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"
33 using namespace llvm;
34
35 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
36
37 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
38 static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
39 static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
40 static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
41
42 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
43 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
44 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
45 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
46
47 namespace {
48 class AAEval : public FunctionPass {
49 unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
50 unsigned NoModRef, Mod, Ref, ModRef;
51
52 public:
53 static char ID; // Pass identification, replacement for typeid
AAEval()54 AAEval() : FunctionPass(ID) {
55 initializeAAEvalPass(*PassRegistry::getPassRegistry());
56 }
57
getAnalysisUsage(AnalysisUsage & AU) const58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 AU.addRequired<AliasAnalysis>();
60 AU.setPreservesAll();
61 }
62
doInitialization(Module & M)63 bool doInitialization(Module &M) {
64 NoAlias = MayAlias = PartialAlias = MustAlias = 0;
65 NoModRef = Mod = Ref = ModRef = 0;
66
67 if (PrintAll) {
68 PrintNoAlias = PrintMayAlias = true;
69 PrintPartialAlias = PrintMustAlias = true;
70 PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
71 }
72 return false;
73 }
74
75 bool runOnFunction(Function &F);
76 bool doFinalization(Module &M);
77 };
78 }
79
80 char AAEval::ID = 0;
81 INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
82 "Exhaustive Alias Analysis Precision Evaluator", false, true)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)83 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
84 INITIALIZE_PASS_END(AAEval, "aa-eval",
85 "Exhaustive Alias Analysis Precision Evaluator", false, true)
86
87 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
88
PrintResults(const char * Msg,bool P,const Value * V1,const Value * V2,const Module * M)89 static void PrintResults(const char *Msg, bool P, const Value *V1,
90 const Value *V2, const Module *M) {
91 if (P) {
92 std::string o1, o2;
93 {
94 raw_string_ostream os1(o1), os2(o2);
95 WriteAsOperand(os1, V1, true, M);
96 WriteAsOperand(os2, V2, true, M);
97 }
98
99 if (o2 < o1)
100 std::swap(o1, o2);
101 errs() << " " << Msg << ":\t"
102 << o1 << ", "
103 << o2 << "\n";
104 }
105 }
106
107 static inline void
PrintModRefResults(const char * Msg,bool P,Instruction * I,Value * Ptr,Module * M)108 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
109 Module *M) {
110 if (P) {
111 errs() << " " << Msg << ": Ptr: ";
112 WriteAsOperand(errs(), Ptr, true, M);
113 errs() << "\t<->" << *I << '\n';
114 }
115 }
116
117 static inline void
PrintModRefResults(const char * Msg,bool P,CallSite CSA,CallSite CSB,Module * M)118 PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
119 Module *M) {
120 if (P) {
121 errs() << " " << Msg << ": " << *CSA.getInstruction()
122 << " <-> " << *CSB.getInstruction() << '\n';
123 }
124 }
125
isInterestingPointer(Value * V)126 static inline bool isInterestingPointer(Value *V) {
127 return V->getType()->isPointerTy()
128 && !isa<ConstantPointerNull>(V);
129 }
130
runOnFunction(Function & F)131 bool AAEval::runOnFunction(Function &F) {
132 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
133
134 SetVector<Value *> Pointers;
135 SetVector<CallSite> CallSites;
136
137 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
138 if (I->getType()->isPointerTy()) // Add all pointer arguments.
139 Pointers.insert(I);
140
141 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
142 if (I->getType()->isPointerTy()) // Add all pointer instructions.
143 Pointers.insert(&*I);
144 Instruction &Inst = *I;
145 if (CallSite CS = cast<Value>(&Inst)) {
146 Value *Callee = CS.getCalledValue();
147 // Skip actual functions for direct function calls.
148 if (!isa<Function>(Callee) && isInterestingPointer(Callee))
149 Pointers.insert(Callee);
150 // Consider formals.
151 for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
152 AI != AE; ++AI)
153 if (isInterestingPointer(*AI))
154 Pointers.insert(*AI);
155 CallSites.insert(CS);
156 } else {
157 // Consider all operands.
158 for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
159 OI != OE; ++OI)
160 if (isInterestingPointer(*OI))
161 Pointers.insert(*OI);
162 }
163 }
164
165 if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
166 PrintNoModRef || PrintMod || PrintRef || PrintModRef)
167 errs() << "Function: " << F.getName() << ": " << Pointers.size()
168 << " pointers, " << CallSites.size() << " call sites\n";
169
170 // iterate over the worklist, and run the full (n^2)/2 disambiguations
171 for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
172 I1 != E; ++I1) {
173 uint64_t I1Size = AliasAnalysis::UnknownSize;
174 Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
175 if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
176
177 for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
178 uint64_t I2Size = AliasAnalysis::UnknownSize;
179 Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
180 if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
181
182 switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
183 case AliasAnalysis::NoAlias:
184 PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
185 ++NoAlias; break;
186 case AliasAnalysis::MayAlias:
187 PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
188 ++MayAlias; break;
189 case AliasAnalysis::PartialAlias:
190 PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
191 F.getParent());
192 ++PartialAlias; break;
193 case AliasAnalysis::MustAlias:
194 PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
195 ++MustAlias; break;
196 default:
197 errs() << "Unknown alias query result!\n";
198 }
199 }
200 }
201
202 // Mod/ref alias analysis: compare all pairs of calls and values
203 for (SetVector<CallSite>::iterator C = CallSites.begin(),
204 Ce = CallSites.end(); C != Ce; ++C) {
205 Instruction *I = C->getInstruction();
206
207 for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
208 V != Ve; ++V) {
209 uint64_t Size = AliasAnalysis::UnknownSize;
210 Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
211 if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
212
213 switch (AA.getModRefInfo(*C, *V, Size)) {
214 case AliasAnalysis::NoModRef:
215 PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
216 ++NoModRef; break;
217 case AliasAnalysis::Mod:
218 PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
219 ++Mod; break;
220 case AliasAnalysis::Ref:
221 PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
222 ++Ref; break;
223 case AliasAnalysis::ModRef:
224 PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
225 ++ModRef; break;
226 default:
227 errs() << "Unknown alias query result!\n";
228 }
229 }
230 }
231
232 // Mod/ref alias analysis: compare all pairs of calls
233 for (SetVector<CallSite>::iterator C = CallSites.begin(),
234 Ce = CallSites.end(); C != Ce; ++C) {
235 for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
236 if (D == C)
237 continue;
238 switch (AA.getModRefInfo(*C, *D)) {
239 case AliasAnalysis::NoModRef:
240 PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
241 ++NoModRef; break;
242 case AliasAnalysis::Mod:
243 PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
244 ++Mod; break;
245 case AliasAnalysis::Ref:
246 PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
247 ++Ref; break;
248 case AliasAnalysis::ModRef:
249 PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
250 ++ModRef; break;
251 }
252 }
253 }
254
255 return false;
256 }
257
PrintPercent(unsigned Num,unsigned Sum)258 static void PrintPercent(unsigned Num, unsigned Sum) {
259 errs() << "(" << Num*100ULL/Sum << "."
260 << ((Num*1000ULL/Sum) % 10) << "%)\n";
261 }
262
doFinalization(Module & M)263 bool AAEval::doFinalization(Module &M) {
264 unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
265 errs() << "===== Alias Analysis Evaluator Report =====\n";
266 if (AliasSum == 0) {
267 errs() << " Alias Analysis Evaluator Summary: No pointers!\n";
268 } else {
269 errs() << " " << AliasSum << " Total Alias Queries Performed\n";
270 errs() << " " << NoAlias << " no alias responses ";
271 PrintPercent(NoAlias, AliasSum);
272 errs() << " " << MayAlias << " may alias responses ";
273 PrintPercent(MayAlias, AliasSum);
274 errs() << " " << PartialAlias << " partial alias responses ";
275 PrintPercent(PartialAlias, AliasSum);
276 errs() << " " << MustAlias << " must alias responses ";
277 PrintPercent(MustAlias, AliasSum);
278 errs() << " Alias Analysis Evaluator Pointer Alias Summary: "
279 << NoAlias*100/AliasSum << "%/" << MayAlias*100/AliasSum << "%/"
280 << PartialAlias*100/AliasSum << "%/"
281 << MustAlias*100/AliasSum << "%\n";
282 }
283
284 // Display the summary for mod/ref analysis
285 unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
286 if (ModRefSum == 0) {
287 errs() << " Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
288 } else {
289 errs() << " " << ModRefSum << " Total ModRef Queries Performed\n";
290 errs() << " " << NoModRef << " no mod/ref responses ";
291 PrintPercent(NoModRef, ModRefSum);
292 errs() << " " << Mod << " mod responses ";
293 PrintPercent(Mod, ModRefSum);
294 errs() << " " << Ref << " ref responses ";
295 PrintPercent(Ref, ModRefSum);
296 errs() << " " << ModRef << " mod & ref responses ";
297 PrintPercent(ModRef, ModRefSum);
298 errs() << " Alias Analysis Evaluator Mod/Ref Summary: "
299 << NoModRef*100/ModRefSum << "%/" << Mod*100/ModRefSum << "%/"
300 << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
301 }
302
303 return false;
304 }
305