Re: Problem with the MiNT library, -m68020

[Juergen Lock <nox@jelal.hb.north.de>]

greetings...

 Michael reminded us of this somewhat older message from entropy,
can someone with a >= 68020 + 68881 and who knows our floatlib a bit
better than me :) (Andreas?) look into this?  i.e. is this all that
needs be fixed, etc...

 thanx + cheers
	Juergen

Nicholas S Castellano writes:

> I recently was working with a program that uses floating point math.
> I discovered that it worked correctly if compiled without -m68020, but
> if compiled with -m68020 -lgnu020, I got some really strange behavior:
> 
> int
> main()
> {
>   double d;
>   int i = 200;
>   d = (double) i;
>   printf("%f\n", d);
> }
> 
> ...yields output of 0.0.
> 
> The problem seems to be in the 68881 version of the __floatsidf
> routine.  The following patch seems to cure my problem.  However, the
> solution provided here is based on GUESSWORK:  I do not have a manual
> for the 68881 and I do not really know what order GCC expects to find
> the return values in d0,d1.  My guess was based only on the fact that
> the SFP version of the code loads d0 first and then d1, whereas the
> 68881 version uses a moveml to d0-d1 (which loads d1 first and then
> d0).  This may be irrelevant, but it's all I had to work with.  Could
> someone with more docs and more of a clue look into this?  I think the
> problem may affect several other conversion routines as well.
> 
> Cheers,
> entropy
> 
> --- 45.1	1994/07/17 10:49:40
> +++ _fltsi.cpp	1994/08/12 17:04:14
> @@ -15,7 +15,8 @@
>  |
>  	fintrzd a7@(4),fp0		| load long int to fp0
>  	fmoved	fp0,a7@-		| get double from fp0
> -	moveml	a7@+,d0-d1
> +	movel	a7@+,d0
> +	movel	a7@+,d1
>   	rts
>  
>  #endif	__M68881__
> 
> 
> 
> --
> entropy -- it's not just a good idea, it's the second law.
> Personal mail:      entropy@gnu.ai.mit.edu
> MiNT library mail:  entropy@terminator.rs.itd.umich.edu
> "what do you have against octal?" -jrb

-- 
J"urgen Lock / nox@jelal.hb.north.de / UUCP: ..!uunet!unido!uniol!jelal!nox
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