llvm/lib/CodeGen/MIRSampleProfile.cpp

   1 //===-------- MIRSampleProfile.cpp: MIRSampleFDO (For FSAFDO) -------------===//
   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 // This file provides the implementation of the MIRSampleProfile loader, mainly
  10 // for flow sensitive SampleFDO.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/CodeGen/MIRSampleProfile.h"
  15 #include "llvm/ADT/DenseMap.h"
  16 #include "llvm/ADT/DenseSet.h"
  17 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
  18 #include "llvm/IR/Function.h"
  19 #include "llvm/Support/CommandLine.h"
  20 #include "llvm/Support/Debug.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 #include "llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h"
  23 #include "llvm/Transforms/Utils/SampleProfileLoaderBaseUtil.h"
  24
  25 using namespace llvm;
  26 using namespace sampleprof;
  27 using namespace llvm::sampleprofutil;
  28 using ProfileCount = Function::ProfileCount;
  29
  30 #define DEBUG_TYPE "fs-profile-loader"
  31
  32 static cl::opt<bool> ShowFSBranchProb(
  33     "show-fs-branchprob", cl::Hidden, cl::init(false),
  34     cl::desc("Print setting flow sensitive branch probabilities"));
  35 static cl::opt<unsigned> FSProfileDebugProbDiffThreshold(
  36     "fs-profile-debug-prob-diff-threshold", cl::init(10),
  37     cl::desc("Only show debug message if the branch probility is greater than "
  38              "this value (in percentage)."));
  39
  40 static cl::opt<unsigned> FSProfileDebugBWThreshold(
  41     "fs-profile-debug-bw-threshold", cl::init(10000),
  42     cl::desc("Only show debug message if the source branch weight is greater "
  43              " than this value."));
  44
  45 static cl::opt<bool> ViewBFIBefore("fs-viewbfi-before", cl::Hidden,
  46                                    cl::init(false),
  47                                    cl::desc("View BFI before MIR loader"));
  48 static cl::opt<bool> ViewBFIAfter("fs-viewbfi-after", cl::Hidden,
  49                                   cl::init(false),
  50                                   cl::desc("View BFI after MIR loader"));
  51
  52 char MIRProfileLoaderPass::ID = 0;
  53
  54 INITIALIZE_PASS_BEGIN(MIRProfileLoaderPass, DEBUG_TYPE,
  55                       "Load MIR Sample Profile",
  56                       /* cfg = */ false, /* is_analysis = */ false)
  57 INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfo)
  58 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
  59 INITIALIZE_PASS_DEPENDENCY(MachinePostDominatorTree)
  60 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
  61 INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass)
  62 INITIALIZE_PASS_END(MIRProfileLoaderPass, DEBUG_TYPE, "Load MIR Sample Profile",
  63                     /* cfg = */ false, /* is_analysis = */ false)
  64
  65 char &llvm::MIRProfileLoaderPassID = MIRProfileLoaderPass::ID;
  66
  67 FunctionPass *llvm::createMIRProfileLoaderPass(std::string File,
  68                                                std::string RemappingFile,
  69                                                FSDiscriminatorPass P) {
  70   return new MIRProfileLoaderPass(File, RemappingFile, P);
  71 }
  72
  73 namespace llvm {
  74
  75 // Internal option used to control BFI display only after MBP pass.
  76 // Defined in CodeGen/MachineBlockFrequencyInfo.cpp:
  77 // -view-block-layout-with-bfi={none | fraction | integer | count}
  78 extern cl::opt<GVDAGType> ViewBlockLayoutWithBFI;
  79
  80 // Command line option to specify the name of the function for CFG dump
  81 // Defined in Analysis/BlockFrequencyInfo.cpp:  -view-bfi-func-name=
  82 extern cl::opt<std::string> ViewBlockFreqFuncName;
  83
  84 namespace afdo_detail {
  85 template <> struct IRTraits<MachineBasicBlock> {
  86   using InstructionT = MachineInstr;
  87   using BasicBlockT = MachineBasicBlock;
  88   using FunctionT = MachineFunction;
  89   using BlockFrequencyInfoT = MachineBlockFrequencyInfo;
  90   using LoopT = MachineLoop;
  91   using LoopInfoPtrT = MachineLoopInfo *;
  92   using DominatorTreePtrT = MachineDominatorTree *;
  93   using PostDominatorTreePtrT = MachinePostDominatorTree *;
  94   using PostDominatorTreeT = MachinePostDominatorTree;
  95   using OptRemarkEmitterT = MachineOptimizationRemarkEmitter;
  96   using OptRemarkAnalysisT = MachineOptimizationRemarkAnalysis;
  97   using PredRangeT = iterator_range<std::vector<MachineBasicBlock *>::iterator>;
  98   using SuccRangeT = iterator_range<std::vector<MachineBasicBlock *>::iterator>;
  99   static Function &getFunction(MachineFunction &F) { return F.getFunction(); }
 100   static const MachineBasicBlock *getEntryBB(const MachineFunction *F) {
 101     return GraphTraits<const MachineFunction *>::getEntryNode(F);
 102   }
 103   static PredRangeT getPredecessors(MachineBasicBlock *BB) {
 104     return BB->predecessors();
 105   }
 106   static SuccRangeT getSuccessors(MachineBasicBlock *BB) {
 107     return BB->successors();
 108   }
 109 };
 110 } // namespace afdo_detail
 111
 112 class MIRProfileLoader final
 113     : public SampleProfileLoaderBaseImpl<MachineBasicBlock> {
 114 public:
 115   void setInitVals(MachineDominatorTree *MDT, MachinePostDominatorTree *MPDT,
 116                    MachineLoopInfo *MLI, MachineBlockFrequencyInfo *MBFI,
 117                    MachineOptimizationRemarkEmitter *MORE) {
 118     DT = MDT;
 119     PDT = MPDT;
 120     LI = MLI;
 121     BFI = MBFI;
 122     ORE = MORE;
 123   }
 124   void setFSPass(FSDiscriminatorPass Pass) {
 125     P = Pass;
 126     LowBit = getFSPassBitBegin(P);
 127     HighBit = getFSPassBitEnd(P);
 128     assert(LowBit < HighBit && "HighBit needs to be greater than Lowbit");
 129   }
 130
 131   MIRProfileLoader(StringRef Name, StringRef RemapName)
 132       : SampleProfileLoaderBaseImpl(std::string(Name), std::string(RemapName)) {
 133   }
 134
 135   void setBranchProbs(MachineFunction &F);
 136   bool runOnFunction(MachineFunction &F);
 137   bool doInitialization(Module &M);
 138   bool isValid() const { return ProfileIsValid; }
 139
 140 protected:
 141   friend class SampleCoverageTracker;
 142
 143   /// Hold the information of the basic block frequency.
 144   MachineBlockFrequencyInfo *BFI;
 145
 146   /// PassNum is the sequence number this pass is called, start from 1.
 147   FSDiscriminatorPass P;
 148
 149   // LowBit in the FS discriminator used by this instance. Note the number is
 150   // 0-based. Base discrimnator use bit 0 to bit 11.
 151   unsigned LowBit;
 152   // HighwBit in the FS discriminator used by this instance. Note the number
 153   // is 0-based.
 154   unsigned HighBit;
 155
 156   bool ProfileIsValid = true;
 157 };
 158
 159 template <>
 160 void SampleProfileLoaderBaseImpl<
 161     MachineBasicBlock>::computeDominanceAndLoopInfo(MachineFunction &F) {}
 162
 163 void MIRProfileLoader::setBranchProbs(MachineFunction &F) {
 164   LLVM_DEBUG(dbgs() << "\nPropagation complete. Setting branch probs\n");
 165   for (auto &BI : F) {
 166     MachineBasicBlock *BB = &BI;
 167     if (BB->succ_size() < 2)
 168       continue;
 169     const MachineBasicBlock *EC = EquivalenceClass[BB];
 170     uint64_t BBWeight = BlockWeights[EC];
 171     uint64_t SumEdgeWeight = 0;
 172     for (MachineBasicBlock *Succ : BB->successors()) {
 173       Edge E = std::make_pair(BB, Succ);
 174       SumEdgeWeight += EdgeWeights[E];
 175     }
 176
 177     if (BBWeight != SumEdgeWeight) {
 178       LLVM_DEBUG(dbgs() << "BBweight is not equal to SumEdgeWeight: BBWWeight="
 179                         << BBWeight << " SumEdgeWeight= " << SumEdgeWeight
 180                         << "\n");
 181       BBWeight = SumEdgeWeight;
 182     }
 183     if (BBWeight == 0) {
 184       LLVM_DEBUG(dbgs() << "SKIPPED. All branch weights are zero.\n");
 185       continue;
 186     }
 187
 188 #ifndef NDEBUG
 189     uint64_t BBWeightOrig = BBWeight;
 190 #endif
 191     uint32_t MaxWeight = std::numeric_limits<uint32_t>::max();
 192     uint32_t Factor = 1;
 193     if (BBWeight > MaxWeight) {
 194       Factor = BBWeight / MaxWeight + 1;
 195       BBWeight /= Factor;
 196       LLVM_DEBUG(dbgs() << "Scaling weights by " << Factor << "\n");
 197     }
 198
 199     for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
 200                                           SE = BB->succ_end();
 201          SI != SE; ++SI) {
 202       MachineBasicBlock *Succ = *SI;
 203       Edge E = std::make_pair(BB, Succ);
 204       uint64_t EdgeWeight = EdgeWeights[E];
 205       EdgeWeight /= Factor;
 206
 207       assert(BBWeight >= EdgeWeight &&
 208              "BBweight is larger than EdgeWeight -- should not happen.\n");
 209
 210       BranchProbability OldProb = BFI->getMBPI()->getEdgeProbability(BB, SI);
 211       BranchProbability NewProb(EdgeWeight, BBWeight);
 212       if (OldProb == NewProb)
 213         continue;
 214       BB->setSuccProbability(SI, NewProb);
 215 #ifndef NDEBUG
 216       if (!ShowFSBranchProb)
 217         continue;
 218       bool Show = false;
 219       BranchProbability Diff;
 220       if (OldProb > NewProb)
 221         Diff = OldProb - NewProb;
 222       else
 223         Diff = NewProb - OldProb;
 224       Show = (Diff >= BranchProbability(FSProfileDebugProbDiffThreshold, 100));
 225       Show &= (BBWeightOrig >= FSProfileDebugBWThreshold);
 226
 227       auto DIL = BB->findBranchDebugLoc();
 228       auto SuccDIL = Succ->findBranchDebugLoc();
 229       if (Show) {
 230         dbgs() << "Set branch fs prob: MBB (" << BB->getNumber() << " -> "
 231                << Succ->getNumber() << "): ";
 232         if (DIL)
 233           dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":"
 234                  << DIL->getColumn();
 235         if (SuccDIL)
 236           dbgs() << "-->" << SuccDIL->getFilename() << ":" << SuccDIL->getLine()
 237                  << ":" << SuccDIL->getColumn();
 238         dbgs() << " W=" << BBWeightOrig << "  " << OldProb << " --> " << NewProb
 239                << "\n";
 240       }
 241 #endif
 242     }
 243   }
 244 }
 245
 246 bool MIRProfileLoader::doInitialization(Module &M) {
 247   auto &Ctx = M.getContext();
 248
 249   auto ReaderOrErr = sampleprof::SampleProfileReader::create(Filename, Ctx, P,
 250                                                              RemappingFilename);
 251   if (std::error_code EC = ReaderOrErr.getError()) {
 252     std::string Msg = "Could not open profile: " + EC.message();
 253     Ctx.diagnose(DiagnosticInfoSampleProfile(Filename, Msg));
 254     return false;
 255   }
 256
 257   Reader = std::move(ReaderOrErr.get());
 258   Reader->setModule(&M);
 259   ProfileIsValid = (Reader->read() == sampleprof_error::success);
 260   Reader->getSummary();
 261
 262   return true;
 263 }
 264
 265 bool MIRProfileLoader::runOnFunction(MachineFunction &MF) {
 266   Function &Func = MF.getFunction();
 267   clearFunctionData(false);
 268   Samples = Reader->getSamplesFor(Func);
 269   if (!Samples || Samples->empty())
 270     return false;
 271
 272   if (getFunctionLoc(MF) == 0)
 273     return false;
 274
 275   DenseSet<GlobalValue::GUID> InlinedGUIDs;
 276   bool Changed = computeAndPropagateWeights(MF, InlinedGUIDs);
 277
 278   // Set the new BPI, BFI.
 279   setBranchProbs(MF);
 280
 281   return Changed;
 282 }
 283
 284 } // namespace llvm
 285
 286 MIRProfileLoaderPass::MIRProfileLoaderPass(std::string FileName,
 287                                            std::string RemappingFileName,
 288                                            FSDiscriminatorPass P)
 289     : MachineFunctionPass(ID), ProfileFileName(FileName), P(P),
 290       MIRSampleLoader(
 291           std::make_unique<MIRProfileLoader>(FileName, RemappingFileName)) {
 292   LowBit = getFSPassBitBegin(P);
 293   HighBit = getFSPassBitEnd(P);
 294   assert(LowBit < HighBit && "HighBit needs to be greater than Lowbit");
 295 }
 296
 297 bool MIRProfileLoaderPass::runOnMachineFunction(MachineFunction &MF) {
 298   if (!MIRSampleLoader->isValid())
 299     return false;
 300
 301   LLVM_DEBUG(dbgs() << "MIRProfileLoader pass working on Func: "
 302                     << MF.getFunction().getName() << "\n");
 303   MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
 304   MIRSampleLoader->setInitVals(
 305       &getAnalysis<MachineDominatorTree>(),
 306       &getAnalysis<MachinePostDominatorTree>(), &getAnalysis<MachineLoopInfo>(),
 307       MBFI, &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE());
 308
 309   MF.RenumberBlocks();
 310   if (ViewBFIBefore && ViewBlockLayoutWithBFI != GVDT_None &&
 311       (ViewBlockFreqFuncName.empty() ||
 312        MF.getFunction().getName().equals(ViewBlockFreqFuncName))) {
 313     MBFI->view("MIR_Prof_loader_b." + MF.getName(), false);
 314   }
 315
 316   bool Changed = MIRSampleLoader->runOnFunction(MF);
 317   if (Changed)
 318     MBFI->calculate(MF, *MBFI->getMBPI(), *&getAnalysis<MachineLoopInfo>());
 319
 320   if (ViewBFIAfter && ViewBlockLayoutWithBFI != GVDT_None &&
 321       (ViewBlockFreqFuncName.empty() ||
 322        MF.getFunction().getName().equals(ViewBlockFreqFuncName))) {
 323     MBFI->view("MIR_prof_loader_a." + MF.getName(), false);
 324   }
 325
 326   return Changed;
 327 }
 328
 329 bool MIRProfileLoaderPass::doInitialization(Module &M) {
 330   LLVM_DEBUG(dbgs() << "MIRProfileLoader pass working on Module " << M.getName()
 331                     << "\n");
 332
 333   MIRSampleLoader->setFSPass(P);
 334   return MIRSampleLoader->doInitialization(M);
 335 }
 336
 337 void MIRProfileLoaderPass::getAnalysisUsage(AnalysisUsage &AU) const {
 338   AU.setPreservesAll();
 339   AU.addRequired<MachineBlockFrequencyInfo>();
 340   AU.addRequired<MachineDominatorTree>();
 341   AU.addRequired<MachinePostDominatorTree>();
 342   AU.addRequiredTransitive<MachineLoopInfo>();
 343   AU.addRequired<MachineOptimizationRemarkEmitterPass>();
 344   MachineFunctionPass::getAnalysisUsage(AU);
 345 }