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/Constants.h" 00021 #include "llvm/DerivedTypes.h" 00022 #include "llvm/Function.h" 00023 #include "llvm/Instructions.h" 00024 #include "llvm/Pass.h" 00025 #include "llvm/Analysis/Passes.h" 00026 #include "llvm/Analysis/AliasAnalysis.h" 00027 #include "llvm/Assembly/Writer.h" 00028 #include "llvm/Target/TargetData.h" 00029 #include "llvm/Support/InstIterator.h" 00030 #include "llvm/Support/CommandLine.h" 00031 #include <iostream> 00032 #include <set> 00033 00034 using namespace llvm; 00035 00036 namespace { 00037 cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden); 00038 00039 cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden); 00040 cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden); 00041 cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden); 00042 00043 cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden); 00044 cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden); 00045 cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden); 00046 cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden); 00047 00048 class AAEval : public FunctionPass { 00049 unsigned NoAlias, MayAlias, MustAlias; 00050 unsigned NoModRef, Mod, Ref, ModRef; 00051 00052 public: 00053 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 00054 AU.addRequired<AliasAnalysis>(); 00055 AU.setPreservesAll(); 00056 } 00057 00058 bool doInitialization(Module &M) { 00059 NoAlias = MayAlias = MustAlias = 0; 00060 NoModRef = Mod = Ref = ModRef = 0; 00061 00062 if (PrintAll) { 00063 PrintNoAlias = PrintMayAlias = PrintMustAlias = true; 00064 PrintNoModRef = PrintMod = PrintRef = PrintModRef = true; 00065 } 00066 return false; 00067 } 00068 00069 bool runOnFunction(Function &F); 00070 bool doFinalization(Module &M); 00071 }; 00072 00073 RegisterOpt<AAEval> 00074 X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator"); 00075 } 00076 00077 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); } 00078 00079 static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2, 00080 Module *M) { 00081 if (P) { 00082 std::cerr << " " << Msg << ":\t"; 00083 WriteAsOperand(std::cerr, V1, true, true, M) << ", "; 00084 WriteAsOperand(std::cerr, V2, true, true, M) << "\n"; 00085 } 00086 } 00087 00088 static inline void 00089 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr, 00090 Module *M) { 00091 if (P) { 00092 std::cerr << " " << Msg << ": Ptr: "; 00093 WriteAsOperand(std::cerr, Ptr, true, true, M); 00094 std::cerr << "\t<->" << *I; 00095 } 00096 } 00097 00098 bool AAEval::runOnFunction(Function &F) { 00099 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 00100 00101 const TargetData &TD = AA.getTargetData(); 00102 00103 std::set<Value *> Pointers; 00104 std::set<CallSite> CallSites; 00105 00106 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) 00107 if (isa<PointerType>(I->getType())) // Add all pointer arguments 00108 Pointers.insert(I); 00109 00110 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) { 00111 if (isa<PointerType>(I->getType())) // Add all pointer instructions 00112 Pointers.insert(&*I); 00113 Instruction &Inst = *I; 00114 User::op_iterator OI = Inst.op_begin(); 00115 if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) && 00116 isa<Function>(Inst.getOperand(0))) 00117 ++OI; // Skip actual functions for direct function calls. 00118 for (; OI != Inst.op_end(); ++OI) 00119 if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI)) 00120 Pointers.insert(*OI); 00121 00122 CallSite CS = CallSite::get(&*I); 00123 if (CS.getInstruction()) CallSites.insert(CS); 00124 } 00125 00126 if (PrintNoAlias || PrintMayAlias || PrintMustAlias || 00127 PrintNoModRef || PrintMod || PrintRef || PrintModRef) 00128 std::cerr << "Function: " << F.getName() << ": " << Pointers.size() 00129 << " pointers, " << CallSites.size() << " call sites\n"; 00130 00131 // iterate over the worklist, and run the full (n^2)/2 disambiguations 00132 for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end(); 00133 I1 != E; ++I1) { 00134 unsigned I1Size = 0; 00135 const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType(); 00136 if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy); 00137 00138 for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) { 00139 unsigned I2Size = 0; 00140 const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType(); 00141 if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy); 00142 00143 switch (AA.alias(*I1, I1Size, *I2, I2Size)) { 00144 case AliasAnalysis::NoAlias: 00145 PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent()); 00146 ++NoAlias; break; 00147 case AliasAnalysis::MayAlias: 00148 PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent()); 00149 ++MayAlias; break; 00150 case AliasAnalysis::MustAlias: 00151 PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent()); 00152 ++MustAlias; break; 00153 default: 00154 std::cerr << "Unknown alias query result!\n"; 00155 } 00156 } 00157 } 00158 00159 // Mod/ref alias analysis: compare all pairs of calls and values 00160 for (std::set<CallSite>::iterator C = CallSites.begin(), 00161 Ce = CallSites.end(); C != Ce; ++C) { 00162 Instruction *I = C->getInstruction(); 00163 00164 for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end(); 00165 V != Ve; ++V) { 00166 unsigned Size = 0; 00167 const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType(); 00168 if (ElTy->isSized()) Size = TD.getTypeSize(ElTy); 00169 00170 switch (AA.getModRefInfo(*C, *V, Size)) { 00171 case AliasAnalysis::NoModRef: 00172 PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent()); 00173 ++NoModRef; break; 00174 case AliasAnalysis::Mod: 00175 PrintModRefResults(" Mod", PrintMod, I, *V, F.getParent()); 00176 ++Mod; break; 00177 case AliasAnalysis::Ref: 00178 PrintModRefResults(" Ref", PrintRef, I, *V, F.getParent()); 00179 ++Ref; break; 00180 case AliasAnalysis::ModRef: 00181 PrintModRefResults(" ModRef", PrintModRef, I, *V, F.getParent()); 00182 ++ModRef; break; 00183 default: 00184 std::cerr << "Unknown alias query result!\n"; 00185 } 00186 } 00187 } 00188 00189 return false; 00190 } 00191 00192 static void PrintPercent(unsigned Num, unsigned Sum) { 00193 std::cerr << "(" << Num*100ULL/Sum << "." 00194 << ((Num*1000ULL/Sum) % 10) << "%)\n"; 00195 } 00196 00197 bool AAEval::doFinalization(Module &M) { 00198 unsigned AliasSum = NoAlias + MayAlias + MustAlias; 00199 std::cerr << "===== Alias Analysis Evaluator Report =====\n"; 00200 if (AliasSum == 0) { 00201 std::cerr << " Alias Analysis Evaluator Summary: No pointers!\n"; 00202 } else { 00203 std::cerr << " " << AliasSum << " Total Alias Queries Performed\n"; 00204 std::cerr << " " << NoAlias << " no alias responses "; 00205 PrintPercent(NoAlias, AliasSum); 00206 std::cerr << " " << MayAlias << " may alias responses "; 00207 PrintPercent(MayAlias, AliasSum); 00208 std::cerr << " " << MustAlias << " must alias responses "; 00209 PrintPercent(MustAlias, AliasSum); 00210 std::cerr << " Alias Analysis Evaluator Pointer Alias Summary: " 00211 << NoAlias*100/AliasSum << "%/" << MayAlias*100/AliasSum << "%/" 00212 << MustAlias*100/AliasSum << "%\n"; 00213 } 00214 00215 // Display the summary for mod/ref analysis 00216 unsigned ModRefSum = NoModRef + Mod + Ref + ModRef; 00217 if (ModRefSum == 0) { 00218 std::cerr << " Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n"; 00219 } else { 00220 std::cerr << " " << ModRefSum << " Total ModRef Queries Performed\n"; 00221 std::cerr << " " << NoModRef << " no mod/ref responses "; 00222 PrintPercent(NoModRef, ModRefSum); 00223 std::cerr << " " << Mod << " mod responses "; 00224 PrintPercent(Mod, ModRefSum); 00225 std::cerr << " " << Ref << " ref responses "; 00226 PrintPercent(Ref, ModRefSum); 00227 std::cerr << " " << ModRef << " mod & ref responses "; 00228 PrintPercent(ModRef, ModRefSum); 00229 std::cerr << " Alias Analysis Evaluator Mod/Ref Summary: " 00230 << NoModRef*100/ModRefSum << "%/" << Mod*100/ModRefSum << "%/" 00231 << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n"; 00232 } 00233 00234 return false; 00235 }