[LLVMdev] getAnalysis<LoopInfo> from ModulePass

[Mariusz Grad]

Hi,

I wrote tiny ModulePass which iterates over functions and then uses getAnalysis<LoopInfo> in order to get informations about the loop.
It compiles smoothly, but whenever I try to run it I got error like this:
opt: .. PassAnalysisSupport.h:203: AnalysisType& llvm::Pass::getAnalysisID(const llvm::PassInfo*) const [with AnalysisType = llvm::LoopInfo]: Assertion `ResultPass && "getAnalysis*() called on an analysis that was not " "'required' by pass!"' failed.
What actually this assertion means?

Whenever I change the ModulePass to the FunctionPass the code bellow works just fine.

Here is the code:
# ============================== #

#define DEBUG_TYPE "bb_info" 
#include "llvm/Pass.h" 
#include "llvm/Function.h" 
#include <llvm/Module.h>
#include "llvm/Support/raw_ostream.h" 
#include "llvm/ADT/Statistic.h" 
#include "llvm/Analysis/LoopInfo.h" 

using namespace llvm; 

namespace { 
  struct bb_info: public ModulePass { 
    static char ID; 

    bb_info() : ModulePass(&ID) {} 

      void getLoopInfo(const Function& F) const { 
        const LoopInfo *LI =  &getAnalysis<LoopInfo> (); 
        Function::const_iterator BB = F.begin(), E = F.end(); 
        for (; BB != E; ++BB) 
          errs() << BB->getName() << " " << LI->getLoopDepth(&*BB) << "\n";
    }; 

    virtual bool runOnModule(Module &M) { 
      Module::const_iterator f_it = M.begin(), f_ite = M.end(); 
      for ( ; f_it != f_ite; ++f_it )
      {
        errs() << f_it->getName() << '\n'; 
        if (!f_it->isDeclaration())
          getLoopInfo(*f_it); 
      }
      return true;
    } 

    virtual void getAnalysisUsage(AnalysisUsage &AU) const { 
      AU.setPreservesAll(); 
      AU.addRequired<LoopInfo> (); 
    } 
  }; 
} 

char bb_info::ID = 0; 
static RegisterPass<bb_info> Y("bb_info", "testing ..");

-- 
Mariusz Grad