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 
44 public:
45   CodeGenPGO(CodeGenModule &CGM)
46       : CGM(CGM), NumValueSites({{0}}), NumRegionCounters(0), FunctionHash(0),
47         CurrentRegionCount(0) {}
48 
49   /// Whether or not we have PGO region data for the current function. This is
50   /// false both when we have no data at all and when our data has been
51   /// discarded.
52   bool haveRegionCounts() const { return !RegionCounts.empty(); }
53 
54   /// Return the counter value of the current region.
55   uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
56 
57   /// Set the counter value for the current region. This is used to keep track
58   /// of changes to the most recent counter from control flow and non-local
59   /// exits.
60   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
61 
62   /// Check if an execution count is known for a given statement. If so, return
63   /// true and put the value in Count; else return false.
64   Optional<uint64_t> getStmtCount(const Stmt *S) {
65     if (!StmtCountMap)
66       return None;
67     auto I = StmtCountMap->find(S);
68     if (I == StmtCountMap->end())
69       return None;
70     return I->second;
71   }
72 
73   /// If the execution count for the current statement is known, record that
74   /// as the current count.
75   void setCurrentStmt(const Stmt *S) {
76     if (auto Count = getStmtCount(S))
77       setCurrentRegionCount(*Count);
78   }
79 
80   /// Assign counters to regions and configure them for PGO of a given
81   /// function. Does nothing if instrumentation is not enabled and either
82   /// generates global variables or associates PGO data with each of the
83   /// counters depending on whether we are generating or using instrumentation.
84   void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
85   /// Emit a coverage mapping range with a counter zero
86   /// for an unused declaration.
87   void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
88                                llvm::GlobalValue::LinkageTypes Linkage);
89   // Insert instrumentation or attach profile metadata at value sites
90   void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
91                     llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
92 private:
93   void setFuncName(llvm::Function *Fn);
94   void setFuncName(StringRef Name, llvm::GlobalValue::LinkageTypes Linkage);
95   void mapRegionCounters(const Decl *D);
96   void computeRegionCounts(const Decl *D);
97   void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
98                                llvm::Function *Fn);
99   void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
100                         bool IsInMainFile);
101   bool skipRegionMappingForDecl(const Decl *D);
102   void emitCounterRegionMapping(const Decl *D);
103 
104 public:
105   void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S,
106                             llvm::Value *StepV);
107 
108   /// Return the region count for the counter at the given index.
109   uint64_t getRegionCount(const Stmt *S) {
110     if (!RegionCounterMap)
111       return 0;
112     if (!haveRegionCounts())
113       return 0;
114     return RegionCounts[(*RegionCounterMap)[S]];
115   }
116 };
117 
118 }  // end namespace CodeGen
119 }  // end namespace clang
120 
121 #endif
122