public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113326] Optimize vector shift with constant delta on shifting-count operand
Date: Thu, 11 Jan 2024 08:10:36 +0000	[thread overview]
Message-ID: <bug-113326-4-NsHTzXLEuc@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-113326-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113326

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
One more thing:
```
 vect_shift_0 = vect_value >> { 0, 1, 2, 3 };
 vect_shift_1 = vect_value >> { 4, 5, 6, 7 };
 vect_shift_2 = vect_value >> { 8, 9, 10, 11 };
 vect_shift_3 = vect_value >> { 12, 13, 14, 15 };
```
vs
```
 vect_shift_0 = vect_value >> { 0, 1, 2, 3 };
 vect_shift_1 = vect_shift_0 >> { 4, 4, 4, 4 };
 vect_shift_2 = vect_shift_0 >> { 8, 8, 8, 8 };
 vect_shift_3 = vect_shift_0 >> { 12, 12, 12, 12 };
```

the first has fully independent operations while in the second case, there is
one dependent and the are independent operations.

On cores which has many vector units the first one might be faster than the
second one.  So this needs a cost model too.

  parent reply	other threads:[~2024-01-11  8:10 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-11  7:13 [Bug tree-optimization/113326] New: " fxue at os dot amperecomputing.com
2024-01-11  7:30 ` [Bug target/113326] " pinskia at gcc dot gnu.org
2024-01-11  7:44 ` pinskia at gcc dot gnu.org
2024-01-11  7:52 ` fxue at os dot amperecomputing.com
2024-01-11  7:56 ` pinskia at gcc dot gnu.org
2024-01-11  8:10 ` pinskia at gcc dot gnu.org [this message]
2024-01-11  9:13 ` rguenth at gcc dot gnu.org
2024-01-11  9:58 ` fxue at os dot amperecomputing.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-113326-4-NsHTzXLEuc@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).