1 /*
   2  * Copyright (c) 2003, 2014, 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_BSD_X86_VM_ORDERACCESS_BSD_X86_INLINE_HPP
  26 #define OS_CPU_BSD_X86_VM_ORDERACCESS_BSD_X86_INLINE_HPP
  27 
  28 #include "runtime/atomic.inline.hpp"
  29 #include "runtime/orderAccess.hpp"
  30 #include "runtime/os.hpp"
  31 
  32 // A compiler barrier, forcing the C++ compiler to invalidate all memory assumptions
  33 static inline void compiler_barrier() {
  34   __asm__ volatile ("" : : : "memory");
  35 }
  36 
  37 // x86 is TSO and hence only needs a fence for storeload
  38 // However, a compiler barrier is still needed to prevent reordering
  39 // between volatile and non-volatile memory accesses.
  40 
  41 // Implementation of class OrderAccess.
  42 
  43 inline void OrderAccess::loadload()   { compiler_barrier(); }
  44 inline void OrderAccess::storestore() { compiler_barrier(); }
  45 inline void OrderAccess::loadstore()  { compiler_barrier(); }
  46 inline void OrderAccess::storeload()  { fence();            }
  47 
  48 inline void OrderAccess::acquire()    { compiler_barrier(); }
  49 inline void OrderAccess::release()    { compiler_barrier(); }
  50 
  51 inline void OrderAccess::fence() {
  52   if (os::is_MP()) {
  53     // always use locked addl since mfence is sometimes expensive
  54 #ifdef AMD64
  55     __asm__ volatile ("lock; addl $0,0(%%rsp)" : : : "cc", "memory");
  56 #else
  57     __asm__ volatile ("lock; addl $0,0(%%esp)" : : : "cc", "memory");
  58 #endif
  59   }
  60   compiler_barrier();
  61 }
  62 
  63 template<>
  64 inline void OrderAccess::specialized_release_store_fence<jbyte> (volatile jbyte*  p, jbyte  v) {
  65   __asm__ volatile (  "xchgb (%2),%0"
  66                     : "=q" (v)
  67                     : "0" (v), "r" (p)
  68                     : "memory");
  69 }
  70 template<>
  71 inline void OrderAccess::specialized_release_store_fence<jshort>(volatile jshort* p, jshort v) {
  72   __asm__ volatile (  "xchgw (%2),%0"
  73                     : "=r" (v)
  74                     : "0" (v), "r" (p)
  75                     : "memory");
  76 }
  77 template<>
  78 inline void OrderAccess::specialized_release_store_fence<jint>  (volatile jint*   p, jint   v) {
  79   __asm__ volatile (  "xchgl (%2),%0"
  80                     : "=r" (v)
  81                     : "0" (v), "r" (p)
  82                     : "memory");
  83 }
  84 
  85 #ifdef AMD64
  86 template<>
  87 inline void OrderAccess::specialized_release_store_fence<jlong> (volatile jlong*  p, jlong  v) {
  88   __asm__ volatile (  "xchgq (%2), %0"
  89                     : "=r" (v)
  90                     : "0" (v), "r" (p)
  91                     : "memory");
  92 }
  93 #endif // AMD64
  94 
  95 template<>
  96 inline void OrderAccess::specialized_release_store_fence<jfloat> (volatile jfloat*  p, jfloat  v) {
  97   release_store_fence((volatile jint*)p, jint_cast(v));
  98 }
  99 template<>
 100 inline void OrderAccess::specialized_release_store_fence<jdouble>(volatile jdouble* p, jdouble v) {
 101   release_store_fence((volatile jlong*)p, jlong_cast(v));
 102 }
 103 
 104 #define VM_HAS_GENERALIZED_ORDER_ACCESS 1
 105 
 106 #endif // OS_CPU_BSD_X86_VM_ORDERACCESS_BSD_X86_INLINE_HPP