limit check insertion

[Henry Cejtin]

With  regards  to  exposing  address  arithmetic (in array references and the
like) this strikes me as a big win.  Some day we want  to  have  things  like
replacing  array subscripting with induction variables that are pointers, and
even barring that it is probably not hard to expose the common sub-expression
which is multiplying by array element size in something like an array copy.

The  original  argument  for pointer arithmetic in C was exactly so that this
kind of common sub-expression stuff could be done (by a human of course since
the C compilers of the day had no chance).