AliasAnalysisEvaluator.cpp revision d7d83db5f22d05e5b14b6b1d838668222113c83a 
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/Constants.h"
21#include "llvm/DerivedTypes.h"
22#include "llvm/Function.h"
23#include "llvm/Instructions.h"
24#include "llvm/Pass.h"
25#include "llvm/Analysis/Passes.h"
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Assembly/Writer.h"
28#include "llvm/Target/TargetData.h"
29#include "llvm/Support/InstIterator.h"
30#include "llvm/Support/CommandLine.h"
31#include "llvm/Support/Compiler.h"
32#include "llvm/Support/Streams.h"
33#include <set>
34using namespace llvm;
35
36namespace {
37  cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
38
39  cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
40  cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
41  cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
42
43  cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
44  cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
45  cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
46  cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
47
48  class VISIBILITY_HIDDEN AAEval : public FunctionPass {
49    unsigned NoAlias, MayAlias, MustAlias;
50    unsigned NoModRef, Mod, Ref, ModRef;
51
52  public:
53    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
54      AU.addRequired<AliasAnalysis>();
55      AU.setPreservesAll();
56    }
57
58    bool doInitialization(Module &M) {
59      NoAlias = MayAlias = MustAlias = 0;
60      NoModRef = Mod = Ref = ModRef = 0;
61
62      if (PrintAll) {
63        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
64        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
65      }
66      return false;
67    }
68
69    bool runOnFunction(Function &F);
70    bool doFinalization(Module &M);
71  };
72
73  RegisterPass<AAEval>
74  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
75}
76
77FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
78
79static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
80                                Module *M) {
81  if (P) {
82    cerr << "  " << Msg << ":\t";
83    WriteAsOperand(*cerr.stream(), V1, true, M) << ", ";
84    WriteAsOperand(*cerr.stream(), V2, true, M) << "\n";
85  }
86}
87
88static inline void
89PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
90                   Module *M) {
91  if (P) {
92    cerr << "  " << Msg << ":  Ptr: ";
93    WriteAsOperand(*cerr.stream(), Ptr, true, M);
94    cerr << "\t<->" << *I;
95  }
96}
97
98bool AAEval::runOnFunction(Function &F) {
99  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
100
101  const TargetData &TD = AA.getTargetData();
102
103  std::set<Value *> Pointers;
104  std::set<CallSite> CallSites;
105
106  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
107    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
108      Pointers.insert(I);
109
110  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
111    if (isa<PointerType>(I->getType())) // Add all pointer instructions
112      Pointers.insert(&*I);
113    Instruction &Inst = *I;
114    User::op_iterator OI = Inst.op_begin();
115    if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) &&
116        isa<Function>(Inst.getOperand(0)))
117      ++OI;  // Skip actual functions for direct function calls.
118    for (; OI != Inst.op_end(); ++OI)
119      if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
120        Pointers.insert(*OI);
121
122    CallSite CS = CallSite::get(&*I);
123    if (CS.getInstruction()) CallSites.insert(CS);
124  }
125
126  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
127      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
128    cerr << "Function: " << F.getName() << ": " << Pointers.size()
129         << " pointers, " << CallSites.size() << " call sites\n";
130
131  // iterate over the worklist, and run the full (n^2)/2 disambiguations
132  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
133       I1 != E; ++I1) {
134    unsigned I1Size = 0;
135    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
136    if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy);
137
138    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
139      unsigned I2Size = 0;
140      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
141      if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy);
142
143      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
144      case AliasAnalysis::NoAlias:
145        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
146        ++NoAlias; break;
147      case AliasAnalysis::MayAlias:
148        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
149        ++MayAlias; break;
150      case AliasAnalysis::MustAlias:
151        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
152        ++MustAlias; break;
153      default:
154        cerr << "Unknown alias query result!\n";
155      }
156    }
157  }
158
159  // Mod/ref alias analysis: compare all pairs of calls and values
160  for (std::set<CallSite>::iterator C = CallSites.begin(),
161         Ce = CallSites.end(); C != Ce; ++C) {
162    Instruction *I = C->getInstruction();
163
164    for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
165         V != Ve; ++V) {
166      unsigned Size = 0;
167      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
168      if (ElTy->isSized()) Size = TD.getTypeSize(ElTy);
169
170      switch (AA.getModRefInfo(*C, *V, Size)) {
171      case AliasAnalysis::NoModRef:
172        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
173        ++NoModRef; break;
174      case AliasAnalysis::Mod:
175        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
176        ++Mod; break;
177      case AliasAnalysis::Ref:
178        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
179        ++Ref; break;
180      case AliasAnalysis::ModRef:
181        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
182        ++ModRef; break;
183      default:
184        cerr << "Unknown alias query result!\n";
185      }
186    }
187  }
188
189  return false;
190}
191
192static void PrintPercent(unsigned Num, unsigned Sum) {
193  cerr << "(" << Num*100ULL/Sum << "."
194            << ((Num*1000ULL/Sum) % 10) << "%)\n";
195}
196
197bool AAEval::doFinalization(Module &M) {
198  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
199  cerr << "===== Alias Analysis Evaluator Report =====\n";
200  if (AliasSum == 0) {
201    cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
202  } else {
203    cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
204    cerr << "  " << NoAlias << " no alias responses ";
205    PrintPercent(NoAlias, AliasSum);
206    cerr << "  " << MayAlias << " may alias responses ";
207    PrintPercent(MayAlias, AliasSum);
208    cerr << "  " << MustAlias << " must alias responses ";
209    PrintPercent(MustAlias, AliasSum);
210    cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
211         << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
212         << MustAlias*100/AliasSum << "%\n";
213  }
214
215  // Display the summary for mod/ref analysis
216  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
217  if (ModRefSum == 0) {
218    cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
219  } else {
220    cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
221    cerr << "  " << NoModRef << " no mod/ref responses ";
222    PrintPercent(NoModRef, ModRefSum);
223    cerr << "  " << Mod << " mod responses ";
224    PrintPercent(Mod, ModRefSum);
225    cerr << "  " << Ref << " ref responses ";
226    PrintPercent(Ref, ModRefSum);
227    cerr << "  " << ModRef << " mod & ref responses ";
228    PrintPercent(ModRef, ModRefSum);
229    cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
230         << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
231         << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
232  }
233
234  return false;
235}
236