Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!rice!sun-spots-request
From: charyb!dan@uunet.uu.net (Dan Mick)
Newsgroups: comp.sys.sun
Subject: Re: Porting Questions
Keywords: Miscellaneous
Message-ID: <4854@brazos.Rice.edu>
Date: 7 Feb 90 18:25:19 GMT
Sender: root@rice.edu
Organization: Sun-Spots
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Approved: Sun-Spots@rice.edu
X-Refs:  Original: v9n21
X-Sun-Spots-Digest: Volume 9, Issue 38, message 6

In article <4635@brazos.Rice.edu> larus@spool.cs.wisc.edu writes:
>X-Sun-Spots-Digest: Volume 9, Issue 21, message 9 of 13
>
>1.  Are any of the global registers (%g1 -- %g7) available to programs?
>Or, a better question, what are these registers used for?

Some of them are off-limits to the compilers, but some are used as part of
the normal register-allocation scheme.  I haven't been able to figure out
if any are available outside the compilers, and those that are may well be
used by the kernel...I've not seen any documentation on that either.

>2.  Is there any trick to doing an unaligned load/store of a word (4 byte
>quantity)?  I can do it with a sequence of load-byte/store-byte's and
>shifts, but I find it hard to believe that this is really the best
>technique.

Nope...that's all you get.  The CPU simply doesn't have the bus mux/demux
that CISC chips, in particular Moto chips, provide.