CodeGenPGO.h revision 360784 
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
23namespace clang {
24namespace CodeGen {
25
26/// Per-function PGO state.
27class CodeGenPGO {
28private:
29  CodeGenModule &CGM;
30  std::string FuncName;
31  llvm::GlobalVariable *FuncNameVar;
32
33  std::array <unsigned, llvm::IPVK_Last + 1> NumValueSites;
34  unsigned NumRegionCounters;
35  uint64_t FunctionHash;
36  std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
37  std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
38  std::unique_ptr<llvm::InstrProfRecord> ProfRecord;
39  std::vector<uint64_t> RegionCounts;
40  uint64_t CurrentRegionCount;
41
42public:
43  CodeGenPGO(CodeGenModule &CGM)
44      : CGM(CGM), FuncNameVar(nullptr), NumValueSites({{0}}),
45        NumRegionCounters(0), FunctionHash(0), CurrentRegionCount(0) {}
46
47  /// Whether or not we have PGO region data for the current function. This is
48  /// false both when we have no data at all and when our data has been
49  /// discarded.
50  bool haveRegionCounts() const { return !RegionCounts.empty(); }
51
52  /// Return the counter value of the current region.
53  uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
54
55  /// Set the counter value for the current region. This is used to keep track
56  /// of changes to the most recent counter from control flow and non-local
57  /// exits.
58  void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
59
60  /// Check if an execution count is known for a given statement. If so, return
61  /// true and put the value in Count; else return false.
62  Optional<uint64_t> getStmtCount(const Stmt *S) {
63    if (!StmtCountMap)
64      return None;
65    auto I = StmtCountMap->find(S);
66    if (I == StmtCountMap->end())
67      return None;
68    return I->second;
69  }
70
71  /// If the execution count for the current statement is known, record that
72  /// as the current count.
73  void setCurrentStmt(const Stmt *S) {
74    if (auto Count = getStmtCount(S))
75      setCurrentRegionCount(*Count);
76  }
77
78  /// Assign counters to regions and configure them for PGO of a given
79  /// function. Does nothing if instrumentation is not enabled and either
80  /// generates global variables or associates PGO data with each of the
81  /// counters depending on whether we are generating or using instrumentation.
82  void assignRegionCounters(GlobalDecl GD, llvm::Function *Fn);
83  /// Emit a coverage mapping range with a counter zero
84  /// for an unused declaration.
85  void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
86                               llvm::GlobalValue::LinkageTypes Linkage);
87  // Insert instrumentation or attach profile metadata at value sites
88  void valueProfile(CGBuilderTy &Builder, uint32_t ValueKind,
89                    llvm::Instruction *ValueSite, llvm::Value *ValuePtr);
90private:
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  bool skipRegionMappingForDecl(const Decl *D);
100  void emitCounterRegionMapping(const Decl *D);
101
102public:
103  void emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S,
104                            llvm::Value *StepV);
105
106  /// Return the region count for the counter at the given index.
107  uint64_t getRegionCount(const Stmt *S) {
108    if (!RegionCounterMap)
109      return 0;
110    if (!haveRegionCounts())
111      return 0;
112    return RegionCounts[(*RegionCounterMap)[S]];
113  }
114};
115
116}  // end namespace CodeGen
117}  // end namespace clang
118
119#endif
120