Problem linking class to a pass in a loadable module

Dear LLVMers,

I have a class X that represents a set of Value* in a specific way.
That class is stored in two files: X.cpp and X.h

The class X works perfectly in a pass that I already have.

However, I need to use that class in some other passes, but I don't
want to have a copy of X.cpp and X.h in every pass folder.

I've tried to do the following:

- put X.h in the folder <llvm_root>/include/lllvm/Analysis
- put X.cpp in the folder <llvm_root>/lib/Analysis

- go to <llvm_root> and execute "make", to compile everything again,
with my new files

- change the includes of my passes to replace #include "X.h" by
#include "llvm/Analysis/X.h"

- compile my pass again

Until this point everything works fine. Although everything compiles
without any warnings,
I can't run my pass after I change the location of the source code of
the class X.

When I use the command:
raphael@ubuntu:~/$ opt -f -load -myPass test.bc

I get the following error message:
opt: symbol lookup error:
undefined symbol: _ZN4llvm5GraphC1Ei

I know that this error message means that X.h was successfully linked
to myPass, but when I call opt, opt can't find the actual
of the class and the methods declared in the header file.

Does anybody know what I did wrong or what I should do to make this work?