ocaml-gccjit is a OCaml library that provides bidings for
libgccjit. libgccjit is an embeddable
shared library included in GCC 5 for adding compilation to existing programs
using GCC as the backend.
For example, consider this C function:
int square (int i)
{
return i * i;
}We can construct this function at runtime using libgccjit, as follows:
open Gccjit
let square =
(* Create a compilation context *)
let ctx = acquire_context () in
let int_type = get_standard_type ctx Int in
(* Create parameter "i" *)
let param_i = new_param ctx int_type "i" in
(* Create the function *)
let fn = new_function ctx Exported int_type "square" [ param_i ] in
(* Create a basic block within the function *)
let block = new_block fn ~name:"entry" () in
(* This basic block is relatively simple *)
let expr = new_binary_op ctx Mult int_type param_i param_i in
end_with_return block expr;
(* Having populated the context, compile it *)
let jit_result = compile ctx in
(* Look up a specific machine code routine within the gccjit.Result, in this
case, the function we created above: *)
get_code jit_result "square" Ctypes.(int @-> returning int)We can now call the function by doing simply
(* Now try running the code *)
Printf.printf "square(5) = %d\n%!" (square 5)opam install gccjit
In order for compilation to be successful the library libgccjit needs to be
found by the C compiler using the -lgccjit flag. If the libgccjit library
in your system is a non-standard location, please set the LIBGCCJIT_DIR
environment variable before installing this package, like this:
LIBGCCJIT_DIR=<directory where libgccjit lives> opam install gccjit
Nicolas Ojeda Bar: [email protected]