Symbol Size Variance

[Gedare Bloom]

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.