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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:
CodeGenPGO(CodeGenModule & CGM)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.
haveRegionCounts()57   bool haveRegionCounts() const { return !RegionCounts.empty(); }
58 
59   /// Return the counter value of the current region.
getCurrentRegionCount()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.
setCurrentRegionCount(uint64_t Count)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.
getStmtCount(const Stmt * S)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.
setCurrentStmt(const Stmt * S)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.
getRegionCount(const Stmt * S)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