m68k: GAS equvivalent of DS.B

[Geir Frode Raanes]

On Mon, 12 Oct 1998, Dony wrote:

> The equivalent MRI directives in GAS :
> 	MRI	|	GAS
> ------------------------------------------
> 	DS.B	|	.comm	label,1
> 	DS.W	|	.comm	label,2
> 	DS.L	|	.comm	label,4

I thought of this but had to drop it.
Unfortunately, I need 'label' to be placed *in the current section,*
and not in the BSS section.  According to further out into the same 
gas documentation you included below, both the '.comm' and '.lcomm' 
directives will place 'label' into the BSS section.  Guess I could 
hack the current section into becoming a/the BSS section, but that 
kind of defeats the point.

So, the prior suggestion of using 'label: .space 1/2/4*n' seems like my
best and most transparent option.  The downside of this is that I do not
get any type checking of my code.  Not that I am all that certain the
Motorola assembler does that either.


> GAS use MIT syntax which is slightly different from Motorola syntax.

According to the documetation - which you where kind enough to 
include below - gas can interpret both version interchangeabely.  
I personally prefer Motorola syntax, both with the intervening 
periods "." and the address mode notation.

But the issue is what syntax the MRI assembler use.  My testing revails
that it does at least accept Motorola syntax.  It renders standard gas
directives illegal and reimplent among others the 'DS.B/W/L' motorola
directive. This is the main reason I would like to use this compatibility
mode - at least for parts of my porting effort.  (I.e. NO porting effort.)

But in the meantime I have discovered what went wrong.  
All my two-operands opcodes failed while single-operand opcodes 
passed.  It appears that the MRI compiler does not accept whitespace 
between the operands.  Thus, the following code is perfectly legal
m68k-coff-as assembly code:

	.mri 1

		DELETE		equ	8
		LINE_BUF	ds.b	64
				lea.l	DELETE,A1
				clr.w	LINE_BUF(A2)
				move.l	(A2),D1
				move.l  255(A1,D1),D2
 				move.l  $FFFF(PC),D3


And by that, I am close to all set.  The remaining two problems is that
gas does not accept '.mri 0' to *leave* MRI compatible mode, eventhough 
it should according to the documentation.  But EOF does the same thing 
so this shortcoming/bug I can live with.  The other is that the
documentation spesifically reserve against the MRI 'ORG' directive.
That means rearranging the source code.

But still, thank you all for the effort.


> with the Sun assembler. Intervening periods are
> ignored; for example, `movel' is ***equivalent*** to `move.l'. 

> Absolute 
>      `symbol', or `digits', optionally followed by `:b', `:w', or `:l'. 


This one looks promising but I am not certain on how to use it.


> The immediate character is `#' for Sun compatibility. 
> The line-comment character is `|' 

Unless in MRI compatibility mode, where the usual Motorola style '*' 
is used as a line-comment character.


--
  ******************************************************

  Never ever underestimate the power of human stupidity.
  -Robert Anson Heinlein

		GeirFRS@invalid.ed.ntnu.no

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