LLVM 20.0.0git
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
22namespace llvm {
23class AnalysisUsage;
24class Function;
25class LoopInfo;
26class 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 : 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, nullptr, nullptr);
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 = false;
79 const Function *F;
80 const LoopInfo *LI;
81 const TargetLibraryInfo *TLI;
82 };
83
84 std::unique_ptr<LazyBranchProbabilityInfo> LBPI;
85
86public:
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.
109void initializeLazyBPIPassPass(PassRegistry &Registry);
110
111/// Simple trait class that provides a mapping between BPI passes and the
112/// corresponding BPInfo.
113template <typename PassT> struct BPIPassTrait {
114 static PassT &getBPI(PassT *P) { return *P; }
115};
116
119 return P->getBPI();
120 }
121};
122}
123#endif
#define F(x, y, z)
Definition: MD5.cpp:55
#define P(N)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
Represent the analysis usage information of a pass.
Analysis providing branch probability information.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:310
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...
bool runOnFunction(Function &F) override
runOnFunction - Virtual method overriden by subclasses to do the per-function processing of the pass.
void releaseMemory() override
releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memo...
const BranchProbabilityInfo & getBPI() const
Compute and return the branch probabilities.
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.
static void getLazyBPIAnalysisUsage(AnalysisUsage &AU)
Helper for client passes to set up the analysis usage on behalf of this pass.
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
Provides information about what library functions are available for the current target.
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void initializeLazyBPIPassPass(PassRegistry &Registry)
Helper for client passes to initialize dependent passes for LBPI.
static BranchProbabilityInfo & getBPI(LazyBranchProbabilityInfoPass *P)
Simple trait class that provides a mapping between BPI passes and the corresponding BPInfo.
static PassT & getBPI(PassT *P)