DWARF inlined frames support

backend/debug/dwarf/dwarf_flags/dwarf_flags.ml

@@ -141,3 +141,5 @@ let default_gdwarf_self_tail_calls = true
 let gdwarf_self_tail_calls = ref default_gdwarf_self_tail_calls
 
 let gdwarf_may_alter_codegen = ref false
+
+let dwarf_inlined_frames = ref false

backend/debug/dwarf/dwarf_flags/dwarf_flags.mli

@@ -68,3 +68,9 @@ val default_ddebug_invariants : bool
 val ddebug_invariants : bool ref
 
 val gdwarf_may_alter_codegen : bool ref
+
+(** Setting this to [true] will emit sufficient DWARF to get inlined frame
+    information, but won't emit information e.g. about local variables (unless
+    [restrict_to_upstream_dwarf] is set to [false], although that implies
+    this variable being set to [true]). *)
+val dwarf_inlined_frames : bool ref

backend/debug/dwarf/dwarf_ocaml/dwarf.ml

@@ -61,6 +61,9 @@ let create ~sourcefile ~unit_name ~asm_directives ~get_file_id ~code_begin
     DS.create ~compilation_unit_header_label ~compilation_unit_proto_die
       ~value_type_proto_die ~start_of_code_symbol debug_loc_table
       debug_ranges_table address_table location_list_table
+      ~get_file_num:get_file_id
+    (* CR mshinwell: does get_file_id successfully emit .file directives for
+       files we haven't seen before? *)
   in
   { state;
     asm_directives;
@@ -75,18 +78,29 @@ type fundecl =
   }
 
 let dwarf_for_fundecl t fundecl ~fun_end_label =
-  if not (!Clflags.debug && not !Dwarf_flags.restrict_to_upstream_dwarf)
+  if not
+       (!Clflags.debug
+       && ((not !Dwarf_flags.restrict_to_upstream_dwarf)
+          || !Dwarf_flags.dwarf_inlined_frames))
   then { fun_end_label; fundecl }
   else
     let available_ranges_vars, fundecl =
-      Profile.record "debug_available_ranges_vars"
-        (fun fundecl -> Available_ranges_vars.create fundecl)
+      if not !Dwarf_flags.restrict_to_upstream_dwarf
+      then
+        Profile.record "debug_available_ranges_vars"
+          (fun fundecl -> Available_ranges_vars.create fundecl)
+          ~accumulate:true fundecl
+      else Available_ranges_vars.empty, fundecl
+    in
+    let inlined_frame_ranges, fundecl =
+      Profile.record "debug_inlined_frame_ranges"
+        (fun fundecl -> Inlined_frame_ranges.create fundecl)
         ~accumulate:true fundecl
     in
     Dwarf_concrete_instances.for_fundecl ~get_file_id:t.get_file_id t.state
       fundecl
       ~fun_end_label:(Asm_label.create_int Text fun_end_label)
-      available_ranges_vars;
+      available_ranges_vars inlined_frame_ranges;
     { fun_end_label; fundecl }
 
 let emit t ~basic_block_sections ~binary_backend_available =

backend/debug/dwarf/dwarf_ocaml/dwarf_abstract_instances.ml

@@ -0,0 +1,180 @@
+(******************************************************************************
+ *                             flambda-backend                                *
+ *                       Mark Shinwell, Jane Street                           *
+ * -------------------------------------------------------------------------- *
+ *                               MIT License                                  *
+ *                                                                            *
+ * Copyright (c) 2024 Jane Street Group LLC                                   *
+ * [email protected]                                         *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included    *
+ * in all copies or substantial portions of the Software.                     *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING    *
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER        *
+ * DEALINGS IN THE SOFTWARE.                                                  *
+ ******************************************************************************)
+
+open! Asm_targets
+open! Dwarf_low
+open! Dwarf_high
+module DAH = Dwarf_attribute_helpers
+module DS = Dwarf_state
+module L = Linear
+
+let attributes fun_name =
+  [DAH.create_name fun_name; DAH.create_external ~is_visible_externally:true]
+
+let abstract_instance_proto_die_symbol ~fun_symbol =
+  Asm_symbol.create (Asm_symbol.to_raw_string fun_symbol ^ "_absinst")
+
+let add_empty state ~compilation_unit_proto_die ~fun_symbol ~demangled_name =
+  let abstract_instance_proto_die =
+    (* DWARF-5 specification section 3.3.8.1, page 82. *)
+    Proto_die.create ~parent:(Some compilation_unit_proto_die) ~tag:Subprogram
+      ~attribute_values:
+        [ DAH.create_name (Asm_symbol.encode fun_symbol);
+          DAH.create_linkage_name ~linkage_name:demangled_name;
+          DAH.create_external ~is_visible_externally:true ]
+      ()
+  in
+  let abstract_instance_proto_die_symbol =
+    abstract_instance_proto_die_symbol ~fun_symbol
+  in
+  Proto_die.set_name abstract_instance_proto_die
+    abstract_instance_proto_die_symbol;
+  Asm_symbol.Tbl.add
+    (DS.function_abstract_instances state)
+    fun_symbol
+    (abstract_instance_proto_die, abstract_instance_proto_die_symbol);
+  abstract_instance_proto_die, abstract_instance_proto_die_symbol
+
+let add_root state ~parent ~demangled_name fun_symbol ~location_attributes =
+  let attributes =
+    [ DAH.create_name (Asm_symbol.encode fun_symbol);
+      DAH.create_linkage_name ~linkage_name:demangled_name;
+      DAH.create_external ~is_visible_externally:true ]
+    @ location_attributes
+  in
+  let attribute_values =
+    attributes
+    @ [ (* We assume every function might potentially be inlined (and possibly
+           in the future), so we choose [DW_INL_inlined] as the most appropriate
+           setting for [DW_AT_inline], even if it doesn't seem exactly correct.
+           We must set something here to ensure that the subprogram is marked as
+           an abstract instance root. *)
+        (* CR mshinwell/xclerc: we could propagate "inline never" attributes to
+           this point *)
+        DAH.create_inline Inlined ]
+  in
+  let abstract_instance_proto_die_symbol =
+    abstract_instance_proto_die_symbol ~fun_symbol
+  in
+  DS.Debug.log "add_root: fun_symbol=%a\n" Asm_symbol.print fun_symbol;
+  let abstract_instance_proto_die =
+    match
+      Asm_symbol.Tbl.find (DS.function_abstract_instances state) fun_symbol
+    with
+    | proto_die, _symbol ->
+      (* See below in [find] *)
+      Proto_die.replace_all_attribute_values proto_die attribute_values
+    | exception Not_found ->
+      (* DWARF-5 specification section 3.3.8.1, page 82. *)
+      Proto_die.create ~parent:(Some parent) ~tag:Subprogram ~attribute_values
+        ()
+  in
+  Proto_die.set_name abstract_instance_proto_die
+    abstract_instance_proto_die_symbol;
+  Asm_symbol.Tbl.add (* or replace *)
+    (DS.function_abstract_instances state)
+    fun_symbol
+    (abstract_instance_proto_die, abstract_instance_proto_die_symbol);
+  abstract_instance_proto_die, abstract_instance_proto_die_symbol
+
+type decomposed_singleton_debuginfo =
+  { demangled_name : string;
+    fun_symbol : Asm_symbol.t;
+    compilation_unit : Compilation_unit.t
+  }
+
+let decompose_singleton_debuginfo dbg =
+  let orig_dbg = dbg in
+  match Debuginfo.to_items dbg with
+  | [({ dinfo_scopes; dinfo_function_symbol; _ } as item)] -> (
+    let module S = Debuginfo.Scoped_location in
+    let compilation_unit = S.compilation_unit dinfo_scopes in
+    let dbg = Debuginfo.of_items [item] in
+    let fun_symbol =
+      match dinfo_function_symbol with
+      | Some dinfo_function_symbol -> Asm_symbol.create dinfo_function_symbol
+      | None ->
+        Misc.fatal_errorf
+          "No function symbol in Debuginfo.t: orig_dbg=%a dbg=%a"
+          Debuginfo.print_compact_extended orig_dbg
+          Debuginfo.print_compact_extended dbg
+    in
+    let demangled_name =
+      Debuginfo.Scoped_location.string_of_scopes dinfo_scopes
+      |> Misc.remove_double_underscores
+    in
+    match compilation_unit with
+    | Some compilation_unit -> { demangled_name; fun_symbol; compilation_unit }
+    | None ->
+      Misc.fatal_errorf "No compilation unit extracted from: %a"
+        Debuginfo.print_compact_extended dbg)
+  | [] -> Misc.fatal_error "Empty Debuginfo.t"
+  | _ :: _ ->
+    Misc.fatal_errorf "Non-singleton Debuginfo.t: %a"
+      Debuginfo.print_compact_extended dbg
+
+type find_result =
+  | Ok of Asm_symbol.t
+  | External_unit of
+      { demangled_name : string;
+        fun_symbol : Asm_symbol.t
+      }
+
+let find state ~compilation_unit_proto_die (dbg : Debuginfo.t) =
+  let { demangled_name; fun_symbol; compilation_unit = dbg_comp_unit } =
+    decompose_singleton_debuginfo dbg
+  in
+  DS.Debug.log "found comp unit %a\n%!" Compilation_unit.print dbg_comp_unit;
+  let this_comp_unit = Compilation_unit.get_current_exn () in
+  if Compilation_unit.equal dbg_comp_unit this_comp_unit
+  then (
+    DS.Debug.log "looking in function_abstract_instances for %a\n%!"
+      Asm_symbol.print fun_symbol;
+    match
+      Asm_symbol.Tbl.find (DS.function_abstract_instances state) fun_symbol
+    with
+    | existing_instance ->
+      DS.Debug.log "...successfully found existing absint DIE\n%!";
+      Ok (snd existing_instance)
+    | exception Not_found ->
+      (* Fabricate an empty abstract instance DIE to fill in later, just in case
+         we haven't seen things in topological order. *)
+      (* CR mshinwell: does that actually happen now? *)
+      DS.Debug.log "...making empty absint DIE for %a\n" Asm_symbol.print
+        fun_symbol;
+      (* The empty abstract instances are parented to the compilation unit as
+         they might be referenced by other DIEs in a completely different scope
+         within the current unit. *)
+      let _, die_symbol =
+        add_empty state ~compilation_unit_proto_die ~fun_symbol ~demangled_name
+      in
+      Ok die_symbol)
+  else
+    (* abstract_instance_proto_die_symbol ~fun_symbol *)
+    (* See the call site of this function *)
+    External_unit { demangled_name; fun_symbol }

backend/debug/dwarf/dwarf_ocaml/dwarf_abstract_instances.mli

@@ -0,0 +1,59 @@
+(******************************************************************************
+ *                             flambda-backend                                *
+ *                       Mark Shinwell, Jane Street                           *
+ * -------------------------------------------------------------------------- *
+ *                               MIT License                                  *
+ *                                                                            *
+ * Copyright (c) 2024 Jane Street Group LLC                                   *
+ * [email protected]                                         *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included    *
+ * in all copies or substantial portions of the Software.                     *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING    *
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER        *
+ * DEALINGS IN THE SOFTWARE.                                                  *
+ ******************************************************************************)
+
+(** Management of DWARF "abstract instances" for functions. *)
+
+open! Asm_targets
+open! Dwarf_low
+open! Dwarf_high
+
+val attributes : string -> Dwarf_attribute_values.Attribute_value.t list
+
+(** Add an abstract instance root. *)
+val add_root :
+  Dwarf_state.t ->
+  parent:Proto_die.t ->
+  demangled_name:string ->
+  Asm_symbol.t ->
+  location_attributes:Dwarf_attribute_values.Attribute_value.t list ->
+  Proto_die.t * Asm_symbol.t
+
+type find_result = private
+  | Ok of Asm_symbol.t
+  | External_unit of
+      { demangled_name : string;
+        fun_symbol : Asm_symbol.t
+      }
+
+val find :
+  Dwarf_state.t ->
+  compilation_unit_proto_die:Proto_die.t ->
+  Debuginfo.t ->
+  find_result
+(* val find_maybe_in_another_unit_or_add : Dwarf_state.t ->
+   function_proto_die:Proto_die.t -> Linear.fundecl -> Asm_symbol.t option *)