fixing i386 gas for 16-bit code
Ian Lance Taylor
ian@cygnus.com
Thu Jun 20 08:46:00 GMT 1996
Date: Wed, 19 Jun 1996 00:41:40 -0500
From: VaX#n8 <vax@linkdead.paranoia.com>
I was wondering if you know how hard it would be (for me) to fix gas
to create 16-bit code properly, especially in the case of SIB (scaled
indexed based) addressing modes on the i386.
I don't know much about the i386 myself, so I'm CC'ing your note to
the gas developers list, gas2@cygnus.com. Perhaps somebody on the
list will have some useful information.
I have to hand code things like:
movb 1(%si), %dh
because it flubs the Mod-R/M byte.
Another cool thing would be 8-bit offset addressing. Coding all this by
hand is hair-pulling material. It is so ugly I chose not to do it :)
I used to hand code stuff when I was a kid, but it's pretty horrifying
to think that anybody still has to do it.
I believe that there are some 16 bit i386 assemblers out there.
Would I have to learn bfd? It confused the heck outta me when I looked
at the bfd source last time :-/
You shouldn't have to look at BFD for this sort of thing.
Ian
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