1 /* 2 * Copyright (c) 2015, 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 SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP 26 #define SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP 27 28 class nmethod; 29 class DepChange; 30 31 // 32 // nmethodBucket is used to record dependent nmethods for 33 // deoptimization. nmethod dependencies are actually <klass, method> 34 // pairs but we really only care about the klass part for purposes of 35 // finding nmethods which might need to be deoptimized. Instead of 36 // recording the method, a count of how many times a particular nmethod 37 // was recorded is kept. This ensures that any recording errors are 38 // noticed since an nmethod should be removed as many times are it's 39 // added. 40 // 41 class nmethodBucket: public CHeapObj<mtClass> { 42 friend class VMStructs; 43 private: 44 nmethod* _nmethod; 45 int _count; 46 nmethodBucket* _next; 47 48 public: 49 nmethodBucket(nmethod* nmethod, nmethodBucket* next) : 50 _nmethod(nmethod), _next(next), _count(1) {} 51 52 int count() { return _count; } 53 int increment() { _count += 1; return _count; } 54 int decrement(); 55 nmethodBucket* next() { return _next; } 56 void set_next(nmethodBucket* b) { _next = b; } 57 nmethod* get_nmethod() { return _nmethod; } 58 }; 59 60 // 61 // Utility class to manipulate nmethod dependency context. 62 // The context consists of nmethodBucket* (a head of a linked list) 63 // and a boolean flag (does the list contains stale entries). The structure is 64 // encoded as an intptr_t: lower bit is used for the flag. It is possible since 65 // nmethodBucket* is aligned - the structure is malloc'ed in C heap. 66 // Dependency context can be attached either to an InstanceKlass (_dep_context field) 67 // or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp). 68 // DependencyContext class operates on some location which holds a intptr_t value. 69 // 70 class DependencyContext : public StackObj { 71 friend class VMStructs; 72 friend class TestDependencyContext; 73 private: 74 enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 }; 75 76 intptr_t* _dependency_context_addr; 77 78 void set_dependencies(nmethodBucket* b) { 79 assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned"); 80 if (has_stale_entries()) { 81 *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask; 82 } else { 83 *_dependency_context_addr = intptr_t(b); 84 } 85 } 86 87 void clear_has_stale_entries() { 88 *_dependency_context_addr &= ~_has_stale_entries_mask; 89 } 90 91 nmethodBucket* dependencies() { 92 intptr_t value = *_dependency_context_addr; 93 return (nmethodBucket*) (value & ~_has_stale_entries_mask); 94 } 95 96 bool has_stale_entries() const { 97 intptr_t value = *_dependency_context_addr; 98 return (value & _has_stale_entries_mask) != 0; 99 }; 100 101 public: 102 DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {} 103 104 static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false 105 106 int mark_dependent_nmethods(DepChange& changes); 107 void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false); 108 void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false); 109 int remove_all_dependents(); 110 111 void expunge_stale_entries(); 112 113 #ifndef PRODUCT 114 void print_dependent_nmethods(bool verbose); 115 bool is_dependent_nmethod(nmethod* nm); 116 bool find_stale_entries(); 117 #endif //PRODUCT 118 }; 119 120 #endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP