Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 2 Jul 2021 11:29:31 -0700 | Subject | Re: [PATCH] arm64: drop CROSS_COMPILE for LLVM=1 LLVM_IAS=1 |
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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? -- Thanks, ~Nick Desaulniers
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