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