1 /*
   2  * Copyright 1999-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 // ciObject
  26 //
  27 // This class represents an oop in the HotSpot virtual machine.
  28 // Its subclasses are structured in a hierarchy which mirrors
  29 // an aggregate of the VM's oop and klass hierarchies (see
  30 // oopHierarchy.hpp).  Each instance of ciObject holds a handle
  31 // to a corresponding oop on the VM side and provides routines
  32 // for accessing the information in its oop.  By using the ciObject
  33 // hierarchy for accessing oops in the VM, the compiler ensures
  34 // that it is safe with respect to garbage collection; that is,
  35 // GC and compilation can proceed independently without
  36 // interference.
  37 //
  38 // Within the VM, the oop and klass hierarchies are separate.
  39 // The compiler interface does not preserve this separation --
  40 // the distinction between `klassOop' and `Klass' are not
  41 // reflected in the interface and instead the Klass hierarchy
  42 // is directly modeled as the subclasses of ciKlass.
  43 class ciObject : public ResourceObj {
  44   CI_PACKAGE_ACCESS
  45   friend class ciEnv;
  46 
  47 private:
  48   // A JNI handle referring to an oop in the VM.  This
  49   // handle may, in a small set of cases, correctly be NULL.
  50   jobject  _handle;
  51   ciKlass* _klass;
  52   uint     _ident;
  53 
  54   enum { FLAG_BITS   = 2 };
  55   enum {
  56          PERM_FLAG        = 1,
  57          SCAVENGABLE_FLAG = 2
  58        };
  59 protected:
  60   ciObject();
  61   ciObject(oop o);
  62   ciObject(Handle h);
  63   ciObject(ciKlass* klass);
  64 
  65   jobject      handle()  const { return _handle; }
  66   // Get the VM oop that this object holds.
  67   oop get_oop() const {
  68     assert(_handle != NULL, "null oop");
  69     return JNIHandles::resolve_non_null(_handle);
  70   }
  71 
  72   void init_flags_from(oop x) {
  73     int flags = 0;
  74     if (x != NULL) {
  75       if (x->is_perm())
  76         flags |= PERM_FLAG;
  77       if (x->is_scavengable())
  78         flags |= SCAVENGABLE_FLAG;
  79     }
  80     _ident |= flags;
  81   }
  82 
  83   // Virtual behavior of the print() method.
  84   virtual void print_impl(outputStream* st) {}
  85 
  86   virtual const char* type_string() { return "ciObject"; }
  87 
  88   void set_ident(uint id);
  89 public:
  90   // The klass of this ciObject.
  91   ciKlass* klass();
  92 
  93   // A number unique to this object.
  94   uint ident();
  95 
  96   // Are two ciObjects equal?
  97   bool equals(ciObject* obj);
  98 
  99   // A hash value for the convenience of compilers.
 100   int hash();
 101 
 102   // Tells if this oop has an encoding as a constant.
 103   // True if is_scavengable is false.
 104   // Also true if ScavengeRootsInCode is non-zero.
 105   // If it does not have an encoding, the compiler is responsible for
 106   // making other arrangements for dealing with the oop.
 107   // See ciEnv::make_array
 108   bool can_be_constant();
 109 
 110   // Tells if this oop should be made a constant.
 111   // True if is_scavengable is false or ScavengeRootsInCode > 1.
 112   bool should_be_constant();
 113 
 114   // Is this object guaranteed to be in the permanent part of the heap?
 115   // If so, CollectedHeap::can_elide_permanent_oop_store_barriers is relevant.
 116   // If the answer is false, no guarantees are made.
 117   bool is_perm() { return (_ident & PERM_FLAG) != 0; }
 118 
 119   // Might this object possibly move during a scavenge operation?
 120   // If the answer is true and ScavengeRootsInCode==0, the oop cannot be embedded in code.
 121   bool is_scavengable() { return (_ident & SCAVENGABLE_FLAG) != 0; }
 122 
 123   // The address which the compiler should embed into the
 124   // generated code to represent this oop.  This address
 125   // is not the true address of the oop -- it will get patched
 126   // during nmethod creation.
 127   //
 128   // Usage note: no address arithmetic allowed.  Oop must
 129   // be registered with the oopRecorder.
 130   jobject constant_encoding();
 131 
 132   // What kind of ciObject is this?
 133   virtual bool is_null_object() const       { return false; }
 134   virtual bool is_call_site() const         { return false; }
 135   virtual bool is_cpcache() const           { return false; }
 136   virtual bool is_instance()                { return false; }
 137   virtual bool is_method()                  { return false; }
 138   virtual bool is_method_data()             { return false; }
 139   virtual bool is_method_handle() const     { return false; }
 140   virtual bool is_array()                   { return false; }
 141   virtual bool is_obj_array()               { return false; }
 142   virtual bool is_type_array()              { return false; }
 143   virtual bool is_symbol()                  { return false; }
 144   virtual bool is_type()                    { return false; }
 145   virtual bool is_return_address()          { return false; }
 146   virtual bool is_klass()                   { return false; }
 147   virtual bool is_instance_klass()          { return false; }
 148   virtual bool is_method_klass()            { return false; }
 149   virtual bool is_array_klass()             { return false; }
 150   virtual bool is_obj_array_klass()         { return false; }
 151   virtual bool is_type_array_klass()        { return false; }
 152   virtual bool is_symbol_klass()            { return false; }
 153   virtual bool is_klass_klass()             { return false; }
 154   virtual bool is_instance_klass_klass()    { return false; }
 155   virtual bool is_array_klass_klass()       { return false; }
 156   virtual bool is_obj_array_klass_klass()   { return false; }
 157   virtual bool is_type_array_klass_klass()  { return false; }
 158 
 159   // Is this a type or value which has no associated class?
 160   // It is true of primitive types and null objects.
 161   virtual bool is_classless() const         { return false; }
 162 
 163   // Is this ciObject a Java Language Object?  That is,
 164   // is the ciObject an instance or an array
 165   virtual bool is_java_object()             { return false; }
 166 
 167   // Does this ciObject represent a Java Language class?
 168   // That is, is the ciObject an instanceKlass or arrayKlass?
 169   virtual bool is_java_klass()              { return false; }
 170 
 171   // Is this ciObject the ciInstanceKlass representing
 172   // java.lang.Object()?
 173   virtual bool is_java_lang_Object()        { return false; }
 174 
 175   // Does this ciObject refer to a real oop in the VM?
 176   //
 177   // Note: some ciObjects refer to oops which have yet to be
 178   // created.  We refer to these as "unloaded".  Specifically,
 179   // there are unloaded ciMethods, ciObjArrayKlasses, and
 180   // ciInstanceKlasses.  By convention the ciNullObject is
 181   // considered loaded, and primitive types are considered loaded.
 182   bool is_loaded() const {
 183     return handle() != NULL || is_classless();
 184   }
 185 
 186   // Subclass casting with assertions.
 187   ciNullObject*            as_null_object() {
 188     assert(is_null_object(), "bad cast");
 189     return (ciNullObject*)this;
 190   }
 191   ciCallSite*              as_call_site() {
 192     assert(is_call_site(), "bad cast");
 193     return (ciCallSite*) this;
 194   }
 195   ciCPCache*               as_cpcache() {
 196     assert(is_cpcache(), "bad cast");
 197     return (ciCPCache*) this;
 198   }
 199   ciInstance*              as_instance() {
 200     assert(is_instance(), "bad cast");
 201     return (ciInstance*)this;
 202   }
 203   ciMethod*                as_method() {
 204     assert(is_method(), "bad cast");
 205     return (ciMethod*)this;
 206   }
 207   ciMethodData*            as_method_data() {
 208     assert(is_method_data(), "bad cast");
 209     return (ciMethodData*)this;
 210   }
 211   ciMethodHandle*          as_method_handle() {
 212     assert(is_method_handle(), "bad cast");
 213     return (ciMethodHandle*) this;
 214   }
 215   ciArray*                 as_array() {
 216     assert(is_array(), "bad cast");
 217     return (ciArray*)this;
 218   }
 219   ciObjArray*              as_obj_array() {
 220     assert(is_obj_array(), "bad cast");
 221     return (ciObjArray*)this;
 222   }
 223   ciTypeArray*             as_type_array() {
 224     assert(is_type_array(), "bad cast");
 225     return (ciTypeArray*)this;
 226   }
 227   ciSymbol*                as_symbol() {
 228     assert(is_symbol(), "bad cast");
 229     return (ciSymbol*)this;
 230   }
 231   ciType*                  as_type() {
 232     assert(is_type(), "bad cast");
 233     return (ciType*)this;
 234   }
 235   ciReturnAddress*         as_return_address() {
 236     assert(is_return_address(), "bad cast");
 237     return (ciReturnAddress*)this;
 238   }
 239   ciKlass*                 as_klass() {
 240     assert(is_klass(), "bad cast");
 241     return (ciKlass*)this;
 242   }
 243   ciInstanceKlass*         as_instance_klass() {
 244     assert(is_instance_klass(), "bad cast");
 245     return (ciInstanceKlass*)this;
 246   }
 247   ciMethodKlass*           as_method_klass() {
 248     assert(is_method_klass(), "bad cast");
 249     return (ciMethodKlass*)this;
 250   }
 251   ciArrayKlass*            as_array_klass() {
 252     assert(is_array_klass(), "bad cast");
 253     return (ciArrayKlass*)this;
 254   }
 255   ciObjArrayKlass*         as_obj_array_klass() {
 256     assert(is_obj_array_klass(), "bad cast");
 257     return (ciObjArrayKlass*)this;
 258   }
 259   ciTypeArrayKlass*        as_type_array_klass() {
 260     assert(is_type_array_klass(), "bad cast");
 261     return (ciTypeArrayKlass*)this;
 262   }
 263   ciSymbolKlass*           as_symbol_klass() {
 264     assert(is_symbol_klass(), "bad cast");
 265     return (ciSymbolKlass*)this;
 266   }
 267   ciKlassKlass*            as_klass_klass() {
 268     assert(is_klass_klass(), "bad cast");
 269     return (ciKlassKlass*)this;
 270   }
 271   ciInstanceKlassKlass*    as_instance_klass_klass() {
 272     assert(is_instance_klass_klass(), "bad cast");
 273     return (ciInstanceKlassKlass*)this;
 274   }
 275   ciArrayKlassKlass*       as_array_klass_klass() {
 276     assert(is_array_klass_klass(), "bad cast");
 277     return (ciArrayKlassKlass*)this;
 278   }
 279   ciObjArrayKlassKlass*    as_obj_array_klass_klass() {
 280     assert(is_obj_array_klass_klass(), "bad cast");
 281     return (ciObjArrayKlassKlass*)this;
 282   }
 283   ciTypeArrayKlassKlass*   as_type_array_klass_klass() {
 284     assert(is_type_array_klass_klass(), "bad cast");
 285     return (ciTypeArrayKlassKlass*)this;
 286   }
 287 
 288   // Print debugging output about this ciObject.
 289   void print(outputStream* st = tty);
 290 
 291   // Print debugging output about the oop this ciObject represents.
 292   void print_oop(outputStream* st = tty);
 293 };