AliasAnalysisEvaluator.cpp revision 3e15bf33e024b9df9e89351a165acfdb1dde51ed 
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    static const char ID; // Pass identifcation, replacement for typeid
54    AAEval() : FunctionPass((intptr_t)&ID) {}
55
56    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
57      AU.addRequired<AliasAnalysis>();
58      AU.setPreservesAll();
59    }
60
61    bool doInitialization(Module &M) {
62      NoAlias = MayAlias = MustAlias = 0;
63      NoModRef = Mod = Ref = ModRef = 0;
64
65      if (PrintAll) {
66        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
67        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
68      }
69      return false;
70    }
71
72    bool runOnFunction(Function &F);
73    bool doFinalization(Module &M);
74  };
75
76  const char AAEval::ID = 0;
77  RegisterPass<AAEval>
78  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
79}
80
81FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
82
83static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
84                                Module *M) {
85  if (P) {
86    cerr << "  " << Msg << ":\t";
87    WriteAsOperand(*cerr.stream(), V1, true, M) << ", ";
88    WriteAsOperand(*cerr.stream(), V2, true, M) << "\n";
89  }
90}
91
92static inline void
93PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
94                   Module *M) {
95  if (P) {
96    cerr << "  " << Msg << ":  Ptr: ";
97    WriteAsOperand(*cerr.stream(), Ptr, true, M);
98    cerr << "\t<->" << *I;
99  }
100}
101
102bool AAEval::runOnFunction(Function &F) {
103  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
104
105  const TargetData &TD = AA.getTargetData();
106
107  std::set<Value *> Pointers;
108  std::set<CallSite> CallSites;
109
110  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
111    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
112      Pointers.insert(I);
113
114  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
115    if (isa<PointerType>(I->getType())) // Add all pointer instructions
116      Pointers.insert(&*I);
117    Instruction &Inst = *I;
118    User::op_iterator OI = Inst.op_begin();
119    if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) &&
120        isa<Function>(Inst.getOperand(0)))
121      ++OI;  // Skip actual functions for direct function calls.
122    for (; OI != Inst.op_end(); ++OI)
123      if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
124        Pointers.insert(*OI);
125
126    CallSite CS = CallSite::get(&*I);
127    if (CS.getInstruction()) CallSites.insert(CS);
128  }
129
130  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
131      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
132    cerr << "Function: " << F.getName() << ": " << Pointers.size()
133         << " pointers, " << CallSites.size() << " call sites\n";
134
135  // iterate over the worklist, and run the full (n^2)/2 disambiguations
136  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
137       I1 != E; ++I1) {
138    unsigned I1Size = 0;
139    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
140    if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy);
141
142    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
143      unsigned I2Size = 0;
144      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
145      if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy);
146
147      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
148      case AliasAnalysis::NoAlias:
149        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
150        ++NoAlias; break;
151      case AliasAnalysis::MayAlias:
152        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
153        ++MayAlias; break;
154      case AliasAnalysis::MustAlias:
155        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
156        ++MustAlias; break;
157      default:
158        cerr << "Unknown alias query result!\n";
159      }
160    }
161  }
162
163  // Mod/ref alias analysis: compare all pairs of calls and values
164  for (std::set<CallSite>::iterator C = CallSites.begin(),
165         Ce = CallSites.end(); C != Ce; ++C) {
166    Instruction *I = C->getInstruction();
167
168    for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
169         V != Ve; ++V) {
170      unsigned Size = 0;
171      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
172      if (ElTy->isSized()) Size = TD.getTypeSize(ElTy);
173
174      switch (AA.getModRefInfo(*C, *V, Size)) {
175      case AliasAnalysis::NoModRef:
176        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
177        ++NoModRef; break;
178      case AliasAnalysis::Mod:
179        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
180        ++Mod; break;
181      case AliasAnalysis::Ref:
182        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
183        ++Ref; break;
184      case AliasAnalysis::ModRef:
185        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
186        ++ModRef; break;
187      default:
188        cerr << "Unknown alias query result!\n";
189      }
190    }
191  }
192
193  return false;
194}
195
196static void PrintPercent(unsigned Num, unsigned Sum) {
197  cerr << "(" << Num*100ULL/Sum << "."
198            << ((Num*1000ULL/Sum) % 10) << "%)\n";
199}
200
201bool AAEval::doFinalization(Module &M) {
202  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
203  cerr << "===== Alias Analysis Evaluator Report =====\n";
204  if (AliasSum == 0) {
205    cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
206  } else {
207    cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
208    cerr << "  " << NoAlias << " no alias responses ";
209    PrintPercent(NoAlias, AliasSum);
210    cerr << "  " << MayAlias << " may alias responses ";
211    PrintPercent(MayAlias, AliasSum);
212    cerr << "  " << MustAlias << " must alias responses ";
213    PrintPercent(MustAlias, AliasSum);
214    cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
215         << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
216         << MustAlias*100/AliasSum << "%\n";
217  }
218
219  // Display the summary for mod/ref analysis
220  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
221  if (ModRefSum == 0) {
222    cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
223  } else {
224    cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
225    cerr << "  " << NoModRef << " no mod/ref responses ";
226    PrintPercent(NoModRef, ModRefSum);
227    cerr << "  " << Mod << " mod responses ";
228    PrintPercent(Mod, ModRefSum);
229    cerr << "  " << Ref << " ref responses ";
230    PrintPercent(Ref, ModRefSum);
231    cerr << "  " << ModRef << " mod & ref responses ";
232    PrintPercent(ModRef, ModRefSum);
233    cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
234         << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
235         << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
236  }
237
238  return false;
239}
240