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
16#include "llvm/CodeGen/MachineBasicBlock.h"
17#include "llvm/CodeGen/MachinePassManager.h"
18#include "llvm/Pass.h"
19#include "llvm/Support/BranchProbability.h"
20
21namespace llvm {
22
23class MachineBranchProbabilityInfo {
24 // Default weight value. Used when we don't have information about the edge.
25 // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
26 // the successors have a weight yet. But it doesn't make sense when providing
27 // weight to an edge that may have siblings with non-zero weights. This can
28 // be handled various ways, but it's probably fine for an edge with unknown
29 // weight to just "inherit" the non-zero weight of an adjacent successor.
30 static const uint32_t DEFAULT_WEIGHT = 16;
31
32public:
33 bool invalidate(MachineFunction &, const PreservedAnalyses &PA,
34 MachineFunctionAnalysisManager::Invalidator &);
35
36 // Return edge probability.
37 BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
38 const MachineBasicBlock *Dst) const;
39
40 // Same as above, but using a const_succ_iterator from Src. This is faster
41 // when the iterator is already available.
42 BranchProbability
43 getEdgeProbability(const MachineBasicBlock *Src,
44 MachineBasicBlock::const_succ_iterator Dst) const;
45
46 // A 'Hot' edge is an edge which probability is >= 80%.
47 bool isEdgeHot(const MachineBasicBlock *Src,
48 const MachineBasicBlock *Dst) const;
49
50 // Print value between 0 (0% probability) and 1 (100% probability),
51 // however the value is never equal to 0, and can be 1 only iff SRC block
52 // has only one successor.
53 raw_ostream &printEdgeProbability(raw_ostream &OS,
54 const MachineBasicBlock *Src,
55 const MachineBasicBlock *Dst) const;
56};
57
58class MachineBranchProbabilityAnalysis
59 : public AnalysisInfoMixin<MachineBranchProbabilityAnalysis> {
60 friend AnalysisInfoMixin<MachineBranchProbabilityAnalysis>;
61
62 static AnalysisKey Key;
63
64public:
65 using Result = MachineBranchProbabilityInfo;
66
67 Result run(MachineFunction &, MachineFunctionAnalysisManager &);
68};
69
70class MachineBranchProbabilityPrinterPass
71 : public PassInfoMixin<MachineBranchProbabilityPrinterPass> {
72 raw_ostream &OS;
73
74public:
75 MachineBranchProbabilityPrinterPass(raw_ostream &OS) : OS(OS) {}
76 PreservedAnalyses run(MachineFunction &MF,
77 MachineFunctionAnalysisManager &MFAM);
78};
79
80class MachineBranchProbabilityInfoWrapperPass : public ImmutablePass {
81 virtual void anchor();
82
83 MachineBranchProbabilityInfo MBPI;
84
85public:
86 static char ID;
87
88 MachineBranchProbabilityInfoWrapperPass();
89
90 void getAnalysisUsage(AnalysisUsage &AU) const override {
91 AU.setPreservesAll();
92 }
93
94 MachineBranchProbabilityInfo &getMBPI() { return MBPI; }
95 const MachineBranchProbabilityInfo &getMBPI() const { return MBPI; }
96};
97}
98
99
100#endif
101