lib/Analysis/ProfileInfo.cpp

   1 //===- ProfileInfo.cpp - Profile Info Interface ---------------------------===//
   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 // This file implements the abstract ProfileInfo interface, and the default
  11 // "no profile" implementation.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Analysis/Passes.h"
  16 #include "llvm/Analysis/ProfileInfo.h"
  17 #include "llvm/Pass.h"
  18 #include "llvm/Support/CFG.h"
  19 #include "llvm/Support/Compiler.h"
  20 #include <set>
  21 using namespace llvm;
  22
  23 // Register the ProfileInfo interface, providing a nice name to refer to.
  24 static RegisterAnalysisGroup<ProfileInfo> Z("Profile Information");
  25 char ProfileInfo::ID = 0;
  26
  27 ProfileInfo::~ProfileInfo() {}
  28
  29 unsigned ProfileInfo::getExecutionCount(BasicBlock *BB) const {
  30   pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
  31
  32   // Are there zero predecessors of this block?
  33   if (PI == PE) {
  34     // If this is the entry block, look for the Null -> Entry edge.
  35     if (BB == &BB->getParent()->getEntryBlock())
  36       return getEdgeWeight(0, BB);
  37     else
  38       return 0;   // Otherwise, this is a dead block.
  39   }
  40
  41   // Otherwise, if there are predecessors, the execution count of this block is
  42   // the sum of the edge frequencies from the incoming edges.  Note that if
  43   // there are multiple edges from a predecessor to this block that we don't
  44   // want to count its weight multiple times.  For this reason, we keep track of
  45   // the predecessors we've seen and only count them if we haven't run into them
  46   // yet.
  47   //
  48   // We don't want to create an std::set unless we are dealing with a block that
  49   // has a LARGE number of in-edges.  Handle the common case of having only a
  50   // few in-edges with special code.
  51   //
  52   BasicBlock *FirstPred = *PI;
  53   unsigned Count = getEdgeWeight(FirstPred, BB);
  54   ++PI;
  55   if (PI == PE) return Count;   // Quick exit for single predecessor blocks
  56
  57   BasicBlock *SecondPred = *PI;
  58   if (SecondPred != FirstPred) Count += getEdgeWeight(SecondPred, BB);
  59   ++PI;
  60   if (PI == PE) return Count;   // Quick exit for two predecessor blocks
  61
  62   BasicBlock *ThirdPred = *PI;
  63   if (ThirdPred != FirstPred && ThirdPred != SecondPred)
  64     Count += getEdgeWeight(ThirdPred, BB);
  65   ++PI;
  66   if (PI == PE) return Count;   // Quick exit for three predecessor blocks
  67
  68   std::set<BasicBlock*> ProcessedPreds;
  69   ProcessedPreds.insert(FirstPred);
  70   ProcessedPreds.insert(SecondPred);
  71   ProcessedPreds.insert(ThirdPred);
  72   for (; PI != PE; ++PI)
  73     if (ProcessedPreds.insert(*PI).second)
  74       Count += getEdgeWeight(*PI, BB);
  75   return Count;
  76 }
  77
  78
  79
  80 //===----------------------------------------------------------------------===//
  81 //  NoProfile ProfileInfo implementation
  82 //
  83
  84 namespace {
  85   struct VISIBILITY_HIDDEN NoProfileInfo
  86     : public ImmutablePass, public ProfileInfo {
  87     static char ID; // Class identification, replacement for typeinfo
  88     NoProfileInfo() : ImmutablePass(&ID) {}
  89   };
  90 }  // End of anonymous namespace
  91
  92 char NoProfileInfo::ID = 0;
  93 // Register this pass...
  94 static RegisterPass<NoProfileInfo>
  95 X("no-profile", "No Profile Information", false, true);
  96
  97 // Declare that we implement the ProfileInfo interface
  98 static RegisterAnalysisGroup<ProfileInfo, true> Y(X);
  99
 100 ImmutablePass *llvm::createNoProfileInfoPass() { return new NoProfileInfo(); }