From: Christopher Li <sparse@chrisli.org>
To: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: "Jacek Śliwerski" <sliwers@googlemail.com>, linux-sparse@vger.kernel.org
Subject: Re: Defect in linearization of short circuit &&
Date: Wed, 17 Feb 2010 12:22:12 -0800 [thread overview]
Message-ID: <70318cbf1002171222p652692eerc3aa0f31f69dbe6b@mail.gmail.com> (raw)
In-Reply-To: <1266407258.11294.194.camel@thorin>
On Wed, Feb 17, 2010 at 3:47 AM, Bernd Petrovitsch
<bernd@petrovitsch.priv.at> wrote:
>>
>> But for this expression:
>>
>> a = st && st->foo && st->bar && i > 0;
>>
>> This optimization might be worth while.
> ACK. But this example has no side effect (assuming no preprocessor
> trickery, no "volatile" somewhere relevant, etc.) so it' not
> "dangerous".
> Above I was talking about the general case.
Then we are in agreement.
Sparse actually go the extra mile to make sure the expression is
safe. So whenever the expression has side effects or unsafe, it set the cost
of the expression prohibitively high.
E.g:
expand_dereference() return UNSAFE because the expression can segfault.
expand_call() return SIDE_EFFECT.
So if there is a bug cause the some unsafe optimization. We just just fix the
bug instead of disable the optimization.
It is harder to do this optimization in the linearized instructions because
the linearized instruction does not have the expression boundary any more.
Chris
prev parent reply other threads:[~2010-02-17 20:22 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-14 13:39 Defect in linearization of short circuit && Jacek Śliwerski
2010-02-14 21:04 ` Jacek Śliwerski
2010-02-14 23:09 ` Christopher Li
2010-02-15 19:12 ` Jacek Śliwerski
2010-02-15 19:41 ` Christopher Li
2010-02-15 20:18 ` Jacek Śliwerski
2010-02-15 21:11 ` Christopher Li
2010-02-16 9:28 ` Bernd Petrovitsch
2010-02-16 19:02 ` Christopher Li
2010-02-16 19:10 ` Christopher Li
2010-02-16 19:19 ` Jacek Śliwerski
2010-02-16 19:36 ` Christopher Li
2010-02-16 20:11 ` enum warning patch (was Re: Defect in linearization of short circuit &&) Kamil Dudka
2010-02-16 20:18 ` Kamil Dudka
2010-02-16 22:44 ` Christopher Li
2010-02-17 14:00 ` Kamil Dudka
2010-02-17 11:47 ` Defect in linearization of short circuit && Bernd Petrovitsch
2010-02-17 20:22 ` Christopher Li [this message]
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