Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!seismo!mcvax!nikhefh!gert
From: gert@nikhefh.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Megamax inline assembly woes (solution)
Message-ID: <270@nikhefh.UUCP>
Date: Wed, 6-May-87 05:41:36 EDT
Article-I.D.: nikhefh.270
Posted: Wed May  6 05:41:36 1987
Date-Received: Fri, 8-May-87 01:35:36 EDT
References: <8705030519.AA18707@ucbvax.Berkeley.EDU> <1058@bath63.ux63.bath.ac.uk>
Reply-To: gert@nikhefh.UUCP (Gert Poletiek)
Distribution: world
Organization: Nikhef-H, Amsterdam (the Netherlands).
Lines: 70

In article <1058@bath63.ux63.bath.ac.uk> sc_dra@ux63.bath.ac.uk (Dave Allum) writes:
>
>The registers have to be in upper case, i.e. A0, D3 etc.  Also SP is not
>recognised so use A7 or put a #define SP A7 in your program.  From memory
>the Megamax manual does mention the upper case requirement.

The registers must indeed be in upper case (and it says so in the manual).
To make the assembler/compiler accept 'normal' assembly language use 
definitions like:

#define	sp	A7
#define	a0	A0

etc.

Since the preprocessor, compiler, and assembler are one program this works
perfectly. Using the same method you can also change the opcodes, like

#define dbra	dbf


Something that is not (fully) covered in the manual is the way you can 
use assembler routines with C declarations:

copy ( from, to, size )
char	*from, *to;
int	size;
{
	asm  {
		movea.l	from(a6),a0
		movea.l	to(a6),a1
		move.w	size(a6),d0
		bra.s	cpend
	 cploop:
		move.b	(a0)+,(a1)+
	 cpend:
		dbra	cploop,d0
	}
}


Or the same routine can be written as:


copy ( from, to, size )
register char	*from, *to;
register int	size;
{
	asm  {
		bra.s	cpend
	 cploop:
		move.b	(from)+,(to)+
	 cpend:
		dbra	cploop,size
	}
}



The inline assembly implementation is really the best part of the Megamax
package. All the other parts contain one or more bugs.

The Mark Williams package is far better, it implements K&R to the full,
and the extensions like struct assignment, structs as function arguments,
functions returning structs, enumerated type. The only thing it lacks is 
an in line assembly implementation like Megamax.



Gert Poletiek