From: Denis Efremov <efremov@linux.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: Re: [Cocci] [PATCH] coccinelle: misc: add swap script
Date: Thu, 18 Feb 2021 14:34:04 +0300 [thread overview]
Message-ID: <afd7f80a-90c9-9d05-cc78-aacc5495174b@linux.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2102181227230.2748@hadrien>
On 2/18/21 2:29 PM, Julia Lawall wrote:
>
>
> On Thu, 18 Feb 2021, Denis Efremov wrote:
>
>>
>>
>> On 2/18/21 1:17 PM, Julia Lawall wrote:
>>>
>>>
>>> On Thu, 18 Feb 2021, Denis Efremov wrote:
>>>
>>>>
>>>>
>>>> On 2/18/21 12:31 AM, Julia Lawall wrote:
>>>>>> +@depends on patch@
>>>>>> +identifier tmp;
>>>>>> +expression a, b;
>>>>>> +type T;
>>>>>> +@@
>>>>>> +
>>>>>> +(
>>>>>> +- T tmp;
>>>>>> +|
>>>>>> +- T tmp = 0;
>>>>>> +|
>>>>>> +- T *tmp = NULL;
>>>>>> +)
>>>>>> +... when != tmp
>>>>>> +- tmp = a;
>>>>>> +- a = b;
>>>>>> +- b = tmp;
>>>>>> ++ swap(a, b);
>>>>>> +... when != tmp
>>>>>
>>>>> In this rule and the next one, if you remove the final ; from the b = tmp
>>>>> line and from the swap line, and put it into context code afterwards, them
>>>>> the generated code looks better on cases like fs/xfs/xfs_inode.c in the
>>>>> function xfs_lock_two_inodes where two successive swap calls are
>>>>> generated.
>>>>>
>>>>> There are also some cases such as drivers/net/wireless/ath/ath5k/phy.c in
>>>>> the function ath5k_hw_get_median_noise_floor where the swap code makes up
>>>>> a whole if branch.
>>>>
>>>>> In this cases it would be good to remove the {}.
>>>>
>>>> How this can be handled?
>>>>
>>>> If I use this pattern:
>>>> @depends on patch@
>>>> identifier tmp;
>>>> expression a, b;
>>>> @@
>>>>
>>>> (
>>>> if (...)
>>>> - {
>>>> - tmp = a;
>>>> - a = b;
>>>> - b = tmp
>>>> + swap(a, b)
>>>> ;
>>>> - }
>>>> |
>>>> - tmp = a;
>>>> - a = b;
>>>> - b = tmp
>>>> + swap(a, b)
>>>> ;
>>>> )
>>>>
>>>> The tool fails with error:
>>>>
>>>> EXN: Failure("rule starting on line 58: already tagged token:\nC code
>>>> context\nFile \"drivers/net/wireless/ath/ath5k/phy.c\", line 1574,
>>>> column 4, charpos = 41650\n around = 'sort',\n whole content =
>>>> \t\t\t\tsort[j - 1] = tmp;") in drivers/net/wireless/ath/ath5k/phy.c
>>>
>>> A disjunction basically says "at this node in the cfg, can I match the
>>> first patter, or can I match the second pattern, etc." Unfortunately in
>>> this case the two branches start matching at different nodes, so the short
>>> circuit aspect of a disjunction isn't used, and it matches both patterns.
>>>
>>> The solution is to just make two rules. The first for the if case and the
>>> second for everything else.
>>>
>>
>> if (...)
>> - {
>> - tmp = a;
>> - a = b;
>> - b = tmp
>> + swap(a, b)
>> ;
>> - }
>>
>>
>> This produces "single-line ifs".
>> Maybe generated patches can be improved somehow?
>> Moving -+; doesn't help in this case.
>
> There is clearly some problem with the management of newlines...
>
> The other alternative is to just have one rule for introducing swap and
> another for removing the braces around a swap, ie
>
> if (...)
> - {
> swap(...);
> - }
>
> I don't think it would be motivated to remove the newline in that case.
Yes, this works. I'll send v2.
Thanks
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next prev parent reply other threads:[~2021-02-18 11:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-16 8:01 [Cocci] [PATCH] coccinelle: misc: add swap script Denis Efremov
2021-02-16 18:05 ` Markus Elfring
2021-02-17 21:31 ` Julia Lawall
2021-02-18 6:13 ` Denis Efremov
2021-02-18 10:17 ` Julia Lawall
2021-02-18 11:03 ` Denis Efremov
2021-02-18 11:29 ` Julia Lawall
2021-02-18 11:34 ` Denis Efremov [this message]
[not found] ` <50eb8319-a552-c749-6143-7e24a8778a04@web.de>
2021-02-18 20:03 ` Julia Lawall
2021-02-19 9:05 ` [Cocci] [PATCH v2] coccinelle: misc: add minmax script Denis Efremov
2021-02-19 9:07 ` Denis Efremov
2021-02-19 9:24 ` [Cocci] [PATCH v2] coccinelle: misc: add swap script Denis Efremov
2021-03-03 16:37 ` Julia Lawall
2021-03-05 10:09 ` [Cocci] [PATCH v3] " Denis Efremov
[not found] ` <afb06bbc-5c28-8a92-f205-c9a1c87c707c@linux.com>
2021-04-04 12:33 ` Julia Lawall
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