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