What logic gets synthesized when I use an integer instead of a reg variable as a storage element? Is use of integer recommended?

An  integer  can  take  place  of  a  reg  as  a  storage  element.  An instance to illustrate  this  is  as follows:

In  this  example,  variable  int_tmp  is  defined  as  an  integer,  rather than reg  that  it  would normally be (the reg declaration is commented in the instance for illustration). Note that, although default  width  of  the  integer  declaration  is  32  bits,  final  result  of  the  int_tmp  registers synthesis  yield  is  only  4  bits.  This  is  since the  optimiser  in  the  synthesis  tool  removes  the unnecessary higher order bits, in order to minimize the area.

Even though  the  use  of  integer  as  shown  above  is  a  legal  construct,  it's  not  recommended  for  the synthesis of storage elements.