1 //===- Transforms/IPO/SampleProfileProbe.h ----------*- 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 /// \file 10 /// This file provides the interface for the pseudo probe implementation for 11 /// AutoFDO. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H 16 #define LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H 17 18 #include "llvm/Analysis/LazyCallGraph.h" 19 #include "llvm/IR/PassManager.h" 20 #include "llvm/ProfileData/SampleProf.h" 21 #include <unordered_map> 22 23 namespace llvm { 24 class BasicBlock; 25 class Function; 26 class Instruction; 27 class Loop; 28 class PassInstrumentationCallbacks; 29 class TargetMachine; 30 31 class Module; 32 33 using namespace sampleprof; 34 using BlockIdMap = std::unordered_map<BasicBlock *, uint32_t>; 35 using InstructionIdMap = std::unordered_map<Instruction *, uint32_t>; 36 // Map from tuples of Probe id and inline stack hash code to distribution 37 // factors. 38 using ProbeFactorMap = std::unordered_map<std::pair<uint64_t, uint64_t>, float, 39 pair_hash<uint64_t, uint64_t>>; 40 using FuncProbeFactorMap = StringMap<ProbeFactorMap>; 41 42 43 // A pseudo probe verifier that can be run after each IR passes to detect the 44 // violation of updating probe factors. In principle, the sum of distribution 45 // factor for a probe should be identical before and after a pass. For a 46 // function pass, the factor sum for a probe would be typically 100%. 47 class PseudoProbeVerifier { 48 public: 49 void registerCallbacks(PassInstrumentationCallbacks &PIC); 50 51 // Implementation of pass instrumentation callbacks for new pass manager. 52 void runAfterPass(StringRef PassID, Any IR); 53 54 private: 55 // Allow a little bias due the rounding to integral factors. 56 constexpr static float DistributionFactorVariance = 0.02f; 57 // Distribution factors from last pass. 58 FuncProbeFactorMap FunctionProbeFactors; 59 60 void collectProbeFactors(const BasicBlock *BB, ProbeFactorMap &ProbeFactors); 61 void runAfterPass(const Module *M); 62 void runAfterPass(const LazyCallGraph::SCC *C); 63 void runAfterPass(const Function *F); 64 void runAfterPass(const Loop *L); 65 bool shouldVerifyFunction(const Function *F); 66 void verifyProbeFactors(const Function *F, 67 const ProbeFactorMap &ProbeFactors); 68 }; 69 70 /// Sample profile pseudo prober. 71 /// 72 /// Insert pseudo probes for block sampling and value sampling. 73 class SampleProfileProber { 74 public: 75 // Give an empty module id when the prober is not used for instrumentation. 76 SampleProfileProber(Function &F, const std::string &CurModuleUniqueId); 77 void instrumentOneFunc(Function &F, TargetMachine *TM); 78 79 private: getFunction()80 Function *getFunction() const { return F; } getFunctionHash()81 uint64_t getFunctionHash() const { return FunctionHash; } 82 uint32_t getBlockId(const BasicBlock *BB) const; 83 uint32_t getCallsiteId(const Instruction *Call) const; 84 void findUnreachableBlocks(DenseSet<BasicBlock *> &BlocksToIgnore); 85 void findInvokeNormalDests(DenseSet<BasicBlock *> &InvokeNormalDests); 86 void computeBlocksToIgnore(DenseSet<BasicBlock *> &BlocksToIgnore, 87 DenseSet<BasicBlock *> &BlocksAndCallsToIgnore); 88 const Instruction * 89 getOriginalTerminator(const BasicBlock *Head, 90 const DenseSet<BasicBlock *> &BlocksToIgnore); 91 void computeCFGHash(const DenseSet<BasicBlock *> &BlocksToIgnore); 92 void computeProbeId(const DenseSet<BasicBlock *> &BlocksToIgnore, 93 const DenseSet<BasicBlock *> &BlocksAndCallsToIgnore); 94 95 Function *F; 96 97 /// The current module ID that is used to name a static object as a comdat 98 /// group. 99 std::string CurModuleUniqueId; 100 101 /// A CFG hash code used to identify a function code changes. 102 uint64_t FunctionHash; 103 104 /// Map basic blocks to the their pseudo probe ids. 105 BlockIdMap BlockProbeIds; 106 107 /// Map indirect calls to the their pseudo probe ids. 108 InstructionIdMap CallProbeIds; 109 110 /// The ID of the last probe, Can be used to number a new probe. 111 uint32_t LastProbeId; 112 }; 113 114 class SampleProfileProbePass : public PassInfoMixin<SampleProfileProbePass> { 115 TargetMachine *TM; 116 117 public: SampleProfileProbePass(TargetMachine * TM)118 SampleProfileProbePass(TargetMachine *TM) : TM(TM) {} 119 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 120 }; 121 122 // Pseudo probe distribution factor updater. 123 // Sample profile annotation can happen in both LTO prelink and postlink. The 124 // postlink-time re-annotation can degrade profile quality because of prelink 125 // code duplication transformation, such as loop unrolling, jump threading, 126 // indirect call promotion etc. As such, samples corresponding to a source 127 // location may be aggregated multiple times in postlink. With a concept of 128 // distribution factor for pseudo probes, samples can be distributed among 129 // duplicated probes reasonable based on the assumption that optimizations 130 // duplicating code well-maintain the branch frequency information (BFI). This 131 // pass updates distribution factors for each pseudo probe at the end of the 132 // prelink pipeline, to reflect an estimated portion of the real execution 133 // count. 134 class PseudoProbeUpdatePass : public PassInfoMixin<PseudoProbeUpdatePass> { 135 void runOnFunction(Function &F, FunctionAnalysisManager &FAM); 136 137 public: 138 PseudoProbeUpdatePass() = default; 139 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 140 }; 141 142 } // end namespace llvm 143 #endif // LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H 144