Various improvements

* Use `Coercion.t` rather than `Coercion.t option` in many places
* Use `Rec_info.t` again where sensible (in making inlining decisions,
  for instance), but redefine it as `unit` pending the next phase of
  `Rec_info` overhaul
* Add simple `int` fields to `Coercion.t` for changing recursion depth;
  this is simpler than what we'll actually need but specific enough that
  we can test meaningfully (e.g., we can tell whether coercions are
  composed in the right order)

Author: lukemaurer

.depend

@@ -3892,10 +3892,15 @@ asmcomp/debug/reg_with_debug_info.cmi : \
     asmcomp/reg.cmi \
     middle_end/backend_var.cmi
 middle_end/flambda/compilenv_deps/coercion.cmo : \
+    utils/misc.cmi \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmi \
     middle_end/flambda/compilenv_deps/coercion.cmi
 middle_end/flambda/compilenv_deps/coercion.cmx : \
+    utils/misc.cmx \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmx \
     middle_end/flambda/compilenv_deps/coercion.cmi
-middle_end/flambda/compilenv_deps/coercion.cmi :
+middle_end/flambda/compilenv_deps/coercion.cmi : \
+    middle_end/flambda/compilenv_deps/rec_info.cmi
 middle_end/flambda/compilenv_deps/compilation_unit.cmo : \
     utils/misc.cmi \
     middle_end/flambda/compilenv_deps/linkage_name.cmi \
@@ -3950,10 +3955,17 @@ middle_end/flambda/compilenv_deps/patricia_tree.cmi : \
     utils/numbers.cmi \
     utils/identifiable.cmi
 middle_end/flambda/compilenv_deps/rec_info.cmo : \
+    utils/misc.cmi \
+    utils/identifiable.cmi \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmi \
     middle_end/flambda/compilenv_deps/rec_info.cmi
 middle_end/flambda/compilenv_deps/rec_info.cmx : \
+    utils/misc.cmx \
+    utils/identifiable.cmx \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmx \
     middle_end/flambda/compilenv_deps/rec_info.cmi
-middle_end/flambda/compilenv_deps/rec_info.cmi :
+middle_end/flambda/compilenv_deps/rec_info.cmi : \
+    utils/identifiable.cmi
 middle_end/flambda/compilenv_deps/reg_width_things.cmo : \
     utils/targetint.cmi \
     middle_end/flambda/compilenv_deps/target_imm.cmi \
@@ -5217,7 +5229,6 @@ middle_end/flambda/inlining/inlining_decision.cmo : \
     middle_end/flambda/terms/function_declaration.cmi \
     middle_end/flambda/terms/flambda.cmi \
     middle_end/flambda/simplify/env/downwards_env.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     utils/clflags.cmi \
     middle_end/flambda/inlining/inlining_decision.cmi
 middle_end/flambda/inlining/inlining_decision.cmx : \
@@ -5229,17 +5240,16 @@ middle_end/flambda/inlining/inlining_decision.cmx : \
     middle_end/flambda/terms/function_declaration.cmx \
     middle_end/flambda/terms/flambda.cmx \
     middle_end/flambda/simplify/env/downwards_env.cmx \
-    middle_end/flambda/compilenv_deps/coercion.cmx \
     utils/clflags.cmx \
     middle_end/flambda/inlining/inlining_decision.cmi
 middle_end/flambda/inlining/inlining_decision.cmi : \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     middle_end/flambda/types/inlining/inlining_state.cmi \
     middle_end/flambda/inlining/inlining_cost.cmi \
     middle_end/flambda/basic/inline_attribute.cmi \
     middle_end/flambda/terms/function_declaration.cmi \
     middle_end/flambda/terms/flambda.cmi \
-    middle_end/flambda/simplify/env/downwards_env.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi
+    middle_end/flambda/simplify/env/downwards_env.cmi
 middle_end/flambda/inlining/inlining_report.cmo : \
     utils/misc.cmi \
     middle_end/flambda/inlining/inlining_decision.cmi \
@@ -6166,7 +6176,6 @@ middle_end/flambda/simplify/simplify.cmo : \
     middle_end/flambda/simplify/env/continuation_env_and_param_types.cmi \
     middle_end/flambda/basic/continuation.cmi \
     middle_end/flambda/compilenv_deps/compilation_unit.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/basic/code_id.cmi \
     middle_end/flambda/types/structures/code_age_relation.cmi \
     middle_end/flambda/basic/closure_id.cmi \
@@ -6237,7 +6246,6 @@ middle_end/flambda/simplify/simplify.cmx : \
     middle_end/flambda/simplify/env/continuation_env_and_param_types.cmx \
     middle_end/flambda/basic/continuation.cmx \
     middle_end/flambda/compilenv_deps/compilation_unit.cmx \
-    middle_end/flambda/compilenv_deps/coercion.cmx \
     middle_end/flambda/basic/code_id.cmx \
     middle_end/flambda/types/structures/code_age_relation.cmx \
     middle_end/flambda/basic/closure_id.cmx \
@@ -6309,7 +6317,6 @@ middle_end/flambda/simplify/simplify_apply_expr.rec.cmo : \
     lambda/debuginfo.cmi \
     middle_end/flambda/basic/continuation.cmi \
     middle_end/flambda/compilenv_deps/compilation_unit.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/basic/code_id.cmi \
     middle_end/flambda/types/structures/code_age_relation.cmi \
     middle_end/flambda/basic/closure_id.cmi \
@@ -6342,7 +6349,6 @@ middle_end/flambda/simplify/simplify_apply_expr.rec.cmx : \
     lambda/debuginfo.cmx \
     middle_end/flambda/basic/continuation.cmx \
     middle_end/flambda/compilenv_deps/compilation_unit.cmx \
-    middle_end/flambda/compilenv_deps/coercion.cmx \
     middle_end/flambda/basic/code_id.cmx \
     middle_end/flambda/types/structures/code_age_relation.cmx \
     middle_end/flambda/basic/closure_id.cmx \
@@ -6696,7 +6702,6 @@ middle_end/flambda/simplify/simplify_set_of_closures.rec.cmo : \
     middle_end/flambda/simplify/env/downwards_acc.cmi \
     middle_end/flambda/basic/continuation.cmi \
     middle_end/flambda/compilenv_deps/compilation_unit.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/basic/code_id.cmi \
     middle_end/flambda/types/structures/code_age_relation.cmi \
     middle_end/flambda/basic/closure_id.cmi \
@@ -6735,7 +6740,6 @@ middle_end/flambda/simplify/simplify_set_of_closures.rec.cmx : \
     middle_end/flambda/simplify/env/downwards_acc.cmx \
     middle_end/flambda/basic/continuation.cmx \
     middle_end/flambda/compilenv_deps/compilation_unit.cmx \
-    middle_end/flambda/compilenv_deps/coercion.cmx \
     middle_end/flambda/basic/code_id.cmx \
     middle_end/flambda/types/structures/code_age_relation.cmx \
     middle_end/flambda/basic/closure_id.cmx \
@@ -8785,6 +8789,7 @@ middle_end/flambda/types/flambda_type.cmo : \
     middle_end/flambda/basic/scope.cmi \
     middle_end/flambda/types/structures/row_like_maps_to_intf.cmo \
     middle_end/flambda/basic/reg_width_const.cmi \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     middle_end/flambda/types/structures/product_intf.cmo \
     utils/printing_cache.cmi \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmi \
@@ -8838,6 +8843,7 @@ middle_end/flambda/types/flambda_type.cmx : \
     middle_end/flambda/basic/scope.cmx \
     middle_end/flambda/types/structures/row_like_maps_to_intf.cmx \
     middle_end/flambda/basic/reg_width_const.cmx \
+    middle_end/flambda/compilenv_deps/rec_info.cmx \
     middle_end/flambda/types/structures/product_intf.cmx \
     utils/printing_cache.cmx \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmx \
@@ -8883,6 +8889,7 @@ middle_end/flambda/types/flambda_type.cmi : \
     middle_end/flambda/basic/simple.cmi \
     middle_end/flambda/basic/scope.cmi \
     middle_end/flambda/basic/reg_width_const.cmi \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     utils/printing_cache.cmi \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmi \
     middle_end/flambda/types/basic/or_unknown.cmi \
@@ -9034,6 +9041,7 @@ middle_end/flambda/types/type_grammar.rec.cmi : \
     lambda/tag.cmi \
     middle_end/flambda/basic/simple.cmi \
     middle_end/flambda/basic/reg_width_const.cmi \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     utils/printing_cache.cmi \
     middle_end/flambda/types/basic/or_unknown.cmi \
     middle_end/flambda/types/basic/or_bottom.cmi \
@@ -9218,33 +9226,34 @@ middle_end/flambda/types/basic/var_within_closure_set.cmi : \
     utils/identifiable.cmi
 middle_end/flambda/types/env/aliases.cmo : \
     middle_end/flambda/compilenv_deps/variable.cmi \
-    middle_end/flambda/compilenv_deps/reg_width_things.cmi \
+    middle_end/flambda/basic/simple.cmi \
     middle_end/flambda/naming/name_mode.cmi \
     middle_end/flambda/basic/name.cmi \
     utils/misc.cmi \
     middle_end/flambda/cmx/ids_for_export.cmi \
-    utils/identifiable.cmi \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmi \
+    middle_end/flambda/compilenv_deps/coercion.cmi \
     utils/clflags.cmi \
     middle_end/flambda/types/env/binding_time.cmi \
     middle_end/flambda/types/env/aliases.cmi
 middle_end/flambda/types/env/aliases.cmx : \
     middle_end/flambda/compilenv_deps/variable.cmx \
-    middle_end/flambda/compilenv_deps/reg_width_things.cmx \
+    middle_end/flambda/basic/simple.cmx \
     middle_end/flambda/naming/name_mode.cmx \
     middle_end/flambda/basic/name.cmx \
     utils/misc.cmx \
     middle_end/flambda/cmx/ids_for_export.cmx \
-    utils/identifiable.cmx \
+    middle_end/flambda/compilenv_deps/flambda_colours.cmx \
+    middle_end/flambda/compilenv_deps/coercion.cmx \
     utils/clflags.cmx \
     middle_end/flambda/types/env/binding_time.cmx \
     middle_end/flambda/types/env/aliases.cmi
 middle_end/flambda/types/env/aliases.cmi : \
-    middle_end/flambda/compilenv_deps/reg_width_things.cmi \
+    middle_end/flambda/basic/simple.cmi \
     middle_end/flambda/naming/name_mode.cmi \
     middle_end/flambda/basic/name.cmi \
-    middle_end/flambda/cmx/ids_for_export.cmi \
-    utils/identifiable.cmi \
     middle_end/flambda/cmx/contains_ids.cmo \
+    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/types/env/binding_time.cmi
 middle_end/flambda/types/env/binding_time.cmo : \
     utils/numbers.cmi \
@@ -9336,7 +9345,6 @@ middle_end/flambda/types/env/typing_env.rec.cmi : \
     middle_end/flambda/types/kinds/flambda_kind.cmi \
     middle_end/flambda/simplify/env/continuation_use_kind.cmi \
     middle_end/flambda/compilenv_deps/compilation_unit.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/basic/code_id.cmi \
     middle_end/flambda/types/structures/code_age_relation.cmi \
     middle_end/flambda/basic/apply_cont_rewrite_id.cmi \
@@ -9492,31 +9500,32 @@ middle_end/flambda/types/structures/code_age_relation.cmi : \
     middle_end/flambda/compilenv_deps/compilation_unit.cmi \
     middle_end/flambda/basic/code_id.cmi
 middle_end/flambda/types/structures/function_declaration_type.rec.cmo : \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmi \
     middle_end/flambda/types/basic/or_bottom.cmi \
     middle_end/flambda/naming/name_permutation.cmi \
     middle_end/flambda/naming/name_occurrences.cmi \
     middle_end/flambda/naming/name_mode.cmi \
     middle_end/flambda/cmx/ids_for_export.cmi \
     lambda/debuginfo.cmi \
-    middle_end/flambda/compilenv_deps/coercion.cmi \
     middle_end/flambda/basic/code_id.cmi \
     middle_end/flambda/types/structures/code_age_relation.cmi \
     middle_end/flambda/types/structures/function_declaration_type.rec.cmi
 middle_end/flambda/types/structures/function_declaration_type.rec.cmx : \
+    middle_end/flambda/compilenv_deps/rec_info.cmx \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmx \
     middle_end/flambda/types/basic/or_bottom.cmx \
     middle_end/flambda/naming/name_permutation.cmx \
     middle_end/flambda/naming/name_occurrences.cmx \
     middle_end/flambda/naming/name_mode.cmx \
     middle_end/flambda/cmx/ids_for_export.cmx \
     lambda/debuginfo.cmx \
-    middle_end/flambda/compilenv_deps/coercion.cmx \
     middle_end/flambda/basic/code_id.cmx \
     middle_end/flambda/types/structures/code_age_relation.cmx \
     middle_end/flambda/types/structures/function_declaration_type.rec.cmi
 middle_end/flambda/types/structures/function_declaration_type.rec.cmi : \
     middle_end/flambda/types/structures/type_structure_intf.cmo \
+    middle_end/flambda/compilenv_deps/rec_info.cmi \
     middle_end/flambda/types/basic/or_unknown_or_bottom.cmi \
     middle_end/flambda/types/basic/or_bottom.cmi \
     lambda/debuginfo.cmi \

middle_end/flambda/basic/simple.ml

@@ -55,23 +55,28 @@ let const_from_descr descr = const (RWC.of_descr descr)
 
 let without_coercion t = pattern_match t ~name ~const
 
-let compose_coercion t ~newer_coercion =
-  if is_const t then None
+let apply_coercion t applied_coercion =
+  if Coercion.is_id applied_coercion then Some t
   else
-    match newer_coercion with
-    | None -> Some t
-    | Some newer_coercion ->
-      let coercion =
-        match coercion t with
-        | None -> newer_coercion
-        | Some older_coercion ->
-          Coercion.compose older_coercion ~newer:newer_coercion
-      in
-      Some (with_coercion (without_coercion t) coercion)
+    let coercion = 
+      let existing_coercion = coercion t in
+      if Coercion.is_id existing_coercion then Some applied_coercion
+      else Coercion.compose existing_coercion ~then_:applied_coercion
+    in
+    coercion
+    |> Option.map (fun coercion -> with_coercion (without_coercion t) coercion)
+
+let apply_coercion_exn t applied_coercion =
+  match apply_coercion t applied_coercion with
+  | Some t -> t
+  | None ->
+    Misc.fatal_errorf "Cannot apply coercion %a to %a"
+      print t
+      Coercion.print applied_coercion
 
 (* CR mshinwell: Make naming consistent with [Name] re. the option type *)
 
-(* CR mshinwell: Careful that Coercion doesn't get dropped using the
+(* CR mshinwell: Careful that coercions don't get dropped using the
    following *)
 
 let [@inline always] must_be_var t =
@@ -118,9 +123,7 @@ let apply_name_permutation t perm =
     let new_name = Name_permutation.apply_name perm old_name in
     if old_name == new_name then t
     else
-      match coercion t with
-      | None -> name new_name
-      | Some coercion -> with_coercion (name new_name) coercion
+      with_coercion (name new_name) (coercion t)
   in
   pattern_match t ~const:(fun _ -> t) ~name
 

middle_end/flambda/basic/simple.mli

@@ -23,7 +23,9 @@ include module type of struct include Reg_width_things.Simple end
 
 include Contains_names.S with type t := t
 
-val compose_coercion : t -> newer_coercion:Coercion.t option -> t option
+val apply_coercion : t -> Coercion.t -> t option
+
+val apply_coercion_exn : t -> Coercion.t -> t
 
 val without_coercion : t -> t
 
@@ -64,7 +66,7 @@ val const_from_descr : Reg_width_const.Descr.t -> t
 
 val map_name : t -> f:(Name.t -> Name.t) -> t
 
-val to_name : t -> (Coercion.t option * Name.t) option
+val to_name : t -> (Coercion.t * Name.t) option
 
 (* CR mshinwell: remove these next two? *)
 val map_var : t -> f:(Variable.t -> Variable.t) -> t

middle_end/flambda/cmx/ids_for_export.ml

@@ -75,8 +75,8 @@ let add_name t name =
 let add_simple t simple =
   let simples =
     match Simple.coercion simple with
-    | None -> t.simples
-    | Some _ -> Simple.Set.add simple t.simples
+    | Id -> t.simples
+    | _ -> Simple.Set.add simple t.simples
   in
   let t = { t with simples; } in
   Simple.pattern_match simple
@@ -92,10 +92,10 @@ let add_continuation t continuation =
 let from_simple simple =
   let simples =
     match Simple.coercion simple with
-    | None ->
+    | Id ->
       (* This simple will not be in the grand_table_of_simples *)
       Simple.Set.empty
-    | Some _ -> Simple.Set.singleton simple
+    | _ -> Simple.Set.singleton simple
   in
   Simple.pattern_match simple
     ~const:(fun const ->
@@ -200,11 +200,11 @@ module Import_map = struct
     | simple -> simple
     | exception Not_found ->
       begin match Simple.coercion simple with
-      | None ->
+      | Id ->
         Simple.pattern_match simple
           ~name:(fun n -> Simple.name (name t n))
           ~const:(fun c -> Simple.const (const t c))
-      | Some _coercion -> simple
+      | _ -> simple
       end
 
   let closure_var_is_used t var =