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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/19721] [meta-bug] optimizations that CSE still catches
Date: Wed, 02 Mar 2005 18:24:00 -0000 [thread overview]
Message-ID: <20050302182353.10217.qmail@sourceware.org> (raw)
In-Reply-To: <20050131123257.19721.steven@gcc.gnu.org>
------- Additional Comments From law at redhat dot com 2005-03-02 18:23 -------
Subject: Re: [meta-bug] optimizations that CSE still
catches
On Wed, 2005-03-02 at 11:50 +0000, steven at gcc dot gnu dot org wrote:
> ------- Additional Comments From steven at gcc dot gnu dot org 2005-03-02 11:50 -------
> Here is a nice one:
>
> Working on insn:
> (insn 215 214 216 15 (parallel [
> (set (reg:DI 176)
> (ashift:DI (reg:DI 175)
> (const_int 3 [0x3])))
> (clobber (reg:CC 17 flags))
> ]) -1 (nil)
> (expr_list:REG_EQUAL (mult:DI (reg:DI 174)
> (const_int 8 [0x8]))
> (nil)))
> Trying to fold rtx:
> (mult:DI (reg:DI 174)
> (const_int 8 [0x8]))
> Returning new rtx:
> (ashift:DI (reg:DI 174)
> (const_int 3 [0x3]))
>
> Sometimes I just hate REG_EQUAL notes...
Am I missing something here? I guess I'm not sure what point you're
trying to make.
It seems to me that (reg 174) must be equal to (reg 175) for the
REG_EQUAL note to be valid. Which means they must either be set
from equivalent expressions or we must have a copy insn between
them.
In the former case (set from equivalent expressions) we should
figure out why DOM or PRE didn't catch the redundancy.
In the latter case we'd want to see why we didn't copy propagate
the copy.
[ It's possible the copy occurs due to tree->rtl expansion -- there's
still a fair number of ways to get silly copies at that phase. In
which case we need to look into ways to eliminate the silly copies.
IIRC some come from lameness in the API for some of our conversion
routines. ]
jeff
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19721
next prev parent reply other threads:[~2005-03-02 18:24 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-31 12:33 [Bug middle-end/19721] New: " steven at gcc dot gnu dot org
2005-01-31 12:35 ` [Bug middle-end/19721] " steven at gcc dot gnu dot org
2005-01-31 12:39 ` steven at gcc dot gnu dot org
2005-01-31 12:40 ` kazu at cs dot umass dot edu
2005-01-31 12:43 ` steven at gcc dot gnu dot org
2005-01-31 12:44 ` steven at gcc dot gnu dot org
2005-01-31 15:15 ` pinskia at gcc dot gnu dot org
2005-01-31 15:24 ` dnovillo at gcc dot gnu dot org
2005-01-31 15:27 ` dnovillo at gcc dot gnu dot org
2005-01-31 20:14 ` stevenb at suse dot de
2005-01-31 21:36 ` law at redhat dot com
2005-02-02 9:22 ` stevenb at suse dot de
2005-02-02 11:51 ` hubicka at ucw dot cz
2005-02-06 17:41 ` steven@gcc.gnu.org
2005-02-14 0:21 ` kazu at cs dot umass dot edu
2005-02-22 6:13 ` kazu at cs dot umass dot edu
2005-02-22 7:29 ` kazu at cs dot umass dot edu
2005-02-25 22:40 ` kazu at cs dot umass dot edu
2005-03-02 11:50 ` steven at gcc dot gnu dot org
2005-03-02 18:24 ` law at redhat dot com [this message]
2005-03-05 10:40 ` stevenb at suse dot de
2005-03-06 0:33 ` steven at gcc dot gnu dot org
2005-03-06 5:59 ` law at redhat dot com
2005-03-06 9:31 ` stevenb at suse dot de
2005-03-06 19:57 ` law at redhat dot com
2005-03-06 22:14 ` steven at gcc dot gnu dot org
2005-03-11 5:04 ` phython at gcc dot gnu dot org
2005-03-11 19:43 ` amylaar at gcc dot gnu dot org
2005-03-11 19:59 ` pinskia at gcc dot gnu dot org
2005-03-16 14:53 ` kazu at cs dot umass dot edu
2005-03-17 8:22 ` aoliva at gcc dot gnu dot org
2005-04-13 18:11 ` pinskia at gcc dot gnu dot org
2005-04-13 18:15 ` pinskia at gcc dot gnu dot org
2005-04-16 15:15 ` steven at gcc dot gnu dot org
2005-04-26 17:35 ` bonzini at gcc dot gnu dot org
2005-05-06 14:02 ` pinskia at gcc dot gnu dot org
2005-07-19 14:13 ` falk at debian dot org
2005-08-17 8:04 ` bonzini at gcc dot gnu dot org
2005-08-17 19:42 ` law at redhat dot com
2005-08-17 20:18 ` paolo dot bonzini at lu dot unisi dot ch
2005-08-18 7:56 ` bonzini at gcc dot gnu dot org
2005-09-16 8:10 ` steven at gcc dot gnu dot org
2005-09-29 12:40 ` steven at gcc dot gnu dot org
[not found] <bug-19721-4@http.gcc.gnu.org/bugzilla/>
2013-05-09 0:32 ` amylaar at gcc dot gnu.org
2013-05-09 10:40 ` steven at gcc dot gnu.org
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