Re: git: 1cae7121c667 - main - Enable LLVM_BINUTILS by default

On Fri, 14 Mar 2025 at 14:05, Nuno Teixeira <eduardo@freebsd.org> wrote:
>
> Hello Ed,
>
> I have a newbie question about building world/kernel with LTO.
> I did not found too much info googling, but I found https://wiki.freebsd.org/LinkTimeOptimization and it says:
>
> Build and link a kernel with:
>
> WITHOUT_CTF=yes
> WITHOUT_DTRACE=yes
> sys/conf/kern.mk -flto=thin (for all clang invocations)
>
> Is this the correct way to test LTO atm?

That page is pretty much completely out of date, unfortunately.
Eventually we want to have user-facing knobs for this (for example,
WITH_KERNEL_LTO in src.conf) but for experimentation you need to add
-flto or -flto=thin to the compiler and linker invocations. This
should be possible by setting CFLAGS and LDFLAGS on the command line
or by editing kern.mk.