CODEWITHSUNDEEP
llvm
user2237704
user2237704

Reputation: 31

Using results from my own pass(not predefined pass) into next pass

I have created a pass that pathprofiles and then stores results in different data structures such as blocks corresponding to the paths, edges in paths etc. I have different variables and data structures for each of these.

Is there a way to use these variables directly in another pass that i write? If yes, how? (Im not sure if getAnalysisUsage works for this?) Urgent help required

Upvotes: 0

Views: 109

Answers (2)

Jens
Jens

Reputation: 9120

This answer might be late, but I had the same question, ran across your post and thanks to Oak was pointed into the right direction. So I wanted to share some code here.

Suppose you have two passes, the first one is your PathProfilePass and the second one is your DoSomethingPass. The first pass contains the data that you collect and share with the second path; nothing special needs to be done here:

/// Path profiling to gather heaps of data.
class PathProfilePass: public llvm::ModulePass {

  public:

    virtual bool runOnModule(llvm::Module &M) {

        // Create goodness for edges and paths.
        ...
    }

    std::set<Edges> edges;   ///< All the edges this pass collects.
    std::set<Paths> paths;   ///< All the paths this pass collects.
};

The interesting stuff happens in the second pass. Two things you need to do here:

  1. Specify the dependency of the second pass on the first pass: see the getAnalysisUsage method.
  2. Access the data from the first pass: see the getAnalysis method.

Code-wise it would look something like this for the second pass:

/// Doing something with edge and path informations.
class DoSomethingPass: public llvm::ModulePass {

  public:

    /// Specify the dependency of this pass on PathProfilePass.
    virtual void getAnalysisUsage(llvm::AnalysisUsage &AU) const {
        AU.addRequired<PathProfilePass>();
    }

    /// Use the data of the PathProfilePass.
    virtual bool runOnModule(llvm::Module &M) {

        PathProfilePass &PPP = getAnalysis<PathProfilePass>();

        // Get the edges and paths from the first pass.
        std::set<Edges> &edges = PPP.edges;
        std::set<Paths> &paths = PPP.paths;

        // Now you can noodle over that data.
        ...
    }
};

Disclaimer: I haven't compiled this code, but this is an adaptation to your example of what works for me. Hope this is useful :-)

Upvotes: 1

Oak
Oak

Reputation: 26868

Set a dependency from the 2nd pass to the 1st pass (via overriding getAnalysisUsage and invoking getAnalysis - see the programmer's guide to writing a pass on how to do that). Once you get an instance of the 1st pass, you can use it just like any other C++ object.

Upvotes: 0

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