[Interest] Compiler optimisation flags on Android

[maitai]

Interesting... Besides Android, is it worth considering -O3 for 
Linux/OS-X/Windows for a heavy-calculation application ?

Philippe Lelong

Le 03-05-2016 19:18, Thiago Macieira a écrit :
> On terça-feira, 3 de maio de 2016 18:14:11 PDT Nuno Santos wrote:
>> Because, from my experience with the code compiled for Intel, putting 
>> -O3
>> made a huge difference on the processing code of my audio app. But the 
>> same
>> might not be valid for arm. That’s why I’m asking.
> 
> -O3 not only enables all of -O2, but also enables optimisations that 
> increase
> code size considerably. One of them is -ftree-vectorize, which is one 
> of the
> reasons why your code and QtCore benefit a lot from it.
> 
> I have no clue whether GCC's -ftree-vectorize support on ARM is any 
> good. In
> any case, I doubt that you can count on Neon support on all those 
> Android
> devices anyway, so it's likely that the gain is minimal anyway.
> 
> PS: QtCore and QtGui are compiled with CONFIG += optimize_full, which 
> enables
> -O3.