| /* |
| * Copyright 1998-2005 Sun Microsystems, Inc. All Rights Reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| * CA 95054 USA or visit www.sun.com if you need additional information or |
| * have any questions. |
| * |
| */ |
| |
| // Recording and retrieval of oop relocations in compiled code. |
| |
| class CodeBlob; |
| |
| class OopRecorder : public ResourceObj { |
| public: |
| // A two-way mapping from positive indexes to oop handles. |
| // The zero index is reserved for a constant (sharable) null. |
| // Indexes may not be negative. |
| |
| // Use the given arena to manage storage, if not NULL. |
| // By default, uses the current ResourceArea. |
| OopRecorder(Arena* arena = NULL); |
| |
| // Generate a new index on which CodeBlob::oop_addr_at will work. |
| // allocate_index and find_index never return the same index, |
| // and allocate_index never returns the same index twice. |
| // In fact, two successive calls to allocate_index return successive ints. |
| int allocate_index(jobject h) { |
| return add_handle(h, false); |
| } |
| |
| // For a given jobject, this will return the same index repeatedly. |
| // The index can later be given to oop_at to retrieve the oop. |
| // However, the oop must not be changed via CodeBlob::oop_addr_at. |
| int find_index(jobject h) { |
| int index = maybe_find_index(h); |
| if (index < 0) { // previously unallocated |
| index = add_handle(h, true); |
| } |
| return index; |
| } |
| |
| // variant of find_index which does not allocate if not found (yields -1) |
| int maybe_find_index(jobject h); |
| |
| // returns the size of the generated oop table, for sizing the CodeBlob. |
| // must be called after all oops are allocated! |
| int oop_size(); |
| |
| // Retrieve the oop handle at a given index. |
| jobject handle_at(int index); |
| |
| int element_count() { |
| // there is always a NULL virtually present as first object |
| return _handles->length() + first_index; |
| } |
| |
| // copy the generated oop table to CodeBlob |
| void copy_to(CodeBlob* code); // => code->copy_oops(_handles) |
| |
| bool is_unused() { return _handles == NULL && !_complete; } |
| #ifdef ASSERT |
| bool is_complete() { return _complete; } |
| #endif |
| |
| private: |
| // leaky hash table of handle => index, to help detect duplicate insertion |
| class IndexCache: public ResourceObj { |
| // This class is only used by the OopRecorder class. |
| friend class OopRecorder; |
| enum { |
| _log_cache_size = 9, |
| _cache_size = (1<<_log_cache_size), |
| // Index entries are ints. The LSBit is a collision indicator. |
| _collision_bit_shift = 0, |
| _collision_bit = 1, |
| _index_shift = _collision_bit_shift+1 |
| }; |
| int _cache[_cache_size]; |
| static juint cache_index(jobject handle) { |
| juint ci = (int) (intptr_t) handle; |
| ci ^= ci >> (BitsPerByte*2); |
| ci += ci >> (BitsPerByte*1); |
| return ci & (_cache_size-1); |
| } |
| int* cache_location(jobject handle) { |
| return &_cache[ cache_index(handle) ]; |
| } |
| static bool cache_location_collision(int* cloc) { |
| return ((*cloc) & _collision_bit) != 0; |
| } |
| static int cache_location_index(int* cloc) { |
| return (*cloc) >> _index_shift; |
| } |
| static void set_cache_location_index(int* cloc, int index) { |
| int cval0 = (*cloc); |
| int cval1 = (index << _index_shift); |
| if (cval0 != 0 && cval1 != cval0) cval1 += _collision_bit; |
| (*cloc) = cval1; |
| } |
| IndexCache(); |
| }; |
| |
| // Helper function; returns false for NULL or Universe::non_oop_word(). |
| inline bool is_real_jobject(jobject h); |
| |
| void maybe_initialize(); |
| int add_handle(jobject h, bool make_findable); |
| |
| enum { null_index = 0, first_index = 1, index_cache_threshold = 20 }; |
| |
| GrowableArray<jobject>* _handles; // ordered list (first is always NULL) |
| GrowableArray<int>* _no_finds; // all unfindable indexes; usually empty |
| IndexCache* _indexes; // map: jobject -> its probable index |
| Arena* _arena; |
| bool _complete; |
| |
| #ifdef ASSERT |
| static int _find_index_calls, _hit_indexes, _missed_indexes; |
| #endif |
| }; |