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_ANALYSIS_OPTIMIZATIONREMARKEMITTER_H 15 #define LLVM_ANALYSIS_OPTIMIZATIONREMARKEMITTER_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 /// Return true iff at least *some* remarks are enabled. enabled()65 bool enabled() const { 66 return F->getContext().getLLVMRemarkStreamer() || 67 F->getContext().getDiagHandlerPtr()->isAnyRemarkEnabled(); 68 } 69 70 /// Output the remark via the diagnostic handler and to the 71 /// optimization record file. 72 void emit(DiagnosticInfoOptimizationBase &OptDiag); 73 74 /// Take a lambda that returns a remark which will be emitted. Second 75 /// argument is only used to restrict this to functions. 76 template <typename T> 77 void emit(T RemarkBuilder, decltype(RemarkBuilder()) * = nullptr) { 78 // Avoid building the remark unless we know there are at least *some* 79 // remarks enabled. We can't currently check whether remarks are requested 80 // for the calling pass since that requires actually building the remark. 81 82 if (enabled()) { 83 auto R = RemarkBuilder(); 84 static_assert( 85 std::is_base_of<DiagnosticInfoOptimizationBase, decltype(R)>::value, 86 "the lambda passed to emit() must return a remark"); 87 emit((DiagnosticInfoOptimizationBase &)R); 88 } 89 } 90 91 /// Whether we allow for extra compile-time budget to perform more 92 /// analysis to produce fewer false positives. 93 /// 94 /// This is useful when reporting missed optimizations. In this case we can 95 /// use the extra analysis (1) to filter trivial false positives or (2) to 96 /// provide more context so that non-trivial false positives can be quickly 97 /// detected by the user. allowExtraAnalysis(StringRef PassName)98 bool allowExtraAnalysis(StringRef PassName) const { 99 return OptimizationRemarkEmitter::allowExtraAnalysis(*F, PassName); 100 } allowExtraAnalysis(const Function & F,StringRef PassName)101 static bool allowExtraAnalysis(const Function &F, StringRef PassName) { 102 return allowExtraAnalysis(F.getContext(), PassName); 103 } allowExtraAnalysis(LLVMContext & Ctx,StringRef PassName)104 static bool allowExtraAnalysis(LLVMContext &Ctx, StringRef PassName) { 105 return Ctx.getLLVMRemarkStreamer() || 106 Ctx.getDiagHandlerPtr()->isAnyRemarkEnabled(PassName); 107 } 108 109 private: 110 const Function *F; 111 112 BlockFrequencyInfo *BFI; 113 114 /// If we generate BFI on demand, we need to free it when ORE is freed. 115 std::unique_ptr<BlockFrequencyInfo> OwnedBFI; 116 117 /// Compute hotness from IR value (currently assumed to be a block) if PGO is 118 /// available. 119 Optional<uint64_t> computeHotness(const Value *V); 120 121 /// Similar but use value from \p OptDiag and update hotness there. 122 void computeHotness(DiagnosticInfoIROptimization &OptDiag); 123 124 /// Only allow verbose messages if we know we're filtering by hotness 125 /// (BFI is only set in this case). shouldEmitVerbose()126 bool shouldEmitVerbose() { return BFI != nullptr; } 127 128 OptimizationRemarkEmitter(const OptimizationRemarkEmitter &) = delete; 129 void operator=(const OptimizationRemarkEmitter &) = delete; 130 }; 131 132 /// Add a small namespace to avoid name clashes with the classes used in 133 /// the streaming interface. We want these to be short for better 134 /// write/readability. 135 namespace ore { 136 using NV = DiagnosticInfoOptimizationBase::Argument; 137 using setIsVerbose = DiagnosticInfoOptimizationBase::setIsVerbose; 138 using setExtraArgs = DiagnosticInfoOptimizationBase::setExtraArgs; 139 } 140 141 /// OptimizationRemarkEmitter legacy analysis pass 142 /// 143 /// Note that this pass shouldn't generally be marked as preserved by other 144 /// passes. It's holding onto BFI, so if the pass does not preserve BFI, BFI 145 /// could be freed. 146 class OptimizationRemarkEmitterWrapperPass : public FunctionPass { 147 std::unique_ptr<OptimizationRemarkEmitter> ORE; 148 149 public: 150 OptimizationRemarkEmitterWrapperPass(); 151 152 bool runOnFunction(Function &F) override; 153 154 void getAnalysisUsage(AnalysisUsage &AU) const override; 155 getORE()156 OptimizationRemarkEmitter &getORE() { 157 assert(ORE && "pass not run yet"); 158 return *ORE; 159 } 160 161 static char ID; 162 }; 163 164 class OptimizationRemarkEmitterAnalysis 165 : public AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis> { 166 friend AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis>; 167 static AnalysisKey Key; 168 169 public: 170 /// Provide the result typedef for this analysis pass. 171 typedef OptimizationRemarkEmitter Result; 172 173 /// Run the analysis pass over a function and produce BFI. 174 Result run(Function &F, FunctionAnalysisManager &AM); 175 }; 176 } 177 #endif // LLVM_ANALYSIS_OPTIMIZATIONREMARKEMITTER_H 178