1 //===- ProfileEstimatorPass.cpp - LLVM Pass to estimate profile info ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a concrete implementation of profiling information that
11 // estimates the profiling information in a very crude and unimaginative way.
13 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "profile-estimator"
15 #include "llvm/Pass.h"
16 #include "llvm/Analysis/Passes.h"
17 #include "llvm/Analysis/ProfileInfo.h"
18 #include "llvm/Analysis/LoopInfo.h"
19 #include "llvm/Support/CommandLine.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include "llvm/Support/Format.h"
25 static cl::opt<double>
27 "profile-estimator-loop-weight", cl::init(10),
28 cl::value_desc("loop-weight"),
29 cl::desc("Number of loop executions used for profile-estimator")
33 class VISIBILITY_HIDDEN ProfileEstimatorPass :
34 public FunctionPass, public ProfileInfo {
37 std::set<BasicBlock*> BBisVisited;
38 std::map<Loop*,double> LoopExitWeights;
40 static char ID; // Class identification, replacement for typeinfo
41 explicit ProfileEstimatorPass(const double execcount = 0)
42 : FunctionPass(&ID), ExecCount(execcount) {
43 if (execcount == 0) ExecCount = LoopWeight;
46 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
48 AU.addRequired<LoopInfo>();
51 virtual const char *getPassName() const {
52 return "Profiling information estimator";
55 /// run - Estimate the profile information from the specified file.
56 virtual bool runOnFunction(Function &F);
58 virtual void recurseBasicBlock(BasicBlock *BB);
60 void inline printEdgeWeight(Edge);
62 } // End of anonymous namespace
64 char ProfileEstimatorPass::ID = 0;
65 static RegisterPass<ProfileEstimatorPass>
66 X("profile-estimator", "Estimate profiling information", false, true);
68 static RegisterAnalysisGroup<ProfileInfo> Y(X);
71 const PassInfo *ProfileEstimatorPassID = &X;
73 FunctionPass *createProfileEstimatorPass() {
74 return new ProfileEstimatorPass();
77 /// createProfileEstimatorPass - This function returns a Pass that estimates
78 /// profiling information using the given loop execution count.
79 Pass *createProfileEstimatorPass(const unsigned execcount) {
80 return new ProfileEstimatorPass(execcount);
84 static double ignoreMissing(double w) {
85 if (w == ProfileInfo::MissingValue) return 0;
89 static void inline printEdgeError(BasicBlock *V1, BasicBlock *V2) {
90 DEBUG(errs() << "-- Edge (" <<(V1)->getName() << "," << (V2)->getName() \
91 << ") is not calculated, returning\n");
94 void inline ProfileEstimatorPass::printEdgeWeight(Edge E) {
95 DEBUG(errs() << "-- Weight of Edge " << E << ":"
96 << format("%g", getEdgeWeight(E)) << "\n");
99 // recurseBasicBlock() - This calculates the ProfileInfo estimation for a
100 // single block and then recurses into the successors.
101 void ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
103 // Break the recursion if this BasicBlock was already visited.
104 if (BBisVisited.find(BB) != BBisVisited.end()) return;
106 // Check if incoming edges are calculated already, if BB is header allow
107 // backedges that are uncalculated for now.
108 bool BBisHeader = LI->isLoopHeader(BB);
109 Loop* BBLoop = LI->getLoopFor(BB);
112 std::set<BasicBlock*> ProcessedPreds;
113 for ( pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
114 bbi != bbe; ++bbi ) {
115 if (ProcessedPreds.insert(*bbi).second) {
116 Edge edge = getEdge(*bbi,BB);
117 BBWeight += ignoreMissing(getEdgeWeight(edge));
119 if (BBisHeader && BBLoop == LI->getLoopFor(*bbi)) {
120 printEdgeError(*bbi,BB);
123 if (BBisVisited.find(*bbi) == BBisVisited.end()) {
124 printEdgeError(*bbi,BB);
128 if (getExecutionCount(BB) != MissingValue) {
129 BBWeight = getExecutionCount(BB);
132 // Fetch all necessary information for current block.
133 SmallVector<Edge, 8> ExitEdges;
134 SmallVector<Edge, 8> Edges;
136 BBLoop->getExitEdges(ExitEdges);
139 // If block is an loop header, first subtract all weights from edges that
140 // exit this loop, then distribute remaining weight on to the edges exiting
141 // this loop. Finally the weight of the block is increased, to simulate
142 // several executions of this loop.
144 double incoming = BBWeight;
145 // Subtract the flow leaving the loop.
146 for (SmallVector<Edge, 8>::iterator ei = ExitEdges.begin(),
147 ee = ExitEdges.end(); ei != ee; ++ei) {
148 double w = getEdgeWeight(*ei);
149 if (w == MissingValue) {
150 Edges.push_back(*ei);
155 // Distribute remaining weight onto the exit edges.
156 for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
158 EdgeInformation[BB->getParent()][*ei] += incoming/Edges.size();
159 printEdgeWeight(*ei);
161 // Increase flow into the loop.
162 BBWeight *= (ExecCount+1);
165 // Remove from current flow of block all the successor edges that already
166 // have some flow on them.
168 std::set<BasicBlock*> ProcessedSuccs;
170 // Otherwise consider weight of outgoing edges and store them for
171 // distribution of remaining weight. In case the block has no successors
172 // create a (BB,0) edge.
173 succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
175 Edge edge = getEdge(BB,0);
176 EdgeInformation[BB->getParent()][edge] = BBWeight;
177 printEdgeWeight(edge);
179 for ( ; bbi != bbe; ++bbi ) {
180 if (ProcessedSuccs.insert(*bbi).second) {
181 Edge edge = getEdge(BB,*bbi);
182 double w = getEdgeWeight(edge);
183 if (w != MissingValue) {
184 BBWeight -= getEdgeWeight(edge);
186 Edges.push_back(edge);
191 // Distribute remaining flow onto the outgoing edges.
192 for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
194 EdgeInformation[BB->getParent()][*ei] += BBWeight/Edges.size();
195 printEdgeWeight(*ei);
198 // Mark this Block visited and recurse into successors.
199 BBisVisited.insert(BB);
200 for ( succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
203 recurseBasicBlock(*bbi);
207 bool ProfileEstimatorPass::runOnFunction(Function &F) {
208 if (F.isDeclaration()) return false;
210 LI = &getAnalysis<LoopInfo>();
211 FunctionInformation.erase(&F);
212 BlockInformation[&F].clear();
213 EdgeInformation[&F].clear();
216 DEBUG(errs() << "Working on function " << F.getNameStr() << "\n");
218 // Since the entry block is the first one and has no predecessors, the edge
219 // (0,entry) is inserted with the starting weight of 1.
220 BasicBlock *entry = &F.getEntryBlock();
221 BlockInformation[&F][entry] = 1;
223 Edge edge = getEdge(0,entry);
224 EdgeInformation[&F][edge] = 1; printEdgeWeight(edge);
225 recurseBasicBlock(entry);
227 // In case something went wrong, clear all results, not profiling info is
229 if (BBisVisited.size() != F.size()) {
230 DEBUG(errs() << "-- could not estimate profile, using default profile\n");
231 FunctionInformation.erase(&F);
232 BlockInformation[&F].clear();
233 for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
234 for (pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
236 Edge e = getEdge(*bbi,BB);
237 EdgeInformation[&F][e] = 1;
240 for (succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
242 Edge e = getEdge(BB,*bbi);
243 EdgeInformation[&F][e] = 1;