Symbol Size Variance

[Sebastian Huber]

On 25/05/18 07:54, Sebastian Huber wrote:
> On 24/05/18 17:46, Gedare Bloom wrote:
>> On Thu, May 24, 2018 at 9:05 AM, Joel Sherrill <joel at rtems.org> wrote:
>>>
>>> On Thu, May 24, 2018, 8:04 AM Gedare Bloom <gedare at rtems.org> wrote:
>>>> On Wed, May 23, 2018 at 2:28 AM, Sebastian Huber
>>>> <sebastian.huber at embedded-brains.de> wrote:
>>>>> On 23/05/18 01:06, Joel Sherrill wrote:
>>>>>> Or we may need to limit ourselves to source line mapping on a per
>>>>>> executable
>>>>>> basis. And generate reports using gcov output if we see methods 
>>>>>> change
>>>>>> between executables. I have shied away from gcov as the primary 
>>>>>> format
>>>>>> because I don't see how to do subexpression analysis.
>>>>>>
>>>>>>    if (a == 0 || b == 1)
>>>>>>
>>>>>> That's one line of source but two sub-expressions. Unless it's 
>>>>>> changed
>>>>>> recently, the debug info is not at a level of granularity to 
>>>>>> generate
>>>>>> gcov data that can tell we always too the first sub-expression.
>>>>>>
>>>>>> I'm not arguing -- just saying that doing the analysis at the asm 
>>>>>> level
>>>>>> gives us branch information I don't think we get via source line
>>>>>> analysis and gcov.
>>>>>
>>>>> Is the --all-blocks option of gcov helpful here?
>>>>>
>>>>> https://gcc.gnu.org/onlinedocs/gcc/Invoking-Gcov.html#Invoking-Gcov
>>>>>
>>>> Yes, that seems like it should work to me.
>>>
>>> Can you decipher the gcov output to see if it is working?
>> Not immediately, but maybe you can put together a simple example of a
>> subexpr that is 'dead code' to test with/without the option.
>
> It seems that gcov already produces sub-expression branch counts 
> without the -a option: 

Actually, I think this is more a feature of the GCC -fprofile-arcs 
-ftest-coverage options.

-- 
Sebastian Huber, embedded brains GmbH

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