// Nothing changes about this SCC or any other.
}
+void LazyCallGraph::SCC::insertOutgoingEdge(Node &CallerN, Node &CalleeN) {
+ // First insert it into the caller.
+ CallerN.insertEdgeInternal(CalleeN);
+
+ assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC.");
+
+ SCC &CalleeC = *G->SCCMap.lookup(&CalleeN);
+ assert(&CalleeC != this && "Callee must not be in this SCC.");
+ assert(CalleeC.isDescendantOf(*this) &&
+ "Callee must be a descendant of the Caller.");
+
+ // The only change required is to add this SCC to the parent set of the callee.
+ CalleeC.ParentSCCs.insert(this);
+}
+
+SmallVector<LazyCallGraph::SCC *, 1>
+LazyCallGraph::SCC::insertIncomingEdge(Node &CallerN, Node &CalleeN) {
+ // First insert it into the caller.
+ CallerN.insertEdgeInternal(CalleeN);
+
+ assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC.");
+
+ SCC &CallerC = *G->SCCMap.lookup(&CallerN);
+ assert(&CallerC != this && "Caller must not be in this SCC.");
+ assert(CallerC.isDescendantOf(*this) &&
+ "Caller must be a descendant of the Callee.");
+
+ // The algorithm we use for merging SCCs based on the cycle introduced here
+ // is to walk the SCC inverted DAG formed by the parent SCC sets. The inverse
+ // graph has the same cycle properties as the actual DAG of the SCCs, and
+ // when forming SCCs lazily by a DFS, the bottom of the graph won't exist in
+ // many cases which should prune the search space.
+ //
+ // FIXME: We can get this pruning behavior even after the incremental SCC
+ // formation by leaving behind (conservative) DFS numberings in the nodes,
+ // and pruning the search with them. These would need to be cleverly updated
+ // during the removal of intra-SCC edges, but could be preserved
+ // conservatively.
+
+ // The set of SCCs that are connected to the caller, and thus will
+ // participate in the merged connected component.
+ SmallPtrSet<SCC *, 8> ConnectedSCCs;
+ ConnectedSCCs.insert(this);
+ ConnectedSCCs.insert(&CallerC);
+
+ // We build up a DFS stack of the parents chains.
+ SmallVector<std::pair<SCC *, SCC::parent_iterator>, 8> DFSSCCs;
+ SmallPtrSet<SCC *, 8> VisitedSCCs;
+ int ConnectedDepth = -1;
+ SCC *C = this;
+ parent_iterator I = parent_begin(), E = parent_end();
+ for (;;) {
+ while (I != E) {
+ SCC &ParentSCC = *I++;
+
+ // If we have already processed this parent SCC, skip it, and remember
+ // whether it was connected so we don't have to check the rest of the
+ // stack. This also handles when we reach a child of the 'this' SCC (the
+ // callee) which terminates the search.
+ if (ConnectedSCCs.count(&ParentSCC)) {
+ ConnectedDepth = std::max<int>(ConnectedDepth, DFSSCCs.size());
+ continue;
+ }
+ if (VisitedSCCs.count(&ParentSCC))
+ continue;
+
+ // We fully explore the depth-first space, adding nodes to the connected
+ // set only as we pop them off, so "recurse" by rotating to the parent.
+ DFSSCCs.push_back(std::make_pair(C, I));
+ C = &ParentSCC;
+ I = ParentSCC.parent_begin();
+ E = ParentSCC.parent_end();
+ }
+
+ // If we've found a connection anywhere below this point on the stack (and
+ // thus up the parent graph from the caller), the current node needs to be
+ // added to the connected set now that we've processed all of its parents.
+ if ((int)DFSSCCs.size() == ConnectedDepth) {
+ --ConnectedDepth; // We're finished with this connection.
+ ConnectedSCCs.insert(C);
+ } else {
+ // Otherwise remember that its parents don't ever connect.
+ assert(ConnectedDepth < (int)DFSSCCs.size() &&
+ "Cannot have a connected depth greater than the DFS depth!");
+ VisitedSCCs.insert(C);
+ }
+
+ if (DFSSCCs.empty())
+ break; // We've walked all the parents of the caller transitively.
+
+ // Pop off the prior node and position to unwind the depth first recursion.
+ std::tie(C, I) = DFSSCCs.pop_back_val();
+ E = C->parent_end();
+ }
+
+ // Now that we have identified all of the SCCs which need to be merged into
+ // a connected set with the inserted edge, merge all of them into this SCC.
+ // FIXME: This operation currently creates ordering stability problems
+ // because we don't use stably ordered containers for the parent SCCs or the
+ // connected SCCs.
+ unsigned NewNodeBeginIdx = Nodes.size();
+ for (SCC *C : ConnectedSCCs) {
+ if (C == this)
+ continue;
+ for (SCC *ParentC : C->ParentSCCs)
+ if (!ConnectedSCCs.count(ParentC))
+ ParentSCCs.insert(ParentC);
+ C->ParentSCCs.clear();
+
+ for (Node *N : *C) {
+ for (Node &ChildN : *N) {
+ SCC &ChildC = *G->SCCMap.lookup(&ChildN);
+ if (&ChildC != C)
+ ChildC.ParentSCCs.erase(C);
+ }
+ G->SCCMap[N] = this;
+ Nodes.push_back(N);
+ }
+ C->Nodes.clear();
+ }
+ for (auto I = Nodes.begin() + NewNodeBeginIdx, E = Nodes.end(); I != E; ++I)
+ for (Node &ChildN : **I) {
+ SCC &ChildC = *G->SCCMap.lookup(&ChildN);
+ if (&ChildC != this)
+ ChildC.ParentSCCs.insert(this);
+ }
+
+ // We return the list of SCCs which were merged so that callers can
+ // invalidate any data they have associated with those SCCs. Note that these
+ // SCCs are no longer in an interesting state (they are totally empty) but
+ // the pointers will remain stable for the life of the graph itself.
+ return SmallVector<SCC *, 1>(ConnectedSCCs.begin(), ConnectedSCCs.end());
+}
+
void LazyCallGraph::SCC::removeInterSCCEdge(Node &CallerN, Node &CalleeN) {
// First remove it from the node.
CallerN.removeEdgeInternal(CalleeN.getFunction());
continue;
}
- // Track the lowest link of the childen, if any are still in the stack.
+ // Track the lowest link of the children, if any are still in the stack.
// Any child not on the stack will have a LowLink of -1.
assert(ChildN.LowLink != 0 &&
"Low-link must not be zero with a non-zero DFS number.");
continue;
}
- // Track the lowest link of the childen, if any are still in the stack.
+ // Track the lowest link of the children, if any are still in the stack.
assert(ChildN.LowLink != 0 &&
"Low-link must not be zero with a non-zero DFS number.");
if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink)
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