Messages in this thread | | | Subject | Re: [PATCH v2 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for LLVM=1 LLVM_IAS=1 | From | Nathan Chancellor <> | Date | Fri, 9 Jul 2021 13:44:10 -0700 |
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On 7/8/2021 4:25 PM, 'Nick Desaulniers' via Clang Built Linux wrote: > 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@kernel.org> > Suggested-by: Nathan Chancellor <nathan@kernel.org> > Suggested-by: Masahiro Yamada <masahiroy@kernel.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> I tested arm, arm64, i386, riscv, and x86_64 and verified that the error fired for an unsupported arch. Consider this:
Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org>
> --- > 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 | 5 +++++ > scripts/Makefile.clang | 34 ++++++++++++++++++++++++++++++++-- > 2 files changed, 37 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..956603f56724 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -1,6 +1,36 @@ > -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 ($(SRCARCH),arm) > +CLANG_FLAGS += --target=arm-linux-gnueabi > +else ifeq ($(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 > +endif # LLVM > +else > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > -endif > +endif # CROSS_COMPILE > + > ifeq ($(LLVM_IAS),1) > CLANG_FLAGS += -integrated-as > else >
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