On Mon, Aug 2, 2021 at 4:43 PM 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. :: > + I am not sure if LLVM_IAS should also impacts linker selection > + 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 ($(LLVM_IAS),0) > KBUILD_CFLAGS += -Wa,-mno-relax > KBUILD_AFLAGS += -Wa,-mno-relax > endif > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > index 1f4e3eb70f88..3ae63bd35582 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -22,12 +22,12 @@ else > CLANG_FLAGS += --target=$(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 >
