lkml.org 
[lkml]   [2021]   [Jul]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] arm64: drop CROSS_COMPILE for LLVM=1 LLVM_IAS=1
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

\
 
 \ /
  Last update: 2021-07-02 20:30    [W:0.221 / U:2.884 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site