
}
}
}
}
else if (falseInst.MatchLdLoc(out v))
{
if (MatchNullableCtor(trueInst, out var utype, out var arg) &&
utype.IsKnownType(KnownTypeCode.Boolean) && arg.MatchLdcI4(1))
{
// condition ? (bool?)true : v
// => condition | v
context.Step("NullableLiftingTransform: 3vl.logic.or(bool, bool?)", ifInst);
return(new ThreeValuedBoolOr(condition, falseInst).WithILRange(ifInst));
}
}
return(null);
}