From: Richard Guenther <rguenther@suse.de>
To: Bernd Schmidt <bernds@codesourcery.com>
Cc: Jakub Jelinek <jakub@redhat.com>, gcc-patches@gcc.gnu.org
Subject: Re: RFC: Fix GCSE exp_equiv_p on MEMs with different MEM_ATTRS (PR rtl-optimization/49390)
Date: Tue, 14 Jun 2011 10:03:00 -0000 [thread overview]
Message-ID: <alpine.LNX.2.00.1106141146560.810@zhemvz.fhfr.qr> (raw)
In-Reply-To: <4DF72BC4.5050306@codesourcery.com>
On Tue, 14 Jun 2011, Bernd Schmidt wrote:
> On 06/14/2011 10:43 AM, Richard Guenther wrote:
> > The patch that reverted the MEM_ATTR comparison didn't come
> > with a single testcase (ugh, I realize I approved it though ;)).
>
> > Bernd, do you have any testcases?
>
> It was a missed-optimization problem, but I think it only showed up with
> a modified ARM backend, and it was a set of changes I threw away in the
> end since I found a better fix. So, from that angle no objections if
> it's reverted.
>
> Judging from the variable names the testcase was 253.perlbmk/op.c, but I
> can't make the problem reappear at the moment - quite possibly because
> I'm not fully remembering what I had changed in arm.c.
It's likely that due to MEM_REFs on the tree level we now detect more
cases there. Btw, if we'd re-arrange the code to use NULL MEM_ATTRS
for the canonical MEM whenever we see two non-equivalent MEM_ATTRS
it should work again (no need to compare MEM_ALIAS_SET either then).
Not sure where to do that check and MEM_ATTRS adjustment though
(probably at hashtable lookup time).
So I'd say we revert your patch for now and if somebody feels like
implementing the above ...
Richard.
next prev parent reply other threads:[~2011-06-14 9:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-13 18:57 Jakub Jelinek
2011-06-14 9:10 ` Richard Guenther
2011-06-14 9:40 ` Bernd Schmidt
2011-06-14 10:03 ` Richard Guenther [this message]
2011-06-14 15:32 ` Jakub Jelinek
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