public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/35292] Missing Const Prop -- union fields
Date: Sat, 23 May 2009 09:23:00 -0000	[thread overview]
Message-ID: <20090523092315.4177.qmail@sourceware.org> (raw)
In-Reply-To: <bug-35292-9436@http.gcc.gnu.org/bugzilla/>



------- Comment #5 from rguenth at gcc dot gnu dot org  2009-05-23 09:23 -------
Hm, with my fix for PR36327 there is now a natural place to do this in SCCVN.
The question is how to properly get to the desired value.  We have (bit
access ranges):

 c.[0..31] = 20;

 ... = c.[0..7];
 ... = c.[8..15];

(or others depending on byte-order).  Ideally we can translate this by
using a BIT_FIELD_REF on the value stored - at least if both stored value
and read value are integral types.  For other type mixes proper
VIEW_CONVERT_EXPRs need to be done.  The question is if it is worth it
for non-constants.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35292


  parent reply	other threads:[~2009-05-23  9:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-22  6:53 [Bug middle-end/35292] New: " xinliangli at gmail dot com
2008-02-22 10:47 ` [Bug middle-end/35292] " rguenth at gcc dot gnu dot org
2008-02-23  5:50 ` pinskia at gcc dot gnu dot org
2008-02-24 21:15 ` rguenther at suse dot de
2009-01-01 21:49 ` [Bug tree-optimization/35292] " pinskia at gcc dot gnu dot org
2009-05-23  9:23 ` rguenth at gcc dot gnu dot org [this message]
     [not found] <bug-35292-4@http.gcc.gnu.org/bugzilla/>
2012-07-05 14:05 ` 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=20090523092315.4177.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).