bool typeFitsConstraint(Type t, TypeConstraint tc) {
switch (tc.category) {
case DataTypeGeneric:
return true;
case DataTypeCountness:
// Consumers using this constraint expect the type to be relaxed to
// Uncounted or left alone, so something like Arr|Obj isn't specific
// enough.
return !t.maybe(TCounted) ||
t.subtypeOfAny(TStr, TArr, TObj,
TRes, TBoxedCell);
case DataTypeCountnessInit:
return typeFitsConstraint(t, DataTypeCountness) &&
(t <= TUninit || !t.maybe(TUninit));
case DataTypeSpecific:
return t.isKnownDataType();
case DataTypeSpecialized:
// Type::isSpecialized() returns true for types like {Arr<Packed>|Int}
// and Arr has non-specialized subtypes, so we require that t is
// specialized, a strict subtype of Obj or Arr, and that it fits the
// specific requirements of tc.
assertx(tc.wantClass() ^ tc.wantArrayKind());
if (t < TObj && t.clsSpec()) {
return tc.wantClass() &&
t.clsSpec().cls()->classof(tc.desiredClass());
}
if (t < TArr && t.arrSpec()) {
auto arrSpec = t.arrSpec();
if (tc.wantArrayShape() && !arrSpec.shape()) return false;
if (tc.wantArrayKind() && !arrSpec.kind()) return false;
return true;
}
return false;
}
not_reached();
}
/*
* Return a copy of tc refined with any new information in newTc.
*/
TypeConstraint applyConstraint(TypeConstraint tc, const TypeConstraint newTc) {
tc.category = std::max(newTc.category, tc.category);
if (newTc.wantArrayKind()) tc.setWantArrayKind();
if (newTc.wantArrayShape()) tc.setWantArrayShape();
if (newTc.wantClass()) {
if (tc.wantClass()) {
// It only makes sense to constrain tc with a class that's related to its
// existing class, and we want to preserve the more derived of the two.
auto cls1 = tc.desiredClass();
auto cls2 = newTc.desiredClass();
tc.setDesiredClass(cls1->classof(cls2) ? cls1 : cls2);
} else {
tc.setDesiredClass(newTc.desiredClass());
}
}
return tc;
}
/*
* relaxConstraint returns the least specific TypeConstraint 'tc' that doesn't
* prevent the intersection of knownType and relaxType(toRelax, tc) from
* satisfying origTc. It is used in IRBuilder::constrainValue and
* IRBuilder::constrainStack to determine how to constrain the typeParam and
* src values of CheckType/CheckStk instructions, and the src values of
* AssertType/AssertStk instructions.
*
* AssertType example:
* t24:Obj<C> = AssertType<{Obj<C>|InitNull}> t4:Obj
*
* If constrainValue is called with (t24, DataTypeSpecialized), relaxConstraint
* will be called with (DataTypeSpecialized, Obj<C>|InitNull, Obj). After a few
* iterations it will determine that constraining Obj with DataTypeCountness
* will still allow the result type of the AssertType instruction to satisfy
* DataTypeSpecialized, because relaxType(Obj, DataTypeCountness) == Obj.
*/
TypeConstraint relaxConstraint(const TypeConstraint origTc,
const Type knownType, const Type toRelax) {
ITRACE(4, "relaxConstraint({}, knownType = {}, toRelax = {})\n",
origTc, knownType, toRelax);
Trace::Indent _i;
auto const dstType = knownType & toRelax;
always_assert_flog(typeFitsConstraint(dstType, origTc),
"refine({}, {}) doesn't fit {}",
knownType, toRelax, origTc);
// Preserve origTc's weak property.
TypeConstraint newTc{DataTypeGeneric};
newTc.weak = origTc.weak;
while (true) {
if (newTc.isSpecialized()) {
// We need to ask for the right kind of specialization, so grab it from
// origTc.
if (origTc.wantArrayKind()) newTc.setWantArrayKind();
if (origTc.wantArrayShape()) newTc.setWantArrayShape();
if (origTc.wantClass()) newTc.setDesiredClass(origTc.desiredClass());
}
auto const relaxed = relaxType(toRelax, newTc);
auto const newDstType = relaxed & knownType;
if (typeFitsConstraint(newDstType, origTc)) break;
ITRACE(5, "newDstType = {}, newTc = {}; incrementing constraint\n",
newDstType, newTc);
incCategory(newTc.category);
}
ITRACE(4, "Returning {}\n", newTc);
// newTc shouldn't be any more specific than origTc.
always_assert(newTc.category <= origTc.category);
return newTc;
}