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/Analysis/Passes.h"
21 #include "llvm/ADT/SetVector.h"
22 #include "llvm/Analysis/AliasAnalysis.h"
23 #include "llvm/Assembly/Writer.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/DerivedTypes.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/Pass.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/InstIterator.h"
32 #include "llvm/Support/raw_ostream.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 static cl::opt<bool> EvalTBAA("evaluate-tbaa", cl::ReallyHidden);
48
49 namespace {
50 class AAEval : public FunctionPass {
51 unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
52 unsigned NoModRef, Mod, Ref, ModRef;
53
54 public:
55 static char ID; // Pass identification, replacement for typeid
AAEval()56 AAEval() : FunctionPass(ID) {
57 initializeAAEvalPass(*PassRegistry::getPassRegistry());
58 }
59
getAnalysisUsage(AnalysisUsage & AU) const60 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
61 AU.addRequired<AliasAnalysis>();
62 AU.setPreservesAll();
63 }
64
doInitialization(Module & M)65 bool doInitialization(Module &M) {
66 NoAlias = MayAlias = PartialAlias = MustAlias = 0;
67 NoModRef = Mod = Ref = ModRef = 0;
68
69 if (PrintAll) {
70 PrintNoAlias = PrintMayAlias = true;
71 PrintPartialAlias = PrintMustAlias = true;
72 PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
73 }
74 return false;
75 }
76
77 bool runOnFunction(Function &F);
78 bool doFinalization(Module &M);
79 };
80 }
81
82 char AAEval::ID = 0;
83 INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
84 "Exhaustive Alias Analysis Precision Evaluator", false, true)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)85 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
86 INITIALIZE_PASS_END(AAEval, "aa-eval",
87 "Exhaustive Alias Analysis Precision Evaluator", false, true)
88
89 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
90
PrintResults(const char * Msg,bool P,const Value * V1,const Value * V2,const Module * M)91 static void PrintResults(const char *Msg, bool P, const Value *V1,
92 const Value *V2, const Module *M) {
93 if (P) {
94 std::string o1, o2;
95 {
96 raw_string_ostream os1(o1), os2(o2);
97 WriteAsOperand(os1, V1, true, M);
98 WriteAsOperand(os2, V2, true, M);
99 }
100
101 if (o2 < o1)
102 std::swap(o1, o2);
103 errs() << " " << Msg << ":\t"
104 << o1 << ", "
105 << o2 << "\n";
106 }
107 }
108
109 static inline void
PrintModRefResults(const char * Msg,bool P,Instruction * I,Value * Ptr,Module * M)110 PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
111 Module *M) {
112 if (P) {
113 errs() << " " << Msg << ": Ptr: ";
114 WriteAsOperand(errs(), Ptr, true, M);
115 errs() << "\t<->" << *I << '\n';
116 }
117 }
118
119 static inline void
PrintModRefResults(const char * Msg,bool P,CallSite CSA,CallSite CSB,Module * M)120 PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
121 Module *M) {
122 if (P) {
123 errs() << " " << Msg << ": " << *CSA.getInstruction()
124 << " <-> " << *CSB.getInstruction() << '\n';
125 }
126 }
127
128 static inline void
PrintLoadStoreResults(const char * Msg,bool P,const Value * V1,const Value * V2,const Module * M)129 PrintLoadStoreResults(const char *Msg, bool P, const Value *V1,
130 const Value *V2, const Module *M) {
131 if (P) {
132 errs() << " " << Msg << ": " << *V1
133 << " <-> " << *V2 << '\n';
134 }
135 }
136
isInterestingPointer(Value * V)137 static inline bool isInterestingPointer(Value *V) {
138 return V->getType()->isPointerTy()
139 && !isa<ConstantPointerNull>(V);
140 }
141
runOnFunction(Function & F)142 bool AAEval::runOnFunction(Function &F) {
143 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
144
145 SetVector<Value *> Pointers;
146 SetVector<CallSite> CallSites;
147 SetVector<Value *> Loads;
148 SetVector<Value *> Stores;
149
150 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
151 if (I->getType()->isPointerTy()) // Add all pointer arguments.
152 Pointers.insert(I);
153
154 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
155 if (I->getType()->isPointerTy()) // Add all pointer instructions.
156 Pointers.insert(&*I);
157 if (EvalTBAA && isa<LoadInst>(&*I))
158 Loads.insert(&*I);
159 if (EvalTBAA && isa<StoreInst>(&*I))
160 Stores.insert(&*I);
161 Instruction &Inst = *I;
162 if (CallSite CS = cast<Value>(&Inst)) {
163 Value *Callee = CS.getCalledValue();
164 // Skip actual functions for direct function calls.
165 if (!isa<Function>(Callee) && isInterestingPointer(Callee))
166 Pointers.insert(Callee);
167 // Consider formals.
168 for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
169 AI != AE; ++AI)
170 if (isInterestingPointer(*AI))
171 Pointers.insert(*AI);
172 CallSites.insert(CS);
173 } else {
174 // Consider all operands.
175 for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
176 OI != OE; ++OI)
177 if (isInterestingPointer(*OI))
178 Pointers.insert(*OI);
179 }
180 }
181
182 if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
183 PrintNoModRef || PrintMod || PrintRef || PrintModRef)
184 errs() << "Function: " << F.getName() << ": " << Pointers.size()
185 << " pointers, " << CallSites.size() << " call sites\n";
186
187 // iterate over the worklist, and run the full (n^2)/2 disambiguations
188 for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
189 I1 != E; ++I1) {
190 uint64_t I1Size = AliasAnalysis::UnknownSize;
191 Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
192 if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
193
194 for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
195 uint64_t I2Size = AliasAnalysis::UnknownSize;
196 Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
197 if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
198
199 switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
200 case AliasAnalysis::NoAlias:
201 PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
202 ++NoAlias; break;
203 case AliasAnalysis::MayAlias:
204 PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
205 ++MayAlias; break;
206 case AliasAnalysis::PartialAlias:
207 PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
208 F.getParent());
209 ++PartialAlias; break;
210 case AliasAnalysis::MustAlias:
211 PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
212 ++MustAlias; break;
213 }
214 }
215 }
216
217 if (EvalTBAA) {
218 // iterate over all pairs of load, store
219 for (SetVector<Value *>::iterator I1 = Loads.begin(), E = Loads.end();
220 I1 != E; ++I1) {
221 for (SetVector<Value *>::iterator I2 = Stores.begin(), E2 = Stores.end();
222 I2 != E2; ++I2) {
223 switch (AA.alias(AA.getLocation(cast<LoadInst>(*I1)),
224 AA.getLocation(cast<StoreInst>(*I2)))) {
225 case AliasAnalysis::NoAlias:
226 PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
227 F.getParent());
228 ++NoAlias; break;
229 case AliasAnalysis::MayAlias:
230 PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
231 F.getParent());
232 ++MayAlias; break;
233 case AliasAnalysis::PartialAlias:
234 PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
235 F.getParent());
236 ++PartialAlias; break;
237 case AliasAnalysis::MustAlias:
238 PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
239 F.getParent());
240 ++MustAlias; break;
241 }
242 }
243 }
244
245 // iterate over all pairs of store, store
246 for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
247 I1 != E; ++I1) {
248 for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
249 switch (AA.alias(AA.getLocation(cast<StoreInst>(*I1)),
250 AA.getLocation(cast<StoreInst>(*I2)))) {
251 case AliasAnalysis::NoAlias:
252 PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
253 F.getParent());
254 ++NoAlias; break;
255 case AliasAnalysis::MayAlias:
256 PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
257 F.getParent());
258 ++MayAlias; break;
259 case AliasAnalysis::PartialAlias:
260 PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
261 F.getParent());
262 ++PartialAlias; break;
263 case AliasAnalysis::MustAlias:
264 PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
265 F.getParent());
266 ++MustAlias; break;
267 }
268 }
269 }
270 }
271
272 // Mod/ref alias analysis: compare all pairs of calls and values
273 for (SetVector<CallSite>::iterator C = CallSites.begin(),
274 Ce = CallSites.end(); C != Ce; ++C) {
275 Instruction *I = C->getInstruction();
276
277 for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
278 V != Ve; ++V) {
279 uint64_t Size = AliasAnalysis::UnknownSize;
280 Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
281 if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
282
283 switch (AA.getModRefInfo(*C, *V, Size)) {
284 case AliasAnalysis::NoModRef:
285 PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
286 ++NoModRef; break;
287 case AliasAnalysis::Mod:
288 PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
289 ++Mod; break;
290 case AliasAnalysis::Ref:
291 PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
292 ++Ref; break;
293 case AliasAnalysis::ModRef:
294 PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
295 ++ModRef; break;
296 }
297 }
298 }
299
300 // Mod/ref alias analysis: compare all pairs of calls
301 for (SetVector<CallSite>::iterator C = CallSites.begin(),
302 Ce = CallSites.end(); C != Ce; ++C) {
303 for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
304 if (D == C)
305 continue;
306 switch (AA.getModRefInfo(*C, *D)) {
307 case AliasAnalysis::NoModRef:
308 PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
309 ++NoModRef; break;
310 case AliasAnalysis::Mod:
311 PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
312 ++Mod; break;
313 case AliasAnalysis::Ref:
314 PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
315 ++Ref; break;
316 case AliasAnalysis::ModRef:
317 PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
318 ++ModRef; break;
319 }
320 }
321 }
322
323 return false;
324 }
325
PrintPercent(unsigned Num,unsigned Sum)326 static void PrintPercent(unsigned Num, unsigned Sum) {
327 errs() << "(" << Num*100ULL/Sum << "."
328 << ((Num*1000ULL/Sum) % 10) << "%)\n";
329 }
330
doFinalization(Module & M)331 bool AAEval::doFinalization(Module &M) {
332 unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
333 errs() << "===== Alias Analysis Evaluator Report =====\n";
334 if (AliasSum == 0) {
335 errs() << " Alias Analysis Evaluator Summary: No pointers!\n";
336 } else {
337 errs() << " " << AliasSum << " Total Alias Queries Performed\n";
338 errs() << " " << NoAlias << " no alias responses ";
339 PrintPercent(NoAlias, AliasSum);
340 errs() << " " << MayAlias << " may alias responses ";
341 PrintPercent(MayAlias, AliasSum);
342 errs() << " " << PartialAlias << " partial alias responses ";
343 PrintPercent(PartialAlias, AliasSum);
344 errs() << " " << MustAlias << " must alias responses ";
345 PrintPercent(MustAlias, AliasSum);
346 errs() << " Alias Analysis Evaluator Pointer Alias Summary: "
347 << NoAlias*100/AliasSum << "%/" << MayAlias*100/AliasSum << "%/"
348 << PartialAlias*100/AliasSum << "%/"
349 << MustAlias*100/AliasSum << "%\n";
350 }
351
352 // Display the summary for mod/ref analysis
353 unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
354 if (ModRefSum == 0) {
355 errs() << " Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
356 } else {
357 errs() << " " << ModRefSum << " Total ModRef Queries Performed\n";
358 errs() << " " << NoModRef << " no mod/ref responses ";
359 PrintPercent(NoModRef, ModRefSum);
360 errs() << " " << Mod << " mod responses ";
361 PrintPercent(Mod, ModRefSum);
362 errs() << " " << Ref << " ref responses ";
363 PrintPercent(Ref, ModRefSum);
364 errs() << " " << ModRef << " mod & ref responses ";
365 PrintPercent(ModRef, ModRefSum);
366 errs() << " Alias Analysis Evaluator Mod/Ref Summary: "
367 << NoModRef*100/ModRefSum << "%/" << Mod*100/ModRefSum << "%/"
368 << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
369 }
370
371 return false;
372 }
373