Messages in this thread Patch in this message | | | Date | Mon, 16 May 2022 14:09:54 -0700 | Subject | [PATCH v3 4/4] ARM: pass -march= only to compiler | From | Nick Desaulniers <> |
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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
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