Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 16 May 2022 14:16:16 -0700 | Subject | Re: [PATCH v3 4/4] ARM: pass -march= only to compiler |
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+ Ard (I messed up my command line invocation of git send-email, sorry for more noise) https://lore.kernel.org/llvm/20220516210954.1660716-1-ndesaulniers@google.com/
On Mon, May 16, 2022 at 2:10 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > When both -march= and -Wa,-march= are specified for assembler or > assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march= > value but Clang will warn that -march= is unused. > > warning: argument unused during compilation: '-march=armv6k' > [-Wunused-command-line-argument] > > This is the top group of warnings we observe when using clang to > assemble the kernel via `ARCH=arm make LLVM=1`. > > Split the arch-y make variable into two, so that -march= flags only get > passed to the compiler, not the assembler. -D flags are added to > KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1315 > Link: https://github.com/ClangBuiltLinux/linux/issues/1587 > Link: https://lore.kernel.org/llvm/628249e8.1c69fb81.d20fd.02ea@mx.google.com/ > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > arch/arm/Makefile | 34 ++++++++++++++++++++++++---------- > 1 file changed, 24 insertions(+), 10 deletions(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index 1029c2503aef..47a300f6f99c 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -57,21 +57,34 @@ endif > KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) > > # This selects which instruction set is used. > +arch-$(CONFIG_CPU_32v7M) :=-march=armv7-m > +arch-$(CONFIG_CPU_32v7) :=-march=armv7-a > +arch-$(CONFIG_CPU_32v6) :=-march=armv6 > +# Only override the compiler option if ARMv6. The ARMv6K extensions are > +# always available in ARMv7 > +ifeq ($(CONFIG_CPU_32v6),y) > +arch-$(CONFIG_CPU_32v6K) :=-march=armv6k > +endif > +arch-$(CONFIG_CPU_32v5) :=-march=armv5te > +arch-$(CONFIG_CPU_32v4T) :=-march=armv4t > +arch-$(CONFIG_CPU_32v4) :=-march=armv4 > +arch-$(CONFIG_CPU_32v3) :=-march=armv3m > + > # Note that GCC does not numerically define an architecture version > # macro, but instead defines a whole series of macros which makes > # testing for a specific architecture or later rather impossible. > -arch-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-m > -arch-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-a > -arch-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 -march=armv6 > -# Only override the compiler opt:ion if ARMv6. The ARMv6K extensions are > +cpp-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 > +cpp-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 > +cpp-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 > +# Only override the compiler option if ARMv6. The ARMv6K extensions are > # always available in ARMv7 > ifeq ($(CONFIG_CPU_32v6),y) > -arch-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 -march=armv6k > +cpp-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 > endif > -arch-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 -march=armv5te > -arch-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 -march=armv4t > -arch-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 -march=armv4 > -arch-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 -march=armv3m > +cpp-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 > +cpp-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 > +cpp-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 > +cpp-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 > > # This selects how we optimise for the processor. > tune-$(CONFIG_CPU_ARM7TDMI) :=-mtune=arm7tdmi > @@ -123,8 +136,9 @@ AFLAGS_ISA :=$(CFLAGS_ISA) > endif > > # Need -Uarm for gcc < 3.x > +KBUILD_CPPFLAGS +=$(cpp-y) > KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm > -KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float > +KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) -Wa,$(arch-y) $(tune-y) -include asm/unified.h -msoft-float > > CHECKFLAGS += -D__arm__ > > -- > 2.36.0.550.gb090851708-goog >
-- Thanks, ~Nick Desaulniers
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