/3rd_party/llvm/lib/Analysis/AliasAnalysisEvaluator.cpp

  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/Analysis/Passes.h"
 21#include "llvm/ADT/SetVector.h"
 22#include "llvm/Analysis/AliasAnalysis.h"
 23#include "llvm/Assembly/Writer.h"
 24#include "llvm/IR/Constants.h"
 25#include "llvm/IR/DerivedTypes.h"
 26#include "llvm/IR/Function.h"
 27#include "llvm/IR/Instructions.h"
 28#include "llvm/Pass.h"
 29#include "llvm/Support/CommandLine.h"
 30#include "llvm/Support/Debug.h"
 31#include "llvm/Support/InstIterator.h"
 32#include "llvm/Support/raw_ostream.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
 47static cl::opt<bool> EvalTBAA("evaluate-tbaa", cl::ReallyHidden);
 48
 49namespace {
 50  class AAEval : public FunctionPass {
 51    unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
 52    unsigned NoModRef, Mod, Ref, ModRef;
 53
 54  public:
 55    static char ID; // Pass identification, replacement for typeid
 56    AAEval() : FunctionPass(ID) {
 57      initializeAAEvalPass(*PassRegistry::getPassRegistry());
 58    }
 59
 60    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
 61      AU.addRequired<AliasAnalysis>();
 62      AU.setPreservesAll();
 63    }
 64
 65    bool doInitialization(Module &M) {
 66      NoAlias = MayAlias = PartialAlias = MustAlias = 0;
 67      NoModRef = Mod = Ref = ModRef = 0;
 68
 69      if (PrintAll) {
 70        PrintNoAlias = PrintMayAlias = true;
 71        PrintPartialAlias = PrintMustAlias = true;
 72        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
 73      }
 74      return false;
 75    }
 76
 77    bool runOnFunction(Function &F);
 78    bool doFinalization(Module &M);
 79  };
 80}
 81
 82char AAEval::ID = 0;
 83INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
 84                "Exhaustive Alias Analysis Precision Evaluator", false, true)
 85INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
 86INITIALIZE_PASS_END(AAEval, "aa-eval",
 87                "Exhaustive Alias Analysis Precision Evaluator", false, true)
 88
 89FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
 90
 91static void PrintResults(const char *Msg, bool P, const Value *V1,
 92                         const Value *V2, const Module *M) {
 93  if (P) {
 94    std::string o1, o2;
 95    {
 96      raw_string_ostream os1(o1), os2(o2);
 97      WriteAsOperand(os1, V1, true, M);
 98      WriteAsOperand(os2, V2, true, M);
 99    }
100    
101    if (o2 < o1)
102      std::swap(o1, o2);
103    errs() << "  " << Msg << ":\t"
104           << o1 << ", "
105           << o2 << "\n";
106  }
107}
108
109static inline void
110PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
111                   Module *M) {
112  if (P) {
113    errs() << "  " << Msg << ":  Ptr: ";
114    WriteAsOperand(errs(), Ptr, true, M);
115    errs() << "\t<->" << *I << '\n';
116  }
117}
118
119static inline void
120PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
121                   Module *M) {
122  if (P) {
123    errs() << "  " << Msg << ": " << *CSA.getInstruction()
124           << " <-> " << *CSB.getInstruction() << '\n';
125  }
126}
127
128static inline void
129PrintLoadStoreResults(const char *Msg, bool P, const Value *V1,
130                      const Value *V2, const Module *M) {
131  if (P) {
132    errs() << "  " << Msg << ": " << *V1
133           << " <-> " << *V2 << '\n';
134  }
135}
136
137static inline bool isInterestingPointer(Value *V) {
138  return V->getType()->isPointerTy()
139      && !isa<ConstantPointerNull>(V);
140}
141
142bool AAEval::runOnFunction(Function &F) {
143  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
144
145  SetVector<Value *> Pointers;
146  SetVector<CallSite> CallSites;
147  SetVector<Value *> Loads;
148  SetVector<Value *> Stores;
149
150  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
151    if (I->getType()->isPointerTy())    // Add all pointer arguments.
152      Pointers.insert(I);
153
154  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
155    if (I->getType()->isPointerTy()) // Add all pointer instructions.
156      Pointers.insert(&*I);
157    if (EvalTBAA && isa<LoadInst>(&*I))
158      Loads.insert(&*I);
159    if (EvalTBAA && isa<StoreInst>(&*I))
160      Stores.insert(&*I);
161    Instruction &Inst = *I;
162    if (CallSite CS = cast<Value>(&Inst)) {
163      Value *Callee = CS.getCalledValue();
164      // Skip actual functions for direct function calls.
165      if (!isa<Function>(Callee) && isInterestingPointer(Callee))
166        Pointers.insert(Callee);
167      // Consider formals.
168      for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
169           AI != AE; ++AI)
170        if (isInterestingPointer(*AI))
171          Pointers.insert(*AI);
172      CallSites.insert(CS);
173    } else {
174      // Consider all operands.
175      for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
176           OI != OE; ++OI)
177        if (isInterestingPointer(*OI))
178          Pointers.insert(*OI);
179    }
180  }
181
182  if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
183      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
184    errs() << "Function: " << F.getName() << ": " << Pointers.size()
185           << " pointers, " << CallSites.size() << " call sites\n";
186
187  // iterate over the worklist, and run the full (n^2)/2 disambiguations
188  for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
189       I1 != E; ++I1) {
190    uint64_t I1Size = AliasAnalysis::UnknownSize;
191    Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
192    if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
193
194    for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
195      uint64_t I2Size = AliasAnalysis::UnknownSize;
196      Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
197      if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
198
199      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
200      case AliasAnalysis::NoAlias:
201        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
202        ++NoAlias; break;
203      case AliasAnalysis::MayAlias:
204        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
205        ++MayAlias; break;
206      case AliasAnalysis::PartialAlias:
207        PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
208                     F.getParent());
209        ++PartialAlias; break;
210      case AliasAnalysis::MustAlias:
211        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
212        ++MustAlias; break;
213      }
214    }
215  }
216
217  if (EvalTBAA) {
218    // iterate over all pairs of load, store
219    for (SetVector<Value *>::iterator I1 = Loads.begin(), E = Loads.end();
220         I1 != E; ++I1) {
221      for (SetVector<Value *>::iterator I2 = Stores.begin(), E2 = Stores.end();
222           I2 != E2; ++I2) {
223        switch (AA.alias(AA.getLocation(cast<LoadInst>(*I1)),
224                         AA.getLocation(cast<StoreInst>(*I2)))) {
225        case AliasAnalysis::NoAlias:
226          PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
227                                F.getParent());
228          ++NoAlias; break;
229        case AliasAnalysis::MayAlias:
230          PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
231                                F.getParent());
232          ++MayAlias; break;
233        case AliasAnalysis::PartialAlias:
234          PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
235                                F.getParent());
236          ++PartialAlias; break;
237        case AliasAnalysis::MustAlias:
238          PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
239                                F.getParent());
240          ++MustAlias; break;
241        }
242      }
243    }
244
245    // iterate over all pairs of store, store
246    for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
247         I1 != E; ++I1) {
248      for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
249        switch (AA.alias(AA.getLocation(cast<StoreInst>(*I1)),
250                         AA.getLocation(cast<StoreInst>(*I2)))) {
251        case AliasAnalysis::NoAlias:
252          PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
253                                F.getParent());
254          ++NoAlias; break;
255        case AliasAnalysis::MayAlias:
256          PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
257                                F.getParent());
258          ++MayAlias; break;
259        case AliasAnalysis::PartialAlias:
260          PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
261                                F.getParent());
262          ++PartialAlias; break;
263        case AliasAnalysis::MustAlias:
264          PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
265                                F.getParent());
266          ++MustAlias; break;
267        }
268      }
269    }
270  }
271
272  // Mod/ref alias analysis: compare all pairs of calls and values
273  for (SetVector<CallSite>::iterator C = CallSites.begin(),
274         Ce = CallSites.end(); C != Ce; ++C) {
275    Instruction *I = C->getInstruction();
276
277    for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
278         V != Ve; ++V) {
279      uint64_t Size = AliasAnalysis::UnknownSize;
280      Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
281      if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
282
283      switch (AA.getModRefInfo(*C, *V, Size)) {
284      case AliasAnalysis::NoModRef:
285        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
286        ++NoModRef; break;
287      case AliasAnalysis::Mod:
288        PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
289        ++Mod; break;
290      case AliasAnalysis::Ref:
291        PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
292        ++Ref; break;
293      case AliasAnalysis::ModRef:
294        PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
295        ++ModRef; break;
296      }
297    }
298  }
299
300  // Mod/ref alias analysis: compare all pairs of calls
301  for (SetVector<CallSite>::iterator C = CallSites.begin(),
302         Ce = CallSites.end(); C != Ce; ++C) {
303    for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
304      if (D == C)
305        continue;
306      switch (AA.getModRefInfo(*C, *D)) {
307      case AliasAnalysis::NoModRef:
308        PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
309        ++NoModRef; break;
310      case AliasAnalysis::Mod:
311        PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
312        ++Mod; break;
313      case AliasAnalysis::Ref:
314        PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
315        ++Ref; break;
316      case AliasAnalysis::ModRef:
317        PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
318        ++ModRef; break;
319      }
320    }
321  }
322
323  return false;
324}
325
326static void PrintPercent(unsigned Num, unsigned Sum) {
327  errs() << "(" << Num*100ULL/Sum << "."
328         << ((Num*1000ULL/Sum) % 10) << "%)\n";
329}
330
331bool AAEval::doFinalization(Module &M) {
332  unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
333  errs() << "===== Alias Analysis Evaluator Report =====\n";
334  if (AliasSum == 0) {
335    errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
336  } else {
337    errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
338    errs() << "  " << NoAlias << " no alias responses ";
339    PrintPercent(NoAlias, AliasSum);
340    errs() << "  " << MayAlias << " may alias responses ";
341    PrintPercent(MayAlias, AliasSum);
342    errs() << "  " << PartialAlias << " partial alias responses ";
343    PrintPercent(PartialAlias, AliasSum);
344    errs() << "  " << MustAlias << " must alias responses ";
345    PrintPercent(MustAlias, AliasSum);
346    errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
347           << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
348           << PartialAlias*100/AliasSum << "%/"
349           << MustAlias*100/AliasSum << "%\n";
350  }
351
352  // Display the summary for mod/ref analysis
353  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
354  if (ModRefSum == 0) {
355    errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
356  } else {
357    errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
358    errs() << "  " << NoModRef << " no mod/ref responses ";
359    PrintPercent(NoModRef, ModRefSum);
360    errs() << "  " << Mod << " mod responses ";
361    PrintPercent(Mod, ModRefSum);
362    errs() << "  " << Ref << " ref responses ";
363    PrintPercent(Ref, ModRefSum);
364    errs() << "  " << ModRef << " mod & ref responses ";
365    PrintPercent(ModRef, ModRefSum);
366    errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
367           << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
368           << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
369  }
370
371  return false;
372}