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| 1 | (**************************************************************************) |
| 2 | (* *) |
| 3 | (* OCaml *) |
| 4 | (* *) |
| 5 | (* Pierre Chambart, OCamlPro *) |
| 6 | (* Mark Shinwell and Leo White, Jane Street Europe *) |
| 7 | (* *) |
| 8 | (* Copyright 2013--2016 OCamlPro SAS *) |
| 9 | (* Copyright 2014--2016 Jane Street Group LLC *) |
| 10 | (* *) |
| 11 | (* All rights reserved. This file is distributed under the terms of *) |
| 12 | (* the GNU Lesser General Public License version 2.1, with the *) |
| 13 | (* special exception on linking described in the file LICENSE. *) |
| 14 | (* *) |
| 15 | (**************************************************************************) |
| 16 | |
| 17 | [@@@ocaml.warning "+a-4-9-30-40-41-42"] |
| 18 | |
| 19 | (** Description of the semantics of primitives, to be used for optimization |
| 20 | purposes. |
| 21 | |
| 22 | "No effects" means that the primitive does not change the observable state |
| 23 | of the world. For example, it must not write to any mutable storage, |
| 24 | call arbitrary external functions or change control flow (e.g. by raising |
| 25 | an exception). Note that allocation is not "No effects" (see below). |
| 26 | |
| 27 | It is assumed in the compiler that applications of primitives with no |
| 28 | effects, whose results are not used, may be eliminated. It is further |
| 29 | assumed that applications of primitives with no effects may be |
| 30 | duplicated (and thus possibly executed more than once). |
| 31 | |
| 32 | (Exceptions arising from allocation points, for example "out of memory" or |
| 33 | exceptions propagated from finalizers or signal handlers, are treated as |
| 34 | "effects out of the ether" and thus ignored for our determination here |
| 35 | of effectfulness. The same goes for floating point operations that may |
| 36 | cause hardware traps on some platforms.) |
| 37 | |
| 38 | "Only generative effects" means that a primitive does not change the |
| 39 | observable state of the world save for possibly affecting the state of |
| 40 | the garbage collector by performing an allocation. Applications of |
| 41 | primitives that only have generative effects and whose results are unused |
| 42 | may be eliminated by the compiler. However, unlike "No effects" |
| 43 | primitives, such applications will never be eligible for duplication. |
| 44 | |
| 45 | "Arbitrary effects" covers all other primitives. |
| 46 | |
| 47 | "No coeffects" means that the primitive does not observe the effects (in |
| 48 | the sense described above) of other expressions. For example, it must not |
| 49 | read from any mutable storage or call arbitrary external functions. |
| 50 | |
| 51 | It is assumed in the compiler that, subject to data dependencies, |
| 52 | expressions with neither effects nor coeffects may be reordered with |
| 53 | respect to other expressions. |
| 54 | *) |
| 55 | |
| 56 | type effects = No_effects | Only_generative_effects | Arbitrary_effects |
| 57 | type coeffects = No_coeffects | Has_coeffects |
| 58 | |
| 59 | (** Describe the semantics of a primitive. This does not take into account of |
| 60 | the (non-)(co)effectfulness of the arguments in a primitive application. |
| 61 | To determine whether such an application is (co)effectful, the arguments |
| 62 | must also be analysed. *) |
| 63 | val for_primitive: Clambda_primitives.primitive -> effects * coeffects |
| 64 | |
| 65 | type return_type = |
| 66 | | Float |
| 67 | | Other |
| 68 | |
| 69 | val return_type_of_primitive: Clambda_primitives.primitive -> return_type |
| 70 |