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> PrintBFIFuncName;
79 } // namespace llvm
80 
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 
95   static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
96     return &G->getFunction()->front();
97   }
98 
99   static ChildIteratorType child_begin(const NodeRef N) {
100     return N->succ_begin();
101   }
102 
103   static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
104 
105   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
106     return nodes_iterator(G->getFunction()->begin());
107   }
108 
109   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 
124   explicit DOTGraphTraits(bool isSimple = false)
125       : MBFIDOTGraphTraitsBase(isSimple) {}
126 
127   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 
149   std::string getNodeAttributes(const MachineBasicBlock *Node,
150                                 const MachineBlockFrequencyInfo *Graph) {
151     return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
152                                                      ViewHotFreqPercent);
153   }
154 
155   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 
173 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
174     : MachineFunctionPass(ID) {
175   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
176 }
177 
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 
187 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
188   AU.addRequired<MachineBranchProbabilityInfo>();
189   AU.addRequired<MachineLoopInfo>();
190   AU.setPreservesAll();
191   MachineFunctionPass::getAnalysisUsage(AU);
192 }
193 
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       (PrintBFIFuncName.empty() || F.getName().equals(PrintBFIFuncName))) {
207     MBFI->print(dbgs());
208   }
209 }
210 
211 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
212   MachineBranchProbabilityInfo &MBPI =
213       getAnalysis<MachineBranchProbabilityInfo>();
214   MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
215   calculate(F, MBPI, MLI);
216   return false;
217 }
218 
219 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
220 
221 /// Pop up a ghostview window with the current block frequency propagation
222 /// rendered using dot.
223 void MachineBlockFrequencyInfo::view(const Twine &Name, bool isSimple) const {
224   // This code is only for debugging.
225   ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this), Name, isSimple);
226 }
227 
228 BlockFrequency
229 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
230   return MBFI ? MBFI->getBlockFreq(MBB) : BlockFrequency(0);
231 }
232 
233 std::optional<uint64_t> MachineBlockFrequencyInfo::getBlockProfileCount(
234     const MachineBasicBlock *MBB) const {
235   if (!MBFI)
236     return std::nullopt;
237 
238   const Function &F = MBFI->getFunction()->getFunction();
239   return MBFI->getBlockProfileCount(F, MBB);
240 }
241 
242 std::optional<uint64_t>
243 MachineBlockFrequencyInfo::getProfileCountFromFreq(BlockFrequency Freq) const {
244   if (!MBFI)
245     return std::nullopt;
246 
247   const Function &F = MBFI->getFunction()->getFunction();
248   return MBFI->getProfileCountFromFreq(F, Freq);
249 }
250 
251 bool MachineBlockFrequencyInfo::isIrrLoopHeader(
252     const MachineBasicBlock *MBB) const {
253   assert(MBFI && "Expected analysis to be available");
254   return MBFI->isIrrLoopHeader(MBB);
255 }
256 
257 void MachineBlockFrequencyInfo::onEdgeSplit(
258     const MachineBasicBlock &NewPredecessor,
259     const MachineBasicBlock &NewSuccessor,
260     const MachineBranchProbabilityInfo &MBPI) {
261   assert(MBFI && "Expected analysis to be available");
262   auto NewSuccFreq = MBFI->getBlockFreq(&NewPredecessor) *
263                      MBPI.getEdgeProbability(&NewPredecessor, &NewSuccessor);
264 
265   MBFI->setBlockFreq(&NewSuccessor, NewSuccFreq);
266 }
267 
268 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
269   return MBFI ? MBFI->getFunction() : nullptr;
270 }
271 
272 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
273   return MBFI ? &MBFI->getBPI() : nullptr;
274 }
275 
276 BlockFrequency MachineBlockFrequencyInfo::getEntryFreq() const {
277   return MBFI ? MBFI->getEntryFreq() : BlockFrequency(0);
278 }
279 
280 Printable llvm::printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
281                                BlockFrequency Freq) {
282   return Printable([&MBFI, Freq](raw_ostream &OS) {
283     printBlockFreqImpl(OS, MBFI.getEntryFreq(), Freq);
284   });
285 }
286 
287 Printable llvm::printBlockFreq(const MachineBlockFrequencyInfo &MBFI,
288                                const MachineBasicBlock &MBB) {
289   return printBlockFreq(MBFI, MBFI.getBlockFreq(&MBB));
290 }
291