llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp

   1 //===- MachineBlockFrequencyInfo.cpp - MBB Frequency Analysis -------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Loops should be simplified before this analysis.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
  14 #include "llvm/ADT/DenseMap.h"
  15 #include "llvm/ADT/iterator.h"
  16 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
  17 #include "llvm/CodeGen/MachineBasicBlock.h"
  18 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineLoopInfo.h"
  21 #include "llvm/InitializePasses.h"
  22 #include "llvm/Pass.h"
  23 #include "llvm/Support/CommandLine.h"
  24 #include "llvm/Support/GraphWriter.h"
  25 #include <optional>
  26 #include <string>
  27
  28 using namespace llvm;
  29
  30 #define DEBUG_TYPE "machine-block-freq"
  31
  32 namespace llvm {
  33 static cl::opt<GVDAGType> ViewMachineBlockFreqPropagationDAG(
  34     "view-machine-block-freq-propagation-dags", cl::Hidden,
  35     cl::desc("Pop up a window to show a dag displaying how machine block "
  36              "frequencies propagate through the CFG."),
  37     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
  38                clEnumValN(GVDT_Fraction, "fraction",
  39                           "display a graph using the "
  40                           "fractional block frequency representation."),
  41                clEnumValN(GVDT_Integer, "integer",
  42                           "display a graph using the raw "
  43                           "integer fractional block frequency representation."),
  44                clEnumValN(GVDT_Count, "count", "display a graph using the real "
  45                                                "profile count if available.")));
  46
  47 // Similar option above, but used to control BFI display only after MBP pass
  48 cl::opt<GVDAGType> ViewBlockLayoutWithBFI(
  49     "view-block-layout-with-bfi", cl::Hidden,
  50     cl::desc(
  51         "Pop up a window to show a dag displaying MBP layout and associated "
  52         "block frequencies of the CFG."),
  53     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
  54                clEnumValN(GVDT_Fraction, "fraction",
  55                           "display a graph using the "
  56                           "fractional block frequency representation."),
  57                clEnumValN(GVDT_Integer, "integer",
  58                           "display a graph using the raw "
  59                           "integer fractional block frequency representation."),
  60                clEnumValN(GVDT_Count, "count",
  61                           "display a graph using the real "
  62                           "profile count if available.")));
  63
  64 // Command line option to specify the name of the function for CFG dump
  65 // Defined in Analysis/BlockFrequencyInfo.cpp:  -view-bfi-func-name=
  66 extern cl::opt<std::string> ViewBlockFreqFuncName;
  67
  68 // Command line option to specify hot frequency threshold.
  69 // Defined in Analysis/BlockFrequencyInfo.cpp:  -view-hot-freq-perc=
  70 extern cl::opt<unsigned> ViewHotFreqPercent;
  71
  72 static cl::opt<bool> PrintMachineBlockFreq(
  73     "print-machine-bfi", cl::init(false), cl::Hidden,
  74     cl::desc("Print the machine block frequency info."));
  75
  76 // Command line option to specify the name of the function for block frequency
  77 // dump. Defined in Analysis/BlockFrequencyInfo.cpp.
  78 extern cl::opt<std::string> PrintBFIFuncName;
  79 } // namespace llvm
  80
  81 static GVDAGType getGVDT() {
  82   if (ViewBlockLayoutWithBFI != GVDT_None)
  83     return ViewBlockLayoutWithBFI;
  84
  85   return ViewMachineBlockFreqPropagationDAG;
  86 }
  87
  88 namespace llvm {
  89
  90 template <> struct GraphTraits<MachineBlockFrequencyInfo *> {
  91   using NodeRef = const MachineBasicBlock *;
  92   using ChildIteratorType = MachineBasicBlock::const_succ_iterator;
  93   using nodes_iterator = pointer_iterator<MachineFunction::const_iterator>;
  94
  95   static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
  96     return &G->getFunction()->front();
  97   }
  98
  99   static ChildIteratorType child_begin(const NodeRef N) {
 100     return N->succ_begin();
 101   }
 102
 103   static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
 104
 105   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
 106     return nodes_iterator(G->getFunction()->begin());
 107   }
 108
 109   static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
 110     return nodes_iterator(G->getFunction()->end());
 111   }
 112 };
 113
 114 using MBFIDOTGraphTraitsBase =
 115     BFIDOTGraphTraitsBase<MachineBlockFrequencyInfo,
 116                           MachineBranchProbabilityInfo>;
 117
 118 template <>
 119 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
 120     : public MBFIDOTGraphTraitsBase {
 121   const MachineFunction *CurFunc = nullptr;
 122   DenseMap<const MachineBasicBlock *, int> LayoutOrderMap;
 123
 124   explicit DOTGraphTraits(bool isSimple = false)
 125       : MBFIDOTGraphTraitsBase(isSimple) {}
 126
 127   std::string getNodeLabel(const MachineBasicBlock *Node,
 128                            const MachineBlockFrequencyInfo *Graph) {
 129     int layout_order = -1;
 130     // Attach additional ordering information if 'isSimple' is false.
 131     if (!isSimple()) {
 132       const MachineFunction *F = Node->getParent();
 133       if (!CurFunc || F != CurFunc) {
 134         if (CurFunc)
 135           LayoutOrderMap.clear();
 136
 137         CurFunc = F;
 138         int O = 0;
 139         for (auto MBI = F->begin(); MBI != F->end(); ++MBI, ++O) {
 140           LayoutOrderMap[&*MBI] = O;
 141         }
 142       }
 143       layout_order = LayoutOrderMap[Node];
 144     }
 145     return MBFIDOTGraphTraitsBase::getNodeLabel(Node, Graph, getGVDT(),
 146                                                 layout_order);
 147   }
 148
 149   std::string getNodeAttributes(const MachineBasicBlock *Node,
 150                                 const MachineBlockFrequencyInfo *Graph) {
 151     return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
 152                                                      ViewHotFreqPercent);
 153   }
 154
 155   std::string getEdgeAttributes(const MachineBasicBlock *Node, EdgeIter EI,
 156                                 const MachineBlockFrequencyInfo *MBFI) {
 157     return MBFIDOTGraphTraitsBase::getEdgeAttributes(
 158         Node, EI, MBFI, MBFI->getMBPI(), ViewHotFreqPercent);
 159   }
 160 };
 161
 162 } // end namespace llvm
 163
 164 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, DEBUG_TYPE,
 165                       "Machine Block Frequency Analysis", true, true)
 166 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
 167 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
 168 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, DEBUG_TYPE,
 169                     "Machine Block Frequency Analysis", true, true)
 170
 171 char MachineBlockFrequencyInfo::ID = 0;
 172
 173 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
 174     : MachineFunctionPass(ID) {
 175   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
 176 }
 177
 178 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo(
 179       MachineFunction &F,
 180       MachineBranchProbabilityInfo &MBPI,
 181       MachineLoopInfo &MLI) : MachineFunctionPass(ID) {
 182   calculate(F, MBPI, MLI);
 183 }
 184
 185 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() = default;
 186
 187 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
 188   AU.addRequired<MachineBranchProbabilityInfo>();
 189   AU.addRequired<MachineLoopInfo>();
 190   AU.setPreservesAll();
 191   MachineFunctionPass::getAnalysisUsage(AU);
 192 }
 193
 194 void MachineBlockFrequencyInfo::calculate(
 195     const MachineFunction &F, const MachineBranchProbabilityInfo &MBPI,
 196     const MachineLoopInfo &MLI) {
 197   if (!MBFI)
 198     MBFI.reset(new ImplType);
 199   MBFI->calculate(F, MBPI, MLI);
 200   if (ViewMachineBlockFreqPropagationDAG != GVDT_None &&
 201       (ViewBlockFreqFuncName.empty() ||
 202        F.getName().equals(ViewBlockFreqFuncName))) {
 203     view("MachineBlockFrequencyDAGS." + F.getName());
 204   }
 205   if (PrintMachineBlockFreq &&
 206       (PrintBFIFuncName.empty() || F.getName().equals(PrintBFIFuncName))) {
 207     MBFI->print(dbgs());
 208   }
 209 }
 210
 211 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
 212   MachineBranchProbabilityInfo &MBPI =
 213       getAnalysis<MachineBranchProbabilityInfo>();
 214   MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
 215   calculate(F, MBPI, MLI);
 216   return false;
 217 }
 218
 219 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
 220
 221 /// Pop up a ghostview window with the current block frequency propagation
 222 /// rendered using dot.
 223 void MachineBlockFrequencyInfo::view(const Twine &Name, bool isSimple) const {
 224   // This code is only for debugging.
 225   ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this), Name, isSimple);
 226 }
 227
 228 BlockFrequency
 229 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
 230   return MBFI ? MBFI->getBlockFreq(MBB) : BlockFrequency(0);
 231 }
 232
 233 std::optional<uint64_t> MachineBlockFrequencyInfo::getBlockProfileCount(
 234     const MachineBasicBlock *MBB) const {
 235   if (!MBFI)
 236     return std::nullopt;
 237
 238   const Function &F = MBFI->getFunction()->getFunction();
 239   return MBFI->getBlockProfileCount(F, MBB);
 240 }
 241
 242 std::optional<uint64_t>
 243 MachineBlockFrequencyInfo::getProfileCountFromFreq(BlockFrequency Freq) const {
 244   if (!MBFI)
 245     return std::nullopt;
 246
 247   const Function &F = MBFI->getFunction()->getFunction();
 248   return MBFI->getProfileCountFromFreq(F, Freq);
 249 }
 250
 251 bool MachineBlockFrequencyInfo::isIrrLoopHeader(
 252     const MachineBasicBlock *MBB) const {
 253   assert(MBFI && "Expected analysis to be available");
 254   return MBFI->isIrrLoopHeader(MBB);
 255 }
 256
 257 void MachineBlockFrequencyInfo::onEdgeSplit(
 258     const MachineBasicBlock &NewPredecessor,
 259     const MachineBasicBlock &NewSuccessor,
 260     const MachineBranchProbabilityInfo &MBPI) {
 261   assert(MBFI && "Expected analysis to be available");
 262   auto NewSuccFreq = MBFI->getBlockFreq(&NewPredecessor) *
 263                      MBPI.getEdgeProbability(&NewPredecessor, &NewSuccessor);
 264
 265   MBFI->setBlockFreq(&NewSuccessor, NewSuccFreq);
 266 }
 267
 268 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
 269   return MBFI ? MBFI->getFunction() : nullptr;
 270 }
 271
 272 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
 273   return MBFI ? &MBFI->getBPI() : nullptr;
 274 }
 275
 276 BlockFrequency MachineBlockFrequencyInfo::getEntryFreq() const {
 277   return MBFI ? MBFI->getEntryFreq() : BlockFrequency(0);
 278 }
 279
 280 Printable llvm::printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
 281                                BlockFrequency Freq) {
 282   return Printable([&MBFI, Freq](raw_ostream &OS) {
 283     printBlockFreqImpl(OS, MBFI.getEntryFreq(), Freq);
 284   });
 285 }
 286
 287 Printable llvm::printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
 288                                const MachineBasicBlock &MBB) {
 289   return printBlockFreq(MBFI, MBFI.getBlockFreq(&MBB));
 290 }