1 /*
   2  * Copyright (c) 2006, 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
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  22  *
  23  */
  24 
  25 #ifndef SHARE_OOPS_MARKWORD_INLINE_HPP
  26 #define SHARE_OOPS_MARKWORD_INLINE_HPP
  27 
  28 #include "oops/klass.hpp"
  29 #include "oops/markWord.hpp"
  30 #include "runtime/globals.hpp"
  31 
  32 // Should this header be preserved during GC?
  33 template <typename KlassProxy>
  34 inline bool markWord::must_be_preserved(KlassProxy klass) const {
  35   if (UseBiasedLocking) {
  36     if (has_bias_pattern()) {
  37       // Will reset bias at end of collection
  38       // Mark words of biased and currently locked objects are preserved separately
  39       return false;
  40     }
  41     markWord prototype_header = prototype_for_klass(klass);
  42     if (prototype_header.has_bias_pattern()) {
  43       // Individual instance which has its bias revoked; must return
  44       // true for correctness
  45       return true;
  46     }
  47   }
  48   return (!is_unlocked() || !has_no_hash());
  49 }
  50 
  51 // Should this header be preserved in the case of a promotion failure during scavenge?
  52 template <typename KlassProxy>
  53 inline bool markWord::must_be_preserved_for_promotion_failure(KlassProxy klass) const {
  54   if (UseBiasedLocking) {
  55     // We don't explicitly save off the mark words of biased and
  56     // currently-locked objects during scavenges, so if during a
  57     // promotion failure we encounter either a biased mark word or a
  58     // klass which still has a biasable prototype header, we have to
  59     // preserve the mark word. This results in oversaving, but promotion
  60     // failures are rare, and this avoids adding more complex logic to
  61     // the scavengers to call new variants of
  62     // BiasedLocking::preserve_marks() / restore_marks() in the middle
  63     // of a scavenge when a promotion failure has first been detected.
  64     if (has_bias_pattern() || prototype_for_klass(klass).has_bias_pattern()) {
  65       return true;
  66     }
  67   }
  68   return (!is_unlocked() || !has_no_hash());
  69 }
  70 
  71 // Same as must_be_preserved_for_promotion_failure().
  72 inline bool markWord::must_be_preserved_for_cms_scavenge(Klass* klass_of_obj_containing_mark) const {
  73   return must_be_preserved_for_promotion_failure(klass_of_obj_containing_mark);
  74 }
  75 
  76 inline markWord markWord::prototype_for_klass(const Klass* klass) {
  77   markWord prototype_header = klass->prototype_header();
  78   assert(prototype_header == prototype() || prototype_header.has_bias_pattern(), "corrupt prototype header");
  79 
  80   return prototype_header;
  81 }
  82 
  83 #endif // SHARE_OOPS_MARKWORD_INLINE_HPP