Fixes ARM/Thumb movt semantics

lib/arm/arm_lifter.ml

@@ -227,7 +227,8 @@ let lift_move ~encoding mem ops (insn : move_insn) : stmt list =
 
   | `MOVTi16, [|`Reg dest; _; src; cond; _wflag|] ->
     let dest = Env.of_reg dest in
-    [Bil.move dest Bil.(var dest lor exp_of_op src lsl int32 16)] |>
+    let src16 = Bil.(cast unsigned 32 (cast low 16 (var dest))) in
+    [Bil.move dest Bil.(src16 lor exp_of_op src lsl int32 16)] |>
     fun ins -> exec ins cond
   | insn,ops ->
     fail [%here] "ops %s doesn't match move insn %s"