AliasAnalysisEvaluator.cpp revision f73e319751bf112e137b3c52d03ca6c872c103e4 
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
37static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
38
39static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
40static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
41static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
42
43static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
44static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
45static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
46static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
47
48namespace {
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(&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    bool runOnFunction(Function &F);
74    bool doFinalization(Module &M);
75  };
76}
77
78char AAEval::ID = 0;
79static RegisterPass<AAEval>
80X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator", false, true);
81
82FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
83
84static void PrintResults(const char *Msg, bool P, const Value *V1, const Value *V2,
85                         const Module *M) {
86  if (P) {
87    std::stringstream s1, s2;
88    WriteAsOperand(s1, V1, true, M);
89    WriteAsOperand(s2, V2, true, M);
90    std::string o1(s1.str()), o2(s2.str());
91    if (o2 < o1)
92        std::swap(o1, o2);
93    cerr << "  " << Msg << ":\t"
94         << o1 << ", "
95         << o2 << "\n";
96  }
97}
98
99static inline void
100PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
101                   Module *M) {
102  if (P) {
103    cerr << "  " << Msg << ":  Ptr: ";
104    WriteAsOperand(*cerr.stream(), Ptr, true, M);
105    cerr << "\t<->" << *I;
106  }
107}
108
109bool AAEval::runOnFunction(Function &F) {
110  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
111
112  const TargetData &TD = AA.getTargetData();
113
114  std::set<Value *> Pointers;
115  std::set<CallSite> CallSites;
116
117  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
118    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
119      Pointers.insert(I);
120
121  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
122    if (isa<PointerType>(I->getType())) // Add all pointer instructions
123      Pointers.insert(&*I);
124    Instruction &Inst = *I;
125    User::op_iterator OI = Inst.op_begin();
126    CallSite CS = CallSite::get(&Inst);
127    if (CS.getInstruction() &&
128        isa<Function>(CS.getCalledValue()))
129      ++OI;  // Skip actual functions for direct function calls.
130    for (; OI != Inst.op_end(); ++OI)
131      if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
132        Pointers.insert(*OI);
133
134    if (CS.getInstruction()) CallSites.insert(CS);
135  }
136
137  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
138      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
139    cerr << "Function: " << F.getName() << ": " << Pointers.size()
140         << " pointers, " << CallSites.size() << " call sites\n";
141
142  // iterate over the worklist, and run the full (n^2)/2 disambiguations
143  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
144       I1 != E; ++I1) {
145    unsigned I1Size = 0;
146    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
147    if (I1ElTy->isSized()) I1Size = TD.getTypeStoreSize(I1ElTy);
148
149    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
150      unsigned I2Size = 0;
151      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
152      if (I2ElTy->isSized()) I2Size = TD.getTypeStoreSize(I2ElTy);
153
154      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
155      case AliasAnalysis::NoAlias:
156        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
157        ++NoAlias; break;
158      case AliasAnalysis::MayAlias:
159        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
160        ++MayAlias; break;
161      case AliasAnalysis::MustAlias:
162        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
163        ++MustAlias; break;
164      default:
165        cerr << "Unknown alias query result!\n";
166      }
167    }
168  }
169
170  // Mod/ref alias analysis: compare all pairs of calls and values
171  for (std::set<CallSite>::iterator C = CallSites.begin(),
172         Ce = CallSites.end(); C != Ce; ++C) {
173    Instruction *I = C->getInstruction();
174
175    for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
176         V != Ve; ++V) {
177      unsigned Size = 0;
178      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
179      if (ElTy->isSized()) Size = TD.getTypeStoreSize(ElTy);
180
181      switch (AA.getModRefInfo(*C, *V, Size)) {
182      case AliasAnalysis::NoModRef:
183        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
184        ++NoModRef; break;
185      case AliasAnalysis::Mod:
186        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
187        ++Mod; break;
188      case AliasAnalysis::Ref:
189        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
190        ++Ref; break;
191      case AliasAnalysis::ModRef:
192        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
193        ++ModRef; break;
194      default:
195        cerr << "Unknown alias query result!\n";
196      }
197    }
198  }
199
200  return false;
201}
202
203static void PrintPercent(unsigned Num, unsigned Sum) {
204  cerr << "(" << Num*100ULL/Sum << "."
205            << ((Num*1000ULL/Sum) % 10) << "%)\n";
206}
207
208bool AAEval::doFinalization(Module &M) {
209  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
210  cerr << "===== Alias Analysis Evaluator Report =====\n";
211  if (AliasSum == 0) {
212    cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
213  } else {
214    cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
215    cerr << "  " << NoAlias << " no alias responses ";
216    PrintPercent(NoAlias, AliasSum);
217    cerr << "  " << MayAlias << " may alias responses ";
218    PrintPercent(MayAlias, AliasSum);
219    cerr << "  " << MustAlias << " must alias responses ";
220    PrintPercent(MustAlias, AliasSum);
221    cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
222         << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
223         << MustAlias*100/AliasSum << "%\n";
224  }
225
226  // Display the summary for mod/ref analysis
227  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
228  if (ModRefSum == 0) {
229    cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
230  } else {
231    cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
232    cerr << "  " << NoModRef << " no mod/ref responses ";
233    PrintPercent(NoModRef, ModRefSum);
234    cerr << "  " << Mod << " mod responses ";
235    PrintPercent(Mod, ModRefSum);
236    cerr << "  " << Ref << " ref responses ";
237    PrintPercent(Ref, ModRefSum);
238    cerr << "  " << ModRef << " mod & ref responses ";
239    PrintPercent(ModRef, ModRefSum);
240    cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
241         << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
242         << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
243  }
244
245  return false;
246}
247