SILValue MemLocation::reduceWithValues(MemLocation &Base, SILModule *Mod, MemLocationValueMap &Values, SILInstruction *InsertPt) { // 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. MemLocationList ALocs; ProjectionPathList Paths; ProjectionPath::expandTypeIntoLeafProjectionPaths(Base.getType(), Mod, Paths, false); for (auto &X : Paths) { ALocs.push_back(MemLocation::createMemLocation(Base.getBase(), X.getValue(), Base.getPath().getValue())); } // 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. MemLocationList FirstLevel; I->getFirstLevelMemLocations(FirstLevel, Mod); 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. // // If there are more than 1 children and all the children nodes have // LoadStoreValues with the same base. 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; auto Iter = FirstLevel.begin(); LoadStoreValue &FirstVal = Values[*Iter]; SILValue FirstBase = FirstVal.getBase(); Iter = std::next(Iter); for (auto EndIter = FirstLevel.end(); Iter != EndIter; ++Iter) { LoadStoreValue &V = Values[*Iter]; HasIdenticalValueBase &= (FirstBase == V.getBase()); } if (HasIdenticalValueBase && (FirstLevel.size() > 1 || !FirstVal.hasEmptyProjectionPath())) { Values[*I] = FirstVal.stripLastLevelProjection(); // We have a value for the parent, remove all the values for children. removeMemLocations(Values, FirstLevel); continue; } // In 2 cases do we need aggregation. // // 1. If there is only 1 child and we can not strip off any projections, // that means we need to create an aggregation. // // 2. 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); NullablePtr<swift::SILInstruction> AI = Projection::createAggFromFirstLevelProjections( Builder, InsertPt->getLoc(), I->getType(), Vals); // This is the Value for the current node. ProjectionPath P; Values[*I] = LoadStoreValue(SILValue(AI.get()), P); removeMemLocations(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); }