On Wed, Jul 21, 2021 at 2:30 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote: > > On 7/20/2021 1:04 AM, Masahiro Yamada wrote: > > On Fri, Jul 9, 2021 at 8:25 AM 'Nick Desaulniers' via Clang Built > > Linux <clang-built-linux@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxx> > >> Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx> > >> Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > >> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > >> --- > >> 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),) > > > > > > Do you need to check $(LLVM) ? > > > > > > LLVM=1 is a convenient switch to change all the > > defaults, but yet you can flip each tool individually. > > > > Instead of LLVM=1, you still should be able to > > get the equivalent setups by: > > > > > > make CC=clang LD=ld.lld AR=llvm-ar OBJCOPY=llvm-objcopy ... > > > > > > The --target option is passed to only > > KBUILD_CFLAGS and KBUILD_AFLAGS. > > > > So, when we talk about --target=, > > we only care about whether $(CC) is Clang. > > Not caring about $(AR), $(LD), or $(OBJCOPY). > > > > > > scripts/Makefile.clang is already guarded by: > > > > ifneq ($(findstring clang,$(CC_VERSION_TEXT)), > > $ make ARCH=arm64 CC=clang LLVM_IAS=1 > > will use the right compiler and assembler but none of the other binary > tools because '--prefix=' will not be set so CROSS_COMPILE needs to be > specified still, which defeats the purpose of this whole change. This > patch is designed to work for the "normal" case of saying "I want to use > all of the LLVM tools", not "I want to use clang by itself". I disagree. LLVM=1 is a shorthand. make LLVM=1 LLVM_IAS=1 should be equivalent to: make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \ OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \ HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld \ LLVM_IAS=1 We do not care about the origin of CC=clang, whether it came from LLVM=1 or every tool was explicitly, individually specified. ifneq ($(LLVM),) is a garbage code that checks a pointless thing. > >> +ifeq ($(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 > >> -- > >> 2.32.0.93.g670b81a890-goog > >> > >> -- > >> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > >> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > >> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210708232522.3118208-3-ndesaulniers%40google.com. > > > > > > -- Best Regards Masahiro Yamada
