Abstracting pointer arithmetic

[Richard Kenner]

  Back ends should define Pmode to be a mode distinct from any other
  mode which used by the back end.  Maybe PSImode can be used for this,
  or maybe there can be an actual Pmode.

  The machine description should define insns for pointer arithmetic.
  They should be named "addsip3", "subsip3", "subpsi3", "tstp", and
  "cmpp", or something like that.  

I *strongly* disagree with this.  It will essentially mean repeating all
the computational instruction with this mode and also make things very
difficult for things such as combine.c.

Please say *precisely*what problem you are trying to solve first.
Once we know that, it will be possible to suggest things that will
work, but it would seem to me that such an abstraction should be at
the tree level.