Remove experimental FDO support

doc/changes/changed/16198.md

@@ -0,0 +1,2 @@
+- Remove the experimental OCamlFDO integration, including the `(fdo ...)`
+  workspace field (#16198, @rgrinberg)

doc/reference/dune-workspace/context.rst

@@ -68,19 +68,6 @@ regular build context, or ``(opam ...)`` to use an opam switch.
   Relative paths are interpreted with respect to the workspace root. See
   :ref:`finding-root`.
 
-- ``(fdo <target_exe>)`` builds this context with feedback-directed
-  optimizations. It requires `OCamlFDO
-  <https://github.com/gretay-js/ocamlfdo>`__. ``<target_exe>`` is a path
-  interpreted relative to the workspace root (see :ref:`finding-root`).
-  ``<target_exe>`` specifies which executable to optimize. Users should define a
-  different context for each target executable built with FDO. The context name
-  is derived automatically from the default name and ``<target-exe>``, unless
-  explicitly specified using the ``(name ...)`` field. For example, if
-  ``<target_exe>`` is *src/foo.exe* in a default context, then the name of the
-  context is *default-fdo-foo* and the filename that contains execution counters
-  is *src/fdo.exe.fdo-profile*.  This feature is **experimental** and no
-  backward compatibility is implied.
-
 - ``(instrument_with <instrumentation_backend>)`` turns on instrumentation for
   the context. See :doc:`/instrumentation` for more information.
 

otherlibs/stdune/src/filename.ml

@@ -181,7 +181,6 @@ let dune_file = "dune-file"
 let dune_project = "dune-project"
 let dune_workspace = "dune-workspace"
 let expected = Extension.to_filename Extension.expected
-let fdo_profile = ".fdo-profile"
 let generated = ".generated"
 let git_dir_basename = ".git"
 let gmake = "gmake"
@@ -190,7 +189,6 @@ let jbuild = "jbuild"
 let json = Extension.to_filename Extension.json
 let js_dir_basename = Extension.to_filename Extension.js
 let lock_dune = "lock.dune"
-let linker_script = ".linker-script"
 let lock_dir_basename = ".lock"
 let make = "make"
 let merlin_conf_dir_basename = ".merlin-conf"

otherlibs/stdune/src/filename.mli

@@ -128,7 +128,6 @@ val dune_file : t
 val dune_project : t
 val dune_workspace : t
 val expected : t
-val fdo_profile : t
 val generated : t
 val git_dir_basename : t
 val gmake : t
@@ -137,7 +136,6 @@ val jbuild : t
 val json : t
 val js_dir_basename : t
 val lock_dune : t
-val linker_script : t
 val lock_dir_basename : t
 val make : t
 val merlin_conf_dir_basename : t

src/dune_rules/context.ml

@@ -69,7 +69,6 @@ type builder =
   { profile : Profile.t
   ; merlin : bool
   ; instrument_with : Lib_name.t list
-  ; fdo_target_exe : Path.t option
   ; dynamically_linked_foreign_archives : bool
   ; env_nodes : Env_nodes.t
   ; name : Context_name.t
@@ -107,7 +106,6 @@ module Builder = struct
     { profile = Profile.Dev
     ; merlin = false
     ; instrument_with = []
-    ; fdo_target_exe = None
     ; dynamically_linked_foreign_archives = false
     ; env_nodes = Env_nodes.empty
     ; name = Context_name.default
@@ -150,7 +148,6 @@ module Builder = struct
         ; toolchain
         ; paths
         ; loc = _
-        ; fdo_target_exe
         ; dynamically_linked_foreign_archives
         ; instrument_with
         ; merlin
@@ -169,7 +166,6 @@ module Builder = struct
     ; profile
     ; dynamically_linked_foreign_archives
     ; instrument_with
-    ; fdo_target_exe
     ; name
     ; env = Memo.return env
     ; findlib_toolchain = toolchain
@@ -197,7 +193,6 @@ let dynamically_linked_foreign_archives t =
     Ocaml_config.supports_shared_libraries ocaml.ocaml_config
 ;;
 
-let fdo_target_exe t = t.builder.fdo_target_exe
 let instrument_with t = t.builder.instrument_with
 let merlin t = t.builder.merlin
 let profile t = t.builder.profile
@@ -220,13 +215,11 @@ let host t =
 
 let to_dyn t : Dyn.t =
   let open Dyn in
-  let path = Path.to_dyn in
   record
     [ "name", Context_name.to_dyn t.builder.name
     ; "kind", Kind.to_dyn t.kind
     ; "profile", Profile.to_dyn t.builder.profile
     ; "merlin", Bool t.builder.merlin
-    ; "fdo_target_exe", option path t.builder.fdo_target_exe
     ; "build_dir", Path.Build.to_dyn t.build_dir
     ; "instrument_with", (list Lib_name.to_dyn) t.builder.instrument_with
     ]
@@ -509,8 +502,6 @@ let create (builder : Builder.t) ~(kind : Kind.t) =
                 toolchain, `Lock)
          in
          Ocaml_toolchain.register_response_file_support ocaml;
-         if Option.is_some builder.fdo_target_exe
-         then Ocaml_toolchain.check_fdo_support ocaml builder.name;
          ocaml, env)
   in
   let default_ocamlpath =

src/dune_rules/context.mli

@@ -59,10 +59,6 @@ val to_dyn_concise : t -> Dyn.t
 val name : t -> Context_name.t
 val which : t -> Filename.t -> Path.t option Memo.t
 
-(** [Some path/to/foo.exe] if this contexts is for feedback-directed
-    optimization of target path/to/foo.exe *)
-val fdo_target_exe : t -> Path.t option
-
 (** By default Dune builds and installs dynamically linked foreign
     archives (usually named [dll*.so]). It is possible to disable this by
     adding (disable_dynamically_linked_foreign_archives true) to the workspace

src/dune_rules/ctypes/ctypes_rules.ml

@@ -186,16 +186,11 @@ let build_c_program
       let+ ocaml = Action_builder.of_memo ocaml in
       let use_standard_flags = Dune_project.use_standard_c_and_cxx_flags project in
       let cfg = ocaml.ocaml_config in
-      let fdo_flags = Command.Args.As (Fdo.c_flags ctx) in
       match use_standard_flags with
-      | Some true -> fdo_flags
+      | Some true -> Command.Args.empty
       | None | Some false ->
         (* In dune < 2.8 flags from ocamlc_config are always added *)
-        S
-          [ As (Ocaml_config.ocamlc_cflags cfg)
-          ; As (Ocaml_config.ocamlc_cppflags cfg)
-          ; fdo_flags
-          ]
+        S [ As (Ocaml_config.ocamlc_cflags cfg); As (Ocaml_config.ocamlc_cppflags cfg) ]
     in
     let open Action_builder.O in
     let* expander = Action_builder.of_memo (Super_context.expander sctx ~dir) in

src/dune_rules/exe.ml

@@ -179,15 +179,11 @@ let link_exe
   let dir = Compilation_context.dir cctx in
   let mode = Link_mode.mode linkage_mode in
   let exe = exe_path_from_name cctx ~name ~linkage in
-  let* action_with_targets =
+  let action_with_targets =
     let ocaml_flags = Ocaml_flags.get (Compilation_context.flags cctx) (Ocaml mode) in
     let prefix =
       Cm_files.top_sorted_objects_and_cms cm_files ~mode |> Action_builder.dyn_paths_unit
     in
-    let+ fdo_linker_script_flags =
-      let fdo_linker_script = Fdo.Linker_script.create cctx (Path.build exe) in
-      Fdo.Linker_script.flags fdo_linker_script
-    in
     let open Action_builder.With_targets.O in
     (* NB. Below we take care to pass [link_args] last on the command-line for
        the following reason: [link_args] contains the list of foreign libraries
@@ -236,10 +232,10 @@ let link_exe
           ; Dyn
               (let top_sorted_cms = Cm_files.top_sorted_cms cm_files ~mode in
                Action_builder.map top_sorted_cms ~f:(fun x -> Command.Args.Deps x))
-          ; fdo_linker_script_flags
           ; Dyn link_args
           ]
-  and* mode =
+  in
+  let* mode =
     let sctx = Compilation_context.super_context cctx in
     let* expander = Super_context.expander sctx ~dir in
     Rule_mode_expand.expand_optional_promote ~expander ~dir promote