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 
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 
93   static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
94     return &G->getFunction()->front();
95   }
96 
97   static ChildIteratorType child_begin(const NodeRef N) {
98     return N->succ_begin();
99   }
100 
101   static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
102 
103   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
104     return nodes_iterator(G->getFunction()->begin());
105   }
106 
107   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 
122   explicit DOTGraphTraits(bool isSimple = false)
123       : MBFIDOTGraphTraitsBase(isSimple) {}
124 
125   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 
147   std::string getNodeAttributes(const MachineBasicBlock *Node,
148                                 const MachineBlockFrequencyInfo *Graph) {
149     return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
150                                                      ViewHotFreqPercent);
151   }
152 
153   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 
171 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
172     : MachineFunctionPass(ID) {
173   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
174 }
175 
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 
185 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
186   AU.addRequired<MachineBranchProbabilityInfo>();
187   AU.addRequired<MachineLoopInfo>();
188   AU.setPreservesAll();
189   MachineFunctionPass::getAnalysisUsage(AU);
190 }
191 
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 
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 
218 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
219 
220 /// Pop up a ghostview window with the current block frequency propagation
221 /// rendered using dot.
222 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
228 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
229   return MBFI ? MBFI->getBlockFreq(MBB) : 0;
230 }
231 
232 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>
239 MachineBlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
240   const Function &F = MBFI->getFunction()->getFunction();
241   return MBFI ? MBFI->getProfileCountFromFreq(F, Freq) : None;
242 }
243 
244 bool
245 MachineBlockFrequencyInfo::isIrrLoopHeader(const MachineBasicBlock *MBB) {
246   assert(MBFI && "Expected analysis to be available");
247   return MBFI->isIrrLoopHeader(MBB);
248 }
249 
250 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
251   return MBFI ? MBFI->getFunction() : nullptr;
252 }
253 
254 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
255   return MBFI ? &MBFI->getBPI() : nullptr;
256 }
257 
258 raw_ostream &
259 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
260                                           const BlockFrequency Freq) const {
261   return MBFI ? MBFI->printBlockFreq(OS, Freq) : OS;
262 }
263 
264 raw_ostream &
265 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
266                                           const MachineBasicBlock *MBB) const {
267   return MBFI ? MBFI->printBlockFreq(OS, MBB) : OS;
268 }
269 
270 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
271   return MBFI ? MBFI->getEntryFreq() : 0;
272 }
273