AliasAnalysisEvaluator.cpp revision b576c94c15af9a440f69d9d03c2afead7971118c 
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 {
30  cl::opt<bool> PrintNo  ("print-no-aliases", cl::ReallyHidden);
31  cl::opt<bool> PrintMay ("print-may-aliases", cl::ReallyHidden);
32  cl::opt<bool> PrintMust("print-must-aliases", cl::ReallyHidden);
33
34  class AAEval : public FunctionPass {
35    unsigned No, May, Must;
36
37  public:
38    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
39      AU.addRequired<AliasAnalysis>();
40      AU.setPreservesAll();
41    }
42
43    bool doInitialization(Module &M) { No = May = Must = 0; return false; }
44    bool runOnFunction(Function &F);
45    bool doFinalization(Module &M);
46  };
47
48  RegisterOpt<AAEval>
49  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
50}
51
52static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2) {
53  if (P) {
54    std::cerr << "  " << Msg << ":\t";
55    WriteAsOperand(std::cerr, V1) << ", ";
56    WriteAsOperand(std::cerr, V2) << "\n";
57  }
58}
59
60bool AAEval::runOnFunction(Function &F) {
61  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
62
63  std::set<Value *> Pointers;
64
65  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
66    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
67      Pointers.insert(I);
68
69  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
70    if (isa<PointerType>((*I)->getType())) // Add all pointer instructions
71      Pointers.insert(*I);
72    for (User::op_iterator OI = (*I)->op_begin(); OI != (*I)->op_end(); ++OI)
73      if (isa<PointerType>((*OI)->getType()))
74        Pointers.insert(*OI);
75  }
76
77  if (PrintNo || PrintMay || PrintMust)
78    std::cerr << "Function: " << F.getName() << "\n";
79
80  // iterate over the worklist, and run the full (n^2)/2 disambiguations
81  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
82       I1 != E; ++I1)
83    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2)
84      switch (AA.alias(*I1, 0, *I2, 0)) {
85      case AliasAnalysis::NoAlias:
86        PrintResults("No", PrintNo, *I1, *I2);
87        ++No; break;
88      case AliasAnalysis::MayAlias:
89        PrintResults("May", PrintMay, *I1, *I2);
90        ++May; break;
91      case AliasAnalysis::MustAlias:
92        PrintResults("Must", PrintMust, *I1, *I2);
93        ++Must; break;
94      default:
95        std::cerr << "Unknown alias query result!\n";
96      }
97
98  return false;
99}
100
101bool AAEval::doFinalization(Module &M) {
102  unsigned Sum = No+May+Must;
103  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
104  if (Sum == 0) {
105    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
106    return false;
107  }
108
109  std::cerr << "  " << Sum << " Total Alias Queries Performed\n";
110  std::cerr << "  " << No << " no alias responses (" << No*100/Sum << "%)\n";
111  std::cerr << "  " << May << " may alias responses (" << May*100/Sum << "%)\n";
112  std::cerr << "  " << Must << " must alias responses (" <<Must*100/Sum<<"%)\n";
113  std::cerr << "  Alias Analysis Evaluator Summary: " << No*100/Sum << "%/"
114            << May*100/Sum << "%/" << Must*100/Sum<<"%\n";
115  return false;
116}
117