LLVM 17.0.0git
MachineBranchProbabilityInfo.h
Go to the documentation of this file.
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
20namespace llvm {
21
23 virtual void anchor();
24
25 // Default weight value. Used when we don't have information about the edge.
26 // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
27 // the successors have a weight yet. But it doesn't make sense when providing
28 // weight to an edge that may have siblings with non-zero weights. This can
29 // be handled various ways, but it's probably fine for an edge with unknown
30 // weight to just "inherit" the non-zero weight of an adjacent successor.
31 static const uint32_t DEFAULT_WEIGHT = 16;
32
33public:
34 static char ID;
35
37
38 void getAnalysisUsage(AnalysisUsage &AU) const override {
39 AU.setPreservesAll();
40 }
41
42 // Return edge probability.
44 const MachineBasicBlock *Dst) const;
45
46 // Same as above, but using a const_succ_iterator from Src. This is faster
47 // when the iterator is already available.
51
52 // A 'Hot' edge is an edge which probability is >= 80%.
53 bool isEdgeHot(const MachineBasicBlock *Src,
54 const MachineBasicBlock *Dst) const;
55
56 // Print value between 0 (0% probability) and 1 (100% probability),
57 // however the value is never equal to 0, and can be 1 only iff SRC block
58 // has only one successor.
60 const MachineBasicBlock *Src,
61 const MachineBasicBlock *Dst) const;
62};
63
64}
65
66
67#endif
Represent the analysis usage information of a pass.
void setPreservesAll()
Set by analyses that do not transform their input at all.
ImmutablePass class - This class is used to provide information that does not need to be run.
Definition: Pass.h:279
std::vector< MachineBasicBlock * >::const_iterator const_succ_iterator
raw_ostream & printEdgeProbability(raw_ostream &OS, const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
bool isEdgeHot(const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
BranchProbability getEdgeProbability(const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const
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