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 * 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.

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 */

#include "incls/_precompiled.incl"

#include "incls/_ciField.cpp.incl"

// ciField

//

// This class represents the result of a field lookup in the VM.

// The lookup may not succeed, in which case the information in

// the ciField will be incomplete.

// The ciObjectFactory cannot create circular data structures in one query.

// To avoid vicious circularities, we initialize ciField::_type to NULL

// for reference types and derive it lazily from the ciField::_signature.

// Primitive types are eagerly initialized, and basic layout queries

// can succeed without initialization, using only the BasicType of the field.

// Notes on bootstrapping and shared CI objects:  A field is shared if and

// only if it is (a) non-static and (b) declared by a shared instance klass.

// This allows non-static field lists to be cached on shared types.

// Because the _type field is lazily initialized, however, there is a

// special restriction that a shared field cannot cache an unshared type.

// This puts a small performance penalty on shared fields with unshared

// types, such as StackTraceElement[] Throwable.stackTrace.

// (Throwable is shared because ClassCastException is shared, but

// StackTraceElement is not presently shared.)

// It is not a vicious circularity for a ciField to recursively create

// the ciSymbols necessary to represent its name and signature.

// Therefore, these items are created eagerly, and the name and signature

// of a shared field are themselves shared symbols.  This somewhat

// pollutes the set of shared CI objects:  It grows from 50 to 93 items,

// with all of the additional 43 being uninteresting shared ciSymbols.

// This adds at most one step to the binary search, an amount which

// decreases for complex compilation tasks.

// ------------------------------------------------------------------

// ciField::ciField

ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with(NULL) {

  ASSERT_IN_VM;

  CompilerThread *thread = CompilerThread::current();

  assert(ciObjectFactory::is_initialized(), "not a shared field");

  assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constan-pool");

  _cp_index = index;

  constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());

  // Get the field's name, signature, and type.

  symbolHandle name  (thread, cpool->name_ref_at(index));

  _name = ciEnv::current(thread)->get_object(name())->as_symbol();

  int nt_index = cpool->name_and_type_ref_index_at(index);

  int sig_index = cpool->signature_ref_index_at(nt_index);

  symbolHandle signature (thread, cpool->symbol_at(sig_index));

  _signature = ciEnv::current(thread)->get_object(signature())->as_symbol();

  BasicType field_type = FieldType::basic_type(signature());

  // If the field is a pointer type, get the klass of the

  // field.

  if (field_type == T_OBJECT || field_type == T_ARRAY) {

    bool ignore;

    // This is not really a class reference; the index always refers to the

    // field's type signature, as a symbol.  Linkage checks do not apply.

    _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);

  } else {

    _type = ciType::make(field_type);

  }

  _name = (ciSymbol*)ciEnv::current(thread)->get_object(name());

  // Get the field's declared holder.

  //

  // Note: we actually create a ciInstanceKlass for this klass,

  // even though we may not need to.

  int holder_index = cpool->klass_ref_index_at(index);

  bool holder_is_accessible;

  ciInstanceKlass* declared_holder =

    ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,

                                               holder_is_accessible,

                                               klass)->as_instance_klass();

  // The declared holder of this field may not have been loaded.

  // Bail out with partial field information.

  if (!holder_is_accessible) {

    // _cp_index and _type have already been set.

    // The default values for _flags and _constant_value will suffice.

    // We need values for _holder, _offset,  and _is_constant,

    _holder = declared_holder;

    _offset = -1;

    _is_constant = false;

    return;

  }

  instanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();

  // Perform the field lookup.

  fieldDescriptor field_desc;

  klassOop canonical_holder =

    loaded_decl_holder->find_field(name(), signature(), &field_desc);

  if (canonical_holder == NULL) {

    // Field lookup failed.  Will be detected by will_link.

    _holder = declared_holder;

    _offset = -1;

    _is_constant = false;

    return;

  }

  assert(canonical_holder == field_desc.field_holder(), "just checking");

  initialize_from(&field_desc);

}

ciField::ciField(fieldDescriptor *fd): _known_to_link_with(NULL) {

  ASSERT_IN_VM;

  _cp_index = -1;

  // Get the field's name, signature, and type.

  ciEnv* env = CURRENT_ENV;

  _name = env->get_object(fd->name())->as_symbol();

  _signature = env->get_object(fd->signature())->as_symbol();

  BasicType field_type = fd->field_type();

  // If the field is a pointer type, get the klass of the

  // field.

  if (field_type == T_OBJECT || field_type == T_ARRAY) {

    _type = NULL;  // must call compute_type on first access

  } else {

    _type = ciType::make(field_type);

  }

  initialize_from(fd);

  // Either (a) it is marked shared, or else (b) we are done bootstrapping.

  assert(is_shared() || ciObjectFactory::is_initialized(),

         "bootstrap classes must not create & cache unshared fields");

}

static bool trust_final_non_static_fields(ciInstanceKlass* holder) {

  if (holder == NULL)

    return false;

  if (holder->name() == ciSymbol::java_lang_System())

    // Never trust strangely unstable finals:  System.out, etc.

    return false;

  // Even if general trusting is disabled, trust system-built closures in these packages.

  if (holder->is_in_package("java/dyn") || holder->is_in_package("sun/dyn"))

    return true;

  return TrustFinalNonStaticFields;

}

void ciField::initialize_from(fieldDescriptor* fd) {

  // Get the flags, offset, and canonical holder of the field.

  _flags = ciFlags(fd->access_flags());

  _offset = fd->offset();

  _holder = CURRENT_ENV->get_object(fd->field_holder())->as_instance_klass();

  // Check to see if the field is constant.

  if (_holder->is_initialized() && this->is_final()) {

    if (!this->is_static()) {

      // A field can be constant if it's a final static field or if it's

      // a final non-static field of a trusted class ({java,sun}.dyn).

      if (trust_final_non_static_fields(_holder)) {

        _is_constant = true;

        return;

      }

      _is_constant = false;

      return;

    }

    // This field just may be constant.  The only cases where it will

    // not be constant are:

    //

    // 1. The field holds a non-perm-space oop.  The field is, strictly

    //    speaking, constant but we cannot embed non-perm-space oops into

    //    generated code.  For the time being we need to consider the

    //    field to be not constant.

    // 2. The field is a *special* static&final field whose value

    //    may change.  The three examples are java.lang.System.in,

    //    java.lang.System.out, and java.lang.System.err.

    klassOop k = _holder->get_klassOop();

    assert( SystemDictionary::System_klass() != NULL, "Check once per vm");

    if( k == SystemDictionary::System_klass() ) {

      // Check offsets for case 2: System.in, System.out, or System.err

      if( _offset == java_lang_System::in_offset_in_bytes()  ||

          _offset == java_lang_System::out_offset_in_bytes() ||

          _offset == java_lang_System::err_offset_in_bytes() ) {

        _is_constant = false;

        return;

      }

    }

    _is_constant = true;

    switch(type()->basic_type()) {

    case T_BYTE:

      _constant_value = ciConstant(type()->basic_type(), k->byte_field(_offset));

      break;

    case T_CHAR:

      _constant_value = ciConstant(type()->basic_type(), k->char_field(_offset));

      break;

    case T_SHORT:

      _constant_value = ciConstant(type()->basic_type(), k->short_field(_offset));

      break;

    case T_BOOLEAN:

      _constant_value = ciConstant(type()->basic_type(), k->bool_field(_offset));

      break;

    case T_INT:

      _constant_value = ciConstant(type()->basic_type(), k->int_field(_offset));

      break;

    case T_FLOAT:

      _constant_value = ciConstant(k->float_field(_offset));

      break;

    case T_DOUBLE:

      _constant_value = ciConstant(k->double_field(_offset));

      break;

    case T_LONG:

      _constant_value = ciConstant(k->long_field(_offset));

      break;

    case T_OBJECT:

    case T_ARRAY:

      {

        oop o = k->obj_field(_offset);

        // A field will be "constant" if it is known always to be

        // a non-null reference to an instance of a particular class,

        // or to a particular array.  This can happen even if the instance

        // or array is not perm.  In such a case, an "unloaded" ciArray

        // or ciInstance is created.  The compiler may be able to use

        // information about the object's class (which is exact) or length.

        if (o == NULL) {

          _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());

        } else {

          _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));

          assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");

        }

      }

    }

  } else {

    _is_constant = false;

  }

}

// ------------------------------------------------------------------

// ciField::compute_type

//

// Lazily compute the type, if it is an instance klass.

ciType* ciField::compute_type() {

  GUARDED_VM_ENTRY(return compute_type_impl();)

}

ciType* ciField::compute_type_impl() {

  ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, _signature, false);

  if (!type->is_primitive_type() && is_shared()) {

    // We must not cache a pointer to an unshared type, in a shared field.

    bool type_is_also_shared = false;

    if (type->is_type_array_klass()) {

      type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped

    } else if (type->is_instance_klass()) {

      type_is_also_shared = type->as_instance_klass()->is_shared();

    } else {

      // Currently there is no 'shared' query for array types.

      type_is_also_shared = !ciObjectFactory::is_initialized();

    }

    if (!type_is_also_shared)

      return type;              // Bummer.

  }

  _type = type;

  return type;

}

// ------------------------------------------------------------------

// ciField::will_link

//

// Can a specific access to this field be made without causing

// link errors?

bool ciField::will_link(ciInstanceKlass* accessing_klass,

                        Bytecodes::Code bc) {

  VM_ENTRY_MARK;

  if (_offset == -1) {

    // at creation we couldn't link to our holder so we need to

    // maintain that stance, otherwise there's no safe way to use this

    // ciField.

    return false;

  }

  if (_known_to_link_with == accessing_klass) {

    return true;

  }

  FieldAccessInfo result;

  constantPoolHandle c_pool(THREAD,

                         accessing_klass->get_instanceKlass()->constants());

  LinkResolver::resolve_field(result, c_pool, _cp_index,

                              Bytecodes::java_code(bc),

                              true, false, KILL_COMPILE_ON_FATAL_(false));

  // update the hit-cache, unless there is a problem with memory scoping:

  if (accessing_klass->is_shared() || !is_shared())

    _known_to_link_with = accessing_klass;

  return true;

}

// ------------------------------------------------------------------

// ciField::print

void ciField::print() {

  tty->print("<ciField ");

  _holder->print_name();

  tty->print(".");

  _name->print_symbol();

  tty->print(" offset=%d type=", _offset);

  if (_type != NULL) _type->print_name();

  else               tty->print("(reference)");

  tty->print(" is_constant=%s", bool_to_str(_is_constant));

  if (_is_constant) {

    tty->print(" constant_value=");

    _constant_value.print();

  }

  tty->print(">");

}

// ------------------------------------------------------------------

// ciField::print_name_on

//

// Print the name of this field

void ciField::print_name_on(outputStream* st) {

  name()->print_symbol_on(st);

}