/* * Copyright (c) 1999, 2011, 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 "precompiled.hpp" #include "ci/ciField.hpp" #include "ci/ciInstanceKlass.hpp" #include "ci/ciUtilities.hpp" #include "classfile/systemDictionary.hpp" #include "gc_interface/collectedHeap.inline.hpp" #include "interpreter/linkResolver.hpp" #include "memory/universe.inline.hpp" #include "oops/oop.inline.hpp" #include "oops/oop.inline2.hpp" #include "runtime/fieldDescriptor.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(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. Symbol* name = cpool->name_ref_at(index); _name = ciEnv::current(thread)->get_symbol(name); 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); _signature = ciEnv::current(thread)->get_symbol(signature); 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_symbol(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_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; 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 (classes in // java.lang.invoke and sun.invoke packages and subpackages). 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. KlassHandle 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; } } Handle mirror = k->java_mirror(); _is_constant = true; switch(type()->basic_type()) { case T_BYTE: _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset)); break; case T_CHAR: _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset)); break; case T_SHORT: _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset)); break; case T_BOOLEAN: _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset)); break; case T_INT: _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset)); break; case T_FLOAT: _constant_value = ciConstant(mirror->float_field(_offset)); break; case T_DOUBLE: _constant_value = ciConstant(mirror->double_field(_offset)); break; case T_LONG: _constant_value = ciConstant(mirror->long_field(_offset)); break; case T_OBJECT: case T_ARRAY: { oop o = mirror->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, 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(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("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 && 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); }