AliasAnalysisEvaluator.cpp revision 534927d82de6d1be0f6e939263eeb309ad135661 
1//===- AliasAnalysisEvaluator.cpp - Alias Analysis Accuracy Evaluator -----===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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/Function.h"
21#include "llvm/Instructions.h"
22#include "llvm/Pass.h"
23#include "llvm/DerivedTypes.h"
24#include "llvm/Analysis/Passes.h"
25#include "llvm/Analysis/AliasAnalysis.h"
26#include "llvm/Assembly/Writer.h"
27#include "llvm/Target/TargetData.h"
28#include "llvm/Support/InstIterator.h"
29#include "llvm/Support/CommandLine.h"
30#include <iostream>
31#include <set>
32
33using namespace llvm;
34
35namespace {
36  cl::opt<bool> PrintAll("print-all-alias-modref-info", cl::ReallyHidden);
37
38  cl::opt<bool> PrintNoAlias("print-no-aliases", cl::ReallyHidden);
39  cl::opt<bool> PrintMayAlias("print-may-aliases", cl::ReallyHidden);
40  cl::opt<bool> PrintMustAlias("print-must-aliases", cl::ReallyHidden);
41
42  cl::opt<bool> PrintNoModRef("print-no-modref", cl::ReallyHidden);
43  cl::opt<bool> PrintMod("print-mod", cl::ReallyHidden);
44  cl::opt<bool> PrintRef("print-ref", cl::ReallyHidden);
45  cl::opt<bool> PrintModRef("print-modref", cl::ReallyHidden);
46
47  class AAEval : public FunctionPass {
48    unsigned NoAlias, MayAlias, MustAlias;
49    unsigned NoModRef, Mod, Ref, ModRef;
50
51  public:
52    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
53      AU.addRequired<AliasAnalysis>();
54      AU.setPreservesAll();
55    }
56
57    bool doInitialization(Module &M) {
58      NoAlias = MayAlias = MustAlias = 0;
59      NoModRef = Mod = Ref = ModRef = 0;
60
61      if (PrintAll) {
62        PrintNoAlias = PrintMayAlias = PrintMustAlias = true;
63        PrintNoModRef = PrintMod = PrintRef = PrintModRef = true;
64      }
65      return false;
66    }
67
68    bool runOnFunction(Function &F);
69    bool doFinalization(Module &M);
70  };
71
72  RegisterOpt<AAEval>
73  X("aa-eval", "Exhaustive Alias Analysis Precision Evaluator");
74}
75
76FunctionPass *llvm::createAAEvalPass() { return new AAEval(); }
77
78static inline void PrintResults(const char *Msg, bool P, Value *V1, Value *V2,
79                                Module *M) {
80  if (P) {
81    std::cerr << "  " << Msg << ":\t";
82    WriteAsOperand(std::cerr, V1, true, true, M) << ", ";
83    WriteAsOperand(std::cerr, V2, true, true, M) << "\n";
84  }
85}
86
87static inline void
88PrintModRefResults(const char *Msg, bool P, Instruction *I, Value *Ptr,
89                   Module *M) {
90  if (P) {
91    std::cerr << "  " << Msg << ":  Ptr: ";
92    WriteAsOperand(std::cerr, Ptr, true, true, M);
93    std::cerr << "\t<->" << *I;
94  }
95}
96
97bool AAEval::runOnFunction(Function &F) {
98  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
99
100  const TargetData &TD = AA.getTargetData();
101
102  std::set<Value *> Pointers;
103  std::set<CallSite> CallSites;
104
105  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
106    if (isa<PointerType>(I->getType()))    // Add all pointer arguments
107      Pointers.insert(I);
108
109  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
110    if (isa<PointerType>(I->getType())) // Add all pointer instructions
111      Pointers.insert(&*I);
112    for (User::op_iterator OI = (*I).op_begin(); OI != (*I).op_end(); ++OI)
113      if (isa<PointerType>((*OI)->getType()))
114        Pointers.insert(*OI);
115
116    CallSite CS = CallSite::get(&*I);
117    if (CS.getInstruction()) CallSites.insert(CS);
118  }
119
120  if (PrintNoAlias || PrintMayAlias || PrintMustAlias ||
121      PrintNoModRef || PrintMod || PrintRef || PrintModRef)
122    std::cerr << "Function: " << F.getName() << ": " << Pointers.size()
123              << " pointers, " << CallSites.size() << " call sites\n";
124
125  // iterate over the worklist, and run the full (n^2)/2 disambiguations
126  for (std::set<Value *>::iterator I1 = Pointers.begin(), E = Pointers.end();
127       I1 != E; ++I1) {
128    unsigned I1Size = 0;
129    const Type *I1ElTy = cast<PointerType>((*I1)->getType())->getElementType();
130    if (I1ElTy->isSized()) I1Size = TD.getTypeSize(I1ElTy);
131
132    for (std::set<Value *>::iterator I2 = Pointers.begin(); I2 != I1; ++I2) {
133      unsigned I2Size = 0;
134      const Type *I2ElTy =cast<PointerType>((*I2)->getType())->getElementType();
135      if (I2ElTy->isSized()) I2Size = TD.getTypeSize(I2ElTy);
136
137      switch (AA.alias(*I1, I1Size, *I2, I2Size)) {
138      case AliasAnalysis::NoAlias:
139        PrintResults("NoAlias", PrintNoAlias, *I1, *I2, F.getParent());
140        ++NoAlias; break;
141      case AliasAnalysis::MayAlias:
142        PrintResults("MayAlias", PrintMayAlias, *I1, *I2, F.getParent());
143        ++MayAlias; break;
144      case AliasAnalysis::MustAlias:
145        PrintResults("MustAlias", PrintMustAlias, *I1, *I2, F.getParent());
146        ++MustAlias; break;
147      default:
148        std::cerr << "Unknown alias query result!\n";
149      }
150    }
151  }
152
153  // Mod/ref alias analysis: compare all pairs of calls and values
154  for (std::set<Value *>::iterator V = Pointers.begin(), Ve = Pointers.end();
155       V != Ve; ++V) {
156    unsigned Size = 0;
157    const Type *ElTy = cast<PointerType>((*V)->getType())->getElementType();
158    if (ElTy->isSized()) Size = TD.getTypeSize(ElTy);
159
160    for (std::set<CallSite>::iterator C = CallSites.begin(),
161           Ce = CallSites.end(); C != Ce; ++C) {
162      Instruction *I = C->getInstruction();
163      switch (AA.getModRefInfo(*C, *V, Size)) {
164      case AliasAnalysis::NoModRef:
165        PrintModRefResults("NoModRef", PrintNoModRef, I, *V, F.getParent());
166        ++NoModRef; break;
167      case AliasAnalysis::Mod:
168        PrintModRefResults("     Mod", PrintMod, I, *V, F.getParent());
169        ++Mod; break;
170      case AliasAnalysis::Ref:
171        PrintModRefResults("     Ref", PrintRef, I, *V, F.getParent());
172        ++Ref; break;
173      case AliasAnalysis::ModRef:
174        PrintModRefResults("  ModRef", PrintModRef, I, *V, F.getParent());
175        ++ModRef; break;
176      default:
177        std::cerr << "Unknown alias query result!\n";
178      }
179    }
180  }
181
182  return false;
183}
184
185bool AAEval::doFinalization(Module &M) {
186  unsigned AliasSum = NoAlias + MayAlias + MustAlias;
187  std::cerr << "===== Alias Analysis Evaluator Report =====\n";
188  if (AliasSum == 0) {
189    std::cerr << "  Alias Analysis Evaluator Summary: No pointers!\n";
190  } else {
191    std::cerr << "  " << AliasSum << " Total Alias Queries Performed\n";
192    std::cerr << "  " << NoAlias << " no alias responses ("
193              << NoAlias*100/AliasSum << "%)\n";
194    std::cerr << "  " << MayAlias << " may alias responses ("
195              << MayAlias*100/AliasSum << "%)\n";
196    std::cerr << "  " << MustAlias << " must alias responses ("
197              << MustAlias*100/AliasSum <<"%)\n";
198    std::cerr << "  Alias Analysis Evaluator Pointer Alias Summary: "
199              << NoAlias*100/AliasSum  << "%/" << MayAlias*100/AliasSum << "%/"
200              << MustAlias*100/AliasSum << "%\n";
201  }
202
203  // Display the summary for mod/ref analysis
204  unsigned ModRefSum = NoModRef + Mod + Ref + ModRef;
205  if (ModRefSum == 0) {
206    std::cerr << "  Alias Analysis Mod/Ref Evaluator Summary: no mod/ref!\n";
207  } else {
208    std::cerr << "  " << ModRefSum << " Total ModRef Queries Performed\n";
209    std::cerr << "  " << NoModRef << " no mod/ref responses ("
210              << NoModRef*100/ModRefSum << "%)\n";
211    std::cerr << "  " << Mod << " mod responses ("
212              << Mod*100/ModRefSum << "%)\n";
213    std::cerr << "  " << Ref << " ref responses ("
214              << Ref*100/ModRefSum <<"%)\n";
215    std::cerr << "  " << ModRef << " mod & ref responses ("
216              << ModRef*100/ModRefSum <<"%)\n";
217    std::cerr << "  Alias Analysis Evaluator Mod/Ref Summary: "
218              << NoModRef*100/ModRefSum  << "%/" << Mod*100/ModRefSum << "%/"
219              << Ref*100/ModRefSum << "%/" << ModRef*100/ModRefSum << "%\n";
220  }
221
222  return false;
223}
224