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* [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield
@ 2004-10-16 3:04 kazu at cs dot umass dot edu
2004-10-16 3:11 ` [Bug middle-end/18030] " pinskia at gcc dot gnu dot org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: kazu at cs dot umass dot edu @ 2004-10-16 3:04 UTC (permalink / raw)
To: gcc-bugs
Consider:
struct B {
unsigned bit : 2;
};
void
plus (struct B *b)
{
b->bit |= 1;
}
./cc1 -O2 -fomit-frame-pointer -mregparm=3 generates
plus:
movb (%eax), %cl
andl $3, %ecx
orl $1, %ecx
andl $3, %ecx
movl (%eax), %edx
andl $-4, %edx
orl %ecx, %edx
movl %edx, (%eax)
ret
Note that we could just do "orl $1, (%eax)"
--
Summary: OR is inefficient in 2-bit bitfield
Product: gcc
Version: unknown
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P2
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: kazu at cs dot umass dot edu
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu @ 2004-10-16 3:11 ` pinskia at gcc dot gnu dot org 2004-10-16 15:49 ` kazu at cs dot umass dot edu ` (4 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-10-16 3:11 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-16 03:11 ------- For PPC: struct B { unsigned :30; unsigned bit : 2; }; Confirmed. -- What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed| |1 Last reconfirmed|0000-00-00 00:00:00 |2004-10-16 03:11:16 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu 2004-10-16 3:11 ` [Bug middle-end/18030] " pinskia at gcc dot gnu dot org @ 2004-10-16 15:49 ` kazu at cs dot umass dot edu 2004-10-17 11:26 ` giovannibajo at libero dot it ` (3 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: kazu at cs dot umass dot edu @ 2004-10-16 15:49 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From kazu at cs dot umass dot edu 2004-10-16 15:49 ------- A patch here: http://gcc.gnu.org/ml/gcc-patches/2004-10/msg01333.html -- What |Removed |Added ---------------------------------------------------------------------------- Keywords| |patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu 2004-10-16 3:11 ` [Bug middle-end/18030] " pinskia at gcc dot gnu dot org 2004-10-16 15:49 ` kazu at cs dot umass dot edu @ 2004-10-17 11:26 ` giovannibajo at libero dot it 2005-01-13 18:58 ` pinskia at gcc dot gnu dot org ` (2 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: giovannibajo at libero dot it @ 2004-10-17 11:26 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From giovannibajo at libero dot it 2004-10-17 11:26 ------- Approved for 4.1. -- What |Removed |Added ---------------------------------------------------------------------------- OtherBugsDependingO| |17652 nThis| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu ` (2 preceding siblings ...) 2004-10-17 11:26 ` giovannibajo at libero dot it @ 2005-01-13 18:58 ` pinskia at gcc dot gnu dot org 2005-03-02 16:05 ` cvs-commit at gcc dot gnu dot org 2005-03-02 16:08 ` kazu at cs dot umass dot edu 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-01-13 18:58 UTC (permalink / raw) To: gcc-bugs -- What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |4.1.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu ` (3 preceding siblings ...) 2005-01-13 18:58 ` pinskia at gcc dot gnu dot org @ 2005-03-02 16:05 ` cvs-commit at gcc dot gnu dot org 2005-03-02 16:08 ` kazu at cs dot umass dot edu 5 siblings, 0 replies; 7+ messages in thread From: cvs-commit at gcc dot gnu dot org @ 2005-03-02 16:05 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From cvs-commit at gcc dot gnu dot org 2005-03-02 16:05 ------- Subject: Bug 18030 CVSROOT: /cvs/gcc Module name: gcc Changes by: kazu@gcc.gnu.org 2005-03-02 16:05:00 Modified files: gcc : ChangeLog expr.c Log message: PR middle-end/18029 and PR middle-end/18030 * expr.c (optimize_bitfield_assignment_op): Add a special case to handle BIT_IOR_EXPR and BIT_XOR_EXPR. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.7632&r2=2.7633 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/expr.c.diff?cvsroot=gcc&r1=1.778&r2=1.779 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/18030] OR is inefficient in 2-bit bitfield 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu ` (4 preceding siblings ...) 2005-03-02 16:05 ` cvs-commit at gcc dot gnu dot org @ 2005-03-02 16:08 ` kazu at cs dot umass dot edu 5 siblings, 0 replies; 7+ messages in thread From: kazu at cs dot umass dot edu @ 2005-03-02 16:08 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From kazu at cs dot umass dot edu 2005-03-02 16:08 ------- Just checked in a patch. -- What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18030 ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2005-03-02 16:08 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2004-10-16 3:04 [Bug middle-end/18030] New: OR is inefficient in 2-bit bitfield kazu at cs dot umass dot edu 2004-10-16 3:11 ` [Bug middle-end/18030] " pinskia at gcc dot gnu dot org 2004-10-16 15:49 ` kazu at cs dot umass dot edu 2004-10-17 11:26 ` giovannibajo at libero dot it 2005-01-13 18:58 ` pinskia at gcc dot gnu dot org 2005-03-02 16:05 ` cvs-commit at gcc dot gnu dot org 2005-03-02 16:08 ` kazu at cs dot umass dot edu
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