[sledge] Change Typ.is_sized to remove hack for opaque types

Summary:
It happens so seldomly that it is not worth it to optimistically
assume that linking will make opaque types sized. In particular, it is
incongruent for `Typ.is_sized` to hold and then `Typ.size_of` to
raise.

Reviewed By: jvillard

Differential Revision: D24772956

fbshipit-source-id: 96a72a5cf

sledge/cli/frontend.ml

@@ -489,7 +489,10 @@ and xlate_value ?(inline = false) stk :
         let name = find_name (Llvm.operand llv 1) in
         ([], Exp.label ~parent ~name)
     | UndefValue ->
-        let typ = xlate_type x (Llvm.type_of llv) in
+        let llt = Llvm.type_of llv in
+        let typ = xlate_type x llt in
+        if not (Typ.is_sized typ) then
+          todo "types with undetermined size: %a" pp_lltype llt () ;
         let name = Printf.sprintf "undef_%i" !undef_count in
         let loc = Loc.none in
         let reg = Reg.program typ name in

sledge/src/llair/typ.ml

@@ -57,9 +57,8 @@ let pp_defn fs = function
 (** Invariants *)
 
 let is_sized = function
-  | Function _ -> false
+  | Function _ | Opaque _ -> false
   | Integer _ | Float _ | Pointer _ | Array _ | Tuple _ | Struct _ -> true
-  | Opaque _ -> (* optimistically assume linking will make it sized *) true
 
 let invariant t =
   let@ () = Invariant.invariant [%here] t [%sexp_of: t] in