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Re: Bug with g77 and -mieee on Alpha Linux
Richard Henderson wrote:
> On Mon, Jul 12, 1999 at 06:04:04PM -0600, Donn Terry wrote:
> > Rounding mode only affects STORE operations.
> Toon was imprecise. We were not speaking of rounding
> (bits 10:11 of fpcr) but rather precision (bits 8:9 of fpcr).
Not surprising - I'm operating without the document defining ia32
floating point arithmetic. Richard, do you have an URL to it ? I
couldn't find it on Intel's Web site. Oops, I just realized - it's
probably in our Readings section ...
PS: Rounding mode is something different in IEEE-754 then what I was
referring to. It doesn't tell at what bit to round, but which method of
rounding you want: round to nearest, round to zero, round up or round
down.
> And in any case, rounding _does_ affect every operation.
> Just that in 64-bit precision mode, the rounding happens
> for the XFmode value of the register, rather than for the
> SFmode value of a variable.
As long as it's the same as that what happens when storing the SFmode
value in memory, we're safe (well, OK, modulo the range question).
Cheers,
--
Toon Moene (toon@moene.indiv.nluug.nl)
Saturnushof 14, 3738 XG Maartensdijk, The Netherlands
Phone: +31 346 214290; Fax: +31 346 214286
GNU Fortran: http://world.std.com/~burley/g77.html