Rebase interpreter (#214)

* wip eval

* first full interpreter attempt

* remove unshared token

* fix wrapping behaviour of cmpxchg

* fix thread text parsing

* add threading tests

* restore seeding flags

* fix instance visibility in init code

* fix binary test

---------

Co-authored-by: Oscar Spencer <oscar@grain-lang.org>

Author: conrad-watt

interpreter/binary/decode.ml

@@ -98,7 +98,6 @@ let rec sN n s =
   then (if b land 0x40 = 0 then x else Int64.(logor x (logxor (-1L) 0x7fL)))
   else Int64.(logor x (shift_left (sN (n - 7) s) 7))
 
-let u1 s = Int64.to_int (uN 1 s)
 let u32 s = Int64.to_int32 (uN 32 s)
 let s7 s = Int64.to_int (sN 7 s)
 let s32 s = Int64.to_int32 (sN 32 s)
@@ -114,7 +113,6 @@ let len32 s =
   if I32.le_u n (Int32.of_int (len s - pos)) then Int32.to_int n else
     error s pos "length out of bounds"
 
-let bool s = (u1 s = 1)
 let string s = let n = len32 s in get_string n s
 let rec list f n s = if n = 0 then [] else let x = f s in x :: list f (n - 1) s
 let opt f b s = if b then Some (f s) else None
@@ -180,20 +178,24 @@ let func_type s =
     FuncType (ts1, ts2)
   | _ -> error s (pos s - 1) "malformed function type"
 
-let limits uN s =
-  let has_max = bool s in
-  let min = uN s in
-  let max = opt uN has_max s in
-  {min; max}
+let limits vu s =
+  let flags = byte s in
+  require (flags land 0xfc = 0) s (pos s - 1) "malformed limits flags";
+  let has_max = (flags land 1 = 1) in
+  let shared = (flags land 2 = 2) in
+  let min = vu s in
+  let max = opt vu has_max s in
+  {min; max}, shared
 
 let table_type s =
   let t = ref_type s in
-  let lim = limits u32 s in
+  let lim, shared = limits u32 s in
+  require (not shared) s (pos s - 1) "tables cannot be shared (yet)";
   TableType (lim, t)
 
 let memory_type s =
-  let lim = limits u32 s in
-  MemoryType lim
+  let lim, shared = limits u32 s in
+  MemoryType (lim, if shared then Shared else Unshared)
 
 let mutability s =
   match byte s with

interpreter/binary/encode.ml

@@ -73,7 +73,6 @@ struct
       Code.error Source.no_region "length out of bounds";
     u32 (Int32.of_int i)
 
-  let bool b = u1 (if b then 1 else 0)
   let string bs = len (String.length bs); put_string s bs
   let name n = string (Utf8.encode n)
   let list f xs = List.iter f xs
@@ -118,14 +117,16 @@ struct
       s7 (-0x20); vec value_type ts1; vec value_type ts2
 
 
-  let limits vu {min; max} =
-    bool (max <> None); vu min; opt vu max
+  let limits vu {min; max} shared =
+    let int_of_bool b = if b then 1 else 0 in
+    let flags = int_of_bool shared lsl 1 lor int_of_bool (max <> None) in
+    byte flags; vu min; opt vu max
 
   let table_type = function
-    | TableType (lim, t) -> ref_type t; limits u32 lim
+    | TableType (lim, t) -> ref_type t; limits u32 lim false
 
   let memory_type = function
-    | MemoryType lim -> limits u32 lim
+    | MemoryType (lim, shared) -> limits u32 lim (shared = Shared)
 
   let mutability = function
     | Immutable -> byte 0