#define LLVM_ADT_SCCITERATOR_H
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/iterator.h"
#include <cassert>
struct NodeInfo {
NodeInfo *Group = this;
uint32_t Rank = 0;
- bool Visited = true;
+ bool Visited = false;
+ DenseSet<const EdgeType *> IncomingMSTEdges;
};
// Find the root group of the node and compress the path from node to the
MSTEdges.insert(Edge);
}
- // Do BFS on MST, starting from nodes that have no incoming edge. These nodes
- // are "roots" of the MST forest. This ensures that nodes are visited before
- // their decsendents are, thus ensures hot edges are processed before cold
- // edges, based on how MST is computed.
+ // Run Kahn's algorithm on MST to compute a topological traversal order.
+ // The algorithm starts from nodes that have no incoming edge. These nodes are
+ // "roots" of the MST forest. This ensures that nodes are visited before their
+ // descendants are, thus ensures hot edges are processed before cold edges,
+ // based on how MST is computed.
+ std::queue<NodeType *> Queue;
for (const auto *Edge : MSTEdges)
- NodeInfoMap[Edge->Target].Visited = false;
+ NodeInfoMap[Edge->Target].IncomingMSTEdges.insert(Edge);
- std::queue<NodeType *> Queue;
- // Initialze the queue with MST roots. Note that walking through SortedEdges
- // instead of NodeInfoMap ensures an ordered deterministic push.
+ // Walk through SortedEdges to initialize the queue, instead of using NodeInfoMap
+ // to ensure an ordered deterministic push.
for (auto *Edge : SortedEdges) {
- if (NodeInfoMap[Edge->Source].Visited) {
+ if (!NodeInfoMap[Edge->Source].Visited &&
+ NodeInfoMap[Edge->Source].IncomingMSTEdges.empty()) {
Queue.push(Edge->Source);
- NodeInfoMap[Edge->Source].Visited = false;
+ NodeInfoMap[Edge->Source].Visited = true;
}
}
Queue.pop();
Nodes.push_back(Node);
for (auto &Edge : Node->Edges) {
- if (MSTEdges.count(&Edge) && !NodeInfoMap[Edge.Target].Visited) {
- NodeInfoMap[Edge.Target].Visited = true;
+ NodeInfoMap[Edge.Target].IncomingMSTEdges.erase(&Edge);
+ if (MSTEdges.count(&Edge) &&
+ NodeInfoMap[Edge.Target].IncomingMSTEdges.empty()) {
Queue.push(Edge.Target);
}
}