README.md

Linux-LLVM-LTO

example on gentoo linux

Install dracut:

emerge --ask sys-kernel/dracut

change directory to /usr/src/linux

cd /usr/src/linux

copy old config if available

sudo cp /usr/src/linux-6.4.4-gentoo/.config .config

sudo make oldconfig

Kernel configuration

General architecture-dependent options --->
    Link Time Optimization (LTO) (Clang ThinLTO (EXPERIMENTAL)) --->
        ( ) None
        ( ) Clang Full LTO (EXPERIMENTAL)
        (x) Clang ThinLTO (EXPERIMENTAL)

sudo make CC=clang LLVM=1 menuconfig

build Kernel

sudo make CC=clang \
    LD=ld.lld \
    AR=llvm-ar \
    NM=llvm-nm \
    STRIP=llvm-strip \
    OBJCOPY=llvm-objcopy \
    OBJDUMP=llvm-objdump \
    READELF=llvm-readelf \
    HOSTCC=clang \
    HOSTCXX=clang++ \
    HOSTAR=llvm-ar \
    HOSTLD=ld.lld \
    LLVM_IAS=1 \
    -j14 KCFLAGS="-O2 -march=native -pipe" \
    EXTRAVERSION=-gentoo-llvm-lto \
    all

install Kernel and Modules

sudo make modules_install

sudo make install

sudo cp arch/x86_64/boot/bzImage /boot/vmlinuz-6.9.11-gentoo-llvm-lto-x86_64

build initramfs

sudo dracut --hostonly "/boot/initramfs-$(make EXTRAVERSION=-gentoo-llvm-lto kernelrelease).img" \
    --kver "$(make EXTRAVERSION=-gentoo-llvm-lto kernelrelease)"

update Grub

sudo grub-mkconfig -o /boot/grub/grub.cfg