1 //===- MachineBlockFrequencyInfo.cpp - MBB Frequency Analysis -------------===//
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 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/None.h"
16 #include "llvm/ADT/iterator.h"
17 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
18 #include "llvm/CodeGen/MachineBasicBlock.h"
19 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineLoopInfo.h"
22 #include "llvm/InitializePasses.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/GraphWriter.h"
26 #include <string>
27
28 using namespace llvm;
29
30 #define DEBUG_TYPE "machine-block-freq"
31
32 static cl::opt<GVDAGType> ViewMachineBlockFreqPropagationDAG(
33 "view-machine-block-freq-propagation-dags", cl::Hidden,
34 cl::desc("Pop up a window to show a dag displaying how machine block "
35 "frequencies propagate through the CFG."),
36 cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
37 clEnumValN(GVDT_Fraction, "fraction",
38 "display a graph using the "
39 "fractional block frequency representation."),
40 clEnumValN(GVDT_Integer, "integer",
41 "display a graph using the raw "
42 "integer fractional block frequency representation."),
43 clEnumValN(GVDT_Count, "count", "display a graph using the real "
44 "profile count if available.")));
45
46 // Similar option above, but used to control BFI display only after MBP pass
47 cl::opt<GVDAGType> ViewBlockLayoutWithBFI(
48 "view-block-layout-with-bfi", cl::Hidden,
49 cl::desc(
50 "Pop up a window to show a dag displaying MBP layout and associated "
51 "block frequencies of the CFG."),
52 cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
53 clEnumValN(GVDT_Fraction, "fraction",
54 "display a graph using the "
55 "fractional block frequency representation."),
56 clEnumValN(GVDT_Integer, "integer",
57 "display a graph using the raw "
58 "integer fractional block frequency representation."),
59 clEnumValN(GVDT_Count, "count",
60 "display a graph using the real "
61 "profile count if available.")));
62
63 // Command line option to specify the name of the function for CFG dump
64 // Defined in Analysis/BlockFrequencyInfo.cpp: -view-bfi-func-name=
65 extern cl::opt<std::string> ViewBlockFreqFuncName;
66
67 // Command line option to specify hot frequency threshold.
68 // Defined in Analysis/BlockFrequencyInfo.cpp: -view-hot-freq-perc=
69 extern cl::opt<unsigned> ViewHotFreqPercent;
70
71 static cl::opt<bool> PrintMachineBlockFreq(
72 "print-machine-bfi", cl::init(false), cl::Hidden,
73 cl::desc("Print the machine block frequency info."));
74
75 // Command line option to specify the name of the function for block frequency
76 // dump. Defined in Analysis/BlockFrequencyInfo.cpp.
77 extern cl::opt<std::string> PrintBlockFreqFuncName;
78
getGVDT()79 static GVDAGType getGVDT() {
80 if (ViewBlockLayoutWithBFI != GVDT_None)
81 return ViewBlockLayoutWithBFI;
82
83 return ViewMachineBlockFreqPropagationDAG;
84 }
85
86 namespace llvm {
87
88 template <> struct GraphTraits<MachineBlockFrequencyInfo *> {
89 using NodeRef = const MachineBasicBlock *;
90 using ChildIteratorType = MachineBasicBlock::const_succ_iterator;
91 using nodes_iterator = pointer_iterator<MachineFunction::const_iterator>;
92
getEntryNodellvm::GraphTraits93 static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
94 return &G->getFunction()->front();
95 }
96
child_beginllvm::GraphTraits97 static ChildIteratorType child_begin(const NodeRef N) {
98 return N->succ_begin();
99 }
100
child_endllvm::GraphTraits101 static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
102
nodes_beginllvm::GraphTraits103 static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
104 return nodes_iterator(G->getFunction()->begin());
105 }
106
nodes_endllvm::GraphTraits107 static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
108 return nodes_iterator(G->getFunction()->end());
109 }
110 };
111
112 using MBFIDOTGraphTraitsBase =
113 BFIDOTGraphTraitsBase<MachineBlockFrequencyInfo,
114 MachineBranchProbabilityInfo>;
115
116 template <>
117 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
118 : public MBFIDOTGraphTraitsBase {
119 const MachineFunction *CurFunc = nullptr;
120 DenseMap<const MachineBasicBlock *, int> LayoutOrderMap;
121
DOTGraphTraitsllvm::DOTGraphTraits122 explicit DOTGraphTraits(bool isSimple = false)
123 : MBFIDOTGraphTraitsBase(isSimple) {}
124
getNodeLabelllvm::DOTGraphTraits125 std::string getNodeLabel(const MachineBasicBlock *Node,
126 const MachineBlockFrequencyInfo *Graph) {
127 int layout_order = -1;
128 // Attach additional ordering information if 'isSimple' is false.
129 if (!isSimple()) {
130 const MachineFunction *F = Node->getParent();
131 if (!CurFunc || F != CurFunc) {
132 if (CurFunc)
133 LayoutOrderMap.clear();
134
135 CurFunc = F;
136 int O = 0;
137 for (auto MBI = F->begin(); MBI != F->end(); ++MBI, ++O) {
138 LayoutOrderMap[&*MBI] = O;
139 }
140 }
141 layout_order = LayoutOrderMap[Node];
142 }
143 return MBFIDOTGraphTraitsBase::getNodeLabel(Node, Graph, getGVDT(),
144 layout_order);
145 }
146
getNodeAttributesllvm::DOTGraphTraits147 std::string getNodeAttributes(const MachineBasicBlock *Node,
148 const MachineBlockFrequencyInfo *Graph) {
149 return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
150 ViewHotFreqPercent);
151 }
152
getEdgeAttributesllvm::DOTGraphTraits153 std::string getEdgeAttributes(const MachineBasicBlock *Node, EdgeIter EI,
154 const MachineBlockFrequencyInfo *MBFI) {
155 return MBFIDOTGraphTraitsBase::getEdgeAttributes(
156 Node, EI, MBFI, MBFI->getMBPI(), ViewHotFreqPercent);
157 }
158 };
159
160 } // end namespace llvm
161
162 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, DEBUG_TYPE,
163 "Machine Block Frequency Analysis", true, true)
164 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
165 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
166 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, DEBUG_TYPE,
167 "Machine Block Frequency Analysis", true, true)
168
169 char MachineBlockFrequencyInfo::ID = 0;
170
MachineBlockFrequencyInfo()171 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
172 : MachineFunctionPass(ID) {
173 initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
174 }
175
MachineBlockFrequencyInfo(MachineFunction & F,MachineBranchProbabilityInfo & MBPI,MachineLoopInfo & MLI)176 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo(
177 MachineFunction &F,
178 MachineBranchProbabilityInfo &MBPI,
179 MachineLoopInfo &MLI) : MachineFunctionPass(ID) {
180 calculate(F, MBPI, MLI);
181 }
182
183 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() = default;
184
getAnalysisUsage(AnalysisUsage & AU) const185 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
186 AU.addRequired<MachineBranchProbabilityInfo>();
187 AU.addRequired<MachineLoopInfo>();
188 AU.setPreservesAll();
189 MachineFunctionPass::getAnalysisUsage(AU);
190 }
191
calculate(const MachineFunction & F,const MachineBranchProbabilityInfo & MBPI,const MachineLoopInfo & MLI)192 void MachineBlockFrequencyInfo::calculate(
193 const MachineFunction &F, const MachineBranchProbabilityInfo &MBPI,
194 const MachineLoopInfo &MLI) {
195 if (!MBFI)
196 MBFI.reset(new ImplType);
197 MBFI->calculate(F, MBPI, MLI);
198 if (ViewMachineBlockFreqPropagationDAG != GVDT_None &&
199 (ViewBlockFreqFuncName.empty() ||
200 F.getName().equals(ViewBlockFreqFuncName))) {
201 view("MachineBlockFrequencyDAGS." + F.getName());
202 }
203 if (PrintMachineBlockFreq &&
204 (PrintBlockFreqFuncName.empty() ||
205 F.getName().equals(PrintBlockFreqFuncName))) {
206 MBFI->print(dbgs());
207 }
208 }
209
runOnMachineFunction(MachineFunction & F)210 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
211 MachineBranchProbabilityInfo &MBPI =
212 getAnalysis<MachineBranchProbabilityInfo>();
213 MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
214 calculate(F, MBPI, MLI);
215 return false;
216 }
217
releaseMemory()218 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
219
220 /// Pop up a ghostview window with the current block frequency propagation
221 /// rendered using dot.
view(const Twine & Name,bool isSimple) const222 void MachineBlockFrequencyInfo::view(const Twine &Name, bool isSimple) const {
223 // This code is only for debugging.
224 ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this), Name, isSimple);
225 }
226
227 BlockFrequency
getBlockFreq(const MachineBasicBlock * MBB) const228 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
229 return MBFI ? MBFI->getBlockFreq(MBB) : 0;
230 }
231
getBlockProfileCount(const MachineBasicBlock * MBB) const232 Optional<uint64_t> MachineBlockFrequencyInfo::getBlockProfileCount(
233 const MachineBasicBlock *MBB) const {
234 const Function &F = MBFI->getFunction()->getFunction();
235 return MBFI ? MBFI->getBlockProfileCount(F, MBB) : None;
236 }
237
238 Optional<uint64_t>
getProfileCountFromFreq(uint64_t Freq) const239 MachineBlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
240 const Function &F = MBFI->getFunction()->getFunction();
241 return MBFI ? MBFI->getProfileCountFromFreq(F, Freq) : None;
242 }
243
isIrrLoopHeader(const MachineBasicBlock * MBB) const244 bool MachineBlockFrequencyInfo::isIrrLoopHeader(
245 const MachineBasicBlock *MBB) const {
246 assert(MBFI && "Expected analysis to be available");
247 return MBFI->isIrrLoopHeader(MBB);
248 }
249
onEdgeSplit(const MachineBasicBlock & NewPredecessor,const MachineBasicBlock & NewSuccessor,const MachineBranchProbabilityInfo & MBPI)250 void MachineBlockFrequencyInfo::onEdgeSplit(
251 const MachineBasicBlock &NewPredecessor,
252 const MachineBasicBlock &NewSuccessor,
253 const MachineBranchProbabilityInfo &MBPI) {
254 assert(MBFI && "Expected analysis to be available");
255 auto NewSuccFreq = MBFI->getBlockFreq(&NewPredecessor) *
256 MBPI.getEdgeProbability(&NewPredecessor, &NewSuccessor);
257
258 MBFI->setBlockFreq(&NewSuccessor, NewSuccFreq.getFrequency());
259 }
260
getFunction() const261 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
262 return MBFI ? MBFI->getFunction() : nullptr;
263 }
264
getMBPI() const265 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
266 return MBFI ? &MBFI->getBPI() : nullptr;
267 }
268
269 raw_ostream &
printBlockFreq(raw_ostream & OS,const BlockFrequency Freq) const270 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
271 const BlockFrequency Freq) const {
272 return MBFI ? MBFI->printBlockFreq(OS, Freq) : OS;
273 }
274
275 raw_ostream &
printBlockFreq(raw_ostream & OS,const MachineBasicBlock * MBB) const276 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
277 const MachineBasicBlock *MBB) const {
278 return MBFI ? MBFI->printBlockFreq(OS, MBB) : OS;
279 }
280
getEntryFreq() const281 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
282 return MBFI ? MBFI->getEntryFreq() : 0;
283 }
284