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> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
40
41 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
42 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
43 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
44 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
45
46 namespace {
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
AAEval()53 AAEval() : FunctionPass(ID) {}
54
getAnalysisUsage(AnalysisUsage & AU) const55 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
56 AU.addRequired<AliasAnalysis>();
57 AU.setPreservesAll();
58 }
59
doInitialization(Module & M)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
76 char AAEval::ID = 0;
77 INITIALIZE_PASS(AAEval, "aa-eval",
78 "Exhaustive Alias Analysis Precision Evaluator", false, true);
79
createAAEvalPass()80 FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
81
PrintResults(const char * Msg,bool P,const Value * V1,const Value * V2,const Module * M)82 static 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
100 static inline void
PrintModRefResults(const char * Msg,bool P,Instruction * I,Value * Ptr,Module * M)101 PrintModRefResults(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
110 static inline void
PrintModRefResults(const char * Msg,bool P,CallSite CSA,CallSite CSB,Module * M)111 PrintModRefResults(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
isInterestingPointer(Value * V)119 static inline bool isInterestingPointer(Value *V) {
120 return V->getType()->isPointerTy()
121 && !isa<ConstantPointerNull>(V);
122 }
123
runOnFunction(Function & F)124 bool 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
PrintPercent(unsigned Num,unsigned Sum)247 static void PrintPercent(unsigned Num, unsigned Sum) {
248 errs() << "(" << Num*100ULL/Sum << "."
249 << ((Num*1000ULL/Sum) % 10) << "%)\n";
250 }
251
doFinalization(Module & M)252 bool 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