From b67ef52116de116e4945b964aa3c4c828848eb1c 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 [ Upstream commit de9c0d49d85dc563549972edc5589d195cd5e859 ] 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 Signed-off-by: Sasha Levin --- 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 3b10a48fa040..a84efd4aad37 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 += -march=armv7-a -mfloat-abi=softfp -mfpu=neon endif ifeq ($(ARCH),arm64) CFLAGS_REMOVE_neon1.o += -mgeneral-regs-only -- cgit v1.2.3