LLVM  10.0.0svn
LazyBranchProbabilityInfo.h
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1 //===- LazyBranchProbabilityInfo.h - Lazy Branch Probability ----*- 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 // This is an alternative analysis pass to BranchProbabilityInfoWrapperPass.
10 // The difference is that with this pass the branch probabilities are not
11 // computed when the analysis pass is executed but rather when the BPI results
12 // is explicitly requested by the analysis client.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H
17 #define LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H
18 
20 #include "llvm/Pass.h"
21 
22 namespace llvm {
23 class AnalysisUsage;
24 class Function;
25 class LoopInfo;
26 class TargetLibraryInfo;
27 
28 /// This is an alternative analysis pass to
29 /// BranchProbabilityInfoWrapperPass. The difference is that with this pass the
30 /// branch probabilities are not computed when the analysis pass is executed but
31 /// rather when the BPI results is explicitly requested by the analysis client.
32 ///
33 /// There are some additional requirements for any client pass that wants to use
34 /// the analysis:
35 ///
36 /// 1. The pass needs to initialize dependent passes with:
37 ///
38 /// INITIALIZE_PASS_DEPENDENCY(LazyBPIPass)
39 ///
40 /// 2. Similarly, getAnalysisUsage should call:
41 ///
42 /// LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU)
43 ///
44 /// 3. The computed BPI should be requested with
45 /// getAnalysis<LazyBranchProbabilityInfoPass>().getBPI() before LoopInfo
46 /// could be invalidated for example by changing the CFG.
47 ///
48 /// Note that it is expected that we wouldn't need this functionality for the
49 /// new PM since with the new PM, analyses are executed on demand.
51 
52  /// Wraps a BPI to allow lazy computation of the branch probabilities.
53  ///
54  /// A pass that only conditionally uses BPI can uncondtionally require the
55  /// analysis without paying for the overhead if BPI doesn't end up being used.
56  class LazyBranchProbabilityInfo {
57  public:
58  LazyBranchProbabilityInfo(const Function *F, const LoopInfo *LI,
59  const TargetLibraryInfo *TLI)
60  : Calculated(false), F(F), LI(LI), TLI(TLI) {}
61 
62  /// Retrieve the BPI with the branch probabilities computed.
63  BranchProbabilityInfo &getCalculated() {
64  if (!Calculated) {
65  assert(F && LI && "call setAnalysis");
66  BPI.calculate(*F, *LI, TLI);
67  Calculated = true;
68  }
69  return BPI;
70  }
71 
72  const BranchProbabilityInfo &getCalculated() const {
73  return const_cast<LazyBranchProbabilityInfo *>(this)->getCalculated();
74  }
75 
76  private:
78  bool Calculated;
79  const Function *F;
80  const LoopInfo *LI;
81  const TargetLibraryInfo *TLI;
82  };
83 
84  std::unique_ptr<LazyBranchProbabilityInfo> LBPI;
85 
86 public:
87  static char ID;
88 
90 
91  /// Compute and return the branch probabilities.
92  BranchProbabilityInfo &getBPI() { return LBPI->getCalculated(); }
93 
94  /// Compute and return the branch probabilities.
95  const BranchProbabilityInfo &getBPI() const { return LBPI->getCalculated(); }
96 
97  void getAnalysisUsage(AnalysisUsage &AU) const override;
98 
99  /// Helper for client passes to set up the analysis usage on behalf of this
100  /// pass.
101  static void getLazyBPIAnalysisUsage(AnalysisUsage &AU);
102 
103  bool runOnFunction(Function &F) override;
104  void releaseMemory() override;
105  void print(raw_ostream &OS, const Module *M) const override;
106 };
107 
108 /// Helper for client passes to initialize dependent passes for LBPI.
110 
111 /// Simple trait class that provides a mapping between BPI passes and the
112 /// corresponding BPInfo.
113 template <typename PassT> struct BPIPassTrait {
114  static PassT &getBPI(PassT *P) { return *P; }
115 };
116 
119  return P->getBPI();
120  }
121 };
122 }
123 #endif
static BranchProbabilityInfo & getBPI(LazyBranchProbabilityInfoPass *P)
const BranchProbabilityInfo & getBPI() const
Compute and return the branch probabilities.
This class represents lattice values for constants.
Definition: AllocatorList.h:23
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:66
A global registry used in conjunction with static constructors to make pluggable components (like tar...
Definition: Registry.h:44
void releaseMemory() override
releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memo...
static void getLazyBPIAnalysisUsage(AnalysisUsage &AU)
Helper for client passes to set up the analysis usage on behalf of this pass.
F(f)
Simple trait class that provides a mapping between BPI passes and the corresponding BPInfo...
This is an alternative analysis pass to BranchProbabilityInfoWrapperPass.
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
#define P(N)
void initializeLazyBPIPassPass(PassRegistry &Registry)
Helper for client passes to initialize dependent passes for LBPI.
bool runOnFunction(Function &F) override
runOnFunction - Virtual method overriden by subclasses to do the per-function processing of the pass...
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
Provides information about what library functions are available for the current target.
void print(raw_ostream &OS, const Module *M) const override
print - Print out the internal state of the pass.
BranchProbabilityInfo & getBPI()
Compute and return the branch probabilities.
Analysis providing branch probability information.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
PassRegistry - This class manages the registration and intitialization of the pass subsystem as appli...
Definition: PassRegistry.h:38
static PassT & getBPI(PassT *P)