AliasAnalysisEvaluator.cpp revision 1f74590e9d1b9cf0f1f81a156efea73f76546e05 
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> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
40
41static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
42static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
43static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
44static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
45
46namespace {
47  class AAEval : public FunctionPass {
48    unsigned NoAlias, MayAlias, MustAlias;
49    unsigned NoModRef, Mod, Ref, ModRef;
50
51  public:
52    static char ID; // Pass identification, replacement for typeid
53    AAEval() : FunctionPass(&ID) {}
54
55    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
56      AU.addRequired<AliasAnalysis>();
57      AU.setPreservesAll();
58    }
59
60    bool doInitialization(Module &M) {
61      NoAlias = MayAlias = MustAlias = 0;
62      NoModRef = Mod = Ref = ModRef = 0;
63
64      if (PrintAll) {
65        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
66        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
67      }
68      return false;
69    }
70
71    bool runOnFunction(Function &F);
72    bool doFinalization(Module &M);
73  };
74}
75
76char AAEval::ID = 0;
77INITIALIZE_PASS(AAEval, "aa-eval",
78                "Exhaustive Alias Analysis Precision Evaluator", false, true);
79
80FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
81
82static void PrintResults(const char *Msg, bool P, const Value *V1,
83                         const Value *V2, const Module *M) {
84  if (P) {
85    std::string o1, o2;
86    {
87      raw_string_ostream os1(o1), os2(o2);
88      WriteAsOperand(os1, V1, true, M);
89      WriteAsOperand(os2, V2, true, M);
90    }
91
92    if (o2 < o1)
93      std::swap(o1, o2);
94    errs() << "  " << Msg << ":\t"
95           << o1 << ", "
96           << o2 << "\n";
97  }
98}
99
100static inline void
101PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
102                   Module *M) {
103  if (P) {
104    errs() << "  " << Msg << ":  Ptr: ";
105    WriteAsOperand(errs(), Ptr, true, M);
106    errs() << "\t<->" << *I << '\n';
107  }
108}
109
110static inline void
111PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
112                   Module *M) {
113  if (P) {
114    errs() << "  " << Msg << ": " << *CSA.getInstruction()
115           << " <-> " << *CSB.getInstruction() << '\n';
116  }
117}
118
119static inline bool isInterestingPointer(Value *V) {
120  return V->getType()->isPointerTy()
121      && !isa<ConstantPointerNull>(V);
122}
123
124bool AAEval::runOnFunction(Function &F) {
125  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
126
127  SetVector<Value *> Pointers;
128  SetVector<CallSite> CallSites;
129
130  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
131    if (I->getType()->isPointerTy())    // Add all pointer arguments.
132      Pointers.insert(I);
133
134  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
135    if (I->getType()->isPointerTy()) // Add all pointer instructions.
136      Pointers.insert(&*I);
137    Instruction &Inst = *I;
138    if (CallSite CS = cast<Value>(&Inst)) {
139      Value *Callee = CS.getCalledValue();
140      // Skip actual functions for direct function calls.
141      if (!isa<Function>(Callee) && isInterestingPointer(Callee))
142        Pointers.insert(Callee);
143      // Consider formals.
144      for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
145           AI != AE; ++AI)
146        if (isInterestingPointer(*AI))
147          Pointers.insert(*AI);
148      CallSites.insert(CS);
149    } else {
150      // Consider all operands.
151      for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
152           OI != OE; ++OI)
153        if (isInterestingPointer(*OI))
154          Pointers.insert(*OI);
155    }
156  }
157
158  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
159      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
160    errs() << "Function: " << F.getName() << ": " << Pointers.size()
161           << " pointers, " << CallSites.size() << " call sites\n";
162
163  // iterate over the worklist, and run the full (n^2)/2 disambiguations
164  for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
165       I1 != E; ++I1) {
166    unsigned I1Size = ~0u;
167    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
168    if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
169
170    for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
171      unsigned I2Size = ~0u;
172      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
173      if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
174
175      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
176      case AliasAnalysis::NoAlias:
177        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
178        ++NoAlias; break;
179      case AliasAnalysis::MayAlias:
180        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
181        ++MayAlias; break;
182      case AliasAnalysis::MustAlias:
183        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
184        ++MustAlias; break;
185      default:
186        errs() << "Unknown alias query result!\n";
187      }
188    }
189  }
190
191  // Mod/ref alias analysis: compare all pairs of calls and values
192  for (SetVector<CallSite>::iterator C = CallSites.begin(),
193         Ce = CallSites.end(); C != Ce; ++C) {
194    Instruction *I = C->getInstruction();
195
196    for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
197         V != Ve; ++V) {
198      unsigned Size = ~0u;
199      const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
200      if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
201
202      switch (AA.getModRefInfo(*C, *V, Size)) {
203      case AliasAnalysis::NoModRef:
204        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
205        ++NoModRef; break;
206      case AliasAnalysis::Mod:
207        PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
208        ++Mod; break;
209      case AliasAnalysis::Ref:
210        PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
211        ++Ref; break;
212      case AliasAnalysis::ModRef:
213        PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
214        ++ModRef; break;
215      default:
216        errs() << "Unknown alias query result!\n";
217      }
218    }
219  }
220
221  // Mod/ref alias analysis: compare all pairs of calls
222  for (SetVector<CallSite>::iterator C = CallSites.begin(),
223         Ce = CallSites.end(); C != Ce; ++C) {
224    for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
225      if (D == C)
226        continue;
227      switch (AA.getModRefInfo(*C, *D)) {
228      case AliasAnalysis::NoModRef:
229        PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
230        ++NoModRef; break;
231      case AliasAnalysis::Mod:
232        PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
233        ++Mod; break;
234      case AliasAnalysis::Ref:
235        PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
236        ++Ref; break;
237      case AliasAnalysis::ModRef:
238        PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
239        ++ModRef; break;
240      }
241    }
242  }
243
244  return false;
245}
246
247static void PrintPercent(unsigned Num, unsigned Sum) {
248  errs() << "(" << Num*100ULL/Sum << "."
249         << ((Num*1000ULL/Sum) % 10) << "%)\n";
250}
251
252bool AAEval::doFinalization(Module &M) {
253  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
254  errs() << "===== Alias Analysis Evaluator Report =====\n";
255  if (AliasSum == 0) {
256    errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
257  } else {
258    errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
259    errs() << "  " << NoAlias << " no alias responses ";
260    PrintPercent(NoAlias, AliasSum);
261    errs() << "  " << MayAlias << " may alias responses ";
262    PrintPercent(MayAlias, AliasSum);
263    errs() << "  " << MustAlias << " must alias responses ";
264    PrintPercent(MustAlias, AliasSum);
265    errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
266           << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
267           << MustAlias*100/AliasSum << "%\n";
268  }
269
270  // Display the summary for mod/ref analysis
271  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
272  if (ModRefSum == 0) {
273    errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
274  } else {
275    errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
276    errs() << "  " << NoModRef << " no mod/ref responses ";
277    PrintPercent(NoModRef, ModRefSum);
278    errs() << "  " << Mod << " mod responses ";
279    PrintPercent(Mod, ModRefSum);
280    errs() << "  " << Ref << " ref responses ";
281    PrintPercent(Ref, ModRefSum);
282    errs() << "  " << ModRef << " mod & ref responses ";
283    PrintPercent(ModRef, ModRefSum);
284    errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
285           << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
286           << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
287  }
288
289  return false;
290}
291