1 //===- OptimizationRemarkEmitter.h - Optimization Diagnostic ----*- 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 // Optimization diagnostic interfaces. It's packaged as an analysis pass so 10 // that by using this service passes become dependent on BFI as well. BFI is 11 // used to compute the "hotness" of the diagnostic message. 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_IR_OPTIMIZATIONDIAGNOSTICINFO_H 15 #define LLVM_IR_OPTIMIZATIONDIAGNOSTICINFO_H 16 17 #include "llvm/ADT/Optional.h" 18 #include "llvm/Analysis/BlockFrequencyInfo.h" 19 #include "llvm/IR/DiagnosticInfo.h" 20 #include "llvm/IR/PassManager.h" 21 #include "llvm/Pass.h" 22 23 namespace llvm { 24 class Function; 25 class Value; 26 27 /// The optimization diagnostic interface. 28 /// 29 /// It allows reporting when optimizations are performed and when they are not 30 /// along with the reasons for it. Hotness information of the corresponding 31 /// code region can be included in the remark if DiagnosticsHotnessRequested is 32 /// enabled in the LLVM context. 33 class OptimizationRemarkEmitter { 34 public: OptimizationRemarkEmitter(const Function * F,BlockFrequencyInfo * BFI)35 OptimizationRemarkEmitter(const Function *F, BlockFrequencyInfo *BFI) 36 : F(F), BFI(BFI) {} 37 38 /// This variant can be used to generate ORE on demand (without the 39 /// analysis pass). 40 /// 41 /// Note that this ctor has a very different cost depending on whether 42 /// F->getContext().getDiagnosticsHotnessRequested() is on or not. If it's off 43 /// the operation is free. 44 /// 45 /// Whereas if DiagnosticsHotnessRequested is on, it is fairly expensive 46 /// operation since BFI and all its required analyses are computed. This is 47 /// for example useful for CGSCC passes that can't use function analyses 48 /// passes in the old PM. 49 OptimizationRemarkEmitter(const Function *F); 50 OptimizationRemarkEmitter(OptimizationRemarkEmitter && Arg)51 OptimizationRemarkEmitter(OptimizationRemarkEmitter &&Arg) 52 : F(Arg.F), BFI(Arg.BFI) {} 53 54 OptimizationRemarkEmitter &operator=(OptimizationRemarkEmitter &&RHS) { 55 F = RHS.F; 56 BFI = RHS.BFI; 57 return *this; 58 } 59 60 /// Handle invalidation events in the new pass manager. 61 bool invalidate(Function &F, const PreservedAnalyses &PA, 62 FunctionAnalysisManager::Invalidator &Inv); 63 64 /// Output the remark via the diagnostic handler and to the 65 /// optimization record file. 66 void emit(DiagnosticInfoOptimizationBase &OptDiag); 67 68 /// Take a lambda that returns a remark which will be emitted. Second 69 /// argument is only used to restrict this to functions. 70 template <typename T> 71 void emit(T RemarkBuilder, decltype(RemarkBuilder()) * = nullptr) { 72 // Avoid building the remark unless we know there are at least *some* 73 // remarks enabled. We can't currently check whether remarks are requested 74 // for the calling pass since that requires actually building the remark. 75 76 if (F->getContext().getLLVMRemarkStreamer() || 77 F->getContext().getDiagHandlerPtr()->isAnyRemarkEnabled()) { 78 auto R = RemarkBuilder(); 79 emit((DiagnosticInfoOptimizationBase &)R); 80 } 81 } 82 83 /// Whether we allow for extra compile-time budget to perform more 84 /// analysis to produce fewer false positives. 85 /// 86 /// This is useful when reporting missed optimizations. In this case we can 87 /// use the extra analysis (1) to filter trivial false positives or (2) to 88 /// provide more context so that non-trivial false positives can be quickly 89 /// detected by the user. allowExtraAnalysis(StringRef PassName)90 bool allowExtraAnalysis(StringRef PassName) const { 91 return (F->getContext().getLLVMRemarkStreamer() || 92 F->getContext().getDiagHandlerPtr()->isAnyRemarkEnabled(PassName)); 93 } 94 95 private: 96 const Function *F; 97 98 BlockFrequencyInfo *BFI; 99 100 /// If we generate BFI on demand, we need to free it when ORE is freed. 101 std::unique_ptr<BlockFrequencyInfo> OwnedBFI; 102 103 /// Compute hotness from IR value (currently assumed to be a block) if PGO is 104 /// available. 105 Optional<uint64_t> computeHotness(const Value *V); 106 107 /// Similar but use value from \p OptDiag and update hotness there. 108 void computeHotness(DiagnosticInfoIROptimization &OptDiag); 109 110 /// Only allow verbose messages if we know we're filtering by hotness 111 /// (BFI is only set in this case). shouldEmitVerbose()112 bool shouldEmitVerbose() { return BFI != nullptr; } 113 114 OptimizationRemarkEmitter(const OptimizationRemarkEmitter &) = delete; 115 void operator=(const OptimizationRemarkEmitter &) = delete; 116 }; 117 118 /// Add a small namespace to avoid name clashes with the classes used in 119 /// the streaming interface. We want these to be short for better 120 /// write/readability. 121 namespace ore { 122 using NV = DiagnosticInfoOptimizationBase::Argument; 123 using setIsVerbose = DiagnosticInfoOptimizationBase::setIsVerbose; 124 using setExtraArgs = DiagnosticInfoOptimizationBase::setExtraArgs; 125 } 126 127 /// OptimizationRemarkEmitter legacy analysis pass 128 /// 129 /// Note that this pass shouldn't generally be marked as preserved by other 130 /// passes. It's holding onto BFI, so if the pass does not preserve BFI, BFI 131 /// could be freed. 132 class OptimizationRemarkEmitterWrapperPass : public FunctionPass { 133 std::unique_ptr<OptimizationRemarkEmitter> ORE; 134 135 public: 136 OptimizationRemarkEmitterWrapperPass(); 137 138 bool runOnFunction(Function &F) override; 139 140 void getAnalysisUsage(AnalysisUsage &AU) const override; 141 getORE()142 OptimizationRemarkEmitter &getORE() { 143 assert(ORE && "pass not run yet"); 144 return *ORE; 145 } 146 147 static char ID; 148 }; 149 150 class OptimizationRemarkEmitterAnalysis 151 : public AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis> { 152 friend AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis>; 153 static AnalysisKey Key; 154 155 public: 156 /// Provide the result typedef for this analysis pass. 157 typedef OptimizationRemarkEmitter Result; 158 159 /// Run the analysis pass over a function and produce BFI. 160 Result run(Function &F, FunctionAnalysisManager &AM); 161 }; 162 } 163 #endif // LLVM_IR_OPTIMIZATIONDIAGNOSTICINFO_H 164