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 enum GVDAGType {
31   GVDT_None,
32   GVDT_Fraction,
33   GVDT_Integer
34 };
35 
36 static cl::opt<GVDAGType>
37 ViewBlockFreqPropagationDAG("view-block-freq-propagation-dags", cl::Hidden,
38           cl::desc("Pop up a window to show a dag displaying how block "
39                    "frequencies propagation through the CFG."),
40           cl::values(
41             clEnumValN(GVDT_None, "none",
42                        "do not display graphs."),
43             clEnumValN(GVDT_Fraction, "fraction", "display a graph using the "
44                        "fractional block frequency representation."),
45             clEnumValN(GVDT_Integer, "integer", "display a graph using the raw "
46                        "integer fractional block frequency representation."),
47             clEnumValEnd));
48 
49 namespace llvm {
50 
51 template <>
52 struct GraphTraits<BlockFrequencyInfo *> {
53   typedef const BasicBlock NodeType;
54   typedef succ_const_iterator ChildIteratorType;
55   typedef Function::const_iterator nodes_iterator;
56 
57   static inline const NodeType *getEntryNode(const BlockFrequencyInfo *G) {
58     return G->getFunction()->begin();
59   }
60   static ChildIteratorType child_begin(const NodeType *N) {
61     return succ_begin(N);
62   }
63   static ChildIteratorType child_end(const NodeType *N) {
64     return succ_end(N);
65   }
66   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
67     return G->getFunction()->begin();
68   }
69   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
70     return G->getFunction()->end();
71   }
72 };
73 
74 template<>
75 struct DOTGraphTraits<BlockFrequencyInfo*> : public DefaultDOTGraphTraits {
76   explicit DOTGraphTraits(bool isSimple=false) :
77     DefaultDOTGraphTraits(isSimple) {}
78 
79   static std::string getGraphName(const BlockFrequencyInfo *G) {
80     return G->getFunction()->getName();
81   }
82 
83   std::string getNodeLabel(const BasicBlock *Node,
84                            const BlockFrequencyInfo *Graph) {
85     string_ostream OS;
86 
87     OS << Node->getName() << ":";
88     switch (ViewBlockFreqPropagationDAG) {
89     case GVDT_Fraction:
90       Graph->printBlockFreq(OS, Node);
91       break;
92     case GVDT_Integer:
93       OS << Graph->getBlockFreq(Node).getFrequency();
94       break;
95     case GVDT_None:
96       llvm_unreachable("If we are not supposed to render a graph we should "
97                        "never reach this point.");
98     }
99 
100     return OS.str();
101   }
102 };
103 
104 } // end namespace llvm
105 #endif
106 
107 INITIALIZE_PASS_BEGIN(BlockFrequencyInfo, "block-freq",
108                       "Block Frequency Analysis", true, true)
109 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfo)
110 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
111 INITIALIZE_PASS_END(BlockFrequencyInfo, "block-freq",
112                     "Block Frequency Analysis", true, true)
113 
114 char BlockFrequencyInfo::ID = 0;
115 
116 
117 BlockFrequencyInfo::BlockFrequencyInfo() : FunctionPass(ID) {
118   initializeBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
119 }
120 
121 BlockFrequencyInfo::~BlockFrequencyInfo() {}
122 
123 void BlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
124   AU.addRequired<BranchProbabilityInfo>();
125   AU.addRequired<LoopInfo>();
126   AU.setPreservesAll();
127 }
128 
129 bool BlockFrequencyInfo::runOnFunction(Function &F) {
130   BranchProbabilityInfo &BPI = getAnalysis<BranchProbabilityInfo>();
131   LoopInfo &LI = getAnalysis<LoopInfo>();
132   if (!BFI)
133     BFI.reset(new ImplType);
134   BFI->doFunction(&F, &BPI, &LI);
135 #ifndef NDEBUG
136   if (ViewBlockFreqPropagationDAG != GVDT_None)
137     view();
138 #endif
139   return false;
140 }
141 
142 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
143 
144 void BlockFrequencyInfo::print(raw_ostream &O, const Module *) const {
145   if (BFI) BFI->print(O);
146 }
147 
148 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
149   return BFI ? BFI->getBlockFreq(BB) : 0;
150 }
151 
152 /// Pop up a ghostview window with the current block frequency propagation
153 /// rendered using dot.
154 void BlockFrequencyInfo::view() const {
155 // This code is only for debugging.
156 #ifndef NDEBUG
157   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
158 #else
159   errs() << "BlockFrequencyInfo::view is only available in debug builds on "
160             "systems with Graphviz or gv!\n";
161 #endif // NDEBUG
162 }
163 
164 const Function *BlockFrequencyInfo::getFunction() const {
165   return BFI ? BFI->getFunction() : nullptr;
166 }
167 
168 raw_ostream &BlockFrequencyInfo::
169 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
170   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
171 }
172 
173 raw_ostream &
174 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
175                                    const BasicBlock *BB) const {
176   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
177 }
178 
179 uint64_t BlockFrequencyInfo::getEntryFreq() const {
180   return BFI ? BFI->getEntryFreq() : 0;
181 }
182