diff --git a/sledge/src/llair/exp.ml b/sledge/src/llair/exp.ml
index c88539a96..ce972bda8 100644
--- a/sledge/src/llair/exp.ml
+++ b/sledge/src/llair/exp.ml
@@ -212,6 +212,7 @@ let rec invariant exp =
     match typ with Float _ -> assert true | _ -> assert false )
   | Label _ -> assert true
   | Ap1 (Convert {dst}, src, arg) ->
+      assert (not (Typ.equal dst src)) ;
       assert (Typ.convertible dst src) ;
       assert (Typ.castable src (typ_of arg))
   | Ap1 (Select idx, typ, rcd) -> (
@@ -223,9 +224,9 @@ let rec invariant exp =
   | Ap2 (Splat, typ, byt, siz) -> (
       assert (Typ.convertible Typ.byt (typ_of byt)) ;
       assert (Typ.convertible Typ.siz (typ_of siz)) ;
-      match (Typ.size_of typ, siz.desc) with
-      | Some n, Integer {data} -> assert (Z.equal (Z.of_int n) data)
-      | None, Integer {data} -> assert (not (Z.equal Z.zero data))
+      assert (Typ.is_sized typ) ;
+      match siz.desc with
+      | Integer {data} -> assert (Z.equal (Z.of_int (Typ.size_of typ)) data)
       | _ -> () )
   | Ap2 (Update idx, typ, rcd, elt) -> (
       assert (Typ.castable typ (typ_of rcd)) ;
@@ -295,6 +296,8 @@ and typ_of exp =
       typ
   [@@warning "-9"]
 
+let typ = typ_of
+
 type exp = t
 
 let pp_exp = pp
@@ -422,10 +425,8 @@ let binary op mk ?typ x y =
 let ubinary op mk ?typ x y =
   let typ = match typ with Some typ -> typ | None -> typ_of x in
   let umk x y =
-    let bits = Option.value_exn (Typ.prim_bit_size_of typ) in
-    mk
-      (Term.extract ~unsigned:true ~bits x)
-      (Term.extract ~unsigned:true ~bits y)
+    let extract = Term.extract ~unsigned:true ~bits:(Typ.bit_size_of typ) in
+    mk (extract x) (extract y)
   in
   binary op umk ~typ x y
 
@@ -520,6 +521,8 @@ let struct_rec key =
          forcing the recursive thunks also updates this value. *)
       {desc= ApN (Struct_rec, typ, elts); term= rec_app ~id Vector.empty}
 
+let size_of exp = integer Typ.siz (Z.of_int (Typ.size_of (typ exp)))
+
 (** Traverse *)
 
 let fold_exps e ~init ~f =
diff --git a/sledge/src/llair/exp.mli b/sledge/src/llair/exp.mli
index b89d90425..30c5a7eab 100644
--- a/sledge/src/llair/exp.mli
+++ b/sledge/src/llair/exp.mli
@@ -196,6 +196,8 @@ val struct_rec :
     one point on each cycle. Failure to obey these requirements will lead to
     stack overflow. *)
 
+val size_of : t -> t
+
 (** Traverse *)
 
 val fold_regs : t -> init:'a -> f:('a -> Reg.t -> 'a) -> 'a
diff --git a/sledge/src/llair/frontend.ml b/sledge/src/llair/frontend.ml
index f91757827..c0850c2f6 100644
--- a/sledge/src/llair/frontend.ml
+++ b/sledge/src/llair/frontend.ml
@@ -190,69 +190,79 @@ type x =
 let ptr_siz : x -> int =
  fun x -> Llvm_target.DataLayout.pointer_size x.lldatalayout
 
-let size_of : x -> Llvm.lltype -> int =
- fun x llt ->
-  if Llvm.type_is_sized llt then
-    match
-      Int64.to_int (Llvm_target.DataLayout.abi_size llt x.lldatalayout)
-    with
-    | Some n -> n
-    | None -> fail "size_of: %a" pp_lltype llt ()
-  else todo "types with undetermined size: %a" pp_lltype llt ()
+let size_of, bit_size_of =
+  let size_to_int size_of x llt =
+    if Llvm.type_is_sized llt then
+      match Int64.to_int (size_of llt x.lldatalayout) with
+      | Some n -> n
+      | None -> fail "type size too large: %a" pp_lltype llt ()
+    else fail "types with undetermined size: %a" pp_lltype llt ()
+  in
+  ( size_to_int Llvm_target.DataLayout.abi_size
+  , size_to_int Llvm_target.DataLayout.size_in_bits )
 
 let memo_type : (Llvm.lltype, Typ.t) Hashtbl.t = Hashtbl.Poly.create ()
 
 let rec xlate_type : x -> Llvm.lltype -> Typ.t =
  fun x llt ->
   let xlate_type_ llt =
-    match Llvm.classify_type llt with
-    | Half -> Typ.float ~bits:16 ~siz:(size_of x llt) ~enc:`IEEE
-    | Float -> Typ.float ~bits:32 ~siz:(size_of x llt) ~enc:`IEEE
-    | Double -> Typ.float ~bits:64 ~siz:(size_of x llt) ~enc:`IEEE
-    | X86fp80 -> Typ.float ~bits:80 ~siz:(size_of x llt) ~enc:`Extended
-    | Fp128 -> Typ.float ~bits:128 ~siz:(size_of x llt) ~enc:`IEEE
-    | Ppc_fp128 -> Typ.float ~bits:128 ~siz:(size_of x llt) ~enc:`Pair
-    | Integer ->
-        Typ.integer ~bits:(Llvm.integer_bitwidth llt) ~siz:(size_of x llt)
-    | X86_mmx -> Typ.integer ~bits:64 ~siz:(size_of x llt)
-    | Function ->
-        let return = xlate_type_opt x (Llvm.return_type llt) in
-        let llargs = Llvm.param_types llt in
-        let len = Array.length llargs in
-        let args = Vector.init len ~f:(fun i -> xlate_type x llargs.(i)) in
-        Typ.function_ ~return ~args
-    | Pointer ->
-        if size_of x llt <> ptr_siz x then
-          todo "non-integral pointer types: %a" pp_lltype llt () ;
-        let elt = xlate_type x (Llvm.element_type llt) in
-        Typ.pointer ~elt
-    | Vector ->
-        let elt = xlate_type x (Llvm.element_type llt) in
-        let len = Llvm.vector_size llt in
-        Typ.array ~elt ~len ~siz:(size_of x llt)
-    | Array ->
-        let elt = xlate_type x (Llvm.element_type llt) in
-        let len = Llvm.array_length llt in
-        Typ.array ~elt ~len ~siz:(size_of x llt)
-    | Struct ->
-        let llelts = Llvm.struct_element_types llt in
-        let len = Array.length llelts in
-        let packed = Llvm.is_packed llt in
-        if Llvm.is_literal llt then
-          let elts =
-            Vector.map ~f:(xlate_type x) (Vector.of_array llelts)
-          in
-          Typ.tuple elts ~siz:(size_of x llt) ~packed
-        else
-          let name = struct_name llt in
-          if Llvm.is_opaque llt then Typ.opaque ~name ~siz:(size_of x llt)
+    if Llvm.type_is_sized llt then
+      let byts = size_of x llt in
+      let bits = bit_size_of x llt in
+      match Llvm.classify_type llt with
+      | Half | Float | Double | Fp128 -> Typ.float ~bits ~byts ~enc:`IEEE
+      | X86fp80 -> Typ.float ~bits ~byts ~enc:`Extended
+      | Ppc_fp128 -> Typ.float ~bits ~byts ~enc:`Pair
+      | Integer -> Typ.integer ~bits ~byts
+      | X86_mmx -> Typ.integer ~bits ~byts
+      | Pointer ->
+          if byts <> ptr_siz x then
+            todo "non-integral pointer types: %a" pp_lltype llt () ;
+          let elt = xlate_type x (Llvm.element_type llt) in
+          Typ.pointer ~elt
+      | Vector ->
+          let elt = xlate_type x (Llvm.element_type llt) in
+          let len = Llvm.vector_size llt in
+          Typ.array ~elt ~len ~bits ~byts
+      | Array ->
+          let elt = xlate_type x (Llvm.element_type llt) in
+          let len = Llvm.array_length llt in
+          Typ.array ~elt ~len ~bits ~byts
+      | Struct ->
+          let llelts = Llvm.struct_element_types llt in
+          let len = Array.length llelts in
+          let packed = Llvm.is_packed llt in
+          if Llvm.is_literal llt then
+            let elts =
+              Vector.map ~f:(xlate_type x) (Vector.of_array llelts)
+            in
+            Typ.tuple elts ~bits ~byts ~packed
           else
+            let name = struct_name llt in
             let elts =
               Vector.init len ~f:(fun i -> lazy (xlate_type x llelts.(i)))
             in
-            Typ.struct_ ~name elts ~siz:(size_of x llt) ~packed
-    | Token -> Typ.opaque ~name:"token" ~siz:(size_of x llt)
-    | Void | Label | Metadata -> assert false
+            Typ.struct_ ~name elts ~bits ~byts ~packed
+      | Function -> fail "expected to be unsized: %a" pp_lltype llt ()
+      | Void | Label | Metadata | Token -> assert false
+    else
+      match Llvm.classify_type llt with
+      | Function ->
+          let return = xlate_type_opt x (Llvm.return_type llt) in
+          let llargs = Llvm.param_types llt in
+          let len = Array.length llargs in
+          let args =
+            Vector.init len ~f:(fun i -> xlate_type x llargs.(i))
+          in
+          Typ.function_ ~return ~args
+      | Struct when Llvm.is_opaque llt -> Typ.opaque ~name:(struct_name llt)
+      | Token -> Typ.opaque ~name:"token"
+      | Vector | Array | Struct ->
+          todo "unsized non-opaque aggregate types: %a" pp_lltype llt ()
+      | Half | Float | Double | X86fp80 | Fp128 | Ppc_fp128 | Integer
+       |X86_mmx | Pointer ->
+          fail "expected to be sized: %a" pp_lltype llt ()
+      | Void | Label | Metadata -> assert false
   in
   Hashtbl.find_or_add memo_type llt ~default:(fun () ->
       [%Trace.call fun {pf} -> pf "%a" pp_lltype llt]
@@ -374,17 +384,16 @@ and xlate_value ?(inline = false) : x -> Llvm.llvalue -> Exp.t =
     | ConstantFP -> xlate_float x llv
     | ConstantPointerNull -> Exp.null
     | ConstantAggregateZero -> (
-        let llt = Llvm.type_of llv in
-        let typ = xlate_type x llt in
+        let typ = xlate_type x (Llvm.type_of llv) in
         match typ with
         | Integer _ -> Exp.integer typ Z.zero
         | Pointer _ -> Exp.null
         | Array _ | Tuple _ | Struct _ ->
-            let llsiz = size_of x llt in
-            if llsiz = 0 then todo "ConstantAggregateZero of size 0" () ;
+            let siz = Typ.size_of typ in
+            if siz = 0 then todo "ConstantAggregateZero of size 0" () ;
             Exp.splat typ
               ~byt:(Exp.integer Typ.byt Z.zero)
-              ~siz:(Exp.integer Typ.siz (Z.of_int llsiz))
+              ~siz:(Exp.integer Typ.siz (Z.of_int siz))
         | _ -> fail "ConstantAggregateZero of type %a" Typ.pp typ () )
     | ConstantVector | ConstantArray ->
         let typ = xlate_type x (Llvm.type_of llv) in
@@ -720,9 +729,9 @@ let landingpad_typs : x -> Llvm.llvalue -> Typ.t * Typ.t * Llvm.lltype =
 
 let exception_typs =
   let pi8 = Typ.pointer ~elt:Typ.byt in
-  let i32 = Typ.integer ~bits:32 ~siz:4 in
+  let i32 = Typ.integer ~bits:32 ~byts:4 in
   let exc =
-    Typ.tuple ~packed:false (Vector.of_array [|pi8; i32|]) ~siz:12
+    Typ.tuple ~packed:false (Vector.of_array [|pi8; i32|]) ~bits:96 ~byts:12
   in
   (pi8, i32, exc)
 
@@ -843,14 +852,12 @@ let xlate_instr :
   match opcode with
   | Load ->
       let reg = xlate_name x instr in
-      let llt = Llvm.type_of instr in
-      let len = Exp.integer Typ.siz (Z.of_int (size_of x llt)) in
+      let len = Exp.size_of (Exp.reg reg) in
       let ptr = xlate_value x (Llvm.operand instr 0) in
       emit_inst (Llair.Inst.load ~reg ~ptr ~len ~loc)
   | Store ->
       let exp = xlate_value x (Llvm.operand instr 0) in
-      let llt = Llvm.type_of (Llvm.operand instr 0) in
-      let len = Exp.integer Typ.siz (Z.of_int (size_of x llt)) in
+      let len = Exp.size_of exp in
       let ptr = xlate_value x (Llvm.operand instr 1) in
       emit_inst (Llair.Inst.store ~ptr ~exp ~len ~loc)
   | Alloca ->
@@ -862,8 +869,7 @@ let xlate_instr :
           (xlate_value x rand)
       in
       assert (Poly.(Llvm.classify_type (Llvm.type_of instr) = Pointer)) ;
-      let llt = Llvm.element_type (Llvm.type_of instr) in
-      let len = Exp.integer Typ.siz (Z.of_int (size_of x llt)) in
+      let len = Exp.size_of (Exp.reg reg) in
       emit_inst (Llair.Inst.alloc ~reg ~num ~len ~loc)
   | Call -> (
       let maybe_llfunc = Llvm.operand instr (Llvm.num_operands instr - 1) in
@@ -914,8 +920,7 @@ let xlate_instr :
             (* operator new(unsigned long, std::align_val_t) *) ] ->
             let reg = xlate_name x instr in
             let num = xlate_value x (Llvm.operand instr 0) in
-            let llt = Llvm.type_of instr in
-            let len = Exp.integer Typ.siz (Z.of_int (size_of x llt)) in
+            let len = Exp.size_of (Exp.reg reg) in
             emit_inst (Llair.Inst.alloc ~reg ~num ~len ~loc)
         | ["_ZdlPv" (* operator delete(void* ptr) *)]
          |[ "_ZdlPvSt11align_val_t"
@@ -1036,8 +1041,7 @@ let xlate_instr :
         when num_args > 0 ->
           let reg = xlate_name x instr in
           let num = xlate_value x (Llvm.operand instr 0) in
-          let llt = Llvm.type_of instr in
-          let len = Exp.integer Typ.siz (Z.of_int (size_of x llt)) in
+          let len = Exp.size_of (Exp.reg reg) in
           let dst, blocks = xlate_jump x instr return_blk loc [] in
           emit_term
             ~prefix:[Llair.Inst.alloc ~reg ~num ~len ~loc]
diff --git a/sledge/src/llair/term.ml b/sledge/src/llair/term.ml
index 708471092..c69bae17e 100644
--- a/sledge/src/llair/term.ml
+++ b/sledge/src/llair/term.ml
@@ -352,7 +352,9 @@ let invariant e =
   | ApN (Concat, mems) -> assert (Vector.length mems <> 1)
   | ApN (Record, elts) | RecN (Record, elts) ->
       assert (not (Vector.is_empty elts))
-  | Ap1 (Convert {dst; src}, _) -> assert (Typ.convertible src dst)
+  | Ap1 (Convert {dst; src}, _) ->
+      assert (not (Typ.equivalent dst src)) ;
+      assert (Typ.convertible dst src)
   | _ -> ()
   [@@warning "-9"]
 
@@ -497,12 +499,13 @@ let simp_extract ~unsigned bits arg =
   | _ -> Ap1 (Extract {unsigned; bits}, arg)
 
 let simp_convert ~unsigned dst src arg =
-  if (not unsigned) && Typ.equivalent dst src then arg
-  else
-    match (dst, src, arg) with
-    | Integer {bits= m; _}, Integer {bits= n; _}, Integer {data} ->
-        integer (Z.extract ~unsigned (min m n) data)
-    | _ -> Ap1 (Convert {unsigned; dst; src}, arg)
+  match (dst, src, arg) with
+  | Typ.Integer {bits= m; _}, Typ.Integer {bits= n; _}, Integer {data} ->
+      if (not unsigned) && m >= n then arg
+      else integer (Z.extract ~unsigned (min m n) data)
+  | _ ->
+      if Typ.equivalent dst src then arg
+      else Ap1 (Convert {unsigned; dst; src}, arg)
 
 (* arithmetic *)
 
@@ -949,9 +952,7 @@ let concat xs = normN Concat (Vector.of_array xs)
 let record elts = normN Record elts
 let select ~rcd ~idx = norm1 (Select idx) rcd
 let update ~rcd ~idx ~elt = norm2 (Update idx) rcd elt
-
-let size_of t =
-  Option.map ~f:(fun n -> integer (Z.of_int n)) (Typ.size_of t)
+let size_of t = integer (Z.of_int (Typ.size_of t))
 
 (** Transform *)
 
diff --git a/sledge/src/llair/term.mli b/sledge/src/llair/term.mli
index b74558223..47af58229 100644
--- a/sledge/src/llair/term.mli
+++ b/sledge/src/llair/term.mli
@@ -197,7 +197,7 @@ val rec_app :
      (module Hashtbl.Key with type t = 'id)
   -> (id:'id -> recN -> t lazy_t vector -> t) Staged.t
 
-val size_of : Typ.t -> t option
+val size_of : Typ.t -> t
 
 (** Transform *)
 
diff --git a/sledge/src/llair/typ.ml b/sledge/src/llair/typ.ml
index 9b1c18482..c8bd6a658 100644
--- a/sledge/src/llair/typ.ml
+++ b/sledge/src/llair/typ.ml
@@ -9,18 +9,19 @@
 
 type t =
   | Function of {return: t option; args: t vector}
-  | Integer of {bits: int; siz: int}
-  | Float of {bits: int; siz: int; enc: [`IEEE | `Extended | `Pair]}
+  | Integer of {bits: int; byts: int}
+  | Float of {bits: int; byts: int; enc: [`IEEE | `Extended | `Pair]}
   | Pointer of {elt: t}
-  | Array of {elt: t; len: int; siz: int}
-  | Tuple of {elts: t vector; siz: int; packed: bool}
+  | Array of {elt: t; len: int; bits: int; byts: int}
+  | Tuple of {elts: t vector; bits: int; byts: int; packed: bool}
   | Struct of
       { name: string
       ; elts: t vector (* possibly cyclic, name unique *)
             [@compare.ignore] [@equal.ignore] [@sexp_drop_if fun _ -> true]
-      ; siz: int
+      ; bits: int
+      ; byts: int
       ; packed: bool }
-  | Opaque of {name: string; siz: int}
+  | Opaque of {name: string}
 [@@deriving compare, equal, hash, sexp]
 
 let rec pp fs typ =
@@ -78,34 +79,41 @@ let invariant t =
 (** Constructors *)
 
 let function_ ~return ~args = Function {return; args} |> check invariant
-let integer ~bits ~siz = Integer {bits; siz} |> check invariant
-let float ~bits ~siz ~enc = Float {bits; siz; enc} |> check invariant
+let integer ~bits ~byts = Integer {bits; byts} |> check invariant
+let float ~bits ~byts ~enc = Float {bits; byts; enc} |> check invariant
 let pointer ~elt = Pointer {elt} |> check invariant
-let array ~elt ~len ~siz = Array {elt; len; siz} |> check invariant
-let tuple elts ~siz ~packed = Tuple {elts; siz; packed} |> check invariant
-let opaque ~name ~siz = Opaque {name; siz} |> check invariant
+
+let array ~elt ~len ~bits ~byts =
+  Array {elt; len; bits; byts} |> check invariant
+
+let tuple elts ~bits ~byts ~packed =
+  Tuple {elts; bits; byts; packed} |> check invariant
+
+let opaque ~name = Opaque {name} |> check invariant
 
 let struct_ =
   let defns : (string, t) Hashtbl.t = Hashtbl.create (module String) in
-  let dummy_typ = Opaque {name= "dummy"; siz= 0} in
-  fun ~name ~siz ~packed elt_thks ->
+  let dummy_typ = Opaque {name= "dummy"} in
+  fun ~name ~bits ~byts ~packed elt_thks ->
     match Hashtbl.find defns name with
     | Some typ -> typ
     | None ->
         (* Add placeholder defn to prevent computing [elts] in calls to
            [struct] from [elts] for recursive occurrences of [name]. *)
         let elts = Array.create ~len:(Vector.length elt_thks) dummy_typ in
-        let typ = Struct {name; elts= Vector.of_array elts; siz; packed} in
+        let typ =
+          Struct {name; elts= Vector.of_array elts; bits; byts; packed}
+        in
         Hashtbl.set defns ~key:name ~data:typ ;
         Vector.iteri elt_thks ~f:(fun i (lazy elt) -> elts.(i) <- elt) ;
         typ |> check invariant
 
 (** Constants *)
 
-let bool = integer ~bits:1 ~siz:1
-let byt = integer ~bits:8 ~siz:1
-let int = integer ~bits:32 ~siz:4
-let siz = integer ~bits:64 ~siz:8
+let bool = integer ~bits:1 ~byts:1
+let byt = integer ~bits:8 ~byts:1
+let int = integer ~bits:32 ~byts:4
+let siz = integer ~bits:64 ~byts:8
 
 (** [ptr] is semantically equivalent to [siz], but has a distinct
     representation because the element type is important for [Global]s *)
@@ -113,38 +121,39 @@ let ptr = pointer ~elt:byt
 
 (** Queries *)
 
+let bit_size_of = function
+  | (Function _ | Opaque _) as t ->
+      fail "bit_size_of requires is_sized: %a" pp t ()
+  | Integer {bits; _}
+   |Float {bits; _}
+   |Array {bits; _}
+   |Tuple {bits; _}
+   |Struct {bits; _} ->
+      bits
+  | Pointer _ -> 64
+
 let size_of = function
-  | Function _ -> None
-  | Integer {siz}
-   |Float {siz}
-   |Array {siz}
-   |Tuple {siz}
-   |Struct {siz}
-   |Opaque {siz} ->
-      Some siz
-  | Pointer _ -> Some 8
-
-let rec prim_bit_size_of = function
-  | Integer {bits} | Float {bits} -> Some bits
-  | Pointer _ -> prim_bit_size_of siz
-  | Array {elt; len} ->
-      Option.map (prim_bit_size_of elt) ~f:(fun n -> n * len)
-  | Function _ | Tuple _ | Struct _ | Opaque _ -> None
+  | (Function _ | Opaque _) as t ->
+      fail "size_of requires is_sized: %a" pp t ()
+  | Integer {byts; _}
+   |Float {byts; _}
+   |Array {byts; _}
+   |Tuple {byts; _}
+   |Struct {byts; _} ->
+      byts
+  | Pointer _ -> 8
 
 let rec equivalent t0 t1 =
   match (t0, t1) with
-  | (Pointer _ | Integer _), (Pointer _ | Integer _) -> (
-    match (prim_bit_size_of t0, prim_bit_size_of t1) with
-    | Some n0, Some n1 -> n0 = n1
-    | _ -> false )
+  | (Pointer _ | Integer _), (Pointer _ | Integer _) ->
+      bit_size_of t0 = bit_size_of t1
   | Array {elt= t; len= m}, Array {elt= u; len= n} ->
       m = n && equivalent t u
   | _ -> equal t0 t1
 
 let castable t0 t1 =
-  match (size_of t0, size_of t1) with
-  | Some m, Some n -> m = n
-  | _ -> equal t0 t1
+  (is_sized t0 && is_sized t1 && bit_size_of t0 = bit_size_of t1)
+  || equal t0 t1
 
 let rec convertible t0 t1 =
   castable t0 t1
diff --git a/sledge/src/llair/typ.mli b/sledge/src/llair/typ.mli
index c9d8a6882..0473086c1 100644
--- a/sledge/src/llair/typ.mli
+++ b/sledge/src/llair/typ.mli
@@ -10,19 +10,24 @@
 type t = private
   | Function of {return: t option; args: t vector}
       (** (Global) function names have type Pointer to Function. *)
-  | Integer of {bits: int; siz: int}  (** Integer of given bitwidth. *)
-  | Float of {bits: int; siz: int; enc: [`IEEE | `Extended | `Pair]}
+  | Integer of {bits: int; byts: int}  (** Integer of given bitwidth. *)
+  | Float of {bits: int; byts: int; enc: [`IEEE | `Extended | `Pair]}
       (** Floating-point numbers of given bitwidth and encoding. *)
   | Pointer of {elt: t}  (** Pointer to element type. *)
-  | Array of {elt: t; len: int; siz: int}
+  | Array of {elt: t; len: int; bits: int; byts: int}
       (** Statically-sized array of [len] elements of type [elt]. *)
-  | Tuple of {elts: t vector; siz: int; packed: bool}
+  | Tuple of {elts: t vector; bits: int; byts: int; packed: bool}
       (** Anonymous aggregate of heterogeneous types. *)
-  | Struct of {name: string; elts: t vector; siz: int; packed: bool}
+  | Struct of
+      { name: string
+      ; elts: t vector
+      ; bits: int
+      ; byts: int
+      ; packed: bool }
       (** Uniquely named aggregate of heterogeneous types. Every cycle of
           recursive types contains a [Struct]. NOTE: recursive [Struct]
           types are represented by cyclic values. *)
-  | Opaque of {name: string; siz: int}
+  | Opaque of {name: string}
       (** Uniquely named aggregate type whose definition is hidden. *)
 [@@deriving compare, equal, hash, sexp]
 
@@ -39,22 +44,30 @@ val int : t
 val siz : t
 val ptr : t
 val function_ : return:t option -> args:t vector -> t
-val integer : bits:int -> siz:int -> t
-val float : bits:int -> siz:int -> enc:[`Extended | `IEEE | `Pair] -> t
+val integer : bits:int -> byts:int -> t
+val float : bits:int -> byts:int -> enc:[`Extended | `IEEE | `Pair] -> t
 val pointer : elt:t -> t
-val array : elt:t -> len:int -> siz:int -> t
-val tuple : t vector -> siz:int -> packed:bool -> t
-val struct_ : name:string -> siz:int -> packed:bool -> t lazy_t vector -> t
-val opaque : name:string -> siz:int -> t
+val array : elt:t -> len:int -> bits:int -> byts:int -> t
+val tuple : t vector -> bits:int -> byts:int -> packed:bool -> t
 
-(** Queries *)
+val struct_ :
+  name:string -> bits:int -> byts:int -> packed:bool -> t lazy_t vector -> t
+
+val opaque : name:string -> t
 
-val size_of : t -> int option
-val prim_bit_size_of : t -> int option
+(** Queries *)
 
 val is_sized : t -> bool
 (** Holds of types which are first-class and have a statically-known size. *)
 
+val bit_size_of : t -> int
+(** The number of bits required to hold a value of the given type. Raises
+    unless [is_sized] holds. *)
+
+val size_of : t -> int
+(** The number of bytes between adjacent values of the given type, including
+    alignment padding. Raises unless is_sized holds. *)
+
 val equivalent : t -> t -> bool
 (** Equivalent types are those that denote the same sets of values in the
     semantic model. An equivalence relation. *)
diff --git a/sledge/src/symbheap/exec.ml b/sledge/src/symbheap/exec.ml
index f943e895d..686167b64 100644
--- a/sledge/src/symbheap/exec.ml
+++ b/sledge/src/symbheap/exec.ml
@@ -328,7 +328,7 @@ let calloc_spec us reg num len =
   let post = Sh.or_ (null_eq (Term.var reg)) (Sh.seg seg) in
   {xs; foot; sub; ms; post}
 
-let size_of_ptr = Option.value_exn (Term.size_of Typ.ptr)
+let size_of_ptr = Term.size_of Typ.ptr
 
 (* { p-[_;_)->⟨W,_⟩ }
  *   posix_memalign r p s
@@ -529,7 +529,7 @@ let nallocx_spec us reg siz =
   let post = Sh.or_ (null_eq loc) (Sh.pure (Term.eq loc siz)) in
   {xs; foot; sub; ms; post}
 
-let size_of_int_mul n = Term.mul (Option.value_exn (Term.size_of Typ.siz)) n
+let size_of_int_mul = Term.mul (Term.size_of Typ.siz)
 
 (* { r-[_;_)->⟨m,_⟩ * i-[_;_)->⟨_,m⟩ * w=0 * n=0 }
  *   mallctl r i w n