1 /*
   2  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_CI_CIFIELD_HPP
  26 #define SHARE_VM_CI_CIFIELD_HPP
  27 
  28 #include "ci/ciClassList.hpp"
  29 #include "ci/ciConstant.hpp"
  30 #include "ci/ciFlags.hpp"
  31 #include "ci/ciInstance.hpp"
  32 
  33 // ciField
  34 //
  35 // This class represents the result of a field lookup in the VM.
  36 // The lookup may not succeed, in which case the information in
  37 // the ciField will be incomplete.
  38 class ciField : public ResourceObj {
  39   CI_PACKAGE_ACCESS
  40   friend class ciEnv;
  41   friend class ciInstanceKlass;
  42   friend class NonStaticFieldFiller;
  43 
  44 private:
  45   ciFlags          _flags;
  46   ciInstanceKlass* _holder;
  47   ciSymbol*        _name;
  48   ciSymbol*        _signature;
  49   ciType*          _type;
  50   int              _offset;
  51   bool             _is_constant;
  52   ciInstanceKlass* _known_to_link_with_put;
  53   ciInstanceKlass* _known_to_link_with_get;
  54   ciConstant       _constant_value;
  55 
  56   ciType* compute_type();
  57   ciType* compute_type_impl();
  58 
  59   ciField(ciInstanceKlass* klass, int index);
  60   ciField(fieldDescriptor* fd);
  61 
  62   // shared constructor code
  63   void initialize_from(fieldDescriptor* fd);
  64 
  65 public:
  66   ciFlags flags() { return _flags; }
  67 
  68   // Of which klass is this field a member?
  69   //
  70   // Usage note: the declared holder of a field is the class
  71   // referenced by name in the bytecodes.  The canonical holder
  72   // is the most general class which holds the field.  This
  73   // method returns the canonical holder.  The declared holder
  74   // can be accessed via a method in ciBytecodeStream.
  75   //
  76   // Ex.
  77   //     class A {
  78   //       public int f = 7;
  79   //     }
  80   //     class B extends A {
  81   //       public void test() {
  82   //         System.out.println(f);
  83   //       }
  84   //     }
  85   //
  86   //   A java compiler is permitted to compile the access to
  87   //   field f as:
  88   //
  89   //     getfield B.f
  90   //
  91   //   In that case the declared holder of f would be B and
  92   //   the canonical holder of f would be A.
  93   ciInstanceKlass* holder() { return _holder; }
  94 
  95   // Name of this field?
  96   ciSymbol* name() { return _name; }
  97 
  98   // Signature of this field?
  99   ciSymbol* signature() { return _signature; }
 100 
 101   // Of what type is this field?
 102   ciType* type() { return (_type == NULL) ? compute_type() : _type; }
 103 
 104   // How is this field actually stored in memory?
 105   BasicType layout_type() { return type2field[(_type == NULL) ? T_OBJECT : _type->basic_type()]; }
 106 
 107   // How big is this field in memory?
 108   int size_in_bytes() { return type2aelembytes(layout_type()); }
 109 
 110   // What is the offset of this field?
 111   int offset() {
 112     assert(_offset >= 1, "illegal call to offset()");
 113     return _offset;
 114   }
 115 
 116   // Same question, explicit units.  (Fields are aligned to the byte level.)
 117   int offset_in_bytes() {
 118     return offset();
 119   }
 120 
 121   // Is this field shared?
 122   bool is_shared() {
 123     // non-static fields of shared holders are cached
 124     return _holder->is_shared() && !is_static();
 125   }
 126 
 127   // Is this field a constant?
 128   //
 129   // Clarification: A field is considered constant if:
 130   //   1. The field is both static and final
 131   //   2. The canonical holder of the field has undergone
 132   //      static initialization.
 133   //   3. The field is not one of the special static/final
 134   //      non-constant fields.  These are java.lang.System.in
 135   //      and java.lang.System.out.  Abomination.
 136   //
 137   // A field is also considered constant if it is marked @Stable
 138   // and is non-null (or non-zero, if a primitive).
 139   // For non-static fields, the null/zero check must be
 140   // arranged by the user, as constant_value().is_null_or_zero().
 141   bool is_constant() { return _is_constant; }
 142 
 143   // Get the constant value of this field.
 144   ciConstant constant_value() {
 145     assert(is_static() && is_constant(), "illegal call to constant_value()");
 146     return _constant_value;
 147   }
 148 
 149   // Get the constant value of non-static final field in the given
 150   // object.
 151   ciConstant constant_value_of(ciObject* object) {
 152     assert(!is_static() && is_constant(), "only if field is non-static constant");
 153     assert(object->is_instance(), "must be instance");
 154     return object->as_instance()->field_value(this);
 155   }
 156 
 157   // Check for link time errors.  Accessing a field from a
 158   // certain class via a certain bytecode may or may not be legal.
 159   // This call checks to see if an exception may be raised by
 160   // an access of this field.
 161   //
 162   // Usage note: if the same field is accessed multiple times
 163   // in the same compilation, will_link will need to be checked
 164   // at each point of access.
 165   bool will_link(ciInstanceKlass* accessing_klass,
 166                  Bytecodes::Code bc);
 167 
 168   // Java access flags
 169   bool is_public      () { return flags().is_public(); }
 170   bool is_private     () { return flags().is_private(); }
 171   bool is_protected   () { return flags().is_protected(); }
 172   bool is_static      () { return flags().is_static(); }
 173   bool is_final       () { return flags().is_final(); }
 174   bool is_stable      () { return flags().is_stable(); }
 175   bool is_volatile    () { return flags().is_volatile(); }
 176   bool is_transient   () { return flags().is_transient(); }
 177 
 178   bool is_call_site_target() {
 179     ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
 180     if (callsite_klass == NULL)
 181       return false;
 182     return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbol::target_name()));
 183   }
 184 
 185   // Debugging output
 186   void print();
 187   void print_name_on(outputStream* st);
 188 };
 189 
 190 #endif // SHARE_VM_CI_CIFIELD_HPP