From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cagney <ac131313@cygnus.com>
To: Eli Zaretskii <eliz@is.elta.co.il>
Cc: gdb-patches@sources.redhat.com
Subject: Re: [rfa(arm)/rfc] Eliminate HOST_{FLOAT,DOUBLE,...}_FORMAT
Date: Fri, 29 Jun 2001 08:31:00 -0000
Message-id: <3B3C9C03.7000704@cygnus.com>
References: <3B3C1A5C.3060906@cygnus.com> <5137-Fri29Jun2001120040+0300-eliz@is.elta.co.il>
X-SW-Source: 2001-06/msg00520.html

> To me, the comment doesn't make sense.  If sizeof (host long double) == 
>> size of (target long double) and information is still being lost then I 
>> think floatformat_* has a bug.
> 
> 
> You could lose information if the original value's bit pattern is not
> a valid FP number.  Does floatformat_to_doublest handle these
> situations 110% correctly?  I see at least one FIXME comment in the
> code there.


At present this loss happens randomly depending on the host / target 
combination.  I would prefer GDB to at least have slightly more 
consistent behavour.

The next step would be to ramp up sim/common/sim-fpu.[hc] and use that 
for all FP caculations.

--

Anyway, looking at the code, yes there are several nasty errors:

   unsigned long mant;

should be ULONGEST so that it fits a 64 bit mantisa and:

       dto += ldexp ((double) mant, exponent - mant_bits);

unfortunatly doesn't take a ``long double''.

   /* Note that if exponent indicates a NaN, we can't really do anything 
useful
      (not knowing if the host has NaN's, or how to build one).  So it will
      end up as an infinity or something close; that is OK.  */


sigh.

	Andrew