From: Richard Henderson <rth@cygnus.com>
To: moshier@mediaone.net, Richard Henderson <rth@cygnus.com>
Cc: law@cygnus.com, Jan Hubicka <hubicka@atrey.karlin.mff.cuni.cz>,
egcs@cygnus.com, Marc Lehmann <pcg@goof.com>
Subject: Re: expand and truncate and 387
Date: Fri, 27 Nov 1998 08:53:00 -0000 [thread overview]
Message-ID: <19981127085125.A616@dot.cygnus.com> (raw)
In-Reply-To: <Pine.LNX.4.05.9811260929050.6450-100000@moshier.ne.mediaone.net>
On Thu, Nov 26, 1998 at 09:51:40AM -0500, Stephen L Moshier wrote:
> > I believe extensions to be a no-op.
>
> IEEE does not agree. The reason is that a format conversion is an
> "operation" which among other things means that the "exception" flags
> can change as a result. Suppose you have a value in single precision
> that is marked with the "inexact" flag. After extending to double it
> is no longer inexact, because IEEE 754 para 5.3 says "Conversion to a
> wider precision is exact." So to make IEEE happy your no-op would
> have to clear the inexact flag.
What? The accrued exception bits are just that -- accrued.
Only the user clears them. Ever.
Moreover, that "inexact" flag means that some _calculation_
was inexact. It says _nothing_ about whether the resulting
value is denormal or whatnot.
r~
next prev parent reply other threads:[~1998-11-27 8:53 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-11-09 14:50 Stephen L Moshier
1998-11-19 8:52 ` Jeffrey A Law
1998-11-20 5:20 ` Stephen L Moshier
1998-11-23 16:29 ` Jan Hubicka
1998-11-23 9:01 ` Jeffrey A Law
1998-11-26 0:40 ` Richard Henderson
1998-11-26 6:51 ` Stephen L Moshier
1998-11-26 8:04 ` Jan Hubicka
1998-11-26 17:08 ` Jeffrey A Law
1998-11-26 19:01 ` Stephen L Moshier
1998-11-27 8:53 ` Richard Henderson [this message]
1998-11-27 12:46 ` Jan Hubicka
1998-11-27 17:13 ` Stephen L Moshier
1998-11-27 12:46 ` Stephen L Moshier
[not found] <19981130114618.A1831@dot.cygnus.com>
1998-11-30 20:56 ` Stephen L Moshier
1998-11-30 23:25 ` Richard Henderson
1998-11-30 20:56 ` Stephen L Moshier
1998-11-30 23:25 ` Richard Henderson
1998-12-01 6:13 ` Stephen L Moshier
1998-12-01 12:51 ` Richard Henderson
1998-12-01 17:59 ` Stephen L Moshier
1998-12-01 17:59 ` Joern Rennecke
-- strict thread matches above, loose matches on Subject: below --
1998-11-19 19:37 N8TM
1998-11-20 8:14 ` Stephen L Moshier
1998-11-02 0:21 Marc Lehmann
1998-10-27 6:09 Jan Hubicka
1998-10-30 3:25 ` Jeffrey A Law
1998-10-31 2:52 ` Jan Hubicka
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