AliasAnalysisEvaluator.cpp revision 1842a90e0bf7b9137fb595828c6e07c5b629b2ad 
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#include <set>
21
22namespace {
23  cl::opt<bool> PrintNo  ("print-no-aliases", cl::ReallyHidden);
24  cl::opt<bool> PrintMay ("print-may-aliases", cl::ReallyHidden);
25  cl::opt<bool> PrintMust("print-must-aliases", cl::ReallyHidden);
26
27  class AAEval : public FunctionPass {
28    unsigned No, May, Must;
29
30  public:
31    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
32      AU.addRequired<AliasAnalysis>();
33      AU.setPreservesAll();
34    }
35
36    bool doInitialization(Module &M) { No = May = Must = 0; return false; }
37    bool runOnFunction(Function &F);
38    bool doFinalization(Module &M);
39  };
40
41  RegisterOpt<AAEval>
42  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
43}
44
45static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2) {
46  if (P) {
47    std::cerr << "  " << Msg << ":\t";
48    WriteAsOperand(std::cerr, V1) << ", ";
49    WriteAsOperand(std::cerr, V2) << "\n";
50  }
51}
52
53bool AAEval::runOnFunction(Function &F) {
54  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
55
56  std::set<Value *> Pointers;
57
58  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
59    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
60      Pointers.insert(I);
61
62  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
63    if (isa<PointerType>((*I)->getType())) // Add all pointer instructions
64      Pointers.insert(*I);
65    for (User::op_iterator OI = (*I)->op_begin(); OI != (*I)->op_end(); ++OI)
66      if (isa<PointerType>((*OI)->getType()))
67        Pointers.insert(*OI);
68  }
69
70  if (PrintNo || PrintMay || PrintMust)
71    std::cerr << "Function: " << F.getName() << "\n";
72
73  // iterate over the worklist, and run the full (n^2)/2 disambiguations
74  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
75       I1 != E; ++I1)
76    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2)
77      switch (AA.alias(*I1, 0, *I2, 0)) {
78      case AliasAnalysis::NoAlias:
79        PrintResults("No", PrintNo, *I1, *I2);
80        ++No; break;
81      case AliasAnalysis::MayAlias:
82        PrintResults("May", PrintMay, *I1, *I2);
83        ++May; break;
84      case AliasAnalysis::MustAlias:
85        PrintResults("Must", PrintMust, *I1, *I2);
86        ++Must; break;
87      default:
88        std::cerr << "Unknown alias query result!\n";
89      }
90
91  return false;
92}
93
94bool AAEval::doFinalization(Module &M) {
95  unsigned Sum = No+May+Must;
96  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
97  if (Sum == 0) {
98    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
99    return false;
100  }
101
102  std::cerr << "  " << Sum << " Total Alias Queries Performed\n";
103  std::cerr << "  " << No << " no alias responses (" << No*100/Sum << "%)\n";
104  std::cerr << "  " << May << " may alias responses (" << May*100/Sum << "%)\n";
105  std::cerr << "  " << Must << " must alias responses (" <<Must*100/Sum<<"%)\n";
106  std::cerr << "  Alias Analysis Evaluator Summary: " << No*100/Sum << "%/"
107            << May*100/Sum << "%/" << Must*100/Sum<<"%\n";
108  return false;
109}
110