[sledge] Strengthen simplification of Convert exps

Summary: Omit casts when source and destination types are equal.

Reviewed By: mbouaziz

Differential Revision: D14495814

fbshipit-source-id: 21bcfb6ab

sledge/src/llair/exp.ml

@@ -654,6 +654,7 @@ let float data = Float {data} |> check invariant
 
 let simp_convert signed (dst : Typ.t) src arg =
   match (dst, arg) with
+  | _ when Typ.equal dst src -> arg
   | Integer {bits= m}, Integer {data; typ= Integer {bits= n}} ->
       integer (Z.clamp ~signed (min m n) data) dst
   | _ -> App {op= Convert {signed; dst; src}; arg}