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
24namespace clang {
25namespace CodeGen {
26
27/// Per-function PGO state.
28class CodeGenPGO {
29private:
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
43public:
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
95private:
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
107public:
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