1 //===- OptimizationRemarkEmitter.cpp - 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 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
15 #include "llvm/Analysis/BranchProbabilityInfo.h"
16 #include "llvm/Analysis/LazyBlockFrequencyInfo.h"
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/IR/DiagnosticInfo.h"
19 #include "llvm/IR/Dominators.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/InitializePasses.h"
22 
23 using namespace llvm;
24 
25 OptimizationRemarkEmitter::OptimizationRemarkEmitter(const Function *F)
26     : F(F), BFI(nullptr) {
27   if (!F->getContext().getDiagnosticsHotnessRequested())
28     return;
29 
30   // First create a dominator tree.
31   DominatorTree DT;
32   DT.recalculate(*const_cast<Function *>(F));
33 
34   // Generate LoopInfo from it.
35   LoopInfo LI;
36   LI.analyze(DT);
37 
38   // Then compute BranchProbabilityInfo.
39   BranchProbabilityInfo BPI;
40   BPI.calculate(*F, LI);
41 
42   // Finally compute BFI.
43   OwnedBFI = std::make_unique<BlockFrequencyInfo>(*F, BPI, LI);
44   BFI = OwnedBFI.get();
45 }
46 
47 bool OptimizationRemarkEmitter::invalidate(
48     Function &F, const PreservedAnalyses &PA,
49     FunctionAnalysisManager::Invalidator &Inv) {
50   if (OwnedBFI.get()) {
51     OwnedBFI.reset();
52     BFI = nullptr;
53   }
54   // This analysis has no state and so can be trivially preserved but it needs
55   // a fresh view of BFI if it was constructed with one.
56   if (BFI && Inv.invalidate<BlockFrequencyAnalysis>(F, PA))
57     return true;
58 
59   // Otherwise this analysis result remains valid.
60   return false;
61 }
62 
63 Optional<uint64_t> OptimizationRemarkEmitter::computeHotness(const Value *V) {
64   if (!BFI)
65     return None;
66 
67   return BFI->getBlockProfileCount(cast<BasicBlock>(V));
68 }
69 
70 void OptimizationRemarkEmitter::computeHotness(
71     DiagnosticInfoIROptimization &OptDiag) {
72   const Value *V = OptDiag.getCodeRegion();
73   if (V)
74     OptDiag.setHotness(computeHotness(V));
75 }
76 
77 void OptimizationRemarkEmitter::emit(
78     DiagnosticInfoOptimizationBase &OptDiagBase) {
79   auto &OptDiag = cast<DiagnosticInfoIROptimization>(OptDiagBase);
80   computeHotness(OptDiag);
81 
82   // Only emit it if its hotness meets the threshold.
83   if (OptDiag.getHotness().getValueOr(0) <
84       F->getContext().getDiagnosticsHotnessThreshold()) {
85     return;
86   }
87 
88   F->getContext().diagnose(OptDiag);
89 }
90 
91 OptimizationRemarkEmitterWrapperPass::OptimizationRemarkEmitterWrapperPass()
92     : FunctionPass(ID) {
93   initializeOptimizationRemarkEmitterWrapperPassPass(
94       *PassRegistry::getPassRegistry());
95 }
96 
97 bool OptimizationRemarkEmitterWrapperPass::runOnFunction(Function &Fn) {
98   BlockFrequencyInfo *BFI;
99 
100   if (Fn.getContext().getDiagnosticsHotnessRequested())
101     BFI = &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI();
102   else
103     BFI = nullptr;
104 
105   ORE = std::make_unique<OptimizationRemarkEmitter>(&Fn, BFI);
106   return false;
107 }
108 
109 void OptimizationRemarkEmitterWrapperPass::getAnalysisUsage(
110     AnalysisUsage &AU) const {
111   LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU);
112   AU.setPreservesAll();
113 }
114 
115 AnalysisKey OptimizationRemarkEmitterAnalysis::Key;
116 
117 OptimizationRemarkEmitter
118 OptimizationRemarkEmitterAnalysis::run(Function &F,
119                                        FunctionAnalysisManager &AM) {
120   BlockFrequencyInfo *BFI;
121 
122   if (F.getContext().getDiagnosticsHotnessRequested())
123     BFI = &AM.getResult<BlockFrequencyAnalysis>(F);
124   else
125     BFI = nullptr;
126 
127   return OptimizationRemarkEmitter(&F, BFI);
128 }
129 
130 char OptimizationRemarkEmitterWrapperPass::ID = 0;
131 static const char ore_name[] = "Optimization Remark Emitter";
132 #define ORE_NAME "opt-remark-emitter"
133 
134 INITIALIZE_PASS_BEGIN(OptimizationRemarkEmitterWrapperPass, ORE_NAME, ore_name,
135                       false, true)
136 INITIALIZE_PASS_DEPENDENCY(LazyBFIPass)
137 INITIALIZE_PASS_END(OptimizationRemarkEmitterWrapperPass, ORE_NAME, ore_name,
138                     false, true)
139