From: "William J. Schmidt" <wschmidt@linux.vnet.ibm.com>
To: Paolo Bonzini <bonzini@gnu.org>
Cc: gcc-patches@gcc.gnu.org, bergner@vnet.ibm.com, rguenth@gcc.gnu.org
Subject: Re: [PATCH] Fix PR46556 (poor address generation)
Date: Thu, 06 Oct 2011 13:23:00 -0000 [thread overview]
Message-ID: <1317906441.16896.16.camel@gnopaine> (raw)
In-Reply-To: <4E8D5D2A.1000208@gnu.org>
On Thu, 2011-10-06 at 09:47 +0200, Paolo Bonzini wrote:
> And IIUC the other address is based on pseudo 125 as well, but the
> combination is (plus (plus (reg 126) (reg 128)) (const_int X)) and
> cannot be represented on ppc. I think _this_ is the problem, so I'm
> afraid your patch could cause pessimizations on x86 for example. On
> x86, which has a cheap REG+REG+CONST addressing mode, it is much better
> to propagate pseudo 125 so that you can delete the set altogether.
>
> However, indeed there is no downstream pass that undoes the
> transformation. Perhaps we can do it in CSE, since this _is_ CSE after
> all. :) The attached untested (uncompiled) patch is an attempt.
>
> Paolo
Thanks, Paolo! This makes good sense. I will play with your (second :)
patch and let you know how it goes.
Bill
next prev parent reply other threads:[~2011-10-06 13:07 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-05 16:16 William J. Schmidt
2011-10-05 16:24 ` Paolo Bonzini
2011-10-05 16:28 ` Paolo Bonzini
2011-10-05 17:48 ` William J. Schmidt
2011-10-05 19:50 ` Paolo Bonzini
2011-10-05 21:04 ` William J. Schmidt
2011-10-06 8:57 ` Paolo Bonzini
2011-10-06 13:23 ` William J. Schmidt [this message]
2011-10-05 16:41 ` Steven Bosscher
2011-10-05 17:19 ` William J. Schmidt
2011-10-06 10:21 ` Richard Guenther
2011-10-06 13:49 ` William J. Schmidt
2011-10-06 14:24 ` Richard Guenther
2011-10-06 17:27 ` William J. Schmidt
2011-10-07 8:28 ` Richard Guenther
2011-10-07 9:45 ` Paolo Bonzini
2011-10-07 12:38 ` William J. Schmidt
2011-10-08 15:44 ` William J. Schmidt
2011-10-11 12:15 ` Richard Guenther
2011-10-11 13:57 ` Paolo Bonzini
2011-10-11 14:15 ` Paolo Bonzini
2011-10-11 14:58 ` William J. Schmidt
2011-10-11 15:33 ` William J. Schmidt
2011-10-18 14:43 ` William J. Schmidt
2011-10-21 9:53 ` Richard Guenther
2011-10-21 12:44 ` William J. Schmidt
2011-10-23 10:19 ` Richard Guenther
2011-10-24 14:10 ` William J. Schmidt
2011-10-30 18:44 ` [PING] " William J. Schmidt
2011-11-02 12:19 ` Richard Guenther
2011-11-02 12:31 ` William J. Schmidt
2011-11-02 14:26 ` Richard Guenther
2011-10-11 21:34 ` Ian Lance Taylor
2011-10-11 21:38 ` William J. Schmidt
2011-10-12 11:28 ` Richard Guenther
2011-10-13 7:08 ` Ian Lance Taylor
2011-10-06 17:47 ` Jeff Law
2011-10-06 18:04 ` William J. Schmidt
2011-10-06 18:15 ` Jeff Law
2011-10-07 8:53 ` Richard Guenther
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