path: root/arch/arm/lib/Makefile
diff options
authorNathan Chancellor <natechancellor@gmail.com>2019-02-02 03:34:36 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2019-02-12 15:20:09 +0000
commitde9c0d49d85dc563549972edc5589d195cd5e859 (patch)
tree4e9c64d1d00a6f7dca3a74e949a29fc54fde3614 /arch/arm/lib/Makefile
parent5388a5b82199facacd3d7ac0d05aca6e8f902fed (diff)
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 <ard.biesheuvel@linaro.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Acked-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/lib/Makefile')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index ad25fd1872c7..0bff0176db2c 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -39,7 +39,7 @@ $(obj)/csumpartialcopy.o: $(obj)/csumpartialcopygeneric.S
$(obj)/csumpartialcopyuser.o: $(obj)/csumpartialcopygeneric.S
- NEON_FLAGS := -mfloat-abi=softfp -mfpu=neon
+ NEON_FLAGS := -march=armv7-a -mfloat-abi=softfp -mfpu=neon
CFLAGS_xor-neon.o += $(NEON_FLAGS)
obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o