1 /*
   2  * Copyright 1998-2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 // The Rewriter adds caches to the constant pool and rewrites bytecode indices
  26 // pointing into the constant pool for better interpreter performance.
  27 
  28 class Rewriter: public StackObj {
  29  private:
  30   instanceKlassHandle _klass;
  31   constantPoolHandle  _pool;
  32   objArrayHandle      _methods;
  33   intArray            _cp_map;
  34   intStack            _cp_cache_map;
  35 
  36   void init_cp_map(int length) {
  37     _cp_map.initialize(length, -1);
  38     // Choose an initial value large enough that we don't get frequent
  39     // calls to grow().
  40     _cp_cache_map.initialize(length / 2);
  41   }
  42   int  cp_entry_to_cp_cache(int i) { assert(has_cp_cache(i), "oob"); return _cp_map[i]; }
  43   bool has_cp_cache(int i) { return (uint)i < (uint)_cp_map.length() && _cp_map[i] >= 0; }
  44   int maybe_add_cp_cache_entry(int i) { return has_cp_cache(i) ? _cp_map[i] : add_cp_cache_entry(i); }
  45   int add_cp_cache_entry(int cp_index) {
  46     assert((cp_index & _secondary_entry_tag) == 0, "bad tag");
  47     assert(_cp_map[cp_index] == -1, "not twice on same cp_index");
  48     int cache_index = _cp_cache_map.append(cp_index);
  49     _cp_map.at_put(cp_index, cache_index);
  50     assert(cp_entry_to_cp_cache(cp_index) == cache_index, "");
  51     return cache_index;
  52   }
  53   int add_secondary_cp_cache_entry(int main_cpc_entry) {
  54     assert(main_cpc_entry < _cp_cache_map.length(), "must be earlier CP cache entry");
  55     int cache_index = _cp_cache_map.append(main_cpc_entry | _secondary_entry_tag);
  56     return cache_index;
  57   }
  58 
  59   // All the work goes in here:
  60   Rewriter(instanceKlassHandle klass, TRAPS);
  61 
  62   void compute_index_maps();
  63   void make_constant_pool_cache(TRAPS);
  64   void scan_method(methodOop m);
  65   methodHandle rewrite_jsrs(methodHandle m, TRAPS);
  66   void rewrite_Object_init(methodHandle m, TRAPS);
  67   int  rewrite_member_reference(address bcp, int offset);
  68   void rewrite_invokedynamic(address bcp, int offset, int cp_index);
  69 
  70  public:
  71   // Driver routine:
  72   static void rewrite(instanceKlassHandle klass, TRAPS);
  73 
  74   enum {
  75     _secondary_entry_tag = nth_bit(30)
  76   };
  77 };