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/Target/TargetData.h"
  29 #include "llvm/Support/InstIterator.h"
  30 #include "llvm/Support/CommandLine.h"
  31 #include "llvm/Support/Compiler.h"
  32 #include "llvm/Support/raw_ostream.h"
  33 #include "llvm/ADT/SetVector.h"
  34 using namespace llvm;
  35
  36 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
  37
  38 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
  39 static cl::opt<bool> PrintMayAlias("print-may-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 VISIBILITY_HIDDEN AAEval : public FunctionPass {
  49     unsigned NoAlias, MayAlias, MustAlias;
  50     unsigned NoModRef, Mod, Ref, ModRef;
  51
  52   public:
  53     static char ID; // Pass identification, replacement for typeid
  54     AAEval() : FunctionPass(&ID) {}
  55
  56     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  57       AU.addRequired<AliasAnalysis>();
  58       AU.setPreservesAll();
  59     }
  60
  61     bool doInitialization(Module &M) {
  62       NoAlias = MayAlias = MustAlias = 0;
  63       NoModRef = Mod = Ref = ModRef = 0;
  64
  65       if (PrintAll) {
  66         PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
  67         PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
  68       }
  69       return false;
  70     }
  71
  72     bool runOnFunction(Function &F);
  73     bool doFinalization(Module &M);
  74   };
  75 }
  76
  77 char AAEval::ID = 0;
  78 static RegisterPass<AAEval>
  79 X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator", false, true);
  80
  81 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
  82
  83 static void PrintResults(const char *Msg, bool P, const Value *V1,
  84                          const Value *V2, const Module *M) {
  85   if (P) {
  86     std::string o1, o2;
  87     {
  88       raw_string_ostream os1(o1), os2(o2);
  89       WriteAsOperand(os1, V1, true, M);
  90       WriteAsOperand(os2, V2, true, M);
  91     }
  92
  93     if (o2 < o1)
  94       std::swap(o1, o2);
  95     errs() << "  " << Msg << ":\t"
  96            << o1 << ", "
  97            << o2 << "\n";
  98   }
  99 }
 100
 101 static inline void
 102 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
 103                    Module *M) {
 104   if (P) {
 105     errs() << "  " << Msg << ":  Ptr: ";
 106     WriteAsOperand(errs(), Ptr, true, M);
 107     errs() << "\t<->" << *I << '\n';
 108   }
 109 }
 110
 111 bool AAEval::runOnFunction(Function &F) {
 112   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
 113
 114   SetVector<Value *> Pointers;
 115   SetVector<CallSite> CallSites;
 116
 117   for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
 118     if (isa<PointerType>(I->getType()))    // Add all pointer arguments
 119       Pointers.insert(I);
 120
 121   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
 122     if (isa<PointerType>(I->getType())) // Add all pointer instructions
 123       Pointers.insert(&*I);
 124     Instruction &Inst = *I;
 125     User::op_iterator OI = Inst.op_begin();
 126     CallSite CS = CallSite::get(&Inst);
 127     if (CS.getInstruction() &&
 128         isa<Function>(CS.getCalledValue()))
 129       ++OI;  // Skip actual functions for direct function calls.
 130     for (; OI != Inst.op_end(); ++OI)
 131       if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
 132         Pointers.insert(*OI);
 133
 134     if (CS.getInstruction()) CallSites.insert(CS);
 135   }
 136
 137   if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
 138       PrintNoModRef || PrintMod || PrintRef || PrintModRef)
 139     errs() << "Function: " << F.getName() << ": " << Pointers.size()
 140            << " pointers, " << CallSites.size() << " call sites\n";
 141
 142   // iterate over the worklist, and run the full (n^2)/2 disambiguations
 143   for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
 144        I1 != E; ++I1) {
 145     unsigned I1Size = ~0u;
 146     const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
 147     if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
 148
 149     for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
 150       unsigned I2Size = ~0u;
 151       const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
 152       if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
 153
 154       switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
 155       case AliasAnalysis::NoAlias:
 156         PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
 157         ++NoAlias; break;
 158       case AliasAnalysis::MayAlias:
 159         PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
 160         ++MayAlias; break;
 161       case AliasAnalysis::MustAlias:
 162         PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
 163         ++MustAlias; break;
 164       default:
 165         errs() << "Unknown alias query result!\n";
 166       }
 167     }
 168   }
 169
 170   // Mod/ref alias analysis: compare all pairs of calls and values
 171   for (SetVector<CallSite>::iterator C = CallSites.begin(),
 172          Ce = CallSites.end(); C != Ce; ++C) {
 173     Instruction *I = C->getInstruction();
 174
 175     for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
 176          V != Ve; ++V) {
 177       unsigned Size = ~0u;
 178       const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
 179       if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
 180
 181       switch (AA.getModRefInfo(*C, *V, Size)) {
 182       case AliasAnalysis::NoModRef:
 183         PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
 184         ++NoModRef; break;
 185       case AliasAnalysis::Mod:
 186         PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
 187         ++Mod; break;
 188       case AliasAnalysis::Ref:
 189         PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
 190         ++Ref; break;
 191       case AliasAnalysis::ModRef:
 192         PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
 193         ++ModRef; break;
 194       default:
 195         errs() << "Unknown alias query result!\n";
 196       }
 197     }
 198   }
 199
 200   return false;
 201 }
 202
 203 static void PrintPercent(unsigned Num, unsigned Sum) {
 204   errs() << "(" << Num*100ULL/Sum << "."
 205          << ((Num*1000ULL/Sum) % 10) << "%)\n";
 206 }
 207
 208 bool AAEval::doFinalization(Module &M) {
 209   unsigned AliasSum = NoAlias + MayAlias + MustAlias;
 210   errs() << "===== Alias Analysis Evaluator Report =====\n";
 211   if (AliasSum == 0) {
 212     errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
 213   } else {
 214     errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
 215     errs() << "  " << NoAlias << " no alias responses ";
 216     PrintPercent(NoAlias, AliasSum);
 217     errs() << "  " << MayAlias << " may alias responses ";
 218     PrintPercent(MayAlias, AliasSum);
 219     errs() << "  " << MustAlias << " must alias responses ";
 220     PrintPercent(MustAlias, AliasSum);
 221     errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
 222            << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
 223            << MustAlias*100/AliasSum << "%\n";
 224   }
 225
 226   // Display the summary for mod/ref analysis
 227   unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
 228   if (ModRefSum == 0) {
 229     errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
 230   } else {
 231     errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
 232     errs() << "  " << NoModRef << " no mod/ref responses ";
 233     PrintPercent(NoModRef, ModRefSum);
 234     errs() << "  " << Mod << " mod responses ";
 235     PrintPercent(Mod, ModRefSum);
 236     errs() << "  " << Ref << " ref responses ";
 237     PrintPercent(Ref, ModRefSum);
 238     errs() << "  " << ModRef << " mod & ref responses ";
 239     PrintPercent(ModRef, ModRefSum);
 240     errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
 241            << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
 242            << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
 243   }
 244
 245   return false;
 246 }