Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!asuvax!hrc!gtephx!campbellb
From: campbellb@...!asuvax!gtephx (Brian Campbell)
Newsgroups: comp.sys.apple2
Subject: Re: ML subroutines (passing parameters in ML)
Summary: What about stack indexing?
Message-ID: <1991Apr29.203359.250@...!asuvax!gtephx>
Date: 29 Apr 91 20:33:59 GMT
References: <3397@kluge.fiu.edu> <13845@ucrmath.ucr.edu>
Organization: gte
Lines: 16

In article <13845@ucrmath.ucr.edu>, rhyde@musial.ucr.edu (randy hyde) writes:
> 4) Pass parameters on the stack.  This is how most HLLs pass parameters.
> It is slow, big, and accessing the parameters is inconvenient,
> especially on processors like the 65816 which don't have a frame pointer
> register.  Nonetheless, there are some advantages to this technique: 

I thought that the 65816 had a stack addressing mode that allows one to
"random" access values on the stack (which is not present
on the 6502).  It looks like this: (i,S) which I take to mean, access the
word at offset i relative to the Stack pointer.  So an immediate value of 0,
means access the last word pushed, 2 means access the previous word pushed,
etc.  I've not had any experience with this mode -- but am I right or wrong?
(Of course, it would access a byte with the m flag = 1).
BTW, if all of this is true, in a assembly routine, to by-pass the JSL
return address, would you typically use offsets of 3,5,7... to get word
parameters n,n-1,n-2,... where n is the number of data words pushed?