public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108583] [13 Regression] wrong code with vector division by uint16 at -O2
Date: Tue, 31 Jan 2023 10:31:39 +0000	[thread overview]
Message-ID: <bug-108583-4-W9bpaBRqCn@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108583-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108583

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #7)
> (In reply to rsandifo@gcc.gnu.org from comment #6)
> > (In reply to Tamar Christina from comment #3)
> > > The vectorizer has this context but since we didn't want a new IFN the
> > > context should instead be derivable in
> > > targetm.vectorize.can_special_div_by_const hook.
> > I probably got lost in the threading, but could you point to where
> > the idea of using an ifn was rejected?  I know there was pushback
> > against hard-coding a specific constant, but that doesn't prevent
> > the use of ifns in itself.  (E.g. the gather/scatter IFNs have
> > constant arguments that are checked against what the target allows.)
> 
> https://patchwork.sourceware.org/project/gcc/patch/patch-15779-tamar@arm.com/
> #124788 is where the original patch used an IFN.
> https://patchwork.sourceware.org/project/gcc/patch/patch-15779-tamar@arm.com/
> #124863 where Richi wouldn't ACK a new optab as it didn't have a physical
> instruction backing it on any ISA, and in fairness, no one else did either
> effectively stranding the change.

Yep.  The other option would have to expose whatever special instruction
is used in the end as IFN and rewrite the division during vectorization
"properly", either via some pattern or via doing the expansion when
emitting the vectorized division instruction.

In hindsight that might have been the better option, but then ...

> https://patchwork.sourceware.org/project/gcc/patch/patch-15779-tamar@arm.com/
> #125144 where I pinged and got no response to the ping. After which I went
> on IRC and asked Richi how he'd like me to proceed.  In reply to this I was
> instructed he would like to proceed the same way vector permutes are
> currently handled with `can_perm` etc.  and that's where the patch thread
> picks off back on the ML.

... this looked simpler and also reasonable.  Only that it breaks now.

  parent reply	other threads:[~2023-01-31 10:31 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-28 14:00 [Bug rtl-optimization/108583] New: " zsojka at seznam dot cz
2023-01-30  4:19 ` [Bug target/108583] " pinskia at gcc dot gnu.org
2023-01-30  4:22 ` pinskia at gcc dot gnu.org
2023-01-30  8:31 ` rguenth at gcc dot gnu.org
2023-01-30 14:20 ` tnfchris at gcc dot gnu.org
2023-01-30 14:52 ` rguenther at suse dot de
2023-01-30 15:01 ` tnfchris at gcc dot gnu.org
2023-01-30 16:52 ` rsandifo at gcc dot gnu.org
2023-01-30 17:04 ` tnfchris at gcc dot gnu.org
2023-01-31 10:31 ` rguenth at gcc dot gnu.org [this message]
2023-01-31 11:01 ` rsandifo at gcc dot gnu.org
2023-01-31 11:39 ` tnfchris at gcc dot gnu.org
2023-01-31 11:44 ` rguenther at suse dot de
2023-01-31 11:58 ` tnfchris at gcc dot gnu.org
2023-01-31 12:03 ` rsandifo at gcc dot gnu.org
2023-01-31 12:19 ` rguenther at suse dot de
2023-01-31 13:35 ` tnfchris at gcc dot gnu.org
2023-01-31 14:33 ` rguenther at suse dot de
2023-01-31 14:45 ` rguenther at suse dot de
2023-01-31 15:01 ` tnfchris at gcc dot gnu.org
2023-02-01  7:29 ` rguenther at suse dot de
2023-02-01 16:22 ` tnfchris at gcc dot gnu.org
2023-02-02  8:03 ` tnfchris at gcc dot gnu.org
2023-02-02  8:50 ` rguenther at suse dot de
2023-02-02  8:55 ` tnfchris at gcc dot gnu.org
2023-02-08 13:57 ` tnfchris at gcc dot gnu.org
2023-02-09  7:41 ` rguenther at suse dot de
2023-03-12 18:43 ` cvs-commit at gcc dot gnu.org
2023-03-12 18:43 ` cvs-commit at gcc dot gnu.org
2023-03-12 18:43 ` cvs-commit at gcc dot gnu.org
2023-03-12 18:44 ` cvs-commit at gcc dot gnu.org
2023-03-12 18:44 ` cvs-commit at gcc dot gnu.org
2023-03-12 18:45 ` tnfchris at gcc dot gnu.org

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=bug-108583-4-W9bpaBRqCn@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /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).