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 #include "ci/ciUtilities.hpp"
  33 
  34 // ciField
  35 //
  36 // This class represents the result of a field lookup in the VM.
  37 // The lookup may not succeed, in which case the information in
  38 // the ciField will be incomplete.
  39 class ciField : public ResourceObj {
  40   CI_PACKAGE_ACCESS
  41   friend class ciEnv;
  42   friend class ciInstanceKlass;
  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   ciMethod*        _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() const { 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() const { return _holder; }
  94 
  95   // Name of this field?
  96   ciSymbol* name() const { return _name; }
  97 
  98   // Signature of this field?
  99   ciSymbol* signature() const { 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() const {
 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() const {
 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 field is not one of the special static/final
 132   //      non-constant fields.  These are java.lang.System.in
 133   //      and java.lang.System.out.  Abomination.
 134   //
 135   // A field is also considered constant if
 136   // - it is marked @Stable and is non-null (or non-zero, if a primitive) or
 137   // - it is trusted or
 138   // - it is the target field of a CallSite object.
 139   //
 140   // See ciField::initialize_from() for more details.
 141   //
 142   // A user should also check the field value (constant_value().is_valid()), since
 143   // constant fields of non-initialized classes don't have values yet.
 144   bool is_constant() const { return _is_constant; }
 145 
 146   // Get the constant value of the static field.
 147   ciConstant constant_value();
 148 
 149   bool is_static_constant() {
 150     return is_static() && is_constant() && constant_value().is_valid();
 151   }
 152 
 153   // Get the constant value of non-static final field in the given
 154   // object.
 155   ciConstant constant_value_of(ciObject* object);
 156 
 157   // Check for link time errors.  Accessing a field from a
 158   // certain method 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(ciMethod* accessing_method,
 166                  Bytecodes::Code bc);
 167 
 168   // Java access flags
 169   bool is_public               () const { return flags().is_public(); }
 170   bool is_private              () const { return flags().is_private(); }
 171   bool is_protected            () const { return flags().is_protected(); }
 172   bool is_static               () const { return flags().is_static(); }
 173   bool is_final                () const { return flags().is_final(); }
 174   bool is_stable               () const { return flags().is_stable(); }
 175   bool is_volatile             () const { return flags().is_volatile(); }
 176   bool is_transient            () const { return flags().is_transient(); }
 177   // The field is modified outside of instance initializer methods
 178   // (or class/initializer methods if the field is static).
 179   bool has_initialized_final_update() const { return flags().has_initialized_final_update(); }
 180 
 181   bool is_call_site_target() {
 182     ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
 183     if (callsite_klass == NULL)
 184       return false;
 185     return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbol::target_name()));
 186   }
 187 
 188   bool is_autobox_cache() {
 189     ciSymbol* klass_name = holder()->name();
 190     return (name() == ciSymbol::cache_field_name() &&
 191             holder()->uses_default_loader() &&
 192             (klass_name == ciSymbol::java_lang_Character_CharacterCache() ||
 193              klass_name == ciSymbol::java_lang_Byte_ByteCache() ||
 194              klass_name == ciSymbol::java_lang_Short_ShortCache() ||
 195              klass_name == ciSymbol::java_lang_Integer_IntegerCache() ||
 196              klass_name == ciSymbol::java_lang_Long_LongCache()));
 197   }
 198 
 199   // Debugging output
 200   void print();
 201   void print_name_on(outputStream* st);
 202 };
 203 
 204 #endif // SHARE_VM_CI_CIFIELD_HPP
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