We get constant feedback that the command line invocation of make is too long. CROSS_COMPILE is helpful when a toolchain has a prefix of the target triple, or is an absolute path outside of $PATH, but it's mostly redundant for a given SRCARCH. SRCARCH itself is derived from ARCH (normalized for a few different targets). If CROSS_COMPILE is not set, simply set --target= for CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS based on $SRCARCH. Previously, we'd cross compile via: $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make LLVM=1 LLVM_IAS=1 Now: $ ARCH=arm64 make LLVM=1 LLVM_IAS=1 For native builds (not involving cross compilation) we now explicitly specify a target triple rather than rely on the implicit host triple. Link: https://github.com/ClangBuiltLinux/linux/issues/1399 Suggested-by: Arnd Bergmann <arnd@xxxxxxxxxx> Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx> Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> --- Changes v2 -> v3: * Drop check/requirement for LLVM=1, as per Masahiro. * Change oneliner from LLVM=1 LLVM_IAS=1 to CC=clang LLVM_IAS=1. * Don't carry forward Nathan's RB/TB tags. :( Sorry Nathan, but thank you for testing+reviewing v2. * Update wording of docs slightly. Changes v1 -> v2: * Fix typos in commit message as per Geert and Masahiro. * Use SRCARCH instead of ARCH, simplifying x86 handling, as per Masahiro. Add his sugguested by tag. * change commit oneline from 'drop' to 'infer.' * Add detail about explicit host --target and relationship of ARCH to SRCARCH, as per Masahiro. Changes RFC -> v1: * Rebase onto linux-kbuild/for-next * Keep full target triples since missing the gnueabi suffix messes up 32b ARM. Drop Fangrui's sugguested by tag. Update commit message to drop references to arm64. * Flush out TODOS. * Add note about -EL/-EB, -m32/-m64. * Add note to Documentation/. Documentation/kbuild/llvm.rst | 6 ++++++ scripts/Makefile.clang | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index b18401d2ba82..aef1587fc09b 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -46,6 +46,12 @@ example: :: clang --target=aarch64-linux-gnu foo.c +When both ``CC=clang`` (set via ``LLVM=1``) and ``LLVM_IAS=1`` are used, +``CROSS_COMPILE`` becomes unnecessary and can be inferred from ``ARCH``. +Example: :: + + ARCH=arm64 make LLVM=1 LLVM_IAS=1 + LLVM Utilities -------------- diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang index 297932e973d4..a1b46811bdc6 100644 --- a/scripts/Makefile.clang +++ b/scripts/Makefile.clang @@ -1,6 +1,34 @@ -ifneq ($(CROSS_COMPILE),) +# Individual arch/{arch}/Makfiles should use -EL/-EB to set intended endianness +# and -m32/-m64 to set word size based on Kconfigs instead of relying on the +# target triple. +ifeq ($(CROSS_COMPILE),) +ifeq ($(LLVM_IAS),1) +ifeq ($(SRCARCH),arm) +CLANG_FLAGS += --target=arm-linux-gnueabi +else ifeq ($(SRCARCH),arm64) +CLANG_FLAGS += --target=aarch64-linux-gnu +else ifeq ($(SRCARCH),hexagon) +CLANG_FLAGS += --target=hexagon-linux-gnu +else ifeq ($(SRCARCH),m68k) +CLANG_FLAGS += --target=m68k-linux-gnu +else ifeq ($(SRCARCH),mips) +CLANG_FLAGS += --target=mipsel-linux-gnu +else ifeq ($(SRCARCH),powerpc) +CLANG_FLAGS += --target=powerpc64le-linux-gnu +else ifeq ($(SRCARCH),riscv) +CLANG_FLAGS += --target=riscv64-linux-gnu +else ifeq ($(SRCARCH),s390) +CLANG_FLAGS += --target=s390x-linux-gnu +else ifeq ($(SRCARCH),x86) +CLANG_FLAGS += --target=x86_64-linux-gnu +else +$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang) +endif # SRCARCH +endif # LLVM_IAS +else CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) -endif +endif # CROSS_COMPILE + ifeq ($(LLVM_IAS),1) CLANG_FLAGS += -integrated-as else -- 2.32.0.432.gabb21c7263-goog
