Segment register support for the i386

[Jeffrey A Law]

  In message < 840i8n$1pp$1@penguin.transmeta.com >you write:
  > I know there were horrible problems with disambiguating pointer
  > dereferences that looked the same: CSE needs to be _very_ careful.  If
  > you go ahead with this, would suggest adding a case like this to your
  > test-suite:
Yes CSE and other passes would all have to know about this kind of
stuff.  Though I don't think it would be that nasty since a seg + offset
pointer would have a different mode than just an offset pointer.

The tougher problem is the general infrastructure to have pointers of
differing sizes, supporting partial mode arithmetic, and ABI issues with
segment/space registers.

Various people looked at supporting segments/spaces in the distant past
(early 90s) but I don't have snapshots of their code anymore.

jeff