(** Conversions from ints to floats can be defined as bitwise manipulations
  over the in-memory representation.  This is what the PowerPC port does.
  The trick is that [from_words 0x4330_0000 x] is the float
  [2^52 + of_intu x]. *)

Definition ox4330_0000 := Int.repr 1127219200.

Lemma ox8000_0000_signed_unsigned: forall x, Int.unsigned (Int.add x ox8000_0000) = Int.signed x + Int.half_modulus.