ocaml-gccjit is a OCaml library that provides bidings for
libgccjit. libgccjit is an embeddable
shared library available since 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 =
let ctx = Context.create () in
(* Create parameter "i" *)
let param_i = Param.create ctx Type.(get ctx Int) "i" in
(* Create the function *)
let fn = Function.create ctx Function.Exported Type.(get ctx Int) "square" [ param_i ] in
(* Create a basic block within the function *)
let block = Block.create ~name:"entry" fn in
(* This basic block is relatively simple *)
let expr = RValue.binary_op ctx Mult Type.(get ctx Int) (RValue.param param_i) (RValue.param param_i) in
Block.return block expr;
(* Having populated the context, compile it *)
let jit_result = Context.compile ctx in
(* Look up a specific machine code routine within the gccjit.Result, in this
case, the function we created above: *)
Result.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)Either opam install gccjit or:
opam pin add gccjit git://github.com/lukstafi/ocaml-gccjitNote: at the time of writing, using gccjit in bytecode requires patching Dune:
PR #8784.
Installing the package should also install the libgccjit library. If that is unsuccessful,
install libgccjit manually so that it is found by the C compiler using the -lgccjit flag.
Nicolas Ojeda Bar: n.oje.bar@gmail.com Lukasz Stafiniak: lukstafi@gmail.com