ProfileInfo.cpp revision c758209153ca0f6da6737f25ada269c573fba456 
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>
21using namespace llvm;
22
23// Register the ProfileInfo interface, providing a nice name to refer to.
24namespace {
25  RegisterAnalysisGroup<ProfileInfo> Z("Profile Information");
26}
27char ProfileInfo::ID = 0;
28
29ProfileInfo::~ProfileInfo() {}
30
31unsigned ProfileInfo::getExecutionCount(BasicBlock *BB) const {
32  pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
33
34  // Are there zero predecessors of this block?
35  if (PI == PE) {
36    // If this is the entry block, look for the Null -> Entry edge.
37    if (BB == &BB->getParent()->getEntryBlock())
38      return getEdgeWeight(0, BB);
39    else
40      return 0;   // Otherwise, this is a dead block.
41  }
42
43  // Otherwise, if there are predecessors, the execution count of this block is
44  // the sum of the edge frequencies from the incoming edges.  Note that if
45  // there are multiple edges from a predecessor to this block that we don't
46  // want to count its weight multiple times.  For this reason, we keep track of
47  // the predecessors we've seen and only count them if we haven't run into them
48  // yet.
49  //
50  // We don't want to create an std::set unless we are dealing with a block that
51  // has a LARGE number of in-edges.  Handle the common case of having only a
52  // few in-edges with special code.
53  //
54  BasicBlock *FirstPred = *PI;
55  unsigned Count = getEdgeWeight(FirstPred, BB);
56  ++PI;
57  if (PI == PE) return Count;   // Quick exit for single predecessor blocks
58
59  BasicBlock *SecondPred = *PI;
60  if (SecondPred != FirstPred) Count += getEdgeWeight(SecondPred, BB);
61  ++PI;
62  if (PI == PE) return Count;   // Quick exit for two predecessor blocks
63
64  BasicBlock *ThirdPred = *PI;
65  if (ThirdPred != FirstPred && ThirdPred != SecondPred)
66    Count += getEdgeWeight(ThirdPred, BB);
67  ++PI;
68  if (PI == PE) return Count;   // Quick exit for three predecessor blocks
69
70  std::set<BasicBlock*> ProcessedPreds;
71  ProcessedPreds.insert(FirstPred);
72  ProcessedPreds.insert(SecondPred);
73  ProcessedPreds.insert(ThirdPred);
74  for (; PI != PE; ++PI)
75    if (ProcessedPreds.insert(*PI).second)
76      Count += getEdgeWeight(*PI, BB);
77  return Count;
78}
79
80
81
82//===----------------------------------------------------------------------===//
83//  NoProfile ProfileInfo implementation
84//
85
86namespace {
87  struct VISIBILITY_HIDDEN NoProfileInfo
88    : public ImmutablePass, public ProfileInfo {
89    static char ID; // Class identification, replacement for typeinfo
90    NoProfileInfo() : ImmutablePass((intptr_t)&ID) {}
91  };
92
93  char NoProfileInfo::ID = 0;
94  // Register this pass...
95  RegisterPass<NoProfileInfo>
96  X("no-profile", "No Profile Information", true, true);
97
98  // Declare that we implement the ProfileInfo interface
99  RegisterAnalysisGroup<ProfileInfo, true> Y(X);
100}  // End of anonymous namespace
101
102ImmutablePass *llvm::createNoProfileInfoPass() { return new NoProfileInfo(); }
103