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| author | Rong Xu <xur@google.com> | 2026-05-29 11:53:46 -0700 |
|---|---|---|
| committer | Nathan Chancellor <nathan@kernel.org> | 2026-05-29 13:44:29 -0700 |
| commit | 9f2aee8f7d1842be08da860e45265d30dba0d1f7 (patch) | |
| tree | e54014c8a7b6f38be666b6a3b4644c73ad5f99d2 /Makefile | |
| parent | 9c72d26e9fe3be79dd1d8a2ba00a033503ffd27d (diff) | |
| download | ath-9f2aee8f7d1842be08da860e45265d30dba0d1f7.tar.gz | |
kbuild: distributed build support for Clang ThinLTO
Add distributed ThinLTO build support for the Linux kernel.
This new mode offers several advantages: (1) Increased
flexibility in handling user-specified build options.
(2) Improved user-friendliness for developers. (3) Greater
convenience for integrating with objtool and livepatch.
Note that "distributed" in this context refers to a term
that differentiates in-process ThinLTO builds by invoking
backend compilation through the linker, not necessarily
building in distributed environments.
Distributed ThinLTO is enabled via the
`CONFIG_LTO_CLANG_THIN_DIST` Kconfig option. For example:
> make LLVM=1 defconfig
> scripts/config -e LTO_CLANG_THIN_DIST
> make LLVM=1 oldconfig
> make LLVM=1 vmlinux -j <..>
The build flow proceeds in four stages:
1. Perform FE compilation, mirroring the in-process ThinLTO mode.
2. Thin-link the generated IR files and object files.
3. Find all IR files and perform BE compilation, using the flags
stored in the .*.o.cmd files.
4. Link the BE results to generate the final vmlinux.o.
NOTE: This patch currently implements the build for the main kernel
image (vmlinux) only. Kernel module support is planned for a
subsequent patch.
Tested on the following arch: x86, arm64, loongarch, and
riscv.
The earlier implementation details can be found here:
https://discourse.llvm.org/t/rfc-distributed-thinlto-build-for-kernel/85934
Signed-off-by: Rong Xu <xur@google.com>
Co-developed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Piotr Gorski <piotrgorski@cachyos.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260529185347.2418373-4-xur@google.com
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/Makefile b/Makefile index 0fce9557a1157..857f08dcc9523 100644 --- a/Makefile +++ b/Makefile @@ -1071,11 +1071,16 @@ export CC_FLAGS_SCS endif ifdef CONFIG_LTO_CLANG -ifdef CONFIG_LTO_CLANG_THIN +ifdef CONFIG_LTO_CLANG_FULL +CC_FLAGS_LTO := -flto +else CC_FLAGS_LTO := -flto=thin -fsplit-lto-unit + +# These LLVM options were initially added with only in-process ThinLTO +# support, so avoid distributed ThinLTO support for now. +ifdef CONFIG_LTO_CLANG_THIN KBUILD_LDFLAGS += $(call ld-option,--lto-whole-program-visibility -mllvm -always-rename-promoted-locals=false) -else -CC_FLAGS_LTO := -flto +endif endif CC_FLAGS_LTO += -fvisibility=hidden @@ -1684,6 +1689,7 @@ endif # CONFIG_MODULES CLEAN_FILES += vmlinux.symvers modules-only.symvers \ modules.builtin modules.builtin.modinfo modules.nsdeps \ modules.builtin.ranges vmlinux.o.map vmlinux.unstripped \ + vmlinux.thinlto-index builtin.order \ compile_commands.json rust/test \ rust-project.json .vmlinux.objs .vmlinux.export.c \ .builtin-dtbs-list .builtin-dtbs.S @@ -2145,7 +2151,7 @@ clean: $(clean-dirs) $(call cmd,rmfiles) @find . $(RCS_FIND_IGNORE) \ \( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \ - -o -name '*.ko.*' \ + -o -name '*.ko.*' -o -name '*.o.thinlto.bc' \ -o -name '*.dtb' -o -name '*.dtbo' \ -o -name '*.dtb.S' -o -name '*.dtbo.S' \ -o -name '*.dt.yaml' -o -name 'dtbs-list' \ |