gas: additional macro functionality (patch attached)

[Olaf Püschel]

Hi!

When I was trying to implement a direct threaded code interpreter  
(forth look alike)
with gas for the msp430 microcontroller, I missed the possibility to  
reference
a) the individual invocation count of each macro and b) the previous  
invocation
count for each macro.

Problem: I need to build a single linked list at assemble time. This  
is traditionally
done with somethink like:

                .set LINK, 0

.macro  HEAD foo, bar
                ...
                .word   LINK
                .set            LINK,.
                .endm

This does not work with gas assembling msp430 code on a PPC Mac, because
LINK only gets resoved at relocation time, so all LINK fields are the  
same :-(

The presence of the \@ ideom hinted to me, that I could easily tweak  
gas to yield
the information I need. So I made two changes::

1) "macro_entry" gets another field "count", giving the individual  
invocation count
2) The ideoms \#, \< and \> yield the current, previous amd next  
invocation count
    when used in a macro.

So I can write the linked list code like:

.macro          HEAD len,name,link,flags=0
lnk\#:          .byte   (\flags << 5) | \len
nam\@:          .ascii  "\name"
                        .org    nam\@ + 3                       ; pad short 
names
                        .word   lnk\<
                        .endm

Tested, works :-)

I would love to see my code incorporated in the next gas release,  
since I consider
it useful not only to me. If you need to have some documentation  
writen to do this,
i'll be happy to provide it.

Attached are the diff's for macro.h and macro.c

Best regards
Olaf

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gas-2.17_macro.c.diff
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gas-2.17_macro.h.diff
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