--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/ci/ciField.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,333 @@
+/*
+ * Copyright 1999-2007 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(klass, sig_index, ignore);
+  } 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(klass, holder_index,
+                                               holder_is_accessible)
+      ->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");
+}
+
+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() && this->is_static()) {
+    // 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);
+}