lib/Analysis/BlockFrequencyInfo.cpp

   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 #define DEBUG_TYPE "block-freq"
  15 #include "llvm/Analysis/BlockFrequencyInfo.h"
  16 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
  17 #include "llvm/Analysis/BranchProbabilityInfo.h"
  18 #include "llvm/Analysis/LoopInfo.h"
  19 #include "llvm/Analysis/Passes.h"
  20 #include "llvm/IR/CFG.h"
  21 #include "llvm/InitializePasses.h"
  22 #include "llvm/Support/CommandLine.h"
  23 #include "llvm/Support/Debug.h"
  24 #include "llvm/Support/GraphWriter.h"
  25
  26 using namespace llvm;
  27
  28 #ifndef NDEBUG
  29 enum GVDAGType {
  30   GVDT_None,
  31   GVDT_Fraction,
  32   GVDT_Integer
  33 };
  34
  35 static cl::opt<GVDAGType>
  36 ViewBlockFreqPropagationDAG("view-block-freq-propagation-dags", cl::Hidden,
  37           cl::desc("Pop up a window to show a dag displaying how block "
  38                    "frequencies propagation through the CFG."),
  39           cl::values(
  40             clEnumValN(GVDT_None, "none",
  41                        "do not display graphs."),
  42             clEnumValN(GVDT_Fraction, "fraction", "display a graph using the "
  43                        "fractional block frequency representation."),
  44             clEnumValN(GVDT_Integer, "integer", "display a graph using the raw "
  45                        "integer fractional block frequency representation."),
  46             clEnumValEnd));
  47
  48 namespace llvm {
  49
  50 template <>
  51 struct GraphTraits<BlockFrequencyInfo *> {
  52   typedef const BasicBlock NodeType;
  53   typedef succ_const_iterator ChildIteratorType;
  54   typedef Function::const_iterator nodes_iterator;
  55
  56   static inline const NodeType *getEntryNode(const BlockFrequencyInfo *G) {
  57     return G->getFunction()->begin();
  58   }
  59   static ChildIteratorType child_begin(const NodeType *N) {
  60     return succ_begin(N);
  61   }
  62   static ChildIteratorType child_end(const NodeType *N) {
  63     return succ_end(N);
  64   }
  65   static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
  66     return G->getFunction()->begin();
  67   }
  68   static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
  69     return G->getFunction()->end();
  70   }
  71 };
  72
  73 template<>
  74 struct DOTGraphTraits<BlockFrequencyInfo*> : public DefaultDOTGraphTraits {
  75   explicit DOTGraphTraits(bool isSimple=false) :
  76     DefaultDOTGraphTraits(isSimple) {}
  77
  78   static std::string getGraphName(const BlockFrequencyInfo *G) {
  79     return G->getFunction()->getName();
  80   }
  81
  82   std::string getNodeLabel(const BasicBlock *Node,
  83                            const BlockFrequencyInfo *Graph) {
  84     std::string Result;
  85     raw_string_ostream OS(Result);
  86
  87     OS << Node->getName().str() << ":";
  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 Result;
 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 }