1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
|
//===- StaticDataSplitter.cpp ---------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// The pass uses branch profile data to assign hotness based section qualifiers
// for the following types of static data:
// - Jump tables
// - Constant pools (TODO)
// - Other module-internal data (TODO)
//
// For the original RFC of this pass please see
// https://discourse.llvm.org/t/rfc-profile-guided-static-data-partitioning/83744
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/CodeGen/MBFIWrapper.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
#define DEBUG_TYPE "static-data-splitter"
STATISTIC(NumHotJumpTables, "Number of hot jump tables seen.");
STATISTIC(NumColdJumpTables, "Number of cold jump tables seen.");
STATISTIC(NumUnknownJumpTables,
"Number of jump tables with unknown hotness. They are from functions "
"without profile information.");
class StaticDataSplitter : public MachineFunctionPass {
const MachineBranchProbabilityInfo *MBPI = nullptr;
const MachineBlockFrequencyInfo *MBFI = nullptr;
const ProfileSummaryInfo *PSI = nullptr;
// Update LLVM statistics for a machine function without profiles.
void updateStatsWithoutProfiles(const MachineFunction &MF);
// Update LLVM statistics for a machine function with profiles.
void updateStatsWithProfiles(const MachineFunction &MF);
// Use profiles to partition static data.
bool partitionStaticDataWithProfiles(MachineFunction &MF);
public:
static char ID;
StaticDataSplitter() : MachineFunctionPass(ID) {
initializeStaticDataSplitterPass(*PassRegistry::getPassRegistry());
}
StringRef getPassName() const override { return "Static Data Splitter"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
MachineFunctionPass::getAnalysisUsage(AU);
AU.addRequired<MachineBranchProbabilityInfoWrapperPass>();
AU.addRequired<MachineBlockFrequencyInfoWrapperPass>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
}
bool runOnMachineFunction(MachineFunction &MF) override;
};
bool StaticDataSplitter::runOnMachineFunction(MachineFunction &MF) {
MBPI = &getAnalysis<MachineBranchProbabilityInfoWrapperPass>().getMBPI();
MBFI = &getAnalysis<MachineBlockFrequencyInfoWrapperPass>().getMBFI();
PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
const bool ProfileAvailable = PSI && PSI->hasProfileSummary() && MBFI &&
MF.getFunction().hasProfileData();
if (!ProfileAvailable) {
updateStatsWithoutProfiles(MF);
return false;
}
bool Changed = partitionStaticDataWithProfiles(MF);
updateStatsWithProfiles(MF);
return Changed;
}
bool StaticDataSplitter::partitionStaticDataWithProfiles(MachineFunction &MF) {
int NumChangedJumpTables = 0;
MachineJumpTableInfo *MJTI = MF.getJumpTableInfo();
// Jump table could be used by either terminating instructions or
// non-terminating ones, so we walk all instructions and use
// `MachineOperand::isJTI()` to identify jump table operands.
// Similarly, `MachineOperand::isCPI()` can identify constant pool usages
// in the same loop.
for (const auto &MBB : MF) {
for (const MachineInstr &I : MBB) {
for (const MachineOperand &Op : I.operands()) {
if (Op.isJTI()) {
assert(MJTI != nullptr && "Jump table info is not available.");
const int JTI = Op.getIndex();
// This is not a source block of jump table.
if (JTI == -1)
continue;
auto Hotness = MachineFunctionDataHotness::Hot;
// Hotness is based on source basic block hotness.
// TODO: PSI APIs are about instruction hotness. Introduce API for
// data access hotness.
if (PSI->isColdBlock(&MBB, MBFI))
Hotness = MachineFunctionDataHotness::Cold;
if (MJTI->updateJumpTableEntryHotness(JTI, Hotness))
++NumChangedJumpTables;
}
}
}
}
return NumChangedJumpTables > 0;
}
void StaticDataSplitter::updateStatsWithProfiles(const MachineFunction &MF) {
if (!AreStatisticsEnabled())
return;
if (const MachineJumpTableInfo *MJTI = MF.getJumpTableInfo()) {
for (const auto &JumpTable : MJTI->getJumpTables()) {
if (JumpTable.Hotness == MachineFunctionDataHotness::Hot) {
++NumHotJumpTables;
} else {
assert(JumpTable.Hotness == MachineFunctionDataHotness::Cold &&
"A jump table is either hot or cold when profile information is "
"available.");
++NumColdJumpTables;
}
}
}
}
void StaticDataSplitter::updateStatsWithoutProfiles(const MachineFunction &MF) {
if (!AreStatisticsEnabled())
return;
if (const MachineJumpTableInfo *MJTI = MF.getJumpTableInfo()) {
NumUnknownJumpTables += MJTI->getJumpTables().size();
}
}
char StaticDataSplitter::ID = 0;
INITIALIZE_PASS_BEGIN(StaticDataSplitter, DEBUG_TYPE, "Split static data",
false, false)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_END(StaticDataSplitter, DEBUG_TYPE, "Split static data", false,
false)
MachineFunctionPass *llvm::createStaticDataSplitterPass() {
return new StaticDataSplitter();
}
|
