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Re: expand and truncate and 387
- To: Richard Henderson <rth at cygnus dot com>
- Subject: Re: expand and truncate and 387
- From: Stephen L Moshier <moshier at mediaone dot net>
- Date: Thu, 26 Nov 1998 09:51:40 -0500 (EST)
- cc: law at cygnus dot com, Jan Hubicka <hubicka at atrey dot karlin dot mff dot cuni dot cz>, egcs at cygnus dot com, Marc Lehmann <pcg at goof dot com>
- Reply-To: moshier at mediaone dot net
> 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.