Re:Re: [PATCH] abg-reader: optimize if construction

["Xiaole He" <hexiaole1994@126.com>]

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Thank you for reviewing.

















At 2022-10-17 22:14:35, "Dodji Seketeli" <dodji@seketeli.org> wrote:
>Hello Xiaole,
>
>Xiaole He via Libabigail <libabigail@sourceware.org> a écrit:
>
>> In 'build_enum_type_decl' function of 'src/abg-reader.cc', the
>> 'for loop' walk through all the child nodes of the '<enum-decl>' for
>> seeking '<underlying-type>' and '<enumerator>':
>>
>> /* original src/abg-reader.cc begin */
>> static enum_type_decl_sptr
>> build_enum_type_decl(read_context& ctxt,
>>              const xmlNodePtr node,
>>              bool add_to_current_scope)
>> {
>>   ...
>>   for (xmlNodePtr n = xmlFirstElementChild(node);
>>        n;
>>        n = xmlNextElementSibling(n))
>>     {
>>       if (xmlStrEqual(n->name, BAD_CAST("underlying-type")))
>>       {
>>          ...
>>       }
>>
>>       if (xmlStrEqual(n->name, BAD_CAST("enumerator")))
>>       {
>>          ...
>>       }
>>     }
>>   ...
>> }
>> /* original src/abg-reader.cc end */
>>
>> Here uses 2 separate 'if' statements for seeking, that is, for any
>> child node of the '<enum-decl>', there involves 2 'if' comparations.
>> Because the child node of the '<enum-decl>' is either
>> '<underlying-type>' or '<enumerator>', there would be a slight
>> optimization when use 'if-else if' construction instead, like below:
>>
>> /* optimized src/abg-reader.cc begin */
>> for (xmlNodePtr n = xmlFirstElementChild(node);
>>      n;
>>      n = xmlNextElementSibling(n))
>>   {
>>     if (xmlStrEqual(n->name, BAD_CAST("underlying-type")))
>>     {
>>        ...
>>     }
>>     else if (xmlStrEqual(n->name, BAD_CAST("enumerator")))
>>     {
>>        ...
>>     }
>>   }
>> /* optimized src/abg-reader.cc end */
>>
>> Supposing there has the test case:
>>
>> /* test case begin */
>> <abi-instr version='1.0'>
>>   <enum-decl name='E' filepath='../../abitests/test-enum0-v0.cc' line='1' column='6' id='type-id-2'>
>>     <underlying-type type-id='type-id-1'/>
>>     <enumerator name='e0' value='0'/>
>>     <enumerator name='e2' value='1'/>
>>   </enum-decl>
>> </abi-instr>
>> /* test case end */
>>
>> When parsing the '<underlying-type>' xml tag, for the original
>> 'src/abg-reader.cc', there involves 2 'if' comparations. But involves
>> only 1 'if' comparation for the optimized 'src/abg-reader.cc'.
>>
>> Signed-off-by: Xiaole He <hexiaole@kylinos.cn>
>> Tested-by: Xiaole He <hexiaole@kylinos.cn>
>
>Applied to the master branch.
>
>Cheers,
>
>-- 
>		Dodji