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Subject: RE: [ping][patch] Fixed-point patch 2/10
Date: Mon, 06 Aug 2007 22:04:00 -0000
Message-ID: <3CB54817FDF733459B230DD27C690CEC03EE8EFF@Exchange.mips.com>
In-Reply-To: <46B77CD9.4070107@codesourcery.com>
From: "Fu, Chao-Ying" <fu@mips.com>
To: "Mark Mitchell" <mark@codesourcery.com>,         "Stephens, Nigel" <nigel@mips.com>
Cc: <gcc-patches@gcc.gnu.org>, "Thekkath, Radhika" <radhika@mips.com>
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Mark Mitchell wrote:
>=20
> Nigel Stephens wrote:
> >=20
> >=20
> > Mark Mitchell wrote:
> >> Fu, Chao-Ying wrote:
> >>
> >>=20=20
> >>> Ex 2: (A and B are negative. )
> >>> A.high =3D 0xffffffffffffffff and A.low =3D 0x8000000000000000
> >>> B.high =3D 0xffffffffffffffff and B.low =3D 0x0000000000000001
> >>> =3D> A > B, because A.high =3D=3D B.high and
> >>> (unsigned HOST_WIDE_INT) a.low > (unsigned HOST_WIDE_INT) b.low
> >>>=20=20=20=20=20
> >>
> >> Yes, I see; two's complement is set up so that after=20
> masking the sign
> >> bit, you can do an unsigned compare.  Thank you for explaining.
> >>=20=20=20
> >=20
> > Since double_int is already declared with low unsigned, like this:
> >=20
> >    typedef struct
> >    {
> >      unsigned HOST_WIDE_INT low;
> >      HOST_WIDE_INT high;
> >    } double_int;
> >=20
> >=20
> > Would it be more obvious to simply remove the casts altogether, e.g.
>=20
> There's a comment in double-int.h that suggests that the signedness of
> low/high is historical and subject to change.  So, I think=20
> the casts are
> OK -- but I think omitting them is also OK.  Chao-Ying, you may decide
> that as you please.
>=20
=20
  Ok. I will omit them.  Thanks!

Regards,
Chao-ying