AliasAnalysisEvaluator.cpp revision 1cee94f04111cfd7114979d6dfddce2669c9380d 
1//===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// 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>
34#include <sstream>
35using namespace llvm;
36
37namespace {
38  cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
39
40  cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
41  cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
42  cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
43
44  cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
45  cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
46  cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
47  cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
48
49  class VISIBILITY_HIDDEN AAEval : public FunctionPass {
50    unsigned NoAlias, MayAlias, MustAlias;
51    unsigned NoModRef, Mod, Ref, ModRef;
52
53  public:
54    static char ID; // Pass identification, replacement for typeid
55    AAEval() : FunctionPass((intptr_t)&ID) {}
56
57    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
58      AU.addRequired<AliasAnalysis>();
59      AU.setPreservesAll();
60    }
61
62    bool doInitialization(Module &M) {
63      NoAlias = MayAlias = MustAlias = 0;
64      NoModRef = Mod = Ref = ModRef = 0;
65
66      if (PrintAll) {
67        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
68        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
69      }
70      return false;
71    }
72
73    /// isAnalysis - Return true if this pass is  implementing an analysis pass.
74    virtual bool isAnalysis() const { return true; }
75
76    bool runOnFunction(Function &F);
77    bool doFinalization(Module &M);
78  };
79
80  char AAEval::ID = 0;
81  RegisterPass<AAEval>
82  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
83}
84
85FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
86
87static void PrintResults(const char *Msg, bool P, const Value *V1, const Value *V2,
88                         const Module *M) {
89  if (P) {
90    std::stringstream s1, s2;
91    WriteAsOperand(s1, V1, true, M);
92    WriteAsOperand(s2, V2, true, M);
93    std::string o1(s1.str()), o2(s2.str());
94    if (o2 < o1)
95        std::swap(o1, o2);
96    cerr << "  " << Msg << ":\t"
97         << o1 << ", "
98         << o2 << "\n";
99  }
100}
101
102static inline void
103PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
104                   Module *M) {
105  if (P) {
106    cerr << "  " << Msg << ":  Ptr: ";
107    WriteAsOperand(*cerr.stream(), Ptr, true, M);
108    cerr << "\t<->" << *I;
109  }
110}
111
112bool AAEval::runOnFunction(Function &F) {
113  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
114
115  const TargetData &TD = AA.getTargetData();
116
117  std::set<Value *> Pointers;
118  std::set<CallSite> CallSites;
119
120  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
121    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
122      Pointers.insert(I);
123
124  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
125    if (isa<PointerType>(I->getType())) // Add all pointer instructions
126      Pointers.insert(&*I);
127    Instruction &Inst = *I;
128    User::op_iterator OI = Inst.op_begin();
129    if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) &&
130        isa<Function>(Inst.getOperand(0)))
131      ++OI;  // Skip actual functions for direct function calls.
132    for (; OI != Inst.op_end(); ++OI)
133      if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
134        Pointers.insert(*OI);
135
136    CallSite CS = CallSite::get(&*I);
137    if (CS.getInstruction()) CallSites.insert(CS);
138  }
139
140  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
141      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
142    cerr << "Function: " << F.getName() << ": " << Pointers.size()
143         << " pointers, " << CallSites.size() << " call sites\n";
144
145  // iterate over the worklist, and run the full (n^2)/2 disambiguations
146  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
147       I1 != E; ++I1) {
148    unsigned I1Size = 0;
149    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
150    if (I1ElTy->isSized()) I1Size = TD.getTypeStoreSize(I1ElTy);
151
152    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
153      unsigned I2Size = 0;
154      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
155      if (I2ElTy->isSized()) I2Size = TD.getTypeStoreSize(I2ElTy);
156
157      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
158      case AliasAnalysis::NoAlias:
159        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
160        ++NoAlias; break;
161      case AliasAnalysis::MayAlias:
162        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
163        ++MayAlias; break;
164      case AliasAnalysis::MustAlias:
165        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
166        ++MustAlias; break;
167      default:
168        cerr << "Unknown alias query result!\n";
169      }
170    }
171  }
172
173  // Mod/ref alias analysis: compare all pairs of calls and values
174  for (std::set<CallSite>::iterator C = CallSites.begin(),
175         Ce = CallSites.end(); C != Ce; ++C) {
176    Instruction *I = C->getInstruction();
177
178    for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
179         V != Ve; ++V) {
180      unsigned Size = 0;
181      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
182      if (ElTy->isSized()) Size = TD.getTypeStoreSize(ElTy);
183
184      switch (AA.getModRefInfo(*C, *V, Size)) {
185      case AliasAnalysis::NoModRef:
186        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
187        ++NoModRef; break;
188      case AliasAnalysis::Mod:
189        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
190        ++Mod; break;
191      case AliasAnalysis::Ref:
192        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
193        ++Ref; break;
194      case AliasAnalysis::ModRef:
195        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
196        ++ModRef; break;
197      default:
198        cerr << "Unknown alias query result!\n";
199      }
200    }
201  }
202
203  return false;
204}
205
206static void PrintPercent(unsigned Num, unsigned Sum) {
207  cerr << "(" << Num*100ULL/Sum << "."
208            << ((Num*1000ULL/Sum) % 10) << "%)\n";
209}
210
211bool AAEval::doFinalization(Module &M) {
212  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
213  cerr << "===== Alias Analysis Evaluator Report =====\n";
214  if (AliasSum == 0) {
215    cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
216  } else {
217    cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
218    cerr << "  " << NoAlias << " no alias responses ";
219    PrintPercent(NoAlias, AliasSum);
220    cerr << "  " << MayAlias << " may alias responses ";
221    PrintPercent(MayAlias, AliasSum);
222    cerr << "  " << MustAlias << " must alias responses ";
223    PrintPercent(MustAlias, AliasSum);
224    cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
225         << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
226         << MustAlias*100/AliasSum << "%\n";
227  }
228
229  // Display the summary for mod/ref analysis
230  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
231  if (ModRefSum == 0) {
232    cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
233  } else {
234    cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
235    cerr << "  " << NoModRef << " no mod/ref responses ";
236    PrintPercent(NoModRef, ModRefSum);
237    cerr << "  " << Mod << " mod responses ";
238    PrintPercent(Mod, ModRefSum);
239    cerr << "  " << Ref << " ref responses ";
240    PrintPercent(Ref, ModRefSum);
241    cerr << "  " << ModRef << " mod & ref responses ";
242    PrintPercent(ModRef, ModRefSum);
243    cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
244         << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
245         << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
246  }
247
248  return false;
249}
250