root/arch/arm/include/asm/neon.h

INCLUDED FROM

   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
  31 void kernel_neon_begin(void);
  32 #endif
  33 void kernel_neon_end(void);