Re: Calling seguence for 65816 (Was: 8/16 bit compilers)

mercier@pongo.West.Sun.COM (Bob Mercier) writes:


>I'm working on a tiny compiler for the 65816 and was trying to work out a
>decent calling sequence for function calls.


>I assumed native mode (16 bit X, Y and A) and wanted to be able to access
>more than 256 bytes of local variables so I didn't use d,s.


>If you can think of anything shorter that will allow easy access to more
>than 256 bytes of locals and recursive functions, please let me know!


>bob.mercier@cypress.west.sun.com




Here's a better way of doing for good performance:




local1 equ 1 ;local variable
local2 equ local1+2 ;local variable
space equ local2+2 ;how much space to reserve for locals
parm1 equ space+3 ;this is the first passed parameter
parm2 equ parm1+2 ;this is another parameter
end equ parm2+2 ;total stack used


tsc
sec
sbc #space-1
tcs
phd
tcd


at this point, you can use straight direct page access for local
variables and the passed parameters


lda <parm1
sta <local1


the following code will exit...x&y are untouched for returning values


lda <space
sta <end-3
lda <space+1
sta <end-2
pld
tsc
clc
adc #end-4
tcs
rtl






here's how we'd call it:


pea 1 ;parm2
pea 23 ;parm1
jsl proc


and we're done...the stack is already cleaned up for us


-tim
--

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