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 CLANG_CODEGEN_CODEGENPGO_H
15 #define CLANG_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;
47 CodeGenPGO(CodeGenModule &CGM)
48 : CGM(CGM), NumRegionCounters(0), FunctionHash(0),
49 RegionCounters(nullptr), CurrentRegionCount(0) {}
51 /// Whether or not we have PGO region data for the current function. This is
52 /// false both when we have no data at all and when our data has been
54 bool haveRegionCounts() const { return RegionCounts != nullptr; }
56 /// Get the string used to identify this function in the profile data.
57 /// For functions with local linkage, this includes the main file name.
58 StringRef getFuncName() const { return StringRef(*PrefixedFuncName); }
59 std::string getFuncVarName(StringRef VarName) const {
60 return ("__llvm_profile_" + VarName + "_" + RawFuncName).str();
63 /// Return the counter value of the current region.
64 uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
66 /// Set the counter value for the current region. This is used to keep track
67 /// of changes to the most recent counter from control flow and non-local
69 void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
71 /// Indicate that the current region is never reached, and thus should have a
72 /// counter value of zero. This is important so that subsequent regions can
73 /// correctly track their parent counts.
74 void setCurrentRegionUnreachable() { setCurrentRegionCount(0); }
76 /// Check if an execution count is known for a given statement. If so, return
77 /// true and put the value in Count; else return false.
78 bool getStmtCount(const Stmt *S, uint64_t &Count) {
81 llvm::DenseMap<const Stmt*, uint64_t>::const_iterator
82 I = StmtCountMap->find(S);
83 if (I == StmtCountMap->end())
89 /// If the execution count for the current statement is known, record that
90 /// as the current count.
91 void setCurrentStmt(const Stmt *S) {
93 if (getStmtCount(S, Count))
94 setCurrentRegionCount(Count);
97 /// Calculate branch weights appropriate for PGO data
98 llvm::MDNode *createBranchWeights(uint64_t TrueCount, uint64_t FalseCount);
99 llvm::MDNode *createBranchWeights(ArrayRef<uint64_t> Weights);
100 llvm::MDNode *createLoopWeights(const Stmt *Cond, RegionCounter &Cnt);
102 /// Assign counters to regions and configure them for PGO of a given
103 /// function. Does nothing if instrumentation is not enabled and either
104 /// generates global variables or associates PGO data with each of the
105 /// counters depending on whether we are generating or using instrumentation.
106 void assignRegionCounters(const Decl *D, llvm::Function *Fn);
107 /// Emit static data structures for instrumentation data.
108 void emitInstrumentationData();
109 /// Clean up region counter state. Must be called if assignRegionCounters is
111 void destroyRegionCounters();
112 /// Emit static initialization code, if any.
113 static llvm::Function *emitInitialization(CodeGenModule &CGM);
116 void setFuncName(llvm::Function *Fn);
117 void mapRegionCounters(const Decl *D);
118 void computeRegionCounts(const Decl *D);
119 void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
121 void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
123 void emitCounterVariables();
124 llvm::GlobalVariable *buildDataVar();
126 /// Emit code to increment the counter at the given index
127 void emitCounterIncrement(CGBuilderTy &Builder, unsigned Counter);
129 /// Return the region counter for the given statement. This should only be
130 /// called on statements that have a dedicated counter.
131 unsigned getRegionCounter(const Stmt *S) {
132 if (!RegionCounterMap)
134 return (*RegionCounterMap)[S];
137 /// Return the region count for the counter at the given index.
138 uint64_t getRegionCount(unsigned Counter) {
139 if (!haveRegionCounts())
141 return (*RegionCounts)[Counter];
144 friend class RegionCounter;
147 /// A counter for a particular region. This is the primary interface through
148 /// which clients manage PGO counters and their values.
149 class RegionCounter {
153 uint64_t ParentCount;
154 uint64_t RegionCount;
157 RegionCounter(CodeGenPGO &PGO, unsigned CounterIndex)
158 : PGO(&PGO), Counter(CounterIndex), Count(PGO.getRegionCount(Counter)),
159 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
162 RegionCounter(CodeGenPGO &PGO, const Stmt *S)
163 : PGO(&PGO), Counter(PGO.getRegionCounter(S)),
164 Count(PGO.getRegionCount(Counter)),
165 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
167 /// Get the value of the counter. In most cases this is the number of times
168 /// the region of the counter was entered, but for switch labels it's the
169 /// number of direct jumps to that label.
170 uint64_t getCount() const { return Count; }
172 /// Get the value of the counter with adjustments applied. Adjustments occur
173 /// when control enters or leaves the region abnormally; i.e., if there is a
174 /// jump to a label within the region, or if the function can return from
175 /// within the region. The adjusted count, then, is the value of the counter
176 /// at the end of the region.
177 uint64_t getAdjustedCount() const {
178 return Count + Adjust;
181 /// Get the value of the counter in this region's parent, i.e., the region
182 /// that was active when this region began. This is useful for deriving
183 /// counts in implicitly counted regions, like the false case of a condition
184 /// or the normal exits of a loop.
185 uint64_t getParentCount() const { return ParentCount; }
187 /// Activate the counter by emitting an increment and starting to track
188 /// adjustments. If AddIncomingFallThrough is true, the current region count
189 /// will be added to the counter for the purposes of tracking the region.
190 void beginRegion(CGBuilderTy &Builder, bool AddIncomingFallThrough=false) {
191 beginRegion(AddIncomingFallThrough);
192 PGO->emitCounterIncrement(Builder, Counter);
194 void beginRegion(bool AddIncomingFallThrough=false) {
196 if (AddIncomingFallThrough)
197 RegionCount += PGO->getCurrentRegionCount();
198 PGO->setCurrentRegionCount(RegionCount);
201 /// For counters on boolean branches, begins tracking adjustments for the
203 void beginElseRegion() {
204 RegionCount = ParentCount - Count;
205 PGO->setCurrentRegionCount(RegionCount);
208 /// Reset the current region count.
209 void setCurrentRegionCount(uint64_t CurrentCount) {
210 RegionCount = CurrentCount;
211 PGO->setCurrentRegionCount(RegionCount);
214 /// Adjust for non-local control flow after emitting a subexpression or
215 /// substatement. This must be called to account for constructs such as gotos,
216 /// labels, and returns, so that we can ensure that our region's count is
217 /// correct in the code that follows.
218 void adjustForControlFlow() {
219 Adjust += PGO->getCurrentRegionCount() - RegionCount;
220 // Reset the region count in case this is called again later.
221 RegionCount = PGO->getCurrentRegionCount();
224 /// Commit all adjustments to the current region. If the region is a loop,
225 /// the LoopAdjust value should be the count of all the breaks and continues
226 /// from the loop, to compensate for those counts being deducted from the
227 /// adjustments for the body of the loop.
228 void applyAdjustmentsToRegion(uint64_t LoopAdjust) {
229 PGO->setCurrentRegionCount(ParentCount + Adjust + LoopAdjust);
233 } // end namespace CodeGen
234 } // end namespace clang