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de9c0d49d8
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>
47 lines
1.3 KiB
C
47 lines
1.3 KiB
C
/*
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* linux/arch/arm/lib/xor-neon.c
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*
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* Copyright (C) 2013 Linaro Ltd <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/raid/xor.h>
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#include <linux/module.h>
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MODULE_LICENSE("GPL");
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#ifndef __ARM_NEON__
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#error You should compile this file with '-march=armv7-a -mfloat-abi=softfp -mfpu=neon'
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#endif
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/*
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* Pull in the reference implementations while instructing GCC (through
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* -ftree-vectorize) to attempt to exploit implicit parallelism and emit
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* NEON instructions.
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*/
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#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
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#pragma GCC optimize "tree-vectorize"
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#else
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/*
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* While older versions of GCC do not generate incorrect code, they fail to
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* recognize the parallel nature of these functions, and emit plain ARM code,
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* which is known to be slower than the optimized ARM code in asm-arm/xor.h.
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*/
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#warning This code requires at least version 4.6 of GCC
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#endif
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#pragma GCC diagnostic ignored "-Wunused-variable"
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#include <asm-generic/xor.h>
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struct xor_block_template const xor_block_neon_inner = {
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.name = "__inner_neon__",
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.do_2 = xor_8regs_2,
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.do_3 = xor_8regs_3,
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.do_4 = xor_8regs_4,
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.do_5 = xor_8regs_5,
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};
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EXPORT_SYMBOL(xor_block_neon_inner);
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