1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   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).
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_CODE_RELOCINFO_HPP
  26 #define SHARE_VM_CODE_RELOCINFO_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/os.hpp"
  30 #include "utilities/macros.hpp"
  31 
  32 class nmethod;
  33 class CompiledMethod;
  34 class Metadata;
  35 class NativeMovConstReg;
  36 
  37 // Types in this file:
  38 //    relocInfo
  39 //      One element of an array of halfwords encoding compressed relocations.
  40 //      Also, the source of relocation types (relocInfo::oop_type, ...).
  41 //    Relocation
  42 //      A flyweight object representing a single relocation.
  43 //      It is fully unpacked from the compressed relocation array.
  44 //    metadata_Relocation, ... (subclasses of Relocation)
  45 //      The location of some type-specific operations (metadata_addr, ...).
  46 //      Also, the source of relocation specs (metadata_Relocation::spec, ...).
  47 //    oop_Relocation, ... (subclasses of Relocation)
  48 //      oops in the code stream (strings, class loaders)
  49 //      Also, the source of relocation specs (oop_Relocation::spec, ...).
  50 //    RelocationHolder
  51 //      A ValueObj type which acts as a union holding a Relocation object.
  52 //      Represents a relocation spec passed into a CodeBuffer during assembly.
  53 //    RelocIterator
  54 //      A StackObj which iterates over the relocations associated with
  55 //      a range of code addresses.  Can be used to operate a copy of code.
  56 //    BoundRelocation
  57 //      An _internal_ type shared by packers and unpackers of relocations.
  58 //      It pastes together a RelocationHolder with some pointers into
  59 //      code and relocInfo streams.
  60 
  61 
  62 // Notes on relocType:
  63 //
  64 // These hold enough information to read or write a value embedded in
  65 // the instructions of an CodeBlob.  They're used to update:
  66 //
  67 //   1) embedded oops     (isOop()          == true)
  68 //   2) inline caches     (isIC()           == true)
  69 //   3) runtime calls     (isRuntimeCall()  == true)
  70 //   4) internal word ref (isInternalWord() == true)
  71 //   5) external word ref (isExternalWord() == true)
  72 //
  73 // when objects move (GC) or if code moves (compacting the code heap).
  74 // They are also used to patch the code (if a call site must change)
  75 //
  76 // A relocInfo is represented in 16 bits:
  77 //   4 bits indicating the relocation type
  78 //  12 bits indicating the offset from the previous relocInfo address
  79 //
  80 // The offsets accumulate along the relocInfo stream to encode the
  81 // address within the CodeBlob, which is named RelocIterator::addr().
  82 // The address of a particular relocInfo always points to the first
  83 // byte of the relevant instruction (and not to any of its subfields
  84 // or embedded immediate constants).
  85 //
  86 // The offset value is scaled appropriately for the target machine.
  87 // (See relocInfo_<arch>.hpp for the offset scaling.)
  88 //
  89 // On some machines, there may also be a "format" field which may provide
  90 // additional information about the format of the instruction stream
  91 // at the corresponding code address.  The format value is usually zero.
  92 // Any machine (such as Intel) whose instructions can sometimes contain
  93 // more than one relocatable constant needs format codes to distinguish
  94 // which operand goes with a given relocation.
  95 //
  96 // If the target machine needs N format bits, the offset has 12-N bits,
  97 // the format is encoded between the offset and the type, and the
  98 // relocInfo_<arch>.hpp file has manifest constants for the format codes.
  99 //
 100 // If the type is "data_prefix_tag" then the offset bits are further encoded,
 101 // and in fact represent not a code-stream offset but some inline data.
 102 // The data takes the form of a counted sequence of halfwords, which
 103 // precedes the actual relocation record.  (Clients never see it directly.)
 104 // The interpetation of this extra data depends on the relocation type.
 105 //
 106 // On machines that have 32-bit immediate fields, there is usually
 107 // little need for relocation "prefix" data, because the instruction stream
 108 // is a perfectly reasonable place to store the value.  On machines in
 109 // which 32-bit values must be "split" across instructions, the relocation
 110 // data is the "true" specification of the value, which is then applied
 111 // to some field of the instruction (22 or 13 bits, on SPARC).
 112 //
 113 // Whenever the location of the CodeBlob changes, any PC-relative
 114 // relocations, and any internal_word_type relocations, must be reapplied.
 115 // After the GC runs, oop_type relocations must be reapplied.
 116 //
 117 //
 118 // Here are meanings of the types:
 119 //
 120 // relocInfo::none -- a filler record
 121 //   Value:  none
 122 //   Instruction: The corresponding code address is ignored
 123 //   Data:  Any data prefix and format code are ignored
 124 //   (This means that any relocInfo can be disabled by setting
 125 //   its type to none.  See relocInfo::remove.)
 126 //
 127 // relocInfo::oop_type, relocInfo::metadata_type -- a reference to an oop or meta data
 128 //   Value:  an oop, or else the address (handle) of an oop
 129 //   Instruction types: memory (load), set (load address)
 130 //   Data:  []       an oop stored in 4 bytes of instruction
 131 //          [n]      n is the index of an oop in the CodeBlob's oop pool
 132 //          [[N]n l] and l is a byte offset to be applied to the oop
 133 //          [Nn Ll]  both index and offset may be 32 bits if necessary
 134 //   Here is a special hack, used only by the old compiler:
 135 //          [[N]n 00] the value is the __address__ of the nth oop in the pool
 136 //   (Note that the offset allows optimal references to class variables.)
 137 //
 138 // relocInfo::internal_word_type -- an address within the same CodeBlob
 139 // relocInfo::section_word_type -- same, but can refer to another section
 140 //   Value:  an address in the CodeBlob's code or constants section
 141 //   Instruction types: memory (load), set (load address)
 142 //   Data:  []     stored in 4 bytes of instruction
 143 //          [[L]l] a relative offset (see [About Offsets] below)
 144 //   In the case of section_word_type, the offset is relative to a section
 145 //   base address, and the section number (e.g., SECT_INSTS) is encoded
 146 //   into the low two bits of the offset L.
 147 //
 148 // relocInfo::external_word_type -- a fixed address in the runtime system
 149 //   Value:  an address
 150 //   Instruction types: memory (load), set (load address)
 151 //   Data:  []   stored in 4 bytes of instruction
 152 //          [n]  the index of a "well-known" stub (usual case on RISC)
 153 //          [Ll] a 32-bit address
 154 //
 155 // relocInfo::runtime_call_type -- a fixed subroutine in the runtime system
 156 //   Value:  an address
 157 //   Instruction types: PC-relative call (or a PC-relative branch)
 158 //   Data:  []   stored in 4 bytes of instruction
 159 //
 160 // relocInfo::static_call_type -- a static call
 161 //   Value:  an CodeBlob, a stub, or a fixup routine
 162 //   Instruction types: a call
 163 //   Data:  []
 164 //   The identity of the callee is extracted from debugging information.
 165 //   //%note reloc_3
 166 //
 167 // relocInfo::virtual_call_type -- a virtual call site (which includes an inline
 168 //                                 cache)
 169 //   Value:  an CodeBlob, a stub, the interpreter, or a fixup routine
 170 //   Instruction types: a call, plus some associated set-oop instructions
 171 //   Data:  []       the associated set-oops are adjacent to the call
 172 //          [n]      n is a relative offset to the first set-oop
 173 //          [[N]n l] and l is a limit within which the set-oops occur
 174 //          [Nn Ll]  both n and l may be 32 bits if necessary
 175 //   The identity of the callee is extracted from debugging information.
 176 //
 177 // relocInfo::opt_virtual_call_type -- a virtual call site that is statically bound
 178 //
 179 //    Same info as a static_call_type. We use a special type, so the handling of
 180 //    virtuals and statics are separated.
 181 //
 182 //
 183 //   The offset n points to the first set-oop.  (See [About Offsets] below.)
 184 //   In turn, the set-oop instruction specifies or contains an oop cell devoted
 185 //   exclusively to the IC call, which can be patched along with the call.
 186 //
 187 //   The locations of any other set-oops are found by searching the relocation
 188 //   information starting at the first set-oop, and continuing until all
 189 //   relocations up through l have been inspected.  The value l is another
 190 //   relative offset.  (Both n and l are relative to the call's first byte.)
 191 //
 192 //   The limit l of the search is exclusive.  However, if it points within
 193 //   the call (e.g., offset zero), it is adjusted to point after the call and
 194 //   any associated machine-specific delay slot.
 195 //
 196 //   Since the offsets could be as wide as 32-bits, these conventions
 197 //   put no restrictions whatever upon code reorganization.
 198 //
 199 //   The compiler is responsible for ensuring that transition from a clean
 200 //   state to a monomorphic compiled state is MP-safe.  This implies that
 201 //   the system must respond well to intermediate states where a random
 202 //   subset of the set-oops has been correctly from the clean state
 203 //   upon entry to the VEP of the compiled method.  In the case of a
 204 //   machine (Intel) with a single set-oop instruction, the 32-bit
 205 //   immediate field must not straddle a unit of memory coherence.
 206 //   //%note reloc_3
 207 //
 208 // relocInfo::static_stub_type -- an extra stub for each static_call_type
 209 //   Value:  none
 210 //   Instruction types: a virtual call:  { set_oop; jump; }
 211 //   Data:  [[N]n]  the offset of the associated static_call reloc
 212 //   This stub becomes the target of a static call which must be upgraded
 213 //   to a virtual call (because the callee is interpreted).
 214 //   See [About Offsets] below.
 215 //   //%note reloc_2
 216 //
 217 // relocInfo::poll_[return_]type -- a safepoint poll
 218 //   Value:  none
 219 //   Instruction types: memory load or test
 220 //   Data:  none
 221 //
 222 // For example:
 223 //
 224 //   INSTRUCTIONS                        RELOC: TYPE    PREFIX DATA
 225 //   ------------                               ----    -----------
 226 // sethi      %hi(myObject),  R               oop_type [n(myObject)]
 227 // ld      [R+%lo(myObject)+fldOffset], R2    oop_type [n(myObject) fldOffset]
 228 // add R2, 1, R2
 229 // st  R2, [R+%lo(myObject)+fldOffset]        oop_type [n(myObject) fldOffset]
 230 //%note reloc_1
 231 //
 232 // This uses 4 instruction words, 8 relocation halfwords,
 233 // and an entry (which is sharable) in the CodeBlob's oop pool,
 234 // for a total of 36 bytes.
 235 //
 236 // Note that the compiler is responsible for ensuring the "fldOffset" when
 237 // added to "%lo(myObject)" does not overflow the immediate fields of the
 238 // memory instructions.
 239 //
 240 //
 241 // [About Offsets] Relative offsets are supplied to this module as
 242 // positive byte offsets, but they may be internally stored scaled
 243 // and/or negated, depending on what is most compact for the target
 244 // system.  Since the object pointed to by the offset typically
 245 // precedes the relocation address, it is profitable to store
 246 // these negative offsets as positive numbers, but this decision
 247 // is internal to the relocation information abstractions.
 248 //
 249 
 250 class Relocation;
 251 class CodeBuffer;
 252 class CodeSection;
 253 class RelocIterator;
 254 
 255 class relocInfo VALUE_OBJ_CLASS_SPEC {
 256   friend class RelocIterator;
 257  public:
 258   enum relocType {
 259     none                    =  0, // Used when no relocation should be generated
 260     oop_type                =  1, // embedded oop
 261     virtual_call_type       =  2, // a standard inline cache call for a virtual send
 262     opt_virtual_call_type   =  3, // a virtual call that has been statically bound (i.e., no IC cache)
 263     static_call_type        =  4, // a static send
 264     static_stub_type        =  5, // stub-entry for static send  (takes care of interpreter case)
 265     runtime_call_type       =  6, // call to fixed external routine
 266     external_word_type      =  7, // reference to fixed external address
 267     internal_word_type      =  8, // reference within the current code blob
 268     section_word_type       =  9, // internal, but a cross-section reference
 269     poll_type               = 10, // polling instruction for safepoints
 270     poll_return_type        = 11, // polling instruction for safepoints at return
 271     metadata_type           = 12, // metadata that used to be oops
 272     trampoline_stub_type    = 13, // stub-entry for trampoline
 273     yet_unused_type_1       = 14, // Still unused
 274     data_prefix_tag         = 15, // tag for a prefix (carries data arguments)
 275     type_mask               = 15  // A mask which selects only the above values
 276   };
 277 
 278  protected:
 279   unsigned short _value;
 280 
 281   enum RawBitsToken { RAW_BITS };
 282   relocInfo(relocType type, RawBitsToken ignore, int bits)
 283     : _value((type << nontype_width) + bits) { }
 284 
 285   relocInfo(relocType type, RawBitsToken ignore, int off, int f)
 286     : _value((type << nontype_width) + (off / (unsigned)offset_unit) + (f << offset_width)) { }
 287 
 288  public:
 289   // constructor
 290   relocInfo(relocType type, int offset, int format = 0)
 291 #ifndef ASSERT
 292   {
 293     (*this) = relocInfo(type, RAW_BITS, offset, format);
 294   }
 295 #else
 296   // Put a bunch of assertions out-of-line.
 297   ;
 298 #endif
 299 
 300   #define APPLY_TO_RELOCATIONS(visitor) \
 301     visitor(oop) \
 302     visitor(metadata) \
 303     visitor(virtual_call) \
 304     visitor(opt_virtual_call) \
 305     visitor(static_call) \
 306     visitor(static_stub) \
 307     visitor(runtime_call) \
 308     visitor(external_word) \
 309     visitor(internal_word) \
 310     visitor(poll) \
 311     visitor(poll_return) \
 312     visitor(section_word) \
 313     visitor(trampoline_stub) \
 314 
 315 
 316  public:
 317   enum {
 318     value_width             = sizeof(unsigned short) * BitsPerByte,
 319     type_width              = 4,   // == log2(type_mask+1)
 320     nontype_width           = value_width - type_width,
 321     datalen_width           = nontype_width-1,
 322     datalen_tag             = 1 << datalen_width,  // or-ed into _value
 323     datalen_limit           = 1 << datalen_width,
 324     datalen_mask            = (1 << datalen_width)-1
 325   };
 326 
 327   // accessors
 328  public:
 329   relocType  type()       const { return (relocType)((unsigned)_value >> nontype_width); }
 330   int  format()           const { return format_mask==0? 0: format_mask &
 331                                          ((unsigned)_value >> offset_width); }
 332   int  addr_offset()      const { assert(!is_prefix(), "must have offset");
 333                                   return (_value & offset_mask)*offset_unit; }
 334 
 335  protected:
 336   const short* data()     const { assert(is_datalen(), "must have data");
 337                                   return (const short*)(this + 1); }
 338   int          datalen()  const { assert(is_datalen(), "must have data");
 339                                   return (_value & datalen_mask); }
 340   int         immediate() const { assert(is_immediate(), "must have immed");
 341                                   return (_value & datalen_mask); }
 342  public:
 343   static int addr_unit()        { return offset_unit; }
 344   static int offset_limit()     { return (1 << offset_width) * offset_unit; }
 345 
 346   void set_type(relocType type);
 347   void set_format(int format);
 348 
 349   void remove() { set_type(none); }
 350 
 351  protected:
 352   bool is_none()                const { return type() == none; }
 353   bool is_prefix()              const { return type() == data_prefix_tag; }
 354   bool is_datalen()             const { assert(is_prefix(), "must be prefix");
 355                                         return (_value & datalen_tag) != 0; }
 356   bool is_immediate()           const { assert(is_prefix(), "must be prefix");
 357                                         return (_value & datalen_tag) == 0; }
 358 
 359  public:
 360   // Occasionally records of type relocInfo::none will appear in the stream.
 361   // We do not bother to filter these out, but clients should ignore them.
 362   // These records serve as "filler" in three ways:
 363   //  - to skip large spans of unrelocated code (this is rare)
 364   //  - to pad out the relocInfo array to the required oop alignment
 365   //  - to disable old relocation information which is no longer applicable
 366 
 367   inline friend relocInfo filler_relocInfo();
 368 
 369   // Every non-prefix relocation may be preceded by at most one prefix,
 370   // which supplies 1 or more halfwords of associated data.  Conventionally,
 371   // an int is represented by 0, 1, or 2 halfwords, depending on how
 372   // many bits are required to represent the value.  (In addition,
 373   // if the sole halfword is a 10-bit unsigned number, it is made
 374   // "immediate" in the prefix header word itself.  This optimization
 375   // is invisible outside this module.)
 376 
 377   inline friend relocInfo prefix_relocInfo(int datalen);
 378 
 379  protected:
 380   // an immediate relocInfo optimizes a prefix with one 10-bit unsigned value
 381   static relocInfo immediate_relocInfo(int data0) {
 382     assert(fits_into_immediate(data0), "data0 in limits");
 383     return relocInfo(relocInfo::data_prefix_tag, RAW_BITS, data0);
 384   }
 385   static bool fits_into_immediate(int data0) {
 386     return (data0 >= 0 && data0 < datalen_limit);
 387   }
 388 
 389  public:
 390   // Support routines for compilers.
 391 
 392   // This routine takes an infant relocInfo (unprefixed) and
 393   // edits in its prefix, if any.  It also updates dest.locs_end.
 394   void initialize(CodeSection* dest, Relocation* reloc);
 395 
 396   // This routine updates a prefix and returns the limit pointer.
 397   // It tries to compress the prefix from 32 to 16 bits, and if
 398   // successful returns a reduced "prefix_limit" pointer.
 399   relocInfo* finish_prefix(short* prefix_limit);
 400 
 401   // bit-packers for the data array:
 402 
 403   // As it happens, the bytes within the shorts are ordered natively,
 404   // but the shorts within the word are ordered big-endian.
 405   // This is an arbitrary choice, made this way mainly to ease debugging.
 406   static int data0_from_int(jint x)         { return x >> value_width; }
 407   static int data1_from_int(jint x)         { return (short)x; }
 408   static jint jint_from_data(short* data) {
 409     return (data[0] << value_width) + (unsigned short)data[1];
 410   }
 411 
 412   static jint short_data_at(int n, short* data, int datalen) {
 413     return datalen > n ? data[n] : 0;
 414   }
 415 
 416   static jint jint_data_at(int n, short* data, int datalen) {
 417     return datalen > n+1 ? jint_from_data(&data[n]) : short_data_at(n, data, datalen);
 418   }
 419 
 420   // Update methods for relocation information
 421   // (since code is dynamically patched, we also need to dynamically update the relocation info)
 422   // Both methods takes old_type, so it is able to performe sanity checks on the information removed.
 423   static void change_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type, relocType new_type);
 424   static void remove_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type);
 425 
 426   // Machine dependent stuff
 427 #include CPU_HEADER(relocInfo)
 428 
 429  protected:
 430   // Derived constant, based on format_width which is PD:
 431   enum {
 432     offset_width       = nontype_width - format_width,
 433     offset_mask        = (1<<offset_width) - 1,
 434     format_mask        = (1<<format_width) - 1
 435   };
 436  public:
 437   enum {
 438 #ifdef _LP64
 439     // for use in format
 440     // format_width must be at least 1 on _LP64
 441     narrow_oop_in_const = 1,
 442 #endif
 443     // Conservatively large estimate of maximum length (in shorts)
 444     // of any relocation record.
 445     // Extended format is length prefix, data words, and tag/offset suffix.
 446     length_limit       = 1 + 1 + (3*BytesPerWord/BytesPerShort) + 1,
 447     have_format        = format_width > 0
 448   };
 449 };
 450 
 451 #define FORWARD_DECLARE_EACH_CLASS(name)              \
 452 class name##_Relocation;
 453 APPLY_TO_RELOCATIONS(FORWARD_DECLARE_EACH_CLASS)
 454 #undef FORWARD_DECLARE_EACH_CLASS
 455 
 456 
 457 
 458 inline relocInfo filler_relocInfo() {
 459   return relocInfo(relocInfo::none, relocInfo::offset_limit() - relocInfo::offset_unit);
 460 }
 461 
 462 inline relocInfo prefix_relocInfo(int datalen = 0) {
 463   assert(relocInfo::fits_into_immediate(datalen), "datalen in limits");
 464   return relocInfo(relocInfo::data_prefix_tag, relocInfo::RAW_BITS, relocInfo::datalen_tag | datalen);
 465 }
 466 
 467 
 468 // Holder for flyweight relocation objects.
 469 // Although the flyweight subclasses are of varying sizes,
 470 // the holder is "one size fits all".
 471 class RelocationHolder VALUE_OBJ_CLASS_SPEC {
 472   friend class Relocation;
 473   friend class CodeSection;
 474 
 475  private:
 476   // this preallocated memory must accommodate all subclasses of Relocation
 477   // (this number is assertion-checked in Relocation::operator new)
 478   enum { _relocbuf_size = 5 };
 479   void* _relocbuf[ _relocbuf_size ];
 480 
 481  public:
 482   Relocation* reloc() const { return (Relocation*) &_relocbuf[0]; }
 483   inline relocInfo::relocType type() const;
 484 
 485   // Add a constant offset to a relocation.  Helper for class Address.
 486   RelocationHolder plus(int offset) const;
 487 
 488   inline RelocationHolder();                // initializes type to none
 489 
 490   inline RelocationHolder(Relocation* r);   // make a copy
 491 
 492   static const RelocationHolder none;
 493 };
 494 
 495 // A RelocIterator iterates through the relocation information of a CodeBlob.
 496 // It is a variable BoundRelocation which is able to take on successive
 497 // values as it is advanced through a code stream.
 498 // Usage:
 499 //   RelocIterator iter(nm);
 500 //   while (iter.next()) {
 501 //     iter.reloc()->some_operation();
 502 //   }
 503 // or:
 504 //   RelocIterator iter(nm);
 505 //   while (iter.next()) {
 506 //     switch (iter.type()) {
 507 //      case relocInfo::oop_type          :
 508 //      case relocInfo::ic_type           :
 509 //      case relocInfo::prim_type         :
 510 //      case relocInfo::uncommon_type     :
 511 //      case relocInfo::runtime_call_type :
 512 //      case relocInfo::internal_word_type:
 513 //      case relocInfo::external_word_type:
 514 //      ...
 515 //     }
 516 //   }
 517 
 518 class RelocIterator : public StackObj {
 519   enum { SECT_LIMIT = 3 };  // must be equal to CodeBuffer::SECT_LIMIT, checked in ctor
 520   friend class Relocation;
 521   friend class relocInfo;       // for change_reloc_info_for_address only
 522   typedef relocInfo::relocType relocType;
 523 
 524  private:
 525   address         _limit;   // stop producing relocations after this _addr
 526   relocInfo*      _current; // the current relocation information
 527   relocInfo*      _end;     // end marker; we're done iterating when _current == _end
 528   CompiledMethod* _code;    // compiled method containing _addr
 529   address         _addr;    // instruction to which the relocation applies
 530   short           _databuf; // spare buffer for compressed data
 531   short*          _data;    // pointer to the relocation's data
 532   short           _datalen; // number of halfwords in _data
 533   char            _format;  // position within the instruction
 534 
 535   // Base addresses needed to compute targets of section_word_type relocs.
 536   address _section_start[SECT_LIMIT];
 537   address _section_end  [SECT_LIMIT];
 538 
 539   void set_has_current(bool b) {
 540     _datalen = !b ? -1 : 0;
 541     debug_only(_data = NULL);
 542   }
 543   void set_current(relocInfo& ri) {
 544     _current = &ri;
 545     set_has_current(true);
 546   }
 547 
 548   RelocationHolder _rh; // where the current relocation is allocated
 549 
 550   relocInfo* current() const { assert(has_current(), "must have current");
 551                                return _current; }
 552 
 553   void set_limits(address begin, address limit);
 554 
 555   void advance_over_prefix();    // helper method
 556 
 557   void initialize_misc();
 558 
 559   void initialize(CompiledMethod* nm, address begin, address limit);
 560 
 561   RelocIterator() { initialize_misc(); }
 562 
 563  public:
 564   // constructor
 565   RelocIterator(CompiledMethod* nm, address begin = NULL, address limit = NULL);
 566   RelocIterator(CodeSection* cb, address begin = NULL, address limit = NULL);
 567 
 568   // get next reloc info, return !eos
 569   bool next() {
 570     _current++;
 571     assert(_current <= _end, "must not overrun relocInfo");
 572     if (_current == _end) {
 573       set_has_current(false);
 574       return false;
 575     }
 576     set_has_current(true);
 577 
 578     if (_current->is_prefix()) {
 579       advance_over_prefix();
 580       assert(!current()->is_prefix(), "only one prefix at a time");
 581     }
 582 
 583     _addr += _current->addr_offset();
 584 
 585     if (_limit != NULL && _addr >= _limit) {
 586       set_has_current(false);
 587       return false;
 588     }
 589 
 590     if (relocInfo::have_format)  _format = current()->format();
 591     return true;
 592   }
 593 
 594   // accessors
 595   address      limit()        const { return _limit; }
 596   void     set_limit(address x);
 597   relocType    type()         const { return current()->type(); }
 598   int          format()       const { return (relocInfo::have_format) ? current()->format() : 0; }
 599   address      addr()         const { return _addr; }
 600   CompiledMethod*     code()  const { return _code; }
 601   nmethod*     code_as_nmethod() const;
 602   short*       data()         const { return _data; }
 603   int          datalen()      const { return _datalen; }
 604   bool     has_current()      const { return _datalen >= 0; }
 605 
 606   void       set_addr(address addr) { _addr = addr; }
 607   bool   addr_in_const()      const;
 608 
 609   address section_start(int n) const {
 610     assert(_section_start[n], "must be initialized");
 611     return _section_start[n];
 612   }
 613   address section_end(int n) const {
 614     assert(_section_end[n], "must be initialized");
 615     return _section_end[n];
 616   }
 617 
 618   // The address points to the affected displacement part of the instruction.
 619   // For RISC, this is just the whole instruction.
 620   // For Intel, this is an unaligned 32-bit word.
 621 
 622   // type-specific relocation accessors:  oop_Relocation* oop_reloc(), etc.
 623   #define EACH_TYPE(name)                               \
 624   inline name##_Relocation* name##_reloc();
 625   APPLY_TO_RELOCATIONS(EACH_TYPE)
 626   #undef EACH_TYPE
 627   // generic relocation accessor; switches on type to call the above
 628   Relocation* reloc();
 629 
 630   // CodeBlob's have relocation indexes for faster random access:
 631   static int locs_and_index_size(int code_size, int locs_size);
 632   // Store an index into [dest_start+dest_count..dest_end).
 633   // At dest_start[0..dest_count] is the actual relocation information.
 634   // Everything else up to dest_end is free space for the index.
 635   static void create_index(relocInfo* dest_begin, int dest_count, relocInfo* dest_end);
 636 
 637 #ifndef PRODUCT
 638  public:
 639   void print();
 640   void print_current();
 641 #endif
 642 };
 643 
 644 
 645 // A Relocation is a flyweight object allocated within a RelocationHolder.
 646 // It represents the relocation data of relocation record.
 647 // So, the RelocIterator unpacks relocInfos into Relocations.
 648 
 649 class Relocation VALUE_OBJ_CLASS_SPEC {
 650   friend class RelocationHolder;
 651   friend class RelocIterator;
 652 
 653  private:
 654   static void guarantee_size();
 655 
 656   // When a relocation has been created by a RelocIterator,
 657   // this field is non-null.  It allows the relocation to know
 658   // its context, such as the address to which it applies.
 659   RelocIterator* _binding;
 660 
 661  protected:
 662   RelocIterator* binding() const {
 663     assert(_binding != NULL, "must be bound");
 664     return _binding;
 665   }
 666   void set_binding(RelocIterator* b) {
 667     assert(_binding == NULL, "must be unbound");
 668     _binding = b;
 669     assert(_binding != NULL, "must now be bound");
 670   }
 671 
 672   Relocation() {
 673     _binding = NULL;
 674   }
 675 
 676   static RelocationHolder newHolder() {
 677     return RelocationHolder();
 678   }
 679 
 680  public:
 681   void* operator new(size_t size, const RelocationHolder& holder) throw() {
 682     if (size > sizeof(holder._relocbuf)) guarantee_size();
 683     assert((void* const *)holder.reloc() == &holder._relocbuf[0], "ptrs must agree");
 684     return holder.reloc();
 685   }
 686 
 687   // make a generic relocation for a given type (if possible)
 688   static RelocationHolder spec_simple(relocInfo::relocType rtype);
 689 
 690   // here is the type-specific hook which writes relocation data:
 691   virtual void pack_data_to(CodeSection* dest) { }
 692 
 693   // here is the type-specific hook which reads (unpacks) relocation data:
 694   virtual void unpack_data() {
 695     assert(datalen()==0 || type()==relocInfo::none, "no data here");
 696   }
 697 
 698  protected:
 699   // Helper functions for pack_data_to() and unpack_data().
 700 
 701   // Most of the compression logic is confined here.
 702   // (The "immediate data" mechanism of relocInfo works independently
 703   // of this stuff, and acts to further compress most 1-word data prefixes.)
 704 
 705   // A variable-width int is encoded as a short if it will fit in 16 bits.
 706   // The decoder looks at datalen to decide whether to unpack short or jint.
 707   // Most relocation records are quite simple, containing at most two ints.
 708 
 709   static bool is_short(jint x) { return x == (short)x; }
 710   static short* add_short(short* p, int x)  { *p++ = x; return p; }
 711   static short* add_jint (short* p, jint x) {
 712     *p++ = relocInfo::data0_from_int(x); *p++ = relocInfo::data1_from_int(x);
 713     return p;
 714   }
 715   static short* add_var_int(short* p, jint x) {   // add a variable-width int
 716     if (is_short(x))  p = add_short(p, x);
 717     else              p = add_jint (p, x);
 718     return p;
 719   }
 720 
 721   static short* pack_1_int_to(short* p, jint x0) {
 722     // Format is one of:  [] [x] [Xx]
 723     if (x0 != 0)  p = add_var_int(p, x0);
 724     return p;
 725   }
 726   int unpack_1_int() {
 727     assert(datalen() <= 2, "too much data");
 728     return relocInfo::jint_data_at(0, data(), datalen());
 729   }
 730 
 731   // With two ints, the short form is used only if both ints are short.
 732   short* pack_2_ints_to(short* p, jint x0, jint x1) {
 733     // Format is one of:  [] [x y?] [Xx Y?y]
 734     if (x0 == 0 && x1 == 0) {
 735       // no halfwords needed to store zeroes
 736     } else if (is_short(x0) && is_short(x1)) {
 737       // 1-2 halfwords needed to store shorts
 738       p = add_short(p, x0); if (x1!=0) p = add_short(p, x1);
 739     } else {
 740       // 3-4 halfwords needed to store jints
 741       p = add_jint(p, x0);             p = add_var_int(p, x1);
 742     }
 743     return p;
 744   }
 745   void unpack_2_ints(jint& x0, jint& x1) {
 746     int    dlen = datalen();
 747     short* dp  = data();
 748     if (dlen <= 2) {
 749       x0 = relocInfo::short_data_at(0, dp, dlen);
 750       x1 = relocInfo::short_data_at(1, dp, dlen);
 751     } else {
 752       assert(dlen <= 4, "too much data");
 753       x0 = relocInfo::jint_data_at(0, dp, dlen);
 754       x1 = relocInfo::jint_data_at(2, dp, dlen);
 755     }
 756   }
 757 
 758  protected:
 759   // platform-independent utility for patching constant section
 760   void       const_set_data_value    (address x);
 761   void       const_verify_data_value (address x);
 762   // platform-dependent utilities for decoding and patching instructions
 763   void       pd_set_data_value       (address x, intptr_t off, bool verify_only = false); // a set or mem-ref
 764   void       pd_verify_data_value    (address x, intptr_t off) { pd_set_data_value(x, off, true); }
 765   address    pd_call_destination     (address orig_addr = NULL);
 766   void       pd_set_call_destination (address x);
 767 
 768   // this extracts the address of an address in the code stream instead of the reloc data
 769   address* pd_address_in_code       ();
 770 
 771   // this extracts an address from the code stream instead of the reloc data
 772   address  pd_get_address_from_code ();
 773 
 774   // these convert from byte offsets, to scaled offsets, to addresses
 775   static jint scaled_offset(address x, address base) {
 776     int byte_offset = x - base;
 777     int offset = -byte_offset / relocInfo::addr_unit();
 778     assert(address_from_scaled_offset(offset, base) == x, "just checkin'");
 779     return offset;
 780   }
 781   static jint scaled_offset_null_special(address x, address base) {
 782     // Some relocations treat offset=0 as meaning NULL.
 783     // Handle this extra convention carefully.
 784     if (x == NULL)  return 0;
 785     assert(x != base, "offset must not be zero");
 786     return scaled_offset(x, base);
 787   }
 788   static address address_from_scaled_offset(jint offset, address base) {
 789     int byte_offset = -( offset * relocInfo::addr_unit() );
 790     return base + byte_offset;
 791   }
 792 
 793   // helpers for mapping between old and new addresses after a move or resize
 794   address old_addr_for(address newa, const CodeBuffer* src, CodeBuffer* dest);
 795   address new_addr_for(address olda, const CodeBuffer* src, CodeBuffer* dest);
 796   void normalize_address(address& addr, const CodeSection* dest, bool allow_other_sections = false);
 797 
 798  public:
 799   // accessors which only make sense for a bound Relocation
 800   address         addr()            const { return binding()->addr(); }
 801   CompiledMethod* code()            const { return binding()->code(); }
 802   nmethod*        code_as_nmethod() const { return binding()->code_as_nmethod(); }
 803   bool            addr_in_const()   const { return binding()->addr_in_const(); }
 804  protected:
 805   short*   data()         const { return binding()->data(); }
 806   int      datalen()      const { return binding()->datalen(); }
 807   int      format()       const { return binding()->format(); }
 808 
 809  public:
 810   virtual relocInfo::relocType type()            { return relocInfo::none; }
 811 
 812   // is it a call instruction?
 813   virtual bool is_call()                         { return false; }
 814 
 815   // is it a data movement instruction?
 816   virtual bool is_data()                         { return false; }
 817 
 818   // some relocations can compute their own values
 819   virtual address  value();
 820 
 821   // all relocations are able to reassert their values
 822   virtual void set_value(address x);
 823 
 824   virtual void clear_inline_cache()              { }
 825 
 826   // This method assumes that all virtual/static (inline) caches are cleared (since for static_call_type and
 827   // ic_call_type is not always posisition dependent (depending on the state of the cache)). However, this is
 828   // probably a reasonable assumption, since empty caches simplifies code reloacation.
 829   virtual void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) { }
 830 
 831   void print();
 832 };
 833 
 834 
 835 // certain inlines must be deferred until class Relocation is defined:
 836 
 837 inline RelocationHolder::RelocationHolder() {
 838   // initialize the vtbl, just to keep things type-safe
 839   new(*this) Relocation();
 840 }
 841 
 842 
 843 inline RelocationHolder::RelocationHolder(Relocation* r) {
 844   // wordwise copy from r (ok if it copies garbage after r)
 845   for (int i = 0; i < _relocbuf_size; i++) {
 846     _relocbuf[i] = ((void**)r)[i];
 847   }
 848 }
 849 
 850 
 851 relocInfo::relocType RelocationHolder::type() const {
 852   return reloc()->type();
 853 }
 854 
 855 // A DataRelocation always points at a memory or load-constant instruction..
 856 // It is absolute on most machines, and the constant is split on RISCs.
 857 // The specific subtypes are oop, external_word, and internal_word.
 858 // By convention, the "value" does not include a separately reckoned "offset".
 859 class DataRelocation : public Relocation {
 860  public:
 861   bool          is_data()                      { return true; }
 862 
 863   // both target and offset must be computed somehow from relocation data
 864   virtual int    offset()                      { return 0; }
 865   address         value()                      = 0;
 866   void        set_value(address x)             { set_value(x, offset()); }
 867   void        set_value(address x, intptr_t o) {
 868     if (addr_in_const())
 869       const_set_data_value(x);
 870     else
 871       pd_set_data_value(x, o);
 872   }
 873   void        verify_value(address x) {
 874     if (addr_in_const())
 875       const_verify_data_value(x);
 876     else
 877       pd_verify_data_value(x, offset());
 878   }
 879 
 880   // The "o" (displacement) argument is relevant only to split relocations
 881   // on RISC machines.  In some CPUs (SPARC), the set-hi and set-lo ins'ns
 882   // can encode more than 32 bits between them.  This allows compilers to
 883   // share set-hi instructions between addresses that differ by a small
 884   // offset (e.g., different static variables in the same class).
 885   // On such machines, the "x" argument to set_value on all set-lo
 886   // instructions must be the same as the "x" argument for the
 887   // corresponding set-hi instructions.  The "o" arguments for the
 888   // set-hi instructions are ignored, and must not affect the high-half
 889   // immediate constant.  The "o" arguments for the set-lo instructions are
 890   // added into the low-half immediate constant, and must not overflow it.
 891 };
 892 
 893 // A CallRelocation always points at a call instruction.
 894 // It is PC-relative on most machines.
 895 class CallRelocation : public Relocation {
 896  public:
 897   bool is_call() { return true; }
 898 
 899   address  destination()                    { return pd_call_destination(); }
 900   void     set_destination(address x); // pd_set_call_destination
 901 
 902   void     fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
 903   address  value()                          { return destination();  }
 904   void     set_value(address x)             { set_destination(x); }
 905 };
 906 
 907 class oop_Relocation : public DataRelocation {
 908   relocInfo::relocType type() { return relocInfo::oop_type; }
 909 
 910  public:
 911   // encode in one of these formats:  [] [n] [n l] [Nn l] [Nn Ll]
 912   // an oop in the CodeBlob's oop pool
 913   static RelocationHolder spec(int oop_index, int offset = 0) {
 914     assert(oop_index > 0, "must be a pool-resident oop");
 915     RelocationHolder rh = newHolder();
 916     new(rh) oop_Relocation(oop_index, offset);
 917     return rh;
 918   }
 919   // an oop in the instruction stream
 920   static RelocationHolder spec_for_immediate() {
 921     const int oop_index = 0;
 922     const int offset    = 0;    // if you want an offset, use the oop pool
 923     RelocationHolder rh = newHolder();
 924     new(rh) oop_Relocation(oop_index, offset);
 925     return rh;
 926   }
 927 
 928  private:
 929   jint _oop_index;                  // if > 0, index into CodeBlob::oop_at
 930   jint _offset;                     // byte offset to apply to the oop itself
 931 
 932   oop_Relocation(int oop_index, int offset) {
 933     _oop_index = oop_index; _offset = offset;
 934   }
 935 
 936   friend class RelocIterator;
 937   oop_Relocation() { }
 938 
 939  public:
 940   int oop_index() { return _oop_index; }
 941   int offset()    { return _offset; }
 942 
 943   // data is packed in "2_ints" format:  [i o] or [Ii Oo]
 944   void pack_data_to(CodeSection* dest);
 945   void unpack_data();
 946 
 947   void fix_oop_relocation();        // reasserts oop value
 948 
 949   void verify_oop_relocation();
 950 
 951   address value()  { return (address) *oop_addr(); }
 952 
 953   bool oop_is_immediate()  { return oop_index() == 0; }
 954 
 955   oop* oop_addr();                  // addr or &pool[jint_data]
 956   oop  oop_value();                 // *oop_addr
 957   // Note:  oop_value transparently converts Universe::non_oop_word to NULL.
 958 };
 959 
 960 
 961 // copy of oop_Relocation for now but may delete stuff in both/either
 962 class metadata_Relocation : public DataRelocation {
 963   relocInfo::relocType type() { return relocInfo::metadata_type; }
 964 
 965  public:
 966   // encode in one of these formats:  [] [n] [n l] [Nn l] [Nn Ll]
 967   // an metadata in the CodeBlob's metadata pool
 968   static RelocationHolder spec(int metadata_index, int offset = 0) {
 969     assert(metadata_index > 0, "must be a pool-resident metadata");
 970     RelocationHolder rh = newHolder();
 971     new(rh) metadata_Relocation(metadata_index, offset);
 972     return rh;
 973   }
 974   // an metadata in the instruction stream
 975   static RelocationHolder spec_for_immediate() {
 976     const int metadata_index = 0;
 977     const int offset    = 0;    // if you want an offset, use the metadata pool
 978     RelocationHolder rh = newHolder();
 979     new(rh) metadata_Relocation(metadata_index, offset);
 980     return rh;
 981   }
 982 
 983  private:
 984   jint _metadata_index;            // if > 0, index into nmethod::metadata_at
 985   jint _offset;                     // byte offset to apply to the metadata itself
 986 
 987   metadata_Relocation(int metadata_index, int offset) {
 988     _metadata_index = metadata_index; _offset = offset;
 989   }
 990 
 991   friend class RelocIterator;
 992   metadata_Relocation() { }
 993 
 994   // Fixes a Metadata pointer in the code. Most platforms embeds the
 995   // Metadata pointer in the code at compile time so this is empty
 996   // for them.
 997   void pd_fix_value(address x);
 998 
 999  public:
1000   int metadata_index() { return _metadata_index; }
1001   int offset()    { return _offset; }
1002 
1003   // data is packed in "2_ints" format:  [i o] or [Ii Oo]
1004   void pack_data_to(CodeSection* dest);
1005   void unpack_data();
1006 
1007   void fix_metadata_relocation();        // reasserts metadata value
1008 
1009   void verify_metadata_relocation();
1010 
1011   address value()  { return (address) *metadata_addr(); }
1012 
1013   bool metadata_is_immediate()  { return metadata_index() == 0; }
1014 
1015   Metadata**   metadata_addr();                  // addr or &pool[jint_data]
1016   Metadata*    metadata_value();                 // *metadata_addr
1017   // Note:  metadata_value transparently converts Universe::non_metadata_word to NULL.
1018 };
1019 
1020 
1021 class virtual_call_Relocation : public CallRelocation {
1022   relocInfo::relocType type() { return relocInfo::virtual_call_type; }
1023 
1024  public:
1025   // "cached_value" points to the first associated set-oop.
1026   // The oop_limit helps find the last associated set-oop.
1027   // (See comments at the top of this file.)
1028   static RelocationHolder spec(address cached_value, jint method_index = 0) {
1029     RelocationHolder rh = newHolder();
1030     new(rh) virtual_call_Relocation(cached_value, method_index);
1031     return rh;
1032   }
1033 
1034  private:
1035   address _cached_value; // location of set-value instruction
1036   jint    _method_index; // resolved method for a Java call
1037 
1038   virtual_call_Relocation(address cached_value, int method_index) {
1039     _cached_value = cached_value;
1040     _method_index = method_index;
1041     assert(cached_value != NULL, "first oop address must be specified");
1042   }
1043 
1044   friend class RelocIterator;
1045   virtual_call_Relocation() { }
1046 
1047  public:
1048   address cached_value();
1049 
1050   int     method_index() { return _method_index; }
1051   Method* method_value();
1052 
1053   // data is packed as scaled offsets in "2_ints" format:  [f l] or [Ff Ll]
1054   // oop_limit is set to 0 if the limit falls somewhere within the call.
1055   // When unpacking, a zero oop_limit is taken to refer to the end of the call.
1056   // (This has the effect of bringing in the call's delay slot on SPARC.)
1057   void pack_data_to(CodeSection* dest);
1058   void unpack_data();
1059 
1060   void clear_inline_cache();
1061 };
1062 
1063 
1064 class opt_virtual_call_Relocation : public CallRelocation {
1065   relocInfo::relocType type() { return relocInfo::opt_virtual_call_type; }
1066 
1067  public:
1068   static RelocationHolder spec(int method_index = 0) {
1069     RelocationHolder rh = newHolder();
1070     new(rh) opt_virtual_call_Relocation(method_index);
1071     return rh;
1072   }
1073 
1074  private:
1075   jint _method_index; // resolved method for a Java call
1076 
1077   opt_virtual_call_Relocation(int method_index) {
1078     _method_index = method_index;
1079   }
1080 
1081   friend class RelocIterator;
1082   opt_virtual_call_Relocation() {}
1083 
1084  public:
1085   int     method_index() { return _method_index; }
1086   Method* method_value();
1087 
1088   void pack_data_to(CodeSection* dest);
1089   void unpack_data();
1090 
1091   void clear_inline_cache();
1092 
1093   // find the matching static_stub
1094   address static_stub();
1095 };
1096 
1097 
1098 class static_call_Relocation : public CallRelocation {
1099   relocInfo::relocType type() { return relocInfo::static_call_type; }
1100 
1101  public:
1102   static RelocationHolder spec(int method_index = 0) {
1103     RelocationHolder rh = newHolder();
1104     new(rh) static_call_Relocation(method_index);
1105     return rh;
1106   }
1107 
1108  private:
1109   jint _method_index; // resolved method for a Java call
1110 
1111   static_call_Relocation(int method_index) {
1112     _method_index = method_index;
1113   }
1114 
1115   friend class RelocIterator;
1116   static_call_Relocation() {}
1117 
1118  public:
1119   int     method_index() { return _method_index; }
1120   Method* method_value();
1121 
1122   void pack_data_to(CodeSection* dest);
1123   void unpack_data();
1124 
1125   void clear_inline_cache();
1126 
1127   // find the matching static_stub
1128   address static_stub();
1129 };
1130 
1131 class static_stub_Relocation : public Relocation {
1132   relocInfo::relocType type() { return relocInfo::static_stub_type; }
1133 
1134  public:
1135   static RelocationHolder spec(address static_call) {
1136     RelocationHolder rh = newHolder();
1137     new(rh) static_stub_Relocation(static_call);
1138     return rh;
1139   }
1140 
1141  private:
1142   address _static_call;  // location of corresponding static_call
1143 
1144   static_stub_Relocation(address static_call) {
1145     _static_call = static_call;
1146   }
1147 
1148   friend class RelocIterator;
1149   static_stub_Relocation() { }
1150 
1151  public:
1152   void clear_inline_cache();
1153 
1154   address static_call() { return _static_call; }
1155 
1156   // data is packed as a scaled offset in "1_int" format:  [c] or [Cc]
1157   void pack_data_to(CodeSection* dest);
1158   void unpack_data();
1159 };
1160 
1161 class runtime_call_Relocation : public CallRelocation {
1162   relocInfo::relocType type() { return relocInfo::runtime_call_type; }
1163 
1164  public:
1165   static RelocationHolder spec() {
1166     RelocationHolder rh = newHolder();
1167     new(rh) runtime_call_Relocation();
1168     return rh;
1169   }
1170 
1171  private:
1172   friend class RelocIterator;
1173   runtime_call_Relocation() { }
1174 
1175  public:
1176 };
1177 
1178 // Trampoline Relocations.
1179 // A trampoline allows to encode a small branch in the code, even if there
1180 // is the chance that this branch can not reach all possible code locations.
1181 // If the relocation finds that a branch is too far for the instruction
1182 // in the code, it can patch it to jump to the trampoline where is
1183 // sufficient space for a far branch. Needed on PPC.
1184 class trampoline_stub_Relocation : public Relocation {
1185   relocInfo::relocType type() { return relocInfo::trampoline_stub_type; }
1186 
1187  public:
1188   static RelocationHolder spec(address static_call) {
1189     RelocationHolder rh = newHolder();
1190     return (new (rh) trampoline_stub_Relocation(static_call));
1191   }
1192 
1193  private:
1194   address _owner;    // Address of the NativeCall that owns the trampoline.
1195 
1196   trampoline_stub_Relocation(address owner) {
1197     _owner = owner;
1198   }
1199 
1200   friend class RelocIterator;
1201   trampoline_stub_Relocation() { }
1202 
1203  public:
1204 
1205   // Return the address of the NativeCall that owns the trampoline.
1206   address owner() { return _owner; }
1207 
1208   void pack_data_to(CodeSection * dest);
1209   void unpack_data();
1210 
1211   // Find the trampoline stub for a call.
1212   static address get_trampoline_for(address call, nmethod* code);
1213 };
1214 
1215 class external_word_Relocation : public DataRelocation {
1216   relocInfo::relocType type() { return relocInfo::external_word_type; }
1217 
1218  public:
1219   static RelocationHolder spec(address target) {
1220     assert(target != NULL, "must not be null");
1221     RelocationHolder rh = newHolder();
1222     new(rh) external_word_Relocation(target);
1223     return rh;
1224   }
1225 
1226   // Use this one where all 32/64 bits of the target live in the code stream.
1227   // The target must be an intptr_t, and must be absolute (not relative).
1228   static RelocationHolder spec_for_immediate() {
1229     RelocationHolder rh = newHolder();
1230     new(rh) external_word_Relocation(NULL);
1231     return rh;
1232   }
1233 
1234   // Some address looking values aren't safe to treat as relocations
1235   // and should just be treated as constants.
1236   static bool can_be_relocated(address target) {
1237     assert(target == NULL || (uintptr_t)target >= (uintptr_t)os::vm_page_size(), INTPTR_FORMAT, (intptr_t)target);
1238     return target != NULL;
1239   }
1240 
1241  private:
1242   address _target;                  // address in runtime
1243 
1244   external_word_Relocation(address target) {
1245     _target = target;
1246   }
1247 
1248   friend class RelocIterator;
1249   external_word_Relocation() { }
1250 
1251  public:
1252   // data is packed as a well-known address in "1_int" format:  [a] or [Aa]
1253   // The function runtime_address_to_index is used to turn full addresses
1254   // to short indexes, if they are pre-registered by the stub mechanism.
1255   // If the "a" value is 0 (i.e., _target is NULL), the address is stored
1256   // in the code stream.  See external_word_Relocation::target().
1257   void pack_data_to(CodeSection* dest);
1258   void unpack_data();
1259 
1260   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1261   address  target();        // if _target==NULL, fetch addr from code stream
1262   address  value()          { return target(); }
1263 };
1264 
1265 class internal_word_Relocation : public DataRelocation {
1266   relocInfo::relocType type() { return relocInfo::internal_word_type; }
1267 
1268  public:
1269   static RelocationHolder spec(address target) {
1270     assert(target != NULL, "must not be null");
1271     RelocationHolder rh = newHolder();
1272     new(rh) internal_word_Relocation(target);
1273     return rh;
1274   }
1275 
1276   // use this one where all the bits of the target can fit in the code stream:
1277   static RelocationHolder spec_for_immediate() {
1278     RelocationHolder rh = newHolder();
1279     new(rh) internal_word_Relocation(NULL);
1280     return rh;
1281   }
1282 
1283   internal_word_Relocation(address target) {
1284     _target  = target;
1285     _section = -1;  // self-relative
1286   }
1287 
1288  protected:
1289   address _target;                  // address in CodeBlob
1290   int     _section;                 // section providing base address, if any
1291 
1292   friend class RelocIterator;
1293   internal_word_Relocation() { }
1294 
1295   // bit-width of LSB field in packed offset, if section >= 0
1296   enum { section_width = 2 }; // must equal CodeBuffer::sect_bits
1297 
1298  public:
1299   // data is packed as a scaled offset in "1_int" format:  [o] or [Oo]
1300   // If the "o" value is 0 (i.e., _target is NULL), the offset is stored
1301   // in the code stream.  See internal_word_Relocation::target().
1302   // If _section is not -1, it is appended to the low bits of the offset.
1303   void pack_data_to(CodeSection* dest);
1304   void unpack_data();
1305 
1306   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1307   address  target();        // if _target==NULL, fetch addr from code stream
1308   int      section()        { return _section;   }
1309   address  value()          { return target();   }
1310 };
1311 
1312 class section_word_Relocation : public internal_word_Relocation {
1313   relocInfo::relocType type() { return relocInfo::section_word_type; }
1314 
1315  public:
1316   static RelocationHolder spec(address target, int section) {
1317     RelocationHolder rh = newHolder();
1318     new(rh) section_word_Relocation(target, section);
1319     return rh;
1320   }
1321 
1322   section_word_Relocation(address target, int section) {
1323     assert(target != NULL, "must not be null");
1324     assert(section >= 0, "must be a valid section");
1325     _target  = target;
1326     _section = section;
1327   }
1328 
1329   //void pack_data_to -- inherited
1330   void unpack_data();
1331 
1332  private:
1333   friend class RelocIterator;
1334   section_word_Relocation() { }
1335 };
1336 
1337 
1338 class poll_Relocation : public Relocation {
1339   bool          is_data()                      { return true; }
1340   relocInfo::relocType type() { return relocInfo::poll_type; }
1341   void     fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1342 };
1343 
1344 class poll_return_Relocation : public poll_Relocation {
1345   relocInfo::relocType type() { return relocInfo::poll_return_type; }
1346 };
1347 
1348 // We know all the xxx_Relocation classes, so now we can define these:
1349 #define EACH_CASE(name)                                         \
1350 inline name##_Relocation* RelocIterator::name##_reloc() {       \
1351   assert(type() == relocInfo::name##_type, "type must agree");  \
1352   /* The purpose of the placed "new" is to re-use the same */   \
1353   /* stack storage for each new iteration. */                   \
1354   name##_Relocation* r = new(_rh) name##_Relocation();          \
1355   r->set_binding(this);                                         \
1356   r->name##_Relocation::unpack_data();                          \
1357   return r;                                                     \
1358 }
1359 APPLY_TO_RELOCATIONS(EACH_CASE);
1360 #undef EACH_CASE
1361 
1362 inline RelocIterator::RelocIterator(CompiledMethod* nm, address begin, address limit) {
1363   initialize(nm, begin, limit);
1364 }
1365 
1366 #endif // SHARE_VM_CODE_RELOCINFO_HPP