From: "Amker.Cheng" <amker.cheng@gmail.com>
To: Miles Bader <miles@gnu.org>
Cc: Jeff Law <law@redhat.com>, Jeff Kenton <jkenton@tilera.com>,
Ian Lance Taylor <iant@google.com>,
David Brown <david@westcontrol.com>,
Georg-Johann Lay <avr@gjlay.de>,
gcc-help@gcc.gnu.org, charfiasma@yahoo.fr
Subject: Re: Tr : [redundency elimination, code motion, commun expression elimination] GCC optimizations
Date: Tue, 27 Sep 2011 16:47:00 -0000 [thread overview]
Message-ID: <CAHFci2_V5yiaVJj4jXP_N3xy0mHnWDH9ewY5J9_FVYqF25UT4Q@mail.gmail.com> (raw)
In-Reply-To: <buooby6h8l9.fsf@dhlpc061.dev.necel.com>
On Tue, Sep 27, 2011 at 1:12 PM, Miles Bader <miles@gnu.org> wrote:
> Miles Bader <miles@gnu.org> writes:
>>> Hmm, actually testing with a recent gcc snapshot, it _is_ merging the
>>> two if-blocks:
>> ...
>>
>> and in fact, gcc 4.4.6, 4.5.3, and 4.6.1 seem to do the same thing!
>>
>> So I dunno... what's the complaint again...?
>
> I note that this optimization only takes place at -O2 or above; maybe
> the original poster simply didn't use a high-enough optimization level?
>
> -miles
>
> --
> I'd rather be consing.
>
A case I ran into with gcc trunk after cprop1 pass:
cc <- compare(r684, 0)
if (cc != 0) goto .L1
r191 <- 0
goto .L2
.L1:
r191 <- 0
...other insns
.L2:
In my experiment, both following pre and cse passes do not hoist the
r191<-0 to the beginning.
I understand that it is actually not a redundant case, and not pre's job.
So which pass in gcc might handle it? Thanks very much.
Wondering is it a similar story to the original post?
--
Best Regards.
next prev parent reply other threads:[~2011-09-27 9:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1316712613.83211.YahooMailNeo@web28503.mail.ukl.yahoo.com>
2011-09-22 19:59 ` charfi asma
2011-09-22 20:51 ` Ian Lance Taylor
2011-09-23 7:04 ` David Brown
2011-09-23 8:47 ` Georg-Johann Lay
2011-09-23 9:13 ` David Brown
2011-09-23 15:16 ` David Brown
2011-09-23 15:53 ` Ian Lance Taylor
2011-09-23 16:05 ` Jeff Kenton
2011-09-23 19:03 ` Jeff Law
2011-09-27 7:18 ` Miles Bader
2011-09-27 9:35 ` Miles Bader
2011-09-27 11:29 ` Miles Bader
2011-09-27 16:47 ` Amker.Cheng [this message]
2011-09-27 23:42 ` Jeff Law
2011-09-28 0:03 ` Re : " charfi asma
2011-09-28 8:59 ` Miles Bader
2011-09-25 13:31 ` David Brown
2011-09-25 13:50 ` David Brown
2011-09-26 10:57 ` Re : " charfi asma
2011-09-26 15:35 ` Miles Bader
2011-09-26 22:47 ` Jeff Law
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