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 ARCH. If CROSS_COMPILE is not set, simply set --target= for CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS based on $ARCH. Previously, we'd cross compile via: $ ARCH=arm64 CROSS_COMPILE=aarch64-linxu-gnu make LLVM=1 LLVM_IAS=1 Now: $ ARCH=arm64 make LLVM=1 LLVM_IAS=1 Link: https://github.com/ClangBuiltLinux/linux/issues/1399 Suggested-by: Arnd Bergmann <arnd@xxxxxxxxxx> Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> --- 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 | 5 +++++ scripts/Makefile.clang | 38 +++++++++++++++++++++++++++++++++-- 2 files changed, 41 insertions(+), 2 deletions(-) diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index b18401d2ba82..80c63dd9a6d1 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -46,6 +46,11 @@ example: :: clang --target=aarch64-linux-gnu foo.c +When both ``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..a79088797a50 100644 --- a/scripts/Makefile.clang +++ b/scripts/Makefile.clang @@ -1,6 +1,40 @@ -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),) +ifneq ($(LLVM),) +ifeq ($(LLVM_IAS),1) +ifeq ($(ARCH),arm) +CLANG_FLAGS += --target=arm-linux-gnueabi +else ifeq ($(ARCH),arm64) +CLANG_FLAGS += --target=aarch64-linux-gnu +else ifeq ($(ARCH),hexagon) +CLANG_FLAGS += --target=hexagon-linux-gnu +else ifeq ($(ARCH),i386) +CLANG_FLAGS += --target=i686-linux-gnu +else ifeq ($(ARCH),m68k) +CLANG_FLAGS += --target=m68k-linux-gnu +else ifeq ($(ARCH),mips) +CLANG_FLAGS += --target=mipsel-linux-gnu +else ifeq ($(ARCH),powerpc) +CLANG_FLAGS += --target=powerpc64le-linux-gnu +else ifeq ($(ARCH),riscv) +CLANG_FLAGS += --target=riscv64-linux-gnu +else ifeq ($(ARCH),s390) +CLANG_FLAGS += --target=s390x-linux-gnu +else ifeq ($(ARCH),x86) +CLANG_FLAGS += --target=x86_64-linux-gnu +else ifeq ($(ARCH),x86_64) +CLANG_FLAGS += --target=x86_64-linux-gnu +else +$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang) +endif # ARCH +endif # LLVM_IAS +endif # LLVM +else CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) -endif +endif # CROSS_COMPILE + ifeq ($(LLVM_IAS),1) CLANG_FLAGS += -integrated-as else -- 2.32.0.93.g670b81a890-goog
