public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/103393] [12 Regression] Generating 256bit register usage with -mprefer-avx128 -mprefer-vector-width=128
Date: Fri, 26 Nov 2021 11:37:13 +0000	[thread overview]
Message-ID: <bug-103393-4-ylaDUMS4S4@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103393-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103393

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Richard Earnshaw from comment #15)
> It seems perverse to me that you have a standard named pattern in the x86
> backend that is enabled, but then you somehow expect the generic parts of
> the compiler to know that it shouldn't be used.

They should be used, but only if the user code asks for it explicitly.
So, say a 32-byte generic vector in user code, or the <x86intrin.h> intrinsics
that need 32-byte vectors are just fine.
The option just asks that the compiler tries hard not to introduce those on its
own (e.g. vectorization but this string ops expansion is similar to that).

With those selected ISAs, such instructions are available, but on some CPUs use
of those is not really performance beneficial and using smaller vectors might
get better results.

  parent reply	other threads:[~2021-11-26 11:37 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-23 19:20 [Bug tree-optimization/103393] New: [ 12 Regression ] Auto vectorizer generating " jschoen4 at gmail dot com
2021-11-24  8:57 ` [Bug tree-optimization/103393] [12 Regression] Generating " rguenth at gcc dot gnu.org
2021-11-24 13:45 ` [Bug target/103393] " hjl.tools at gmail dot com
2021-11-24 13:53 ` rguenth at gcc dot gnu.org
2021-11-24 20:38 ` jschoen4 at gmail dot com
2021-11-25  1:15 ` crazylht at gmail dot com
2021-11-25  1:25 ` crazylht at gmail dot com
2021-11-25  7:16 ` rguenther at suse dot de
2021-11-25  7:28 ` [Bug middle-end/103393] " rguenth at gcc dot gnu.org
2021-11-25  7:40 ` rguenth at gcc dot gnu.org
2021-11-25 17:57 ` jakub at gcc dot gnu.org
2021-11-25 18:09 ` jakub at gcc dot gnu.org
2021-11-25 20:54 ` rearnsha at gcc dot gnu.org
2021-11-25 20:57 ` rearnsha at gcc dot gnu.org
2021-11-25 22:49 ` hjl.tools at gmail dot com
2021-11-26 11:31 ` rearnsha at gcc dot gnu.org
2021-11-26 11:37 ` jakub at gcc dot gnu.org [this message]
2021-11-26 11:44 ` rearnsha at gcc dot gnu.org
2021-11-26 11:48 ` jakub at gcc dot gnu.org
2021-11-26 11:51 ` rearnsha at gcc dot gnu.org
2021-11-26 11:58 ` jakub at gcc dot gnu.org
2021-11-26 12:26 ` rguenth at gcc dot gnu.org
2021-11-26 12:51 ` rearnsha at gcc dot gnu.org
2022-03-01 22:41 ` hjl.tools at gmail dot com
2022-03-02 14:52 ` hjl.tools at gmail dot com
2022-03-31  7:31 ` rguenth 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-103393-4-ylaDUMS4S4@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).