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 <set>
  34 #include <sstream>
  35 using namespace llvm;
  36
  37 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
  38
  39 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
  40 static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
  41 static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
  42
  43 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
  44 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
  45 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
  46 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
  47
  48 namespace {
  49   class VISIBILITY_HIDDEN AAEval : public FunctionPass {
  50     unsigned NoAlias, MayAlias, MustAlias;
  51     unsigned NoModRef, Mod, Ref, ModRef;
  52
  53   public:
  54     static char ID; // Pass identification, replacement for typeid
  55     AAEval() : FunctionPass(&ID) {}
  56
  57     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  58       AU.addRequired<AliasAnalysis>();
  59       AU.setPreservesAll();
  60     }
  61
  62     bool doInitialization(Module &M) {
  63       NoAlias = MayAlias = MustAlias = 0;
  64       NoModRef = Mod = Ref = ModRef = 0;
  65
  66       if (PrintAll) {
  67         PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
  68         PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
  69       }
  70       return false;
  71     }
  72
  73     bool runOnFunction(Function &F);
  74     bool doFinalization(Module &M);
  75   };
  76 }
  77
  78 char AAEval::ID = 0;
  79 static RegisterPass<AAEval>
  80 X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator", false, true);
  81
  82 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
  83
  84 static void PrintResults(const char *Msg, bool P, const Value *V1, const Value *V2,
  85                          const Module *M) {
  86   if (P) {
  87     std::stringstream s1, s2;
  88     WriteAsOperand(s1, V1, true, M);
  89     WriteAsOperand(s2, V2, true, M);
  90     std::string o1(s1.str()), o2(s2.str());
  91     if (o2 < o1)
  92       std::swap(o1, o2);
  93     errs() << "  " << Msg << ":\t"
  94            << o1 << ", "
  95            << o2 << "\n";
  96   }
  97 }
  98
  99 static inline void
 100 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
 101                    Module *M) {
 102   if (P) {
 103     errs() << "  " << Msg << ":  Ptr: ";
 104     WriteAsOperand(errs(), Ptr, true, M);
 105     errs() << "\t<->" << *I;
 106   }
 107 }
 108
 109 bool AAEval::runOnFunction(Function &F) {
 110   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
 111
 112   std::set<Value *> Pointers;
 113   std::set<CallSite> CallSites;
 114
 115   for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
 116     if (isa<PointerType>(I->getType()))    // Add all pointer arguments
 117       Pointers.insert(I);
 118
 119   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
 120     if (isa<PointerType>(I->getType())) // Add all pointer instructions
 121       Pointers.insert(&*I);
 122     Instruction &Inst = *I;
 123     User::op_iterator OI = Inst.op_begin();
 124     CallSite CS = CallSite::get(&Inst);
 125     if (CS.getInstruction() &&
 126         isa<Function>(CS.getCalledValue()))
 127       ++OI;  // Skip actual functions for direct function calls.
 128     for (; OI != Inst.op_end(); ++OI)
 129       if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
 130         Pointers.insert(*OI);
 131
 132     if (CS.getInstruction()) CallSites.insert(CS);
 133   }
 134
 135   if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
 136       PrintNoModRef || PrintMod || PrintRef || PrintModRef)
 137     errs() << "Function: " << F.getName() << ": " << Pointers.size()
 138            << " pointers, " << CallSites.size() << " call sites\n";
 139
 140   // iterate over the worklist, and run the full (n^2)/2 disambiguations
 141   for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
 142        I1 != E; ++I1) {
 143     unsigned I1Size = ~0u;
 144     const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
 145     if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
 146
 147     for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
 148       unsigned I2Size = ~0u;
 149       const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
 150       if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
 151
 152       switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
 153       case AliasAnalysis::NoAlias:
 154         PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
 155         ++NoAlias; break;
 156       case AliasAnalysis::MayAlias:
 157         PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
 158         ++MayAlias; break;
 159       case AliasAnalysis::MustAlias:
 160         PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
 161         ++MustAlias; break;
 162       default:
 163         errs() << "Unknown alias query result!\n";
 164       }
 165     }
 166   }
 167
 168   // Mod/ref alias analysis: compare all pairs of calls and values
 169   for (std::set<CallSite>::iterator C = CallSites.begin(),
 170          Ce = CallSites.end(); C != Ce; ++C) {
 171     Instruction *I = C->getInstruction();
 172
 173     for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
 174          V != Ve; ++V) {
 175       unsigned Size = ~0u;
 176       const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
 177       if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
 178
 179       switch (AA.getModRefInfo(*C, *V, Size)) {
 180       case AliasAnalysis::NoModRef:
 181         PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
 182         ++NoModRef; break;
 183       case AliasAnalysis::Mod:
 184         PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
 185         ++Mod; break;
 186       case AliasAnalysis::Ref:
 187         PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
 188         ++Ref; break;
 189       case AliasAnalysis::ModRef:
 190         PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
 191         ++ModRef; break;
 192       default:
 193         errs() << "Unknown alias query result!\n";
 194       }
 195     }
 196   }
 197
 198   return false;
 199 }
 200
 201 static void PrintPercent(unsigned Num, unsigned Sum) {
 202   errs() << "(" << Num*100ULL/Sum << "."
 203          << ((Num*1000ULL/Sum) % 10) << "%)\n";
 204 }
 205
 206 bool AAEval::doFinalization(Module &M) {
 207   unsigned AliasSum = NoAlias + MayAlias + MustAlias;
 208   errs() << "===== Alias Analysis Evaluator Report =====\n";
 209   if (AliasSum == 0) {
 210     errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
 211   } else {
 212     errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
 213     errs() << "  " << NoAlias << " no alias responses ";
 214     PrintPercent(NoAlias, AliasSum);
 215     errs() << "  " << MayAlias << " may alias responses ";
 216     PrintPercent(MayAlias, AliasSum);
 217     errs() << "  " << MustAlias << " must alias responses ";
 218     PrintPercent(MustAlias, AliasSum);
 219     errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
 220            << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
 221            << MustAlias*100/AliasSum << "%\n";
 222   }
 223
 224   // Display the summary for mod/ref analysis
 225   unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
 226   if (ModRefSum == 0) {
 227     errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
 228   } else {
 229     errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
 230     errs() << "  " << NoModRef << " no mod/ref responses ";
 231     PrintPercent(NoModRef, ModRefSum);
 232     errs() << "  " << Mod << " mod responses ";
 233     PrintPercent(Mod, ModRefSum);
 234     errs() << "  " << Ref << " ref responses ";
 235     PrintPercent(Ref, ModRefSum);
 236     errs() << "  " << ModRef << " mod & ref responses ";
 237     PrintPercent(ModRef, ModRefSum);
 238     errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
 239            << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
 240            << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
 241   }
 242
 243   return false;
 244 }