From: Andrew Waterman <andrew@sifive.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Aldy Hernandez <aldyh@redhat.com>,
GCC patches <gcc-patches@gcc.gnu.org>,
Andrew MacLeod <amacleod@redhat.com>
Subject: Re: [PATCH] [PR24021] Implement PLUS_EXPR range-op entry for floats.
Date: Tue, 8 Nov 2022 10:17:40 -0800 [thread overview]
Message-ID: <CA++6G0DY6fmPqWgYxe9zhZttiCjF9VpbmSZqT4SF74j1JJnPZQ@mail.gmail.com> (raw)
In-Reply-To: <Y2qb2H3QPYuULPqb@tucnak>
On Tue, Nov 8, 2022 at 10:11 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Tue, Nov 08, 2022 at 09:44:40AM -0800, Andrew Waterman wrote:
> > On Tue, Nov 8, 2022 at 3:20 AM Jakub Jelinek via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > On Mon, Nov 07, 2022 at 04:41:23PM +0100, Aldy Hernandez wrote:
> > > > As suggested upthread, I have also adjusted update_nan_sign() to drop
> > > > the NAN sign to VARYING if both operands are NAN. As an optimization
> > > > I keep the sign if both operands are NAN and have the same sign.
> > >
> > > For NaNs this still relies on something IEEE754 doesn't guarantee,
> > > as I cited, after a binary operation the sign bit of the NaN is
> > > unspecified, whether there is one NaN operand or two.
> > > It might be that all CPUs handle it the way you've implemented
> > > (that for one NaN operand the sign of NaN result will be the same
> > > as that NaN operand and for two it will be the sign of one of the two
> > > NaNs operands, never something else), but I think we'd need to check
> > > more than one implementation for that (I've only tried x86_64 and thus
> > > SSE behavior in it), so one would need to test i387 long double behavior
> > > too, ARM/AArch64, PowerPC, s390{,x}, RISCV, ...
> > > The guarantee given by IEEE754 is only for those copy, negate, abs, copySign
> > > operations, so copying values around, NEG_EXPR, ABS_EXPR, __builtin_fabs*,
> > > __builtin_copysign*.
> >
> > FWIW, RISC-V canonicalizes NaNs by clearing the sign bit; the signs of
> > the input NaNs do not factor in.
>
> Just for binary operations and some unary, or also the ones that
> IEEE754 spells out (moves, negations, absolute value and copysign)?
I should've been more specific in my earlier email: I was referring to
the arithmetic operators. Copysign and friends do not canonicalize
NaNs.
>
> Jakub
>
prev parent reply other threads:[~2022-11-08 18:17 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 12:36 Aldy Hernandez
2022-10-13 13:02 ` Toon Moene
2022-10-13 13:44 ` Aldy Hernandez
2022-10-13 13:52 ` Toon Moene
2022-10-14 8:04 ` Aldy Hernandez
2022-10-13 17:57 ` Jakub Jelinek
2022-10-17 6:21 ` Aldy Hernandez
2022-10-24 6:04 ` Aldy Hernandez
2022-10-29 4:55 ` Jeff Law
2022-10-31 8:42 ` Aldy Hernandez
2022-11-04 13:16 ` Jakub Jelinek
2022-11-04 19:14 ` Jakub Jelinek
2022-11-04 19:53 ` Jakub Jelinek
2022-11-07 12:35 ` Aldy Hernandez
2022-11-07 12:43 ` Jakub Jelinek
2022-11-07 12:48 ` Aldy Hernandez
2022-11-07 12:56 ` Jakub Jelinek
2022-11-07 15:38 ` Aldy Hernandez
2022-11-08 11:07 ` Jakub Jelinek
2022-11-08 12:47 ` Aldy Hernandez
2022-11-08 13:15 ` Jakub Jelinek
2022-11-08 14:02 ` Aldy Hernandez
2022-11-08 14:03 ` Jakub Jelinek
2022-11-07 15:41 ` Aldy Hernandez
2022-11-08 11:20 ` Jakub Jelinek
2022-11-08 13:06 ` Aldy Hernandez
2022-11-08 13:24 ` Jakub Jelinek
2022-11-08 13:47 ` Aldy Hernandez
2022-11-08 13:50 ` Jakub Jelinek
2022-11-08 14:06 ` Aldy Hernandez
2022-11-08 14:11 ` Jakub Jelinek
2022-11-08 14:14 ` Aldy Hernandez
2022-11-08 23:05 ` Aldy Hernandez
2022-11-09 6:59 ` Aldy Hernandez
2022-11-08 17:44 ` Andrew Waterman
2022-11-08 18:11 ` Jakub Jelinek
2022-11-08 18:17 ` Andrew Waterman [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CA++6G0DY6fmPqWgYxe9zhZttiCjF9VpbmSZqT4SF74j1JJnPZQ@mail.gmail.com \
--to=andrew@sifive.com \
--cc=aldyh@redhat.com \
--cc=amacleod@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jakub@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).