AliasAnalysisEvaluator.cpp revision 638b381713e32a0a9fb2a83c43b600683116df52 
1//===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
2//
3// This file implements a simple N^2 alias analysis accuracy evaluator.
4// Basically, for each function in the program, it simply queries to see how the
5// alias analysis implementation answers alias queries between each pair of
6// pointers in the function.
7//
8// This is inspired and adapted from code by: Naveen Neelakantam, Francesco
9// Spadini, and Wojciech Stryjewski.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/Analysis/AliasAnalysis.h"
14#include "llvm/Pass.h"
15#include "llvm/Function.h"
16#include "llvm/Type.h"
17#include "llvm/Support/InstIterator.h"
18#include "llvm/Assembly/Writer.h"
19#include "Support/CommandLine.h"
20
21namespace {
22  cl::opt<bool> PrintNo  ("print-no-alias-results", cl::ReallyHidden);
23  cl::opt<bool> PrintMay ("print-may-alias-results", cl::ReallyHidden);
24  cl::opt<bool> PrintMust("print-must-alias-results", cl::ReallyHidden);
25
26  class AAEval : public FunctionPass {
27    unsigned No, May, Must;
28
29  public:
30    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
31      AU.addRequired<AliasAnalysis>();
32      AU.setPreservesAll();
33    }
34
35    bool doInitialization(Module &M) { No = May = Must = 0; return false; }
36    bool runOnFunction(Function &F);
37    bool doFinalization(Module &M);
38  };
39
40  RegisterOpt<AAEval>
41  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
42}
43
44static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2) {
45  if (P) {
46    std::cerr << "  " << Msg << ":\t";
47    WriteAsOperand(std::cerr, V1) << ", ";
48    WriteAsOperand(std::cerr, V2) << "\n";
49  }
50}
51
52bool AAEval::runOnFunction(Function &F) {
53  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
54
55  std::vector<Value *> Pointers;
56
57  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
58    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
59      Pointers.push_back(I);
60
61  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
62    if (isa<PointerType>((*I)->getType())) // Add all pointer instructions
63      Pointers.push_back(*I);
64
65  if (PrintNo || PrintMay || PrintMust)
66    std::cerr << "Function: " << F.getName() << "\n";
67
68  // iterate over the worklist, and run the full (n^2)/2 disambiguations
69  for (std::vector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
70       I1 != E; ++I1)
71    for (std::vector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2)
72      switch (AA.alias(*I1, *I2)) {
73      case AliasAnalysis::NoAlias:
74        PrintResults("No", PrintNo, *I1, *I2);
75        ++No; break;
76      case AliasAnalysis::MayAlias:
77        PrintResults("May", PrintMay, *I1, *I2);
78        ++May; break;
79      case AliasAnalysis::MustAlias:
80        PrintResults("Must", PrintMust, *I1, *I2);
81        ++Must; break;
82      default:
83        std::cerr << "Unknown alias query result!\n";
84      }
85
86  return false;
87}
88
89bool AAEval::doFinalization(Module &M) {
90  unsigned Sum = No+May+Must;
91  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
92  if (Sum == 0) {
93    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
94    return false;
95  }
96
97  std::cerr << "  " << Sum << " Total Alias Queries Performed\n";
98  std::cerr << "  " << No << " no alias responses (" << No*100/Sum << "%)\n";
99  std::cerr << "  " << May << " may alias responses (" << May*100/Sum << "%)\n";
100  std::cerr << "  " << Must << " must alias responses (" <<Must*100/Sum<<"%)\n";
101  std::cerr << "  Alias Analysis Evaluator Summary: " << No*100/Sum << "%/"
102            << May*100/Sum << "%/" << Must*100/Sum<<"%\n";
103  return false;
104}
105