lib/Analysis/AliasAnalysisEvaluator.cpp

   1 //===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by the LLVM research group and is distributed under
   6 // the University of Illinois Open Source 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 <iostream>
  32 #include <set>
  33
  34 using namespace llvm;
  35
  36 namespace {
  37   cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
  38
  39   cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
  40   cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
  41   cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
  42
  43   cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
  44   cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
  45   cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
  46   cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
  47
  48   class AAEval : public FunctionPass {
  49     unsigned NoAlias, MayAlias, MustAlias;
  50     unsigned NoModRef, Mod, Ref, ModRef;
  51
  52   public:
  53     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  54       AU.addRequired<AliasAnalysis>();
  55       AU.setPreservesAll();
  56     }
  57
  58     bool doInitialization(Module &M) {
  59       NoAlias = MayAlias = MustAlias = 0;
  60       NoModRef = Mod = Ref = ModRef = 0;
  61
  62       if (PrintAll) {
  63         PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
  64         PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
  65       }
  66       return false;
  67     }
  68
  69     bool runOnFunction(Function &F);
  70     bool doFinalization(Module &M);
  71   };
  72
  73   RegisterOpt<AAEval>
  74   X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
  75 }
  76
  77 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
  78
  79 static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
  80                                 Module *M) {
  81   if (P) {
  82     std::cerr << "  " << Msg << ":\t";
  83     WriteAsOperand(std::cerr, V1, true, true, M) << ", ";
  84     WriteAsOperand(std::cerr, V2, true, true, M) << "\n";
  85   }
  86 }
  87
  88 static inline void
  89 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
  90                    Module *M) {
  91   if (P) {
  92     std::cerr << "  " << Msg << ":  Ptr: ";
  93     WriteAsOperand(std::cerr, Ptr, true, true, M);
  94     std::cerr << "\t<->" << *I;
  95   }
  96 }
  97
  98 bool AAEval::runOnFunction(Function &F) {
  99   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
 100
 101   const TargetData &TD = AA.getTargetData();
 102
 103   std::set<Value *> Pointers;
 104   std::set<CallSite> CallSites;
 105
 106   for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
 107     if (isa<PointerType>(I->getType()))    // Add all pointer arguments
 108       Pointers.insert(I);
 109
 110   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
 111     if (isa<PointerType>(I->getType())) // Add all pointer instructions
 112       Pointers.insert(&*I);
 113     Instruction &Inst = *I;
 114     User::op_iterator OI = Inst.op_begin();
 115     if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) &&
 116         isa<Function>(Inst.getOperand(0)))
 117       ++OI;  // Skip actual functions for direct function calls.
 118     for (; OI != Inst.op_end(); ++OI)
 119       if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI))
 120         Pointers.insert(*OI);
 121
 122     CallSite CS = CallSite::get(&*I);
 123     if (CS.getInstruction()) CallSites.insert(CS);
 124   }
 125
 126   if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
 127       PrintNoModRef || PrintMod || PrintRef || PrintModRef)
 128     std::cerr << "Function: " << F.getName() << ": " << Pointers.size()
 129               << " pointers, " << CallSites.size() << " call sites\n";
 130
 131   // iterate over the worklist, and run the full (n^2)/2 disambiguations
 132   for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
 133        I1 != E; ++I1) {
 134     unsigned I1Size = 0;
 135     const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
 136     if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy);
 137
 138     for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
 139       unsigned I2Size = 0;
 140       const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
 141       if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy);
 142
 143       switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
 144       case AliasAnalysis::NoAlias:
 145         PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
 146         ++NoAlias; break;
 147       case AliasAnalysis::MayAlias:
 148         PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
 149         ++MayAlias; break;
 150       case AliasAnalysis::MustAlias:
 151         PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
 152         ++MustAlias; break;
 153       default:
 154         std::cerr << "Unknown alias query result!\n";
 155       }
 156     }
 157   }
 158
 159   // Mod/ref alias analysis: compare all pairs of calls and values
 160   for (std::set<CallSite>::iterator C = CallSites.begin(),
 161          Ce = CallSites.end(); C != Ce; ++C) {
 162     Instruction *I = C->getInstruction();
 163
 164     for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
 165          V != Ve; ++V) {
 166       unsigned Size = 0;
 167       const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
 168       if (ElTy->isSized()) Size = TD.getTypeSize(ElTy);
 169
 170       switch (AA.getModRefInfo(*C, *V, Size)) {
 171       case AliasAnalysis::NoModRef:
 172         PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
 173         ++NoModRef; break;
 174       case AliasAnalysis::Mod:
 175         PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
 176         ++Mod; break;
 177       case AliasAnalysis::Ref:
 178         PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
 179         ++Ref; break;
 180       case AliasAnalysis::ModRef:
 181         PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
 182         ++ModRef; break;
 183       default:
 184         std::cerr << "Unknown alias query result!\n";
 185       }
 186     }
 187   }
 188
 189   return false;
 190 }
 191
 192 static void PrintPercent(unsigned Num, unsigned Sum) {
 193   std::cerr << "(" << Num*100ULL/Sum << "."
 194             << ((Num*1000ULL/Sum) % 10) << "%)\n";
 195 }
 196
 197 bool AAEval::doFinalization(Module &M) {
 198   unsigned AliasSum = NoAlias + MayAlias + MustAlias;
 199   std::cerr << "===== Alias Analysis Evaluator Report =====\n";
 200   if (AliasSum == 0) {
 201     std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
 202   } else {
 203     std::cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
 204     std::cerr << "  " << NoAlias << " no alias responses ";
 205     PrintPercent(NoAlias, AliasSum);
 206     std::cerr << "  " << MayAlias << " may alias responses ";
 207     PrintPercent(MayAlias, AliasSum);
 208     std::cerr << "  " << MustAlias << " must alias responses ";
 209     PrintPercent(MustAlias, AliasSum);
 210     std::cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
 211               << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
 212               << MustAlias*100/AliasSum << "%\n";
 213   }
 214
 215   // Display the summary for mod/ref analysis
 216   unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
 217   if (ModRefSum == 0) {
 218     std::cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
 219   } else {
 220     std::cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
 221     std::cerr << "  " << NoModRef << " no mod/ref responses ";
 222     PrintPercent(NoModRef, ModRefSum);
 223     std::cerr << "  " << Mod << " mod responses ";
 224     PrintPercent(Mod, ModRefSum);
 225     std::cerr << "  " << Ref << " ref responses ";
 226     PrintPercent(Ref, ModRefSum);
 227     std::cerr << "  " << ModRef << " mod & ref responses ";
 228     PrintPercent(ModRef, ModRefSum);
 229     std::cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
 230               << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
 231               << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
 232   }
 233
 234   return false;
 235 }