SILValue LSValue::reduce(LSLocation &Base, SILModule *M,
LSLocationValueMap &Values,
SILInstruction *InsertPt,
TypeExpansionAnalysis *TE) {
// Walk bottom up the projection tree, try to reason about how to construct
// a single SILValue out of all the available values for all the memory
// locations.
//
// First, get a list of all the leaf nodes and intermediate nodes for the
// Base memory location.
LSLocationList ALocs;
ProjectionPath &BasePath = Base.getPath().getValue();
for (const auto &P :
TE->getTypeExpansionProjectionPaths(Base.getType(), M, TEKind::TENode)) {
ALocs.push_back(LSLocation(Base.getBase(), P.getValue(), BasePath));
}
// Second, go from leaf nodes to their parents. This guarantees that at the
// point the parent is processed, its children have been processed already.
for (auto I = ALocs.rbegin(), E = ALocs.rend(); I != E; ++I) {
// This is a leaf node, we have a value for it.
//
// Reached the end of the projection tree, this is a leaf node.
LSLocationList FirstLevel;
I->getFirstLevelLSLocations(FirstLevel, M);
if (FirstLevel.empty())
continue;
// If this is a class reference type, we have reached end of the type tree.
if (I->getType().getClassOrBoundGenericClass())
continue;
// This is NOT a leaf node, we need to construct a value for it.
// There is only 1 children node and its value's projection path is not
// empty, keep stripping it.
auto Iter = FirstLevel.begin();
LSValue &FirstVal = Values[*Iter];
if (FirstLevel.size() == 1 && !FirstVal.hasEmptyProjectionPath()) {
Values[*I] = FirstVal.stripLastLevelProjection();
// We have a value for the parent, remove all the values for children.
removeLSLocations(Values, FirstLevel);
continue;
}
// If there are more than 1 children and all the children nodes have
// LSValues with the same base and non-empty projection path. we can get
// away by not extracting value for every single field.
//
// Simply create a new node with all the aggregated base value, i.e.
// stripping off the last level projection.
bool HasIdenticalValueBase = true;
SILValue FirstBase = FirstVal.getBase();
Iter = std::next(Iter);
for (auto EndIter = FirstLevel.end(); Iter != EndIter; ++Iter) {
LSValue &V = Values[*Iter];
HasIdenticalValueBase &= (FirstBase == V.getBase());
}
if (FirstLevel.size() > 1 && HasIdenticalValueBase &&
!FirstVal.hasEmptyProjectionPath()) {
Values[*I] = FirstVal.stripLastLevelProjection();
// We have a value for the parent, remove all the values for children.
removeLSLocations(Values, FirstLevel);
continue;
}
// In 3 cases do we need aggregation.
//
// 1. If there is only 1 child and we cannot strip off any projections,
// that means we need to create an aggregation.
//
// 2. There are multiple children and they have the same base, but empty
// projection paths.
//
// 3. Children have values from different bases, We need to create
// extractions and aggregation in this case.
//
llvm::SmallVector<SILValue, 8> Vals;
for (auto &X : FirstLevel) {
Vals.push_back(Values[X].materialize(InsertPt));
}
SILBuilder Builder(InsertPt);
// We use an auto-generated SILLocation for now.
// TODO: make the sil location more precise.
NullablePtr<swift::SILInstruction> AI =
Projection::createAggFromFirstLevelProjections(
Builder, RegularLocation::getAutoGeneratedLocation(), I->getType(),
Vals);
// This is the Value for the current node.
ProjectionPath P;
Values[*I] = LSValue(SILValue(AI.get()), P);
removeLSLocations(Values, FirstLevel);
// Keep iterating until we have reach the top-most level of the projection
// tree.
// i.e. the memory location represented by the Base.
}
assert(Values.size() == 1 && "Should have a single location this point");
// Finally materialize and return the forwarding SILValue.
return Values.begin()->second.materialize(InsertPt);
}
void
LSValue::reduceInner(LSLocation &Base, SILModule *M, LSLocationValueMap &Values,
SILInstruction *InsertPt) {
// If this is a class reference type, we have reached end of the type tree.
if (Base.getType(M).getClassOrBoundGenericClass())
return;
// This is a leaf node, we must have a value for it.
LSLocationList NextLevel;
Base.getNextLevelLSLocations(NextLevel, M);
if (NextLevel.empty())
return;
// This is not a leaf node, reduce the next level node one by one.
for (auto &X : NextLevel) {
LSValue::reduceInner(X, M, Values, InsertPt);
}
// This is NOT a leaf node, we need to construct a value for it.
auto Iter = NextLevel.begin();
LSValue &FirstVal = Values[*Iter];
// There is only 1 children node and its value's projection path is not
// empty, keep stripping it.
if (NextLevel.size() == 1 && !FirstVal.hasEmptyProjectionPath()) {
Values[Base] = FirstVal.stripLastLevelProjection();
// We have a value for the parent, remove all the values for children.
removeLSLocations(Values, NextLevel);
return;
}
bool HasIdenticalBase = true;
SILValue FirstBase = FirstVal.getBase();
for (auto &X : NextLevel) {
HasIdenticalBase &= (FirstBase == Values[X].getBase());
}
// This is NOT a leaf node and it has multiple children, but they have the
// same value base.
if (NextLevel.size() > 1 && HasIdenticalBase) {
if (!FirstVal.hasEmptyProjectionPath()) {
Values[Base] = FirstVal.stripLastLevelProjection();
// We have a value for the parent, remove all the values for children.
removeLSLocations(Values, NextLevel);
return;
}
}
// In 3 cases do we need aggregation.
//
// 1. If there is only 1 child and we cannot strip off any projections,
// that means we need to create an aggregation.
//
// 2. There are multiple children and they have the same base, but empty
// projection paths.
//
// 3. Children have values from different bases, We need to create
// extractions and aggregation in this case.
//
llvm::SmallVector<SILValue, 8> Vals;
for (auto &X : NextLevel) {
Vals.push_back(Values[X].materialize(InsertPt));
}
SILBuilder Builder(InsertPt);
Builder.setCurrentDebugScope(InsertPt->getFunction()->getDebugScope());
// We use an auto-generated SILLocation for now.
NullablePtr<swift::SILInstruction> AI =
Projection::createAggFromFirstLevelProjections(
Builder, RegularLocation::getAutoGeneratedLocation(),
Base.getType(M).getObjectType(),
Vals);
// This is the Value for the current base.
ProjectionPath P(Base.getType(M));
Values[Base] = LSValue(SILValue(AI.get()), P);
removeLSLocations(Values, NextLevel);
}