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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/18041] OR of two single-bit bitfields is inefficient
Date: Fri, 06 May 2011 13:25:00 -0000 [thread overview]
Message-ID: <bug-18041-4-FqtYXQE2Cz@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-18041-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18041
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
AssignedTo|unassigned at gcc dot |rguenth at gcc dot gnu.org
|gnu.org |
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-06 13:23:11 UTC ---
Mine. With bitfield lowering I see
<bb 2>:
BF.0_2 = MEM[(struct B *)b_1(D)];
D.2686_3 = (<unnamed-unsigned:1>) BF.0_2;
D.2687_4 = (unsigned char) D.2686_3;
D.2694_6 = BF.0_2 >> 1;
D.2688_7 = (<unnamed-unsigned:1>) D.2694_6;
D.2689_8 = (unsigned char) D.2688_7;
D.2690_9 = D.2689_8 | D.2687_4;
D.2691_10 = (<unnamed-unsigned:1>) D.2690_9;
D.2696_12 = BF.0_2 & 4294967294;
D.2697_13 = (unsigned int) D.2691_10;
BF.2_14 = D.2697_13 | D.2696_12;
MEM[(struct B *)b_1(D)] = BF.2_14;
return;
there is the possibility to associate truncations/widenings with |& so
D.2689_8 | D.2687_4 becomes (unsigned char) D.2688_7 | D.2686_3
and the truncation (<unnamed-unsigned:1>) D.2690_9 can be combined
with it.
next parent reply other threads:[~2011-05-06 13:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-18041-4@http.gcc.gnu.org/bugzilla/>
2011-05-06 13:25 ` rguenth at gcc dot gnu.org [this message]
2011-05-10 11:48 ` rguenth at gcc dot gnu.org
2011-05-11 11:44 ` rguenth at gcc dot gnu.org
2004-10-17 16:36 [Bug middle-end/18041] New: " kazu at cs dot umass dot edu
2004-10-17 17:01 ` [Bug middle-end/18041] " pinskia at gcc dot gnu dot org
2004-10-17 17:05 ` pinskia at gcc dot gnu dot org
2005-02-07 19:21 ` pinskia at gcc dot gnu dot org
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