1 //===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "llvm/Analysis/AliasAnalysisEvaluator.h"
10 #include "llvm/ADT/SetVector.h"
11 #include "llvm/Analysis/AliasAnalysis.h"
12 #include "llvm/IR/Constants.h"
13 #include "llvm/IR/DataLayout.h"
14 #include "llvm/IR/DerivedTypes.h"
15 #include "llvm/IR/Function.h"
16 #include "llvm/IR/InstIterator.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/Module.h"
19 #include "llvm/InitializePasses.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/raw_ostream.h"
24 using namespace llvm;
25 
26 static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
27 
28 static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
29 static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
30 static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
31 static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
32 
33 static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
34 static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
35 static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
36 static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
37 static cl::opt<bool> PrintMust("print-must", cl::ReallyHidden);
38 static cl::opt<bool> PrintMustRef("print-mustref", cl::ReallyHidden);
39 static cl::opt<bool> PrintMustMod("print-mustmod", cl::ReallyHidden);
40 static cl::opt<bool> PrintMustModRef("print-mustmodref", cl::ReallyHidden);
41 
42 static cl::opt<bool> EvalAAMD("evaluate-aa-metadata", cl::ReallyHidden);
43 
44 static void PrintResults(AliasResult AR, bool P, const Value *V1,
45                          const Value *V2, const Module *M) {
46   if (PrintAll || P) {
47     std::string o1, o2;
48     {
49       raw_string_ostream os1(o1), os2(o2);
50       V1->printAsOperand(os1, true, M);
51       V2->printAsOperand(os2, true, M);
52     }
53 
54     if (o2 < o1)
55       std::swap(o1, o2);
56     errs() << "  " << AR << ":\t" << o1 << ", " << o2 << "\n";
57   }
58 }
59 
60 static inline void PrintModRefResults(const char *Msg, bool P, Instruction *I,
61                                       Value *Ptr, Module *M) {
62   if (PrintAll || P) {
63     errs() << "  " << Msg << ":  Ptr: ";
64     Ptr->printAsOperand(errs(), true, M);
65     errs() << "\t<->" << *I << '\n';
66   }
67 }
68 
69 static inline void PrintModRefResults(const char *Msg, bool P, CallBase *CallA,
70                                       CallBase *CallB, Module *M) {
71   if (PrintAll || P) {
72     errs() << "  " << Msg << ": " << *CallA << " <-> " << *CallB << '\n';
73   }
74 }
75 
76 static inline void PrintLoadStoreResults(AliasResult AR, bool P,
77                                          const Value *V1, const Value *V2,
78                                          const Module *M) {
79   if (PrintAll || P) {
80     errs() << "  " << AR << ": " << *V1 << " <-> " << *V2 << '\n';
81   }
82 }
83 
84 static inline bool isInterestingPointer(Value *V) {
85   return V->getType()->isPointerTy()
86       && !isa<ConstantPointerNull>(V);
87 }
88 
89 PreservedAnalyses AAEvaluator::run(Function &F, FunctionAnalysisManager &AM) {
90   runInternal(F, AM.getResult<AAManager>(F));
91   return PreservedAnalyses::all();
92 }
93 
94 void AAEvaluator::runInternal(Function &F, AAResults &AA) {
95   const DataLayout &DL = F.getParent()->getDataLayout();
96 
97   ++FunctionCount;
98 
99   SetVector<Value *> Pointers;
100   SmallSetVector<CallBase *, 16> Calls;
101   SetVector<Value *> Loads;
102   SetVector<Value *> Stores;
103 
104   for (auto &I : F.args())
105     if (I.getType()->isPointerTy())    // Add all pointer arguments.
106       Pointers.insert(&I);
107 
108   for (Instruction &Inst : instructions(F)) {
109     if (Inst.getType()->isPointerTy()) // Add all pointer instructions.
110       Pointers.insert(&Inst);
111     if (EvalAAMD && isa<LoadInst>(&Inst))
112       Loads.insert(&Inst);
113     if (EvalAAMD && isa<StoreInst>(&Inst))
114       Stores.insert(&Inst);
115     if (auto *Call = dyn_cast<CallBase>(&Inst)) {
116       Value *Callee = Call->getCalledOperand();
117       // Skip actual functions for direct function calls.
118       if (!isa<Function>(Callee) && isInterestingPointer(Callee))
119         Pointers.insert(Callee);
120       // Consider formals.
121       for (Use &DataOp : Call->data_ops())
122         if (isInterestingPointer(DataOp))
123           Pointers.insert(DataOp);
124       Calls.insert(Call);
125     } else {
126       // Consider all operands.
127       for (Use &Op : Inst.operands())
128         if (isInterestingPointer(Op))
129           Pointers.insert(Op);
130     }
131   }
132 
133   if (PrintAll || PrintNoAlias || PrintMayAlias || PrintPartialAlias ||
134       PrintMustAlias || PrintNoModRef || PrintMod || PrintRef || PrintModRef)
135     errs() << "Function: " << F.getName() << ": " << Pointers.size()
136            << " pointers, " << Calls.size() << " call sites\n";
137 
138   // iterate over the worklist, and run the full (n^2)/2 disambiguations
139   for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
140        I1 != E; ++I1) {
141     auto I1Size = LocationSize::afterPointer();
142     Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
143     if (I1ElTy->isSized())
144       I1Size = LocationSize::precise(DL.getTypeStoreSize(I1ElTy));
145 
146     for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
147       auto I2Size = LocationSize::afterPointer();
148       Type *I2ElTy = cast<PointerType>((*I2)->getType())->getElementType();
149       if (I2ElTy->isSized())
150         I2Size = LocationSize::precise(DL.getTypeStoreSize(I2ElTy));
151 
152       AliasResult AR = AA.alias(*I1, I1Size, *I2, I2Size);
153       switch (AR) {
154       case NoAlias:
155         PrintResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
156         ++NoAliasCount;
157         break;
158       case MayAlias:
159         PrintResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
160         ++MayAliasCount;
161         break;
162       case PartialAlias:
163         PrintResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
164         ++PartialAliasCount;
165         break;
166       case MustAlias:
167         PrintResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
168         ++MustAliasCount;
169         break;
170       }
171     }
172   }
173 
174   if (EvalAAMD) {
175     // iterate over all pairs of load, store
176     for (Value *Load : Loads) {
177       for (Value *Store : Stores) {
178         AliasResult AR = AA.alias(MemoryLocation::get(cast<LoadInst>(Load)),
179                                   MemoryLocation::get(cast<StoreInst>(Store)));
180         switch (AR) {
181         case NoAlias:
182           PrintLoadStoreResults(AR, PrintNoAlias, Load, Store, F.getParent());
183           ++NoAliasCount;
184           break;
185         case MayAlias:
186           PrintLoadStoreResults(AR, PrintMayAlias, Load, Store, F.getParent());
187           ++MayAliasCount;
188           break;
189         case PartialAlias:
190           PrintLoadStoreResults(AR, PrintPartialAlias, Load, Store, F.getParent());
191           ++PartialAliasCount;
192           break;
193         case MustAlias:
194           PrintLoadStoreResults(AR, PrintMustAlias, Load, Store, F.getParent());
195           ++MustAliasCount;
196           break;
197         }
198       }
199     }
200 
201     // iterate over all pairs of store, store
202     for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
203          I1 != E; ++I1) {
204       for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
205         AliasResult AR = AA.alias(MemoryLocation::get(cast<StoreInst>(*I1)),
206                                   MemoryLocation::get(cast<StoreInst>(*I2)));
207         switch (AR) {
208         case NoAlias:
209           PrintLoadStoreResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
210           ++NoAliasCount;
211           break;
212         case MayAlias:
213           PrintLoadStoreResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
214           ++MayAliasCount;
215           break;
216         case PartialAlias:
217           PrintLoadStoreResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
218           ++PartialAliasCount;
219           break;
220         case MustAlias:
221           PrintLoadStoreResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
222           ++MustAliasCount;
223           break;
224         }
225       }
226     }
227   }
228 
229   // Mod/ref alias analysis: compare all pairs of calls and values
230   for (CallBase *Call : Calls) {
231     for (auto Pointer : Pointers) {
232       auto Size = LocationSize::afterPointer();
233       Type *ElTy = cast<PointerType>(Pointer->getType())->getElementType();
234       if (ElTy->isSized())
235         Size = LocationSize::precise(DL.getTypeStoreSize(ElTy));
236 
237       switch (AA.getModRefInfo(Call, Pointer, Size)) {
238       case ModRefInfo::NoModRef:
239         PrintModRefResults("NoModRef", PrintNoModRef, Call, Pointer,
240                            F.getParent());
241         ++NoModRefCount;
242         break;
243       case ModRefInfo::Mod:
244         PrintModRefResults("Just Mod", PrintMod, Call, Pointer, F.getParent());
245         ++ModCount;
246         break;
247       case ModRefInfo::Ref:
248         PrintModRefResults("Just Ref", PrintRef, Call, Pointer, F.getParent());
249         ++RefCount;
250         break;
251       case ModRefInfo::ModRef:
252         PrintModRefResults("Both ModRef", PrintModRef, Call, Pointer,
253                            F.getParent());
254         ++ModRefCount;
255         break;
256       case ModRefInfo::Must:
257         PrintModRefResults("Must", PrintMust, Call, Pointer, F.getParent());
258         ++MustCount;
259         break;
260       case ModRefInfo::MustMod:
261         PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, Call, Pointer,
262                            F.getParent());
263         ++MustModCount;
264         break;
265       case ModRefInfo::MustRef:
266         PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, Call, Pointer,
267                            F.getParent());
268         ++MustRefCount;
269         break;
270       case ModRefInfo::MustModRef:
271         PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, Call,
272                            Pointer, F.getParent());
273         ++MustModRefCount;
274         break;
275       }
276     }
277   }
278 
279   // Mod/ref alias analysis: compare all pairs of calls
280   for (CallBase *CallA : Calls) {
281     for (CallBase *CallB : Calls) {
282       if (CallA == CallB)
283         continue;
284       switch (AA.getModRefInfo(CallA, CallB)) {
285       case ModRefInfo::NoModRef:
286         PrintModRefResults("NoModRef", PrintNoModRef, CallA, CallB,
287                            F.getParent());
288         ++NoModRefCount;
289         break;
290       case ModRefInfo::Mod:
291         PrintModRefResults("Just Mod", PrintMod, CallA, CallB, F.getParent());
292         ++ModCount;
293         break;
294       case ModRefInfo::Ref:
295         PrintModRefResults("Just Ref", PrintRef, CallA, CallB, F.getParent());
296         ++RefCount;
297         break;
298       case ModRefInfo::ModRef:
299         PrintModRefResults("Both ModRef", PrintModRef, CallA, CallB,
300                            F.getParent());
301         ++ModRefCount;
302         break;
303       case ModRefInfo::Must:
304         PrintModRefResults("Must", PrintMust, CallA, CallB, F.getParent());
305         ++MustCount;
306         break;
307       case ModRefInfo::MustMod:
308         PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, CallA, CallB,
309                            F.getParent());
310         ++MustModCount;
311         break;
312       case ModRefInfo::MustRef:
313         PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, CallA, CallB,
314                            F.getParent());
315         ++MustRefCount;
316         break;
317       case ModRefInfo::MustModRef:
318         PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, CallA,
319                            CallB, F.getParent());
320         ++MustModRefCount;
321         break;
322       }
323     }
324   }
325 }
326 
327 static void PrintPercent(int64_t Num, int64_t Sum) {
328   errs() << "(" << Num * 100LL / Sum << "." << ((Num * 1000LL / Sum) % 10)
329          << "%)\n";
330 }
331 
332 AAEvaluator::~AAEvaluator() {
333   if (FunctionCount == 0)
334     return;
335 
336   int64_t AliasSum =
337       NoAliasCount + MayAliasCount + PartialAliasCount + MustAliasCount;
338   errs() << "===== Alias Analysis Evaluator Report =====\n";
339   if (AliasSum == 0) {
340     errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
341   } else {
342     errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
343     errs() << "  " << NoAliasCount << " no alias responses ";
344     PrintPercent(NoAliasCount, AliasSum);
345     errs() << "  " << MayAliasCount << " may alias responses ";
346     PrintPercent(MayAliasCount, AliasSum);
347     errs() << "  " << PartialAliasCount << " partial alias responses ";
348     PrintPercent(PartialAliasCount, AliasSum);
349     errs() << "  " << MustAliasCount << " must alias responses ";
350     PrintPercent(MustAliasCount, AliasSum);
351     errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
352            << NoAliasCount * 100 / AliasSum << "%/"
353            << MayAliasCount * 100 / AliasSum << "%/"
354            << PartialAliasCount * 100 / AliasSum << "%/"
355            << MustAliasCount * 100 / AliasSum << "%\n";
356   }
357 
358   // Display the summary for mod/ref analysis
359   int64_t ModRefSum = NoModRefCount + RefCount + ModCount + ModRefCount +
360                       MustCount + MustRefCount + MustModCount + MustModRefCount;
361   if (ModRefSum == 0) {
362     errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no "
363               "mod/ref!\n";
364   } else {
365     errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
366     errs() << "  " << NoModRefCount << " no mod/ref responses ";
367     PrintPercent(NoModRefCount, ModRefSum);
368     errs() << "  " << ModCount << " mod responses ";
369     PrintPercent(ModCount, ModRefSum);
370     errs() << "  " << RefCount << " ref responses ";
371     PrintPercent(RefCount, ModRefSum);
372     errs() << "  " << ModRefCount << " mod & ref responses ";
373     PrintPercent(ModRefCount, ModRefSum);
374     errs() << "  " << MustCount << " must responses ";
375     PrintPercent(MustCount, ModRefSum);
376     errs() << "  " << MustModCount << " must mod responses ";
377     PrintPercent(MustModCount, ModRefSum);
378     errs() << "  " << MustRefCount << " must ref responses ";
379     PrintPercent(MustRefCount, ModRefSum);
380     errs() << "  " << MustModRefCount << " must mod & ref responses ";
381     PrintPercent(MustModRefCount, ModRefSum);
382     errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
383            << NoModRefCount * 100 / ModRefSum << "%/"
384            << ModCount * 100 / ModRefSum << "%/" << RefCount * 100 / ModRefSum
385            << "%/" << ModRefCount * 100 / ModRefSum << "%/"
386            << MustCount * 100 / ModRefSum << "%/"
387            << MustRefCount * 100 / ModRefSum << "%/"
388            << MustModCount * 100 / ModRefSum << "%/"
389            << MustModRefCount * 100 / ModRefSum << "%\n";
390   }
391 }
392 
393 namespace llvm {
394 class AAEvalLegacyPass : public FunctionPass {
395   std::unique_ptr<AAEvaluator> P;
396 
397 public:
398   static char ID; // Pass identification, replacement for typeid
399   AAEvalLegacyPass() : FunctionPass(ID) {
400     initializeAAEvalLegacyPassPass(*PassRegistry::getPassRegistry());
401   }
402 
403   void getAnalysisUsage(AnalysisUsage &AU) const override {
404     AU.addRequired<AAResultsWrapperPass>();
405     AU.setPreservesAll();
406   }
407 
408   bool doInitialization(Module &M) override {
409     P.reset(new AAEvaluator());
410     return false;
411   }
412 
413   bool runOnFunction(Function &F) override {
414     P->runInternal(F, getAnalysis<AAResultsWrapperPass>().getAAResults());
415     return false;
416   }
417   bool doFinalization(Module &M) override {
418     P.reset();
419     return false;
420   }
421 };
422 }
423 
424 char AAEvalLegacyPass::ID = 0;
425 INITIALIZE_PASS_BEGIN(AAEvalLegacyPass, "aa-eval",
426                       "Exhaustive Alias Analysis Precision Evaluator", false,
427                       true)
428 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
429 INITIALIZE_PASS_END(AAEvalLegacyPass, "aa-eval",
430                     "Exhaustive Alias Analysis Precision Evaluator", false,
431                     true)
432 
433 FunctionPass *llvm::createAAEvalPass() { return new AAEvalLegacyPass(); }
434