/*

 * 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

 * questions.

 *

 */

# 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

      case JVM_CONSTANT_MethodHandle      : // fall through

      case JVM_CONSTANT_MethodType        : // 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.

}

// Rewrite some ldc bytecodes to _fast_aldc

void Rewriter::maybe_rewrite_ldc(address bcp, int offset, bool is_wide) {

  assert((*bcp) == (is_wide ? Bytecodes::_ldc_w : Bytecodes::_ldc), "");

  address p = bcp + offset;

  int cp_index = is_wide ? Bytes::get_Java_u2(p) : (u1)(*p);

  constantTag tag = _pool->tag_at(cp_index).value();

  if (tag.is_method_handle() || tag.is_method_type()) {

    int cache_index = cp_entry_to_cp_cache(cp_index);

    if (is_wide) {

      (*bcp) = Bytecodes::_fast_aldc_w;

      assert(cache_index == (u2)cache_index, "");

      Bytes::put_native_u2(p, cache_index);

    } else {

      (*bcp) = Bytecodes::_fast_aldc;

      assert(cache_index == (u1)cache_index, "");

      (*p) = (u1)cache_index;

    }

  }

}

// 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::_ldc:

          maybe_rewrite_ldc(bcp, prefix_length+1, false);

          break;

        case Bytecodes::_ldc_w:

          maybe_rewrite_ldc(bcp, prefix_length+1, true);

          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

  }

}