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/ProfileData/InstrProfReader.h"
22 #include <array>
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   std::array <unsigned, llvm::IPVK_Last + 1> NumValueSites;
36   unsigned NumRegionCounters;
37   uint64_t FunctionHash;
38   std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
39   std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
40   std::unique_ptr<llvm::InstrProfRecord> ProfRecord;
41   std::vector<uint64_t> RegionCounts;
42   uint64_t CurrentRegionCount;
43   /// \brief A flag that is set to true when this function doesn't need
44   /// to have coverage mapping data.
45   bool SkipCoverageMapping;
46 
47 public:
48   CodeGenPGO(CodeGenModule &CGM)
49       : CGM(CGM), NumValueSites({{0}}), NumRegionCounters(0),
50         FunctionHash(0), CurrentRegionCount(0), SkipCoverageMapping(false) {}
51 
52   /// Whether or not we have PGO region data for the current function. This is
53   /// false both when we have no data at all and when our data has been
54   /// discarded.
55   bool haveRegionCounts() const { return !RegionCounts.empty(); }
56 
57   /// Return the counter value of the current region.
58   uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
59 
60   /// Set the counter value for the current region. This is used to keep track
61   /// of changes to the most recent counter from control flow and non-local
62   /// exits.
63   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
64 
65   /// Check if an execution count is known for a given statement. If so, return
66   /// true and put the value in Count; else return false.
67   Optional<uint64_t> getStmtCount(const Stmt *S) {
68     if (!StmtCountMap)
69       return None;
70     auto I = StmtCountMap->find(S);
71     if (I == StmtCountMap->end())
72       return None;
73     return I->second;
74   }
75 
76   /// If the execution count for the current statement is known, record that
77   /// as the current count.
78   void setCurrentStmt(const Stmt *S) {
79     if (auto Count = getStmtCount(S))
80       setCurrentRegionCount(*Count);
81   }
82 
83   /// Assign counters to regions and configure them for PGO of a given
84   /// function. Does nothing if instrumentation is not enabled and either
85   /// generates global variables or associates PGO data with each of the
86   /// counters depending on whether we are generating or using instrumentation.
87   void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
88   /// Emit a coverage mapping range with a counter zero
89   /// for an unused declaration.
90   void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
91                                llvm::GlobalValue::LinkageTypes Linkage);
92   // Insert instrumentation or attach profile metadata at value sites
93   void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
94                     llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
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 
110   /// Return the region count for the counter at the given index.
111   uint64_t getRegionCount(const Stmt *S) {
112     if (!RegionCounterMap)
113       return 0;
114     if (!haveRegionCounts())
115       return 0;
116     return RegionCounts[(*RegionCounterMap)[S]];
117   }
118 };
119 
120 }  // end namespace CodeGen
121 }  // end namespace clang
122 
123 #endif
124