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MachineBranchProbabilityInfo.h
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1 //=- MachineBranchProbabilityInfo.h - Branch Probability Analysis -*- 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 pass is used to evaluate branch probabilties on machine basic blocks.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
14 #define LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
15 
17 #include "llvm/Pass.h"
19 #include <climits>
20 #include <numeric>
21 
22 namespace llvm {
23 
25  virtual void anchor();
26 
27  // Default weight value. Used when we don't have information about the edge.
28  // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
29  // the successors have a weight yet. But it doesn't make sense when providing
30  // weight to an edge that may have siblings with non-zero weights. This can
31  // be handled various ways, but it's probably fine for an edge with unknown
32  // weight to just "inherit" the non-zero weight of an adjacent successor.
33  static const uint32_t DEFAULT_WEIGHT = 16;
34 
35 public:
36  static char ID;
37 
39 
40  void getAnalysisUsage(AnalysisUsage &AU) const override {
41  AU.setPreservesAll();
42  }
43 
44  // Return edge probability.
46  const MachineBasicBlock *Dst) const;
47 
48  // Same as above, but using a const_succ_iterator from Src. This is faster
49  // when the iterator is already available.
53 
54  // A 'Hot' edge is an edge which probability is >= 80%.
55  bool isEdgeHot(const MachineBasicBlock *Src,
56  const MachineBasicBlock *Dst) const;
57 
58  // Return a hot successor for the block BB or null if there isn't one.
59  // NB: This routine's complexity is linear on the number of successors.
61 
62  // Print value between 0 (0% probability) and 1 (100% probability),
63  // however the value is never equal to 0, and can be 1 only iff SRC block
64  // has only one successor.
66  const MachineBasicBlock *Src,
67  const MachineBasicBlock *Dst) const;
68 };
69 
70 }
71 
72 
73 #endif
llvm::MachineBranchProbabilityInfo::MachineBranchProbabilityInfo
MachineBranchProbabilityInfo()
Definition: MachineBranchProbabilityInfo.cpp:44
llvm
Definition: AllocatorList.h:23
llvm::ImmutablePass
ImmutablePass class - This class is used to provide information that does not need to be run.
Definition: Pass.h:269
Pass.h
llvm::MachineBranchProbabilityInfo::ID
static char ID
Definition: MachineBranchProbabilityInfo.h:36
MachineBasicBlock.h
llvm::MachineBranchProbabilityInfo::getHotSucc
MachineBasicBlock * getHotSucc(MachineBasicBlock *MBB) const
Definition: MachineBranchProbabilityInfo.cpp:72
llvm::MachineBranchProbabilityInfo::printEdgeProbability
raw_ostream & printEdgeProbability(raw_ostream &OS, const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
Definition: MachineBranchProbabilityInfo.cpp:91
llvm::MachineBranchProbabilityInfo
Definition: MachineBranchProbabilityInfo.h:24
llvm::AnalysisUsage
Represent the analysis usage information of a pass.
Definition: PassAnalysisSupport.h:47
llvm::MachineBranchProbabilityInfo::getAnalysisUsage
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: MachineBranchProbabilityInfo.h:40
llvm::raw_ostream
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:50
BranchProbability.h
llvm::MachineBasicBlock
Definition: MachineBasicBlock.h:95
llvm::MachineBranchProbabilityInfo::getEdgeProbability
BranchProbability getEdgeProbability(const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
Definition: MachineBranchProbabilityInfo.cpp:58
uint32_t
llvm::BranchProbability
Definition: BranchProbability.h:30
MBB
MachineBasicBlock & MBB
Definition: AArch64SLSHardening.cpp:74
llvm::AnalysisUsage::setPreservesAll
void setPreservesAll()
Set by analyses that do not transform their input at all.
Definition: PassAnalysisSupport.h:130
llvm::MachineBasicBlock::const_succ_iterator
std::vector< MachineBasicBlock * >::const_iterator const_succ_iterator
Definition: MachineBasicBlock.h:307
llvm::MachineBranchProbabilityInfo::isEdgeHot
bool isEdgeHot(const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
Definition: MachineBranchProbabilityInfo.cpp:65