title: LLVM IR: How to call a function in another .ll file
body: <p>I am writing LLVM IR code, can I call a function in another .ll file?</p>
  
  <p>For example:
  In a.ll file, there is a function foo();
  Can I use this function in b.ll, like just call foo? If so, how can I include a.ll</p>
  
  <p>Thanks</p>