1 //===- MachineBlockFrequencyInfo.cpp - MBB Frequency Analysis -------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Loops should be simplified before this analysis.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
15 #include "llvm/ADT/DenseMap.h"
16 #include "llvm/ADT/None.h"
17 #include "llvm/ADT/iterator.h"
18 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
19 #include "llvm/CodeGen/MachineBasicBlock.h"
20 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineLoopInfo.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 GVDAGType getGVDT() {
72   if (ViewBlockLayoutWithBFI != GVDT_None)
73     return ViewBlockLayoutWithBFI;
74 
75   return ViewMachineBlockFreqPropagationDAG;
76 }
77 
78 namespace llvm {
79 
80 template <> struct GraphTraits<MachineBlockFrequencyInfo *> {
81   using NodeRef = const MachineBasicBlock *;
82   using ChildIteratorType = MachineBasicBlock::const_succ_iterator;
83   using nodes_iterator = pointer_iterator<MachineFunction::const_iterator>;
84 
85   static NodeRef getEntryNode(const MachineBlockFrequencyInfo *G) {
86     return &G->getFunction()->front();
87   }
88 
89   static ChildIteratorType child_begin(const NodeRef N) {
90     return N->succ_begin();
91   }
92 
93   static ChildIteratorType child_end(const NodeRef N) { return N->succ_end(); }
94 
95   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
96     return nodes_iterator(G->getFunction()->begin());
97   }
98 
99   static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
100     return nodes_iterator(G->getFunction()->end());
101   }
102 };
103 
104 using MBFIDOTGraphTraitsBase =
105     BFIDOTGraphTraitsBase<MachineBlockFrequencyInfo,
106                           MachineBranchProbabilityInfo>;
107 
108 template <>
109 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
110     : public MBFIDOTGraphTraitsBase {
111   const MachineFunction *CurFunc = nullptr;
112   DenseMap<const MachineBasicBlock *, int> LayoutOrderMap;
113 
114   explicit DOTGraphTraits(bool isSimple = false)
115       : MBFIDOTGraphTraitsBase(isSimple) {}
116 
117   std::string getNodeLabel(const MachineBasicBlock *Node,
118                            const MachineBlockFrequencyInfo *Graph) {
119     int layout_order = -1;
120     // Attach additional ordering information if 'isSimple' is false.
121     if (!isSimple()) {
122       const MachineFunction *F = Node->getParent();
123       if (!CurFunc || F != CurFunc) {
124         if (CurFunc)
125           LayoutOrderMap.clear();
126 
127         CurFunc = F;
128         int O = 0;
129         for (auto MBI = F->begin(); MBI != F->end(); ++MBI, ++O) {
130           LayoutOrderMap[&*MBI] = O;
131         }
132       }
133       layout_order = LayoutOrderMap[Node];
134     }
135     return MBFIDOTGraphTraitsBase::getNodeLabel(Node, Graph, getGVDT(),
136                                                 layout_order);
137   }
138 
139   std::string getNodeAttributes(const MachineBasicBlock *Node,
140                                 const MachineBlockFrequencyInfo *Graph) {
141     return MBFIDOTGraphTraitsBase::getNodeAttributes(Node, Graph,
142                                                      ViewHotFreqPercent);
143   }
144 
145   std::string getEdgeAttributes(const MachineBasicBlock *Node, EdgeIter EI,
146                                 const MachineBlockFrequencyInfo *MBFI) {
147     return MBFIDOTGraphTraitsBase::getEdgeAttributes(
148         Node, EI, MBFI, MBFI->getMBPI(), ViewHotFreqPercent);
149   }
150 };
151 
152 } // end namespace llvm
153 
154 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, DEBUG_TYPE,
155                       "Machine Block Frequency Analysis", true, true)
156 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
157 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
158 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, DEBUG_TYPE,
159                     "Machine Block Frequency Analysis", true, true)
160 
161 char MachineBlockFrequencyInfo::ID = 0;
162 
163 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
164     : MachineFunctionPass(ID) {
165   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
166 }
167 
168 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() = default;
169 
170 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
171   AU.addRequired<MachineBranchProbabilityInfo>();
172   AU.addRequired<MachineLoopInfo>();
173   AU.setPreservesAll();
174   MachineFunctionPass::getAnalysisUsage(AU);
175 }
176 
177 void MachineBlockFrequencyInfo::calculate(
178     const MachineFunction &F, const MachineBranchProbabilityInfo &MBPI,
179     const MachineLoopInfo &MLI) {
180   if (!MBFI)
181     MBFI.reset(new ImplType);
182   MBFI->calculate(F, MBPI, MLI);
183   if (ViewMachineBlockFreqPropagationDAG != GVDT_None &&
184       (ViewBlockFreqFuncName.empty() ||
185        F.getName().equals(ViewBlockFreqFuncName))) {
186     view("MachineBlockFrequencyDAGS." + F.getName());
187   }
188 }
189 
190 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
191   MachineBranchProbabilityInfo &MBPI =
192       getAnalysis<MachineBranchProbabilityInfo>();
193   MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
194   calculate(F, MBPI, MLI);
195   return false;
196 }
197 
198 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
199 
200 /// Pop up a ghostview window with the current block frequency propagation
201 /// rendered using dot.
202 void MachineBlockFrequencyInfo::view(const Twine &Name, bool isSimple) const {
203   // This code is only for debugging.
204   ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this), Name, isSimple);
205 }
206 
207 BlockFrequency
208 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
209   return MBFI ? MBFI->getBlockFreq(MBB) : 0;
210 }
211 
212 Optional<uint64_t> MachineBlockFrequencyInfo::getBlockProfileCount(
213     const MachineBasicBlock *MBB) const {
214   const Function *F = MBFI->getFunction()->getFunction();
215   return MBFI ? MBFI->getBlockProfileCount(*F, MBB) : None;
216 }
217 
218 Optional<uint64_t>
219 MachineBlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
220   const Function *F = MBFI->getFunction()->getFunction();
221   return MBFI ? MBFI->getProfileCountFromFreq(*F, Freq) : None;
222 }
223 
224 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
225   return MBFI ? MBFI->getFunction() : nullptr;
226 }
227 
228 const MachineBranchProbabilityInfo *MachineBlockFrequencyInfo::getMBPI() const {
229   return MBFI ? &MBFI->getBPI() : nullptr;
230 }
231 
232 raw_ostream &
233 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
234                                           const BlockFrequency Freq) const {
235   return MBFI ? MBFI->printBlockFreq(OS, Freq) : OS;
236 }
237 
238 raw_ostream &
239 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
240                                           const MachineBasicBlock *MBB) const {
241   return MBFI ? MBFI->printBlockFreq(OS, MBB) : OS;
242 }
243 
244 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
245   return MBFI ? MBFI->getEntryFreq() : 0;
246 }
247