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From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= <f4bug@amsat.org>
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Date: Thu, 11 May 2017 23:01:09 -0300
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Subject: Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to
 optimize tcg op using tcg_gen_extract()
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To: Markus Armbruster <armbru@redhat.com>
Cc: qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>, Richard Henderson <rth@twiddle.net>, Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>, Eric Blake <eblake@redhat.com>, Laurent Vivier <lvivier@redhat.com>, Michael Tokarev <mjt@tls.msk.ru>, Eduardo Habkost <ehabkost@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>Eric Blake <eblake@redhat.com>

Hi Markus,

On 05/11/2017 06:03 AM, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <f4bug@amsat.org> writes:
>
>> Ok I just understood Richard explanation, so this patch is WRONG and I
>> need to get some real rest :(
>
> Ha!  Get some sleep; we'll still be around in the morning ;)
>
>> On 05/10/2017 08:52 PM, Philippe Mathieu-Daudé wrote:
>>> Apply this script using:
>>>
>>> $ docker run -v `pwd`:`pwd` -w `pwd` petersenna/coccinelle \
>>>     --sp-file scripts/coccinelle/tcg_gen_extract.cocci \
>>>     --macro-file scripts/cocci-macro-file.h \
>>>     --dir target \
>>>     --in-place
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> ---
>>>
>>> This is a new version of the coccinelle script addressing Richard comments and
>>> trying to do it correctly. Also changed license to GPLv2+.
>>>
>>> The first rule matches, it calls a python2 script that basically checks the
>>> target_ulong is not overflowed: (msk << ofs) >> sizeof(target_ulong) == 0
>>
>> WRONG
> [...]
>
> Is this script likely to be rerun in the future?  If yes, keeping it in
> scripts/coccinelle/ is a good idea.  If no, I recommend to store it in
> the commit message instead.

It is unlikely to be rerun in the future, at least for this specific 
pattern. But it can be easily adapted for another TCG optimization.

I could not find much documentation about how to do a such script using 
Python, except on a thread [1]. If it is documented enough I think it is 
worth to keep it.

About putting it in each commit message, it is now 3 times bigger than 
the patch it generates!

Regards,

Phil.