[Interest] Compiler optimisation flags on Android

[Thiago Macieira]

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.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center