Re: gcc CXX_FLAGS

[gabx <arnaud dot gaboury at gmail dot com>]

On Wed, May 29, 2013 at 9:24 AM, Martin Guy-2 [via Sourceware.org] <
ml-node+s1504n233506h65@n7.nabble.com> wrote:

> On 28 May 2013 19:31, gabx <[hidden email]<http://user/SendEmail.jtp?type=node&node=233506&i=0>>
> wrote:
> > Thank you all for these details. It is my first deep journey in the
> > toolchain world, and as described on the ct-ng website, it can quickly
> > become a nightmare.
>
> Not a nightmare. It's just that compilers are complex. cross-compiler
> even more so.
>
> > I guess my CCX_FLAGS is then a non-sense :
>
> Not nonsense. You just have a super-fast cross-compiler that generates
> the same code as a regular one!
>
> > Which flags would you keep ?
> > My toolchain is aimed at building android kernel and rom for the Google
> LG
> > nexus 4.
>
> It depends what you are trying to achieve. If it's just a few % extra
> speed, try -Os or -O2/-O3. I think the manual says they optimise for
> minimum code size or maximum speed without/with large increases in
> compile time and code size, respectively.
> Beyond telling the compiler the instruction set it can use, which
> should correspond to the silicon in your target device, there is only
> a few % speed to be had by juggling with magic options, and which help
> and which make it worse or produce non-working code depend on the
> specific program you are compiling.
>
>     M
>
>
>
Thank you Martin.

The unique goal of this toolchain is to build android kernel and rom with
gcc 4.8 and some optimization flags for the Google LG nexus 4 (armv7-a
rev2)




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