On Thu, Aug 5, 2021 at 8:16 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > On Tue, Aug 3, 2021 at 8:43 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > > > LLVM_IAS=1 controls enabling clang's integrated assembler via > > -integrated-as. This was an explicit opt in until we could enable > > assembler support in Clang for more architecures. Now we have support > > and CI coverage of LLVM_IAS=1 for all architecures except a few more > > bugs affecting s390 and powerpc. > > > > This commit flips the default from opt in via LLVM_IAS=1 to opt out via > > LLVM_IAS=0. CI systems or developers that were previously doing builds > > with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now > > explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly > > opted-in. > > > > This finally shortens the command line invocation when cross compiling > > with LLVM to simply: > > > > $ make ARCH=arm64 LLVM=1 > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1434 > > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > --- > > Note: base is: > > https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@xxxxxxxxxx/ > > > > Documentation/kbuild/llvm.rst | 14 ++++++++------ > > Makefile | 2 +- > > arch/riscv/Makefile | 2 +- > > scripts/Makefile.clang | 6 +++--- > > 4 files changed, 13 insertions(+), 11 deletions(-) > > > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > > index f8a360958f4c..16712fab4d3a 100644 > > --- a/Documentation/kbuild/llvm.rst > > +++ b/Documentation/kbuild/llvm.rst > > @@ -60,17 +60,14 @@ They can be enabled individually. The full list of the parameters: :: > > OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \ > > HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld > > > > -Currently, the integrated assembler is disabled by default. You can pass > > -``LLVM_IAS=1`` to enable it. > > +Currently, the integrated assembler is enabled by default. You can pass > > +``LLVM_IAS=0`` to disable it. > > > > Omitting CROSS_COMPILE > > ---------------------- > > > > As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``. > > > > -Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive > > -``--prefix=<path>`` to search for the GNU assembler and linker. > > - > > If ``CROSS_COMPILE`` is not specified, the ``--target=<triple>`` is inferred > > from ``ARCH``. > > > > @@ -78,7 +75,12 @@ That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary. > > > > For example, to cross-compile the arm64 kernel:: > > > > - make ARCH=arm64 LLVM=1 LLVM_IAS=1 > > + make ARCH=arm64 LLVM=1 > > + > > +If ``LLVM_IAS=0`` is specified, ``CROSS_COMPILE`` is also used to derive > > +``--prefix=<path>`` to search for the GNU assembler and linker. :: > > + > > + make ARCH=arm64 LLVM=1 LLVM_IAS=0 CROSS_COMPILE=aarch64-linux-gnu- > > > > Supported Architectures > > ----------------------- > > diff --git a/Makefile b/Makefile > > index 444558e62cbc..b24b48c9ebb7 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -845,7 +845,7 @@ else > > DEBUG_CFLAGS += -g > > endif > > > > -ifneq ($(LLVM_IAS),1) > > +ifeq ($(LLVM_IAS),0) > > KBUILD_AFLAGS += -Wa,-gdwarf-2 > > endif > > > > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile > > index bc74afdbf31e..807f7c94bc6f 100644 > > --- a/arch/riscv/Makefile > > +++ b/arch/riscv/Makefile > > @@ -41,7 +41,7 @@ endif > > ifeq ($(CONFIG_LD_IS_LLD),y) > > KBUILD_CFLAGS += -mno-relax > > KBUILD_AFLAGS += -mno-relax > > -ifneq ($(LLVM_IAS),1) > > +ifeq ($(LLVM_IAS),0) > > KBUILD_CFLAGS += -Wa,-mno-relax > > KBUILD_AFLAGS += -Wa,-mno-relax > > endif > > > > Please drop these two hunks. > > I will apply my patch instead. > https://lore.kernel.org/patchwork/patch/1472580/ > > > > > > > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > > index 1f4e3eb70f88..3ae63bd35582 100644 > > --- a/scripts/Makefile.clang > > +++ b/scripts/Makefile.clang > > @@ -22,12 +22,12 @@ else > > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > > endif # CROSS_COMPILE > > > > -ifeq ($(LLVM_IAS),1) > > -CLANG_FLAGS += -integrated-as > > -else > > +ifeq ($(LLVM_IAS),0) > > CLANG_FLAGS += -no-integrated-as > > GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) > > CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) > > +else > > +CLANG_FLAGS += -integrated-as > > endif > > CLANG_FLAGS += -Werror=unknown-warning-option > > KBUILD_CFLAGS += $(CLANG_FLAGS) > > > > base-commit: d7a86429dbc691bf540688fcc8542cc20246a85b > > prerequisite-patch-id: 0d3072ecb5fd06ff6fd6ea81fe601f6c54c23910 > > prerequisite-patch-id: 2654829756eb8a094a0ffad1679caa75a4d86619 > > prerequisite-patch-id: a51e7885ca2376d008bbf146a5589da247806f7b > > -- > > 2.32.0.554.ge1b32706d8-goog > > > > > When we negate a flag that is enabled by default, > which is a common way? > - set it to '0' > - set is to empty > > > So, I was wondering if we should support > not only LLVM_IAS=0 but also LLVM_IAS=. > > What do you think? always asking for 0 or 1 is perhaps better. > > > -- > Best Regards > Masahiro Yamada
