LLVM API Documentation
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 }