duke@435: /*
duke@435:  * Copyright 1998-2005 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: // Recording and retrieval of oop relocations in compiled code.
duke@435: 
duke@435: class CodeBlob;
duke@435: 
duke@435: class OopRecorder : public ResourceObj {
duke@435:  public:
duke@435:   // A two-way mapping from positive indexes to oop handles.
duke@435:   // The zero index is reserved for a constant (sharable) null.
duke@435:   // Indexes may not be negative.
duke@435: 
duke@435:   // Use the given arena to manage storage, if not NULL.
duke@435:   // By default, uses the current ResourceArea.
duke@435:   OopRecorder(Arena* arena = NULL);
duke@435: 
duke@435:   // Generate a new index on which CodeBlob::oop_addr_at will work.
duke@435:   // allocate_index and find_index never return the same index,
duke@435:   // and allocate_index never returns the same index twice.
duke@435:   // In fact, two successive calls to allocate_index return successive ints.
duke@435:   int allocate_index(jobject h) {
duke@435:     return add_handle(h, false);
duke@435:   }
duke@435: 
duke@435:   // For a given jobject, this will return the same index repeatedly.
duke@435:   // The index can later be given to oop_at to retrieve the oop.
duke@435:   // However, the oop must not be changed via CodeBlob::oop_addr_at.
duke@435:   int find_index(jobject h) {
duke@435:     int index = maybe_find_index(h);
duke@435:     if (index < 0) {  // previously unallocated
duke@435:       index = add_handle(h, true);
duke@435:     }
duke@435:     return index;
duke@435:   }
duke@435: 
duke@435:   // variant of find_index which does not allocate if not found (yields -1)
duke@435:   int maybe_find_index(jobject h);
duke@435: 
duke@435:   // returns the size of the generated oop table, for sizing the CodeBlob.
duke@435:   // must be called after all oops are allocated!
duke@435:   int oop_size();
duke@435: 
duke@435:   // Retrieve the oop handle at a given index.
duke@435:   jobject handle_at(int index);
duke@435: 
duke@435:   int element_count() {
duke@435:     // there is always a NULL virtually present as first object
duke@435:     return _handles->length() + first_index;
duke@435:   }
duke@435: 
duke@435:   // copy the generated oop table to CodeBlob
duke@435:   void copy_to(CodeBlob* code);  // => code->copy_oops(_handles)
duke@435: 
duke@435:   bool is_unused() { return _handles == NULL && !_complete; }
duke@435: #ifdef ASSERT
duke@435:   bool is_complete() { return _complete; }
duke@435: #endif
duke@435: 
duke@435:  private:
duke@435:   // leaky hash table of handle => index, to help detect duplicate insertion
duke@435:   class IndexCache: public ResourceObj {
duke@435:     // This class is only used by the OopRecorder class.
duke@435:     friend class OopRecorder;
duke@435:     enum {
duke@435:       _log_cache_size = 9,
duke@435:       _cache_size = (1<<_log_cache_size),
duke@435:       // Index entries are ints.  The LSBit is a collision indicator.
duke@435:       _collision_bit_shift = 0,
duke@435:       _collision_bit = 1,
duke@435:       _index_shift = _collision_bit_shift+1
duke@435:     };
duke@435:     int _cache[_cache_size];
duke@435:     static juint cache_index(jobject handle) {
duke@435:       juint ci = (int) (intptr_t) handle;
duke@435:       ci ^= ci >> (BitsPerByte*2);
duke@435:       ci += ci >> (BitsPerByte*1);
duke@435:       return ci & (_cache_size-1);
duke@435:     }
duke@435:     int* cache_location(jobject handle) {
duke@435:       return &_cache[ cache_index(handle) ];
duke@435:     }
duke@435:     static bool cache_location_collision(int* cloc) {
duke@435:       return ((*cloc) & _collision_bit) != 0;
duke@435:     }
duke@435:     static int cache_location_index(int* cloc) {
duke@435:       return (*cloc) >> _index_shift;
duke@435:     }
duke@435:     static void set_cache_location_index(int* cloc, int index) {
duke@435:       int cval0 = (*cloc);
duke@435:       int cval1 = (index << _index_shift);
duke@435:       if (cval0 != 0 && cval1 != cval0)  cval1 += _collision_bit;
duke@435:       (*cloc) = cval1;
duke@435:     }
duke@435:     IndexCache();
duke@435:   };
duke@435: 
duke@435:   // Helper function; returns false for NULL or Universe::non_oop_word().
duke@435:   inline bool is_real_jobject(jobject h);
duke@435: 
duke@435:   void maybe_initialize();
duke@435:   int add_handle(jobject h, bool make_findable);
duke@435: 
duke@435:   enum { null_index = 0, first_index = 1, index_cache_threshold = 20 };
duke@435: 
duke@435:   GrowableArray<jobject>*   _handles;  // ordered list (first is always NULL)
duke@435:   GrowableArray<int>*       _no_finds; // all unfindable indexes; usually empty
duke@435:   IndexCache*               _indexes;  // map: jobject -> its probable index
duke@435:   Arena*                    _arena;
duke@435:   bool                      _complete;
duke@435: 
duke@435: #ifdef ASSERT
duke@435:   static int _find_index_calls, _hit_indexes, _missed_indexes;
duke@435: #endif
duke@435: };