linux/arch/arm/include/asm/neon.h
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   1/* SPDX-License-Identifier: GPL-2.0-only */
   2/*
   3 * linux/arch/arm/include/asm/neon.h
   4 *
   5 * Copyright (C) 2013 Linaro Ltd <ard.biesheuvel@linaro.org>
   6 */
   7
   8#include <asm/hwcap.h>
   9
  10#define cpu_has_neon()          (!!(elf_hwcap & HWCAP_NEON))
  11
  12#ifdef __ARM_NEON__
  13
  14/*
  15 * If you are affected by the BUILD_BUG below, it probably means that you are
  16 * using NEON code /and/ calling the kernel_neon_begin() function from the same
  17 * compilation unit. To prevent issues that may arise from GCC reordering or
  18 * generating(1) NEON instructions outside of these begin/end functions, the
  19 * only supported way of using NEON code in the kernel is by isolating it in a
  20 * separate compilation unit, and calling it from another unit from inside a
  21 * kernel_neon_begin/kernel_neon_end pair.
  22 *
  23 * (1) Current GCC (4.7) might generate NEON instructions at O3 level if
  24 *     -mpfu=neon is set.
  25 */
  26
  27#define kernel_neon_begin() \
  28        BUILD_BUG_ON_MSG(1, "kernel_neon_begin() called from NEON code")
  29
  30#else
  31void kernel_neon_begin(void);
  32#endif
  33void kernel_neon_end(void);
  34