contrib/llvm/lib/Analysis/BlockFrequencyInfo.cpp

   1 //===- BlockFrequencyInfo.cpp - Block Frequency Analysis ------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Loops should be simplified before this analysis.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Analysis/BlockFrequencyInfo.h"
  15 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
  16 #include "llvm/Analysis/BranchProbabilityInfo.h"
  17 #include "llvm/Analysis/LoopInfo.h"
  18 #include "llvm/Analysis/Passes.h"
  19 #include "llvm/IR/CFG.h"
  20 #include "llvm/InitializePasses.h"
  21 #include "llvm/Support/CommandLine.h"
  22 #include "llvm/Support/Debug.h"
  23 #include "llvm/Support/GraphWriter.h"
  24
  25 using namespace llvm;
  26
  27 #define DEBUG_TYPE "block-freq"
  28
  29 static cl::opt<GVDAGType> ViewBlockFreqPropagationDAG(
  30     "view-block-freq-propagation-dags", cl::Hidden,
  31     cl::desc("Pop up a window to show a dag displaying how block "
  32              "frequencies propagation through the CFG."),
  33     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
  34                clEnumValN(GVDT_Fraction, "fraction",
  35                           "display a graph using the "
  36                           "fractional block frequency representation."),
  37                clEnumValN(GVDT_Integer, "integer",
  38                           "display a graph using the raw "
  39                           "integer fractional block frequency representation."),
  40                clEnumValN(GVDT_Count, "count", "display a graph using the real "
  41                                                "profile count if available.")));
  42
  43 cl::opt<std::string>
  44     ViewBlockFreqFuncName("view-bfi-func-name", cl::Hidden,
  45                           cl::desc("The option to specify "
  46                                    "the name of the function "
  47                                    "whose CFG will be displayed."));
  48
  49 cl::opt<unsigned>
  50     ViewHotFreqPercent("view-hot-freq-percent", cl::init(10), cl::Hidden,
  51                        cl::desc("An integer in percent used to specify "
  52                                 "the hot blocks/edges to be displayed "
  53                                 "in red: a block or edge whose frequency "
  54                                 "is no less than the max frequency of the "
  55                                 "function multiplied by this percent."));
  56
  57 // Command line option to turn on CFG dot dump after profile annotation.
  58 cl::opt<bool>
  59     PGOViewCounts("pgo-view-counts", cl::init(false), cl::Hidden,
  60                   cl::desc("A boolean option to show CFG dag with "
  61                            "block profile counts and branch probabilities "
  62                            "right after PGO profile annotation step. The "
  63                            "profile counts are computed using branch "
  64                            "probabilities from the runtime profile data and "
  65                            "block frequency propagation algorithm. To view "
  66                            "the raw counts from the profile, use option "
  67                            "-pgo-view-raw-counts instead. To limit graph "
  68                            "display to only one function, use filtering option "
  69                            "-view-bfi-func-name."));
  70
  71 namespace llvm {
  72
  73 static GVDAGType getGVDT() {
  74
  75   if (PGOViewCounts)
  76     return GVDT_Count;
  77   return ViewBlockFreqPropagationDAG;
  78 }
  79
  80 template <>
  81 struct GraphTraits<BlockFrequencyInfo *> {
  82   typedef const BasicBlock *NodeRef;
  83   typedef succ_const_iterator ChildIteratorType;
  84   typedef pointer_iterator<Function::const_iterator> nodes_iterator;
  85
  86   static NodeRef getEntryNode(const BlockFrequencyInfo *G) {
  87     return &G->getFunction()->front();
  88   }
  89   static ChildIteratorType child_begin(const NodeRef N) {
  90     return succ_begin(N);
  91   }
  92   static ChildIteratorType child_end(const NodeRef N) { return succ_end(N); }
  93   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
  94     return nodes_iterator(G->getFunction()->begin());
  95   }
  96   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
  97     return nodes_iterator(G->getFunction()->end());
  98   }
  99 };
 100
 101 typedef BFIDOTGraphTraitsBase<BlockFrequencyInfo, BranchProbabilityInfo>
 102     BFIDOTGTraitsBase;
 103
 104 template <>
 105 struct DOTGraphTraits<BlockFrequencyInfo *> : public BFIDOTGTraitsBase {
 106   explicit DOTGraphTraits(bool isSimple = false)
 107       : BFIDOTGTraitsBase(isSimple) {}
 108
 109   std::string getNodeLabel(const BasicBlock *Node,
 110                            const BlockFrequencyInfo *Graph) {
 111
 112     return BFIDOTGTraitsBase::getNodeLabel(Node, Graph, getGVDT());
 113   }
 114
 115   std::string getNodeAttributes(const BasicBlock *Node,
 116                                 const BlockFrequencyInfo *Graph) {
 117     return BFIDOTGTraitsBase::getNodeAttributes(Node, Graph,
 118                                                 ViewHotFreqPercent);
 119   }
 120
 121   std::string getEdgeAttributes(const BasicBlock *Node, EdgeIter EI,
 122                                 const BlockFrequencyInfo *BFI) {
 123     return BFIDOTGTraitsBase::getEdgeAttributes(Node, EI, BFI, BFI->getBPI(),
 124                                                 ViewHotFreqPercent);
 125   }
 126 };
 127
 128 } // end namespace llvm
 129
 130 BlockFrequencyInfo::BlockFrequencyInfo() {}
 131
 132 BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
 133                                        const BranchProbabilityInfo &BPI,
 134                                        const LoopInfo &LI) {
 135   calculate(F, BPI, LI);
 136 }
 137
 138 BlockFrequencyInfo::BlockFrequencyInfo(BlockFrequencyInfo &&Arg)
 139     : BFI(std::move(Arg.BFI)) {}
 140
 141 BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
 142   releaseMemory();
 143   BFI = std::move(RHS.BFI);
 144   return *this;
 145 }
 146
 147 // Explicitly define the default constructor otherwise it would be implicitly
 148 // defined at the first ODR-use which is the BFI member in the
 149 // LazyBlockFrequencyInfo header.  The dtor needs the BlockFrequencyInfoImpl
 150 // template instantiated which is not available in the header.
 151 BlockFrequencyInfo::~BlockFrequencyInfo() {}
 152
 153 bool BlockFrequencyInfo::invalidate(Function &F, const PreservedAnalyses &PA,
 154                                     FunctionAnalysisManager::Invalidator &) {
 155   // Check whether the analysis, all analyses on functions, or the function's
 156   // CFG have been preserved.
 157   auto PAC = PA.getChecker<BlockFrequencyAnalysis>();
 158   return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
 159            PAC.preservedSet<CFGAnalyses>());
 160 }
 161
 162 void BlockFrequencyInfo::calculate(const Function &F,
 163                                    const BranchProbabilityInfo &BPI,
 164                                    const LoopInfo &LI) {
 165   if (!BFI)
 166     BFI.reset(new ImplType);
 167   BFI->calculate(F, BPI, LI);
 168   if (ViewBlockFreqPropagationDAG != GVDT_None &&
 169       (ViewBlockFreqFuncName.empty() ||
 170        F.getName().equals(ViewBlockFreqFuncName))) {
 171     view();
 172   }
 173 }
 174
 175 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
 176   return BFI ? BFI->getBlockFreq(BB) : 0;
 177 }
 178
 179 Optional<uint64_t>
 180 BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB) const {
 181   if (!BFI)
 182     return None;
 183
 184   return BFI->getBlockProfileCount(*getFunction(), BB);
 185 }
 186
 187 Optional<uint64_t>
 188 BlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
 189   if (!BFI)
 190     return None;
 191   return BFI->getProfileCountFromFreq(*getFunction(), Freq);
 192 }
 193
 194 void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB, uint64_t Freq) {
 195   assert(BFI && "Expected analysis to be available");
 196   BFI->setBlockFreq(BB, Freq);
 197 }
 198
 199 void BlockFrequencyInfo::setBlockFreqAndScale(
 200     const BasicBlock *ReferenceBB, uint64_t Freq,
 201     SmallPtrSetImpl<BasicBlock *> &BlocksToScale) {
 202   assert(BFI && "Expected analysis to be available");
 203   // Use 128 bits APInt to avoid overflow.
 204   APInt NewFreq(128, Freq);
 205   APInt OldFreq(128, BFI->getBlockFreq(ReferenceBB).getFrequency());
 206   APInt BBFreq(128, 0);
 207   for (auto *BB : BlocksToScale) {
 208     BBFreq = BFI->getBlockFreq(BB).getFrequency();
 209     // Multiply first by NewFreq and then divide by OldFreq
 210     // to minimize loss of precision.
 211     BBFreq *= NewFreq;
 212     // udiv is an expensive operation in the general case. If this ends up being
 213     // a hot spot, one of the options proposed in
 214     // https://reviews.llvm.org/D28535#650071 could be used to avoid this.
 215     BBFreq = BBFreq.udiv(OldFreq);
 216     BFI->setBlockFreq(BB, BBFreq.getLimitedValue());
 217   }
 218   BFI->setBlockFreq(ReferenceBB, Freq);
 219 }
 220
 221 /// Pop up a ghostview window with the current block frequency propagation
 222 /// rendered using dot.
 223 void BlockFrequencyInfo::view() const {
 224   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
 225 }
 226
 227 const Function *BlockFrequencyInfo::getFunction() const {
 228   return BFI ? BFI->getFunction() : nullptr;
 229 }
 230
 231 const BranchProbabilityInfo *BlockFrequencyInfo::getBPI() const {
 232   return BFI ? &BFI->getBPI() : nullptr;
 233 }
 234
 235 raw_ostream &BlockFrequencyInfo::
 236 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
 237   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
 238 }
 239
 240 raw_ostream &
 241 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
 242                                    const BasicBlock *BB) const {
 243   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
 244 }
 245
 246 uint64_t BlockFrequencyInfo::getEntryFreq() const {
 247   return BFI ? BFI->getEntryFreq() : 0;
 248 }
 249
 250 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
 251
 252 void BlockFrequencyInfo::print(raw_ostream &OS) const {
 253   if (BFI)
 254     BFI->print(OS);
 255 }
 256
 257
 258 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
 259                       "Block Frequency Analysis", true, true)
 260 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
 261 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 262 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
 263                     "Block Frequency Analysis", true, true)
 264
 265 char BlockFrequencyInfoWrapperPass::ID = 0;
 266
 267
 268 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
 269     : FunctionPass(ID) {
 270   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 271 }
 272
 273 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
 274
 275 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
 276                                           const Module *) const {
 277   BFI.print(OS);
 278 }
 279
 280 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 281   AU.addRequired<BranchProbabilityInfoWrapperPass>();
 282   AU.addRequired<LoopInfoWrapperPass>();
 283   AU.setPreservesAll();
 284 }
 285
 286 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
 287
 288 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
 289   BranchProbabilityInfo &BPI =
 290       getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
 291   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
 292   BFI.calculate(F, BPI, LI);
 293   return false;
 294 }
 295
 296 AnalysisKey BlockFrequencyAnalysis::Key;
 297 BlockFrequencyInfo BlockFrequencyAnalysis::run(Function &F,
 298                                                FunctionAnalysisManager &AM) {
 299   BlockFrequencyInfo BFI;
 300   BFI.calculate(F, AM.getResult<BranchProbabilityAnalysis>(F),
 301                 AM.getResult<LoopAnalysis>(F));
 302   return BFI;
 303 }
 304
 305 PreservedAnalyses
 306 BlockFrequencyPrinterPass::run(Function &F, FunctionAnalysisManager &AM) {
 307   OS << "Printing analysis results of BFI for function "
 308      << "'" << F.getName() << "':"
 309      << "\n";
 310   AM.getResult<BlockFrequencyAnalysis>(F).print(OS);
 311   return PreservedAnalyses::all();
 312 }