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/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"
  33 using namespace llvm;
  34
  35 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
  36
  37 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
  38 static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
  39 static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
  40 static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
  41
  42 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
  43 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
  44 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
  45 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
  46
  47 namespace {
  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
  80 char AAEval::ID = 0;
  81 INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
  82                 "Exhaustive Alias Analysis Precision Evaluator", false, true)
  83 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
  84 INITIALIZE_PASS_END(AAEval, "aa-eval",
  85                 "Exhaustive Alias Analysis Precision Evaluator", false, true)
  86
  87 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
  88
  89 static 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
 107 static inline void
 108 PrintModRefResults(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
 117 static inline void
 118 PrintModRefResults(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
 126 static inline bool isInterestingPointer(Value *V) {
 127   return V->getType()->isPointerTy()
 128       && !isa<ConstantPointerNull>(V);
 129 }
 130
 131 bool 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
 258 static void PrintPercent(unsigned Num, unsigned Sum) {
 259   errs() << "(" << Num*100ULL/Sum << "."
 260          << ((Num*1000ULL/Sum) % 10) << "%)\n";
 261 }
 262
 263 bool 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 }