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Re: Segment register support for the i386
- To: torvalds at transmeta dot com (Linus Torvalds)
- Subject: Re: Segment register support for the i386
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Mon, 27 Dec 1999 05:55:06 -0700
- cc: gcc at gcc dot gnu dot org
- Reply-To: law at cygnus dot com
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