[llvm-dev] How to get the full alias analysis results of LLVM Alias analysis passes?

[Ren Kunpeng via llvm-dev]

Hi all,

 I am working on a project about pointer analysis based on LLVM IR, and I not very familar with LLVM Development.
Now, I want to compare the original LLVM alias analysis pass with my tool. I use AAResultsWrapperPass to do this thing, just as below:

virtual bool runOnFunction(Function &F)
    {
      AliasAnalysis *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
      for (auto &B : F)
      {
        for (auto &I : B)
        {
          if (auto *call = dyn_cast<CallInst>(&I))
          {
            if (call->getCalledFunction()!= NULL)
            {
              if(call->getNumArgOperands() !=2)
                continue;
              Value *V1 = call->getArgOperand(0);
              Value *V2 = call->getArgOperand(1);
              //Get LLVM alias analysi result
              AliasResult aares = AA->alias(V1, V2);
              .......................


I have doubt that wether the AliasResults are analysied by all LLVM alias pass<https://llvm.org/docs/AliasAnalysis.html#available-aliasanalysis-implementations>, such as -basic-aa, -globalsmodref-aa, -stens-aa. I find the implement of AAResultsWrapperPass contains some code like below:
void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.setPreservesAll();
  AU.addRequiredTransitive<BasicAAWrapperPass>();
  AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();

  // We also need to mark all the alias analysis passes we will potentially
  // probe in runOnFunction as used here to ensure the legacy pass manager
  // preserves them. This hard coding of lists of alias analyses is specific to
  // the legacy pass manager.
  AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>();
  AU.addUsedIfAvailable<TypeBasedAAWrapperPass>();
  AU.addUsedIfAvailable<objcarc::ObjCARCAAWrapperPass>();
  AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
  AU.addUsedIfAvailable<SCEVAAWrapperPass>();
  AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
  AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
  AU.addUsedIfAvailable<ExternalAAWrapperPass>();
}
Does it mean the AAResultsWrapperPass contains all the alias analysis pass result?
By the way, is there a better implement to get the LLVM alias analysis result. Thank you for telling me about that.

Thanks for you reading. Wishing you have a good day.

Regards,
Kunpeng

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