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/iterator.h"
16 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineLoopInfo.h"
21 #include "llvm/InitializePasses.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/GraphWriter.h"
25 #include <optional>
26 #include <string>
27
28 using namespace llvm;
29
30 #define DEBUG_TYPE "machine-block-freq"
31
32 namespace llvm {
33 static cl::opt<GVDAGType> ViewMachineBlockFreqPropagationDAG(
34 "view-machine-block-freq-propagation-dags", cl::Hidden,
35 cl::desc("Pop up a window to show a dag displaying how machine block "
36 "frequencies propagate through the CFG."),
37 cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
38 clEnumValN(GVDT_Fraction, "fraction",
39 "display a graph using the "
40 "fractional block frequency representation."),
41 clEnumValN(GVDT_Integer, "integer",
42 "display a graph using the raw "
43 "integer fractional block frequency representation."),
44 clEnumValN(GVDT_Count, "count", "display a graph using the real "
45 "profile count if available.")));
46
47 // Similar option above, but used to control BFI display only after MBP pass
48 cl::opt<GVDAGType> ViewBlockLayoutWithBFI(
49 "view-block-layout-with-bfi", cl::Hidden,
50 cl::desc(
51 "Pop up a window to show a dag displaying MBP layout and associated "
52 "block frequencies of the CFG."),
53 cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
54 clEnumValN(GVDT_Fraction, "fraction",
55 "display a graph using the "
56 "fractional block frequency representation."),
57 clEnumValN(GVDT_Integer, "integer",
58 "display a graph using the raw "
59 "integer fractional block frequency representation."),
60 clEnumValN(GVDT_Count, "count",
61 "display a graph using the real "
62 "profile count if available.")));
63
64 // Command line option to specify the name of the function for CFG dump
65 // Defined in Analysis/BlockFrequencyInfo.cpp: -view-bfi-func-name=
66 extern cl::opt<std::string> ViewBlockFreqFuncName;
67
68 // Command line option to specify hot frequency threshold.
69 // Defined in Analysis/BlockFrequencyInfo.cpp: -view-hot-freq-perc=
70 extern cl::opt<unsigned> ViewHotFreqPercent;
71
72 static cl::opt<bool> PrintMachineBlockFreq(
73 "print-machine-bfi", cl::init(false), cl::Hidden,
74 cl::desc("Print the machine block frequency info."));
75
76 // Command line option to specify the name of the function for block frequency
77 // dump. Defined in Analysis/BlockFrequencyInfo.cpp.
78 extern cl::opt<std::string> PrintBlockFreqFuncName;
79 } // namespace llvm
80
getGVDT()81 static GVDAGType getGVDT() {
82 if (ViewBlockLayoutWithBFI != GVDT_None)
83 return ViewBlockLayoutWithBFI;
84
85 return ViewMachineBlockFreqPropagationDAG;
86 }
87
88 namespace llvm {
89
90 template <> struct GraphTraits<MachineBlockFrequencyInfo *> {
91 using NodeRef = const MachineBasicBlock *;
92 using ChildIteratorType = MachineBasicBlock::const_succ_iterator;
93 using nodes_iterator = pointer_iterator<MachineFunction::const_iterator>;
94
getEntryNodellvm::GraphTraits95 static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
96 return &G->getFunction()->front();
97 }
98
child_beginllvm::GraphTraits99 static ChildIteratorType child_begin(const NodeRef N) {
100 return N->succ_begin();
101 }
102
child_endllvm::GraphTraits103 static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
104
nodes_beginllvm::GraphTraits105 static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
106 return nodes_iterator(G->getFunction()->begin());
107 }
108
nodes_endllvm::GraphTraits109 static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
110 return nodes_iterator(G->getFunction()->end());
111 }
112 };
113
114 using MBFIDOTGraphTraitsBase =
115 BFIDOTGraphTraitsBase<MachineBlockFrequencyInfo,
116 MachineBranchProbabilityInfo>;
117
118 template <>
119 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
120 : public MBFIDOTGraphTraitsBase {
121 const MachineFunction *CurFunc = nullptr;
122 DenseMap<const MachineBasicBlock *, int> LayoutOrderMap;
123
DOTGraphTraitsllvm::DOTGraphTraits124 explicit DOTGraphTraits(bool isSimple = false)
125 : MBFIDOTGraphTraitsBase(isSimple) {}
126
getNodeLabelllvm::DOTGraphTraits127 std::string getNodeLabel(const MachineBasicBlock *Node,
128 const MachineBlockFrequencyInfo *Graph) {
129 int layout_order = -1;
130 // Attach additional ordering information if 'isSimple' is false.
131 if (!isSimple()) {
132 const MachineFunction *F = Node->getParent();
133 if (!CurFunc || F != CurFunc) {
134 if (CurFunc)
135 LayoutOrderMap.clear();
136
137 CurFunc = F;
138 int O = 0;
139 for (auto MBI = F->begin(); MBI != F->end(); ++MBI, ++O) {
140 LayoutOrderMap[&*MBI] = O;
141 }
142 }
143 layout_order = LayoutOrderMap[Node];
144 }
145 return MBFIDOTGraphTraitsBase::getNodeLabel(Node, Graph, getGVDT(),
146 layout_order);
147 }
148
getNodeAttributesllvm::DOTGraphTraits149 std::string getNodeAttributes(const MachineBasicBlock *Node,
150 const MachineBlockFrequencyInfo *Graph) {
151 return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
152 ViewHotFreqPercent);
153 }
154
getEdgeAttributesllvm::DOTGraphTraits155 std::string getEdgeAttributes(const MachineBasicBlock *Node, EdgeIter EI,
156 const MachineBlockFrequencyInfo *MBFI) {
157 return MBFIDOTGraphTraitsBase::getEdgeAttributes(
158 Node, EI, MBFI, MBFI->getMBPI(), ViewHotFreqPercent);
159 }
160 };
161
162 } // end namespace llvm
163
164 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, DEBUG_TYPE,
165 "Machine Block Frequency Analysis", true, true)
166 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
167 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
168 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, DEBUG_TYPE,
169 "Machine Block Frequency Analysis", true, true)
170
171 char MachineBlockFrequencyInfo::ID = 0;
172
MachineBlockFrequencyInfo()173 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
174 : MachineFunctionPass(ID) {
175 initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
176 }
177
MachineBlockFrequencyInfo(MachineFunction & F,MachineBranchProbabilityInfo & MBPI,MachineLoopInfo & MLI)178 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo(
179 MachineFunction &F,
180 MachineBranchProbabilityInfo &MBPI,
181 MachineLoopInfo &MLI) : MachineFunctionPass(ID) {
182 calculate(F, MBPI, MLI);
183 }
184
185 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() = default;
186
getAnalysisUsage(AnalysisUsage & AU) const187 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
188 AU.addRequired<MachineBranchProbabilityInfo>();
189 AU.addRequired<MachineLoopInfo>();
190 AU.setPreservesAll();
191 MachineFunctionPass::getAnalysisUsage(AU);
192 }
193
calculate(const MachineFunction & F,const MachineBranchProbabilityInfo & MBPI,const MachineLoopInfo & MLI)194 void MachineBlockFrequencyInfo::calculate(
195 const MachineFunction &F, const MachineBranchProbabilityInfo &MBPI,
196 const MachineLoopInfo &MLI) {
197 if (!MBFI)
198 MBFI.reset(new ImplType);
199 MBFI->calculate(F, MBPI, MLI);
200 if (ViewMachineBlockFreqPropagationDAG != GVDT_None &&
201 (ViewBlockFreqFuncName.empty() ||
202 F.getName().equals(ViewBlockFreqFuncName))) {
203 view("MachineBlockFrequencyDAGS." + F.getName());
204 }
205 if (PrintMachineBlockFreq &&
206 (PrintBlockFreqFuncName.empty() ||
207 F.getName().equals(PrintBlockFreqFuncName))) {
208 MBFI->print(dbgs());
209 }
210 }
211
runOnMachineFunction(MachineFunction & F)212 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
213 MachineBranchProbabilityInfo &MBPI =
214 getAnalysis<MachineBranchProbabilityInfo>();
215 MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
216 calculate(F, MBPI, MLI);
217 return false;
218 }
219
releaseMemory()220 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
221
222 /// Pop up a ghostview window with the current block frequency propagation
223 /// rendered using dot.
view(const Twine & Name,bool isSimple) const224 void MachineBlockFrequencyInfo::view(const Twine &Name, bool isSimple) const {
225 // This code is only for debugging.
226 ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this), Name, isSimple);
227 }
228
229 BlockFrequency
getBlockFreq(const MachineBasicBlock * MBB) const230 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
231 return MBFI ? MBFI->getBlockFreq(MBB) : 0;
232 }
233
getBlockProfileCount(const MachineBasicBlock * MBB) const234 std::optional<uint64_t> MachineBlockFrequencyInfo::getBlockProfileCount(
235 const MachineBasicBlock *MBB) const {
236 if (!MBFI)
237 return std::nullopt;
238
239 const Function &F = MBFI->getFunction()->getFunction();
240 return MBFI->getBlockProfileCount(F, MBB);
241 }
242
243 std::optional<uint64_t>
getProfileCountFromFreq(uint64_t Freq) const244 MachineBlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
245 if (!MBFI)
246 return std::nullopt;
247
248 const Function &F = MBFI->getFunction()->getFunction();
249 return MBFI->getProfileCountFromFreq(F, Freq);
250 }
251
isIrrLoopHeader(const MachineBasicBlock * MBB) const252 bool MachineBlockFrequencyInfo::isIrrLoopHeader(
253 const MachineBasicBlock *MBB) const {
254 assert(MBFI && "Expected analysis to be available");
255 return MBFI->isIrrLoopHeader(MBB);
256 }
257
onEdgeSplit(const MachineBasicBlock & NewPredecessor,const MachineBasicBlock & NewSuccessor,const MachineBranchProbabilityInfo & MBPI)258 void MachineBlockFrequencyInfo::onEdgeSplit(
259 const MachineBasicBlock &NewPredecessor,
260 const MachineBasicBlock &NewSuccessor,
261 const MachineBranchProbabilityInfo &MBPI) {
262 assert(MBFI && "Expected analysis to be available");
263 auto NewSuccFreq = MBFI->getBlockFreq(&NewPredecessor) *
264 MBPI.getEdgeProbability(&NewPredecessor, &NewSuccessor);
265
266 MBFI->setBlockFreq(&NewSuccessor, NewSuccFreq.getFrequency());
267 }
268
getFunction() const269 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
270 return MBFI ? MBFI->getFunction() : nullptr;
271 }
272
getMBPI() const273 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
274 return MBFI ? &MBFI->getBPI() : nullptr;
275 }
276
277 raw_ostream &
printBlockFreq(raw_ostream & OS,const BlockFrequency Freq) const278 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
279 const BlockFrequency Freq) const {
280 return MBFI ? MBFI->printBlockFreq(OS, Freq) : OS;
281 }
282
283 raw_ostream &
printBlockFreq(raw_ostream & OS,const MachineBasicBlock * MBB) const284 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
285 const MachineBasicBlock *MBB) const {
286 return MBFI ? MBFI->printBlockFreq(OS, MBB) : OS;
287 }
288
getEntryFreq() const289 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
290 return MBFI ? MBFI->getEntryFreq() : 0;
291 }
292