1//===- MachineBlockFrequencyInfo.h - MBB Frequency 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// Loops should be simplified before this analysis.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
14#define LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
15
16#include "llvm/CodeGen/MachineFunctionPass.h"
17#include "llvm/Support/BlockFrequency.h"
18#include <cstdint>
19#include <memory>
20#include <optional>
21
22namespace llvm {
23
24template <class BlockT> class BlockFrequencyInfoImpl;
25class MachineBasicBlock;
26class MachineBranchProbabilityInfo;
27class MachineFunction;
28class MachineLoopInfo;
29class raw_ostream;
30
31/// MachineBlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation
32/// to estimate machine basic block frequencies.
33class MachineBlockFrequencyInfo : public MachineFunctionPass {
34 using ImplType = BlockFrequencyInfoImpl<MachineBasicBlock>;
35 std::unique_ptr<ImplType> MBFI;
36
37public:
38 static char ID;
39
40 MachineBlockFrequencyInfo();
41 explicit MachineBlockFrequencyInfo(MachineFunction &F,
42 MachineBranchProbabilityInfo &MBPI,
43 MachineLoopInfo &MLI);
44 ~MachineBlockFrequencyInfo() override;
45
46 void getAnalysisUsage(AnalysisUsage &AU) const override;
47
48 bool runOnMachineFunction(MachineFunction &F) override;
49
50 /// calculate - compute block frequency info for the given function.
51 void calculate(const MachineFunction &F,
52 const MachineBranchProbabilityInfo &MBPI,
53 const MachineLoopInfo &MLI);
54
55 void releaseMemory() override;
56
57 /// getblockFreq - Return block frequency. Return 0 if we don't have the
58 /// information. Please note that initial frequency is equal to 1024. It means
59 /// that we should not rely on the value itself, but only on the comparison to
60 /// the other block frequencies. We do this to avoid using of floating points.
61 /// For example, to get the frequency of a block relative to the entry block,
62 /// divide the integral value returned by this function (the
63 /// BlockFrequency::getFrequency() value) by getEntryFreq().
64 BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
65
66 /// Compute the frequency of the block, relative to the entry block.
67 /// This API assumes getEntryFreq() is non-zero.
68 double getBlockFreqRelativeToEntryBlock(const MachineBasicBlock *MBB) const {
69 assert(getEntryFreq() != BlockFrequency(0) &&
70 "getEntryFreq() should not return 0 here!");
71 return static_cast<double>(getBlockFreq(MBB).getFrequency()) /
72 static_cast<double>(getEntryFreq().getFrequency());
73 }
74
75 std::optional<uint64_t>
76 getBlockProfileCount(const MachineBasicBlock *MBB) const;
77 std::optional<uint64_t> getProfileCountFromFreq(BlockFrequency Freq) const;
78
79 bool isIrrLoopHeader(const MachineBasicBlock *MBB) const;
80
81 /// incrementally calculate block frequencies when we split edges, to avoid
82 /// full CFG traversal.
83 void onEdgeSplit(const MachineBasicBlock &NewPredecessor,
84 const MachineBasicBlock &NewSuccessor,
85 const MachineBranchProbabilityInfo &MBPI);
86
87 const MachineFunction *getFunction() const;
88 const MachineBranchProbabilityInfo *getMBPI() const;
89
90 /// Pop up a ghostview window with the current block frequency propagation
91 /// rendered using dot.
92 void view(const Twine &Name, bool isSimple = true) const;
93
94 /// Divide a block's BlockFrequency::getFrequency() value by this value to
95 /// obtain the entry block - relative frequency of said block.
96 BlockFrequency getEntryFreq() const;
97};
98
99/// Print the block frequency @p Freq relative to the current functions entry
100/// frequency. Returns a Printable object that can be piped via `<<` to a
101/// `raw_ostream`.
102Printable printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
103 BlockFrequency Freq);
104
105/// Convenience function equivalent to calling
106/// `printBlockFreq(MBFI, MBFI.getBlockFreq(&MBB))`.
107Printable printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
108 const MachineBasicBlock &MBB);
109
110} // end namespace llvm
111
112#endif // LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
113

source code of llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h