u/Brian_Littlewood

I've learned that this is a thing on Gentoo. If one wants to compile packages for other machine, one gets to make VMs and do it there through QEMU.

Isn't there less cluttered/insane way to do this ? Seems awfully wasteful, especially on arches that would have to be SW emulated, like compiling for RISC-V or Arm on x86 host.

GCC can do cross-compile as it is. Same with CLANG AFAIK.
So why not Portage ?

AFAIK gcc is far more aggressive with LTO than clang, which on kernel does only thinLTO (at least by default IIRC).

But while kernel has been adapted to allow LTO with clang, I can't find any recipe for gcc.

Besides that, even with thinLTO, clang kernel compile seems o take forever. Gcc LTO is slower, but not nearly as much.

Also, is there any way to compile kernel with BOLT optimizations ?
I've read that BOLT/Propeller do the same kind of optimizations that compiler does with PGO, only that they do it more aggressively(especially BOLT) and at the final linking stage, when they can apply them over thee final binary.

I've read that this brings measurable gains even on stuff like kernel, so why not ?
I assume this implies having to compile with PGO as a basis for BOLT/Propeller, so add that one to the list. How does one compile kernel with PGO and how does one profile such kernel ?

I'm looking at the latest versions:

• sys-kernel/linux-headers-6.19:0
• sys-kernel/gentoo-sources-7.0.5:7.0.5

What's the point of having current gentoo-sources if userland isnt't informed about its new functionalities through linux-headers ? gentoo-sources-7.0.x is out for quite some time now.

Also, why are linux-headres separate package ?
Isn't the kernel supposed to install and expose its own header files ?