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.
35 llvm::GlobalVariable *FuncNameVar;
37 unsigned NumRegionCounters;
38 uint64_t FunctionHash;
39 std::unique_ptr<llvm::DenseMap<const Stmt *, unsigned>> RegionCounterMap;
40 std::unique_ptr<llvm::DenseMap<const Stmt *, uint64_t>> StmtCountMap;
41 std::vector<uint64_t> RegionCounts;
42 uint64_t CurrentRegionCount;
43 /// \brief A flag that is set to true when this function doesn't need
44 /// to have coverage mapping data.
45 bool SkipCoverageMapping;
48 CodeGenPGO(CodeGenModule &CGM)
49 : CGM(CGM), NumRegionCounters(0), FunctionHash(0), CurrentRegionCount(0),
50 SkipCoverageMapping(false) {}
52 /// Whether or not we have PGO region data for the current function. This is
53 /// false both when we have no data at all and when our data has been
55 bool haveRegionCounts() const { return !RegionCounts.empty(); }
57 /// Return the counter value of the current region.
58 uint64_t getCurrentRegionCount() const { return CurrentRegionCount; }
60 /// Set the counter value for the current region. This is used to keep track
61 /// of changes to the most recent counter from control flow and non-local
63 void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
65 /// Indicate that the current region is never reached, and thus should have a
66 /// counter value of zero. This is important so that subsequent regions can
67 /// correctly track their parent counts.
68 void setCurrentRegionUnreachable() { setCurrentRegionCount(0); }
70 /// Check if an execution count is known for a given statement. If so, return
71 /// true and put the value in Count; else return false.
72 bool getStmtCount(const Stmt *S, uint64_t &Count) {
75 llvm::DenseMap<const Stmt*, uint64_t>::const_iterator
76 I = StmtCountMap->find(S);
77 if (I == StmtCountMap->end())
83 /// If the execution count for the current statement is known, record that
84 /// as the current count.
85 void setCurrentStmt(const Stmt *S) {
87 if (getStmtCount(S, Count))
88 setCurrentRegionCount(Count);
91 /// Calculate branch weights appropriate for PGO data
92 llvm::MDNode *createBranchWeights(uint64_t TrueCount, uint64_t FalseCount);
93 llvm::MDNode *createBranchWeights(ArrayRef<uint64_t> Weights);
94 llvm::MDNode *createLoopWeights(const Stmt *Cond, RegionCounter &Cnt);
96 /// Check if we need to emit coverage mapping for a given declaration
97 void checkGlobalDecl(GlobalDecl GD);
98 /// Assign counters to regions and configure them for PGO of a given
99 /// function. Does nothing if instrumentation is not enabled and either
100 /// generates global variables or associates PGO data with each of the
101 /// counters depending on whether we are generating or using instrumentation.
102 void assignRegionCounters(const Decl *D, llvm::Function *Fn);
103 /// Emit a coverage mapping range with a counter zero
104 /// for an unused declaration.
105 void emitEmptyCounterMapping(const Decl *D, StringRef FuncName,
106 llvm::GlobalValue::LinkageTypes Linkage);
108 void setFuncName(llvm::Function *Fn);
109 void setFuncName(StringRef Name, llvm::GlobalValue::LinkageTypes Linkage);
110 void createFuncNameVar(llvm::GlobalValue::LinkageTypes Linkage);
111 void mapRegionCounters(const Decl *D);
112 void computeRegionCounts(const Decl *D);
113 void applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
115 void loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
117 void emitCounterVariables();
118 void emitCounterRegionMapping(const Decl *D);
120 /// Emit code to increment the counter at the given index
121 void emitCounterIncrement(CGBuilderTy &Builder, unsigned Counter);
123 /// Return the region counter for the given statement. This should only be
124 /// called on statements that have a dedicated counter.
125 unsigned getRegionCounter(const Stmt *S) {
126 if (!RegionCounterMap)
128 return (*RegionCounterMap)[S];
131 /// Return the region count for the counter at the given index.
132 uint64_t getRegionCount(unsigned Counter) {
133 if (!haveRegionCounts())
135 return RegionCounts[Counter];
138 friend class RegionCounter;
141 /// A counter for a particular region. This is the primary interface through
142 /// which clients manage PGO counters and their values.
143 class RegionCounter {
147 uint64_t ParentCount;
148 uint64_t RegionCount;
151 RegionCounter(CodeGenPGO &PGO, unsigned CounterIndex)
152 : PGO(&PGO), Counter(CounterIndex), Count(PGO.getRegionCount(Counter)),
153 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
156 RegionCounter(CodeGenPGO &PGO, const Stmt *S)
157 : PGO(&PGO), Counter(PGO.getRegionCounter(S)),
158 Count(PGO.getRegionCount(Counter)),
159 ParentCount(PGO.getCurrentRegionCount()), Adjust(0) {}
161 /// Get the value of the counter. In most cases this is the number of times
162 /// the region of the counter was entered, but for switch labels it's the
163 /// number of direct jumps to that label.
164 uint64_t getCount() const { return Count; }
166 /// Get the value of the counter with adjustments applied. Adjustments occur
167 /// when control enters or leaves the region abnormally; i.e., if there is a
168 /// jump to a label within the region, or if the function can return from
169 /// within the region. The adjusted count, then, is the value of the counter
170 /// at the end of the region.
171 uint64_t getAdjustedCount() const {
172 return Count + Adjust;
175 /// Get the value of the counter in this region's parent, i.e., the region
176 /// that was active when this region began. This is useful for deriving
177 /// counts in implicitly counted regions, like the false case of a condition
178 /// or the normal exits of a loop.
179 uint64_t getParentCount() const { return ParentCount; }
181 /// Activate the counter by emitting an increment and starting to track
182 /// adjustments. If AddIncomingFallThrough is true, the current region count
183 /// will be added to the counter for the purposes of tracking the region.
184 void beginRegion(CGBuilderTy &Builder, bool AddIncomingFallThrough=false) {
185 beginRegion(AddIncomingFallThrough);
186 PGO->emitCounterIncrement(Builder, Counter);
188 void beginRegion(bool AddIncomingFallThrough=false) {
190 if (AddIncomingFallThrough)
191 RegionCount += PGO->getCurrentRegionCount();
192 PGO->setCurrentRegionCount(RegionCount);
195 /// For counters on boolean branches, begins tracking adjustments for the
197 void beginElseRegion() {
198 RegionCount = ParentCount - Count;
199 PGO->setCurrentRegionCount(RegionCount);
202 /// Reset the current region count.
203 void setCurrentRegionCount(uint64_t CurrentCount) {
204 RegionCount = CurrentCount;
205 PGO->setCurrentRegionCount(RegionCount);
208 /// Adjust for non-local control flow after emitting a subexpression or
209 /// substatement. This must be called to account for constructs such as gotos,
210 /// labels, and returns, so that we can ensure that our region's count is
211 /// correct in the code that follows.
212 void adjustForControlFlow() {
213 Adjust += PGO->getCurrentRegionCount() - RegionCount;
214 // Reset the region count in case this is called again later.
215 RegionCount = PGO->getCurrentRegionCount();
218 /// Commit all adjustments to the current region. If the region is a loop,
219 /// the LoopAdjust value should be the count of all the breaks and continues
220 /// from the loop, to compensate for those counts being deducted from the
221 /// adjustments for the body of the loop.
222 void applyAdjustmentsToRegion(uint64_t LoopAdjust) {
223 PGO->setCurrentRegionCount(ParentCount + Adjust + LoopAdjust);
227 } // end namespace CodeGen
228 } // end namespace clang