[interpreter] Factor data and element segments into abstract types (WebAssembly#1492)

Author: rossberg

interpreter/exec/eval.ml

@@ -142,15 +142,15 @@ let mem_oob frame x i n =
 
 let data_oob frame x i n =
   I64.gt_u (I64.add (I64_convert.extend_i32_u i) (I64_convert.extend_i32_u n))
-    (I64.of_int_u (String.length !(data frame.inst x)))
+    (Data.size (data frame.inst x))
 
 let table_oob frame x i n =
   I64.gt_u (I64.add (I64_convert.extend_i32_u i) (I64_convert.extend_i32_u n))
     (I64_convert.extend_i32_u (Table.size (table frame.inst x)))
 
 let elem_oob frame x i n =
   I64.gt_u (I64.add (I64_convert.extend_i32_u i) (I64_convert.extend_i32_u n))
-    (I64.of_int_u (List.length !(elem frame.inst x)))
+    (I64_convert.extend_i32_u (Elem.size (elem frame.inst x)))
 
 let rec step (c : config) : config =
   let vs, es = c.code in
@@ -349,10 +349,10 @@ let rec step (c : config) : config =
         else if n = 0l then
           vs', []
         else
-          let seg = !(elem c.frame.inst y) in
+          let seg = elem c.frame.inst y in
           vs', List.map (Lib.Fun.flip (@@) e.at) [
             Plain (Const (I32 d @@ e.at));
-            Refer (List.nth seg (Int32.to_int s));
+            Refer (Elem.load seg s);
             Plain (TableSet x);
             Plain (Const (I32 (I32.add d 1l) @@ e.at));
             Plain (Const (I32 (I32.add s 1l) @@ e.at));
@@ -362,7 +362,7 @@ let rec step (c : config) : config =
 
       | ElemDrop x, vs ->
         let seg = elem c.frame.inst x in
-        seg := [];
+        Elem.drop seg;
         vs, []
 
       | Load {offset; ty; pack; _}, Num (I32 i) :: vs' ->
@@ -513,11 +513,12 @@ let rec step (c : config) : config =
         else if n = 0l then
           vs', []
         else
-          let seg = !(data c.frame.inst x) in
-          let b = Int32.of_int (Char.code seg.[Int32.to_int s]) in
+          let seg = data c.frame.inst x in
+          let a = I64_convert.extend_i32_u s in
+          let b = Data.load seg a in
           vs', List.map (Lib.Fun.flip (@@) e.at) [
             Plain (Const (I32 d @@ e.at));
-            Plain (Const (I32 b @@ e.at));
+            Plain (Const (I32 (I32.of_int_u (Char.code b)) @@ e.at));
             Plain (Store
               {ty = Types.I32T; align = 0; offset = 0l; pack = Some Pack8});
             Plain (Const (I32 (I32.add d 1l) @@ e.at));
@@ -528,7 +529,7 @@ let rec step (c : config) : config =
 
       | DataDrop x, vs ->
         let seg = data c.frame.inst x in
-        seg := "";
+        Data.drop seg;
         vs, []
 
       | RefNull t, vs' ->
@@ -788,11 +789,11 @@ let create_export (inst : module_inst) (ex : export) : export_inst =
 
 let create_elem (inst : module_inst) (seg : elem_segment) : elem_inst =
   let {etype; einit; _} = seg.it in
-  ref (List.map (fun c -> as_ref (eval_const inst c)) einit)
+  Elem.alloc (List.map (fun c -> as_ref (eval_const inst c)) einit)
 
 let create_data (inst : module_inst) (seg : data_segment) : data_inst =
   let {dinit; _} = seg.it in
-  ref dinit
+  Data.alloc dinit
 
 
 let add_import (m : module_) (ext : extern) (im : import) (inst : module_inst)

interpreter/exec/ixx.ml

@@ -30,8 +30,8 @@ sig
 
   val of_int : int -> t
   val to_int : t -> int
-  val of_int64: int64 -> t
-  val to_int64: t -> int64
+  val of_int64 : int64 -> t
+  val to_int64 : t -> int64
   val to_string : t -> string
   val to_hex_string : t -> string
 

interpreter/runtime/data.ml

@@ -0,0 +1,7 @@
+type data = string ref
+type t = data
+
+let alloc bs = ref bs
+let size seg = I64.of_int_u (String.length !seg)
+let load seg i = (!seg).[Int64.to_int i]
+let drop seg = seg := ""

interpreter/runtime/data.mli

@@ -0,0 +1,7 @@
+type data
+type t = data
+
+val alloc : string -> data
+val size : data -> Memory.address
+val load : data -> Memory.address -> char
+val drop : data -> unit

interpreter/runtime/elem.ml

@@ -0,0 +1,7 @@
+type elem = Values.ref_ list ref
+type t = elem
+
+let alloc rs = ref rs
+let size seg = Lib.List32.length !seg
+let load seg i = Lib.List32.nth !seg i
+let drop seg = seg := []

interpreter/runtime/elem.mli

@@ -0,0 +1,9 @@
+open Values
+
+type elem
+type t = elem
+
+val alloc : ref_ list -> elem
+val size : elem -> Table.size
+val load : elem -> Table.index -> ref_
+val drop : elem -> unit

interpreter/runtime/instance.ml

@@ -7,19 +7,19 @@ type module_inst =
   tables : table_inst list;
   memories : memory_inst list;
   globals : global_inst list;
-  exports : export_inst list;
   elems : elem_inst list;
   datas : data_inst list;
+  exports : export_inst list;
 }
 
 and type_inst = var
 and func_inst = module_inst Lib.Promise.t Func.t
 and table_inst = Table.t
 and memory_inst = Memory.t
 and global_inst = Global.t
+and elem_inst = Elem.t
+and data_inst = Data.t
 and export_inst = Ast.name * extern
-and elem_inst = Value.ref_ list ref
-and data_inst = string ref
 
 and extern =
   | ExternFunc of func_inst
@@ -56,7 +56,7 @@ let () =
 
 let empty_module_inst =
   { types = []; funcs = []; tables = []; memories = []; globals = [];
-    exports = []; elems = []; datas = [] }
+    elems = []; datas = []; exports = [] }
 
 let extern_type_of c = function
   | ExternFunc func -> ExternFuncT (Func.type_of func)