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     std::string Result;
86     raw_string_ostream OS(Result);
87 
88     OS << Node->getName() << ":";
89     switch (ViewBlockFreqPropagationDAG) {
90     case GVDT_Fraction:
91       Graph->printBlockFreq(OS, Node);
92       break;
93     case GVDT_Integer:
94       OS << Graph->getBlockFreq(Node).getFrequency();
95       break;
96     case GVDT_None:
97       llvm_unreachable("If we are not supposed to render a graph we should "
98                        "never reach this point.");
99     }
100 
101     return Result;
102   }
103 };
104 
105 } // end namespace llvm
106 #endif
107 
108 void BlockFrequencyInfo::calculate(const Function &F,
109                                    const BranchProbabilityInfo &BPI,
110                                    const LoopInfo &LI) {
111   if (!BFI)
112     BFI.reset(new ImplType);
113   BFI->doFunction(&F, &BPI, &LI);
114 #ifndef NDEBUG
115   if (ViewBlockFreqPropagationDAG != GVDT_None)
116     view();
117 #endif
118 }
119 
120 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
121   return BFI ? BFI->getBlockFreq(BB) : 0;
122 }
123 
124 /// Pop up a ghostview window with the current block frequency propagation
125 /// rendered using dot.
126 void BlockFrequencyInfo::view() const {
127 // This code is only for debugging.
128 #ifndef NDEBUG
129   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
130 #else
131   errs() << "BlockFrequencyInfo::view is only available in debug builds on "
132             "systems with Graphviz or gv!\n";
133 #endif // NDEBUG
134 }
135 
136 const Function *BlockFrequencyInfo::getFunction() const {
137   return BFI ? BFI->getFunction() : nullptr;
138 }
139 
140 raw_ostream &BlockFrequencyInfo::
141 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
142   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
143 }
144 
145 raw_ostream &
146 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
147                                    const BasicBlock *BB) const {
148   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
149 }
150 
151 uint64_t BlockFrequencyInfo::getEntryFreq() const {
152   return BFI ? BFI->getEntryFreq() : 0;
153 }
154 
155 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
156 
157 void BlockFrequencyInfo::print(raw_ostream &OS) const {
158   if (BFI)
159     BFI->print(OS);
160 }
161 
162 
163 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
164                       "Block Frequency Analysis", true, true)
165 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfo)
166 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
167 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
168                     "Block Frequency Analysis", true, true)
169 
170 char BlockFrequencyInfoWrapperPass::ID = 0;
171 
172 
173 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
174     : FunctionPass(ID) {
175   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
176 }
177 
178 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
179 
180 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
181                                           const Module *) const {
182   BFI.print(OS);
183 }
184 
185 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
186   AU.addRequired<BranchProbabilityInfo>();
187   AU.addRequired<LoopInfoWrapperPass>();
188   AU.setPreservesAll();
189 }
190 
191 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
192 
193 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
194   BranchProbabilityInfo &BPI = getAnalysis<BranchProbabilityInfo>();
195   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
196   BFI.calculate(F, BPI, LI);
197   return false;
198 }
199