third_party/llvm-7.0/llvm/examples/OCaml-Kaleidoscope/Chapter7/toplevel.ml

(*===----------------------------------------------------------------------===
 * Top-Level parsing and JIT Driver
 *===----------------------------------------------------------------------===*)

open Llvm
open Llvm_executionengine

(* top ::= definition | external | expression | ';' *)
let rec main_loop the_fpm the_execution_engine stream =
  match Stream.peek stream with
  | None -> ()

  (* ignore top-level semicolons. *)
  | Some (Token.Kwd ';') ->
      Stream.junk stream;
      main_loop the_fpm the_execution_engine stream

  | Some token ->
      begin
        try match token with
        | Token.Def ->
            let e = Parser.parse_definition stream in
            print_endline "parsed a function definition.";
            dump_value (Codegen.codegen_func the_fpm e);
        | Token.Extern ->
            let e = Parser.parse_extern stream in
            print_endline "parsed an extern.";
            dump_value (Codegen.codegen_proto e);
        | _ ->
            (* Evaluate a top-level expression into an anonymous function. *)
            let e = Parser.parse_toplevel stream in
            print_endline "parsed a top-level expr";
            let the_function = Codegen.codegen_func the_fpm e in
            dump_value the_function;

            (* JIT the function, returning a function pointer. *)
            let result = ExecutionEngine.run_function the_function [||]
              the_execution_engine in

            print_string "Evaluated to ";
            print_float (GenericValue.as_float Codegen.double_type result);
            print_newline ();
        with Stream.Error s | Codegen.Error s ->
          (* Skip token for error recovery. *)
          Stream.junk stream;
          print_endline s;
      end;
      print_string "ready> "; flush stdout;
      main_loop the_fpm the_execution_engine stream