I want to get the results of ScalarEvolution analysis in a Function pass in order to get the tripcount for each loop.

I tried running this code:

llvm::ScalarEvolutionWrapperPass sewp = llvm::ScalarEvolutionWrapperPass();
llvm::ScalarEvolution &se = sewp.getSE();
unsigned tripcount = se.getSmallConstantTripCount(loop);

but getSE returns NULL.

Can anybody help?