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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>
46 lines
1.5 KiB
Makefile
46 lines
1.5 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# linux/arch/arm/lib/Makefile
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#
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# Copyright (C) 1995-2000 Russell King
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#
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lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
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csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
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delay.o delay-loop.o findbit.o memchr.o memcpy.o \
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memmove.o memset.o setbit.o \
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strchr.o strrchr.o \
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testchangebit.o testclearbit.o testsetbit.o \
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ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
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ucmpdi2.o lib1funcs.o div64.o \
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io-readsb.o io-writesb.o io-readsl.o io-writesl.o \
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call_with_stack.o bswapsdi2.o
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mmu-y := clear_user.o copy_page.o getuser.o putuser.o \
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copy_from_user.o copy_to_user.o
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# using lib_ here won't override already available weak symbols
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obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o
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lib-$(CONFIG_MMU) += $(mmu-y)
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ifeq ($(CONFIG_CPU_32v3),y)
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lib-y += io-readsw-armv3.o io-writesw-armv3.o
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else
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lib-y += io-readsw-armv4.o io-writesw-armv4.o
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endif
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ifeq ($(CONFIG_ARCH_RPC),y)
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lib-y += ecard.o io-acorn.o floppydma.o
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AFLAGS_delay-loop.o += -march=armv4
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endif
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$(obj)/csumpartialcopy.o: $(obj)/csumpartialcopygeneric.S
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$(obj)/csumpartialcopyuser.o: $(obj)/csumpartialcopygeneric.S
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ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
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NEON_FLAGS := -march=armv7-a -mfloat-abi=softfp -mfpu=neon
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CFLAGS_xor-neon.o += $(NEON_FLAGS)
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obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
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endif
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