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1 ///===- LazyMachineBlockFrequencyInfo.h - Lazy Block Frequency -*- C++ -*--===//
2 ///
3 ///                     The LLVM Compiler Infrastructure
4 ///
5 /// This file is distributed under the University of Illinois Open Source
6 /// License. See LICENSE.TXT for details.
7 ///
8 ///===---------------------------------------------------------------------===//
9 /// \file
10 /// This is an alternative analysis pass to MachineBlockFrequencyInfo.  The
11 /// difference is that with this pass the block frequencies are not computed
12 /// when the analysis pass is executed but rather when the BFI result is
13 /// explicitly requested by the analysis client.
14 ///
15 ///===---------------------------------------------------------------------===//
16 
17 #ifndef LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
18 #define LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
19 
20 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
21 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
22 #include "llvm/CodeGen/MachineDominators.h"
23 #include "llvm/CodeGen/MachineLoopInfo.h"
24 
25 namespace llvm {
26 /// This is an alternative analysis pass to MachineBlockFrequencyInfo.
27 /// The difference is that with this pass, the block frequencies are not
28 /// computed when the analysis pass is executed but rather when the BFI result
29 /// is explicitly requested by the analysis client.
30 ///
31 /// This works by checking querying if MBFI is available and otherwise
32 /// generating MBFI on the fly.  In this case the passes required for (LI, DT)
33 /// are also queried before being computed on the fly.
34 ///
35 /// Note that it is expected that we wouldn't need this functionality for the
36 /// new PM since with the new PM, analyses are executed on demand.
37 
38 class LazyMachineBlockFrequencyInfoPass : public MachineFunctionPass {
39 private:
40   /// If generated on the fly this own the instance.
41   mutable std::unique_ptr<MachineBlockFrequencyInfo> OwnedMBFI;
42 
43   /// If generated on the fly this own the instance.
44   mutable std::unique_ptr<MachineLoopInfo> OwnedMLI;
45 
46   /// If generated on the fly this own the instance.
47   mutable std::unique_ptr<MachineDominatorTree> OwnedMDT;
48 
49   /// The function.
50   MachineFunction *MF = nullptr;
51 
52   /// Calculate MBFI and all other analyses that's not available and
53   /// required by BFI.
54   MachineBlockFrequencyInfo &calculateIfNotAvailable() const;
55 
56 public:
57   static char ID;
58 
59   LazyMachineBlockFrequencyInfoPass();
60 
61   /// Compute and return the block frequencies.
getBFI()62   MachineBlockFrequencyInfo &getBFI() { return calculateIfNotAvailable(); }
63 
64   /// Compute and return the block frequencies.
getBFI()65   const MachineBlockFrequencyInfo &getBFI() const {
66     return calculateIfNotAvailable();
67   }
68 
69   void getAnalysisUsage(AnalysisUsage &AU) const override;
70 
71   bool runOnMachineFunction(MachineFunction &F) override;
72   void releaseMemory() override;
73   void print(raw_ostream &OS, const Module *M) const override;
74 };
75 }
76 #endif
77