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      1 //===--- CodeGenPGO.h - PGO Instrumentation for LLVM CodeGen ----*- C++ -*-===//
      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 // Instrumentation-based profile-guided optimization
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
     15 #define LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
     16 
     17 #include "CGBuilder.h"
     18 #include "CodeGenModule.h"
     19 #include "CodeGenTypes.h"
     20 #include "clang/Frontend/CodeGenOptions.h"
     21 #include "llvm/ADT/StringMap.h"
     22 #include "llvm/ProfileData/InstrProfReader.h"
     23 #include "llvm/Support/MemoryBuffer.h"
     24 #include <array>
     25 #include <memory>
     26 
     27 namespace clang {
     28 namespace CodeGen {
     29 
     30 /// Per-function PGO state.
     31 class CodeGenPGO {
     32 private:
     33   CodeGenModule &CGM;
     34   std::string FuncName;
     35   llvm::GlobalVariable *FuncNameVar;
     36 
     37   std::array <unsigned, llvm::IPVK_Last + 1> NumValueSites;
     38   unsigned NumRegionCounters;
     39   uint64_t FunctionHash;
     40   std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
     41   std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
     42   std::unique_ptr<llvm::InstrProfRecord> ProfRecord;
     43   std::vector<uint64_t> RegionCounts;
     44   uint64_t CurrentRegionCount;
     45   /// \brief A flag that is set to true when this function doesn't need
     46   /// to have coverage mapping data.
     47   bool SkipCoverageMapping;
     48 
     49 public:
     50   CodeGenPGO(CodeGenModule &CGM)
     51       : CGM(CGM), NumValueSites({{0}}), NumRegionCounters(0),
     52         FunctionHash(0), CurrentRegionCount(0), SkipCoverageMapping(false) {}
     53 
     54   /// Whether or not we have PGO region data for the current function. This is
     55   /// false both when we have no data at all and when our data has been
     56   /// discarded.
     57   bool haveRegionCounts() const { return !RegionCounts.empty(); }
     58 
     59   /// Return the counter value of the current region.
     60   uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
     61 
     62   /// Set the counter value for the current region. This is used to keep track
     63   /// of changes to the most recent counter from control flow and non-local
     64   /// exits.
     65   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
     66 
     67   /// Check if an execution count is known for a given statement. If so, return
     68   /// true and put the value in Count; else return false.
     69   Optional<uint64_t> getStmtCount(const Stmt *S) {
     70     if (!StmtCountMap)
     71       return None;
     72     auto I = StmtCountMap->find(S);
     73     if (I == StmtCountMap->end())
     74       return None;
     75     return I->second;
     76   }
     77 
     78   /// If the execution count for the current statement is known, record that
     79   /// as the current count.
     80   void setCurrentStmt(const Stmt *S) {
     81     if (auto Count = getStmtCount(S))
     82       setCurrentRegionCount(*Count);
     83   }
     84 
     85   /// Assign counters to regions and configure them for PGO of a given
     86   /// function. Does nothing if instrumentation is not enabled and either
     87   /// generates global variables or associates PGO data with each of the
     88   /// counters depending on whether we are generating or using instrumentation.
     89   void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
     90   /// Emit a coverage mapping range with a counter zero
     91   /// for an unused declaration.
     92   void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
     93                                llvm::GlobalValue::LinkageTypes Linkage);
     94   // Insert instrumentation or attach profile metadata at value sites
     95   void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
     96                     llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
     97 private:
     98   void setFuncName(llvm::Function *Fn);
     99   void setFuncName(StringRef Name, llvm::GlobalValue::LinkageTypes Linkage);
    100   void mapRegionCounters(const Decl *D);
    101   void computeRegionCounts(const Decl *D);
    102   void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
    103                                llvm::Function *Fn);
    104   void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
    105                         bool IsInMainFile);
    106   bool skipRegionMappingForDecl(const Decl *D);
    107   void emitCounterRegionMapping(const Decl *D);
    108 
    109 public:
    110   void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S);
    111 
    112   /// Return the region count for the counter at the given index.
    113   uint64_t getRegionCount(const Stmt *S) {
    114     if (!RegionCounterMap)
    115       return 0;
    116     if (!haveRegionCounts())
    117       return 0;
    118     return RegionCounts[(*RegionCounterMap)[S]];
    119   }
    120 };
    121 
    122 }  // end namespace CodeGen
    123 }  // end namespace clang
    124 
    125 #endif
    126