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AliasAnalysisEvaluator.cpp

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00001 //===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements a simple N^2 alias analysis accuracy evaluator.
00011 // Basically, for each function in the program, it simply queries to see how the
00012 // alias analysis implementation answers alias queries between each pair of
00013 // pointers in the function.
00014 //
00015 // This is inspired and adapted from code by: Naveen Neelakantam, Francesco
00016 // Spadini, and Wojciech Stryjewski.
00017 //
00018 //===----------------------------------------------------------------------===//
00019 
00020 #include "llvm/Function.h"
00021 #include "llvm/Instructions.h"
00022 #include "llvm/Pass.h"
00023 #include "llvm/DerivedTypes.h"
00024 #include "llvm/Analysis/AliasAnalysis.h"
00025 #include "llvm/Assembly/Writer.h"
00026 #include "llvm/Target/TargetData.h"
00027 #include "llvm/Support/InstIterator.h"
00028 #include "llvm/Support/CommandLine.h"
00029 #include <iostream>
00030 #include <set>
00031 
00032 using namespace llvm;
00033 
00034 namespace {
00035   cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
00036 
00037   cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
00038   cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
00039   cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
00040 
00041   cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
00042   cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
00043   cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
00044   cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
00045 
00046   class AAEval : public FunctionPass {
00047     unsigned NoAlias, MayAlias, MustAlias;
00048     unsigned NoModRef, Mod, Ref, ModRef;
00049 
00050   public:
00051     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
00052       AU.addRequired<AliasAnalysis>();
00053       AU.setPreservesAll();
00054     }
00055     
00056     bool doInitialization(Module &M) { 
00057       NoAlias = MayAlias = MustAlias = 0; 
00058       NoModRef = Mod = Ref = ModRef = 0;
00059 
00060       if (PrintAll) {
00061         PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
00062         PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
00063       }
00064       return false; 
00065     }
00066 
00067     bool runOnFunction(Function &F);
00068     bool doFinalization(Module &M);
00069   };
00070 
00071   RegisterOpt<AAEval>
00072   X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
00073 }
00074 
00075 static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
00076                                 Module *M) {
00077   if (P) {
00078     std::cerr << "  " << Msg << ":\t";
00079     WriteAsOperand(std::cerr, V1, true, true, M) << ", ";
00080     WriteAsOperand(std::cerr, V2, true, true, M) << "\n";
00081   }
00082 }
00083 
00084 static inline void 
00085 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
00086                    Module *M) {
00087   if (P) {
00088     std::cerr << "  " << Msg << ":  Ptr: ";
00089     WriteAsOperand(std::cerr, Ptr, true, true, M);
00090     std::cerr << "\t<->" << *I;
00091   }
00092 }
00093 
00094 bool AAEval::runOnFunction(Function &F) {
00095   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
00096 
00097   const TargetData &TD = AA.getTargetData();
00098   
00099   std::set<Value *> Pointers;
00100   std::set<CallSite> CallSites;
00101 
00102   for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
00103     if (isa<PointerType>(I->getType()))    // Add all pointer arguments
00104       Pointers.insert(I);
00105 
00106   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
00107     if (isa<PointerType>(I->getType())) // Add all pointer instructions
00108       Pointers.insert(&*I);
00109     for (User::op_iterator OI = (*I).op_begin(); OI != (*I).op_end(); ++OI)
00110       if (isa<PointerType>((*OI)->getType()))
00111         Pointers.insert(*OI);
00112 
00113     CallSite CS = CallSite::get(&*I);
00114     if (CS.getInstruction()) CallSites.insert(CS);
00115   }
00116 
00117   if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
00118       PrintNoModRef || PrintMod || PrintRef || PrintModRef)
00119     std::cerr << "Function: " << F.getName() << ": " << Pointers.size()
00120               << " pointers, " << CallSites.size() << " call sites\n";
00121 
00122   // iterate over the worklist, and run the full (n^2)/2 disambiguations
00123   for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
00124        I1 != E; ++I1) {
00125     unsigned I1Size = 0;
00126     const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
00127     if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy);
00128 
00129     for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
00130       unsigned I2Size = 0;
00131       const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
00132       if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy);
00133 
00134       switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
00135       case AliasAnalysis::NoAlias:
00136         PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
00137         ++NoAlias; break;
00138       case AliasAnalysis::MayAlias:
00139         PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
00140         ++MayAlias; break;
00141       case AliasAnalysis::MustAlias:
00142         PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
00143         ++MustAlias; break;
00144       default:
00145         std::cerr << "Unknown alias query result!\n";
00146       }
00147     }
00148   }
00149 
00150   // Mod/ref alias analysis: compare all pairs of calls and values
00151   for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
00152        V != Ve; ++V) {
00153     unsigned Size = 0;
00154     const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
00155     if (ElTy->isSized()) Size = TD.getTypeSize(ElTy);
00156 
00157     for (std::set<CallSite>::iterator C = CallSites.begin(), 
00158            Ce = CallSites.end(); C != Ce; ++C) {
00159       Instruction *I = C->getInstruction();
00160       switch (AA.getModRefInfo(*C, *V, Size)) {
00161       case AliasAnalysis::NoModRef:
00162         PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
00163         ++NoModRef; break;
00164       case AliasAnalysis::Mod:
00165         PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
00166         ++Mod; break;
00167       case AliasAnalysis::Ref:
00168         PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
00169         ++Ref; break;
00170       case AliasAnalysis::ModRef:
00171         PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
00172         ++ModRef; break;
00173       default:
00174         std::cerr << "Unknown alias query result!\n";
00175       }
00176     }
00177   }
00178 
00179   return false;
00180 }
00181 
00182 bool AAEval::doFinalization(Module &M) {
00183   unsigned AliasSum = NoAlias + MayAlias + MustAlias;
00184   std::cerr << "===== Alias Analysis Evaluator Report =====\n";
00185   if (AliasSum == 0) {
00186     std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
00187   } else { 
00188     std::cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
00189     std::cerr << "  " << NoAlias << " no alias responses (" 
00190               << NoAlias*100/AliasSum << "%)\n";
00191     std::cerr << "  " << MayAlias << " may alias responses (" 
00192               << MayAlias*100/AliasSum << "%)\n";
00193     std::cerr << "  " << MustAlias << " must alias responses (" 
00194               << MustAlias*100/AliasSum <<"%)\n";
00195     std::cerr << "  Alias Analysis Evaluator Pointer Alias Summary: " 
00196               << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/" 
00197               << MustAlias*100/AliasSum << "%\n";
00198   }
00199 
00200   // Display the summary for mod/ref analysis
00201   unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
00202   if (ModRefSum == 0) {
00203     std::cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
00204   } else {
00205     std::cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
00206     std::cerr << "  " << NoModRef << " no mod/ref responses (" 
00207               << NoModRef*100/ModRefSum << "%)\n";
00208     std::cerr << "  " << Mod << " mod responses (" 
00209               << Mod*100/ModRefSum << "%)\n";
00210     std::cerr << "  " << Ref << " ref responses (" 
00211               << Ref*100/ModRefSum <<"%)\n";
00212     std::cerr << "  " << ModRef << " mod & ref responses (" 
00213               << ModRef*100/ModRefSum <<"%)\n";
00214     std::cerr << "  Alias Analysis Evaluator Mod/Ref Summary: " 
00215               << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/" 
00216               << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
00217   }
00218 
00219   return false;
00220 }