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.
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