Re: [kbuild-all] mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'

From: Maciej W. Rozycki
Date: Thu Apr 21 2016 - 17:11:09 EST


On Thu, 21 Apr 2016, Ralf Baechle wrote:

> > I don't think it makes sense as the compiler won't support MIPSr6 code
> > anyway, so first it'll bail out on `-march=mips32r6', and if we go even
> > further and disable that too, then GAS will probably break somewhere on
> > inline asm and GCC will produce code which does not make sense otherwise.
>
> GCC 5.2.0 claims to support mips32r6 and mips64r6. It's just the option
> -mcompact-branches which seem to have been added later only.

Ah, I see -- I didn't track the timeline of support for this compiler's
option and I took it from an earlier response that the compiler does not
support R6 at all.

In that case however it looks to me like these `-mcompact-branches='
options (all the three we support) need to be wrapped into `$(call
cc-option,...)'. They do not affect any functionality and they are an
optimisation choice only anyway (and therefore I wonder why they've been
placed in arch/mips/Kconfig.debug rather than arch/mips/Kconfig).

Maciej