Re: No selection for "Architecture level and Tune for CPU" in menuconfig

["Yann E. MORIN" <yann dot morin dot 1998 at anciens dot enib dot fr>]

Henry, All,

On Sunday 22 May 2011 22:12:46 hong zhang wrote:
> make menuconfig does not have selection for "Architecture level and Tune
> for CPU". 

If by 'selection' you mean a 'choice menu, then, no there is no such
'selection'. You have to enter the appropriate values in the menu, as
you said below.

> I have to manually type to
>           o Set Architecture level to "armv7-a"
>           o Set Tune for CPU to "cortex-a9"
> 
> How do I know if it supports cortex-a8 or arm11 or any other option?

It all depends on the version off gcc you select.

> Any explanation?

Maintaining such a list for -march and -mcpu and -mtune and whatnot is just
impossible. With new versions of gcc come new values, some combinations that
were impossible are now possible, or the other way around, old combinations
are no longer valid.

Plus, we'd have to maintain such a list for all architectures, not only ARM,
which makes the job almost insanely complex.

Besides, for ARM, -mcpu and -mtune share the same list, but -march has
another set. for x86, -mcpu is deprecated in favor of -mtune, and -march
has the same set as -mtune. For MIPS, there's no -mcpu at all. And so on...

So, as explained in the help entries for Arch, CPU, Tune (and FPU, BTW):
  Pick a value from the gcc manual for your choosen gcc version and your
  target CPU.

So, yes, a bit of research is necessary before you can setup a toolchain.

And no, I will not take a patch that tries to add such a selection. Yes,
Alpha has such a selection, and yes, I'm gonna kill it very soon...

Regards,
Yann E. MORIN.

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