1 //===--- CodeGenPGO.h - PGO Instrumentation for LLVM CodeGen ----*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Instrumentation-based profile-guided optimization
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
14 #define LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
15 
16 #include "CGBuilder.h"
17 #include "CodeGenModule.h"
18 #include "CodeGenTypes.h"
19 #include "llvm/ProfileData/InstrProfReader.h"
20 #include <array>
21 #include <memory>
22 #include <optional>
23 
24 namespace clang {
25 namespace CodeGen {
26 
27 /// Per-function PGO state.
28 class CodeGenPGO {
29 private:
30   CodeGenModule &CGM;
31   std::string FuncName;
32   llvm::GlobalVariable *FuncNameVar;
33 
34   std::array <unsigned, llvm::IPVK_Last + 1> NumValueSites;
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::unique_ptr<llvm::InstrProfRecord> ProfRecord;
40   std::vector<uint64_t> RegionCounts;
41   uint64_t CurrentRegionCount;
42 
43 public:
44   CodeGenPGO(CodeGenModule &CGModule)
45       : CGM(CGModule), FuncNameVar(nullptr), NumValueSites({{0}}),
46         NumRegionCounters(0), FunctionHash(0), CurrentRegionCount(0) {}
47 
48   /// Whether or not we have PGO region data for the current function. This is
49   /// false both when we have no data at all and when our data has been
50   /// discarded.
51   bool haveRegionCounts() const { return !RegionCounts.empty(); }
52 
53   /// Return the counter value of the current region.
54   uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
55 
56   /// Set the counter value for the current region. This is used to keep track
57   /// of changes to the most recent counter from control flow and non-local
58   /// exits.
59   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
60 
61   /// Check if an execution count is known for a given statement. If so, return
62   /// true and put the value in Count; else return false.
63   std::optional<uint64_t> getStmtCount(const Stmt *S) const {
64     if (!StmtCountMap)
65       return std::nullopt;
66     auto I = StmtCountMap->find(S);
67     if (I == StmtCountMap->end())
68       return std::nullopt;
69     return I->second;
70   }
71 
72   /// If the execution count for the current statement is known, record that
73   /// as the current count.
74   void setCurrentStmt(const Stmt *S) {
75     if (auto Count = getStmtCount(S))
76       setCurrentRegionCount(*Count);
77   }
78 
79   /// Assign counters to regions and configure them for PGO of a given
80   /// function. Does nothing if instrumentation is not enabled and either
81   /// generates global variables or associates PGO data with each of the
82   /// counters depending on whether we are generating or using instrumentation.
83   void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
84   /// Emit a coverage mapping range with a counter zero
85   /// for an unused declaration.
86   void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
87                                llvm::GlobalValue::LinkageTypes Linkage);
88   // Insert instrumentation or attach profile metadata at value sites
89   void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
90                     llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
91 
92   // Set a module flag indicating if value profiling is enabled.
93   void setValueProfilingFlag(llvm::Module &M);
94 
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                             llvm::Value *StepV);
110 
111   /// Return the region count for the counter at the given index.
112   uint64_t getRegionCount(const Stmt *S) {
113     if (!RegionCounterMap)
114       return 0;
115     if (!haveRegionCounts())
116       return 0;
117     // With profiles from a differing version of clang we can have mismatched
118     // decl counts. Don't crash in such a case.
119     auto Index = (*RegionCounterMap)[S];
120     if (Index >= RegionCounts.size())
121       return 0;
122     return RegionCounts[Index];
123   }
124 };
125 
126 }  // end namespace CodeGen
127 }  // end namespace clang
128 
129 #endif
130