[LLVMdev] IVUsers (LoopPass) analysis in a ModulePass?

[Timothy Mattausch Creech]

Hi Devang,
  Thanks for your reply. In my case it is helpful just to know that what I'm trying is unsupported.

You're right that we don't really strictly need this arrangement. Ideally, I think our ModulePass should actually be converted to a LoopPass. I think this is how we'll move forward.

Thanks again,
Tim

On Sep 12, 2011, at 5:41 PM, Devang Patel wrote:

Hi Tim,


From: Tim Creech <tcreech at umd.edu<mailto:tcreech at umd.edu>>
Subject: [LLVMdev] IVUsers (LoopPass) analysis in a ModulePass?
Date: September 1, 2011 11:46:28 AM PDT
To: llvmdev at cs.uiuc.edu<mailto:llvmdev at cs.uiuc.edu>

Hi all,
 I have a loadable ModulePass which does transformations, and I would like to
use IVUsers analysis within it. I noticed when I try to do this (via
the usual addRequired<IVUsers>() and getAnalysis<IVUsers>(*F)), opt
fails an assert:

All LoopPass, including IVUsers, uses runOnLoop(L, LPM) as an external  interface to collect loop analysis or transform a loop. This is the hook used by pass manager. In your case getAnalysis<IVUsers>(*F) (where I assume F is a function ptr) is not what IVUsers supports. This works for FunctionPass because pass manager can do runOnFunction(F).

opt: /home/tcreech/build/llvm-2.9/include/llvm/PassAnalysisSupport.h:239: AnalysisType& llvm::Pass::getAnalysisID(const void*, llvm::Function&) [with AnalysisType = llvm::LoopInfo]: Assertion `ResultPass && "Unable to find requested analysis info"' failed.

...where I was using LoopInfo analysis without trouble before trying to
run IVUsers analysis as well. I suspect that I'm somehow doing something
that LLVM just doesn't allow. I know that LLVM allows getting
FunctionPass analysis from a ModulePass, but can I also get LoopPass
analysis from a ModulePass?

As you can image, this is not something that is supported by current pass manager implement.

Are you sure you need LoopPass to run your ModulePass ? Typically, ModulePass work at a module level e.g. inline functions, change function signatures etc.. Why would a ModulePass need a  LoopPass analysis ? I am curious.

If you're interested in updating pass manager to support your needs then I can give you some hints.
-
Devang

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