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Re: expand and truncate and 387
- To: moshier at mediaone dot net, Richard Henderson <rth at cygnus dot com>
- Subject: Re: expand and truncate and 387
- From: Richard Henderson <rth at cygnus dot com>
- Date: Mon, 30 Nov 1998 17:19:31 -0800
- Cc: Jan Hubicka <hubicka at atrey dot karlin dot mff dot cuni dot cz>, law at cygnus dot com, egcs at cygnus dot com, Marc Lehmann <pcg at goof dot com>
- References: <19981130114618.A1831@dot.cygnus.com> <Pine.LNX.4.05.9811301823340.6723-100000@moshier.ne.mediaone.net>
- Reply-To: Richard Henderson <rth at cygnus dot com>
On Mon, Nov 30, 1998 at 06:27:23PM -0500, Stephen L Moshier wrote:
> Look at Section 5, "Operations," and Secton 5.3, "Floating-Point Format
> Conversions."
Yes I see.
(1) Extension of normal values is exact, and does nothing since the
numbers are already in the right form. Likewise for infinities,
QNaN, and what would be a denormal in the source precision.
(2) The invalid operation exception for SNaN is signaled when the
value is loaded with `fld'. Therefore no additional signaling is
required when the value is already in a register.
Therefore extension in a register, on x86, is a no-op.
r~