arch/arm/include/asm/neon.h

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