Re: [PATCH 1/3] [RESEND] ARM: pass -march=armv7-a when building NEON files with clang

From: Nicolas Pitre
Date: Thu Feb 18 2016 - 12:31:45 EST


On Thu, 18 Feb 2016, Arnd Bergmann wrote:

> clang ignores the -mfpu=neon flag when building with -march=armv6:
>
> In file included from lib/raid6/neon1.c:27:
> clang/3.8.0/include/arm_neon.h:28:2: error: "NEON support not enabled"
>
> There is no real need to build the file with -march=armv6 in a
> multi-CPU enabled kernel, as nothing in here will ever get called
> on an ARMv6 CPU. Adding -march=armv7 doesn't hurt and can only
> improve the code quality.

Is this enough to override a previous -mfpu for gcc?


>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> arch/arm/lib/Makefile | 2 +-
> lib/raid6/Makefile | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
> index d8a780799506..a86c6c8e0648 100644
> --- a/arch/arm/lib/Makefile
> +++ b/arch/arm/lib/Makefile
> @@ -35,7 +35,7 @@ $(obj)/csumpartialcopy.o: $(obj)/csumpartialcopygeneric.S
> $(obj)/csumpartialcopyuser.o: $(obj)/csumpartialcopygeneric.S
>
> ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
> - NEON_FLAGS := -mfloat-abi=softfp -mfpu=neon
> + NEON_FLAGS := -mfloat-abi=softfp -mfpu=neon -march=armv7-a
> CFLAGS_xor-neon.o += $(NEON_FLAGS)
> obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
> endif
> diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile
> index 3b10a48fa040..4ef3e800fb39 100644
> --- a/lib/raid6/Makefile
> +++ b/lib/raid6/Makefile
> @@ -23,7 +23,7 @@ endif
> ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
> NEON_FLAGS := -ffreestanding
> ifeq ($(ARCH),arm)
> -NEON_FLAGS += -mfloat-abi=softfp -mfpu=neon
> +NEON_FLAGS += -mfloat-abi=softfp -mfpu=neon -march=armv7-a
> endif
> ifeq ($(ARCH),arm64)
> CFLAGS_REMOVE_neon1.o += -mgeneral-regs-only
> --
> 2.7.0
>
>