Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!samsung!uunet!zephyr.ens.tek.com!orca!frip!andrew
From: andrew@frip.WV.TEK.COM (Andrew Klossner)
Newsgroups: comp.sys.m88k
Subject: Re: Info about the 88open Consortium and standards
Message-ID: <5352@orca.WV.TEK.COM>
Date: 15 Nov 89 17:35:50 GMT
References: <1948@psueea.UUCP> <1989Nov14.175806.23483@paris.ics.uci.edu>
Sender: nobody@orca.WV.TEK.COM
Reply-To: andrew@frip.wv.tek.com
Organization: Tektronix, Wilsonville, Oregon
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[]

	"(a) you are limited to passing at most 8 words worth of actual
	parameters in registers (which seems an unnecessary and
	artificial limit to me)"

Yep.  This covers 98%+ of procedure calls in real-world code.

	"(b) more significantly, there seems to have been a major
	departure from the common practice in the good ol' CICS days
	when callers could assume that almost all registers (except for
	the one which got the return value) were *preserved* across a
	"standard" call."

Registers r14 and up are preserved.  That's more registers than those
good ol' CISC machines preserved.

	"It seems to me that (b) effectively ties the hands of many
	otherwise very sophisticated modern optimizers (with nice
	graph-coloring register allocators of course)."

Not at all.  If you have the global program view necessary to do
graph-coloring (you are generating the code for all calls to the
caller), then it's fairly obvious that you can generate any code you
want, and need not conform to the standard interface.  The OCS serves
only to guide compilers/linkers in making procedure interfaces for
callers that they do not control.

  -=- Andrew Klossner   (uunet!tektronix!frip.WV.TEK!andrew)    [UUCP]
                        (andrew%frip.wv.tek.com@relay.cs.net)   [ARPA]