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-rw-r--r--lib/Transforms/Instrumentation/MaximumSpanningTree.cpp119
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diff --git a/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp b/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp
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-//===- MaximumSpanningTree.cpp - LLVM Pass to estimate profile info -------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This module privides means for calculating a maximum spanning tree for the
-// CFG of a function according to a given profile. The tree does not contain
-// leaf edges, since they are needed for optimal edge profiling.
-//
-//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "maximum-spanning-tree"
-#include "MaximumSpanningTree.h"
-#include "llvm/ADT/EquivalenceClasses.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/Format.h"
-using namespace llvm;
-
-namespace {
- // compare two weighted edges
- struct VISIBILITY_HIDDEN EdgeWeightCompare {
- bool operator()(const ProfileInfo::EdgeWeight X,
- const ProfileInfo::EdgeWeight Y) const {
- if (X.second > Y.second) return true;
- if (X.second < Y.second) return false;
-
- // It would be enough to just compare the weights of the edges and be
- // done. With edges of the same weight this may lead to a different MST
- // each time the MST is created. To have more stable sorting (and thus
- // more stable MSTs) furhter sort the edges.
- if (X.first.first != 0 && Y.first.first == 0) return true;
- if (X.first.first == 0 && Y.first.first != 0) return false;
- if (X.first.first == 0 && Y.first.first == 0) return false;
-
- if (X.first.first->size() > Y.first.first->size()) return true;
- if (X.first.first->size() < Y.first.first->size()) return false;
-
- if (X.first.second != 0 && Y.first.second == 0) return true;
- if (X.first.second == 0 && Y.first.second != 0) return false;
- if (X.first.second == 0 && Y.first.second == 0) return false;
-
- if (X.first.second->size() > Y.first.second->size()) return true;
- if (X.first.second->size() < Y.first.second->size()) return false;
-
- return false;
- }
- };
-}
-
-static void inline printMSTEdge(ProfileInfo::EdgeWeight E,
- const char *M) {
- DEBUG(errs() << "--Edge " << E.first
- <<" (Weight "<< format("%g",E.second) << ") "
- << (M) << "\n");
-}
-
-// MaximumSpanningTree() - Takes a function and returns a spanning tree
-// according to the currently active profiling information, the leaf edges are
-// NOT in the MST. MaximumSpanningTree uses the algorithm of Kruskal.
-MaximumSpanningTree::MaximumSpanningTree(std::vector<ProfileInfo::EdgeWeight>
- &EdgeVector) {
-
- std::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 BasicBlock*> Forest;
- for (std::vector<ProfileInfo::EdgeWeight>::iterator bbi = EdgeVector.begin(),
- bbe = EdgeVector.end(); bbi != bbe; ++bbi) {
- Forest.insert(bbi->first.first);
- Forest.insert(bbi->first.second);
- }
- Forest.insert(0);
-
- // Iterate over the sorted edges, biggest first.
- for (std::vector<ProfileInfo::EdgeWeight>::iterator bbi = EdgeVector.begin(),
- bbe = EdgeVector.end(); bbi != bbe; ++bbi) {
- ProfileInfo::Edge e = (*bbi).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 (and not
- // (0,entry)), so we push the edge to the MST if it has some successors.
- MST.push_back(e);
- printMSTEdge(*bbi,"in MST");
- } else {
- // This edge is either (0,entry) or (BB,0) or would create a circle in a
- // subtree.
- printMSTEdge(*bbi,"*not* in MST");
- }
- }
-
- // Sort the MST edges.
- std::stable_sort(MST.begin(),MST.end());
-}
-
-MaximumSpanningTree::MaxSpanTree::iterator MaximumSpanningTree::begin() {
- return MST.begin();
-}
-
-MaximumSpanningTree::MaxSpanTree::iterator MaximumSpanningTree::end() {
- return MST.end();
-}
-
-void MaximumSpanningTree::dump() {
- errs()<<"{";
- for ( MaxSpanTree::iterator ei = MST.begin(), ee = MST.end();
- ei!=ee; ++ei ) {
- errs()<<"("<<((*ei).first?(*ei).first->getNameStr():"0")<<",";
- errs()<<(*ei).second->getNameStr()<<")";
- }
- errs()<<"}\n";
-}