flambda-backend: Add [@@Builtin] attribute to Primitives (#11 part 1)

Author: gretay-js

asmcomp/cmm_helpers.ml

@@ -1358,6 +1358,7 @@ let int64_native_prim name arity ~alloc =
   let rec make_args = function 0 -> [] | n -> u64 :: make_args (n - 1) in
   Primitive.make ~name ~native_name:(name ^ "_native")
     ~alloc
+    ~c_builtin:false
     ~native_repr_args:(make_args arity)
     ~native_repr_res:u64
 

typing/primitive.ml

@@ -30,6 +30,7 @@ type description =
   { prim_name: string;         (* Name of primitive  or C function *)
     prim_arity: int;           (* Number of arguments *)
     prim_alloc: bool;          (* Does it allocates or raise? *)
+    prim_c_builtin: bool;        (* Is the compiler allowed to replace it? *)
     prim_native_name: string;  (* Name of C function for the nat. code gen. *)
     prim_native_repr_args: native_repr list;
     prim_native_repr_res: native_repr }
@@ -69,14 +70,17 @@ let simple ~name ~arity ~alloc =
   {prim_name = name;
    prim_arity = arity;
    prim_alloc = alloc;
+   prim_c_builtin = false;
    prim_native_name = "";
    prim_native_repr_args = make_native_repr_args arity Same_as_ocaml_repr;
    prim_native_repr_res = Same_as_ocaml_repr}
 
-let make ~name ~alloc ~native_name ~native_repr_args ~native_repr_res =
+let make ~name ~alloc ~c_builtin
+      ~native_name ~native_repr_args ~native_repr_res =
   {prim_name = name;
    prim_arity = List.length native_repr_args;
    prim_alloc = alloc;
+   prim_c_builtin = c_builtin;
    prim_native_name = native_name;
    prim_native_repr_args = native_repr_args;
    prim_native_repr_res = native_repr_res}
@@ -98,6 +102,10 @@ let parse_declaration valdecl ~native_repr_args ~native_repr_res =
     Attr_helper.has_no_payload_attribute ["noalloc"; "ocaml.noalloc"]
       valdecl.pval_attributes
   in
+  let builtin_attribute =
+    Attr_helper.has_no_payload_attribute ["builtin"; "ocaml.builtin"]
+      valdecl.pval_attributes
+  in
   if old_style_float &&
      not (List.for_all is_ocaml_repr native_repr_args &&
           is_ocaml_repr native_repr_res) then
@@ -131,6 +139,7 @@ let parse_declaration valdecl ~native_repr_args ~native_repr_res =
   {prim_name = name;
    prim_arity = arity;
    prim_alloc = not noalloc;
+   prim_c_builtin = builtin_attribute;
    prim_native_name = native_name;
    prim_native_repr_args = native_repr_args;
    prim_native_repr_res = native_repr_res}
@@ -155,6 +164,7 @@ let rec add_native_repr_attributes ty attrs =
 let oattr_unboxed = { oattr_name = "unboxed" }
 let oattr_untagged = { oattr_name = "untagged" }
 let oattr_noalloc = { oattr_name = "noalloc" }
+let oattr_builtin = { oattr_name = "builtin" }
 
 let print p osig_val_decl =
   let prims =
@@ -169,6 +179,7 @@ let print p osig_val_decl =
   let all_unboxed = for_all is_unboxed in
   let all_untagged = for_all is_untagged in
   let attrs = if p.prim_alloc then [] else [oattr_noalloc] in
+  let attrs = if p.prim_c_builtin then oattr_builtin::attrs else attrs in
   let attrs =
     if all_unboxed then
       oattr_unboxed :: attrs

typing/primitive.mli

@@ -29,6 +29,12 @@ type description = private
   { prim_name: string;         (* Name of primitive  or C function *)
     prim_arity: int;           (* Number of arguments *)
     prim_alloc: bool;          (* Does it allocates or raise? *)
+    prim_c_builtin: bool;
+    (* When [prim_c_builtin] is true, the native compiler is allowed to rewrite
+       calls to the external C function that implements this primitive,
+       based on its name [prim_name], into a predetermined instruction sequence.
+       [prim_c_builtin] is ignored on compiler primitives
+       whose name [prim_name] starts with %. *)
     prim_native_name: string;  (* Name of C function for the nat. code gen. *)
     prim_native_repr_args: native_repr list;
     prim_native_repr_res: native_repr }
@@ -44,6 +50,7 @@ val simple
 val make
   :  name:string
   -> alloc:bool
+  -> c_builtin:bool
   -> native_name:string
   -> native_repr_args: native_repr list
   -> native_repr_res: native_repr