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 target/101579] Suboptimal codegen for __builtin_shufflevector
Date: Wed, 28 Jul 2021 09:49:38 +0000	[thread overview]
Message-ID: <bug-101579-4-S1CfXjaiby@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-101579-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101579

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Hongtao.liu from comment #4)
> I looks to me that middle end should be able to transform 64-byte vector
> shuffle to 32-byte vector shuffle when data flow analysis shows the upper
> part of the vector is never used.

That is not needed in this case.  The permutation is such that all indices for
the first half read from one half (in this case the first) and all indices for
the second half read from one half (in this case the first again), so it is
identical to a vector containing permutation of the first half with the first
half of the indices and permutation of the first half again with the second
half of the indices.

  parent reply	other threads:[~2021-07-28  9:49 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-22 12:41 [Bug target/101579] New: " hjl.tools at gmail dot com
2021-07-27 10:14 ` [Bug target/101579] " rguenth at gcc dot gnu.org
2021-07-27 10:35 ` jakub at gcc dot gnu.org
2021-07-28  9:01 ` crazylht at gmail dot com
2021-07-28  9:40 ` crazylht at gmail dot com
2021-07-28  9:45 ` crazylht at gmail dot com
2021-07-28  9:49 ` jakub at gcc dot gnu.org [this message]
2021-07-28 10:03 ` crazylht at gmail dot com
2021-07-28 10:12 ` crazylht at gmail dot com

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-101579-4-S1CfXjaiby@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).