src/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/IR/Constants.h"
  24 #include "llvm/IR/DerivedTypes.h"
  25 #include "llvm/IR/Function.h"
  26 #include "llvm/IR/InstIterator.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/raw_ostream.h"
  32 using namespace llvm;
  33
  34 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
  35
  36 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
  37 static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
  38 static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
  39 static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
  40
  41 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
  42 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
  43 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
  44 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
  45
  46 static cl::opt<bool> EvalAAMD("evaluate-aa-metadata", cl::ReallyHidden);
  47
  48 namespace {
  49   class AAEval : public FunctionPass {
  50     unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
  51     unsigned NoModRef, Mod, Ref, ModRef;
  52
  53   public:
  54     static char ID; // Pass identification, replacement for typeid
  55     AAEval() : FunctionPass(ID) {
  56       initializeAAEvalPass(*PassRegistry::getPassRegistry());
  57     }
  58
  59     void getAnalysisUsage(AnalysisUsage &AU) const override {
  60       AU.addRequired<AliasAnalysis>();
  61       AU.setPreservesAll();
  62     }
  63
  64     bool doInitialization(Module &M) override {
  65       NoAlias = MayAlias = PartialAlias = MustAlias = 0;
  66       NoModRef = Mod = Ref = ModRef = 0;
  67
  68       if (PrintAll) {
  69         PrintNoAlias = PrintMayAlias = true;
  70         PrintPartialAlias = PrintMustAlias = true;
  71         PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
  72       }
  73       return false;
  74     }
  75
  76     bool runOnFunction(Function &F) override;
  77     bool doFinalization(Module &M) override;
  78   };
  79 }
  80
  81 char AAEval::ID = 0;
  82 INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
  83                 "Exhaustive Alias Analysis Precision Evaluator", false, true)
  84 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
  85 INITIALIZE_PASS_END(AAEval, "aa-eval",
  86                 "Exhaustive Alias Analysis Precision Evaluator", false, true)
  87
  88 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
  89
  90 static void PrintResults(const char *Msg, bool P, const Value *V1,
  91                          const Value *V2, const Module *M) {
  92   if (P) {
  93     std::string o1, o2;
  94     {
  95       raw_string_ostream os1(o1), os2(o2);
  96       V1->printAsOperand(os1, true, M);
  97       V2->printAsOperand(os2, true, M);
  98     }
  99
 100     if (o2 < o1)
 101       std::swap(o1, o2);
 102     errs() << "  " << Msg << ":\t"
 103            << o1 << ", "
 104            << o2 << "\n";
 105   }
 106 }
 107
 108 static inline void
 109 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
 110                    Module *M) {
 111   if (P) {
 112     errs() << "  " << Msg << ":  Ptr: ";
 113     Ptr->printAsOperand(errs(), true, M);
 114     errs() << "\t<->" << *I << '\n';
 115   }
 116 }
 117
 118 static inline void
 119 PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
 120                    Module *M) {
 121   if (P) {
 122     errs() << "  " << Msg << ": " << *CSA.getInstruction()
 123            << " <-> " << *CSB.getInstruction() << '\n';
 124   }
 125 }
 126
 127 static inline void
 128 PrintLoadStoreResults(const char *Msg, bool P, const Value *V1,
 129                       const Value *V2, const Module *M) {
 130   if (P) {
 131     errs() << "  " << Msg << ": " << *V1
 132            << " <-> " << *V2 << '\n';
 133   }
 134 }
 135
 136 static inline bool isInterestingPointer(Value *V) {
 137   return V->getType()->isPointerTy()
 138       && !isa<ConstantPointerNull>(V);
 139 }
 140
 141 bool AAEval::runOnFunction(Function &F) {
 142   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
 143
 144   SetVector<Value *> Pointers;
 145   SetVector<CallSite> CallSites;
 146   SetVector<Value *> Loads;
 147   SetVector<Value *> Stores;
 148
 149   for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
 150     if (I->getType()->isPointerTy())    // Add all pointer arguments.
 151       Pointers.insert(I);
 152
 153   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
 154     if (I->getType()->isPointerTy()) // Add all pointer instructions.
 155       Pointers.insert(&*I);
 156     if (EvalAAMD && isa<LoadInst>(&*I))
 157       Loads.insert(&*I);
 158     if (EvalAAMD && isa<StoreInst>(&*I))
 159       Stores.insert(&*I);
 160     Instruction &Inst = *I;
 161     if (CallSite CS = cast<Value>(&Inst)) {
 162       Value *Callee = CS.getCalledValue();
 163       // Skip actual functions for direct function calls.
 164       if (!isa<Function>(Callee) && isInterestingPointer(Callee))
 165         Pointers.insert(Callee);
 166       // Consider formals.
 167       for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
 168            AI != AE; ++AI)
 169         if (isInterestingPointer(*AI))
 170           Pointers.insert(*AI);
 171       CallSites.insert(CS);
 172     } else {
 173       // Consider all operands.
 174       for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
 175            OI != OE; ++OI)
 176         if (isInterestingPointer(*OI))
 177           Pointers.insert(*OI);
 178     }
 179   }
 180
 181   if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
 182       PrintNoModRef || PrintMod || PrintRef || PrintModRef)
 183     errs() << "Function: " << F.getName() << ": " << Pointers.size()
 184            << " pointers, " << CallSites.size() << " call sites\n";
 185
 186   // iterate over the worklist, and run the full (n^2)/2 disambiguations
 187   for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
 188        I1 != E; ++I1) {
 189     uint64_t I1Size = AliasAnalysis::UnknownSize;
 190     Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
 191     if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
 192
 193     for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
 194       uint64_t I2Size = AliasAnalysis::UnknownSize;
 195       Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
 196       if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
 197
 198       switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
 199       case AliasAnalysis::NoAlias:
 200         PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
 201         ++NoAlias; break;
 202       case AliasAnalysis::MayAlias:
 203         PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
 204         ++MayAlias; break;
 205       case AliasAnalysis::PartialAlias:
 206         PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
 207                      F.getParent());
 208         ++PartialAlias; break;
 209       case AliasAnalysis::MustAlias:
 210         PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
 211         ++MustAlias; break;
 212       }
 213     }
 214   }
 215
 216   if (EvalAAMD) {
 217     // iterate over all pairs of load, store
 218     for (SetVector<Value *>::iterator I1 = Loads.begin(), E = Loads.end();
 219          I1 != E; ++I1) {
 220       for (SetVector<Value *>::iterator I2 = Stores.begin(), E2 = Stores.end();
 221            I2 != E2; ++I2) {
 222         switch (AA.alias(AA.getLocation(cast<LoadInst>(*I1)),
 223                          AA.getLocation(cast<StoreInst>(*I2)))) {
 224         case AliasAnalysis::NoAlias:
 225           PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
 226                                 F.getParent());
 227           ++NoAlias; break;
 228         case AliasAnalysis::MayAlias:
 229           PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
 230                                 F.getParent());
 231           ++MayAlias; break;
 232         case AliasAnalysis::PartialAlias:
 233           PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
 234                                 F.getParent());
 235           ++PartialAlias; break;
 236         case AliasAnalysis::MustAlias:
 237           PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
 238                                 F.getParent());
 239           ++MustAlias; break;
 240         }
 241       }
 242     }
 243
 244     // iterate over all pairs of store, store
 245     for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
 246          I1 != E; ++I1) {
 247       for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
 248         switch (AA.alias(AA.getLocation(cast<StoreInst>(*I1)),
 249                          AA.getLocation(cast<StoreInst>(*I2)))) {
 250         case AliasAnalysis::NoAlias:
 251           PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
 252                                 F.getParent());
 253           ++NoAlias; break;
 254         case AliasAnalysis::MayAlias:
 255           PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
 256                                 F.getParent());
 257           ++MayAlias; break;
 258         case AliasAnalysis::PartialAlias:
 259           PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
 260                                 F.getParent());
 261           ++PartialAlias; break;
 262         case AliasAnalysis::MustAlias:
 263           PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
 264                                 F.getParent());
 265           ++MustAlias; break;
 266         }
 267       }
 268     }
 269   }
 270
 271   // Mod/ref alias analysis: compare all pairs of calls and values
 272   for (SetVector<CallSite>::iterator C = CallSites.begin(),
 273          Ce = CallSites.end(); C != Ce; ++C) {
 274     Instruction *I = C->getInstruction();
 275
 276     for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
 277          V != Ve; ++V) {
 278       uint64_t Size = AliasAnalysis::UnknownSize;
 279       Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
 280       if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
 281
 282       switch (AA.getModRefInfo(*C, *V, Size)) {
 283       case AliasAnalysis::NoModRef:
 284         PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
 285         ++NoModRef; break;
 286       case AliasAnalysis::Mod:
 287         PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
 288         ++Mod; break;
 289       case AliasAnalysis::Ref:
 290         PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
 291         ++Ref; break;
 292       case AliasAnalysis::ModRef:
 293         PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
 294         ++ModRef; break;
 295       }
 296     }
 297   }
 298
 299   // Mod/ref alias analysis: compare all pairs of calls
 300   for (SetVector<CallSite>::iterator C = CallSites.begin(),
 301          Ce = CallSites.end(); C != Ce; ++C) {
 302     for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
 303       if (D == C)
 304         continue;
 305       switch (AA.getModRefInfo(*C, *D)) {
 306       case AliasAnalysis::NoModRef:
 307         PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
 308         ++NoModRef; break;
 309       case AliasAnalysis::Mod:
 310         PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
 311         ++Mod; break;
 312       case AliasAnalysis::Ref:
 313         PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
 314         ++Ref; break;
 315       case AliasAnalysis::ModRef:
 316         PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
 317         ++ModRef; break;
 318       }
 319     }
 320   }
 321
 322   return false;
 323 }
 324
 325 static void PrintPercent(unsigned Num, unsigned Sum) {
 326   errs() << "(" << Num*100ULL/Sum << "."
 327          << ((Num*1000ULL/Sum) % 10) << "%)\n";
 328 }
 329
 330 bool AAEval::doFinalization(Module &M) {
 331   unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
 332   errs() << "===== Alias Analysis Evaluator Report =====\n";
 333   if (AliasSum == 0) {
 334     errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
 335   } else {
 336     errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
 337     errs() << "  " << NoAlias << " no alias responses ";
 338     PrintPercent(NoAlias, AliasSum);
 339     errs() << "  " << MayAlias << " may alias responses ";
 340     PrintPercent(MayAlias, AliasSum);
 341     errs() << "  " << PartialAlias << " partial alias responses ";
 342     PrintPercent(PartialAlias, AliasSum);
 343     errs() << "  " << MustAlias << " must alias responses ";
 344     PrintPercent(MustAlias, AliasSum);
 345     errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
 346            << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
 347            << PartialAlias*100/AliasSum << "%/"
 348            << MustAlias*100/AliasSum << "%\n";
 349   }
 350
 351   // Display the summary for mod/ref analysis
 352   unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
 353   if (ModRefSum == 0) {
 354     errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
 355   } else {
 356     errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
 357     errs() << "  " << NoModRef << " no mod/ref responses ";
 358     PrintPercent(NoModRef, ModRefSum);
 359     errs() << "  " << Mod << " mod responses ";
 360     PrintPercent(Mod, ModRefSum);
 361     errs() << "  " << Ref << " ref responses ";
 362     PrintPercent(Ref, ModRefSum);
 363     errs() << "  " << ModRef << " mod & ref responses ";
 364     PrintPercent(ModRef, ModRefSum);
 365     errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
 366            << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
 367            << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
 368   }
 369
 370   return false;
 371 }