ceph/src/boost/boost/fiber/detail/cpu_relax.hpp

   1
   2 //          Copyright Oliver Kowalke 2016.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 //    (See accompanying file LICENSE_1_0.txt or copy at
   5 //          http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_FIBERS_DETAIL_CPU_RELAX_H
   8 #define BOOST_FIBERS_DETAIL_CPU_RELAX_H
   9
  10 #include <chrono>
  11 #include <thread>
  12
  13 #include <boost/config.hpp>
  14 #include <boost/predef.h>
  15
  16 #include <boost/fiber/detail/config.hpp>
  17
  18 #if BOOST_COMP_MSVC || BOOST_COMP_MSVC_EMULATED
  19 # include <windows.h>
  20 #endif
  21
  22 #ifdef BOOST_HAS_ABI_HEADERS
  23 #  include BOOST_ABI_PREFIX
  24 #endif
  25
  26 namespace boost {
  27 namespace fibers {
  28 namespace detail {
  29
  30 #if BOOST_ARCH_ARM
  31 # if BOOST_COMP_MSVC
  32 #  define cpu_relax() YieldProcessor();
  33 # elif (defined(__ARM_ARCH_6K__) || \
  34         defined(__ARM_ARCH_6Z__) || \
  35         defined(__ARM_ARCH_6ZK__) || \
  36         defined(__ARM_ARCH_6T2__) || \
  37         defined(__ARM_ARCH_7__) || \
  38         defined(__ARM_ARCH_7A__) || \
  39         defined(__ARM_ARCH_7R__) || \
  40         defined(__ARM_ARCH_7M__) || \
  41         defined(__ARM_ARCH_7S__) || \
  42         defined(__ARM_ARCH_8A__) || \
  43         defined(__aarch64__))
  44 // http://groups.google.com/a/chromium.org/forum/#!msg/chromium-dev/YGVrZbxYOlU/Vpgy__zeBQAJ
  45 // mnemonic 'yield' is supported from ARMv6k onwards
  46 #  define cpu_relax() asm volatile ("yield" ::: "memory");
  47 # else
  48 #  define cpu_relax() asm volatile ("nop" ::: "memory");
  49 # endif
  50 #elif BOOST_ARCH_MIPS && (__mips_isa_rev > 1)
  51 # define cpu_relax() asm volatile ("pause" ::: "memory");
  52 #elif BOOST_ARCH_PPC
  53 // http://code.metager.de/source/xref/gnu/glibc/sysdeps/powerpc/sys/platform/ppc.h
  54 // http://stackoverflow.com/questions/5425506/equivalent-of-x86-pause-instruction-for-ppc
  55 // mnemonic 'or' shared resource hints
  56 // or 27, 27, 27 This form of 'or' provides a hint that performance
  57 //               will probably be imrpoved if shared resources dedicated
  58 //               to the executing processor are released for use by other
  59 //               processors
  60 // extended mnemonics (available with POWER7)
  61 // yield   ==   or 27, 27, 27
  62 # define cpu_relax() asm volatile ("or 27,27,27" ::: "memory");
  63 #elif BOOST_ARCH_X86
  64 # if BOOST_COMP_MSVC || BOOST_COMP_MSVC_EMULATED
  65 #  define cpu_relax() YieldProcessor();
  66 # else
  67 #  define cpu_relax() asm volatile ("pause" ::: "memory");
  68 # endif
  69 #else
  70 # define cpu_relax() { \
  71    static constexpr std::chrono::microseconds us0{ 0 }; \
  72    std::this_thread::sleep_for( us0); \
  73   }
  74 #endif
  75
  76 }}}
  77
  78 #ifdef BOOST_HAS_ABI_HEADERS
  79 #  include BOOST_ABI_SUFFIX
  80 #endif
  81
  82 #endif // BOOST_FIBERS_DETAIL_CPU_RELAX_H