Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 1999-2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 #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);

 }