clang: Enable LTO and lld based on distro knobs

Add to local.conf or distro config the following to enable lto flavors
and lld linker

DISTRO_FEATURES += "thin-lto"
DISTRO_FEATURES += "full-lto"
DISTRO_FEATURES += "lld"

Add lto.bbclass

To enable LTO is currently per recipe, or globally

to enable globally add following to global config meta-data e.g.
local.conf

INHRIT += "lto"

other-wise enable LTO per recipe using

inherit lto to recipe via bbappend or in main recipe

Signed-off-by: Khem Raj <raj.khem@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/classes/clang.bbclass b/classes/clang.bbclass
index 88dd893..2d08c10 100644
--- a/classes/clang.bbclass
+++ b/classes/clang.bbclass
@@ -18,6 +18,9 @@ TUNE_CCARGS_append_toolchain-clang = " -Wno-error=unused-command-line-argument -
 TOOLCHAIN_OPTIONS_append_toolchain-clang_class-nativesdk_x86-64 = " -Wl,-dynamic-linker,${base_libdir}/ld-linux-x86-64.so.2"
 TOOLCHAIN_OPTIONS_append_toolchain-clang_class-nativesdk_x86 = " -Wl,-dynamic-linker,${base_libdir}/ld-linux.so.2"
 
+# Enable lld globally"
+TOOLCHAIN_OPTIONS_append_toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'ld-is-lld', ' -fuse-ld=lld', '', d)}"
+
 # choose between 'gcc' 'clang' an empty '' can be used as well
 TOOLCHAIN ??= "gcc"