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author | Nathan Chancellor <natechancellor@gmail.com> | 2019-02-02 03:34:36 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-05 22:34:39 +0200 |
commit | c716b08e06cafe9e6b713cd5e34dc8cf2286dab8 (patch) | |
tree | 4646ab6af5141dd1da053cbce8b869002f529b1c | |
parent | f74b0a4bf14c15d6bef9d3bdfe90512a6652599e (diff) | |
download | blackbird-obmc-linux-c716b08e06cafe9e6b713cd5e34dc8cf2286dab8.tar.gz blackbird-obmc-linux-c716b08e06cafe9e6b713cd5e34dc8cf2286dab8.zip |
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 <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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r-- | Documentation/arm/kernel_mode_neon.txt | 4 | ||||
-rw-r--r-- | arch/arm/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/arm/lib/xor-neon.c | 2 | ||||
-rw-r--r-- | lib/raid6/Makefile | 2 |
4 files changed, 5 insertions, 5 deletions
diff --git a/Documentation/arm/kernel_mode_neon.txt b/Documentation/arm/kernel_mode_neon.txt index 525452726d31..b9e060c5b61e 100644 --- a/Documentation/arm/kernel_mode_neon.txt +++ b/Documentation/arm/kernel_mode_neon.txt @@ -6,7 +6,7 @@ TL;DR summary * Use only NEON instructions, or VFP instructions that don't rely on support code * Isolate your NEON code in a separate compilation unit, and compile it with - '-mfpu=neon -mfloat-abi=softfp' + '-march=armv7-a -mfpu=neon -mfloat-abi=softfp' * Put kernel_neon_begin() and kernel_neon_end() calls around the calls into your NEON code * Don't sleep in your NEON code, and be aware that it will be executed with @@ -87,7 +87,7 @@ instructions appearing in unexpected places if no special care is taken. Therefore, the recommended and only supported way of using NEON/VFP in the kernel is by adhering to the following rules: * isolate the NEON code in a separate compilation unit and compile it with - '-mfpu=neon -mfloat-abi=softfp'; + '-march=armv7-a -mfpu=neon -mfloat-abi=softfp'; * issue the calls to kernel_neon_begin(), kernel_neon_end() as well as the calls into the unit containing the NEON code from a compilation unit which is *not* built with the GCC flag '-mfpu=neon' set. 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: $(obj)/csumpartialcopygeneric.S ifeq ($(CONFIG_KERNEL_MODE_NEON),y) - 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 endif diff --git a/arch/arm/lib/xor-neon.c b/arch/arm/lib/xor-neon.c index 2c40aeab3eaa..c691b901092f 100644 --- a/arch/arm/lib/xor-neon.c +++ b/arch/arm/lib/xor-neon.c @@ -14,7 +14,7 @@ MODULE_LICENSE("GPL"); #ifndef __ARM_NEON__ -#error You should compile this file with '-mfloat-abi=softfp -mfpu=neon' +#error You should compile this file with '-march=armv7-a -mfloat-abi=softfp -mfpu=neon' #endif /* 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) |