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 BlockFrequencyInfo::BlockFrequencyInfo() {}
109 
110 BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
111                                        const BranchProbabilityInfo &BPI,
112                                        const LoopInfo &LI) {
113   calculate(F, BPI, LI);
114 }
115 
116 void BlockFrequencyInfo::calculate(const Function &F,
117                                    const BranchProbabilityInfo &BPI,
118                                    const LoopInfo &LI) {
119   if (!BFI)
120     BFI.reset(new ImplType);
121   BFI->calculate(F, BPI, LI);
122 #ifndef NDEBUG
123   if (ViewBlockFreqPropagationDAG != GVDT_None)
124     view();
125 #endif
126 }
127 
128 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
129   return BFI ? BFI->getBlockFreq(BB) : 0;
130 }
131 
132 /// Pop up a ghostview window with the current block frequency propagation
133 /// rendered using dot.
134 void BlockFrequencyInfo::view() const {
135 // This code is only for debugging.
136 #ifndef NDEBUG
137   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
138 #else
139   errs() << "BlockFrequencyInfo::view is only available in debug builds on "
140             "systems with Graphviz or gv!\n";
141 #endif // NDEBUG
142 }
143 
144 const Function *BlockFrequencyInfo::getFunction() const {
145   return BFI ? BFI->getFunction() : nullptr;
146 }
147 
148 raw_ostream &BlockFrequencyInfo::
149 printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
150   return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
151 }
152 
153 raw_ostream &
154 BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
155                                    const BasicBlock *BB) const {
156   return BFI ? BFI->printBlockFreq(OS, BB) : OS;
157 }
158 
159 uint64_t BlockFrequencyInfo::getEntryFreq() const {
160   return BFI ? BFI->getEntryFreq() : 0;
161 }
162 
163 void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
164 
165 void BlockFrequencyInfo::print(raw_ostream &OS) const {
166   if (BFI)
167     BFI->print(OS);
168 }
169 
170 
171 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
172                       "Block Frequency Analysis", true, true)
173 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
174 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
175 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
176                     "Block Frequency Analysis", true, true)
177 
178 char BlockFrequencyInfoWrapperPass::ID = 0;
179 
180 
181 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
182     : FunctionPass(ID) {
183   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
184 }
185 
186 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
187 
188 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
189                                           const Module *) const {
190   BFI.print(OS);
191 }
192 
193 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
194   AU.addRequired<BranchProbabilityInfoWrapperPass>();
195   AU.addRequired<LoopInfoWrapperPass>();
196   AU.setPreservesAll();
197 }
198 
199 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
200 
201 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
202   BranchProbabilityInfo &BPI =
203       getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
204   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
205   BFI.calculate(F, BPI, LI);
206   return false;
207 }
208