AliasAnalysisEvaluator.cpp revision 907857d74630430be024cbb67da960147fa7a1d9
1//===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// 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/Support/Debug.h" 29#include "llvm/Support/InstIterator.h" 30#include "llvm/Support/CommandLine.h" 31#include "llvm/Support/raw_ostream.h" 32#include "llvm/ADT/SetVector.h" 33using namespace llvm; 34 35static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden); 36 37static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden); 38static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden); 39static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden); 40 41static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden); 42static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden); 43static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden); 44static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden); 45 46namespace { 47 class AAEval : public FunctionPass { 48 unsigned NoAlias, MayAlias, MustAlias; 49 unsigned NoModRef, Mod, Ref, ModRef; 50 51 public: 52 static char ID; // Pass identification, replacement for typeid 53 AAEval() : FunctionPass(&ID) {} 54 55 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 56 AU.addRequired<AliasAnalysis>(); 57 AU.setPreservesAll(); 58 } 59 60 bool doInitialization(Module &M) { 61 NoAlias = MayAlias = MustAlias = 0; 62 NoModRef = Mod = Ref = ModRef = 0; 63 64 if (PrintAll) { 65 PrintNoAlias = PrintMayAlias = PrintMustAlias = true; 66 PrintNoModRef = PrintMod = PrintRef = PrintModRef = true; 67 } 68 return false; 69 } 70 71 bool runOnFunction(Function &F); 72 bool doFinalization(Module &M); 73 }; 74} 75 76char AAEval::ID = 0; 77INITIALIZE_PASS(AAEval, "aa-eval", 78 "Exhaustive Alias Analysis Precision Evaluator", false, true); 79 80FunctionPass *llvm::createAAEvalPass() { return new AAEval(); } 81 82static void PrintResults(const char *Msg, bool P, const Value *V1, 83 const Value *V2, const Module *M) { 84 if (P) { 85 std::string o1, o2; 86 { 87 raw_string_ostream os1(o1), os2(o2); 88 WriteAsOperand(os1, V1, true, M); 89 WriteAsOperand(os2, V2, true, M); 90 } 91 92 if (o2 < o1) 93 std::swap(o1, o2); 94 errs() << " " << Msg << ":\t" 95 << o1 << ", " 96 << o2 << "\n"; 97 } 98} 99 100static inline void 101PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr, 102 Module *M) { 103 if (P) { 104 errs() << " " << Msg << ": Ptr: "; 105 WriteAsOperand(errs(), Ptr, true, M); 106 errs() << "\t<->" << *I << '\n'; 107 } 108} 109 110static inline void 111PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB, 112 Module *M) { 113 if (P) { 114 errs() << " " << Msg << ": " << *CSA.getInstruction() 115 << " <-> " << *CSB.getInstruction() << '\n'; 116 } 117} 118 119static inline bool isInterestingPointer(Value *V) { 120 return V->getType()->isPointerTy() 121 && !isa<ConstantPointerNull>(V); 122} 123 124bool AAEval::runOnFunction(Function &F) { 125 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 126 127 SetVector<Value *> Pointers; 128 SetVector<CallSite> CallSites; 129 130 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) 131 if (I->getType()->isPointerTy()) // Add all pointer arguments. 132 Pointers.insert(I); 133 134 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) { 135 if (I->getType()->isPointerTy()) // Add all pointer instructions. 136 Pointers.insert(&*I); 137 Instruction &Inst = *I; 138 if (CallSite CS = cast<Value>(&Inst)) { 139 Value *Callee = CS.getCalledValue(); 140 // Skip actual functions for direct function calls. 141 if (!isa<Function>(Callee) && isInterestingPointer(Callee)) 142 Pointers.insert(Callee); 143 // Consider formals. 144 for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end(); 145 AI != AE; ++AI) 146 if (isInterestingPointer(*AI)) 147 Pointers.insert(*AI); 148 CallSites.insert(CS); 149 } else { 150 // Consider all operands. 151 for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end(); 152 OI != OE; ++OI) 153 if (isInterestingPointer(*OI)) 154 Pointers.insert(*OI); 155 } 156 } 157 158 if (PrintNoAlias || PrintMayAlias || PrintMustAlias || 159 PrintNoModRef || PrintMod || PrintRef || PrintModRef) 160 errs() << "Function: " << F.getName() << ": " << Pointers.size() 161 << " pointers, " << CallSites.size() << " call sites\n"; 162 163 // iterate over the worklist, and run the full (n^2)/2 disambiguations 164 for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end(); 165 I1 != E; ++I1) { 166 unsigned I1Size = ~0u; 167 const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType(); 168 if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy); 169 170 for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) { 171 unsigned I2Size = ~0u; 172 const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType(); 173 if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy); 174 175 switch (AA.alias(*I1, I1Size, *I2, I2Size)) { 176 case AliasAnalysis::NoAlias: 177 PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent()); 178 ++NoAlias; break; 179 case AliasAnalysis::MayAlias: 180 PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent()); 181 ++MayAlias; break; 182 case AliasAnalysis::MustAlias: 183 PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent()); 184 ++MustAlias; break; 185 default: 186 errs() << "Unknown alias query result!\n"; 187 } 188 } 189 } 190 191 // Mod/ref alias analysis: compare all pairs of calls and values 192 for (SetVector<CallSite>::iterator C = CallSites.begin(), 193 Ce = CallSites.end(); C != Ce; ++C) { 194 Instruction *I = C->getInstruction(); 195 196 for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end(); 197 V != Ve; ++V) { 198 unsigned Size = ~0u; 199 const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType(); 200 if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy); 201 202 switch (AA.getModRefInfo(*C, *V, Size)) { 203 case AliasAnalysis::NoModRef: 204 PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent()); 205 ++NoModRef; break; 206 case AliasAnalysis::Mod: 207 PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent()); 208 ++Mod; break; 209 case AliasAnalysis::Ref: 210 PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent()); 211 ++Ref; break; 212 case AliasAnalysis::ModRef: 213 PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent()); 214 ++ModRef; break; 215 default: 216 errs() << "Unknown alias query result!\n"; 217 } 218 } 219 } 220 221 // Mod/ref alias analysis: compare all pairs of calls 222 for (SetVector<CallSite>::iterator C = CallSites.begin(), 223 Ce = CallSites.end(); C != Ce; ++C) { 224 for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) { 225 if (D == C) 226 continue; 227 switch (AA.getModRefInfo(*C, *D)) { 228 case AliasAnalysis::NoModRef: 229 PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent()); 230 ++NoModRef; break; 231 case AliasAnalysis::Mod: 232 PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent()); 233 ++Mod; break; 234 case AliasAnalysis::Ref: 235 PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent()); 236 ++Ref; break; 237 case AliasAnalysis::ModRef: 238 PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent()); 239 ++ModRef; break; 240 } 241 } 242 } 243 244 return false; 245} 246 247static void PrintPercent(unsigned Num, unsigned Sum) { 248 errs() << "(" << Num*100ULL/Sum << "." 249 << ((Num*1000ULL/Sum) % 10) << "%)\n"; 250} 251 252bool AAEval::doFinalization(Module &M) { 253 unsigned AliasSum = NoAlias + MayAlias + MustAlias; 254 errs() << "===== Alias Analysis Evaluator Report =====\n"; 255 if (AliasSum == 0) { 256 errs() << " Alias Analysis Evaluator Summary: No pointers!\n"; 257 } else { 258 errs() << " " << AliasSum << " Total Alias Queries Performed\n"; 259 errs() << " " << NoAlias << " no alias responses "; 260 PrintPercent(NoAlias, AliasSum); 261 errs() << " " << MayAlias << " may alias responses "; 262 PrintPercent(MayAlias, AliasSum); 263 errs() << " " << MustAlias << " must alias responses "; 264 PrintPercent(MustAlias, AliasSum); 265 errs() << " Alias Analysis Evaluator Pointer Alias Summary: " 266 << NoAlias*100/AliasSum << "%/" << MayAlias*100/AliasSum << "%/" 267 << MustAlias*100/AliasSum << "%\n"; 268 } 269 270 // Display the summary for mod/ref analysis 271 unsigned ModRefSum = NoModRef + Mod + Ref + ModRef; 272 if (ModRefSum == 0) { 273 errs() << " Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n"; 274 } else { 275 errs() << " " << ModRefSum << " Total ModRef Queries Performed\n"; 276 errs() << " " << NoModRef << " no mod/ref responses "; 277 PrintPercent(NoModRef, ModRefSum); 278 errs() << " " << Mod << " mod responses "; 279 PrintPercent(Mod, ModRefSum); 280 errs() << " " << Ref << " ref responses "; 281 PrintPercent(Ref, ModRefSum); 282 errs() << " " << ModRef << " mod & ref responses "; 283 PrintPercent(ModRef, ModRefSum); 284 errs() << " Alias Analysis Evaluator Mod/Ref Summary: " 285 << NoModRef*100/ModRefSum << "%/" << Mod*100/ModRefSum << "%/" 286 << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n"; 287 } 288 289 return false; 290} 291