368 lines
14 KiB
C++
368 lines
14 KiB
C++
/*
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* Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "ci/ciField.hpp"
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#include "ci/ciInstanceKlass.hpp"
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#include "ci/ciUtilities.hpp"
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#include "classfile/systemDictionary.hpp"
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#include "gc_interface/collectedHeap.inline.hpp"
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#include "interpreter/linkResolver.hpp"
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#include "memory/universe.inline.hpp"
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#include "oops/oop.inline.hpp"
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#include "oops/oop.inline2.hpp"
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#include "runtime/fieldDescriptor.hpp"
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// ciField
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//
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// This class represents the result of a field lookup in the VM.
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// The lookup may not succeed, in which case the information in
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// the ciField will be incomplete.
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// The ciObjectFactory cannot create circular data structures in one query.
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// To avoid vicious circularities, we initialize ciField::_type to NULL
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// for reference types and derive it lazily from the ciField::_signature.
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// Primitive types are eagerly initialized, and basic layout queries
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// can succeed without initialization, using only the BasicType of the field.
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// Notes on bootstrapping and shared CI objects: A field is shared if and
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// only if it is (a) non-static and (b) declared by a shared instance klass.
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// This allows non-static field lists to be cached on shared types.
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// Because the _type field is lazily initialized, however, there is a
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// special restriction that a shared field cannot cache an unshared type.
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// This puts a small performance penalty on shared fields with unshared
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// types, such as StackTraceElement[] Throwable.stackTrace.
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// (Throwable is shared because ClassCastException is shared, but
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// StackTraceElement is not presently shared.)
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// It is not a vicious circularity for a ciField to recursively create
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// the ciSymbols necessary to represent its name and signature.
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// Therefore, these items are created eagerly, and the name and signature
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// of a shared field are themselves shared symbols. This somewhat
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// pollutes the set of shared CI objects: It grows from 50 to 93 items,
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// with all of the additional 43 being uninteresting shared ciSymbols.
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// This adds at most one step to the binary search, an amount which
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// decreases for complex compilation tasks.
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// ------------------------------------------------------------------
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// ciField::ciField
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ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with(NULL) {
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ASSERT_IN_VM;
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CompilerThread *thread = CompilerThread::current();
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assert(ciObjectFactory::is_initialized(), "not a shared field");
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assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constan-pool");
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_cp_index = index;
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constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
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// Get the field's name, signature, and type.
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Symbol* name = cpool->name_ref_at(index);
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_name = ciEnv::current(thread)->get_symbol(name);
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int nt_index = cpool->name_and_type_ref_index_at(index);
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int sig_index = cpool->signature_ref_index_at(nt_index);
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Symbol* signature = cpool->symbol_at(sig_index);
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_signature = ciEnv::current(thread)->get_symbol(signature);
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BasicType field_type = FieldType::basic_type(signature);
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// If the field is a pointer type, get the klass of the
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// field.
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if (field_type == T_OBJECT || field_type == T_ARRAY) {
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bool ignore;
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// This is not really a class reference; the index always refers to the
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// field's type signature, as a symbol. Linkage checks do not apply.
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_type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
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} else {
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_type = ciType::make(field_type);
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}
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_name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
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// Get the field's declared holder.
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//
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// Note: we actually create a ciInstanceKlass for this klass,
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// even though we may not need to.
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int holder_index = cpool->klass_ref_index_at(index);
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bool holder_is_accessible;
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ciInstanceKlass* declared_holder =
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ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
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holder_is_accessible,
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klass)->as_instance_klass();
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// The declared holder of this field may not have been loaded.
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// Bail out with partial field information.
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if (!holder_is_accessible) {
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// _cp_index and _type have already been set.
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// The default values for _flags and _constant_value will suffice.
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// We need values for _holder, _offset, and _is_constant,
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_holder = declared_holder;
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_offset = -1;
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_is_constant = false;
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return;
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}
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instanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
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// Perform the field lookup.
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fieldDescriptor field_desc;
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klassOop canonical_holder =
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loaded_decl_holder->find_field(name, signature, &field_desc);
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if (canonical_holder == NULL) {
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// Field lookup failed. Will be detected by will_link.
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_holder = declared_holder;
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_offset = -1;
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_is_constant = false;
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return;
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}
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assert(canonical_holder == field_desc.field_holder(), "just checking");
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initialize_from(&field_desc);
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}
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ciField::ciField(fieldDescriptor *fd): _known_to_link_with(NULL) {
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ASSERT_IN_VM;
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_cp_index = -1;
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// Get the field's name, signature, and type.
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ciEnv* env = CURRENT_ENV;
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_name = env->get_symbol(fd->name());
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_signature = env->get_symbol(fd->signature());
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BasicType field_type = fd->field_type();
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// If the field is a pointer type, get the klass of the
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// field.
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if (field_type == T_OBJECT || field_type == T_ARRAY) {
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_type = NULL; // must call compute_type on first access
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} else {
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_type = ciType::make(field_type);
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}
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initialize_from(fd);
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// Either (a) it is marked shared, or else (b) we are done bootstrapping.
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assert(is_shared() || ciObjectFactory::is_initialized(),
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"bootstrap classes must not create & cache unshared fields");
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}
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static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
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if (holder == NULL)
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return false;
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if (holder->name() == ciSymbol::java_lang_System())
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// Never trust strangely unstable finals: System.out, etc.
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return false;
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// Even if general trusting is disabled, trust system-built closures in these packages.
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if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
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return true;
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return TrustFinalNonStaticFields;
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}
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void ciField::initialize_from(fieldDescriptor* fd) {
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// Get the flags, offset, and canonical holder of the field.
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_flags = ciFlags(fd->access_flags());
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_offset = fd->offset();
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_holder = CURRENT_ENV->get_object(fd->field_holder())->as_instance_klass();
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// Check to see if the field is constant.
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if (_holder->is_initialized() && this->is_final()) {
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if (!this->is_static()) {
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// A field can be constant if it's a final static field or if
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// it's a final non-static field of a trusted class (classes in
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// java.lang.invoke and sun.invoke packages and subpackages).
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if (trust_final_non_static_fields(_holder)) {
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_is_constant = true;
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return;
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}
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_is_constant = false;
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return;
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}
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// This field just may be constant. The only cases where it will
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// not be constant are:
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//
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// 1. The field holds a non-perm-space oop. The field is, strictly
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// speaking, constant but we cannot embed non-perm-space oops into
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// generated code. For the time being we need to consider the
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// field to be not constant.
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// 2. The field is a *special* static&final field whose value
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// may change. The three examples are java.lang.System.in,
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// java.lang.System.out, and java.lang.System.err.
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KlassHandle k = _holder->get_klassOop();
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assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
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if( k() == SystemDictionary::System_klass() ) {
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// Check offsets for case 2: System.in, System.out, or System.err
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if( _offset == java_lang_System::in_offset_in_bytes() ||
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_offset == java_lang_System::out_offset_in_bytes() ||
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_offset == java_lang_System::err_offset_in_bytes() ) {
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_is_constant = false;
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return;
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}
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}
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Handle mirror = k->java_mirror();
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_is_constant = true;
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switch(type()->basic_type()) {
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case T_BYTE:
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_constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
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break;
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case T_CHAR:
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_constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
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break;
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case T_SHORT:
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_constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
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break;
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case T_BOOLEAN:
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_constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
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break;
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case T_INT:
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_constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
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break;
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case T_FLOAT:
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_constant_value = ciConstant(mirror->float_field(_offset));
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break;
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case T_DOUBLE:
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_constant_value = ciConstant(mirror->double_field(_offset));
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break;
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case T_LONG:
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_constant_value = ciConstant(mirror->long_field(_offset));
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break;
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case T_OBJECT:
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case T_ARRAY:
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{
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oop o = mirror->obj_field(_offset);
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// A field will be "constant" if it is known always to be
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// a non-null reference to an instance of a particular class,
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// or to a particular array. This can happen even if the instance
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// or array is not perm. In such a case, an "unloaded" ciArray
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// or ciInstance is created. The compiler may be able to use
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// information about the object's class (which is exact) or length.
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if (o == NULL) {
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_constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
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} else {
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_constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
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assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
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}
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}
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}
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} else {
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_is_constant = false;
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}
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}
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// ------------------------------------------------------------------
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// ciField::compute_type
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//
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// Lazily compute the type, if it is an instance klass.
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ciType* ciField::compute_type() {
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GUARDED_VM_ENTRY(return compute_type_impl();)
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}
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ciType* ciField::compute_type_impl() {
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ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
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if (!type->is_primitive_type() && is_shared()) {
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// We must not cache a pointer to an unshared type, in a shared field.
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bool type_is_also_shared = false;
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if (type->is_type_array_klass()) {
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type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
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} else if (type->is_instance_klass()) {
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type_is_also_shared = type->as_instance_klass()->is_shared();
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} else {
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// Currently there is no 'shared' query for array types.
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type_is_also_shared = !ciObjectFactory::is_initialized();
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}
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if (!type_is_also_shared)
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return type; // Bummer.
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}
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_type = type;
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return type;
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}
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// ------------------------------------------------------------------
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// ciField::will_link
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//
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// Can a specific access to this field be made without causing
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// link errors?
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bool ciField::will_link(ciInstanceKlass* accessing_klass,
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Bytecodes::Code bc) {
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VM_ENTRY_MARK;
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if (_offset == -1) {
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// at creation we couldn't link to our holder so we need to
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// maintain that stance, otherwise there's no safe way to use this
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// ciField.
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return false;
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}
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if (_known_to_link_with == accessing_klass) {
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return true;
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}
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FieldAccessInfo result;
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constantPoolHandle c_pool(THREAD,
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accessing_klass->get_instanceKlass()->constants());
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LinkResolver::resolve_field(result, c_pool, _cp_index,
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Bytecodes::java_code(bc),
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true, false, KILL_COMPILE_ON_FATAL_(false));
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// update the hit-cache, unless there is a problem with memory scoping:
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if (accessing_klass->is_shared() || !is_shared())
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_known_to_link_with = accessing_klass;
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return true;
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}
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// ------------------------------------------------------------------
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// ciField::print
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void ciField::print() {
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tty->print("<ciField ");
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_holder->print_name();
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tty->print(".");
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_name->print_symbol();
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tty->print(" offset=%d type=", _offset);
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if (_type != NULL) _type->print_name();
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else tty->print("(reference)");
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tty->print(" is_constant=%s", bool_to_str(_is_constant));
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if (_is_constant && is_static()) {
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tty->print(" constant_value=");
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_constant_value.print();
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}
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tty->print(">");
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}
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// ------------------------------------------------------------------
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// ciField::print_name_on
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//
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// Print the name of this field
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void ciField::print_name_on(outputStream* st) {
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name()->print_symbol_on(st);
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}
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