1 //===--- CodeGenPGO.h - PGO Instrumentation for LLVM CodeGen ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Instrumentation-based profile-guided optimization
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
15 #define LLVM_CLANG_LIB_CODEGEN_CODEGENPGO_H
17 #include "CGBuilder.h"
18 #include "CodeGenModule.h"
19 #include "CodeGenTypes.h"
20 #include "clang/Frontend/CodeGenOptions.h"
21 #include "llvm/ADT/StringMap.h"
22 #include "llvm/Support/MemoryBuffer.h"
29 /// Per-function PGO state. This class should generally not be used directly,
30 /// but instead through the CodeGenFunction and RegionCounter types.
34 std::unique_ptr<std::string> PrefixedFuncName;
35 StringRef RawFuncName;
36 llvm::GlobalValue::LinkageTypes VarLinkage;
38 unsigned NumRegionCounters;
39 uint64_t FunctionHash;
40 llvm::GlobalVariable *RegionCounters;
41 std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
42 std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
43 std::unique_ptr<std::vector<uint64_t>> RegionCounts;
44 uint64_t CurrentRegionCount;
45 std::string CoverageMapping;
46 /// \brief A flag that is set to true when this function doesn't need
47 /// to have coverage mapping data.
48 bool SkipCoverageMapping;
51 CodeGenPGO(CodeGenModule &CGM)
52 : CGM(CGM), NumRegionCounters(0), FunctionHash(0),
53 RegionCounters(nullptr), CurrentRegionCount(0),
54 SkipCoverageMapping(false) {}
56 /// Whether or not we have PGO region data for the current function. This is
57 /// false both when we have no data at all and when our data has been
59 bool haveRegionCounts() const { return RegionCounts != nullptr; }
61 /// Get the string used to identify this function in the profile data.
62 /// For functions with local linkage, this includes the main file name.
63 StringRef getFuncName() const { return StringRef(*PrefixedFuncName); }
64 std::string getFuncVarName(StringRef VarName) const {
65 return ("__llvm_profile_" + VarName + "_" + RawFuncName).str();
68 /// Return the counter value of the current region.
69 uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
71 /// Set the counter value for the current region. This is used to keep track
72 /// of changes to the most recent counter from control flow and non-local
74 void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
76 /// Indicate that the current region is never reached, and thus should have a
77 /// counter value of zero. This is important so that subsequent regions can
78 /// correctly track their parent counts.
79 void setCurrentRegionUnreachable() { setCurrentRegionCount(0); }
81 /// Check if an execution count is known for a given statement. If so, return
82 /// true and put the value in Count; else return false.
83 bool getStmtCount(const Stmt *S, uint64_t &Count) {
86 llvm::DenseMap<const Stmt*, uint64_t>::const_iterator
87 I = StmtCountMap->find(S);
88 if (I == StmtCountMap->end())
94 /// If the execution count for the current statement is known, record that
95 /// as the current count.
96 void setCurrentStmt(const Stmt *S) {
98 if (getStmtCount(S, Count))
99 setCurrentRegionCount(Count);
102 /// Calculate branch weights appropriate for PGO data
103 llvm::MDNode *createBranchWeights(uint64_t TrueCount, uint64_t FalseCount);
104 llvm::MDNode *createBranchWeights(ArrayRef<uint64_t> Weights);
105 llvm::MDNode *createLoopWeights(const Stmt *Cond, RegionCounter &Cnt);
107 /// Check if we need to emit coverage mapping for a given declaration
108 void checkGlobalDecl(GlobalDecl GD);
109 /// Assign counters to regions and configure them for PGO of a given
110 /// function. Does nothing if instrumentation is not enabled and either
111 /// generates global variables or associates PGO data with each of the
112 /// counters depending on whether we are generating or using instrumentation.
113 void assignRegionCounters(const Decl *D, llvm::Function *Fn);
114 /// Emit static data structures for instrumentation data.
115 void emitInstrumentationData();
116 /// Clean up region counter state. Must be called if assignRegionCounters is
118 void destroyRegionCounters();
119 /// Emit static initialization code, if any.
120 static llvm::Function *emitInitialization(CodeGenModule &CGM);
121 /// Emit a coverage mapping range with a counter zero
122 /// for an unused declaration.
123 void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
124 llvm::GlobalValue::LinkageTypes Linkage);
126 void setFuncName(llvm::Function *Fn);
127 void setFuncName(StringRef Name, llvm::GlobalValue::LinkageTypes Linkage);
128 void setVarLinkage(llvm::GlobalValue::LinkageTypes Linkage);
129 void mapRegionCounters(const Decl *D);
130 void computeRegionCounts(const Decl *D);
131 void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
133 void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
135 void emitCounterVariables();
136 llvm::GlobalVariable *buildDataVar();
137 void emitCounterRegionMapping(const Decl *D);
139 /// Emit code to increment the counter at the given index
140 void emitCounterIncrement(CGBuilderTy &Builder, unsigned Counter);
142 /// Return the region counter for the given statement. This should only be
143 /// called on statements that have a dedicated counter.
144 unsigned getRegionCounter(const Stmt *S) {
145 if (!RegionCounterMap)
147 return (*RegionCounterMap)[S];
150 /// Return the region count for the counter at the given index.
151 uint64_t getRegionCount(unsigned Counter) {
152 if (!haveRegionCounts())
154 return (*RegionCounts)[Counter];
157 friend class RegionCounter;
160 /// A counter for a particular region. This is the primary interface through
161 /// which clients manage PGO counters and their values.
162 class RegionCounter {
166 uint64_t ParentCount;
167 uint64_t RegionCount;
170 RegionCounter(CodeGenPGO &PGO, unsigned CounterIndex)
171 : PGO(&PGO), Counter(CounterIndex), Count(PGO.getRegionCount(Counter)),
172 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
175 RegionCounter(CodeGenPGO &PGO, const Stmt *S)
176 : PGO(&PGO), Counter(PGO.getRegionCounter(S)),
177 Count(PGO.getRegionCount(Counter)),
178 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
180 /// Get the value of the counter. In most cases this is the number of times
181 /// the region of the counter was entered, but for switch labels it's the
182 /// number of direct jumps to that label.
183 uint64_t getCount() const { return Count; }
185 /// Get the value of the counter with adjustments applied. Adjustments occur
186 /// when control enters or leaves the region abnormally; i.e., if there is a
187 /// jump to a label within the region, or if the function can return from
188 /// within the region. The adjusted count, then, is the value of the counter
189 /// at the end of the region.
190 uint64_t getAdjustedCount() const {
191 return Count + Adjust;
194 /// Get the value of the counter in this region's parent, i.e., the region
195 /// that was active when this region began. This is useful for deriving
196 /// counts in implicitly counted regions, like the false case of a condition
197 /// or the normal exits of a loop.
198 uint64_t getParentCount() const { return ParentCount; }
200 /// Activate the counter by emitting an increment and starting to track
201 /// adjustments. If AddIncomingFallThrough is true, the current region count
202 /// will be added to the counter for the purposes of tracking the region.
203 void beginRegion(CGBuilderTy &Builder, bool AddIncomingFallThrough=false) {
204 beginRegion(AddIncomingFallThrough);
205 PGO->emitCounterIncrement(Builder, Counter);
207 void beginRegion(bool AddIncomingFallThrough=false) {
209 if (AddIncomingFallThrough)
210 RegionCount += PGO->getCurrentRegionCount();
211 PGO->setCurrentRegionCount(RegionCount);
214 /// For counters on boolean branches, begins tracking adjustments for the
216 void beginElseRegion() {
217 RegionCount = ParentCount - Count;
218 PGO->setCurrentRegionCount(RegionCount);
221 /// Reset the current region count.
222 void setCurrentRegionCount(uint64_t CurrentCount) {
223 RegionCount = CurrentCount;
224 PGO->setCurrentRegionCount(RegionCount);
227 /// Adjust for non-local control flow after emitting a subexpression or
228 /// substatement. This must be called to account for constructs such as gotos,
229 /// labels, and returns, so that we can ensure that our region's count is
230 /// correct in the code that follows.
231 void adjustForControlFlow() {
232 Adjust += PGO->getCurrentRegionCount() - RegionCount;
233 // Reset the region count in case this is called again later.
234 RegionCount = PGO->getCurrentRegionCount();
237 /// Commit all adjustments to the current region. If the region is a loop,
238 /// the LoopAdjust value should be the count of all the breaks and continues
239 /// from the loop, to compensate for those counts being deducted from the
240 /// adjustments for the body of the loop.
241 void applyAdjustmentsToRegion(uint64_t LoopAdjust) {
242 PGO->setCurrentRegionCount(ParentCount + Adjust + LoopAdjust);
246 } // end namespace CodeGen
247 } // end namespace clang