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 
PrintResults(AliasResult AR,bool P,const Value * V1,const Value * V2,const Module * M)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       // Change offset sign for the local AR, for printing only.
57       AR.swap();
58     }
59     errs() << "  " << AR << ":\t" << o1 << ", " << o2 << "\n";
60   }
61 }
62 
PrintModRefResults(const char * Msg,bool P,Instruction * I,Value * Ptr,Module * M)63 static inline void PrintModRefResults(const char *Msg, bool P, Instruction *I,
64                                       Value *Ptr, Module *M) {
65   if (PrintAll || P) {
66     errs() << "  " << Msg << ":  Ptr: ";
67     Ptr->printAsOperand(errs(), true, M);
68     errs() << "\t<->" << *I << '\n';
69   }
70 }
71 
PrintModRefResults(const char * Msg,bool P,CallBase * CallA,CallBase * CallB,Module * M)72 static inline void PrintModRefResults(const char *Msg, bool P, CallBase *CallA,
73                                       CallBase *CallB, Module *M) {
74   if (PrintAll || P) {
75     errs() << "  " << Msg << ": " << *CallA << " <-> " << *CallB << '\n';
76   }
77 }
78 
PrintLoadStoreResults(AliasResult AR,bool P,const Value * V1,const Value * V2,const Module * M)79 static inline void PrintLoadStoreResults(AliasResult AR, bool P,
80                                          const Value *V1, const Value *V2,
81                                          const Module *M) {
82   if (PrintAll || P) {
83     errs() << "  " << AR << ": " << *V1 << " <-> " << *V2 << '\n';
84   }
85 }
86 
isInterestingPointer(Value * V)87 static inline bool isInterestingPointer(Value *V) {
88   return V->getType()->isPointerTy()
89       && !isa<ConstantPointerNull>(V);
90 }
91 
run(Function & F,FunctionAnalysisManager & AM)92 PreservedAnalyses AAEvaluator::run(Function &F, FunctionAnalysisManager &AM) {
93   runInternal(F, AM.getResult<AAManager>(F));
94   return PreservedAnalyses::all();
95 }
96 
runInternal(Function & F,AAResults & AA)97 void AAEvaluator::runInternal(Function &F, AAResults &AA) {
98   const DataLayout &DL = F.getParent()->getDataLayout();
99 
100   ++FunctionCount;
101 
102   SetVector<Value *> Pointers;
103   SmallSetVector<CallBase *, 16> Calls;
104   SetVector<Value *> Loads;
105   SetVector<Value *> Stores;
106 
107   for (auto &I : F.args())
108     if (I.getType()->isPointerTy())    // Add all pointer arguments.
109       Pointers.insert(&I);
110 
111   for (Instruction &Inst : instructions(F)) {
112     if (Inst.getType()->isPointerTy()) // Add all pointer instructions.
113       Pointers.insert(&Inst);
114     if (EvalAAMD && isa<LoadInst>(&Inst))
115       Loads.insert(&Inst);
116     if (EvalAAMD && isa<StoreInst>(&Inst))
117       Stores.insert(&Inst);
118     if (auto *Call = dyn_cast<CallBase>(&Inst)) {
119       Value *Callee = Call->getCalledOperand();
120       // Skip actual functions for direct function calls.
121       if (!isa<Function>(Callee) && isInterestingPointer(Callee))
122         Pointers.insert(Callee);
123       // Consider formals.
124       for (Use &DataOp : Call->data_ops())
125         if (isInterestingPointer(DataOp))
126           Pointers.insert(DataOp);
127       Calls.insert(Call);
128     } else {
129       // Consider all operands.
130       for (Use &Op : Inst.operands())
131         if (isInterestingPointer(Op))
132           Pointers.insert(Op);
133     }
134   }
135 
136   if (PrintAll || PrintNoAlias || PrintMayAlias || PrintPartialAlias ||
137       PrintMustAlias || PrintNoModRef || PrintMod || PrintRef || PrintModRef)
138     errs() << "Function: " << F.getName() << ": " << Pointers.size()
139            << " pointers, " << Calls.size() << " call sites\n";
140 
141   // iterate over the worklist, and run the full (n^2)/2 disambiguations
142   for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
143        I1 != E; ++I1) {
144     auto I1Size = LocationSize::afterPointer();
145     Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
146     if (I1ElTy->isSized())
147       I1Size = LocationSize::precise(DL.getTypeStoreSize(I1ElTy));
148 
149     for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
150       auto I2Size = LocationSize::afterPointer();
151       Type *I2ElTy = cast<PointerType>((*I2)->getType())->getElementType();
152       if (I2ElTy->isSized())
153         I2Size = LocationSize::precise(DL.getTypeStoreSize(I2ElTy));
154 
155       AliasResult AR = AA.alias(*I1, I1Size, *I2, I2Size);
156       switch (AR) {
157       case AliasResult::NoAlias:
158         PrintResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
159         ++NoAliasCount;
160         break;
161       case AliasResult::MayAlias:
162         PrintResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
163         ++MayAliasCount;
164         break;
165       case AliasResult::PartialAlias:
166         PrintResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
167         ++PartialAliasCount;
168         break;
169       case AliasResult::MustAlias:
170         PrintResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
171         ++MustAliasCount;
172         break;
173       }
174     }
175   }
176 
177   if (EvalAAMD) {
178     // iterate over all pairs of load, store
179     for (Value *Load : Loads) {
180       for (Value *Store : Stores) {
181         AliasResult AR = AA.alias(MemoryLocation::get(cast<LoadInst>(Load)),
182                                   MemoryLocation::get(cast<StoreInst>(Store)));
183         switch (AR) {
184         case AliasResult::NoAlias:
185           PrintLoadStoreResults(AR, PrintNoAlias, Load, Store, F.getParent());
186           ++NoAliasCount;
187           break;
188         case AliasResult::MayAlias:
189           PrintLoadStoreResults(AR, PrintMayAlias, Load, Store, F.getParent());
190           ++MayAliasCount;
191           break;
192         case AliasResult::PartialAlias:
193           PrintLoadStoreResults(AR, PrintPartialAlias, Load, Store, F.getParent());
194           ++PartialAliasCount;
195           break;
196         case AliasResult::MustAlias:
197           PrintLoadStoreResults(AR, PrintMustAlias, Load, Store, F.getParent());
198           ++MustAliasCount;
199           break;
200         }
201       }
202     }
203 
204     // iterate over all pairs of store, store
205     for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
206          I1 != E; ++I1) {
207       for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
208         AliasResult AR = AA.alias(MemoryLocation::get(cast<StoreInst>(*I1)),
209                                   MemoryLocation::get(cast<StoreInst>(*I2)));
210         switch (AR) {
211         case AliasResult::NoAlias:
212           PrintLoadStoreResults(AR, PrintNoAlias, *I1, *I2, F.getParent());
213           ++NoAliasCount;
214           break;
215         case AliasResult::MayAlias:
216           PrintLoadStoreResults(AR, PrintMayAlias, *I1, *I2, F.getParent());
217           ++MayAliasCount;
218           break;
219         case AliasResult::PartialAlias:
220           PrintLoadStoreResults(AR, PrintPartialAlias, *I1, *I2, F.getParent());
221           ++PartialAliasCount;
222           break;
223         case AliasResult::MustAlias:
224           PrintLoadStoreResults(AR, PrintMustAlias, *I1, *I2, F.getParent());
225           ++MustAliasCount;
226           break;
227         }
228       }
229     }
230   }
231 
232   // Mod/ref alias analysis: compare all pairs of calls and values
233   for (CallBase *Call : Calls) {
234     for (auto Pointer : Pointers) {
235       auto Size = LocationSize::afterPointer();
236       Type *ElTy = cast<PointerType>(Pointer->getType())->getElementType();
237       if (ElTy->isSized())
238         Size = LocationSize::precise(DL.getTypeStoreSize(ElTy));
239 
240       switch (AA.getModRefInfo(Call, Pointer, Size)) {
241       case ModRefInfo::NoModRef:
242         PrintModRefResults("NoModRef", PrintNoModRef, Call, Pointer,
243                            F.getParent());
244         ++NoModRefCount;
245         break;
246       case ModRefInfo::Mod:
247         PrintModRefResults("Just Mod", PrintMod, Call, Pointer, F.getParent());
248         ++ModCount;
249         break;
250       case ModRefInfo::Ref:
251         PrintModRefResults("Just Ref", PrintRef, Call, Pointer, F.getParent());
252         ++RefCount;
253         break;
254       case ModRefInfo::ModRef:
255         PrintModRefResults("Both ModRef", PrintModRef, Call, Pointer,
256                            F.getParent());
257         ++ModRefCount;
258         break;
259       case ModRefInfo::Must:
260         PrintModRefResults("Must", PrintMust, Call, Pointer, F.getParent());
261         ++MustCount;
262         break;
263       case ModRefInfo::MustMod:
264         PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, Call, Pointer,
265                            F.getParent());
266         ++MustModCount;
267         break;
268       case ModRefInfo::MustRef:
269         PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, Call, Pointer,
270                            F.getParent());
271         ++MustRefCount;
272         break;
273       case ModRefInfo::MustModRef:
274         PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, Call,
275                            Pointer, F.getParent());
276         ++MustModRefCount;
277         break;
278       }
279     }
280   }
281 
282   // Mod/ref alias analysis: compare all pairs of calls
283   for (CallBase *CallA : Calls) {
284     for (CallBase *CallB : Calls) {
285       if (CallA == CallB)
286         continue;
287       switch (AA.getModRefInfo(CallA, CallB)) {
288       case ModRefInfo::NoModRef:
289         PrintModRefResults("NoModRef", PrintNoModRef, CallA, CallB,
290                            F.getParent());
291         ++NoModRefCount;
292         break;
293       case ModRefInfo::Mod:
294         PrintModRefResults("Just Mod", PrintMod, CallA, CallB, F.getParent());
295         ++ModCount;
296         break;
297       case ModRefInfo::Ref:
298         PrintModRefResults("Just Ref", PrintRef, CallA, CallB, F.getParent());
299         ++RefCount;
300         break;
301       case ModRefInfo::ModRef:
302         PrintModRefResults("Both ModRef", PrintModRef, CallA, CallB,
303                            F.getParent());
304         ++ModRefCount;
305         break;
306       case ModRefInfo::Must:
307         PrintModRefResults("Must", PrintMust, CallA, CallB, F.getParent());
308         ++MustCount;
309         break;
310       case ModRefInfo::MustMod:
311         PrintModRefResults("Just Mod (MustAlias)", PrintMustMod, CallA, CallB,
312                            F.getParent());
313         ++MustModCount;
314         break;
315       case ModRefInfo::MustRef:
316         PrintModRefResults("Just Ref (MustAlias)", PrintMustRef, CallA, CallB,
317                            F.getParent());
318         ++MustRefCount;
319         break;
320       case ModRefInfo::MustModRef:
321         PrintModRefResults("Both ModRef (MustAlias)", PrintMustModRef, CallA,
322                            CallB, F.getParent());
323         ++MustModRefCount;
324         break;
325       }
326     }
327   }
328 }
329 
PrintPercent(int64_t Num,int64_t Sum)330 static void PrintPercent(int64_t Num, int64_t Sum) {
331   errs() << "(" << Num * 100LL / Sum << "." << ((Num * 1000LL / Sum) % 10)
332          << "%)\n";
333 }
334 
~AAEvaluator()335 AAEvaluator::~AAEvaluator() {
336   if (FunctionCount == 0)
337     return;
338 
339   int64_t AliasSum =
340       NoAliasCount + MayAliasCount + PartialAliasCount + MustAliasCount;
341   errs() << "===== Alias Analysis Evaluator Report =====\n";
342   if (AliasSum == 0) {
343     errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
344   } else {
345     errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
346     errs() << "  " << NoAliasCount << " no alias responses ";
347     PrintPercent(NoAliasCount, AliasSum);
348     errs() << "  " << MayAliasCount << " may alias responses ";
349     PrintPercent(MayAliasCount, AliasSum);
350     errs() << "  " << PartialAliasCount << " partial alias responses ";
351     PrintPercent(PartialAliasCount, AliasSum);
352     errs() << "  " << MustAliasCount << " must alias responses ";
353     PrintPercent(MustAliasCount, AliasSum);
354     errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
355            << NoAliasCount * 100 / AliasSum << "%/"
356            << MayAliasCount * 100 / AliasSum << "%/"
357            << PartialAliasCount * 100 / AliasSum << "%/"
358            << MustAliasCount * 100 / AliasSum << "%\n";
359   }
360 
361   // Display the summary for mod/ref analysis
362   int64_t ModRefSum = NoModRefCount + RefCount + ModCount + ModRefCount +
363                       MustCount + MustRefCount + MustModCount + MustModRefCount;
364   if (ModRefSum == 0) {
365     errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no "
366               "mod/ref!\n";
367   } else {
368     errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
369     errs() << "  " << NoModRefCount << " no mod/ref responses ";
370     PrintPercent(NoModRefCount, ModRefSum);
371     errs() << "  " << ModCount << " mod responses ";
372     PrintPercent(ModCount, ModRefSum);
373     errs() << "  " << RefCount << " ref responses ";
374     PrintPercent(RefCount, ModRefSum);
375     errs() << "  " << ModRefCount << " mod & ref responses ";
376     PrintPercent(ModRefCount, ModRefSum);
377     errs() << "  " << MustCount << " must responses ";
378     PrintPercent(MustCount, ModRefSum);
379     errs() << "  " << MustModCount << " must mod responses ";
380     PrintPercent(MustModCount, ModRefSum);
381     errs() << "  " << MustRefCount << " must ref responses ";
382     PrintPercent(MustRefCount, ModRefSum);
383     errs() << "  " << MustModRefCount << " must mod & ref responses ";
384     PrintPercent(MustModRefCount, ModRefSum);
385     errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
386            << NoModRefCount * 100 / ModRefSum << "%/"
387            << ModCount * 100 / ModRefSum << "%/" << RefCount * 100 / ModRefSum
388            << "%/" << ModRefCount * 100 / ModRefSum << "%/"
389            << MustCount * 100 / ModRefSum << "%/"
390            << MustRefCount * 100 / ModRefSum << "%/"
391            << MustModCount * 100 / ModRefSum << "%/"
392            << MustModRefCount * 100 / ModRefSum << "%\n";
393   }
394 }
395 
396 namespace llvm {
397 class AAEvalLegacyPass : public FunctionPass {
398   std::unique_ptr<AAEvaluator> P;
399 
400 public:
401   static char ID; // Pass identification, replacement for typeid
AAEvalLegacyPass()402   AAEvalLegacyPass() : FunctionPass(ID) {
403     initializeAAEvalLegacyPassPass(*PassRegistry::getPassRegistry());
404   }
405 
getAnalysisUsage(AnalysisUsage & AU) const406   void getAnalysisUsage(AnalysisUsage &AU) const override {
407     AU.addRequired<AAResultsWrapperPass>();
408     AU.setPreservesAll();
409   }
410 
doInitialization(Module & M)411   bool doInitialization(Module &M) override {
412     P.reset(new AAEvaluator());
413     return false;
414   }
415 
runOnFunction(Function & F)416   bool runOnFunction(Function &F) override {
417     P->runInternal(F, getAnalysis<AAResultsWrapperPass>().getAAResults());
418     return false;
419   }
doFinalization(Module & M)420   bool doFinalization(Module &M) override {
421     P.reset();
422     return false;
423   }
424 };
425 }
426 
427 char AAEvalLegacyPass::ID = 0;
428 INITIALIZE_PASS_BEGIN(AAEvalLegacyPass, "aa-eval",
429                       "Exhaustive Alias Analysis Precision Evaluator", false,
430                       true)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)431 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
432 INITIALIZE_PASS_END(AAEvalLegacyPass, "aa-eval",
433                     "Exhaustive Alias Analysis Precision Evaluator", false,
434                     true)
435 
436 FunctionPass *llvm::createAAEvalPass() { return new AAEvalLegacyPass(); }
437