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|
open! Base
open Option_array
open Expect_test_helpers_core
let () =
let t = of_array [| None |] in
assert (
require_no_allocation [%here] (fun () ->
match get t 0 with
| None -> true
| Some _ -> false))
;;
let () =
let t = of_array [| Some 0 |] in
let get_some () =
match get t 0 with
| None -> false
| Some _ -> true
in
(* After inlining, [match get t 0 with] is:
{[
match
let cheap_option = Uniform_array.get t 0 in
if Cheap_option.is_some cheap_option
then Some (Cheap_option.value_unsafe cheap_option)
else None
with
]}
This situation is called "match-in-match" (the inner [if] is essentially a match).
The OCaml compiler and Flambda optimizer don't handle match-in-match well, and so
cannot eliminate the allocation of [Some]. Flambda2 is expected to eliminate the
allocation, at which point we can [require_no_allocation] (possibly annotating the
test with [@tags "fast-flambda"]).
Note that Flambda 2 only eliminates the allocation in optimized mode.
In classic mode, it will remain. This file is compiled with optimized mode.
*)
let compiler_eliminates_the_allocation =
(* [Version_util.x_library_inlining] is the whole reason this is a separate
executable. *)
Config.flambda2 && Version_util.x_library_inlining
in
if compiler_eliminates_the_allocation
then assert (require_no_allocation [%here] get_some)
else
let module Gc = Core.Gc.For_testing in
let _, { Gc.Allocation_report.minor_words_allocated; _ } =
Gc.measure_allocation get_some
in
if minor_words_allocated <= 2
then ()
else
failwith
(Printf.sprintf "Allocated more words than expected: %d" minor_words_allocated)
;;
|
