BlockFrequencyInfo.cpp revision 263508 
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/InitializePasses.h"
20#include "llvm/Support/CFG.h"
21#include "llvm/Support/CommandLine.h"
22#include "llvm/Support/Debug.h"
23#include "llvm/Support/GraphWriter.h"
24
25using namespace llvm;
26
27#ifndef NDEBUG
28enum GVDAGType {
29  GVDT_None,
30  GVDT_Fraction,
31  GVDT_Integer
32};
33
34static cl::opt<GVDAGType>
35ViewBlockFreqPropagationDAG("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
47namespace llvm {
48
49template <>
50struct 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
72template<>
73struct 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->getBlockFreq(Node).print(OS);
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
106INITIALIZE_PASS_BEGIN(BlockFrequencyInfo, "block-freq",
107                      "Block Frequency Analysis", true, true)
108INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfo)
109INITIALIZE_PASS_END(BlockFrequencyInfo, "block-freq",
110                    "Block Frequency Analysis", true, true)
111
112char BlockFrequencyInfo::ID = 0;
113
114
115BlockFrequencyInfo::BlockFrequencyInfo() : FunctionPass(ID) {
116  initializeBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
117  BFI = new BlockFrequencyImpl<BasicBlock, Function, BranchProbabilityInfo>();
118}
119
120BlockFrequencyInfo::~BlockFrequencyInfo() {
121  delete BFI;
122}
123
124void BlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
125  AU.addRequired<BranchProbabilityInfo>();
126  AU.setPreservesAll();
127}
128
129bool 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
139void BlockFrequencyInfo::print(raw_ostream &O, const Module *) const {
140  if (BFI) BFI->print(O);
141}
142
143BlockFrequency 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.
149void 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
159const Function *BlockFrequencyInfo::getFunction() const {
160  return BFI->Fn;
161}
162