/*

 * Copyright (c) 1999, 2018, 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.

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 */

#include "precompiled.hpp"

#include "ci/ciField.hpp"

#include "ci/ciInstanceKlass.hpp"

#include "ci/ciUtilities.inline.hpp"

#include "classfile/systemDictionary.hpp"

#include "gc/shared/collectedHeap.inline.hpp"

#include "interpreter/linkResolver.hpp"

#include "memory/universe.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/fieldDescriptor.hpp"

#include "runtime/handles.inline.hpp"

// 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_put(NULL), _known_to_link_with_get(NULL) {

  ASSERT_IN_VM;

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

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

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

  Symbol* name  = cpool->name_ref_at(index);

  int nt_index = cpool->name_and_type_ref_index_at(index);

  int sig_index = cpool->signature_ref_index_at(nt_index);

  Symbol* signature = cpool->symbol_at(sig_index);

  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.

  } else {

    _type = ciType::make(field_type);

  }

  // 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;

                                                                                holder_is_accessible,

                                                                                klass);

  if (generic_declared_holder->is_array_klass()) {

    // If the declared holder of the field is an array class, assume that

    // the canonical holder of that field is java.lang.Object. Arrays

    // do not have fields; java.lang.Object is the only supertype of an

    // array type that can declare fields and is therefore the canonical

    // holder of the array type.

    //

    // Furthermore, the compilers assume that java.lang.Object does not

    // have any fields. Therefore, the field is not looked up. Instead,

    // the method returns partial information that will trigger special

    // handling in ciField::will_link and will result in a

    // java.lang.NoSuchFieldError exception being thrown by the compiled

    // code (the expected behavior in this case).

    _offset = -1;

    _is_constant = false;

    return;

  }

  ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();

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

  // Bail out with partial field information.

  if (!holder_is_accessible) {

    // _type has 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;

  Klass* 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;

  }

  // Access check based on declared_holder. canonical_holder should not be used

  // to check access because it can erroneously succeed. If this check fails,

  // propagate the declared holder to will_link() which in turn will bail out

  // compilation for this field access.

    _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_put(NULL), _known_to_link_with_get(NULL) {

  ASSERT_IN_VM;

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

  ciEnv* env = CURRENT_ENV;

  _name = env->get_symbol(fd->name());

  _signature = env->get_symbol(fd->signature());

  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/lang/invoke") || holder->is_in_package("sun/invoke"))

    return true;

  // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,

  // so there is no hacking of finals going on with them.

  if (holder->is_anonymous())

    return true;

  // Trust final fields in all boxed classes

  if (holder->is_box_klass())

    return true;

  // Trust final fields in String

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

    return true;

  // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one

  // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.

  if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||

      holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||

      holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||

      holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {

    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();

  Klass* field_holder = fd->field_holder();

  assert(field_holder != NULL, "null field_holder");

  _holder = CURRENT_ENV->get_instance_klass(field_holder);

  // Check to see if the field is constant.

  Klass* k = _holder->get_Klass();

  bool is_stable_field = FoldStableValues && is_stable();

  if ((is_final() && !has_initialized_final_update()) || is_stable_field) {

    if (is_static()) {

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

      // not be constant is when 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.

      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;

    } else {

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

      // it's a final non-static field of a trusted class (classes in

      // java.lang.invoke and sun.invoke packages and subpackages).

      _is_constant = is_stable_field || trust_final_non_static_fields(_holder);

    }

  } else {

    // For CallSite objects treat the target field as a compile time constant.

    assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");

    if (k == SystemDictionary::CallSite_klass() &&

        _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {

      assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");

      _is_constant = true;

    } else {

      // Non-final & non-stable fields are not constants.

      _is_constant = false;

    }

  }

}

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

// ciField::constant_value

// Get the constant value of a this static field.

ciConstant ciField::constant_value() {

  assert(is_static() && is_constant(), "illegal call to constant_value()");

  if (!_holder->is_initialized()) {

    return ciConstant(); // Not initialized yet

  }

  if (_constant_value.basic_type() == T_ILLEGAL) {

    // Static fields are placed in mirror objects.

    VM_ENTRY_MARK;

    ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());

    _constant_value = mirror->field_value_impl(type()->basic_type(), offset());

  }

  if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {

    return ciConstant();

  }

  return _constant_value;

}

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

// ciField::constant_value_of

// Get the constant value of non-static final field in the given object.

ciConstant ciField::constant_value_of(ciObject* object) {

  assert(!is_static() && is_constant(), "only if field is non-static constant");

  assert(object->is_instance(), "must be instance");

  ciConstant field_value = object->as_instance()->field_value(this);

  if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {

    return ciConstant();

  }

  return field_value;

}

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

// 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, constantPoolHandle(), _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(ciMethod* accessing_method,

                        Bytecodes::Code bc) {

  VM_ENTRY_MARK;

  assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||

         bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,

         "unexpected bytecode");

  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;

  }

  // Check for static/nonstatic mismatch

  bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);

  if (is_static != this->is_static()) {

    return false;

  }

  // Get and put can have different accessibility rules

  bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);

  if (is_put) {

    if (_known_to_link_with_put == accessing_method) {

      return true;

    }

  } else {

    if (_known_to_link_with_get == accessing_method->holder()) {

      return true;

    }

  }

  LinkInfo link_info(_holder->get_instanceKlass(),

                     _name->get_symbol(), _signature->get_symbol(),

                     accessing_method->get_Method());

  fieldDescriptor result;

  LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));

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

  if (accessing_method->holder()->is_shared() || !is_shared()) {

    if (is_put) {

      _known_to_link_with_put = accessing_method;

    } else {

      _known_to_link_with_get = accessing_method->holder();

    }

  }

  return true;

}

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

// ciField::print

void ciField::print() {

  tty->print("<ciField name=");

  _holder->print_name();

  tty->print(".");

  _name->print_symbol();

  tty->print(" signature=");

  _signature->print_symbol();

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

  if (_type != NULL)

    _type->print_name();

  else

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

  tty->print(" flags=%04x", flags().as_int());

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

  if (_is_constant && is_static()) {

    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);

}