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From: greg@ncr-sd.SanDiego.NCR.COM (Greg Noel)
Newsgroups: comp.lang.c
Subject: Re: MSC and stack manipulation
Message-ID: <1809@ncr-sd.SanDiego.NCR.COM>
Date: Fri, 9-Oct-87 17:37:13 EDT
Article-I.D.: ncr-sd.1809
Posted: Fri Oct  9 17:37:13 1987
Date-Received: Sun, 11-Oct-87 16:44:43 EDT
References: <325@picuxa.UUCP>
Reply-To: greg@ncr-sd.SanDiego.NCR.COM (Greg Noel)
Organization: NCR Corporation, Rancho Bernardo
Lines: 17
Keywords: MSC

Nobody seems to have risen to this, so I'll speculate a possibility.

In article <325@picuxa.UUCP> gp@picuxa.UUCP (Greg Pasquariello X1190) writes:
>....  Therefor the next push will put the value
>of the register (whatever it may be) two bytes below the previous push
>thus leaving a gap in the stack of two bytes.

The PDP-11 compiler did this.  The observation was that there were a lot of
one- and two-argument functions being called.  Leaving a gap essentially
pre-allocated the space for one argument, making the calling sequence shorter
-- the stack adjustment upon return from a one-argument function is no longer
required.  Also, on the PDP-11, the two-argument case was also optimized,
since a shorter (one word) instruction could clean up the stack pointer.

MSC may be doing something similar.
-- 
-- Greg Noel, NCR Rancho Bernardo     Greg.Noel@SanDiego.NCR.COM