OCaml LLVM JIT minimal setup

dune

(executable
  (name llvmjit)
  (libraries
    llvm
    llvm.executionengine
    ctypes.foreign))

llvmjit.ml

module L = Llvm

let context = L.global_context ()
let the_module = L.create_module context "my module"
let builder = L.builder context

let double_type = L.double_type context
let top_func_type = L.function_type double_type [||]
let the_function = L.declare_function "__toplevel1" top_func_type the_module
let bb = L.append_block context "entry" the_function

let () = L.position_at_end bb builder

let n = L.const_float double_type 1.0
let m = L.const_float double_type 2.0
let ret_val = L.build_add n m "addtmp" builder
let () = ignore @@ L.build_ret ret_val builder

let _ = Llvm_executionengine.initialize ()
let the_execution_engine = Llvm_executionengine.create the_module

let () = L.dump_value the_function
let fp =
  Llvm_executionengine.get_function_address
    function_name
    (Foreign.funptr Ctypes.(void @-> returning double))
    the_execution_engine
let () = print_endline @@ string_of_float @@ fp ()