1 /*
   2  * Copyright (c) 1998, 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
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "interpreter/bytecodes.hpp"
  27 #include "interpreter/interpreter.hpp"
  28 #include "interpreter/rewriter.hpp"
  29 #include "memory/metadataFactory.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "oops/constantPool.hpp"
  32 #include "oops/generateOopMap.hpp"
  33 #include "prims/methodHandles.hpp"
  34 #include "runtime/fieldDescriptor.inline.hpp"
  35 #include "runtime/handles.inline.hpp"
  36 
  37 // Computes a CPC map (new_index -> original_index) for constant pool entries
  38 // that are referred to by the interpreter at runtime via the constant pool cache.
  39 // Also computes a CP map (original_index -> new_index).
  40 // Marks entries in CP which require additional processing.
  41 void Rewriter::compute_index_maps() {
  42   const int length  = _pool->length();
  43   init_maps(length);
  44   bool saw_mh_symbol = false;
  45   for (int i = 0; i < length; i++) {
  46     int tag = _pool->tag_at(i).value();
  47     switch (tag) {
  48       case JVM_CONSTANT_InterfaceMethodref:
  49       case JVM_CONSTANT_Fieldref          : // fall through
  50       case JVM_CONSTANT_Methodref         : // fall through
  51         add_cp_cache_entry(i);
  52         break;
  53       case JVM_CONSTANT_Dynamic:
  54         assert(_pool->has_dynamic_constant(), "constant pool's _has_dynamic_constant flag not set");
  55         add_resolved_references_entry(i);
  56         break;
  57       case JVM_CONSTANT_String            : // fall through
  58       case JVM_CONSTANT_MethodHandle      : // fall through
  59       case JVM_CONSTANT_MethodType        : // fall through
  60         add_resolved_references_entry(i);
  61         break;
  62       case JVM_CONSTANT_Utf8:
  63         if (_pool->symbol_at(i) == vmSymbols::java_lang_invoke_MethodHandle() ||
  64             _pool->symbol_at(i) == vmSymbols::java_lang_invoke_VarHandle()) {
  65           saw_mh_symbol = true;
  66         }
  67         break;
  68     }
  69   }
  70 
  71   // Record limits of resolved reference map for constant pool cache indices
  72   record_map_limits();
  73 
  74   guarantee((int) _cp_cache_map.length() - 1 <= (int) ((u2)-1),
  75             "all cp cache indexes fit in a u2");
  76 
  77   if (saw_mh_symbol) {
  78     _method_handle_invokers.at_grow(length, 0);
  79   }
  80 }
  81 
  82 // Unrewrite the bytecodes if an error occurs.
  83 void Rewriter::restore_bytecodes() {
  84   int len = _methods->length();
  85   bool invokespecial_error = false;
  86 
  87   for (int i = len-1; i >= 0; i--) {
  88     Method* method = _methods->at(i);
  89     scan_method(method, true, &invokespecial_error);
  90     assert(!invokespecial_error, "reversing should not get an invokespecial error");
  91   }
  92 }
  93 
  94 // Creates a constant pool cache given a CPC map
  95 void Rewriter::make_constant_pool_cache(TRAPS) {
  96   ClassLoaderData* loader_data = _pool->pool_holder()->class_loader_data();
  97   ConstantPoolCache* cache =
  98       ConstantPoolCache::allocate(loader_data, _cp_cache_map,
  99                                   _invokedynamic_cp_cache_map,
 100                                   _invokedynamic_references_map, CHECK);
 101 
 102   // initialize object cache in constant pool
 103   _pool->set_cache(cache);
 104   cache->set_constant_pool(_pool());
 105 
 106   // _resolved_references is stored in pool->cache(), so need to be done after
 107   // the above lines.
 108   _pool->initialize_resolved_references(loader_data, _resolved_references_map,
 109                                         _resolved_reference_limit,
 110                                         THREAD);
 111 
 112   // Clean up constant pool cache if initialize_resolved_references() failed.
 113   if (HAS_PENDING_EXCEPTION) {
 114     MetadataFactory::free_metadata(loader_data, cache);
 115     _pool->set_cache(NULL);  // so the verifier isn't confused
 116   } else {
 117     DEBUG_ONLY(
 118     if (DumpSharedSpaces) {
 119       cache->verify_just_initialized();
 120     })
 121   }
 122 }
 123 
 124 
 125 
 126 // The new finalization semantics says that registration of
 127 // finalizable objects must be performed on successful return from the
 128 // Object.<init> constructor.  We could implement this trivially if
 129 // <init> were never rewritten but since JVMTI allows this to occur, a
 130 // more complicated solution is required.  A special return bytecode
 131 // is used only by Object.<init> to signal the finalization
 132 // registration point.  Additionally local 0 must be preserved so it's
 133 // available to pass to the registration function.  For simplicity we
 134 // require that local 0 is never overwritten so it's available as an
 135 // argument for registration.
 136 
 137 void Rewriter::rewrite_Object_init(const methodHandle& method, TRAPS) {
 138   RawBytecodeStream bcs(method);
 139   while (!bcs.is_last_bytecode()) {
 140     Bytecodes::Code opcode = bcs.raw_next();
 141     switch (opcode) {
 142       case Bytecodes::_return: *bcs.bcp() = Bytecodes::_return_register_finalizer; break;
 143 
 144       case Bytecodes::_istore:
 145       case Bytecodes::_lstore:
 146       case Bytecodes::_fstore:
 147       case Bytecodes::_dstore:
 148       case Bytecodes::_astore:
 149         if (bcs.get_index() != 0) continue;
 150 
 151         // fall through
 152       case Bytecodes::_istore_0:
 153       case Bytecodes::_lstore_0:
 154       case Bytecodes::_fstore_0:
 155       case Bytecodes::_dstore_0:
 156       case Bytecodes::_astore_0:
 157         THROW_MSG(vmSymbols::java_lang_IncompatibleClassChangeError(),
 158                   "can't overwrite local 0 in Object.<init>");
 159         break;
 160 
 161       default:
 162         break;
 163     }
 164   }
 165 }
 166 
 167 
 168 // Rewrite a classfile-order CP index into a native-order CPC index.
 169 void Rewriter::rewrite_member_reference(address bcp, int offset, bool reverse) {
 170   address p = bcp + offset;
 171   if (!reverse) {
 172     int cp_index    = Bytes::get_Java_u2(p);
 173     int  cache_index = cp_entry_to_cp_cache(cp_index);
 174     Bytes::put_native_u2(p, cache_index);
 175     if (!_method_handle_invokers.is_empty())
 176       maybe_rewrite_invokehandle(p - 1, cp_index, cache_index, reverse);
 177   } else {
 178     int cache_index = Bytes::get_native_u2(p);
 179     int pool_index = cp_cache_entry_pool_index(cache_index);
 180     Bytes::put_Java_u2(p, pool_index);
 181     if (!_method_handle_invokers.is_empty())
 182       maybe_rewrite_invokehandle(p - 1, pool_index, cache_index, reverse);
 183   }
 184 }
 185 
 186 // If the constant pool entry for invokespecial is InterfaceMethodref,
 187 // we need to add a separate cpCache entry for its resolution, because it is
 188 // different than the resolution for invokeinterface with InterfaceMethodref.
 189 // These cannot share cpCache entries.
 190 void Rewriter::rewrite_invokespecial(address bcp, int offset, bool reverse, bool* invokespecial_error) {
 191   address p = bcp + offset;
 192   if (!reverse) {
 193     int cp_index = Bytes::get_Java_u2(p);
 194     if (_pool->tag_at(cp_index).is_interface_method()) {
 195       int cache_index = add_invokespecial_cp_cache_entry(cp_index);
 196       if (cache_index != (int)(jushort) cache_index) {
 197         *invokespecial_error = true;
 198       }
 199       Bytes::put_native_u2(p, cache_index);
 200     } else {
 201       rewrite_member_reference(bcp, offset, reverse);
 202     }
 203   } else {
 204     rewrite_member_reference(bcp, offset, reverse);
 205   }
 206 }
 207 
 208 // Adjust the invocation bytecode for a signature-polymorphic method (MethodHandle.invoke, etc.)
 209 void Rewriter::maybe_rewrite_invokehandle(address opc, int cp_index, int cache_index, bool reverse) {
 210   if (!reverse) {
 211     if ((*opc) == (u1)Bytecodes::_invokevirtual ||
 212         // allow invokespecial as an alias, although it would be very odd:
 213         (*opc) == (u1)Bytecodes::_invokespecial) {
 214       assert(_pool->tag_at(cp_index).is_method(), "wrong index");
 215       // Determine whether this is a signature-polymorphic method.
 216       if (cp_index >= _method_handle_invokers.length())  return;
 217       int status = _method_handle_invokers.at(cp_index);
 218       assert(status >= -1 && status <= 1, "oob tri-state");
 219       if (status == 0) {
 220         if (_pool->klass_ref_at_noresolve(cp_index) == vmSymbols::java_lang_invoke_MethodHandle() &&
 221             MethodHandles::is_signature_polymorphic_name(SystemDictionary::MethodHandle_klass(),
 222                                                          _pool->name_ref_at(cp_index))) {
 223           // we may need a resolved_refs entry for the appendix
 224           add_invokedynamic_resolved_references_entry(cp_index, cache_index);
 225           status = +1;
 226         } else if (_pool->klass_ref_at_noresolve(cp_index) == vmSymbols::java_lang_invoke_VarHandle() &&
 227                    MethodHandles::is_signature_polymorphic_name(SystemDictionary::VarHandle_klass(),
 228                                                                 _pool->name_ref_at(cp_index))) {
 229           // we may need a resolved_refs entry for the appendix
 230           add_invokedynamic_resolved_references_entry(cp_index, cache_index);
 231           status = +1;
 232         } else {
 233           status = -1;
 234         }
 235         _method_handle_invokers.at(cp_index) = status;
 236       }
 237       // We use a special internal bytecode for such methods (if non-static).
 238       // The basic reason for this is that such methods need an extra "appendix" argument
 239       // to transmit the call site's intended call type.
 240       if (status > 0) {
 241         (*opc) = (u1)Bytecodes::_invokehandle;
 242       }
 243     }
 244   } else {
 245     // Do not need to look at cp_index.
 246     if ((*opc) == (u1)Bytecodes::_invokehandle) {
 247       (*opc) = (u1)Bytecodes::_invokevirtual;
 248       // Ignore corner case of original _invokespecial instruction.
 249       // This is safe because (a) the signature polymorphic method was final, and
 250       // (b) the implementation of MethodHandle will not call invokespecial on it.
 251     }
 252   }
 253 }
 254 
 255 
 256 void Rewriter::rewrite_invokedynamic(address bcp, int offset, bool reverse) {
 257   address p = bcp + offset;
 258   assert(p[-1] == Bytecodes::_invokedynamic, "not invokedynamic bytecode");
 259   if (!reverse) {
 260     int cp_index = Bytes::get_Java_u2(p);
 261     int cache_index = add_invokedynamic_cp_cache_entry(cp_index);
 262     int resolved_index = add_invokedynamic_resolved_references_entry(cp_index, cache_index);
 263     // Replace the trailing four bytes with a CPC index for the dynamic
 264     // call site.  Unlike other CPC entries, there is one per bytecode,
 265     // not just one per distinct CP entry.  In other words, the
 266     // CPC-to-CP relation is many-to-one for invokedynamic entries.
 267     // This means we must use a larger index size than u2 to address
 268     // all these entries.  That is the main reason invokedynamic
 269     // must have a five-byte instruction format.  (Of course, other JVM
 270     // implementations can use the bytes for other purposes.)
 271     // Note: We use native_u4 format exclusively for 4-byte indexes.
 272     Bytes::put_native_u4(p, ConstantPool::encode_invokedynamic_index(cache_index));
 273     // add the bcp in case we need to patch this bytecode if we also find a
 274     // invokespecial/InterfaceMethodref in the bytecode stream
 275     _patch_invokedynamic_bcps->push(p);
 276     _patch_invokedynamic_refs->push(resolved_index);
 277   } else {
 278     int cache_index = ConstantPool::decode_invokedynamic_index(
 279                         Bytes::get_native_u4(p));
 280     // We will reverse the bytecode rewriting _after_ adjusting them.
 281     // Adjust the cache index by offset to the invokedynamic entries in the
 282     // cpCache plus the delta if the invokedynamic bytecodes were adjusted.
 283     int adjustment = cp_cache_delta() + _first_iteration_cp_cache_limit;
 284     int cp_index = invokedynamic_cp_cache_entry_pool_index(cache_index - adjustment);
 285     assert(_pool->tag_at(cp_index).is_invoke_dynamic(), "wrong index");
 286     // zero out 4 bytes
 287     Bytes::put_Java_u4(p, 0);
 288     Bytes::put_Java_u2(p, cp_index);
 289   }
 290 }
 291 
 292 void Rewriter::patch_invokedynamic_bytecodes() {
 293   // If the end of the cp_cache is the same as after initializing with the
 294   // cpool, nothing needs to be done.  Invokedynamic bytecodes are at the
 295   // correct offsets. ie. no invokespecials added
 296   int delta = cp_cache_delta();
 297   if (delta > 0) {
 298     int length = _patch_invokedynamic_bcps->length();
 299     assert(length == _patch_invokedynamic_refs->length(),
 300            "lengths should match");
 301     for (int i = 0; i < length; i++) {
 302       address p = _patch_invokedynamic_bcps->at(i);
 303       int cache_index = ConstantPool::decode_invokedynamic_index(
 304                           Bytes::get_native_u4(p));
 305       Bytes::put_native_u4(p, ConstantPool::encode_invokedynamic_index(cache_index + delta));
 306 
 307       // invokedynamic resolved references map also points to cp cache and must
 308       // add delta to each.
 309       int resolved_index = _patch_invokedynamic_refs->at(i);
 310         assert(_invokedynamic_references_map.at(resolved_index) == cache_index,
 311              "should be the same index");
 312         _invokedynamic_references_map.at_put(resolved_index, cache_index + delta);
 313     }
 314   }
 315 }
 316 
 317 
 318 // Rewrite some ldc bytecodes to _fast_aldc
 319 void Rewriter::maybe_rewrite_ldc(address bcp, int offset, bool is_wide,
 320                                  bool reverse) {
 321   if (!reverse) {
 322     assert((*bcp) == (is_wide ? Bytecodes::_ldc_w : Bytecodes::_ldc), "not ldc bytecode");
 323     address p = bcp + offset;
 324     int cp_index = is_wide ? Bytes::get_Java_u2(p) : (u1)(*p);
 325     constantTag tag = _pool->tag_at(cp_index).value();
 326 
 327     if (tag.is_method_handle() ||
 328         tag.is_method_type() ||
 329         tag.is_string() ||
 330         (tag.is_dynamic_constant() &&
 331          // keep regular ldc interpreter logic for condy primitives
 332          is_reference_type(FieldType::basic_type(_pool->uncached_signature_ref_at(cp_index))))
 333         ) {
 334       int ref_index = cp_entry_to_resolved_references(cp_index);
 335       if (is_wide) {
 336         (*bcp) = Bytecodes::_fast_aldc_w;
 337         assert(ref_index == (u2)ref_index, "index overflow");
 338         Bytes::put_native_u2(p, ref_index);
 339       } else {
 340         (*bcp) = Bytecodes::_fast_aldc;
 341         assert(ref_index == (u1)ref_index, "index overflow");
 342         (*p) = (u1)ref_index;
 343       }
 344     }
 345   } else {
 346     Bytecodes::Code rewritten_bc =
 347               (is_wide ? Bytecodes::_fast_aldc_w : Bytecodes::_fast_aldc);
 348     if ((*bcp) == rewritten_bc) {
 349       address p = bcp + offset;
 350       int ref_index = is_wide ? Bytes::get_native_u2(p) : (u1)(*p);
 351       int pool_index = resolved_references_entry_to_pool_index(ref_index);
 352       if (is_wide) {
 353         (*bcp) = Bytecodes::_ldc_w;
 354         assert(pool_index == (u2)pool_index, "index overflow");
 355         Bytes::put_Java_u2(p, pool_index);
 356       } else {
 357         (*bcp) = Bytecodes::_ldc;
 358         assert(pool_index == (u1)pool_index, "index overflow");
 359         (*p) = (u1)pool_index;
 360       }
 361     }
 362   }
 363 }
 364 
 365 
 366 // Rewrites a method given the index_map information
 367 void Rewriter::scan_method(Method* method, bool reverse, bool* invokespecial_error) {
 368 
 369   int nof_jsrs = 0;
 370   bool has_monitor_bytecodes = false;
 371   Bytecodes::Code c;
 372 
 373   // Bytecodes and their length
 374   const address code_base = method->code_base();
 375   const int code_length = method->code_size();
 376 
 377   int bc_length;
 378   for (int bci = 0; bci < code_length; bci += bc_length) {
 379     address bcp = code_base + bci;
 380     int prefix_length = 0;
 381     c = (Bytecodes::Code)(*bcp);
 382 
 383     // Since we have the code, see if we can get the length
 384     // directly. Some more complicated bytecodes will report
 385     // a length of zero, meaning we need to make another method
 386     // call to calculate the length.
 387     bc_length = Bytecodes::length_for(c);
 388     if (bc_length == 0) {
 389       bc_length = Bytecodes::length_at(method, bcp);
 390 
 391       // length_at will put us at the bytecode after the one modified
 392       // by 'wide'. We don't currently examine any of the bytecodes
 393       // modified by wide, but in case we do in the future...
 394       if (c == Bytecodes::_wide) {
 395         prefix_length = 1;
 396         c = (Bytecodes::Code)bcp[1];
 397       }
 398     }
 399 
 400     // Continuing with an invalid bytecode will fail in the loop below.
 401     // So guarantee here.
 402     guarantee(bc_length > 0, "Verifier should have caught this invalid bytecode");
 403 
 404     switch (c) {
 405       case Bytecodes::_lookupswitch   : {
 406 #ifndef CC_INTERP
 407         Bytecode_lookupswitch bc(method, bcp);
 408         (*bcp) = (
 409           bc.number_of_pairs() < BinarySwitchThreshold
 410           ? Bytecodes::_fast_linearswitch
 411           : Bytecodes::_fast_binaryswitch
 412         );
 413 #endif
 414         break;
 415       }
 416       case Bytecodes::_fast_linearswitch:
 417       case Bytecodes::_fast_binaryswitch: {
 418 #ifndef CC_INTERP
 419         (*bcp) = Bytecodes::_lookupswitch;
 420 #endif
 421         break;
 422       }
 423 
 424       case Bytecodes::_invokespecial  : {
 425         rewrite_invokespecial(bcp, prefix_length+1, reverse, invokespecial_error);
 426         break;
 427       }
 428 
 429       case Bytecodes::_putstatic      :
 430       case Bytecodes::_putfield       : {
 431         if (!reverse) {
 432           // Check if any final field of the class given as parameter is modified
 433           // outside of initializer methods of the class. Fields that are modified
 434           // are marked with a flag. For marked fields, the compilers do not perform
 435           // constant folding (as the field can be changed after initialization).
 436           //
 437           // The check is performed after verification and only if verification has
 438           // succeeded. Therefore, the class is guaranteed to be well-formed.
 439           InstanceKlass* klass = method->method_holder();
 440           u2 bc_index = Bytes::get_Java_u2(bcp + prefix_length + 1);
 441           constantPoolHandle cp(method->constants());
 442           Symbol* ref_class_name = cp->klass_name_at(cp->klass_ref_index_at(bc_index));
 443 
 444           if (klass->name() == ref_class_name) {
 445             Symbol* field_name = cp->name_ref_at(bc_index);
 446             Symbol* field_sig = cp->signature_ref_at(bc_index);
 447 
 448             fieldDescriptor fd;
 449             if (klass->find_field(field_name, field_sig, &fd) != NULL) {
 450               if (fd.access_flags().is_final()) {
 451                 if (fd.access_flags().is_static()) {
 452                   if (!method->is_class_initializer()) {
 453                     fd.set_has_initialized_final_update(true);
 454                   }
 455                 } else {
 456                   if (!method->is_object_constructor()) {
 457                     fd.set_has_initialized_final_update(true);
 458                   }
 459                 }
 460               }
 461             }
 462           }
 463         }
 464       }
 465       // fall through
 466       case Bytecodes::_getstatic      : // fall through
 467       case Bytecodes::_getfield       : // fall through
 468       case Bytecodes::_withfield     : // fall through but may require more checks for correctness
 469       case Bytecodes::_invokevirtual  : // fall through
 470       case Bytecodes::_invokestatic   :
 471       case Bytecodes::_invokeinterface:
 472       case Bytecodes::_invokehandle   : // if reverse=true
 473         rewrite_member_reference(bcp, prefix_length+1, reverse);
 474         break;
 475       case Bytecodes::_invokedynamic:
 476         rewrite_invokedynamic(bcp, prefix_length+1, reverse);
 477         break;
 478       case Bytecodes::_ldc:
 479       case Bytecodes::_fast_aldc:  // if reverse=true
 480         maybe_rewrite_ldc(bcp, prefix_length+1, false, reverse);
 481         break;
 482       case Bytecodes::_ldc_w:
 483       case Bytecodes::_fast_aldc_w:  // if reverse=true
 484         maybe_rewrite_ldc(bcp, prefix_length+1, true, reverse);
 485         break;
 486       case Bytecodes::_jsr            : // fall through
 487       case Bytecodes::_jsr_w          : nof_jsrs++;                   break;
 488       case Bytecodes::_monitorenter   : // fall through
 489       case Bytecodes::_monitorexit    : has_monitor_bytecodes = true; break;
 490 
 491       default: break;
 492     }
 493   }
 494 
 495   // Update access flags
 496   if (has_monitor_bytecodes) {
 497     method->set_has_monitor_bytecodes();
 498   }
 499 
 500   // The present of a jsr bytecode implies that the method might potentially
 501   // have to be rewritten, so we run the oopMapGenerator on the method
 502   if (nof_jsrs > 0) {
 503     method->set_has_jsrs();
 504     // Second pass will revisit this method.
 505     assert(method->has_jsrs(), "didn't we just set this?");
 506   }
 507 }
 508 
 509 // After constant pool is created, revisit methods containing jsrs.
 510 methodHandle Rewriter::rewrite_jsrs(const methodHandle& method, TRAPS) {
 511   ResourceMark rm(THREAD);
 512   ResolveOopMapConflicts romc(method);
 513   methodHandle new_method = romc.do_potential_rewrite(CHECK_(methodHandle()));
 514   // Update monitor matching info.
 515   if (romc.monitor_safe()) {
 516     new_method->set_guaranteed_monitor_matching();
 517   }
 518 
 519   return new_method;
 520 }
 521 
 522 void Rewriter::rewrite_bytecodes(TRAPS) {
 523   assert(_pool->cache() == NULL, "constant pool cache must not be set yet");
 524 
 525   // determine index maps for Method* rewriting
 526   compute_index_maps();
 527 
 528   if (RegisterFinalizersAtInit && _klass->name() == vmSymbols::java_lang_Object()) {
 529     bool did_rewrite = false;
 530     int i = _methods->length();
 531     while (i-- > 0) {
 532       Method* method = _methods->at(i);
 533       if (method->intrinsic_id() == vmIntrinsics::_Object_init) {
 534         // rewrite the return bytecodes of Object.<init> to register the
 535         // object for finalization if needed.
 536         methodHandle m(THREAD, method);
 537         rewrite_Object_init(m, CHECK);
 538         did_rewrite = true;
 539         break;
 540       }
 541     }
 542     assert(did_rewrite, "must find Object::<init> to rewrite it");
 543   }
 544 
 545   // rewrite methods, in two passes
 546   int len = _methods->length();
 547   bool invokespecial_error = false;
 548 
 549   for (int i = len-1; i >= 0; i--) {
 550     Method* method = _methods->at(i);
 551     scan_method(method, false, &invokespecial_error);
 552     if (invokespecial_error) {
 553       // If you get an error here, there is no reversing bytecodes
 554       // This exception is stored for this class and no further attempt is
 555       // made at verifying or rewriting.
 556       THROW_MSG(vmSymbols::java_lang_InternalError(),
 557                 "This classfile overflows invokespecial for interfaces "
 558                 "and cannot be loaded");
 559       return;
 560      }
 561   }
 562 
 563   // May have to fix invokedynamic bytecodes if invokestatic/InterfaceMethodref
 564   // entries had to be added.
 565   patch_invokedynamic_bytecodes();
 566 }
 567 
 568 void Rewriter::rewrite(InstanceKlass* klass, TRAPS) {
 569   if (!DumpSharedSpaces) {
 570     assert(!klass->is_shared(), "archive methods must not be rewritten at run time");
 571   }
 572   ResourceMark rm(THREAD);
 573   Rewriter     rw(klass, klass->constants(), klass->methods(), CHECK);
 574   // (That's all, folks.)
 575 }
 576 
 577 Rewriter::Rewriter(InstanceKlass* klass, const constantPoolHandle& cpool, Array<Method*>* methods, TRAPS)
 578   : _klass(klass),
 579     _pool(cpool),
 580     _methods(methods),
 581     _cp_map(cpool->length()),
 582     _cp_cache_map(cpool->length() / 2),
 583     _reference_map(cpool->length()),
 584     _resolved_references_map(cpool->length() / 2),
 585     _invokedynamic_references_map(cpool->length() / 2),
 586     _method_handle_invokers(cpool->length()),
 587     _invokedynamic_cp_cache_map(cpool->length() / 4)
 588 {
 589 
 590   // Rewrite bytecodes - exception here exits.
 591   rewrite_bytecodes(CHECK);
 592 
 593   // Stress restoring bytecodes
 594   if (StressRewriter) {
 595     restore_bytecodes();
 596     rewrite_bytecodes(CHECK);
 597   }
 598 
 599   // allocate constant pool cache, now that we've seen all the bytecodes
 600   make_constant_pool_cache(THREAD);
 601 
 602   // Restore bytecodes to their unrewritten state if there are exceptions
 603   // rewriting bytecodes or allocating the cpCache
 604   if (HAS_PENDING_EXCEPTION) {
 605     restore_bytecodes();
 606     return;
 607   }
 608 
 609   // Relocate after everything, but still do this under the is_rewritten flag,
 610   // so methods with jsrs in custom class lists in aren't attempted to be
 611   // rewritten in the RO section of the shared archive.
 612   // Relocated bytecodes don't have to be restored, only the cp cache entries
 613   int len = _methods->length();
 614   for (int i = len-1; i >= 0; i--) {
 615     methodHandle m(THREAD, _methods->at(i));
 616 
 617     if (m->has_jsrs()) {
 618       m = rewrite_jsrs(m, THREAD);
 619       // Restore bytecodes to their unrewritten state if there are exceptions
 620       // relocating bytecodes.  If some are relocated, that is ok because that
 621       // doesn't affect constant pool to cpCache rewriting.
 622       if (HAS_PENDING_EXCEPTION) {
 623         restore_bytecodes();
 624         return;
 625       }
 626       // Method might have gotten rewritten.
 627       methods->at_put(i, m());
 628     }
 629   }
 630 }