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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/64541] FRE pass optimization failure
Date: Wed, 14 Jan 2015 12:00:00 -0000 [thread overview]
Message-ID: <bug-64541-4-JSzvcIXStS@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-64541-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64541
--- Comment #3 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 14 Jan 2015, skvadrik at gmail dot com wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64541
>
> --- Comment #2 from Ulya <skvadrik at gmail dot com> ---
> > we have to assume that p == q and thus the store to *q invalidates the previously load *p
>
> I see.
> It seemed to me from GIMPLE dumps that both cases are equally easy to optimize,
> perhaps I'm missing something.
1:
_6 = *p_2(D);
*q_7(D) = _6;
_9 = *q_7(D);
_10 = *_9;
it's easy to see that the load _9 = *q_7(D) results in _6.
2:
*p_2(D) = _4;
_6 = *p_2(D);
*q_7(D) = _6;
_9 = *p_2(D);
_10 = *_9;
not so much here for the load _9 = *p_2(D) as I explained
(the store *q_7(D) = _6 aliases it)
next prev parent reply other threads:[~2015-01-14 12:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-08 16:06 [Bug tree-optimization/64541] New: .fre1 " skvadrik at gmail dot com
2015-01-14 11:56 ` [Bug tree-optimization/64541] FRE " skvadrik at gmail dot com
2015-01-14 12:00 ` rguenther at suse dot de [this message]
2015-01-14 12:03 ` skvadrik at gmail dot com
2021-12-15 21:43 ` pinskia at gcc dot gnu.org
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