[FFmpeg-soc] [soc]: r5419 - als/alsdec.c

[Thilo Borgmann]

Michael Niedermayer schrieb:
> On Thu, Oct 22, 2009 at 01:32:15PM +0200, Thilo Borgmann wrote:
>> Michael Niedermayer schrieb:
>>> On Thu, Oct 22, 2009 at 11:29:55AM +0200, Thilo Borgmann wrote:
>>>> Thilo Borgmann schrieb:
>>>>> Michael Niedermayer schrieb:
>>>>>> On Wed, Oct 21, 2009 at 12:33:21PM +0200, Thilo Borgmann wrote:
>>>>>>> Michael Niedermayer schrieb:
>>>>>>>> On Tue, Oct 20, 2009 at 03:00:40PM +0200, thilo.borgmann wrote:
>>>>>>>>> Author: thilo.borgmann
>>>>>>>>> Date: Tue Oct 20 15:00:40 2009
>>>>>>>>> New Revision: 5419
>>>>>>>>>
>>>>>>>>> Log:
>>>>>>>>> Splits reading of block data and decoding of block data.
>>>>>>>>> Introduces ALSBlockData struct.
>>>>>>>> You are missing the "why" part, that should be explained in the commit
>>>>>>>> message
>>>>>>> Yes, sorry.
>>>>>>>
>>>>>>>> also this needs a benchmark as there are many additional dereferences
>>>>>>>> added
>>>>>>> It is a necessary evil to support MCC. If it would be faster the "old"
>>>>>>> way for non-MCC files, would this reason to have both, a split read &
>>>>>>> decode function pair and an all-in-one function?
>>>>>> I think a benchmark is usefull to judge if we should spend time thinking
>>>>>> about alternatives to the many dereferences or not
>>> [...]
>>>>> This is a 30% difference which makes me think to try these alternatives.
>>>>>
>>>>> What comes into my mind would be to use local copies, thus dereferencing
>>>>> the field of *bd just twice. One at the top and one at the bottom of the
>>>>> function.
>>>>>
>>>> I tested using local copies instead of dereferencing:
>>> [...]
>>>> That's a 4% gain so I think local copies don't pay off...
>>>>
>>>> Other alternatives?
>>> i would first confirm that gcc did not do something stupid about inlining.
>>> Or more precissely not inlining some random unrelated function after the
>>> file got bigger ...
>> How to do that?
> 
> nm -S foobar.o
> will show you things that are not inlined and how large they are

The BSD version does not have the option to show the size instead of the
'value'...


> 
> you can also use gcc to compile code to .s files and use grep on them

... so this seems to be necessary. What am I grepping for?

-Thilo