AliasAnalysisEvaluator.cpp revision 3d9f1ca5afd909bfcea243fb27c96013a9134484 
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/Support/Debug.h"
29#include "llvm/Support/InstIterator.h"
30#include "llvm/Support/CommandLine.h"
31#include "llvm/Support/raw_ostream.h"
32#include "llvm/ADT/SetVector.h"
33using namespace llvm;
34
35static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
36
37static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
38static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
39static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
40static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
41
42static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
43static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
44static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
45static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
46
47namespace {
48  class AAEval : public FunctionPass {
49    unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
50    unsigned NoModRef, Mod, Ref, ModRef;
51
52  public:
53    static char ID; // Pass identification, replacement for typeid
54    AAEval() : FunctionPass(ID) {
55      initializeAAEvalPass(*PassRegistry::getPassRegistry());
56    }
57
58    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59      AU.addRequired<AliasAnalysis>();
60      AU.setPreservesAll();
61    }
62
63    bool doInitialization(Module &M) {
64      NoAlias = MayAlias = PartialAlias = MustAlias = 0;
65      NoModRef = Mod = Ref = ModRef = 0;
66
67      if (PrintAll) {
68        PrintNoAlias = PrintMayAlias = true;
69        PrintPartialAlias = PrintMustAlias = true;
70        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
71      }
72      return false;
73    }
74
75    bool runOnFunction(Function &F);
76    bool doFinalization(Module &M);
77  };
78}
79
80char AAEval::ID = 0;
81INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
82                "Exhaustive Alias Analysis Precision Evaluator", false, true)
83INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
84INITIALIZE_PASS_END(AAEval, "aa-eval",
85                "Exhaustive Alias Analysis Precision Evaluator", false, true)
86
87FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
88
89static void PrintResults(const char *Msg, bool P, const Value *V1,
90                         const Value *V2, const Module *M) {
91  if (P) {
92    std::string o1, o2;
93    {
94      raw_string_ostream os1(o1), os2(o2);
95      WriteAsOperand(os1, V1, true, M);
96      WriteAsOperand(os2, V2, true, M);
97    }
98
99    if (o2 < o1)
100      std::swap(o1, o2);
101    errs() << "  " << Msg << ":\t"
102           << o1 << ", "
103           << o2 << "\n";
104  }
105}
106
107static inline void
108PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
109                   Module *M) {
110  if (P) {
111    errs() << "  " << Msg << ":  Ptr: ";
112    WriteAsOperand(errs(), Ptr, true, M);
113    errs() << "\t<->" << *I << '\n';
114  }
115}
116
117static inline void
118PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
119                   Module *M) {
120  if (P) {
121    errs() << "  " << Msg << ": " << *CSA.getInstruction()
122           << " <-> " << *CSB.getInstruction() << '\n';
123  }
124}
125
126static inline bool isInterestingPointer(Value *V) {
127  return V->getType()->isPointerTy()
128      && !isa<ConstantPointerNull>(V);
129}
130
131bool AAEval::runOnFunction(Function &F) {
132  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
133
134  SetVector<Value *> Pointers;
135  SetVector<CallSite> CallSites;
136
137  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
138    if (I->getType()->isPointerTy())    // Add all pointer arguments.
139      Pointers.insert(I);
140
141  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
142    if (I->getType()->isPointerTy()) // Add all pointer instructions.
143      Pointers.insert(&*I);
144    Instruction &Inst = *I;
145    if (CallSite CS = cast<Value>(&Inst)) {
146      Value *Callee = CS.getCalledValue();
147      // Skip actual functions for direct function calls.
148      if (!isa<Function>(Callee) && isInterestingPointer(Callee))
149        Pointers.insert(Callee);
150      // Consider formals.
151      for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
152           AI != AE; ++AI)
153        if (isInterestingPointer(*AI))
154          Pointers.insert(*AI);
155      CallSites.insert(CS);
156    } else {
157      // Consider all operands.
158      for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
159           OI != OE; ++OI)
160        if (isInterestingPointer(*OI))
161          Pointers.insert(*OI);
162    }
163  }
164
165  if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
166      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
167    errs() << "Function: " << F.getName() << ": " << Pointers.size()
168           << " pointers, " << CallSites.size() << " call sites\n";
169
170  // iterate over the worklist, and run the full (n^2)/2 disambiguations
171  for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
172       I1 != E; ++I1) {
173    uint64_t I1Size = AliasAnalysis::UnknownSize;
174    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
175    if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
176
177    for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
178      uint64_t I2Size = AliasAnalysis::UnknownSize;
179      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
180      if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
181
182      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
183      case AliasAnalysis::NoAlias:
184        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
185        ++NoAlias; break;
186      case AliasAnalysis::MayAlias:
187        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
188        ++MayAlias; break;
189      case AliasAnalysis::PartialAlias:
190        PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
191                     F.getParent());
192        ++PartialAlias; break;
193      case AliasAnalysis::MustAlias:
194        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
195        ++MustAlias; break;
196      default:
197        errs() << "Unknown alias query result!\n";
198      }
199    }
200  }
201
202  // Mod/ref alias analysis: compare all pairs of calls and values
203  for (SetVector<CallSite>::iterator C = CallSites.begin(),
204         Ce = CallSites.end(); C != Ce; ++C) {
205    Instruction *I = C->getInstruction();
206
207    for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
208         V != Ve; ++V) {
209      uint64_t Size = AliasAnalysis::UnknownSize;
210      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
211      if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
212
213      switch (AA.getModRefInfo(*C, *V, Size)) {
214      case AliasAnalysis::NoModRef:
215        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
216        ++NoModRef; break;
217      case AliasAnalysis::Mod:
218        PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
219        ++Mod; break;
220      case AliasAnalysis::Ref:
221        PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
222        ++Ref; break;
223      case AliasAnalysis::ModRef:
224        PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
225        ++ModRef; break;
226      default:
227        errs() << "Unknown alias query result!\n";
228      }
229    }
230  }
231
232  // Mod/ref alias analysis: compare all pairs of calls
233  for (SetVector<CallSite>::iterator C = CallSites.begin(),
234         Ce = CallSites.end(); C != Ce; ++C) {
235    for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
236      if (D == C)
237        continue;
238      switch (AA.getModRefInfo(*C, *D)) {
239      case AliasAnalysis::NoModRef:
240        PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
241        ++NoModRef; break;
242      case AliasAnalysis::Mod:
243        PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
244        ++Mod; break;
245      case AliasAnalysis::Ref:
246        PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
247        ++Ref; break;
248      case AliasAnalysis::ModRef:
249        PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
250        ++ModRef; break;
251      }
252    }
253  }
254
255  return false;
256}
257
258static void PrintPercent(unsigned Num, unsigned Sum) {
259  errs() << "(" << Num*100ULL/Sum << "."
260         << ((Num*1000ULL/Sum) % 10) << "%)\n";
261}
262
263bool AAEval::doFinalization(Module &M) {
264  unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
265  errs() << "===== Alias Analysis Evaluator Report =====\n";
266  if (AliasSum == 0) {
267    errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
268  } else {
269    errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
270    errs() << "  " << NoAlias << " no alias responses ";
271    PrintPercent(NoAlias, AliasSum);
272    errs() << "  " << MayAlias << " may alias responses ";
273    PrintPercent(MayAlias, AliasSum);
274    errs() << "  " << PartialAlias << " partial alias responses ";
275    PrintPercent(PartialAlias, AliasSum);
276    errs() << "  " << MustAlias << " must alias responses ";
277    PrintPercent(MustAlias, AliasSum);
278    errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
279           << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
280           << PartialAlias*100/AliasSum << "%/"
281           << MustAlias*100/AliasSum << "%\n";
282  }
283
284  // Display the summary for mod/ref analysis
285  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
286  if (ModRefSum == 0) {
287    errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
288  } else {
289    errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
290    errs() << "  " << NoModRef << " no mod/ref responses ";
291    PrintPercent(NoModRef, ModRefSum);
292    errs() << "  " << Mod << " mod responses ";
293    PrintPercent(Mod, ModRefSum);
294    errs() << "  " << Ref << " ref responses ";
295    PrintPercent(Ref, ModRefSum);
296    errs() << "  " << ModRef << " mod & ref responses ";
297    PrintPercent(ModRef, ModRefSum);
298    errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
299           << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
300           << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
301  }
302
303  return false;
304}
305