Combining merlin and llvm module

sorry to ask a newbee question.

I installed llvm via opam install llvm, and when I do

open Llvm

merlin recognizes all imported symbols, but when I do “goto definition” in Emacs, it doesn’t jump to the definition and say
“Needed cmt file of module ‘Llvm’ to locate ‘llmdkind’ but it is not present” instead.

should I pass in special flag to make opam generate cmt files? or how should I proceed in this case?