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/ADT/APInt.h"
  16 #include "llvm/ADT/None.h"
  17 #include "llvm/ADT/iterator.h"
  18 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
  19 #include "llvm/Analysis/BranchProbabilityInfo.h"
  20 #include "llvm/Analysis/LoopInfo.h"
  21 #include "llvm/IR/CFG.h"
  22 #include "llvm/IR/Function.h"
  23 #include "llvm/IR/PassManager.h"
  24 #include "llvm/Pass.h"
  25 #include "llvm/Support/CommandLine.h"
  26 #include "llvm/Support/GraphWriter.h"
  27 #include "llvm/Support/raw_ostream.h"
  28 #include <algorithm>
  29 #include <cassert>
  30 #include <string>
  31
  32 using namespace llvm;
  33
  34 #define DEBUG_TYPE "block-freq"
  35
  36 static cl::opt<GVDAGType> ViewBlockFreqPropagationDAG(
  37     "view-block-freq-propagation-dags", cl::Hidden,
  38     cl::desc("Pop up a window to show a dag displaying how block "
  39              "frequencies propagation through the CFG."),
  40     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
  41                clEnumValN(GVDT_Fraction, "fraction",
  42                           "display a graph using the "
  43                           "fractional block frequency representation."),
  44                clEnumValN(GVDT_Integer, "integer",
  45                           "display a graph using the raw "
  46                           "integer fractional block frequency representation."),
  47                clEnumValN(GVDT_Count, "count", "display a graph using the real "
  48                                                "profile count if available.")));
  49
  50 cl::opt<std::string>
  51     ViewBlockFreqFuncName("view-bfi-func-name", cl::Hidden,
  52                           cl::desc("The option to specify "
  53                                    "the name of the function "
  54                                    "whose CFG will be displayed."));
  55
  56 cl::opt<unsigned>
  57     ViewHotFreqPercent("view-hot-freq-percent", cl::init(10), cl::Hidden,
  58                        cl::desc("An integer in percent used to specify "
  59                                 "the hot blocks/edges to be displayed "
  60                                 "in red: a block or edge whose frequency "
  61                                 "is no less than the max frequency of the "
  62                                 "function multiplied by this percent."));
  63
  64 // Command line option to turn on CFG dot or text dump after profile annotation.
  65 cl::opt<PGOViewCountsType> PGOViewCounts(
  66     "pgo-view-counts", cl::Hidden,
  67     cl::desc("A boolean option to show CFG dag or text with "
  68              "block profile counts and branch probabilities "
  69              "right after PGO profile annotation step. The "
  70              "profile counts are computed using branch "
  71              "probabilities from the runtime profile data and "
  72              "block frequency propagation algorithm. To view "
  73              "the raw counts from the profile, use option "
  74              "-pgo-view-raw-counts instead. To limit graph "
  75              "display to only one function, use filtering option "
  76              "-view-bfi-func-name."),
  77     cl::values(clEnumValN(PGOVCT_None, "none", "do not show."),
  78                clEnumValN(PGOVCT_Graph, "graph", "show a graph."),
  79                clEnumValN(PGOVCT_Text, "text", "show in text.")));
  80
  81 static cl::opt<bool> PrintBlockFreq(
  82     "print-bfi", cl::init(false), cl::Hidden,
  83     cl::desc("Print the block frequency info."));
  84
  85 cl::opt<std::string> PrintBlockFreqFuncName(
  86     "print-bfi-func-name", cl::Hidden,
  87     cl::desc("The option to specify the name of the function "
  88              "whose block frequency info is printed."));
  89
  90 namespace llvm {
  91
  92 static GVDAGType getGVDT() {
  93   if (PGOViewCounts == PGOVCT_Graph)
  94     return GVDT_Count;
  95   return ViewBlockFreqPropagationDAG;
  96 }
  97
  98 template <>
  99 struct GraphTraits<BlockFrequencyInfo *> {
 100   using NodeRef = const BasicBlock *;
 101   using ChildIteratorType = succ_const_iterator;
 102   using nodes_iterator = pointer_iterator<Function::const_iterator>;
 103
 104   static NodeRef getEntryNode(const BlockFrequencyInfo *G) {
 105     return &G->getFunction()->front();
 106   }
 107
 108   static ChildIteratorType child_begin(const NodeRef N) {
 109     return succ_begin(N);
 110   }
 111
 112   static ChildIteratorType child_end(const NodeRef N) { return succ_end(N); }
 113
 114   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
 115     return nodes_iterator(G->getFunction()->begin());
 116   }
 117
 118   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
 119     return nodes_iterator(G->getFunction()->end());
 120   }
 121 };
 122
 123 using BFIDOTGTraitsBase =
 124     BFIDOTGraphTraitsBase<BlockFrequencyInfo, BranchProbabilityInfo>;
 125
 126 template <>
 127 struct DOTGraphTraits<BlockFrequencyInfo *> : public BFIDOTGTraitsBase {
 128   explicit DOTGraphTraits(bool isSimple = false)
 129       : BFIDOTGTraitsBase(isSimple) {}
 130
 131   std::string getNodeLabel(const BasicBlock *Node,
 132                            const BlockFrequencyInfo *Graph) {
 133
 134     return BFIDOTGTraitsBase::getNodeLabel(Node, Graph, getGVDT());
 135   }
 136
 137   std::string getNodeAttributes(const BasicBlock *Node,
 138                                 const BlockFrequencyInfo *Graph) {
 139     return BFIDOTGTraitsBase::getNodeAttributes(Node, Graph,
 140                                                 ViewHotFreqPercent);
 141   }
 142
 143   std::string getEdgeAttributes(const BasicBlock *Node, EdgeIter EI,
 144                                 const BlockFrequencyInfo *BFI) {
 145     return BFIDOTGTraitsBase::getEdgeAttributes(Node, EI, BFI, BFI->getBPI(),
 146                                                 ViewHotFreqPercent);
 147   }
 148 };
 149
 150 } // end namespace llvm
 151
 152 BlockFrequencyInfo::BlockFrequencyInfo() = default;
 153
 154 BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
 155                                        const BranchProbabilityInfo &BPI,
 156                                        const LoopInfo &LI) {
 157   calculate(F, BPI, LI);
 158 }
 159
 160 BlockFrequencyInfo::BlockFrequencyInfo(BlockFrequencyInfo &&Arg)
 161     : BFI(std::move(Arg.BFI)) {}
 162
 163 BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
 164   releaseMemory();
 165   BFI = std::move(RHS.BFI);
 166   return *this;
 167 }
 168
 169 // Explicitly define the default constructor otherwise it would be implicitly
 170 // defined at the first ODR-use which is the BFI member in the
 171 // LazyBlockFrequencyInfo header.  The dtor needs the BlockFrequencyInfoImpl
 172 // template instantiated which is not available in the header.
 173 BlockFrequencyInfo::~BlockFrequencyInfo() = default;
 174
 175 bool BlockFrequencyInfo::invalidate(Function &F, const PreservedAnalyses &PA,
 176                                     FunctionAnalysisManager::Invalidator &) {
 177   // Check whether the analysis, all analyses on functions, or the function's
 178   // CFG have been preserved.
 179   auto PAC = PA.getChecker<BlockFrequencyAnalysis>();
 180   return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
 181            PAC.preservedSet<CFGAnalyses>());
 182 }
 183
 184 void BlockFrequencyInfo::calculate(const Function &F,
 185                                    const BranchProbabilityInfo &BPI,
 186                                    const LoopInfo &LI) {
 187   if (!BFI)
 188     BFI.reset(new ImplType);
 189   BFI->calculate(F, BPI, LI);
 190   if (ViewBlockFreqPropagationDAG != GVDT_None &&
 191       (ViewBlockFreqFuncName.empty() ||
 192        F.getName().equals(ViewBlockFreqFuncName))) {
 193     view();
 194   }
 195   if (PrintBlockFreq &&
 196       (PrintBlockFreqFuncName.empty() ||
 197        F.getName().equals(PrintBlockFreqFuncName))) {
 198     print(dbgs());
 199   }
 200 }
 201
 202 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
 203   return BFI ? BFI->getBlockFreq(BB) : 0;
 204 }
 205
 206 Optional<uint64_t>
 207 BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB) const {
 208   if (!BFI)
 209     return None;
 210
 211   return BFI->getBlockProfileCount(*getFunction(), BB);
 212 }
 213
 214 Optional<uint64_t>
 215 BlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
 216   if (!BFI)
 217     return None;
 218   return BFI->getProfileCountFromFreq(*getFunction(), Freq);
 219 }
 220
 221 bool BlockFrequencyInfo::isIrrLoopHeader(const BasicBlock *BB) {
 222   assert(BFI && "Expected analysis to be available");
 223   return BFI->isIrrLoopHeader(BB);
 224 }
 225
 226 void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB, uint64_t Freq) {
 227   assert(BFI && "Expected analysis to be available");
 228   BFI->setBlockFreq(BB, Freq);
 229 }
 230
 231 void BlockFrequencyInfo::setBlockFreqAndScale(
 232     const BasicBlock *ReferenceBB, uint64_t Freq,
 233     SmallPtrSetImpl<BasicBlock *> &BlocksToScale) {
 234   assert(BFI && "Expected analysis to be available");
 235   // Use 128 bits APInt to avoid overflow.
 236   APInt NewFreq(128, Freq);
 237   APInt OldFreq(128, BFI->getBlockFreq(ReferenceBB).getFrequency());
 238   APInt BBFreq(128, 0);
 239   for (auto *BB : BlocksToScale) {
 240     BBFreq = BFI->getBlockFreq(BB).getFrequency();
 241     // Multiply first by NewFreq and then divide by OldFreq
 242     // to minimize loss of precision.
 243     BBFreq *= NewFreq;
 244     // udiv is an expensive operation in the general case. If this ends up being
 245     // a hot spot, one of the options proposed in
 246     // https://reviews.llvm.org/D28535#650071 could be used to avoid this.
 247     BBFreq = BBFreq.udiv(OldFreq);
 248     BFI->setBlockFreq(BB, BBFreq.getLimitedValue());
 249   }
 250   BFI->setBlockFreq(ReferenceBB, Freq);
 251 }
 252
 253 /// Pop up a ghostview window with the current block frequency propagation
 254 /// rendered using dot.
 255 void BlockFrequencyInfo::view() const {
 256   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
 257 }
 258
 259 const Function *BlockFrequencyInfo::getFunction() const {
 260   return BFI ? BFI->getFunction() : nullptr;
 261 }
 262
 263 const BranchProbabilityInfo *BlockFrequencyInfo::getBPI() const {
 264   return BFI ? &BFI->getBPI() : nullptr;
 265 }
 266
 267 raw_ostream &BlockFrequencyInfo::
 268 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
 269   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
 270 }
 271
 272 raw_ostream &
 273 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
 274                                    const BasicBlock *BB) const {
 275   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
 276 }
 277
 278 uint64_t BlockFrequencyInfo::getEntryFreq() const {
 279   return BFI ? BFI->getEntryFreq() : 0;
 280 }
 281
 282 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
 283
 284 void BlockFrequencyInfo::print(raw_ostream &OS) const {
 285   if (BFI)
 286     BFI->print(OS);
 287 }
 288
 289 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
 290                       "Block Frequency Analysis", true, true)
 291 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
 292 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 293 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
 294                     "Block Frequency Analysis", true, true)
 295
 296 char BlockFrequencyInfoWrapperPass::ID = 0;
 297
 298 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
 299     : FunctionPass(ID) {
 300   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 301 }
 302
 303 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() = default;
 304
 305 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
 306                                           const Module *) const {
 307   BFI.print(OS);
 308 }
 309
 310 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 311   AU.addRequired<BranchProbabilityInfoWrapperPass>();
 312   AU.addRequired<LoopInfoWrapperPass>();
 313   AU.setPreservesAll();
 314 }
 315
 316 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
 317
 318 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
 319   BranchProbabilityInfo &BPI =
 320       getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
 321   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
 322   BFI.calculate(F, BPI, LI);
 323   return false;
 324 }
 325
 326 AnalysisKey BlockFrequencyAnalysis::Key;
 327 BlockFrequencyInfo BlockFrequencyAnalysis::run(Function &F,
 328                                                FunctionAnalysisManager &AM) {
 329   BlockFrequencyInfo BFI;
 330   BFI.calculate(F, AM.getResult<BranchProbabilityAnalysis>(F),
 331                 AM.getResult<LoopAnalysis>(F));
 332   return BFI;
 333 }
 334
 335 PreservedAnalyses
 336 BlockFrequencyPrinterPass::run(Function &F, FunctionAnalysisManager &AM) {
 337   OS << "Printing analysis results of BFI for function "
 338      << "'" << F.getName() << "':"
 339      << "\n";
 340   AM.getResult<BlockFrequencyAnalysis>(F).print(OS);
 341   return PreservedAnalyses::all();
 342 }