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 83