AliasDebugger.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===- AliasDebugger.cpp - Simple Alias Analysis Use Checker --------------===//
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 simple pass checks alias analysis users to ensure that if they
11// create a new value, they do not query AA without informing it of the value.
12// It acts as a shim over any other AA pass you want.
13//
14// Yes keeping track of every value in the program is expensive, but this is
15// a debugging pass.
16//
17//===----------------------------------------------------------------------===//
18
19#include "llvm/Analysis/Passes.h"
20#include "llvm/Analysis/AliasAnalysis.h"
21#include "llvm/IR/Constants.h"
22#include "llvm/IR/DerivedTypes.h"
23#include "llvm/IR/Instructions.h"
24#include "llvm/IR/Module.h"
25#include "llvm/Pass.h"
26#include <set>
27using namespace llvm;
28
29namespace {
30
31  class AliasDebugger : public ModulePass, public AliasAnalysis {
32
33    //What we do is simple.  Keep track of every value the AA could
34    //know about, and verify that queries are one of those.
35    //A query to a value that didn't exist when the AA was created
36    //means someone forgot to update the AA when creating new values
37
38    std::set<const Value*> Vals;
39
40  public:
41    static char ID; // Class identification, replacement for typeinfo
42    AliasDebugger() : ModulePass(ID) {
43      initializeAliasDebuggerPass(*PassRegistry::getPassRegistry());
44    }
45
46    bool runOnModule(Module &M) override {
47      InitializeAliasAnalysis(this);                 // set up super class
48
49      for(Module::global_iterator I = M.global_begin(),
50            E = M.global_end(); I != E; ++I) {
51        Vals.insert(&*I);
52        for (User::const_op_iterator OI = I->op_begin(),
53             OE = I->op_end(); OI != OE; ++OI)
54          Vals.insert(*OI);
55      }
56
57      for(Module::iterator I = M.begin(),
58            E = M.end(); I != E; ++I){
59        Vals.insert(&*I);
60        if(!I->isDeclaration()) {
61          for (Function::arg_iterator AI = I->arg_begin(), AE = I->arg_end();
62               AI != AE; ++AI)
63            Vals.insert(&*AI);
64          for (Function::const_iterator FI = I->begin(), FE = I->end();
65               FI != FE; ++FI)
66            for (BasicBlock::const_iterator BI = FI->begin(), BE = FI->end();
67                 BI != BE; ++BI) {
68              Vals.insert(&*BI);
69              for (User::const_op_iterator OI = BI->op_begin(),
70                   OE = BI->op_end(); OI != OE; ++OI)
71                Vals.insert(*OI);
72            }
73        }
74
75      }
76      return false;
77    }
78
79    void getAnalysisUsage(AnalysisUsage &AU) const override {
80      AliasAnalysis::getAnalysisUsage(AU);
81      AU.setPreservesAll();                         // Does not transform code
82    }
83
84    /// getAdjustedAnalysisPointer - This method is used when a pass implements
85    /// an analysis interface through multiple inheritance.  If needed, it
86    /// should override this to adjust the this pointer as needed for the
87    /// specified pass info.
88    void *getAdjustedAnalysisPointer(AnalysisID PI) override {
89      if (PI == &AliasAnalysis::ID)
90        return (AliasAnalysis*)this;
91      return this;
92    }
93
94    //------------------------------------------------
95    // Implement the AliasAnalysis API
96    //
97    AliasResult alias(const Location &LocA, const Location &LocB) override {
98      assert(Vals.find(LocA.Ptr) != Vals.end() &&
99             "Never seen value in AA before");
100      assert(Vals.find(LocB.Ptr) != Vals.end() &&
101             "Never seen value in AA before");
102      return AliasAnalysis::alias(LocA, LocB);
103    }
104
105    ModRefResult getModRefInfo(ImmutableCallSite CS,
106                               const Location &Loc) override {
107      assert(Vals.find(Loc.Ptr) != Vals.end() && "Never seen value in AA before");
108      return AliasAnalysis::getModRefInfo(CS, Loc);
109    }
110
111    ModRefResult getModRefInfo(ImmutableCallSite CS1,
112                               ImmutableCallSite CS2) override {
113      return AliasAnalysis::getModRefInfo(CS1,CS2);
114    }
115
116    bool pointsToConstantMemory(const Location &Loc, bool OrLocal) override {
117      assert(Vals.find(Loc.Ptr) != Vals.end() && "Never seen value in AA before");
118      return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
119    }
120
121    void deleteValue(Value *V) override {
122      assert(Vals.find(V) != Vals.end() && "Never seen value in AA before");
123      AliasAnalysis::deleteValue(V);
124    }
125    void copyValue(Value *From, Value *To) override {
126      Vals.insert(To);
127      AliasAnalysis::copyValue(From, To);
128    }
129
130  };
131}
132
133char AliasDebugger::ID = 0;
134INITIALIZE_AG_PASS(AliasDebugger, AliasAnalysis, "debug-aa",
135                   "AA use debugger", false, true, false)
136
137Pass *llvm::createAliasDebugger() { return new AliasDebugger(); }
138
139