From de9c0d49d85dc563549972edc5589d195cd5e859 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Sat, 2 Feb 2019 03:34:36 +0100 Subject: ARM: 8833/1: Ensure that NEON code always compiles with Clang While building arm32 allyesconfig, I ran into the following errors: arch/arm/lib/xor-neon.c:17:2: error: You should compile this file with '-mfloat-abi=softfp -mfpu=neon' In file included from lib/raid6/neon1.c:27: /home/nathan/cbl/prebuilt/lib/clang/8.0.0/include/arm_neon.h:28:2: error: "NEON support not enabled" Building V=1 showed NEON_FLAGS getting passed along to Clang but __ARM_NEON__ was not getting defined. Ultimately, it boils down to Clang only defining __ARM_NEON__ when targeting armv7, rather than armv6k, which is the '-march' value for allyesconfig. >From lib/Basic/Targets/ARM.cpp in the Clang source: // This only gets set when Neon instructions are actually available, unlike // the VFP define, hence the soft float and arch check. This is subtly // different from gcc, we follow the intent which was that it should be set // when Neon instructions are actually available. if ((FPU & NeonFPU) && !SoftFloat && ArchVersion >= 7) { Builder.defineMacro("__ARM_NEON", "1"); Builder.defineMacro("__ARM_NEON__"); // current AArch32 NEON implementations do not support double-precision // floating-point even when it is present in VFP. Builder.defineMacro("__ARM_NEON_FP", "0x" + Twine::utohexstr(HW_FP & ~HW_FP_DP)); } Ard Biesheuvel recommended explicitly adding '-march=armv7-a' at the beginning of the NEON_FLAGS definitions so that __ARM_NEON__ always gets definined by Clang. This doesn't functionally change anything because that code will only run where NEON is supported, which is implicitly armv7. Link: https://github.com/ClangBuiltLinux/linux/issues/287 Suggested-by: Ard Biesheuvel Signed-off-by: Nathan Chancellor Acked-by: Nicolas Pitre Reviewed-by: Nick Desaulniers Reviewed-by: Stefan Agner Signed-off-by: Russell King --- lib/raid6/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile index 4e90d443d1b0..e723eacf7868 100644 --- a/lib/raid6/Makefile +++ b/lib/raid6/Makefile @@ -39,7 +39,7 @@ endif ifeq ($(CONFIG_KERNEL_MODE_NEON),y) NEON_FLAGS := -ffreestanding ifeq ($(ARCH),arm) -NEON_FLAGS += -mfloat-abi=softfp -mfpu=neon +NEON_FLAGS += -march=armv7-a -mfloat-abi=softfp -mfpu=neon endif CFLAGS_recov_neon_inner.o += $(NEON_FLAGS) ifeq ($(ARCH),arm64) -- cgit v1.2.3