This patch cleans up a few places in the Makefile to make way for landing LLD support in the kernel. There are still a few arch specific fixes that need to get upstreamed, but this core set of patches should be arch independent. Some very rough numbers: LLD is improving the overall build time of Google Pixel kernels by about 9%. The build is mostly dominated by compilation, but LLD is able to shave off quite a bit of time. One of the included patches helps get LLD linked kernels to competitive binary size, but there still some bugs in LLD causing it not to discard certain sections. Once that's fixed, I estimate an LLD linked kernel to be just barely smaller than a BFD linked kernel (less than 1%). Folks looking to test should use LLD built from source, as I recently fixed a bug in LLD that prevented LLD linked kernel modules from being loadable. $ make LD=ld.lld Nick Desaulniers (4): init/Kconfig: add config support for detecting linker Makefile: clang: choose GCC_TOOLCHAIN_DIR not on LD Makefile: lld: tell clang to use lld Makefile: lld: set -O2 linker flag when linking with LLD Changes since v1: * collect reviewed-by, sugguested-by, tested-by tags. * move where -fuse-ld=lld is added to CFLAGS. Makefile | 9 ++++++++- init/Kconfig | 9 +++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) -- 2.20.1.791.gb4d0f1c61a-goog
