First stab at implementing named handlers

Author: dhil

interpreter/binary/decode.ml

@@ -194,6 +194,8 @@ let heap_type s =
       | -0x16 -> ArrayHT
       | -0x17 -> ExnHT
       | -0x18 -> ContHT
+      | -0x19 -> HandlerHT
+      | -0x1a -> NoHandlerHT
       | _ -> error s pos "malformed heap type"
     )
   ] s
@@ -215,6 +217,8 @@ let ref_type s =
   | -0x16 -> (Null, ArrayHT)
   | -0x17 -> (Null, ExnHT)
   | -0x18 -> (Null, ContHT)
+  | -0x19 -> (Null, HandlerHT)
+  | -0x1a -> (Null, NoHandlerHT)
   | -0x1c -> (NoNull, heap_type s)
   | -0x1d -> (Null, heap_type s)
   | _ -> error s pos "malformed reference type"
@@ -260,12 +264,16 @@ let func_type s =
 let cont_type s =
   ContT (heap_type s)
 
+let handler_type s =
+  HandlerT (result_type s)
+
 let str_type s =
   match s7 s with
   | -0x20 -> DefFuncT (func_type s)
   | -0x21 -> DefStructT (struct_type s)
   | -0x22 -> DefArrayT (array_type s)
   | -0x23 -> DefContT (cont_type s) (* TODO(dhil): See comment in encode.ml *)
+  | -0x24 -> DefHandlerT (handler_type s)
   | _ -> error s (pos s - 1) "malformed definition type"
 
 let sub_type s =
@@ -654,6 +662,14 @@ let rec instr s =
     let es' = instr_block s in
     end_ s;
     barrier bt es'
+  | 0xe7 ->
+    let x = at var s in
+    let y = at var s in
+    suspend_to x y
+  | 0xe8 ->
+    let x = at var s in
+    let xls = vec on_clause s in
+    resume_with x xls
 
   | 0xfb as b ->
     (match u32 s with

interpreter/binary/encode.ml

@@ -132,6 +132,8 @@ struct
     | NoExternHT -> s7 (-0x0e)
     | ContHT -> s7 (-0x18)
     | NoContHT -> s7 (-0x0b)
+    | HandlerHT -> s7 (-0x19)
+    | NoHandlerHT -> s7 (-0x1a)
     | VarHT x -> var_type s33 x
     | DefHT _ | BotHT -> assert false
 
@@ -187,6 +189,9 @@ struct
   let cont_type = function
     | ContT ht -> heap_type ht
 
+  let handler_type = function
+    | HandlerT ts -> vec val_type ts
+
   let str_type = function
     | DefStructT st -> s7 (-0x21); struct_type st
     | DefArrayT at -> s7 (-0x22); array_type at
@@ -195,6 +200,7 @@ struct
     (* TODO(dhil): This might need to change again in the future as a
        different proposal might claim this opcode! GC proposal claimed
        the previous opcode we were using. *)
+    | DefHandlerT ht -> s7 (-0x24); handler_type ht
 
   let sub_type = function
     | SubT (Final, [], st) -> str_type st
@@ -300,8 +306,10 @@ struct
     | ContNew x -> op 0xe0; var x
     | ContBind (x, y) -> op 0xe1; var x; var y
     | Suspend x -> op 0xe2; var x
+    | SuspendTo (x, y) -> op 0xe7; var x; var y
     | Resume (x, xls) -> op 0xe3; var x; resumetable xls
     | ResumeThrow (x, y, xls) -> op 0xe4; var x; var y; resumetable xls
+    | ResumeWith (x, xls) -> op 0xe8; var x; resumetable xls
     | Switch (x, y) -> op 0xe5; var x; var y
     | Barrier (bt, es) -> op 0xe6; block_type bt; list instr es; end_ ()
 

interpreter/exec/eval.ml

@@ -58,6 +58,7 @@ type frame =
 }
 
 type code = value stack * admin_instr list
+and handler_name = exn
 
 and admin_instr = admin_instr' phrase
 and admin_instr' =
@@ -72,25 +73,28 @@ and admin_instr' =
   | Label of int * instr list * code
   | Frame of int * frame * code
   | Handler of int * catch list * code
-  | Handle of handle_table option * code
-  | Suspending of tag_inst * value stack * ref_ option * ctxt
+  | Handle of handler_name option * handle_table option * code
+  | Suspending of tag_inst * value stack * ref_ option * ref_ option * ctxt
 
 and ctxt = code -> code
 and handle_table = (tag_inst * idx) list * tag_inst list
 
 type cont = int32 * ctxt  (* TODO: represent type properly *)
 type ref_ += ContRef of cont option ref
+type ref_ += HandlerRef of handler_name option ref
 
 let () =
   let type_of_ref' = !Value.type_of_ref' in
   Value.type_of_ref' := function
     | ContRef _ -> ContHT
+    | HandlerRef _ -> HandlerHT
     | r -> type_of_ref' r
 
 let () =
   let string_of_ref' = !Value.string_of_ref' in
   Value.string_of_ref' := function
     | ContRef _ -> "cont"
+    | HandlerRef _ -> "handler"
     | r -> string_of_ref' r
 
 let plain e = Plain e.it @@ e.at
@@ -377,7 +381,18 @@ let rec step (c : config) : config =
         let tagt = tag c.frame.inst x in
         let FuncT (ts, _) = func_type_of_tag_type c.frame.inst (Tag.type_of tagt) in
         let args, vs' = i32_split (Lib.List32.length ts) vs e.at in
-        vs', [Suspending (tagt, args, None, fun code -> code) @@ e.at]
+        vs', [Suspending (tagt, args, None, None, fun code -> code) @@ e.at]
+
+      | SuspendTo (x, y), vs ->
+        let tagt = tag c.frame.inst y in
+        let FuncT (ts, _) = func_type_of_tag_type c.frame.inst (Tag.type_of tagt) in
+        let args, vs' = i32_split (Lib.List32.length ts) vs e.at in
+        let args, href =
+          match Lib.List.lead args, Lib.List.last args with
+          | args, Ref r -> args, r
+          | _ -> Crash.error e.at "type mismatch at suspend to"
+        in
+        vs', [Suspending (tagt, args, None, Some href, fun code -> code) @@ e.at]
 
       | Resume (x, xls), Ref (NullRef _) :: vs ->
         vs, [Trapping "null continuation reference" @@ e.at]
@@ -389,7 +404,7 @@ let rec step (c : config) : config =
         let hs = handle_table c xls in
         let args, vs' = i32_split n vs e.at in
         cont := None;
-        vs', [Handle (Some hs, ctxt (args, [])) @@ e.at]
+        vs', [Handle (None, Some hs, ctxt (args, [])) @@ e.at]
 
       | ResumeThrow (x, y, xls), Ref (NullRef _) :: vs ->
         vs, [Trapping "null continuation reference" @@ e.at]
@@ -403,7 +418,24 @@ let rec step (c : config) : config =
         let hs = handle_table c xls in
         let args, vs' = i32_split (Lib.List32.length ts) vs e.at in
         cont := None;
-        vs', [Handle (Some hs, ctxt (args, [Plain (Throw x) @@ e.at])) @@ e.at]
+        vs', [Handle (None, Some hs, ctxt (args, [Plain (Throw x) @@ e.at])) @@ e.at]
+
+      | ResumeWith (x, xls), Ref (NullRef _) :: vs ->
+        vs, [Trapping "null continuation reference" @@ e.at]
+
+      | ResumeWith (x, xls), Ref (ContRef {contents = None}) :: vs ->
+        vs, [Trapping "continuation already consumed" @@ e.at]
+
+      | ResumeWith (x, xls), Ref (ContRef ({contents = Some (n, ctxt)} as cont)) :: vs ->
+        let hs = handle_table c xls in
+        Printf.printf "arity: %s\n%!" (I32.to_string_u n); 
+        let args, vs' = i32_split (I32.sub n 1l) vs e.at in
+        let exception Name in
+        let name =
+          Ref (HandlerRef (ref (Some Name)))
+        in
+        cont := None;
+        vs', [Handle (Some Name, Some hs, ctxt (args @ [name], [])) @@ e.at]
 
       | Switch (x, y), Ref (NullRef _) :: vs ->
          vs, [Trapping "null continuation reference" @@ e.at]
@@ -414,13 +446,13 @@ let rec step (c : config) : config =
       | Switch (x, y), Ref (ContRef {contents = Some (n, ctxt)} as cont) :: vs ->
          let tagt = tag c.frame.inst y in
          let args, vs' = i32_split (Int32.sub n 1l) vs e.at in
-         vs', [Suspending (tagt, args, Some cont, fun code -> code) @@ e.at]
+         vs', [Suspending (tagt, args, Some cont, None, fun code -> code) @@ e.at]
 
       | Barrier (bt, es'), vs ->
         let InstrT (ts1, _, _xs) = block_type c.frame.inst bt e.at in
         let args, vs' = i32_split (Lib.List32.length ts1) vs e.at in
         vs', [
-          Handle (None,
+          Handle (None, None,
             (args, [Plain (Block (bt, es')) @@ e.at])
           ) @@ e.at
         ]
@@ -1156,9 +1188,9 @@ let rec step (c : config) : config =
     | Label (n, es0, (vs', [])), vs ->
       vs' @ vs, []
 
-    | Label (n, es0, (vs', {it = Suspending (tagt, vs1, contref, ctxt); at} :: es')), vs ->
+    | Label (n, es0, (vs', {it = Suspending (tagt, vs1, contref, href, ctxt); at} :: es')), vs ->
       let ctxt' code = [], [Label (n, es0, compose (ctxt code) (vs', es')) @@ e.at] in
-      vs, [Suspending (tagt, vs1, contref, ctxt') @@ at]
+      vs, [Suspending (tagt, vs1, contref, href, ctxt') @@ at]
 
     | Label (n, es0, (vs', {it = ReturningInvoke (vs0, f); at} :: es')), vs ->
       vs, [ReturningInvoke (vs0, f) @@ at]
@@ -1185,9 +1217,9 @@ let rec step (c : config) : config =
     | Frame (n, frame', (vs', {it = Throwing (a, vs0); at} :: es')), vs ->
       vs, [Throwing (a, vs0) @@ at]
 
-    | Frame (n, frame', (vs', {it = Suspending (tagt, vs1, contref, ctxt); at} :: es')), vs ->
+    | Frame (n, frame', (vs', {it = Suspending (tagt, vs1, contref, href, ctxt); at} :: es')), vs ->
       let ctxt' code = [], [Frame (n, frame', compose (ctxt code) (vs', es')) @@ e.at] in
-      vs, [Suspending (tagt, vs1, contref, ctxt') @@ at]
+      vs, [Suspending (tagt, vs1, contref, href, ctxt') @@ at]
 
     | Frame (n, frame', (vs', {it = Returning vs0; at} :: es')), vs ->
       take n vs0 e.at @ vs, []
@@ -1227,9 +1259,9 @@ let rec step (c : config) : config =
     | Handler (n, [], (vs', {it = Throwing (a, vs0); at} :: es')), vs ->
       vs, [Throwing (a, vs0) @@ at]
 
-    | Handler (n, cs, (vs', {it = Suspending (tagt, vs1, contref, ctxt); at} :: es')), vs ->
+    | Handler (n, cs, (vs', {it = Suspending (tagt, vs1, contref, href, ctxt); at} :: es')), vs ->
       let ctxt' code = [], [Handler (n, cs, compose (ctxt code) (vs', es')) @@ e.at] in
-      vs, [Suspending (tagt, vs1, contref, ctxt') @@ at]
+      vs, [Suspending (tagt, vs1, contref, href, ctxt') @@ at]
 
     | Handler (n, cs, (vs', e' :: es')), vs when is_jumping e' ->
       vs, [e']
@@ -1261,40 +1293,48 @@ let rec step (c : config) : config =
         with Crash (_, msg) -> Crash.error e.at msg)
       )
 
-    | Handle (hso, (vs', [])), vs ->
+    | Handle (name, hso, (vs', [])), vs ->
       vs' @ vs, []
 
-    | Handle (None, (vs', {it = Suspending _; at} :: es')), vs ->
+    | Handle (name, None, (vs', {it = Suspending _; at} :: es')), vs ->
       vs, [Trapping "barrier hit by suspension" @@ at]
 
-    | Handle (Some (hs, _), (vs', {it = Suspending (tagt, vs1, None, ctxt); at} :: es')), vs
+    | Handle (None, Some (hs, _), (vs', {it = Suspending (tagt, vs1, None, None, ctxt); at} :: es')), vs
       when List.mem_assq tagt hs ->
       let FuncT (_, ts) = func_type_of_tag_type c.frame.inst (Tag.type_of tagt) in
       let ctxt' code = compose (ctxt code) (vs', es') in
       [Ref (ContRef (ref (Some (Lib.List32.length ts, ctxt'))))] @ vs1 @ vs,
       [Plain (Br (List.assq tagt hs)) @@ e.at]
 
-    | Handle (Some (_, hs) as hso, (vs', {it = Suspending (tagt, vs1, Some (ContRef ({contents = Some (_, ctxt)} as cont)), ctxt'); at} :: es')), vs
+    | Handle (Some h, Some (hs, _), (vs', {it = Suspending (tagt, vs1, None, Some (HandlerRef ({contents = Some h'} as href)), ctxt); at} :: es')), vs
+      when h == h' && List.mem_assq tagt hs ->
+      let FuncT (_, ts) = func_type_of_tag_type c.frame.inst (Tag.type_of tagt) in
+      let ctxt' code = compose (ctxt code) (vs', es') in
+      href := None;
+      [Ref (ContRef (ref (Some (Int32.add (Lib.List32.length ts) 1l, ctxt'))))] @ vs1 @ vs,
+      [Plain (Br (List.assq tagt hs)) @@ e.at]
+
+    | Handle (None, (Some (_, hs) as hso), (vs', {it = Suspending (tagt, vs1, Some (ContRef ({contents = Some (_, ctxt)} as cont)), None, ctxt'); at} :: es')), vs
        when List.memq tagt hs ->
        let FuncT (_, ts) = func_type_of_tag_type c.frame.inst (Tag.type_of tagt) in
        let ctxt'' code = compose (ctxt' code) (vs', es') in
        let cont' = Ref (ContRef (ref (Some (Int32.add (Lib.List32.length ts) 1l, ctxt'')))) in
        let args = vs1 @ [cont'] in
        cont := None;
-       vs' @ vs, [Handle (hso, ctxt (args, [])) @@ e.at]
+       vs' @ vs, [Handle (None, hso, ctxt (args, [])) @@ e.at]
 
-    | Handle (hso, (vs', {it = Suspending (tagt, vs1, contref, ctxt); at} :: es')), vs ->
-      let ctxt' code = [], [Handle (hso, compose (ctxt code) (vs', es')) @@ e.at] in
-      vs, [Suspending (tagt, vs1, contref, ctxt') @@ at]
+    | Handle (name, hso, (vs', {it = Suspending (tagt, vs1, contref, href, ctxt); at} :: es')), vs ->
+      let ctxt' code = [], [Handle (name, hso, compose (ctxt code) (vs', es')) @@ e.at] in
+      vs, [Suspending (tagt, vs1, contref, href, ctxt') @@ at]
 
-    | Handle (hso, (vs', e' :: es')), vs when is_jumping e' ->
+    | Handle (name, hso, (vs', e' :: es')), vs when is_jumping e' ->
       vs, [e']
 
-    | Handle (hso, code'), vs ->
+    | Handle (name, hso, code'), vs ->
       let c' = step {c with code = code'} in
-      vs, [Handle (hso, c'.code) @@ e.at]
+      vs, [Handle (name, hso, c'.code) @@ e.at]
 
-    | Suspending (_, _, _, _), _ -> assert false
+    | Suspending (_, _, _, _, _), _ -> assert false
 
   in {c with code = vs', es' @ List.tl es}
 

interpreter/syntax/ast.ml

@@ -167,8 +167,10 @@ and instr' =
   | ContNew of idx                    (* create continuation *)
   | ContBind of idx * idx             (* bind continuation arguments *)
   | Suspend of idx                    (* suspend continuation *)
+  | SuspendTo of idx * idx            (* named suspend continuation *)
   | Resume of idx * (idx * hdl) list  (* resume continuation *)
   | ResumeThrow of idx * idx * (idx * hdl) list (* abort continuation *)
+  | ResumeWith of idx * (idx * hdl) list (* named resume continuation *)
   | Switch of idx * idx               (* direct switch continuation *)
   | Barrier of block_type * instr list  (* guard against suspension *)
   | Throw of idx                      (* throw exception *)

interpreter/syntax/free.ml

@@ -82,6 +82,7 @@ let heap_type = function
   | ExnHT | NoExnHT -> empty
   | ExternHT | NoExternHT -> empty
   | ContHT | NoContHT -> empty
+  | HandlerHT | NoHandlerHT -> empty
   | VarHT x -> var_type x
   | DefHT _ct -> empty  (* assume closed *)
   | BotHT -> empty
@@ -109,12 +110,14 @@ let field_type (FieldT (_mut, st)) = storage_type st
 let struct_type (StructT fts) = list field_type fts
 let array_type (ArrayT ft) = field_type ft
 let func_type (FuncT (ts1, ts2)) = list val_type ts1 ++ list val_type ts2
+let handler_type (HandlerT ts) = list val_type ts
 
 let str_type = function
   | DefStructT st -> struct_type st
   | DefArrayT at -> array_type at
   | DefFuncT ft -> func_type ft
   | DefContT ct -> cont_type ct
+  | DefHandlerT ht -> handler_type ht
 
 let sub_type = function
   | SubT (_fin, hts, st) -> list heap_type hts ++ str_type st
@@ -182,7 +185,9 @@ let rec instr (e : instr) =
   | ContBind (x, y) -> types (idx x) ++ types (idx y)
   | ResumeThrow (x, y, xys) -> types (idx x) ++ tags (idx y) ++ list (fun (x, y) -> tags (idx x) ++ hdl y) xys
   | Resume (x, xys) -> types (idx x) ++ list (fun (x, y) -> tags (idx x) ++ hdl y) xys
+  | ResumeWith (x, xys) -> types (idx x) ++ list (fun (x, y) -> tags (idx x) ++ hdl y) xys
   | Suspend x -> tags (idx x)
+  | SuspendTo (x, y) -> types (idx x) ++ tags (idx y)
   | Switch (x, z) -> types (idx x) ++ tags (idx z)
   | Throw x -> tags (idx x)
   | ThrowRef -> empty

interpreter/syntax/operators.ml

@@ -48,8 +48,10 @@ let return_call_indirect x y = ReturnCallIndirect (x, y)
 let cont_new x = ContNew x
 let cont_bind x y = ContBind (x, y)
 let suspend x = Suspend x
+let suspend_to x y = SuspendTo (x, y)
 let resume x xys = Resume (x, xys)
 let resume_throw x y xys = ResumeThrow (x, y, xys)
+let resume_with x xys = ResumeWith (x, xys)
 let switch x y = Switch (x, y)
 let barrier bt es = Barrier (bt, es)
 let throw x = Throw x