AliasAnalysisEvaluator.cpp revision d0fde30ce850b78371fd1386338350591f9ff494 
1//===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements a simple N^2 alias analysis accuracy evaluator.
11// Basically, for each function in the program, it simply queries to see how the
12// alias analysis implementation answers alias queries between each pair of
13// pointers in the function.
14//
15// This is inspired and adapted from code by: Naveen Neelakantam, Francesco
16// Spadini, and Wojciech Stryjewski.
17//
18//===----------------------------------------------------------------------===//
19
20#include "llvm/Analysis/AliasAnalysis.h"
21#include "llvm/Pass.h"
22#include "llvm/Function.h"
23#include "llvm/Type.h"
24#include "llvm/Support/InstIterator.h"
25#include "llvm/Assembly/Writer.h"
26#include "Support/CommandLine.h"
27#include <set>
28
29namespace llvm {
30
31namespace {
32  cl::opt<bool> PrintNo  ("print-no-aliases", cl::ReallyHidden);
33  cl::opt<bool> PrintMay ("print-may-aliases", cl::ReallyHidden);
34  cl::opt<bool> PrintMust("print-must-aliases", cl::ReallyHidden);
35
36  class AAEval : public FunctionPass {
37    unsigned No, May, Must;
38
39  public:
40    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
41      AU.addRequired<AliasAnalysis>();
42      AU.setPreservesAll();
43    }
44
45    bool doInitialization(Module &M) { No = May = Must = 0; return false; }
46    bool runOnFunction(Function &F);
47    bool doFinalization(Module &M);
48  };
49
50  RegisterOpt<AAEval>
51  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
52}
53
54static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2) {
55  if (P) {
56    std::cerr << "  " << Msg << ":\t";
57    WriteAsOperand(std::cerr, V1) << ", ";
58    WriteAsOperand(std::cerr, V2) << "\n";
59  }
60}
61
62bool AAEval::runOnFunction(Function &F) {
63  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
64
65  std::set<Value *> Pointers;
66
67  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
68    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
69      Pointers.insert(I);
70
71  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
72    if (isa<PointerType>((*I)->getType())) // Add all pointer instructions
73      Pointers.insert(*I);
74    for (User::op_iterator OI = (*I)->op_begin(); OI != (*I)->op_end(); ++OI)
75      if (isa<PointerType>((*OI)->getType()))
76        Pointers.insert(*OI);
77  }
78
79  if (PrintNo || PrintMay || PrintMust)
80    std::cerr << "Function: " << F.getName() << "\n";
81
82  // iterate over the worklist, and run the full (n^2)/2 disambiguations
83  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
84       I1 != E; ++I1)
85    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2)
86      switch (AA.alias(*I1, 0, *I2, 0)) {
87      case AliasAnalysis::NoAlias:
88        PrintResults("No", PrintNo, *I1, *I2);
89        ++No; break;
90      case AliasAnalysis::MayAlias:
91        PrintResults("May", PrintMay, *I1, *I2);
92        ++May; break;
93      case AliasAnalysis::MustAlias:
94        PrintResults("Must", PrintMust, *I1, *I2);
95        ++Must; break;
96      default:
97        std::cerr << "Unknown alias query result!\n";
98      }
99
100  return false;
101}
102
103bool AAEval::doFinalization(Module &M) {
104  unsigned Sum = No+May+Must;
105  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
106  if (Sum == 0) {
107    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
108    return false;
109  }
110
111  std::cerr << "  " << Sum << " Total Alias Queries Performed\n";
112  std::cerr << "  " << No << " no alias responses (" << No*100/Sum << "%)\n";
113  std::cerr << "  " << May << " may alias responses (" << May*100/Sum << "%)\n";
114  std::cerr << "  " << Must << " must alias responses (" <<Must*100/Sum<<"%)\n";
115  std::cerr << "  Alias Analysis Evaluator Summary: " << No*100/Sum << "%/"
116            << May*100/Sum << "%/" << Must*100/Sum<<"%\n";
117  return false;
118}
119
120} // End llvm namespace
121