Messages in this thread | | | Date | Sat, 3 Jul 2021 17:47:21 -0700 | From | Nathan Chancellor <> | Subject | Re: [PATCH] arm64: drop CROSS_COMPILE for LLVM=1 LLVM_IAS=1 |
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On Fri, Jul 02, 2021 at 11:29:31AM -0700, Nick Desaulniers wrote: > On Fri, Jul 2, 2021 at 4:59 AM Arnd Bergmann <arnd@kernel.org> wrote: > > > > On Fri, Jul 2, 2021 at 1:55 AM 'Nick Desaulniers' via Clang Built > > Linux <clang-built-linux@googlegroups.com> wrote: > > > > > > +ifneq ($(LLVM),) > > > +ifneq ($(LLVM_IAS),) > > > +ifeq ($(CROSS_COMPILE),) > > > +CLANG_TARGET :=--target=aarch64-linux > > > +CLANG_FLAGS += $(CLANG_TARGET) > > > +KBUILD_CFLAGS += $(CLANG_TARGET) > > > +KBUILD_AFLAGS += $(CLANG_TARGET) > > > +endif > > > +endif > > > +endif > > > > I think only the "CLANG_TARGET :=--target=aarch64-linux" line should > > go into the > > per-architecture Makefile. It doesn't hurt to just set that > > unconditionally here, > > and then change the CLANG_FLAGS logic in the top-level Makefile to use this > > in place of $(notdir $(CROSS_COMPILE:%-=%)). > > I don't think we can do that. Based on the order the arch/ specific > Makefiles are included, if we don't eagerly add --target to the > KBUILD_{C|A}FLAGS, then cc-option, as-option, and as-instr macros > (defined in scripts/Makefile.compiler) checks in per arch/ Makefiles > may fail erroneously because --target was not set for > KBUILD_{C|A}FLAGS yet. > > Another issue is the order of operations between the top level > Makefile and the per arch/ Makefiles. The `notdir` block you > reference occurs earlier than the per-arch includes: > > 609 TENTATIVE_CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > ... > 648 include $(srctree)/arch/$(SRCARCH)/Makefile > > We would need the opposite order to do what you describe. Reordering > these would effectively be a revert of > commit ae6b289a3789 ("kbuild: Set KBUILD_CFLAGS before incl. arch Makefile") > which I'm not sure we want to do. But maybe there's another way I'm > not seeing yet?
Is there any reason we cannot just add this sort of logic to the main Makefile?
Such as (indentation to emphasis diff):
ifeq ($(CROSS_COMPILE),) ifneq ($(LLVM),) ifeq ($(LLVM_IAS),1) ifeq ($(ARCH),arm64) TENTATIVE_CLANG_FLAGS += --target=aarch64-linux else ifeq ($(ARCH),s390) TENTATIVE_CLANG_FLAGS += --target=s390x-linux else ifeq ($(ARCH),x86_64) TENTATIVE_CLANG_FLAGS += --target=x86_64-linux else $(error Specify CROSS_COMPILE or add '--target=' option to Makefile) endif endif endif else TENTATIVE_CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) ifeq ($(LLVM_IAS),1) TENTATIVE_CLANG_FLAGS += -integrated-as else TENTATIVE_CLANG_FLAGS += -no-integrated-as GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) TENTATIVE_CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) endif endif
I know this looks a little cumbersome but it does help us avoid duplication across architecture Makefiles and ordering dependencies.
Cheers, Nathan
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