1 /*

     2  * Copyright (c) 2015, 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 #ifndef SHARE_GC_Z_ZFORWARDING_INLINE_HPP

    25 #define SHARE_GC_Z_ZFORWARDING_INLINE_HPP

    26 

    27 #include "gc/z/zForwarding.hpp"

    28 #include "gc/z/zGlobals.hpp"

    29 #include "gc/z/zHash.inline.hpp"

    30 #include "runtime/atomic.hpp"

    31 #include "utilities/debug.hpp"

    32 

    33 inline uintptr_t ZForwarding::start() const {

    34   return _start;

    35 }

    36 

    37 inline size_t ZForwarding::object_alignment_shift() const {

    38   return _object_alignment_shift;

    39 }

    40 

    41 inline bool ZForwarding::inc_refcount() {

    42   uint32_t refcount = Atomic::load(&_refcount);

    43 

    44   while (refcount > 0) {

    45     const uint32_t old_refcount = refcount;

    46     const uint32_t new_refcount = old_refcount + 1;

    47     const uint32_t prev_refcount = Atomic::cmpxchg(new_refcount, &_refcount, old_refcount);

    48     if (prev_refcount == old_refcount) {

    49       return true;

    50     }

    51 

    52     refcount = prev_refcount;

    53   }

    54 

    55   return false;

    56 }

    57 

    58 inline bool ZForwarding::dec_refcount() {

    59   assert(_refcount > 0, "Invalid state");

    60   return Atomic::sub(1u, &_refcount) == 0u;

    61 }

    62 

    63 inline bool ZForwarding::is_pinned() const {

    64   return Atomic::load(&_pinned);

    65 }

    66 

    67 inline void ZForwarding::set_pinned() {

    68   Atomic::store(true, &_pinned);

    69 }

    70 

    71 inline ZForwardingEntry* ZForwarding::entries() const {

    72   return reinterpret_cast<ZForwardingEntry*>(reinterpret_cast<uintptr_t>(this) + sizeof(*this));

    73 }

    74 

    75 inline ZForwardingEntry ZForwarding::at(ZForwardingCursor* cursor) const {

    76   return Atomic::load(entries() + *cursor);

    77 }

    78 

    79 inline ZForwardingEntry ZForwarding::first(uintptr_t from_index, ZForwardingCursor* cursor) const {

    80   const uint32_t mask = _nentries - 1;

    81   const uint32_t hash = ZHash::uint32_to_uint32((uint32_t)from_index);

    82   *cursor = hash & mask;

    83   return at(cursor);

    84 }

    85 

    86 inline ZForwardingEntry ZForwarding::next(ZForwardingCursor* cursor) const {

    87   const uint32_t mask = _nentries - 1;

    88   *cursor = (*cursor + 1) & mask;

    89   return at(cursor);

    90 }

    91 

    92 inline ZForwardingEntry ZForwarding::find(uintptr_t from_index) const {

    93   ZForwardingCursor dummy;

    94   return find(from_index, &dummy);

    95 }

    96 

    97 inline ZForwardingEntry ZForwarding::find(uintptr_t from_index, ZForwardingCursor* cursor) const {

    98   // Reading entries in the table races with the atomic CAS done for

    99   // insertion into the table. This is safe because each entry is at

   100   // most updated once (from -1 to something else).

   101   ZForwardingEntry entry = first(from_index, cursor);

   102   while (!entry.is_empty()) {

   103     if (entry.from_index() == from_index) {

   104       // Match found, return matching entry

   105       return entry;

   106     }

   107 

   108     entry = next(cursor);

   109   }

   110 

   111   // Match not found, return empty entry

   112   return entry;

   113 }

   114 

   115 inline uintptr_t ZForwarding::insert(uintptr_t from_index, uintptr_t to_offset, ZForwardingCursor* cursor) {

   116   const ZForwardingEntry new_entry(from_index, to_offset);

   117   const ZForwardingEntry old_entry; // empty

   118 

   119   for (;;) {

   120     const ZForwardingEntry prev_entry = Atomic::cmpxchg(new_entry, entries() + *cursor, old_entry);

   121     if (prev_entry.is_empty()) {

   122       // Success

   123       return to_offset;

   124     }

   125 

   126     // Find next empty or matching entry

   127     ZForwardingEntry entry = at(cursor);

   128     while (!entry.is_empty()) {

   129       if (entry.from_index() == from_index) {

   130         // Match found, return already inserted address

   131         return entry.to_offset();

   132       }

   133 

   134       entry = next(cursor);

   135     }

   136   }

   137 }

   138 

   139 #endif // SHARE_GC_Z_ZFORWARDING_INLINE_HPP