public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "ben at shellandslate dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/27212] vec_cmplt followed by a vec_all_ge, gives two vcmpgtuh instructions
Date: Wed, 19 Apr 2006 20:20:00 -0000	[thread overview]
Message-ID: <20060419202051.19274.qmail@sourceware.org> (raw)
In-Reply-To: <bug-27212-12549@http.gcc.gnu.org/bugzilla/>



------- Comment #3 from ben at shellandslate dot com  2006-04-19 20:20 -------
It's true that the instructions are not identical (the first sets the condition
register, the second doesn't.) But the second still duplicates work already
performed, and should be removed. (The two instructions are sometimes generated
in reverse order from similar source code, but the same principle applies.)
I've verified with assembly that removing the second instruction has no effect
on the program behavior, except to make it faster. :)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27212


  parent reply	other threads:[~2006-04-19 20:20 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-04-19  9:30 [Bug c++/27212] New: Altivec Comparison Peephole Bug ben at shellandslate dot com
2006-04-19 15:03 ` [Bug c++/27212] " pinskia at gcc dot gnu dot org
2006-04-19 16:50 ` [Bug target/27212] vec_cmplt followed by a vec_all_ge, gives two vcmpgtuh instructions pinskia at gcc dot gnu dot org
2006-04-19 20:20 ` ben at shellandslate dot com [this message]
2006-04-22 18:36 ` pinskia at gcc dot gnu dot org
2006-06-09  8:50 ` bonzini at gnu dot org
2009-02-24  9:01 ` bonzini at gnu dot 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=20060419202051.19274.qmail@sourceware.org \
    --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).