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Re: Patch: Add BID decimal floating point format
- From: Janis Johnson <janis187 at us dot ibm dot com>
- To: "Meissner, Michael" <michael dot meissner at amd dot com>
- Cc: Florian Weimer <fw at deneb dot enyo dot de>, gcc-patches at gcc dot gnu dot org, "Harle, Christophe" <christophe dot harle at amd dot com>, "H. J. Lu" <hjl at lucon dot org>, bje at au1 dot ibm dot com, Janis Johnson <janis187 at us dot ibm dot com>
- Date: Thu, 1 Mar 2007 09:55:04 -0800
- Subject: Re: Patch: Add BID decimal floating point format
- References: <87y7mjwb4y.fsf@mid.deneb.enyo.de> <6096959DEF5C9447A6BF80BDC7EB9EDC06155C3F@SBOSEXMB1.amd.com>
On Wed, Feb 28, 2007 at 05:15:51PM -0500, Meissner, Michael wrote:
> > -----Original Message-----
> > From: Florian Weimer [mailto:fw@deneb.enyo.de]
> > Sent: Tuesday, February 27, 2007 4:20 PM
> > To: Meissner, Michael
> > Cc: gcc-patches@gcc.gnu.org; Harle, Christophe; H. J. Lu;
> bje@au1.ibm.com;
> > Janis Johnson
> > Subject: Re: Patch: Add BID decimal floating point format
> >
> > * Michael Meissner:
> >
> > > Are there any objections or comments to patch?
> >
> > @item --enable-decimal-float
> > +@itemx --enable-decimal-float=yes
> > +@itemx --enable-decimal-float=no
> > +@itemx --enable-decimal-float=bid
> > +@itemx --enable-decimal-float=dpd
> > @itemx --disable-decimal-float
> > Enable (or disable) support for the C decimal floating point
> > -extension. This is enabled by default only on PowerPC GNU/Linux
> > -systems. Other systems may also support it, but require the user to
> > -specifically enable it.
> > +extension. This is enabled by default only on PowerPC, i386, and
> > +x86_64 GNU/Linux systems. Other systems may also support it, but
> > +require the user to specifically enable it. You can optionally
> > +control which decimal floating point format is used (either @var{bid}
> > +or @var{dpd}). The @var{bid} format is default on i386 and x86_64
> > +systems, and the @var{dpd} format is default on PowerPC systems.
> >
> > @samp{bid} and @samp{dpd} instead of @var{bid} and @var{dpd} (@var{}
> > is intended for metasyntactic variables only and is rendered in
> > CAPITAL LETTERS in plain text).
> >
> > Are DPD and BID universal terms? If not, it might make sense to
> > reference a definition (or provide one).
> >
>
> I'm attaching my rework of the documentation file.
The support in GCC is based on ISO/EIC WDTR 24732, which in turn is
based on IEEE 754r.
It doesn't make sense to enable decimal-float for targets other than
the ones mentioned because it requires support in the back end.
We shouldn't enable support by default because decNumber code in GCC
is currently covered by the GPL, not GPL plus exception, as described
in PR other/28002.
Janis