Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!ncrlnk!ncr-sd!hp-sdd!ucsdhub!ucsd!nosc!helios.ee.lbl.gov!pasteur!agate!bizet.Berkeley.EDU!matloff
From: matloff@bizet.Berkeley.EDU (Norman Matloff)
Newsgroups: comp.arch
Subject: Re: multiple register windows
Message-ID: <16155@agate.BERKELEY.EDU>
Date: 28 Oct 88 20:05:08 GMT
Article-I.D.: agate.16155
References: <156@gloom.UUCP> <310@lynx.zyx.SE> <332@pvab.UUCP> <15964@agate.BERKELEY.EDU> <23367@amdcad.AMD.COM> <16003@agate.BERKELEY.EDU>
Sender: usenet@agate.BERKELEY.EDU
Reply-To: matloff@iris.ucdavis.edu (Norm Matloff)
Organization: EECS, UC Davis
Lines: 25

In article <536@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes:
*In article <16054@agate.BERKELEY.EDU> matloff@iris.ucdavis.edu (Norm Matloff) writes:

*>A compiler which automatically inlines procedure calls might be able
*>to do what you are saying.  However, there may be some unpleasant
*>side effects, depending on the language.  Actually, one of my grad
*>students in making a thesis out of this, so I'll try to report more
*>on it later.

*Don't forget that one of the side effects of having your registers
*arranged into windows is that you don't have access to very many 
*registers from within any given procedure.  There are routines
*that need lots of them, and there are routines that need very
*few.  The one-size-fits-all approach is not what a good compiler
*wants; it would rather see them all at once and do the management
*explicitly.  The windowing is just a hack to make parameter-passing
*cheap, which a compiler can do just as well or better.

There was a good suggestion (I don't remember the reference, maybe
the Huguet and Lang paper) to have variable-size windows, but only
in a FEW sizes, solving the one-size-fits-all problem at a low time
cost (as I recall, this was achieved by restricting window sizes to
powers of 2).

   Norm