AliasAnalysisEvaluator.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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/IR/Constants.h"
24#include "llvm/IR/DerivedTypes.h"
25#include "llvm/IR/Function.h"
26#include "llvm/IR/InstIterator.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/raw_ostream.h"
32using namespace llvm;
33
34static cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
35
36static cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
37static cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
38static cl::opt<bool> PrintPartialAlias("print-partial-aliases", cl::ReallyHidden);
39static cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
40
41static cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
42static cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
43static cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
44static cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
45
46static cl::opt<bool> EvalTBAA("evaluate-tbaa", cl::ReallyHidden);
47
48namespace {
49  class AAEval : public FunctionPass {
50    unsigned NoAlias, MayAlias, PartialAlias, MustAlias;
51    unsigned NoModRef, Mod, Ref, ModRef;
52
53  public:
54    static char ID; // Pass identification, replacement for typeid
55    AAEval() : FunctionPass(ID) {
56      initializeAAEvalPass(*PassRegistry::getPassRegistry());
57    }
58
59    void getAnalysisUsage(AnalysisUsage &AU) const override {
60      AU.addRequired<AliasAnalysis>();
61      AU.setPreservesAll();
62    }
63
64    bool doInitialization(Module &M) override {
65      NoAlias = MayAlias = PartialAlias = MustAlias = 0;
66      NoModRef = Mod = Ref = ModRef = 0;
67
68      if (PrintAll) {
69        PrintNoAlias = PrintMayAlias = true;
70        PrintPartialAlias = PrintMustAlias = true;
71        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
72      }
73      return false;
74    }
75
76    bool runOnFunction(Function &F) override;
77    bool doFinalization(Module &M) override;
78  };
79}
80
81char AAEval::ID = 0;
82INITIALIZE_PASS_BEGIN(AAEval, "aa-eval",
83                "Exhaustive Alias Analysis Precision Evaluator", false, true)
84INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
85INITIALIZE_PASS_END(AAEval, "aa-eval",
86                "Exhaustive Alias Analysis Precision Evaluator", false, true)
87
88FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
89
90static void PrintResults(const char *Msg, bool P, const Value *V1,
91                         const Value *V2, const Module *M) {
92  if (P) {
93    std::string o1, o2;
94    {
95      raw_string_ostream os1(o1), os2(o2);
96      V1->printAsOperand(os1, true, M);
97      V2->printAsOperand(os2, true, M);
98    }
99
100    if (o2 < o1)
101      std::swap(o1, o2);
102    errs() << "  " << Msg << ":\t"
103           << o1 << ", "
104           << o2 << "\n";
105  }
106}
107
108static inline void
109PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
110                   Module *M) {
111  if (P) {
112    errs() << "  " << Msg << ":  Ptr: ";
113    Ptr->printAsOperand(errs(), true, M);
114    errs() << "\t<->" << *I << '\n';
115  }
116}
117
118static inline void
119PrintModRefResults(const char *Msg, bool P, CallSite CSA, CallSite CSB,
120                   Module *M) {
121  if (P) {
122    errs() << "  " << Msg << ": " << *CSA.getInstruction()
123           << " <-> " << *CSB.getInstruction() << '\n';
124  }
125}
126
127static inline void
128PrintLoadStoreResults(const char *Msg, bool P, const Value *V1,
129                      const Value *V2, const Module *M) {
130  if (P) {
131    errs() << "  " << Msg << ": " << *V1
132           << " <-> " << *V2 << '\n';
133  }
134}
135
136static inline bool isInterestingPointer(Value *V) {
137  return V->getType()->isPointerTy()
138      && !isa<ConstantPointerNull>(V);
139}
140
141bool AAEval::runOnFunction(Function &F) {
142  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
143
144  SetVector<Value *> Pointers;
145  SetVector<CallSite> CallSites;
146  SetVector<Value *> Loads;
147  SetVector<Value *> Stores;
148
149  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
150    if (I->getType()->isPointerTy())    // Add all pointer arguments.
151      Pointers.insert(I);
152
153  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
154    if (I->getType()->isPointerTy()) // Add all pointer instructions.
155      Pointers.insert(&*I);
156    if (EvalTBAA && isa<LoadInst>(&*I))
157      Loads.insert(&*I);
158    if (EvalTBAA && isa<StoreInst>(&*I))
159      Stores.insert(&*I);
160    Instruction &Inst = *I;
161    if (CallSite CS = cast<Value>(&Inst)) {
162      Value *Callee = CS.getCalledValue();
163      // Skip actual functions for direct function calls.
164      if (!isa<Function>(Callee) && isInterestingPointer(Callee))
165        Pointers.insert(Callee);
166      // Consider formals.
167      for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
168           AI != AE; ++AI)
169        if (isInterestingPointer(*AI))
170          Pointers.insert(*AI);
171      CallSites.insert(CS);
172    } else {
173      // Consider all operands.
174      for (Instruction::op_iterator OI = Inst.op_begin(), OE = Inst.op_end();
175           OI != OE; ++OI)
176        if (isInterestingPointer(*OI))
177          Pointers.insert(*OI);
178    }
179  }
180
181  if (PrintNoAlias || PrintMayAlias || PrintPartialAlias || PrintMustAlias ||
182      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
183    errs() << "Function: " << F.getName() << ": " << Pointers.size()
184           << " pointers, " << CallSites.size() << " call sites\n";
185
186  // iterate over the worklist, and run the full (n^2)/2 disambiguations
187  for (SetVector<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
188       I1 != E; ++I1) {
189    uint64_t I1Size = AliasAnalysis::UnknownSize;
190    Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
191    if (I1ElTy->isSized()) I1Size = AA.getTypeStoreSize(I1ElTy);
192
193    for (SetVector<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
194      uint64_t I2Size = AliasAnalysis::UnknownSize;
195      Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
196      if (I2ElTy->isSized()) I2Size = AA.getTypeStoreSize(I2ElTy);
197
198      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
199      case AliasAnalysis::NoAlias:
200        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
201        ++NoAlias; break;
202      case AliasAnalysis::MayAlias:
203        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
204        ++MayAlias; break;
205      case AliasAnalysis::PartialAlias:
206        PrintResults("PartialAlias", PrintPartialAlias, *I1, *I2,
207                     F.getParent());
208        ++PartialAlias; break;
209      case AliasAnalysis::MustAlias:
210        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
211        ++MustAlias; break;
212      }
213    }
214  }
215
216  if (EvalTBAA) {
217    // iterate over all pairs of load, store
218    for (SetVector<Value *>::iterator I1 = Loads.begin(), E = Loads.end();
219         I1 != E; ++I1) {
220      for (SetVector<Value *>::iterator I2 = Stores.begin(), E2 = Stores.end();
221           I2 != E2; ++I2) {
222        switch (AA.alias(AA.getLocation(cast<LoadInst>(*I1)),
223                         AA.getLocation(cast<StoreInst>(*I2)))) {
224        case AliasAnalysis::NoAlias:
225          PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
226                                F.getParent());
227          ++NoAlias; break;
228        case AliasAnalysis::MayAlias:
229          PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
230                                F.getParent());
231          ++MayAlias; break;
232        case AliasAnalysis::PartialAlias:
233          PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
234                                F.getParent());
235          ++PartialAlias; break;
236        case AliasAnalysis::MustAlias:
237          PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
238                                F.getParent());
239          ++MustAlias; break;
240        }
241      }
242    }
243
244    // iterate over all pairs of store, store
245    for (SetVector<Value *>::iterator I1 = Stores.begin(), E = Stores.end();
246         I1 != E; ++I1) {
247      for (SetVector<Value *>::iterator I2 = Stores.begin(); I2 != I1; ++I2) {
248        switch (AA.alias(AA.getLocation(cast<StoreInst>(*I1)),
249                         AA.getLocation(cast<StoreInst>(*I2)))) {
250        case AliasAnalysis::NoAlias:
251          PrintLoadStoreResults("NoAlias", PrintNoAlias, *I1, *I2,
252                                F.getParent());
253          ++NoAlias; break;
254        case AliasAnalysis::MayAlias:
255          PrintLoadStoreResults("MayAlias", PrintMayAlias, *I1, *I2,
256                                F.getParent());
257          ++MayAlias; break;
258        case AliasAnalysis::PartialAlias:
259          PrintLoadStoreResults("PartialAlias", PrintPartialAlias, *I1, *I2,
260                                F.getParent());
261          ++PartialAlias; break;
262        case AliasAnalysis::MustAlias:
263          PrintLoadStoreResults("MustAlias", PrintMustAlias, *I1, *I2,
264                                F.getParent());
265          ++MustAlias; break;
266        }
267      }
268    }
269  }
270
271  // Mod/ref alias analysis: compare all pairs of calls and values
272  for (SetVector<CallSite>::iterator C = CallSites.begin(),
273         Ce = CallSites.end(); C != Ce; ++C) {
274    Instruction *I = C->getInstruction();
275
276    for (SetVector<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
277         V != Ve; ++V) {
278      uint64_t Size = AliasAnalysis::UnknownSize;
279      Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
280      if (ElTy->isSized()) Size = AA.getTypeStoreSize(ElTy);
281
282      switch (AA.getModRefInfo(*C, *V, Size)) {
283      case AliasAnalysis::NoModRef:
284        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
285        ++NoModRef; break;
286      case AliasAnalysis::Mod:
287        PrintModRefResults("Just Mod", PrintMod, I, *V, F.getParent());
288        ++Mod; break;
289      case AliasAnalysis::Ref:
290        PrintModRefResults("Just Ref", PrintRef, I, *V, F.getParent());
291        ++Ref; break;
292      case AliasAnalysis::ModRef:
293        PrintModRefResults("Both ModRef", PrintModRef, I, *V, F.getParent());
294        ++ModRef; break;
295      }
296    }
297  }
298
299  // Mod/ref alias analysis: compare all pairs of calls
300  for (SetVector<CallSite>::iterator C = CallSites.begin(),
301         Ce = CallSites.end(); C != Ce; ++C) {
302    for (SetVector<CallSite>::iterator D = CallSites.begin(); D != Ce; ++D) {
303      if (D == C)
304        continue;
305      switch (AA.getModRefInfo(*C, *D)) {
306      case AliasAnalysis::NoModRef:
307        PrintModRefResults("NoModRef", PrintNoModRef, *C, *D, F.getParent());
308        ++NoModRef; break;
309      case AliasAnalysis::Mod:
310        PrintModRefResults("Just Mod", PrintMod, *C, *D, F.getParent());
311        ++Mod; break;
312      case AliasAnalysis::Ref:
313        PrintModRefResults("Just Ref", PrintRef, *C, *D, F.getParent());
314        ++Ref; break;
315      case AliasAnalysis::ModRef:
316        PrintModRefResults("Both ModRef", PrintModRef, *C, *D, F.getParent());
317        ++ModRef; break;
318      }
319    }
320  }
321
322  return false;
323}
324
325static void PrintPercent(unsigned Num, unsigned Sum) {
326  errs() << "(" << Num*100ULL/Sum << "."
327         << ((Num*1000ULL/Sum) % 10) << "%)\n";
328}
329
330bool AAEval::doFinalization(Module &M) {
331  unsigned AliasSum = NoAlias + MayAlias + PartialAlias + MustAlias;
332  errs() << "===== Alias Analysis Evaluator Report =====\n";
333  if (AliasSum == 0) {
334    errs() << "  Alias Analysis Evaluator Summary: No pointers!\n";
335  } else {
336    errs() << "  " << AliasSum << " Total Alias Queries Performed\n";
337    errs() << "  " << NoAlias << " no alias responses ";
338    PrintPercent(NoAlias, AliasSum);
339    errs() << "  " << MayAlias << " may alias responses ";
340    PrintPercent(MayAlias, AliasSum);
341    errs() << "  " << PartialAlias << " partial alias responses ";
342    PrintPercent(PartialAlias, AliasSum);
343    errs() << "  " << MustAlias << " must alias responses ";
344    PrintPercent(MustAlias, AliasSum);
345    errs() << "  Alias Analysis Evaluator Pointer Alias Summary: "
346           << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
347           << PartialAlias*100/AliasSum << "%/"
348           << MustAlias*100/AliasSum << "%\n";
349  }
350
351  // Display the summary for mod/ref analysis
352  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
353  if (ModRefSum == 0) {
354    errs() << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
355  } else {
356    errs() << "  " << ModRefSum << " Total ModRef Queries Performed\n";
357    errs() << "  " << NoModRef << " no mod/ref responses ";
358    PrintPercent(NoModRef, ModRefSum);
359    errs() << "  " << Mod << " mod responses ";
360    PrintPercent(Mod, ModRefSum);
361    errs() << "  " << Ref << " ref responses ";
362    PrintPercent(Ref, ModRefSum);
363    errs() << "  " << ModRef << " mod & ref responses ";
364    PrintPercent(ModRef, ModRefSum);
365    errs() << "  Alias Analysis Evaluator Mod/Ref Summary: "
366           << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
367           << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
368  }
369
370  return false;
371}
372