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 
23 namespace clang {
24 namespace CodeGen {
25 
26 /// Per-function PGO state.
27 class CodeGenPGO {
28 private:
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 
42 public:
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);
90 private:
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 
102 public:
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