clang/lib/CodeGen/CodeGenPGO.h

   1 //===--- CodeGenPGO.h - PGO Instrumentation for LLVM CodeGen ----*- C++ -*-===//
   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 // Instrumentation-based profile-guided optimization
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
  14 #define LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
  15
  16 #include "CGBuilder.h"
  17 #include "CodeGenModule.h"
  18 #include "CodeGenTypes.h"
  19 #include "llvm/ProfileData/InstrProfReader.h"
  20 #include <array>
  21 #include <memory>
  22 #include <optional>
  23
  24 namespace clang {
  25 namespace CodeGen {
  26
  27 /// Per-function PGO state.
  28 class CodeGenPGO {
  29 private:
  30   CodeGenModule &CGM;
  31   std::string FuncName;
  32   llvm::GlobalVariable *FuncNameVar;
  33
  34   std::array <unsigned, llvm::IPVK_Last + 1> NumValueSites;
  35   unsigned NumRegionCounters;
  36   uint64_t FunctionHash;
  37   std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
  38   std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
  39   std::unique_ptr<llvm::InstrProfRecord> ProfRecord;
  40   std::vector<uint64_t> RegionCounts;
  41   uint64_t CurrentRegionCount;
  42
  43 public:
  44   CodeGenPGO(CodeGenModule &CGModule)
  45       : CGM(CGModule), FuncNameVar(nullptr), NumValueSites({{0}}),
  46         NumRegionCounters(0), FunctionHash(0), CurrentRegionCount(0) {}
  47
  48   /// Whether or not we have PGO region data for the current function. This is
  49   /// false both when we have no data at all and when our data has been
  50   /// discarded.
  51   bool haveRegionCounts() const { return !RegionCounts.empty(); }
  52
  53   /// Return the counter value of the current region.
  54   uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
  55
  56   /// Set the counter value for the current region. This is used to keep track
  57   /// of changes to the most recent counter from control flow and non-local
  58   /// exits.
  59   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
  60
  61   /// Check if an execution count is known for a given statement. If so, return
  62   /// true and put the value in Count; else return false.
  63   std::optional<uint64_t> getStmtCount(const Stmt *S) const {
  64     if (!StmtCountMap)
  65       return std::nullopt;
  66     auto I = StmtCountMap->find(S);
  67     if (I == StmtCountMap->end())
  68       return std::nullopt;
  69     return I->second;
  70   }
  71
  72   /// If the execution count for the current statement is known, record that
  73   /// as the current count.
  74   void setCurrentStmt(const Stmt *S) {
  75     if (auto Count = getStmtCount(S))
  76       setCurrentRegionCount(*Count);
  77   }
  78
  79   /// Assign counters to regions and configure them for PGO of a given
  80   /// function. Does nothing if instrumentation is not enabled and either
  81   /// generates global variables or associates PGO data with each of the
  82   /// counters depending on whether we are generating or using instrumentation.
  83   void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
  84   /// Emit a coverage mapping range with a counter zero
  85   /// for an unused declaration.
  86   void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
  87                                llvm::GlobalValue::LinkageTypes Linkage);
  88   // Insert instrumentation or attach profile metadata at value sites
  89   void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
  90                     llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
  91
  92   // Set a module flag indicating if value profiling is enabled.
  93   void setValueProfilingFlag(llvm::Module &M);
  94
  95 private:
  96   void setFuncName(llvm::Function *Fn);
  97   void setFuncName(StringRef Name, llvm::GlobalValue::LinkageTypes Linkage);
  98   void mapRegionCounters(const Decl *D);
  99   void computeRegionCounts(const Decl *D);
 100   void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
 101                                llvm::Function *Fn);
 102   void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
 103                         bool IsInMainFile);
 104   bool skipRegionMappingForDecl(const Decl *D);
 105   void emitCounterRegionMapping(const Decl *D);
 106
 107 public:
 108   void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S,
 109                             llvm::Value *StepV);
 110
 111   /// Return the region count for the counter at the given index.
 112   uint64_t getRegionCount(const Stmt *S) {
 113     if (!RegionCounterMap)
 114       return 0;
 115     if (!haveRegionCounts())
 116       return 0;
 117     // With profiles from a differing version of clang we can have mismatched
 118     // decl counts. Don't crash in such a case.
 119     auto Index = (*RegionCounterMap)[S];
 120     if (Index >= RegionCounts.size())
 121       return 0;
 122     return RegionCounts[Index];
 123   }
 124 };
 125
 126 }  // end namespace CodeGen
 127 }  // end namespace clang
 128
 129 #endif