1 /*
   2  * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef OS_CPU_LINUX_X86_ORDERACCESS_LINUX_X86_HPP
  26 #define OS_CPU_LINUX_X86_ORDERACCESS_LINUX_X86_HPP
  27 
  28 // Included in orderAccess.hpp header file.
  29 
  30 // Compiler version last used for testing: gcc 4.8.2
  31 // Please update this information when this file changes
  32 
  33 // Implementation of class OrderAccess.
  34 
  35 // A compiler barrier, forcing the C++ compiler to invalidate all memory assumptions
  36 static inline void compiler_barrier() {
  37   __asm__ volatile ("" : : : "memory");
  38 }
  39 
  40 inline void OrderAccess::loadload()   { compiler_barrier(); }
  41 inline void OrderAccess::storestore() { compiler_barrier(); }
  42 inline void OrderAccess::loadstore()  { compiler_barrier(); }
  43 inline void OrderAccess::storeload()  { fence();            }
  44 
  45 inline void OrderAccess::acquire()    { compiler_barrier(); }
  46 inline void OrderAccess::release()    { compiler_barrier(); }
  47 
  48 inline void OrderAccess::fence() {
  49    // always use locked addl since mfence is sometimes expensive
  50 #ifdef AMD64
  51   __asm__ volatile ("lock; addl $0,0(%%rsp)" : : : "cc", "memory");
  52 #else
  53   __asm__ volatile ("lock; addl $0,0(%%esp)" : : : "cc", "memory");
  54 #endif
  55   compiler_barrier();
  56 }
  57 
  58 inline void OrderAccess::cross_modify_fence() {
  59   int idx = 0;
  60 #ifdef AMD64
  61   __asm__ volatile ("cpuid " : "+a" (idx) : : "ebx", "ecx", "edx", "memory");
  62 #else
  63   // On some x86 systems EBX is a reserved register that cannot be
  64   // clobbered, so we must protect it around the CPUID.
  65   __asm__ volatile ("xchg %%esi, %%ebx; cpuid; xchg %%esi, %%ebx " : "+a" (idx) : : "esi", "ecx", "edx", "memory");
  66 #endif
  67 }
  68 
  69 #endif // OS_CPU_LINUX_X86_ORDERACCESS_LINUX_X86_HPP