//
//===----------------------------------------------------------------------===//
//
-// This module privides means for calculating a maximum spanning tree for the
-// CFG of a function according to a given profile.
+// This module provides means for calculating a maximum spanning tree for a
+// given set of weighted edges. The type parameter T is the type of a node.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
#define LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
-#include "llvm/Analysis/ProfileInfo.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/IR/BasicBlock.h"
+#include <algorithm>
#include <vector>
namespace llvm {
- class Function;
+ /// MaximumSpanningTree - A MST implementation.
+ /// The type parameter T determines the type of the nodes of the graph.
+ template <typename T>
class MaximumSpanningTree {
public:
- typedef std::vector<ProfileInfo::Edge> MaxSpanTree;
-
+ typedef std::pair<const T*, const T*> Edge;
+ typedef std::pair<Edge, double> EdgeWeight;
+ typedef std::vector<EdgeWeight> EdgeWeights;
protected:
+ typedef std::vector<Edge> MaxSpanTree;
+
MaxSpanTree MST;
+ private:
+ // A comparing class for comparing weighted edges.
+ struct EdgeWeightCompare {
+ static bool getBlockSize(const T *X) {
+ const BasicBlock *BB = dyn_cast_or_null<BasicBlock>(X);
+ return BB ? BB->size() : 0;
+ }
+
+ bool operator()(EdgeWeight X, EdgeWeight Y) const {
+ if (X.second > Y.second) return true;
+ if (X.second < Y.second) return false;
+
+ // Equal edge weights: break ties by comparing block sizes.
+ size_t XSizeA = getBlockSize(X.first.first);
+ size_t YSizeA = getBlockSize(Y.first.first);
+ if (XSizeA > YSizeA) return true;
+ if (XSizeA < YSizeA) return false;
+
+ size_t XSizeB = getBlockSize(X.first.second);
+ size_t YSizeB = getBlockSize(Y.first.second);
+ if (XSizeB > YSizeB) return true;
+ if (XSizeB < YSizeB) return false;
+
+ return false;
+ }
+ };
+
public:
static char ID; // Class identification, replacement for typeinfo
- // MaxSpanTree() - Calculates a MST for a function according to a profile.
- // If inverted is true, all the edges *not* in the MST are returned. As a
- // special also all leaf edges of the MST are not included, this makes it
- // easier for the OptimalEdgeProfileInstrumentation to use this MST to do
- // an optimal profiling.
- MaximumSpanningTree(std::vector<ProfileInfo::EdgeWeight>&);
- virtual ~MaximumSpanningTree() {}
+ /// MaximumSpanningTree() - Takes a vector of weighted edges and returns a
+ /// spanning tree.
+ MaximumSpanningTree(EdgeWeights &EdgeVector) {
+
+ std::stable_sort(EdgeVector.begin(), EdgeVector.end(), EdgeWeightCompare());
+
+ // Create spanning tree, Forest contains a special data structure
+ // that makes checking if two nodes are already in a common (sub-)tree
+ // fast and cheap.
+ EquivalenceClasses<const T*> Forest;
+ for (typename EdgeWeights::iterator EWi = EdgeVector.begin(),
+ EWe = EdgeVector.end(); EWi != EWe; ++EWi) {
+ Edge e = (*EWi).first;
+
+ Forest.insert(e.first);
+ Forest.insert(e.second);
+ }
+
+ // Iterate over the sorted edges, biggest first.
+ for (typename EdgeWeights::iterator EWi = EdgeVector.begin(),
+ EWe = EdgeVector.end(); EWi != EWe; ++EWi) {
+ Edge e = (*EWi).first;
+
+ if (Forest.findLeader(e.first) != Forest.findLeader(e.second)) {
+ Forest.unionSets(e.first, e.second);
+ // So we know now that the edge is not already in a subtree, so we push
+ // the edge to the MST.
+ MST.push_back(e);
+ }
+ }
+ }
- virtual MaxSpanTree::iterator begin();
- virtual MaxSpanTree::iterator end();
+ typename MaxSpanTree::iterator begin() {
+ return MST.begin();
+ }
- virtual void dump();
+ typename MaxSpanTree::iterator end() {
+ return MST.end();
+ }
};
} // End llvm namespace