| //===- OptimalEdgeProfiling.cpp - Insert counters for opt. edge profiling -===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass instruments the specified program with counters for edge profiling. |
| // Edge profiling can give a reasonable approximation of the hot paths through a |
| // program, and is used for a wide variety of program transformations. |
| // |
| //===----------------------------------------------------------------------===// |
| #define DEBUG_TYPE "insert-optimal-edge-profiling" |
| #include "ProfilingUtils.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/Passes.h" |
| #include "llvm/Analysis/ProfileInfo.h" |
| #include "llvm/Analysis/ProfileInfoLoader.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Instrumentation.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "MaximumSpanningTree.h" |
| using namespace llvm; |
| |
| STATISTIC(NumEdgesInserted, "The # of edges inserted."); |
| |
| namespace { |
| class OptimalEdgeProfiler : public ModulePass { |
| bool runOnModule(Module &M); |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| OptimalEdgeProfiler() : ModulePass(ID) { |
| initializeOptimalEdgeProfilerPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequiredID(ProfileEstimatorPassID); |
| AU.addRequired<ProfileInfo>(); |
| } |
| |
| virtual const char *getPassName() const { |
| return "Optimal Edge Profiler"; |
| } |
| }; |
| } |
| |
| char OptimalEdgeProfiler::ID = 0; |
| INITIALIZE_PASS_BEGIN(OptimalEdgeProfiler, "insert-optimal-edge-profiling", |
| "Insert optimal instrumentation for edge profiling", |
| false, false) |
| INITIALIZE_PASS_DEPENDENCY(ProfileEstimatorPass) |
| INITIALIZE_AG_DEPENDENCY(ProfileInfo) |
| INITIALIZE_PASS_END(OptimalEdgeProfiler, "insert-optimal-edge-profiling", |
| "Insert optimal instrumentation for edge profiling", |
| false, false) |
| |
| ModulePass *llvm::createOptimalEdgeProfilerPass() { |
| return new OptimalEdgeProfiler(); |
| } |
| |
| inline static void printEdgeCounter(ProfileInfo::Edge e, |
| BasicBlock* b, |
| unsigned i) { |
| DEBUG(dbgs() << "--Edge Counter for " << (e) << " in " \ |
| << ((b)?(b)->getNameStr():"0") << " (# " << (i) << ")\n"); |
| } |
| |
| bool OptimalEdgeProfiler::runOnModule(Module &M) { |
| Function *Main = M.getFunction("main"); |
| if (Main == 0) { |
| errs() << "WARNING: cannot insert edge profiling into a module" |
| << " with no main function!\n"; |
| return false; // No main, no instrumentation! |
| } |
| |
| // NumEdges counts all the edges that may be instrumented. Later on its |
| // decided which edges to actually instrument, to achieve optimal profiling. |
| // For the entry block a virtual edge (0,entry) is reserved, for each block |
| // with no successors an edge (BB,0) is reserved. These edges are necessary |
| // to calculate a truly optimal maximum spanning tree and thus an optimal |
| // instrumentation. |
| unsigned NumEdges = 0; |
| |
| for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) { |
| if (F->isDeclaration()) continue; |
| // Reserve space for (0,entry) edge. |
| ++NumEdges; |
| for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { |
| // Keep track of which blocks need to be instrumented. We don't want to |
| // instrument blocks that are added as the result of breaking critical |
| // edges! |
| if (BB->getTerminator()->getNumSuccessors() == 0) { |
| // Reserve space for (BB,0) edge. |
| ++NumEdges; |
| } else { |
| NumEdges += BB->getTerminator()->getNumSuccessors(); |
| } |
| } |
| } |
| |
| // In the profiling output a counter for each edge is reserved, but only few |
| // are used. This is done to be able to read back in the profile without |
| // calulating the maximum spanning tree again, instead each edge counter that |
| // is not used is initialised with -1 to signal that this edge counter has to |
| // be calculated from other edge counters on reading the profile info back |
| // in. |
| |
| const Type *Int32 = Type::getInt32Ty(M.getContext()); |
| const ArrayType *ATy = ArrayType::get(Int32, NumEdges); |
| GlobalVariable *Counters = |
| new GlobalVariable(M, ATy, false, GlobalValue::InternalLinkage, |
| Constant::getNullValue(ATy), "OptEdgeProfCounters"); |
| NumEdgesInserted = 0; |
| |
| std::vector<Constant*> Initializer(NumEdges); |
| Constant *Zero = ConstantInt::get(Int32, 0); |
| Constant *Uncounted = ConstantInt::get(Int32, ProfileInfoLoader::Uncounted); |
| |
| // Instrument all of the edges not in MST... |
| unsigned i = 0; |
| for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) { |
| if (F->isDeclaration()) continue; |
| DEBUG(dbgs() << "Working on " << F->getNameStr() << "\n"); |
| |
| // Calculate a Maximum Spanning Tree with the edge weights determined by |
| // ProfileEstimator. ProfileEstimator also assign weights to the virtual |
| // edges (0,entry) and (BB,0) (for blocks with no successors) and this |
| // edges also participate in the maximum spanning tree calculation. |
| // The third parameter of MaximumSpanningTree() has the effect that not the |
| // actual MST is returned but the edges _not_ in the MST. |
| |
| ProfileInfo::EdgeWeights ECs = |
| getAnalysis<ProfileInfo>(*F).getEdgeWeights(F); |
| std::vector<ProfileInfo::EdgeWeight> EdgeVector(ECs.begin(), ECs.end()); |
| MaximumSpanningTree<BasicBlock> MST(EdgeVector); |
| std::stable_sort(MST.begin(), MST.end()); |
| |
| // Check if (0,entry) not in the MST. If not, instrument edge |
| // (IncrementCounterInBlock()) and set the counter initially to zero, if |
| // the edge is in the MST the counter is initialised to -1. |
| |
| BasicBlock *entry = &(F->getEntryBlock()); |
| ProfileInfo::Edge edge = ProfileInfo::getEdge(0, entry); |
| if (!std::binary_search(MST.begin(), MST.end(), edge)) { |
| printEdgeCounter(edge, entry, i); |
| IncrementCounterInBlock(entry, i, Counters); ++NumEdgesInserted; |
| Initializer[i++] = (Zero); |
| } else{ |
| Initializer[i++] = (Uncounted); |
| } |
| |
| // InsertedBlocks contains all blocks that were inserted for splitting an |
| // edge, this blocks do not have to be instrumented. |
| DenseSet<BasicBlock*> InsertedBlocks; |
| for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { |
| // Check if block was not inserted and thus does not have to be |
| // instrumented. |
| if (InsertedBlocks.count(BB)) continue; |
| |
| // Okay, we have to add a counter of each outgoing edge not in MST. If |
| // the outgoing edge is not critical don't split it, just insert the |
| // counter in the source or destination of the edge. Also, if the block |
| // has no successors, the virtual edge (BB,0) is processed. |
| TerminatorInst *TI = BB->getTerminator(); |
| if (TI->getNumSuccessors() == 0) { |
| ProfileInfo::Edge edge = ProfileInfo::getEdge(BB, 0); |
| if (!std::binary_search(MST.begin(), MST.end(), edge)) { |
| printEdgeCounter(edge, BB, i); |
| IncrementCounterInBlock(BB, i, Counters); ++NumEdgesInserted; |
| Initializer[i++] = (Zero); |
| } else{ |
| Initializer[i++] = (Uncounted); |
| } |
| } |
| for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) { |
| BasicBlock *Succ = TI->getSuccessor(s); |
| ProfileInfo::Edge edge = ProfileInfo::getEdge(BB,Succ); |
| if (!std::binary_search(MST.begin(), MST.end(), edge)) { |
| |
| // If the edge is critical, split it. |
| bool wasInserted = SplitCriticalEdge(TI, s, this); |
| Succ = TI->getSuccessor(s); |
| if (wasInserted) |
| InsertedBlocks.insert(Succ); |
| |
| // Okay, we are guaranteed that the edge is no longer critical. If |
| // we only have a single successor, insert the counter in this block, |
| // otherwise insert it in the successor block. |
| if (TI->getNumSuccessors() == 1) { |
| // Insert counter at the start of the block |
| printEdgeCounter(edge, BB, i); |
| IncrementCounterInBlock(BB, i, Counters); ++NumEdgesInserted; |
| } else { |
| // Insert counter at the start of the block |
| printEdgeCounter(edge, Succ, i); |
| IncrementCounterInBlock(Succ, i, Counters); ++NumEdgesInserted; |
| } |
| Initializer[i++] = (Zero); |
| } else { |
| Initializer[i++] = (Uncounted); |
| } |
| } |
| } |
| } |
| |
| // Check if the number of edges counted at first was the number of edges we |
| // considered for instrumentation. |
| assert(i == NumEdges && "the number of edges in counting array is wrong"); |
| |
| // Assign the now completely defined initialiser to the array. |
| Constant *init = ConstantArray::get(ATy, Initializer); |
| Counters->setInitializer(init); |
| |
| // Add the initialization call to main. |
| InsertProfilingInitCall(Main, "llvm_start_opt_edge_profiling", Counters); |
| return true; |
| } |
| |