libc/src/__support/threads/sleep.h

   1 //===-- Utilities for suspending threads ----------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_SLEEP_H
  10 #define LLVM_LIBC_SRC___SUPPORT_THREADS_SLEEP_H
  11
  12 #include "src/__support/macros/attributes.h"
  13 #include "src/__support/macros/config.h"
  14
  15 namespace LIBC_NAMESPACE_DECL {
  16
  17 /// Suspend the thread briefly to assist the thread scheduler during busy loops.
  18 LIBC_INLINE void sleep_briefly() {
  19 #if defined(LIBC_TARGET_ARCH_IS_NVPTX)
  20   if (__nvvm_reflect("__CUDA_ARCH") >= 700)
  21     LIBC_INLINE_ASM("nanosleep.u32 64;" ::: "memory");
  22 #elif defined(LIBC_TARGET_ARCH_IS_AMDGPU)
  23   __builtin_amdgcn_s_sleep(2);
  24 #elif defined(LIBC_TARGET_ARCH_IS_X86)
  25   __builtin_ia32_pause();
  26 #elif defined(LIBC_TARGET_ARCH_IS_AARCH64) && __has_builtin(__builtin_arm_isb)
  27   __builtin_arm_isb(0xf);
  28 #elif defined(LIBC_TARGET_ARCH_IS_AARCH64)
  29   asm volatile("isb\n" ::: "memory");
  30 #else
  31   // Simply do nothing if sleeping isn't supported on this platform.
  32 #endif
  33 }
  34
  35 } // namespace LIBC_NAMESPACE_DECL
  36
  37 #endif // LLVM_LIBC_SRC___SUPPORT_THREADS_SLEEP_H