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Preparation for Optimal Edge Profiling:
This implements the maximum spanning tree algorithm on CFGs according to weights given by the ProfileEstimator. This is then used to implement Optimal Edge Profiling. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80358 91177308-0d34-0410-b5e6-96231b3b80d8
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lib/Transforms/Instrumentation/MaximumSpanningTree.cpp
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lib/Transforms/Instrumentation/MaximumSpanningTree.cpp
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//===- MaximumSpanningTree.cpp - LLVM Pass to estimate profile info -------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This module privides means for calculating a maximum spanning tree for the
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// CFG of a function according to a given profile. The tree does not contain
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// leaf edges, since they are needed for optimal edge profiling.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "maximum-spanning-tree"
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#include "MaximumSpanningTree.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/ADT/EquivalenceClasses.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Format.h"
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using namespace llvm;
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namespace {
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// compare two weighted edges
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struct VISIBILITY_HIDDEN EdgeWeightCompare {
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bool operator()(const ProfileInfo::EdgeWeight X,
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const ProfileInfo::EdgeWeight Y) const {
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if (X.second > Y.second) return true;
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if (X.second < Y.second) return false;
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#ifndef NDEBUG
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if (X.first.first != 0 && Y.first.first == 0) return true;
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if (X.first.first == 0 && Y.first.first != 0) return false;
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if (X.first.first == 0 && Y.first.first == 0) return false;
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if (X.first.first->size() > Y.first.first->size()) return true;
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if (X.first.first->size() < Y.first.first->size()) return false;
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if (X.first.second != 0 && Y.first.second == 0) return true;
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if (X.first.second == 0 && Y.first.second != 0) return false;
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if (X.first.second == 0 && Y.first.second == 0) return false;
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if (X.first.second->size() > Y.first.second->size()) return true;
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if (X.first.second->size() < Y.first.second->size()) return false;
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#endif
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return false;
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}
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};
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}
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static void inline printMSTEdge(ProfileInfo::EdgeWeight E,
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const char *M) {
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DEBUG(errs() << "--Edge " << E.first
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<<" (Weight "<< format("%g",E.second) << ") "
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<< (M) << "\n");
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}
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// MaximumSpanningTree() - Takes a function and returns a spanning tree
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// according to the currently active profiling information, the leaf edges are
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// NOT in the MST. MaximumSpanningTree uses the algorithm of Kruskal.
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MaximumSpanningTree::MaximumSpanningTree(Function *F, ProfileInfo *PI,
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bool inverted = false) {
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// Copy edges to vector, sort them biggest first.
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ProfileInfo::EdgeWeights ECs = PI->getEdgeWeights(F);
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std::vector<ProfileInfo::EdgeWeight> EdgeVector(ECs.begin(), ECs.end());
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std::sort(EdgeVector.begin(), EdgeVector.end(), EdgeWeightCompare());
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// Create spanning tree, Forest contains a special data structure
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// that makes checking if two nodes are already in a common (sub-)tree
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// fast and cheap.
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EquivalenceClasses<const BasicBlock*> Forest;
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for (std::vector<ProfileInfo::EdgeWeight>::iterator bbi = EdgeVector.begin(),
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bbe = EdgeVector.end(); bbi != bbe; ++bbi) {
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Forest.insert(bbi->first.first);
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Forest.insert(bbi->first.second);
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}
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Forest.insert(0);
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// Iterate over the sorted edges, biggest first.
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for (std::vector<ProfileInfo::EdgeWeight>::iterator bbi = EdgeVector.begin(),
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bbe = EdgeVector.end(); bbi != bbe; ++bbi) {
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ProfileInfo::Edge e = (*bbi).first;
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if (Forest.findLeader(e.first) != Forest.findLeader(e.second)) {
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Forest.unionSets(e.first, e.second);
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// So we know now that the edge is not already in a subtree (and not
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// (0,entry)), so we push the edge to the MST if it has some successors.
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if (!inverted) { MST.push_back(e); }
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printMSTEdge(*bbi,"in MST");
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} else {
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// This edge is either (0,entry) or (BB,0) or would create a circle in a
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// subtree.
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if (inverted) { MST.push_back(e); }
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printMSTEdge(*bbi,"*not* in MST");
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}
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}
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// Sort the MST edges.
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std::stable_sort(MST.begin(),MST.end());
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}
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MaximumSpanningTree::MaxSpanTree::iterator MaximumSpanningTree::begin() {
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return MST.begin();
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}
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MaximumSpanningTree::MaxSpanTree::iterator MaximumSpanningTree::end() {
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return MST.end();
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}
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void MaximumSpanningTree::dump() {
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errs()<<"{";
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for ( MaxSpanTree::iterator ei = MST.begin(), ee = MST.end();
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ei!=ee; ++ei ) {
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errs()<<"("<<((*ei).first?(*ei).first->getNameStr():"0")<<",";
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errs()<<(*ei).second->getNameStr()<<")";
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}
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errs()<<"}\n";
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}
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lib/Transforms/Instrumentation/MaximumSpanningTree.h
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lib/Transforms/Instrumentation/MaximumSpanningTree.h
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//===- llvm/Analysis/MaximumSpanningTree.h - Interface ----------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This module privides means for calculating a maximum spanning tree for the
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// CFG of a function according to a given profile.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
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#define LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
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#include "llvm/Analysis/ProfileInfo.h"
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#include "llvm/Support/raw_ostream.h"
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#include <vector>
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namespace llvm {
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class Function;
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class MaximumSpanningTree {
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public:
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typedef std::vector<ProfileInfo::Edge> MaxSpanTree;
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protected:
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MaxSpanTree MST;
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public:
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static char ID; // Class identification, replacement for typeinfo
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// MaxSpanTree() - Calculates a MST for a function according to a profile.
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// If inverted is true, all the edges *not* in the MST are returned. As a
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// special also all leaf edges of the MST are not included, this makes it
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// easier for the OptimalEdgeProfileInstrumentation to use this MST to do
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// an optimal profiling.
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MaximumSpanningTree(Function *F, ProfileInfo *PI, bool invert);
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virtual MaxSpanTree::iterator begin();
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virtual MaxSpanTree::iterator end();
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virtual void dump();
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};
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} // End llvm namespace
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#endif
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