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 /*

  * Copyright (c) 1998, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 # include "incls/_precompiled.incl"

 # include "incls/_rewriter.cpp.incl"

 // Computes a CPC map (new_index -> original_index) for constant pool entries

 // that are referred to by the interpreter at runtime via the constant pool cache.

 // Also computes a CP map (original_index -> new_index).

 // Marks entries in CP which require additional processing.

 void Rewriter::compute_index_maps() {

   const int length  = _pool->length();

   init_cp_map(length);

   for (int i = 0; i < length; i++) {

     int tag = _pool->tag_at(i).value();

     switch (tag) {

       case JVM_CONSTANT_InterfaceMethodref:

       case JVM_CONSTANT_Fieldref          : // fall through

       case JVM_CONSTANT_Methodref         : // fall through

         add_cp_cache_entry(i);

         break;

     }

   }

   guarantee((int)_cp_cache_map.length()-1 <= (int)((u2)-1),

             "all cp cache indexes fit in a u2");

 }

 // Creates a constant pool cache given a CPC map

 // This creates the constant pool cache initially in a state

 // that is unsafe for concurrent GC processing but sets it to

 // a safe mode before the constant pool cache is returned.

 void Rewriter::make_constant_pool_cache(TRAPS) {

   const int length = _cp_cache_map.length();

   constantPoolCacheOop cache =

       oopFactory::new_constantPoolCache(length, methodOopDesc::IsUnsafeConc, CHECK);

   cache->initialize(_cp_cache_map);

   _pool->set_cache(cache);

   cache->set_constant_pool(_pool());

 }

 // The new finalization semantics says that registration of

 // finalizable objects must be performed on successful return from the

 // Object.<init> constructor.  We could implement this trivially if

 // <init> were never rewritten but since JVMTI allows this to occur, a

 // more complicated solution is required.  A special return bytecode

 // is used only by Object.<init> to signal the finalization

 // registration point.  Additionally local 0 must be preserved so it's

 // available to pass to the registration function.  For simplicty we

 // require that local 0 is never overwritten so it's available as an

 // argument for registration.

 void Rewriter::rewrite_Object_init(methodHandle method, TRAPS) {

   RawBytecodeStream bcs(method);

   while (!bcs.is_last_bytecode()) {

     Bytecodes::Code opcode = bcs.raw_next();

     switch (opcode) {

       case Bytecodes::_return: *bcs.bcp() = Bytecodes::_return_register_finalizer; break;

       case Bytecodes::_istore:

       case Bytecodes::_lstore:

       case Bytecodes::_fstore:

       case Bytecodes::_dstore:

       case Bytecodes::_astore:

         if (bcs.get_index() != 0) continue;

         // fall through

       case Bytecodes::_istore_0:

       case Bytecodes::_lstore_0:

       case Bytecodes::_fstore_0:

       case Bytecodes::_dstore_0:

       case Bytecodes::_astore_0:

         THROW_MSG(vmSymbols::java_lang_IncompatibleClassChangeError(),

                   "can't overwrite local 0 in Object.<init>");

         break;

     }

   }

 }

 // Rewrite a classfile-order CP index into a native-order CPC index.

 void Rewriter::rewrite_member_reference(address bcp, int offset) {

   address p = bcp + offset;

   int  cp_index    = Bytes::get_Java_u2(p);

   int  cache_index = cp_entry_to_cp_cache(cp_index);

   Bytes::put_native_u2(p, cache_index);

 }

 void Rewriter::rewrite_invokedynamic(address bcp, int offset) {

   address p = bcp + offset;

   assert(p[-1] == Bytecodes::_invokedynamic, "");

   int cp_index = Bytes::get_Java_u2(p);

   int cpc  = maybe_add_cp_cache_entry(cp_index);  // add lazily

   int cpc2 = add_secondary_cp_cache_entry(cpc);

   // Replace the trailing four bytes with a CPC index for the dynamic

   // call site.  Unlike other CPC entries, there is one per bytecode,

   // not just one per distinct CP entry.  In other words, the

   // CPC-to-CP relation is many-to-one for invokedynamic entries.

   // This means we must use a larger index size than u2 to address

   // all these entries.  That is the main reason invokedynamic

   // must have a five-byte instruction format.  (Of course, other JVM

   // implementations can use the bytes for other purposes.)

   Bytes::put_native_u4(p, constantPoolCacheOopDesc::encode_secondary_index(cpc2));

   // Note: We use native_u4 format exclusively for 4-byte indexes.

 }

 // Rewrites a method given the index_map information

 void Rewriter::scan_method(methodOop method) {

   int nof_jsrs = 0;

   bool has_monitor_bytecodes = false;

   {

     // We cannot tolerate a GC in this block, because we've

     // cached the bytecodes in 'code_base'. If the methodOop

     // moves, the bytecodes will also move.

     No_Safepoint_Verifier nsv;

     Bytecodes::Code c;

     // Bytecodes and their length

     const address code_base = method->code_base();

     const int code_length = method->code_size();

     int bc_length;

     for (int bci = 0; bci < code_length; bci += bc_length) {

       address bcp = code_base + bci;

       int prefix_length = 0;

       c = (Bytecodes::Code)(*bcp);

       // Since we have the code, see if we can get the length

       // directly. Some more complicated bytecodes will report

       // a length of zero, meaning we need to make another method

       // call to calculate the length.

       bc_length = Bytecodes::length_for(c);

       if (bc_length == 0) {

         bc_length = Bytecodes::length_at(bcp);

         // length_at will put us at the bytecode after the one modified

         // by 'wide'. We don't currently examine any of the bytecodes

         // modified by wide, but in case we do in the future...

         if (c == Bytecodes::_wide) {

           prefix_length = 1;

           c = (Bytecodes::Code)bcp[1];

         }

       }

       assert(bc_length != 0, "impossible bytecode length");

       switch (c) {

         case Bytecodes::_lookupswitch   : {

 #ifndef CC_INTERP

           Bytecode_lookupswitch* bc = Bytecode_lookupswitch_at(bcp);

           (*bcp) = (

             bc->number_of_pairs() < BinarySwitchThreshold

             ? Bytecodes::_fast_linearswitch

             : Bytecodes::_fast_binaryswitch

           );

 #endif

           break;

         }

         case Bytecodes::_getstatic      : // fall through

         case Bytecodes::_putstatic      : // fall through

         case Bytecodes::_getfield       : // fall through

         case Bytecodes::_putfield       : // fall through

         case Bytecodes::_invokevirtual  : // fall through

         case Bytecodes::_invokespecial  : // fall through

         case Bytecodes::_invokestatic   :

         case Bytecodes::_invokeinterface:

           rewrite_member_reference(bcp, prefix_length+1);

           break;

         case Bytecodes::_invokedynamic:

           rewrite_invokedynamic(bcp, prefix_length+1);

           break;

         case Bytecodes::_jsr            : // fall through

         case Bytecodes::_jsr_w          : nof_jsrs++;                   break;

         case Bytecodes::_monitorenter   : // fall through

         case Bytecodes::_monitorexit    : has_monitor_bytecodes = true; break;

       }

     }

   }

   // Update access flags

   if (has_monitor_bytecodes) {

     method->set_has_monitor_bytecodes();

   }

   // The present of a jsr bytecode implies that the method might potentially

   // have to be rewritten, so we run the oopMapGenerator on the method

   if (nof_jsrs > 0) {

     method->set_has_jsrs();

     // Second pass will revisit this method.

     assert(method->has_jsrs(), "");

   }

 }

 // After constant pool is created, revisit methods containing jsrs.

 methodHandle Rewriter::rewrite_jsrs(methodHandle method, TRAPS) {

   ResolveOopMapConflicts romc(method);

   methodHandle original_method = method;

   method = romc.do_potential_rewrite(CHECK_(methodHandle()));

   if (method() != original_method()) {

     // Insert invalid bytecode into original methodOop and set

     // interpreter entrypoint, so that a executing this method

     // will manifest itself in an easy recognizable form.

     address bcp = original_method->bcp_from(0);

     *bcp = (u1)Bytecodes::_shouldnotreachhere;

     int kind = Interpreter::method_kind(original_method);

     original_method->set_interpreter_kind(kind);

   }

   // Update monitor matching info.

   if (romc.monitor_safe()) {

     method->set_guaranteed_monitor_matching();

   }

   return method;

 }

 void Rewriter::rewrite(instanceKlassHandle klass, TRAPS) {

   ResourceMark rm(THREAD);

   Rewriter     rw(klass, klass->constants(), klass->methods(), CHECK);

   // (That's all, folks.)

 }

 void Rewriter::rewrite(instanceKlassHandle klass, constantPoolHandle cpool, objArrayHandle methods, TRAPS) {

   ResourceMark rm(THREAD);

   Rewriter     rw(klass, cpool, methods, CHECK);

   // (That's all, folks.)

 }

 Rewriter::Rewriter(instanceKlassHandle klass, constantPoolHandle cpool, objArrayHandle methods, TRAPS)

   : _klass(klass),

     _pool(cpool),

     _methods(methods)

 {

   assert(_pool->cache() == NULL, "constant pool cache must not be set yet");

   // determine index maps for methodOop rewriting

   compute_index_maps();

   if (RegisterFinalizersAtInit && _klass->name() == vmSymbols::java_lang_Object()) {

     bool did_rewrite = false;

     int i = _methods->length();

     while (i-- > 0) {

       methodOop method = (methodOop)_methods->obj_at(i);

       if (method->intrinsic_id() == vmIntrinsics::_Object_init) {

         // rewrite the return bytecodes of Object.<init> to register the

         // object for finalization if needed.

         methodHandle m(THREAD, method);

         rewrite_Object_init(m, CHECK);

         did_rewrite = true;

         break;

       }

     }

     assert(did_rewrite, "must find Object::<init> to rewrite it");

   }

   // rewrite methods, in two passes

   int i, len = _methods->length();

   for (i = len; --i >= 0; ) {

     methodOop method = (methodOop)_methods->obj_at(i);

     scan_method(method);

   }

   // allocate constant pool cache, now that we've seen all the bytecodes

   make_constant_pool_cache(CHECK);

   for (i = len; --i >= 0; ) {

     methodHandle m(THREAD, (methodOop)_methods->obj_at(i));

     if (m->has_jsrs()) {

       m = rewrite_jsrs(m, CHECK);

       // Method might have gotten rewritten.

       _methods->obj_at_put(i, m());

     }

     // Set up method entry points for compiler and interpreter.

     m->link_method(m, CHECK);

 #ifdef ASSERT

     if (StressMethodComparator) {

       static int nmc = 0;

       for (int j = i; j >= 0 && j >= i-4; j--) {

         if ((++nmc % 1000) == 0)  tty->print_cr("Have run MethodComparator %d times...", nmc);

         bool z = MethodComparator::methods_EMCP(m(), (methodOop)_methods->obj_at(j));

         if (j == i && !z) {

           tty->print("MethodComparator FAIL: "); m->print(); m->print_codes();

           assert(z, "method must compare equal to itself");

         }

       }

     }

 #endif //ASSERT

   }

 }