72 lines
3.6 KiB
OCaml
72 lines
3.6 KiB
OCaml
(**************************************************************************)
|
|
(* *)
|
|
(* OCaml *)
|
|
(* *)
|
|
(* Pierre Chambart, OCamlPro *)
|
|
(* Mark Shinwell and Leo White, Jane Street Europe *)
|
|
(* *)
|
|
(* Copyright 2013--2016 OCamlPro SAS *)
|
|
(* Copyright 2014--2016 Jane Street Group LLC *)
|
|
(* *)
|
|
(* All rights reserved. This file is distributed under the terms of *)
|
|
(* the GNU Lesser General Public License version 2.1, with the *)
|
|
(* special exception on linking described in the file LICENSE. *)
|
|
(* *)
|
|
(**************************************************************************)
|
|
|
|
[@@@ocaml.warning "+a-4-9-30-40-41-42"]
|
|
|
|
(** Description of the semantics of primitives, to be used for optimization
|
|
purposes.
|
|
|
|
"No effects" means that the primitive does not change the observable state
|
|
of the world. For example, it must not write to any mutable storage,
|
|
call arbitrary external functions or change control flow (e.g. by raising
|
|
an exception). Note that allocation is not "No effects" (see below).
|
|
|
|
It is assumed in the compiler that applications of primitives with no
|
|
effects, whose results are not used, may be eliminated. It is further
|
|
assumed that applications of primitives with no effects may be
|
|
duplicated (and thus possibly executed more than once).
|
|
|
|
(Exceptions arising from allocation points, for example "out of memory" or
|
|
exceptions propagated from finalizers or signal handlers, are treated as
|
|
"effects out of the ether" and thus ignored for our determination here
|
|
of effectfulness. The same goes for floating point operations that may
|
|
cause hardware traps on some platforms.)
|
|
|
|
"Only generative effects" means that a primitive does not change the
|
|
observable state of the world save for possibly affecting the state of
|
|
the garbage collector by performing an allocation. Applications of
|
|
primitives that only have generative effects and whose results are unused
|
|
may be eliminated by the compiler. However, unlike "No effects"
|
|
primitives, such applications will never be eligible for duplication.
|
|
|
|
"Arbitrary effects" covers all other primitives.
|
|
|
|
"No coeffects" means that the primitive does not observe the effects (in
|
|
the sense described above) of other expressions. For example, it must not
|
|
read from any mutable storage or call arbitrary external functions.
|
|
|
|
It is assumed in the compiler that, subject to data dependencies,
|
|
expressions with neither effects nor coeffects may be reordered with
|
|
respect to other expressions.
|
|
*)
|
|
|
|
type effects = No_effects | Only_generative_effects | Arbitrary_effects
|
|
type coeffects = No_coeffects | Has_coeffects
|
|
|
|
(** Describe the semantics of a primitive. This does not take into account of
|
|
the (non-)(co)effectfulness of the arguments in a primitive application.
|
|
To determine whether such an application is (co)effectful, the arguments
|
|
must also be analysed. *)
|
|
val for_primitive
|
|
: Lambda.primitive
|
|
-> effects * coeffects
|
|
|
|
type return_type =
|
|
| Float
|
|
| Other
|
|
|
|
val return_type_of_primitive : Lambda.primitive -> return_type
|