AliasAnalysisEvaluator.cpp revision ad48cc71dcd218216e5e7df6d05c481946a65879 
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/Function.h"
21#include "llvm/iOther.h"
22#include "llvm/iTerminators.h"
23#include "llvm/Pass.h"
24#include "llvm/Type.h"
25#include "llvm/Analysis/AliasAnalysis.h"
26#include "llvm/Assembly/Writer.h"
27#include "llvm/Support/InstIterator.h"
28#include "Support/CommandLine.h"
29#include <iostream>
30#include <set>
31
32using namespace llvm;
33
34namespace {
35  cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
36
37  cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
38  cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
39  cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
40
41  cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
42  cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
43  cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
44  cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
45
46  class AAEval : public FunctionPass {
47    unsigned NoAlias, MayAlias, MustAlias;
48    unsigned NoModRef, Mod, Ref, ModRef;
49
50  public:
51    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
52      AU.addRequired<AliasAnalysis>();
53      AU.setPreservesAll();
54    }
55
56    bool doInitialization(Module &M) {
57      NoAlias = MayAlias = MustAlias = 0;
58      NoModRef = Mod = Ref = ModRef = 0;
59
60      if (PrintAll) {
61        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
62        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
63      }
64      return false;
65    }
66
67    bool runOnFunction(Function &F);
68    bool doFinalization(Module &M);
69  };
70
71  RegisterOpt<AAEval>
72  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
73}
74
75static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
76                                Module *M) {
77  if (P) {
78    std::cerr << "  " << Msg << ":\t";
79    WriteAsOperand(std::cerr, V1, true, true, M) << ", ";
80    WriteAsOperand(std::cerr, V2, true, true, M) << "\n";
81  }
82}
83
84static inline void
85PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
86                   Module *M) {
87  if (P) {
88    std::cerr << "  " << Msg << ":  Ptr: ";
89    WriteAsOperand(std::cerr, Ptr, true, true, M);
90    std::cerr << "\t<->" << *I;
91  }
92}
93
94bool AAEval::runOnFunction(Function &F) {
95  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
96
97  std::set<Value *> Pointers;
98  std::set<CallSite> CallSites;
99
100  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
101    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
102      Pointers.insert(I);
103
104  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
105    if (isa<PointerType>(I->getType())) // Add all pointer instructions
106      Pointers.insert(&*I);
107    for (User::op_iterator OI = (*I).op_begin(); OI != (*I).op_end(); ++OI)
108      if (isa<PointerType>((*OI)->getType()))
109        Pointers.insert(*OI);
110
111    CallSite CS = CallSite::get(&*I);
112    if (CS.getInstruction()) CallSites.insert(CS);
113  }
114
115  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
116      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
117    std::cerr << "Function: " << F.getName() << ": " << Pointers.size()
118              << " pointers, " << CallSites.size() << " call sites\n";
119
120  // iterate over the worklist, and run the full (n^2)/2 disambiguations
121  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
122       I1 != E; ++I1)
123    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2)
124      switch (AA.alias(*I1, 0, *I2, 0)) {
125      case AliasAnalysis::NoAlias:
126        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
127        ++NoAlias; break;
128      case AliasAnalysis::MayAlias:
129        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
130        ++MayAlias; break;
131      case AliasAnalysis::MustAlias:
132        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
133        ++MustAlias; break;
134      default:
135        std::cerr << "Unknown alias query result!\n";
136      }
137
138  // Mod/ref alias analysis: compare all pairs of calls and values
139  for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
140       V != Ve; ++V)
141    for (std::set<CallSite>::iterator C = CallSites.begin(),
142           Ce = CallSites.end(); C != Ce; ++C) {
143      Instruction *I = C->getInstruction();
144      switch (AA.getModRefInfo(*C, *V, (*V)->getType()->getPrimitiveSize())) {
145      case AliasAnalysis::NoModRef:
146        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
147        ++NoModRef; break;
148      case AliasAnalysis::Mod:
149        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
150        ++Mod; break;
151      case AliasAnalysis::Ref:
152        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
153        ++Ref; break;
154      case AliasAnalysis::ModRef:
155        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
156        ++ModRef; break;
157      default:
158        std::cerr << "Unknown alias query result!\n";
159      }
160    }
161
162  return false;
163}
164
165bool AAEval::doFinalization(Module &M) {
166  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
167  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
168  if (AliasSum == 0) {
169    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
170  } else {
171    std::cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
172    std::cerr << "  " << NoAlias << " no alias responses ("
173              << NoAlias*100/AliasSum << "%)\n";
174    std::cerr << "  " << MayAlias << " may alias responses ("
175              << MayAlias*100/AliasSum << "%)\n";
176    std::cerr << "  " << MustAlias << " must alias responses ("
177              << MustAlias*100/AliasSum <<"%)\n";
178    std::cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
179              << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
180              << MustAlias*100/AliasSum << "%\n";
181  }
182
183  // Display the summary for mod/ref analysis
184  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
185  if (ModRefSum == 0) {
186    std::cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
187  } else {
188    std::cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
189    std::cerr << "  " << NoModRef << " no mod/ref responses ("
190              << NoModRef*100/ModRefSum << "%)\n";
191    std::cerr << "  " << Mod << " mod responses ("
192              << Mod*100/ModRefSum << "%)\n";
193    std::cerr << "  " << Ref << " ref responses ("
194              << Ref*100/ModRefSum <<"%)\n";
195    std::cerr << "  " << ModRef << " mod & ref responses ("
196              << ModRef*100/ModRefSum <<"%)\n";
197    std::cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
198              << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
199              << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
200  }
201
202  return false;
203}
204