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 *NodeRef;
64   typedef succ_const_iterator ChildIteratorType;
65   typedef pointer_iterator<Function::const_iterator> nodes_iterator;
66 
67   static NodeRef getEntryNode(const BlockFrequencyInfo *G) {
68     return &G->getFunction()->front();
69   }
70   static ChildIteratorType child_begin(const NodeRef N) {
71     return succ_begin(N);
72   }
73   static ChildIteratorType child_end(const NodeRef N) { return succ_end(N); }
74   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
75     return nodes_iterator(G->getFunction()->begin());
76   }
77   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
78     return nodes_iterator(G->getFunction()->end());
79   }
80 };
81 
82 typedef BFIDOTGraphTraitsBase<BlockFrequencyInfo, BranchProbabilityInfo>
83     BFIDOTGTraitsBase;
84 
85 template <>
86 struct DOTGraphTraits<BlockFrequencyInfo *> : public BFIDOTGTraitsBase {
87   explicit DOTGraphTraits(bool isSimple = false)
88       : BFIDOTGTraitsBase(isSimple) {}
89 
90   std::string getNodeLabel(const BasicBlock *Node,
91                            const BlockFrequencyInfo *Graph) {
92 
93     return BFIDOTGTraitsBase::getNodeLabel(Node, Graph,
94                                            ViewBlockFreqPropagationDAG);
95   }
96 
97   std::string getNodeAttributes(const BasicBlock *Node,
98                                 const BlockFrequencyInfo *Graph) {
99     return BFIDOTGTraitsBase::getNodeAttributes(Node, Graph,
100                                                 ViewHotFreqPercent);
101   }
102 
103   std::string getEdgeAttributes(const BasicBlock *Node, EdgeIter EI,
104                                 const BlockFrequencyInfo *BFI) {
105     return BFIDOTGTraitsBase::getEdgeAttributes(Node, EI, BFI, BFI->getBPI(),
106                                                 ViewHotFreqPercent);
107   }
108 };
109 
110 } // end namespace llvm
111 #endif
112 
113 BlockFrequencyInfo::BlockFrequencyInfo() {}
114 
115 BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
116                                        const BranchProbabilityInfo &BPI,
117                                        const LoopInfo &LI) {
118   calculate(F, BPI, LI);
119 }
120 
121 BlockFrequencyInfo::BlockFrequencyInfo(BlockFrequencyInfo &&Arg)
122     : BFI(std::move(Arg.BFI)) {}
123 
124 BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
125   releaseMemory();
126   BFI = std::move(RHS.BFI);
127   return *this;
128 }
129 
130 // Explicitly define the default constructor otherwise it would be implicitly
131 // defined at the first ODR-use which is the BFI member in the
132 // LazyBlockFrequencyInfo header.  The dtor needs the BlockFrequencyInfoImpl
133 // template instantiated which is not available in the header.
134 BlockFrequencyInfo::~BlockFrequencyInfo() {}
135 
136 void BlockFrequencyInfo::calculate(const Function &F,
137                                    const BranchProbabilityInfo &BPI,
138                                    const LoopInfo &LI) {
139   if (!BFI)
140     BFI.reset(new ImplType);
141   BFI->calculate(F, BPI, LI);
142 #ifndef NDEBUG
143   if (ViewBlockFreqPropagationDAG != GVDT_None &&
144       (ViewBlockFreqFuncName.empty() ||
145        F.getName().equals(ViewBlockFreqFuncName))) {
146     view();
147   }
148 #endif
149 }
150 
151 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
152   return BFI ? BFI->getBlockFreq(BB) : 0;
153 }
154 
155 Optional<uint64_t>
156 BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB) const {
157   if (!BFI)
158     return None;
159 
160   return BFI->getBlockProfileCount(*getFunction(), BB);
161 }
162 
163 Optional<uint64_t>
164 BlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
165   if (!BFI)
166     return None;
167   return BFI->getProfileCountFromFreq(*getFunction(), Freq);
168 }
169 
170 void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB, uint64_t Freq) {
171   assert(BFI && "Expected analysis to be available");
172   BFI->setBlockFreq(BB, Freq);
173 }
174 
175 /// Pop up a ghostview window with the current block frequency propagation
176 /// rendered using dot.
177 void BlockFrequencyInfo::view() const {
178 // This code is only for debugging.
179 #ifndef NDEBUG
180   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
181 #else
182   errs() << "BlockFrequencyInfo::view is only available in debug builds on "
183             "systems with Graphviz or gv!\n";
184 #endif // NDEBUG
185 }
186 
187 const Function *BlockFrequencyInfo::getFunction() const {
188   return BFI ? BFI->getFunction() : nullptr;
189 }
190 
191 const BranchProbabilityInfo *BlockFrequencyInfo::getBPI() const {
192   return BFI ? &BFI->getBPI() : nullptr;
193 }
194 
195 raw_ostream &BlockFrequencyInfo::
196 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
197   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
198 }
199 
200 raw_ostream &
201 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
202                                    const BasicBlock *BB) const {
203   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
204 }
205 
206 uint64_t BlockFrequencyInfo::getEntryFreq() const {
207   return BFI ? BFI->getEntryFreq() : 0;
208 }
209 
210 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
211 
212 void BlockFrequencyInfo::print(raw_ostream &OS) const {
213   if (BFI)
214     BFI->print(OS);
215 }
216 
217 
218 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
219                       "Block Frequency Analysis", true, true)
220 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
221 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
222 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
223                     "Block Frequency Analysis", true, true)
224 
225 char BlockFrequencyInfoWrapperPass::ID = 0;
226 
227 
228 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
229     : FunctionPass(ID) {
230   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
231 }
232 
233 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
234 
235 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
236                                           const Module *) const {
237   BFI.print(OS);
238 }
239 
240 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
241   AU.addRequired<BranchProbabilityInfoWrapperPass>();
242   AU.addRequired<LoopInfoWrapperPass>();
243   AU.setPreservesAll();
244 }
245 
246 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
247 
248 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
249   BranchProbabilityInfo &BPI =
250       getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
251   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
252   BFI.calculate(F, BPI, LI);
253   return false;
254 }
255 
256 char BlockFrequencyAnalysis::PassID;
257 BlockFrequencyInfo BlockFrequencyAnalysis::run(Function &F,
258                                                FunctionAnalysisManager &AM) {
259   BlockFrequencyInfo BFI;
260   BFI.calculate(F, AM.getResult<BranchProbabilityAnalysis>(F),
261                 AM.getResult<LoopAnalysis>(F));
262   return BFI;
263 }
264 
265 PreservedAnalyses
266 BlockFrequencyPrinterPass::run(Function &F, FunctionAnalysisManager &AM) {
267   OS << "Printing analysis results of BFI for function "
268      << "'" << F.getName() << "':"
269      << "\n";
270   AM.getResult<BlockFrequencyAnalysis>(F).print(OS);
271   return PreservedAnalyses::all();
272 }
273