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| Rev | Author | Line No. | Line |
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| 14 | pmbaty | 1 | //===- LazyBlockFrequencyInfo.h - Lazy Block Frequency Analysis -*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This is an alternative analysis pass to BlockFrequencyInfoWrapperPass. The |
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| 10 | // difference is that with this pass the block frequencies are not computed when |
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| 11 | // the analysis pass is executed but rather when the BFI result is explicitly |
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| 12 | // requested by the analysis client. |
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| 13 | // |
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| 14 | //===----------------------------------------------------------------------===// |
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| 15 | |||
| 16 | #ifndef LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H |
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| 17 | #define LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H |
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| 18 | |||
| 19 | #include "llvm/Analysis/BlockFrequencyInfo.h" |
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| 20 | #include "llvm/Analysis/LazyBranchProbabilityInfo.h" |
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| 21 | #include "llvm/Pass.h" |
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| 22 | |||
| 23 | namespace llvm { |
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| 24 | class AnalysisUsage; |
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| 25 | class Function; |
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| 26 | class LoopInfo; |
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| 27 | |||
| 28 | /// Wraps a BFI to allow lazy computation of the block frequencies. |
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| 29 | /// |
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| 30 | /// A pass that only conditionally uses BFI can uncondtionally require the |
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| 31 | /// analysis without paying for the overhead if BFI doesn't end up being used. |
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| 32 | template <typename FunctionT, typename BranchProbabilityInfoPassT, |
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| 33 | typename LoopInfoT, typename BlockFrequencyInfoT> |
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| 34 | class LazyBlockFrequencyInfo { |
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| 35 | public: |
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| 36 | LazyBlockFrequencyInfo() = default; |
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| 37 | |||
| 38 | /// Set up the per-function input. |
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| 39 | void setAnalysis(const FunctionT *F, BranchProbabilityInfoPassT *BPIPass, |
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| 40 | const LoopInfoT *LI) { |
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| 41 | this->F = F; |
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| 42 | this->BPIPass = BPIPass; |
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| 43 | this->LI = LI; |
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| 44 | } |
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| 45 | |||
| 46 | /// Retrieve the BFI with the block frequencies computed. |
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| 47 | BlockFrequencyInfoT &getCalculated() { |
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| 48 | if (!Calculated) { |
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| 49 | assert(F && BPIPass && LI && "call setAnalysis"); |
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| 50 | BFI.calculate( |
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| 51 | *F, BPIPassTrait<BranchProbabilityInfoPassT>::getBPI(BPIPass), *LI); |
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| 52 | Calculated = true; |
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| 53 | } |
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| 54 | return BFI; |
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| 55 | } |
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| 56 | |||
| 57 | const BlockFrequencyInfoT &getCalculated() const { |
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| 58 | return const_cast<LazyBlockFrequencyInfo *>(this)->getCalculated(); |
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| 59 | } |
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| 60 | |||
| 61 | void releaseMemory() { |
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| 62 | BFI.releaseMemory(); |
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| 63 | Calculated = false; |
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| 64 | setAnalysis(nullptr, nullptr, nullptr); |
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| 65 | } |
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| 66 | |||
| 67 | private: |
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| 68 | BlockFrequencyInfoT BFI; |
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| 69 | bool Calculated = false; |
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| 70 | const FunctionT *F = nullptr; |
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| 71 | BranchProbabilityInfoPassT *BPIPass = nullptr; |
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| 72 | const LoopInfoT *LI = nullptr; |
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| 73 | }; |
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| 74 | |||
| 75 | /// This is an alternative analysis pass to |
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| 76 | /// BlockFrequencyInfoWrapperPass. The difference is that with this pass the |
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| 77 | /// block frequencies are not computed when the analysis pass is executed but |
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| 78 | /// rather when the BFI result is explicitly requested by the analysis client. |
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| 79 | /// |
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| 80 | /// There are some additional requirements for any client pass that wants to use |
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| 81 | /// the analysis: |
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| 82 | /// |
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| 83 | /// 1. The pass needs to initialize dependent passes with: |
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| 84 | /// |
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| 85 | /// INITIALIZE_PASS_DEPENDENCY(LazyBFIPass) |
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| 86 | /// |
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| 87 | /// 2. Similarly, getAnalysisUsage should call: |
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| 88 | /// |
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| 89 | /// LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU) |
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| 90 | /// |
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| 91 | /// 3. The computed BFI should be requested with |
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| 92 | /// getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() before either LoopInfo |
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| 93 | /// or BPI could be invalidated for example by changing the CFG. |
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| 94 | /// |
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| 95 | /// Note that it is expected that we wouldn't need this functionality for the |
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| 96 | /// new PM since with the new PM, analyses are executed on demand. |
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| 97 | |||
| 98 | class LazyBlockFrequencyInfoPass : public FunctionPass { |
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| 99 | private: |
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| 100 | LazyBlockFrequencyInfo<Function, LazyBranchProbabilityInfoPass, LoopInfo, |
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| 101 | BlockFrequencyInfo> |
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| 102 | LBFI; |
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| 103 | |||
| 104 | public: |
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| 105 | static char ID; |
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| 106 | |||
| 107 | LazyBlockFrequencyInfoPass(); |
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| 108 | |||
| 109 | /// Compute and return the block frequencies. |
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| 110 | BlockFrequencyInfo &getBFI() { return LBFI.getCalculated(); } |
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| 111 | |||
| 112 | /// Compute and return the block frequencies. |
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| 113 | const BlockFrequencyInfo &getBFI() const { return LBFI.getCalculated(); } |
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| 114 | |||
| 115 | void getAnalysisUsage(AnalysisUsage &AU) const override; |
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| 116 | |||
| 117 | /// Helper for client passes to set up the analysis usage on behalf of this |
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| 118 | /// pass. |
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| 119 | static void getLazyBFIAnalysisUsage(AnalysisUsage &AU); |
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| 120 | |||
| 121 | bool runOnFunction(Function &F) override; |
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| 122 | void releaseMemory() override; |
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| 123 | void print(raw_ostream &OS, const Module *M) const override; |
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| 124 | }; |
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| 125 | |||
| 126 | /// Helper for client passes to initialize dependent passes for LBFI. |
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| 127 | void initializeLazyBFIPassPass(PassRegistry &Registry); |
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| 128 | } |
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| 129 | #endif |