AliasAnalysisEvaluator.cpp revision 3e15bf33e024b9df9e89351a165acfdb1dde51ed
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 "llvm/Support/Compiler.h" 32#include "llvm/Support/Streams.h" 33#include <set> 34using namespace llvm; 35 36namespace { 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 VISIBILITY_HIDDEN AAEval : public FunctionPass { 49 unsigned NoAlias, MayAlias, MustAlias; 50 unsigned NoModRef, Mod, Ref, ModRef; 51 52 public: 53 static const char ID; // Pass identifcation, replacement for typeid 54 AAEval() : FunctionPass((intptr_t)&ID) {} 55 56 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 57 AU.addRequired<AliasAnalysis>(); 58 AU.setPreservesAll(); 59 } 60 61 bool doInitialization(Module &M) { 62 NoAlias = MayAlias = MustAlias = 0; 63 NoModRef = Mod = Ref = ModRef = 0; 64 65 if (PrintAll) { 66 PrintNoAlias = PrintMayAlias = PrintMustAlias = true; 67 PrintNoModRef = PrintMod = PrintRef = PrintModRef = true; 68 } 69 return false; 70 } 71 72 bool runOnFunction(Function &F); 73 bool doFinalization(Module &M); 74 }; 75 76 const char AAEval::ID = 0; 77 RegisterPass<AAEval> 78 X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator"); 79} 80 81FunctionPass *llvm::createAAEvalPass() { return new AAEval(); } 82 83static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2, 84 Module *M) { 85 if (P) { 86 cerr << " " << Msg << ":\t"; 87 WriteAsOperand(*cerr.stream(), V1, true, M) << ", "; 88 WriteAsOperand(*cerr.stream(), V2, true, M) << "\n"; 89 } 90} 91 92static inline void 93PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr, 94 Module *M) { 95 if (P) { 96 cerr << " " << Msg << ": Ptr: "; 97 WriteAsOperand(*cerr.stream(), Ptr, true, M); 98 cerr << "\t<->" << *I; 99 } 100} 101 102bool AAEval::runOnFunction(Function &F) { 103 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 104 105 const TargetData &TD = AA.getTargetData(); 106 107 std::set<Value *> Pointers; 108 std::set<CallSite> CallSites; 109 110 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) 111 if (isa<PointerType>(I->getType())) // Add all pointer arguments 112 Pointers.insert(I); 113 114 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) { 115 if (isa<PointerType>(I->getType())) // Add all pointer instructions 116 Pointers.insert(&*I); 117 Instruction &Inst = *I; 118 User::op_iterator OI = Inst.op_begin(); 119 if ((isa<InvokeInst>(Inst) || isa<CallInst>(Inst)) && 120 isa<Function>(Inst.getOperand(0))) 121 ++OI; // Skip actual functions for direct function calls. 122 for (; OI != Inst.op_end(); ++OI) 123 if (isa<PointerType>((*OI)->getType()) && !isa<ConstantPointerNull>(*OI)) 124 Pointers.insert(*OI); 125 126 CallSite CS = CallSite::get(&*I); 127 if (CS.getInstruction()) CallSites.insert(CS); 128 } 129 130 if (PrintNoAlias || PrintMayAlias || PrintMustAlias || 131 PrintNoModRef || PrintMod || PrintRef || PrintModRef) 132 cerr << "Function: " << F.getName() << ": " << Pointers.size() 133 << " pointers, " << CallSites.size() << " call sites\n"; 134 135 // iterate over the worklist, and run the full (n^2)/2 disambiguations 136 for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end(); 137 I1 != E; ++I1) { 138 unsigned I1Size = 0; 139 const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType(); 140 if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy); 141 142 for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) { 143 unsigned I2Size = 0; 144 const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType(); 145 if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy); 146 147 switch (AA.alias(*I1, I1Size, *I2, I2Size)) { 148 case AliasAnalysis::NoAlias: 149 PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent()); 150 ++NoAlias; break; 151 case AliasAnalysis::MayAlias: 152 PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent()); 153 ++MayAlias; break; 154 case AliasAnalysis::MustAlias: 155 PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent()); 156 ++MustAlias; break; 157 default: 158 cerr << "Unknown alias query result!\n"; 159 } 160 } 161 } 162 163 // Mod/ref alias analysis: compare all pairs of calls and values 164 for (std::set<CallSite>::iterator C = CallSites.begin(), 165 Ce = CallSites.end(); C != Ce; ++C) { 166 Instruction *I = C->getInstruction(); 167 168 for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end(); 169 V != Ve; ++V) { 170 unsigned Size = 0; 171 const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType(); 172 if (ElTy->isSized()) Size = TD.getTypeSize(ElTy); 173 174 switch (AA.getModRefInfo(*C, *V, Size)) { 175 case AliasAnalysis::NoModRef: 176 PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent()); 177 ++NoModRef; break; 178 case AliasAnalysis::Mod: 179 PrintModRefResults(" Mod", PrintMod, I, *V, F.getParent()); 180 ++Mod; break; 181 case AliasAnalysis::Ref: 182 PrintModRefResults(" Ref", PrintRef, I, *V, F.getParent()); 183 ++Ref; break; 184 case AliasAnalysis::ModRef: 185 PrintModRefResults(" ModRef", PrintModRef, I, *V, F.getParent()); 186 ++ModRef; break; 187 default: 188 cerr << "Unknown alias query result!\n"; 189 } 190 } 191 } 192 193 return false; 194} 195 196static void PrintPercent(unsigned Num, unsigned Sum) { 197 cerr << "(" << Num*100ULL/Sum << "." 198 << ((Num*1000ULL/Sum) % 10) << "%)\n"; 199} 200 201bool AAEval::doFinalization(Module &M) { 202 unsigned AliasSum = NoAlias + MayAlias + MustAlias; 203 cerr << "===== Alias Analysis Evaluator Report =====\n"; 204 if (AliasSum == 0) { 205 cerr << " Alias Analysis Evaluator Summary: No pointers!\n"; 206 } else { 207 cerr << " " << AliasSum << " Total Alias Queries Performed\n"; 208 cerr << " " << NoAlias << " no alias responses "; 209 PrintPercent(NoAlias, AliasSum); 210 cerr << " " << MayAlias << " may alias responses "; 211 PrintPercent(MayAlias, AliasSum); 212 cerr << " " << MustAlias << " must alias responses "; 213 PrintPercent(MustAlias, AliasSum); 214 cerr << " Alias Analysis Evaluator Pointer Alias Summary: " 215 << NoAlias*100/AliasSum << "%/" << MayAlias*100/AliasSum << "%/" 216 << MustAlias*100/AliasSum << "%\n"; 217 } 218 219 // Display the summary for mod/ref analysis 220 unsigned ModRefSum = NoModRef + Mod + Ref + ModRef; 221 if (ModRefSum == 0) { 222 cerr << " Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n"; 223 } else { 224 cerr << " " << ModRefSum << " Total ModRef Queries Performed\n"; 225 cerr << " " << NoModRef << " no mod/ref responses "; 226 PrintPercent(NoModRef, ModRefSum); 227 cerr << " " << Mod << " mod responses "; 228 PrintPercent(Mod, ModRefSum); 229 cerr << " " << Ref << " ref responses "; 230 PrintPercent(Ref, ModRefSum); 231 cerr << " " << ModRef << " mod & ref responses "; 232 PrintPercent(ModRef, ModRefSum); 233 cerr << " Alias Analysis Evaluator Mod/Ref Summary: " 234 << NoModRef*100/ModRefSum << "%/" << Mod*100/ModRefSum << "%/" 235 << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n"; 236 } 237 238 return false; 239} 240