[Buildroot] generic code with i7 bootlin toolchain?

[Giulio Benetti]

Hi,

> Il giorno 3 nov 2021, alle ore 21:04, stsp <stsp2 at yandex.ru> ha scritto:
> 
> Hello.
> 
> I configured buildroot for
> corei7 CPU to use the bootlin
> tool-chain. As expected, nothing
> worked, as I have the (very old)
> AMD CPU.
> Then I did the following:
> BR2_TARGET_OPTIMIZATION="-march=x86-64 -mtune=generic"
> 
> make clean
> and full rebuild.
> After that I've got working
> kernel and the user-space
> starts booting, but still many
> user-space apps or libs crash
> with an illegal instruction exception.
> I even checked that the toolchain-wrapper
> generated by buildroot, has these
> strings embedded, so my change
> certainly had some effect. But
> it was not enough.
> 
> So it looks like the
> BR2_TARGET_OPTIMIZATION
> is somehow applied not to all
> built packages? Why can that be?

Unfortunately some package(I would say many) has theirself a broken way to correctly pass external C/CXX/LDFLAGS. 
Usually they internally override some flag that makes null what we pass or worse they completely ignore them by using hard coded flags.
To fix this specific problem we should go through every package and fix the package build system itself(a huge work).

> Is there any other way I can
> utilize bootlin tool-chain for some
> "generic" (non-SSE3/4) CPU?

Here I leave the answer to more experienced people.

Best regards
Giulio

> 
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