1 //===- BlockFrequencyInfo.cpp - Block 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/Analysis/BlockFrequencyInfo.h"
15 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
16 #include "llvm/Analysis/BranchProbabilityInfo.h"
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/Analysis/Passes.h"
19 #include "llvm/IR/CFG.h"
20 #include "llvm/InitializePasses.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/GraphWriter.h"
24 
25 using namespace llvm;
26 
27 #define DEBUG_TYPE "block-freq"
28 
29 #ifndef NDEBUG
30 static cl::opt<GVDAGType> ViewBlockFreqPropagationDAG(
31     "view-block-freq-propagation-dags", cl::Hidden,
32     cl::desc("Pop up a window to show a dag displaying how block "
33              "frequencies propagation through the CFG."),
34     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
35                clEnumValN(GVDT_Fraction, "fraction",
36                           "display a graph using the "
37                           "fractional block frequency representation."),
38                clEnumValN(GVDT_Integer, "integer",
39                           "display a graph using the raw "
40                           "integer fractional block frequency representation."),
41                clEnumValN(GVDT_Count, "count", "display a graph using the real "
42                                                "profile count if available."),
43                clEnumValEnd));
44 
45 cl::opt<std::string>
46     ViewBlockFreqFuncName("view-bfi-func-name", cl::Hidden,
47                           cl::desc("The option to specify "
48                                    "the name of the function "
49                                    "whose CFG will be displayed."));
50 
51 cl::opt<unsigned>
52     ViewHotFreqPercent("view-hot-freq-percent", cl::init(10), cl::Hidden,
53                        cl::desc("An integer in percent used to specify "
54                                 "the hot blocks/edges to be displayed "
55                                 "in red: a block or edge whose frequency "
56                                 "is no less than the max frequency of the "
57                                 "function multiplied by this percent."));
58 
59 namespace llvm {
60 
61 template <>
62 struct GraphTraits<BlockFrequencyInfo *> {
63   typedef const BasicBlock NodeType;
64   typedef succ_const_iterator ChildIteratorType;
65   typedef Function::const_iterator nodes_iterator;
66 
67   static inline const NodeType *getEntryNode(const BlockFrequencyInfo *G) {
68     return &G->getFunction()->front();
69   }
70   static ChildIteratorType child_begin(const NodeType *N) {
71     return succ_begin(N);
72   }
73   static ChildIteratorType child_end(const NodeType *N) {
74     return succ_end(N);
75   }
76   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
77     return G->getFunction()->begin();
78   }
79   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
80     return G->getFunction()->end();
81   }
82 };
83 
84 typedef BFIDOTGraphTraitsBase<BlockFrequencyInfo, BranchProbabilityInfo>
85     BFIDOTGTraitsBase;
86 
87 template <>
88 struct DOTGraphTraits<BlockFrequencyInfo *> : public BFIDOTGTraitsBase {
89   explicit DOTGraphTraits(bool isSimple = false)
90       : BFIDOTGTraitsBase(isSimple) {}
91 
92   std::string getNodeLabel(const BasicBlock *Node,
93                            const BlockFrequencyInfo *Graph) {
94 
95     return BFIDOTGTraitsBase::getNodeLabel(Node, Graph,
96                                            ViewBlockFreqPropagationDAG);
97   }
98 
99   std::string getNodeAttributes(const BasicBlock *Node,
100                                 const BlockFrequencyInfo *Graph) {
101     return BFIDOTGTraitsBase::getNodeAttributes(Node, Graph,
102                                                 ViewHotFreqPercent);
103   }
104 
105   std::string getEdgeAttributes(const BasicBlock *Node, EdgeIter EI,
106                                 const BlockFrequencyInfo *BFI) {
107     return BFIDOTGTraitsBase::getEdgeAttributes(Node, EI, BFI, BFI->getBPI(),
108                                                 ViewHotFreqPercent);
109   }
110 };
111 
112 } // end namespace llvm
113 #endif
114 
115 BlockFrequencyInfo::BlockFrequencyInfo() {}
116 
117 BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
118                                        const BranchProbabilityInfo &BPI,
119                                        const LoopInfo &LI) {
120   calculate(F, BPI, LI);
121 }
122 
123 BlockFrequencyInfo::BlockFrequencyInfo(BlockFrequencyInfo &&Arg)
124     : BFI(std::move(Arg.BFI)) {}
125 
126 BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
127   releaseMemory();
128   BFI = std::move(RHS.BFI);
129   return *this;
130 }
131 
132 void BlockFrequencyInfo::calculate(const Function &F,
133                                    const BranchProbabilityInfo &BPI,
134                                    const LoopInfo &LI) {
135   if (!BFI)
136     BFI.reset(new ImplType);
137   BFI->calculate(F, BPI, LI);
138 #ifndef NDEBUG
139   if (ViewBlockFreqPropagationDAG != GVDT_None &&
140       (ViewBlockFreqFuncName.empty() ||
141        F.getName().equals(ViewBlockFreqFuncName))) {
142     view();
143   }
144 #endif
145 }
146 
147 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
148   return BFI ? BFI->getBlockFreq(BB) : 0;
149 }
150 
151 Optional<uint64_t>
152 BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB) const {
153   if (!BFI)
154     return None;
155 
156   return BFI->getBlockProfileCount(*getFunction(), BB);
157 }
158 
159 void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB, uint64_t Freq) {
160   assert(BFI && "Expected analysis to be available");
161   BFI->setBlockFreq(BB, Freq);
162 }
163 
164 /// Pop up a ghostview window with the current block frequency propagation
165 /// rendered using dot.
166 void BlockFrequencyInfo::view() const {
167 // This code is only for debugging.
168 #ifndef NDEBUG
169   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
170 #else
171   errs() << "BlockFrequencyInfo::view is only available in debug builds on "
172             "systems with Graphviz or gv!\n";
173 #endif // NDEBUG
174 }
175 
176 const Function *BlockFrequencyInfo::getFunction() const {
177   return BFI ? BFI->getFunction() : nullptr;
178 }
179 
180 const BranchProbabilityInfo *BlockFrequencyInfo::getBPI() const {
181   return BFI ? &BFI->getBPI() : nullptr;
182 }
183 
184 raw_ostream &BlockFrequencyInfo::
185 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
186   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
187 }
188 
189 raw_ostream &
190 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
191                                    const BasicBlock *BB) const {
192   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
193 }
194 
195 uint64_t BlockFrequencyInfo::getEntryFreq() const {
196   return BFI ? BFI->getEntryFreq() : 0;
197 }
198 
199 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
200 
201 void BlockFrequencyInfo::print(raw_ostream &OS) const {
202   if (BFI)
203     BFI->print(OS);
204 }
205 
206 
207 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
208                       "Block Frequency Analysis", true, true)
209 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
210 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
211 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
212                     "Block Frequency Analysis", true, true)
213 
214 char BlockFrequencyInfoWrapperPass::ID = 0;
215 
216 
217 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
218     : FunctionPass(ID) {
219   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
220 }
221 
222 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
223 
224 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
225                                           const Module *) const {
226   BFI.print(OS);
227 }
228 
229 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
230   AU.addRequired<BranchProbabilityInfoWrapperPass>();
231   AU.addRequired<LoopInfoWrapperPass>();
232   AU.setPreservesAll();
233 }
234 
235 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
236 
237 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
238   BranchProbabilityInfo &BPI =
239       getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
240   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
241   BFI.calculate(F, BPI, LI);
242   return false;
243 }
244 
245 char BlockFrequencyAnalysis::PassID;
246 BlockFrequencyInfo BlockFrequencyAnalysis::run(Function &F,
247                                                AnalysisManager<Function> &AM) {
248   BlockFrequencyInfo BFI;
249   BFI.calculate(F, AM.getResult<BranchProbabilityAnalysis>(F),
250                 AM.getResult<LoopAnalysis>(F));
251   return BFI;
252 }
253 
254 PreservedAnalyses
255 BlockFrequencyPrinterPass::run(Function &F, AnalysisManager<Function> &AM) {
256   OS << "Printing analysis results of BFI for function "
257      << "'" << F.getName() << "':"
258      << "\n";
259   AM.getResult<BlockFrequencyAnalysis>(F).print(OS);
260   return PreservedAnalyses::all();
261 }
262