Merge pull request #3773 from BuckleScript/fix_tail

Refine tail position property

Author: bobzhang

jscomp/core/js_output.ml

@@ -54,15 +54,15 @@ let output_of_expression
     (continuation : continuation)
     (exp : J.expression) ~(no_effects: bool Lazy.t)  =
   match continuation with
-  | EffectCall  ReturnFalse ->
+  | EffectCall  Not_tail ->
     if Lazy.force no_effects 
     then dummy
     else {block = []; value  = Some exp ; output_finished = False}
   | Declare (kind, n)->
     make [ S.define_variable ~kind n  exp]
   | Assign n  ->
     make [S.assign n exp ]
-  | EffectCall (ReturnTrue _) ->
+  | EffectCall (Maybe_tail_is_return _) ->
     make [S.return_stmt  exp] ~output_finished:True
   | NeedValue _ ->
     {block = []; value = Some exp; output_finished = False }
@@ -72,8 +72,8 @@ let output_of_block_and_expression
     (continuation : continuation)
     (block : J.block) exp : t =
   match continuation with
-  | EffectCall ReturnFalse -> make block ~value:exp
-  | EffectCall (ReturnTrue _) -> 
+  | EffectCall Not_tail -> make block ~value:exp
+  | EffectCall (Maybe_tail_is_return _) -> 
     make (Ext_list.append_one block (S.return_stmt exp)) ~output_finished:True
   | Declare (kind,n) ->
     make (Ext_list.append_one block (S.define_variable ~kind  n exp))

jscomp/core/lam_compile.ml

@@ -46,12 +46,16 @@ type return_label = {
   mutable triggered : bool
 }
 
-type return_type = 
-  | ReturnFalse 
-  | ReturnTrue of return_label option 
+type maybe_tail = 
+  | Tail_in_try
+  | Tail_with_name of return_label option
+
+type tail_type = 
+  | Not_tail 
+  | Maybe_tail_is_return of maybe_tail
   (* Note [return] does indicate it is a tail position in most cases
      however, in an exception handler, return may not be in tail position
-     to fix #1701 we play a trick that (ReturnTrue None) 
+     to fix #1701 we play a trick that (Maybe_tail_is_return None) 
      would never trigger tailcall, however, it preserves [return] 
      semantics
   *)
@@ -61,18 +65,18 @@ type return_type =
 type let_kind = Lam_compat.let_kind
 
 type continuation = 
-  | EffectCall of return_type
-  | NeedValue of return_type
+  | EffectCall of tail_type
+  | NeedValue of tail_type
   | Declare of let_kind * J.ident (* bound value *)
   | Assign of J.ident (* when use [Assign], var is not needed, since it's already declared  *)
 
 type jmp_table =   value  HandlerMap.t
 
 let continuation_is_return ( x : continuation) =  
   match x with 
-  | EffectCall (ReturnTrue _) | NeedValue (ReturnTrue _) 
+  | EffectCall (Maybe_tail_is_return _) | NeedValue (Maybe_tail_is_return _) 
     -> true 
-  | EffectCall ReturnFalse | NeedValue ReturnFalse 
+  | EffectCall Not_tail | NeedValue Not_tail 
   | Declare _ | Assign _
     -> false
 
@@ -109,5 +113,5 @@ let add_jmps
   map, List.rev handlers
 
 
-let find_exn i cxt = 
+let find_exn cxt i = 
   Int_map.find_exn cxt.jmp_table i 

jscomp/core/lam_compile_context.ml

@@ -57,17 +57,22 @@ type value = {
 
 type let_kind = Lam_compat.let_kind
 
-type return_type = 
-  | ReturnFalse 
-  | ReturnTrue of return_label option (* anonoymous function does not have identifier *)
+type maybe_tail = 
+    | Tail_in_try    
+    | Tail_with_name of return_label option
+
+type tail_type = 
+  | Not_tail 
+  | Maybe_tail_is_return of maybe_tail
+  (* anonoymous function does not have identifier *)
 
 (* delegate to the callee to generate expression 
       Invariant: [output] should return a trailing expression
   *)
 
 type continuation = 
-  | EffectCall of return_type
-  | NeedValue of return_type
+  | EffectCall of tail_type
+  | NeedValue of tail_type
   | Declare of let_kind * J.ident (* bound value *)
   | Assign of J.ident 
   (** when use [Assign], var is not needed, since it's already declared 
@@ -81,6 +86,8 @@ type jmp_table
 val continuation_is_return:
   continuation -> 
   bool 
+
+
 type t = {
   continuation : continuation ;
   jmp_table : jmp_table;
@@ -96,9 +103,13 @@ type handler = {
 } 
 
 val add_jmps :
-    jmp_table -> 
-    Ident.t ->
-    handler list ->
-    jmp_table * (jbl_label * Lam.t) list
+  jmp_table -> 
+  Ident.t ->
+  handler list ->
+  jmp_table * (jbl_label * Lam.t) list
+
 
-val find_exn : jbl_label -> t -> value
+val find_exn : 
+  t -> 
+  jbl_label -> 
+  value

jscomp/core/lam_compile_context.mli

@@ -77,13 +77,13 @@ let compile_group (meta : Lam_stats.t)
 
   | Recursive id_lams   -> 
     Lam_compile.compile_recursive_lets 
-      { continuation = EffectCall ReturnFalse; 
+      { continuation = EffectCall Not_tail; 
         jmp_table = Lam_compile_context.empty_handler_map;
         meta
       } 
       id_lams
   | Nop lam -> (* TODO: Side effect callls, log and see statistics *)
-    Lam_compile.compile_lambda {continuation = EffectCall ReturnFalse;
+    Lam_compile.compile_lambda {continuation = EffectCall Not_tail;
                                 jmp_table = Lam_compile_context.empty_handler_map;
                                 meta
                                } lam

jscomp/core/lam_compile_main.ml

@@ -36,9 +36,9 @@ module E = Js_exp_make
 *)
 let ensure_value_unit (st : Lam_compile_context.continuation) e : E.t = 
   match st with 
-  | EffectCall (ReturnTrue _ ) | NeedValue (ReturnTrue _)
+  | EffectCall (Maybe_tail_is_return _ ) | NeedValue (Maybe_tail_is_return _)
   | Assign _ | Declare _ | NeedValue _  -> E.seq e E.unit
-  | EffectCall ReturnFalse -> e 
+  | EffectCall Not_tail -> e 
 (* NeedValue should return a meaningful expression*)
 
 let translate  loc