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      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>
     27 using namespace llvm;
     28 
     29 namespace {
     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, &M.getDataLayout()); // 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 
    133 char AliasDebugger::ID = 0;
    134 INITIALIZE_AG_PASS(AliasDebugger, AliasAnalysis, "debug-aa",
    135                    "AA use debugger", false, true, false)
    136 
    137 Pass *llvm::createAliasDebugger() { return new AliasDebugger(); }
    138 
    139