view src/share/vm/oops/methodDataOop.cpp @ 4155:394404b2d9bd

Removed strict requirement for GRAAL environment variable. It only needs to be set now if the graal directory is not in the directory hierarchy of GraalVM JDK.
author Doug Simon <doug.simon@oracle.com>
date Wed, 21 Dec 2011 11:25:27 +0100
parents a97fd181b813
children f7251c729b31
line wrap: on
line source

/*
 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/systemDictionary.hpp"
#include "gc_implementation/shared/markSweep.inline.hpp"
#include "interpreter/bytecode.hpp"
#include "interpreter/bytecodeStream.hpp"
#include "interpreter/linkResolver.hpp"
#include "oops/methodDataOop.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/compilationPolicy.hpp"
#include "runtime/deoptimization.hpp"
#include "runtime/handles.inline.hpp"

// ==================================================================
// DataLayout
//
// Overlay for generic profiling data.

// Some types of data layouts need a length field.
bool DataLayout::needs_array_len(u1 tag) {
  return (tag == multi_branch_data_tag) || (tag == arg_info_data_tag);
}

// Perform generic initialization of the data.  More specific
// initialization occurs in overrides of ProfileData::post_initialize.
void DataLayout::initialize(u1 tag, u2 bci, int cell_count) {
  _header._bits = (intptr_t)0;
  _header._struct._tag = tag;
  _header._struct._bci = bci;
  for (int i = 0; i < cell_count; i++) {
    set_cell_at(i, (intptr_t)0);
  }
  if (needs_array_len(tag)) {
    set_cell_at(ArrayData::array_len_off_set, cell_count - 1); // -1 for header.
  }
}

void DataLayout::follow_weak_refs(BoolObjectClosure* cl) {
  ResourceMark m;
  data_in()->follow_weak_refs(cl);
}


// ==================================================================
// ProfileData
//
// A ProfileData object is created to refer to a section of profiling
// data in a structured way.

// Constructor for invalid ProfileData.
ProfileData::ProfileData() {
  _data = NULL;
}

#ifndef PRODUCT
void ProfileData::print_shared(outputStream* st, const char* name) {
  st->print("bci: %d", bci());
  st->fill_to(tab_width_one);
  st->print("%s", name);
  tab(st);
  int trap = trap_state();
  if (trap != 0) {
    char buf[100];
    st->print("trap(%s) ", Deoptimization::format_trap_state(buf, sizeof(buf), trap));
  }
  int flags = data()->flags();
  if (flags != 0)
    st->print("flags(%d) ", flags);
}

void ProfileData::tab(outputStream* st) {
  st->fill_to(tab_width_two);
}
#endif // !PRODUCT

// ==================================================================
// BitData
//
// A BitData corresponds to a one-bit flag.  This is used to indicate
// whether a checkcast bytecode has seen a null value.


#ifndef PRODUCT
void BitData::print_data_on(outputStream* st) {
  print_shared(st, "BitData");
}
#endif // !PRODUCT

// ==================================================================
// CounterData
//
// A CounterData corresponds to a simple counter.

#ifndef PRODUCT
void CounterData::print_data_on(outputStream* st) {
  print_shared(st, "CounterData");
  st->print_cr("count(%u)", count());
}
#endif // !PRODUCT

// ==================================================================
// JumpData
//
// A JumpData is used to access profiling information for a direct
// branch.  It is a counter, used for counting the number of branches,
// plus a data displacement, used for realigning the data pointer to
// the corresponding target bci.

void JumpData::post_initialize(BytecodeStream* stream, methodDataOop mdo) {
  assert(stream->bci() == bci(), "wrong pos");
  int target;
  Bytecodes::Code c = stream->code();
  if (c == Bytecodes::_goto_w || c == Bytecodes::_jsr_w) {
    target = stream->dest_w();
  } else {
    target = stream->dest();
  }
  int my_di = mdo->dp_to_di(dp());
  int target_di = mdo->bci_to_di(target);
  int offset = target_di - my_di;
  set_displacement(offset);
}

#ifndef PRODUCT
void JumpData::print_data_on(outputStream* st) {
  print_shared(st, "JumpData");
  st->print_cr("taken(%u) displacement(%d)", taken(), displacement());
}
#endif // !PRODUCT

// ==================================================================
// ReceiverTypeData
//
// A ReceiverTypeData is used to access profiling information about a
// dynamic type check.  It consists of a counter which counts the total times
// that the check is reached, and a series of (klassOop, count) pairs
// which are used to store a type profile for the receiver of the check.

void ReceiverTypeData::follow_contents() {
  // This is a set of weak references that need
  // to be followed at the end of the strong marking
  // phase. Memoize this object so it can be visited
  // in the weak roots processing phase.
  MarkSweep::revisit_mdo(data());
}

#ifndef SERIALGC
void ReceiverTypeData::follow_contents(ParCompactionManager* cm) {
  // This is a set of weak references that need
  // to be followed at the end of the strong marking
  // phase. Memoize this object so it can be visited
  // in the weak roots processing phase.
  PSParallelCompact::revisit_mdo(cm, data());
}
#endif // SERIALGC

void ReceiverTypeData::oop_iterate(OopClosure* blk) {
  if (blk->should_remember_mdo()) {
    // This is a set of weak references that need
    // to be followed at the end of the strong marking
    // phase. Memoize this object so it can be visited
    // in the weak roots processing phase.
    blk->remember_mdo(data());
  } else { // normal scan
    for (uint row = 0; row < row_limit(); row++) {
      if (receiver(row) != NULL) {
        oop* adr = adr_receiver(row);
        blk->do_oop(adr);
      }
    }
  }
}

void ReceiverTypeData::oop_iterate_m(OopClosure* blk, MemRegion mr) {
  // Currently, this interface is called only during card-scanning for
  // a young gen gc, in which case this object cannot contribute anything,
  // since it does not contain any references that cross out of
  // the perm gen. However, for future more general use we allow
  // the possibility of calling for instance from more general
  // iterators (for example, a future regionalized perm gen for G1,
  // or the possibility of moving some references out of perm in
  // the case of other collectors). In that case, you will need
  // to relax or remove some of the assertions below.
#ifdef ASSERT
  // Verify that none of the embedded oop references cross out of
  // this generation.
  for (uint row = 0; row < row_limit(); row++) {
    if (receiver(row) != NULL) {
      oop* adr = adr_receiver(row);
      CollectedHeap* h = Universe::heap();
      assert(h->is_permanent(adr) && h->is_permanent_or_null(*adr), "Not intra-perm");
    }
  }
#endif // ASSERT
  assert(!blk->should_remember_mdo(), "Not expected to remember MDO");
  return;   // Nothing to do, see comment above
#if 0
  if (blk->should_remember_mdo()) {
    // This is a set of weak references that need
    // to be followed at the end of the strong marking
    // phase. Memoize this object so it can be visited
    // in the weak roots processing phase.
    blk->remember_mdo(data());
  } else { // normal scan
    for (uint row = 0; row < row_limit(); row++) {
      if (receiver(row) != NULL) {
        oop* adr = adr_receiver(row);
        if (mr.contains(adr)) {
          blk->do_oop(adr);
        } else if ((HeapWord*)adr >= mr.end()) {
          // Test that the current cursor and the two ends of the range
          // that we may have skipped iterating over are monotonically ordered;
          // this is just a paranoid assertion, just in case represetations
          // should change in the future rendering the short-circuit return
          // here invalid.
          assert((row+1 >= row_limit() || adr_receiver(row+1) > adr) &&
                 (row+2 >= row_limit() || adr_receiver(row_limit()-1) > adr_receiver(row+1)), "Reducing?");
          break; // remaining should be outside this mr too
        }
      }
    }
  }
#endif
}

void ReceiverTypeData::adjust_pointers() {
  for (uint row = 0; row < row_limit(); row++) {
    if (receiver(row) != NULL) {
      MarkSweep::adjust_pointer(adr_receiver(row));
    }
  }
}

void ReceiverTypeData::follow_weak_refs(BoolObjectClosure* is_alive_cl) {
  for (uint row = 0; row < row_limit(); row++) {
    klassOop p = receiver(row);
    if (p != NULL && !is_alive_cl->do_object_b(p)) {
      clear_row(row);
    }
  }
}

#ifndef SERIALGC
void ReceiverTypeData::update_pointers() {
  for (uint row = 0; row < row_limit(); row++) {
    if (receiver_unchecked(row) != NULL) {
      PSParallelCompact::adjust_pointer(adr_receiver(row));
    }
  }
}
#endif // SERIALGC

#ifndef PRODUCT
void ReceiverTypeData::print_receiver_data_on(outputStream* st) {
  uint row;
  int entries = 0;
  for (row = 0; row < row_limit(); row++) {
    if (receiver(row) != NULL)  entries++;
  }
  st->print_cr("count(%u) entries(%u)", count(), entries);
  int total = count();
  for (row = 0; row < row_limit(); row++) {
    if (receiver(row) != NULL) {
      total += receiver_count(row);
    }
  }
  for (row = 0; row < row_limit(); row++) {
    if (receiver(row) != NULL) {
      tab(st);
      receiver(row)->print_value_on(st);
      st->print_cr("(%u %4.2f)", receiver_count(row), (float) receiver_count(row) / (float) total);
    }
  }
}
void ReceiverTypeData::print_data_on(outputStream* st) {
  print_shared(st, "ReceiverTypeData");
  print_receiver_data_on(st);
}
void VirtualCallData::print_data_on(outputStream* st) {
  print_shared(st, "VirtualCallData");
  print_receiver_data_on(st);
}
#endif // !PRODUCT

// ==================================================================
// RetData
//
// A RetData is used to access profiling information for a ret bytecode.
// It is composed of a count of the number of times that the ret has
// been executed, followed by a series of triples of the form
// (bci, count, di) which count the number of times that some bci was the
// target of the ret and cache a corresponding displacement.

void RetData::post_initialize(BytecodeStream* stream, methodDataOop mdo) {
  for (uint row = 0; row < row_limit(); row++) {
    set_bci_displacement(row, -1);
    set_bci(row, no_bci);
  }
  // release so other threads see a consistent state.  bci is used as
  // a valid flag for bci_displacement.
  OrderAccess::release();
}

// This routine needs to atomically update the RetData structure, so the
// caller needs to hold the RetData_lock before it gets here.  Since taking
// the lock can block (and allow GC) and since RetData is a ProfileData is a
// wrapper around a derived oop, taking the lock in _this_ method will
// basically cause the 'this' pointer's _data field to contain junk after the
// lock.  We require the caller to take the lock before making the ProfileData
// structure.  Currently the only caller is InterpreterRuntime::update_mdp_for_ret
address RetData::fixup_ret(int return_bci, methodDataHandle h_mdo) {
  // First find the mdp which corresponds to the return bci.
  address mdp = h_mdo->bci_to_dp(return_bci);

  // Now check to see if any of the cache slots are open.
  for (uint row = 0; row < row_limit(); row++) {
    if (bci(row) == no_bci) {
      set_bci_displacement(row, mdp - dp());
      set_bci_count(row, DataLayout::counter_increment);
      // Barrier to ensure displacement is written before the bci; allows
      // the interpreter to read displacement without fear of race condition.
      release_set_bci(row, return_bci);
      break;
    }
  }
  return mdp;
}


#ifndef PRODUCT
void RetData::print_data_on(outputStream* st) {
  print_shared(st, "RetData");
  uint row;
  int entries = 0;
  for (row = 0; row < row_limit(); row++) {
    if (bci(row) != no_bci)  entries++;
  }
  st->print_cr("count(%u) entries(%u)", count(), entries);
  for (row = 0; row < row_limit(); row++) {
    if (bci(row) != no_bci) {
      tab(st);
      st->print_cr("bci(%d: count(%u) displacement(%d))",
                   bci(row), bci_count(row), bci_displacement(row));
    }
  }
}
#endif // !PRODUCT

// ==================================================================
// BranchData
//
// A BranchData is used to access profiling data for a two-way branch.
// It consists of taken and not_taken counts as well as a data displacement
// for the taken case.

void BranchData::post_initialize(BytecodeStream* stream, methodDataOop mdo) {
  assert(stream->bci() == bci(), "wrong pos");
  int target = stream->dest();
  int my_di = mdo->dp_to_di(dp());
  int target_di = mdo->bci_to_di(target);
  int offset = target_di - my_di;
  set_displacement(offset);
}

#ifndef PRODUCT
void BranchData::print_data_on(outputStream* st) {
  print_shared(st, "BranchData");
  st->print_cr("taken(%u) displacement(%d)",
               taken(), displacement());
  tab(st);
  st->print_cr("not taken(%u)", not_taken());
}
#endif

// ==================================================================
// MultiBranchData
//
// A MultiBranchData is used to access profiling information for
// a multi-way branch (*switch bytecodes).  It consists of a series
// of (count, displacement) pairs, which count the number of times each
// case was taken and specify the data displacment for each branch target.

int MultiBranchData::compute_cell_count(BytecodeStream* stream) {
  int cell_count = 0;
  if (stream->code() == Bytecodes::_tableswitch) {
    Bytecode_tableswitch sw(stream->method()(), stream->bcp());
    cell_count = 1 + per_case_cell_count * (1 + sw.length()); // 1 for default
  } else {
    Bytecode_lookupswitch sw(stream->method()(), stream->bcp());
    cell_count = 1 + per_case_cell_count * (sw.number_of_pairs() + 1); // 1 for default
  }
  return cell_count;
}

void MultiBranchData::post_initialize(BytecodeStream* stream,
                                      methodDataOop mdo) {
  assert(stream->bci() == bci(), "wrong pos");
  int target;
  int my_di;
  int target_di;
  int offset;
  if (stream->code() == Bytecodes::_tableswitch) {
    Bytecode_tableswitch sw(stream->method()(), stream->bcp());
    int len = sw.length();
    assert(array_len() == per_case_cell_count * (len + 1), "wrong len");
    for (int count = 0; count < len; count++) {
      target = sw.dest_offset_at(count) + bci();
      my_di = mdo->dp_to_di(dp());
      target_di = mdo->bci_to_di(target);
      offset = target_di - my_di;
      set_displacement_at(count, offset);
    }
    target = sw.default_offset() + bci();
    my_di = mdo->dp_to_di(dp());
    target_di = mdo->bci_to_di(target);
    offset = target_di - my_di;
    set_default_displacement(offset);

  } else {
    Bytecode_lookupswitch sw(stream->method()(), stream->bcp());
    int npairs = sw.number_of_pairs();
    assert(array_len() == per_case_cell_count * (npairs + 1), "wrong len");
    for (int count = 0; count < npairs; count++) {
      LookupswitchPair pair = sw.pair_at(count);
      target = pair.offset() + bci();
      my_di = mdo->dp_to_di(dp());
      target_di = mdo->bci_to_di(target);
      offset = target_di - my_di;
      set_displacement_at(count, offset);
    }
    target = sw.default_offset() + bci();
    my_di = mdo->dp_to_di(dp());
    target_di = mdo->bci_to_di(target);
    offset = target_di - my_di;
    set_default_displacement(offset);
  }
}

#ifndef PRODUCT
void MultiBranchData::print_data_on(outputStream* st) {
  print_shared(st, "MultiBranchData");
  st->print_cr("default_count(%u) displacement(%d)",
               default_count(), default_displacement());
  int cases = number_of_cases();
  for (int i = 0; i < cases; i++) {
    tab(st);
    st->print_cr("count(%u) displacement(%d)",
                 count_at(i), displacement_at(i));
  }
}
#endif

#ifndef PRODUCT
void ArgInfoData::print_data_on(outputStream* st) {
  print_shared(st, "ArgInfoData");
  int nargs = number_of_args();
  for (int i = 0; i < nargs; i++) {
    st->print("  0x%x", arg_modified(i));
  }
  st->cr();
}

#endif
// ==================================================================
// methodDataOop
//
// A methodDataOop holds information which has been collected about
// a method.

int methodDataOopDesc::bytecode_cell_count(Bytecodes::Code code) {
  switch (code) {
  case Bytecodes::_checkcast:
  case Bytecodes::_instanceof:
  case Bytecodes::_aastore:
    if (TypeProfileCasts) {
      return ReceiverTypeData::static_cell_count();
    } else {
      return BitData::static_cell_count();
    }
  case Bytecodes::_invokespecial:
  case Bytecodes::_invokestatic:
    return CounterData::static_cell_count();
  case Bytecodes::_goto:
  case Bytecodes::_goto_w:
  case Bytecodes::_jsr:
  case Bytecodes::_jsr_w:
    return JumpData::static_cell_count();
  case Bytecodes::_invokevirtual:
  case Bytecodes::_invokeinterface:
    return VirtualCallData::static_cell_count();
  case Bytecodes::_invokedynamic:
    return CounterData::static_cell_count();
  case Bytecodes::_ret:
    return RetData::static_cell_count();
  case Bytecodes::_ifeq:
  case Bytecodes::_ifne:
  case Bytecodes::_iflt:
  case Bytecodes::_ifge:
  case Bytecodes::_ifgt:
  case Bytecodes::_ifle:
  case Bytecodes::_if_icmpeq:
  case Bytecodes::_if_icmpne:
  case Bytecodes::_if_icmplt:
  case Bytecodes::_if_icmpge:
  case Bytecodes::_if_icmpgt:
  case Bytecodes::_if_icmple:
  case Bytecodes::_if_acmpeq:
  case Bytecodes::_if_acmpne:
  case Bytecodes::_ifnull:
  case Bytecodes::_ifnonnull:
    return BranchData::static_cell_count();
  case Bytecodes::_lookupswitch:
  case Bytecodes::_tableswitch:
    return variable_cell_count;
  }
  return no_profile_data;
}

// Compute the size of the profiling information corresponding to
// the current bytecode.
int methodDataOopDesc::compute_data_size(BytecodeStream* stream) {
  int cell_count = bytecode_cell_count(stream->code());
  if (cell_count == no_profile_data) {
    return 0;
  }
  if (cell_count == variable_cell_count) {
    cell_count = MultiBranchData::compute_cell_count(stream);
  }
  // Note:  cell_count might be zero, meaning that there is just
  //        a DataLayout header, with no extra cells.
  assert(cell_count >= 0, "sanity");
  return DataLayout::compute_size_in_bytes(cell_count);
}

int methodDataOopDesc::compute_extra_data_count(int data_size, int empty_bc_count) {
  if (ProfileTraps) {
    // Assume that up to 3% of BCIs with no MDP will need to allocate one.
    int extra_data_count = (uint)(empty_bc_count * 3) / 128 + 1;
    // If the method is large, let the extra BCIs grow numerous (to ~1%).
    int one_percent_of_data
      = (uint)data_size / (DataLayout::header_size_in_bytes()*128);
    if (extra_data_count < one_percent_of_data)
      extra_data_count = one_percent_of_data;
    if (extra_data_count > empty_bc_count)
      extra_data_count = empty_bc_count;  // no need for more
    return extra_data_count;
  } else {
    return 0;
  }
}

// Compute the size of the methodDataOop necessary to store
// profiling information about a given method.  Size is in bytes.
int methodDataOopDesc::compute_allocation_size_in_bytes(methodHandle method) {
  int data_size = 0;
  BytecodeStream stream(method);
  Bytecodes::Code c;
  int empty_bc_count = 0;  // number of bytecodes lacking data
  while ((c = stream.next()) >= 0) {
    int size_in_bytes = compute_data_size(&stream);
    data_size += size_in_bytes;
    if (size_in_bytes == 0)  empty_bc_count += 1;
  }
  int object_size = in_bytes(data_offset()) + data_size;

  // Add some extra DataLayout cells (at least one) to track stray traps.
  int extra_data_count = compute_extra_data_count(data_size, empty_bc_count);
  object_size += extra_data_count * DataLayout::compute_size_in_bytes(0);

  // Add a cell to record information about modified arguments.
  int arg_size = method->size_of_parameters();
  object_size += DataLayout::compute_size_in_bytes(arg_size+1);
  return object_size;
}

// Compute the size of the methodDataOop necessary to store
// profiling information about a given method.  Size is in words
int methodDataOopDesc::compute_allocation_size_in_words(methodHandle method) {
  int byte_size = compute_allocation_size_in_bytes(method);
  int word_size = align_size_up(byte_size, BytesPerWord) / BytesPerWord;
  return align_object_size(word_size);
}

// Initialize an individual data segment.  Returns the size of
// the segment in bytes.
int methodDataOopDesc::initialize_data(BytecodeStream* stream,
                                       int data_index) {
  int cell_count = -1;
  int tag = DataLayout::no_tag;
  DataLayout* data_layout = data_layout_at(data_index);
  Bytecodes::Code c = stream->code();
  switch (c) {
  case Bytecodes::_checkcast:
  case Bytecodes::_instanceof:
  case Bytecodes::_aastore:
    if (TypeProfileCasts) {
      cell_count = ReceiverTypeData::static_cell_count();
      tag = DataLayout::receiver_type_data_tag;
    } else {
      cell_count = BitData::static_cell_count();
      tag = DataLayout::bit_data_tag;
    }
    break;
  case Bytecodes::_invokespecial:
  case Bytecodes::_invokestatic:
    cell_count = CounterData::static_cell_count();
    tag = DataLayout::counter_data_tag;
    break;
  case Bytecodes::_goto:
  case Bytecodes::_goto_w:
  case Bytecodes::_jsr:
  case Bytecodes::_jsr_w:
    cell_count = JumpData::static_cell_count();
    tag = DataLayout::jump_data_tag;
    break;
  case Bytecodes::_invokevirtual:
  case Bytecodes::_invokeinterface:
    cell_count = VirtualCallData::static_cell_count();
    tag = DataLayout::virtual_call_data_tag;
    break;
  case Bytecodes::_invokedynamic:
    // %%% should make a type profile for any invokedynamic that takes a ref argument
    cell_count = CounterData::static_cell_count();
    tag = DataLayout::counter_data_tag;
    break;
  case Bytecodes::_ret:
    cell_count = RetData::static_cell_count();
    tag = DataLayout::ret_data_tag;
    break;
  case Bytecodes::_ifeq:
  case Bytecodes::_ifne:
  case Bytecodes::_iflt:
  case Bytecodes::_ifge:
  case Bytecodes::_ifgt:
  case Bytecodes::_ifle:
  case Bytecodes::_if_icmpeq:
  case Bytecodes::_if_icmpne:
  case Bytecodes::_if_icmplt:
  case Bytecodes::_if_icmpge:
  case Bytecodes::_if_icmpgt:
  case Bytecodes::_if_icmple:
  case Bytecodes::_if_acmpeq:
  case Bytecodes::_if_acmpne:
  case Bytecodes::_ifnull:
  case Bytecodes::_ifnonnull:
    cell_count = BranchData::static_cell_count();
    tag = DataLayout::branch_data_tag;
    break;
  case Bytecodes::_lookupswitch:
  case Bytecodes::_tableswitch:
    cell_count = MultiBranchData::compute_cell_count(stream);
    tag = DataLayout::multi_branch_data_tag;
    break;
  }
  assert(tag == DataLayout::multi_branch_data_tag ||
         cell_count == bytecode_cell_count(c), "cell counts must agree");
  if (cell_count >= 0) {
    assert(tag != DataLayout::no_tag, "bad tag");
    assert(bytecode_has_profile(c), "agree w/ BHP");
    data_layout->initialize(tag, stream->bci(), cell_count);
    return DataLayout::compute_size_in_bytes(cell_count);
  } else {
    assert(!bytecode_has_profile(c), "agree w/ !BHP");
    return 0;
  }
}

// Get the data at an arbitrary (sort of) data index.
ProfileData* methodDataOopDesc::data_at(int data_index) {
  if (out_of_bounds(data_index)) {
    return NULL;
  }
  DataLayout* data_layout = data_layout_at(data_index);
  return data_layout->data_in();
}

ProfileData* DataLayout::data_in() {
  switch (tag()) {
  case DataLayout::no_tag:
  default:
    ShouldNotReachHere();
    return NULL;
  case DataLayout::bit_data_tag:
    return new BitData(this);
  case DataLayout::counter_data_tag:
    return new CounterData(this);
  case DataLayout::jump_data_tag:
    return new JumpData(this);
  case DataLayout::receiver_type_data_tag:
    return new ReceiverTypeData(this);
  case DataLayout::virtual_call_data_tag:
    return new VirtualCallData(this);
  case DataLayout::ret_data_tag:
    return new RetData(this);
  case DataLayout::branch_data_tag:
    return new BranchData(this);
  case DataLayout::multi_branch_data_tag:
    return new MultiBranchData(this);
  case DataLayout::arg_info_data_tag:
    return new ArgInfoData(this);
  };
}

// Iteration over data.
ProfileData* methodDataOopDesc::next_data(ProfileData* current) {
  int current_index = dp_to_di(current->dp());
  int next_index = current_index + current->size_in_bytes();
  ProfileData* next = data_at(next_index);
  return next;
}

// Give each of the data entries a chance to perform specific
// data initialization.
void methodDataOopDesc::post_initialize(BytecodeStream* stream) {
  ResourceMark rm;
  ProfileData* data;
  for (data = first_data(); is_valid(data); data = next_data(data)) {
    stream->set_start(data->bci());
    stream->next();
    data->post_initialize(stream, this);
  }
}

// Initialize the methodDataOop corresponding to a given method.
void methodDataOopDesc::initialize(methodHandle method) {
  ResourceMark rm;
  // Set the method back-pointer.
  _method = method();

  if (TieredCompilation) {
    _invocation_counter.init();
    _backedge_counter.init();
    _invocation_counter_start = 0;
    _backedge_counter_start = 0;
    _num_loops = 0;
    _num_blocks = 0;
    _highest_comp_level = 0;
    _highest_osr_comp_level = 0;
    _would_profile = true;
  }
  set_creation_mileage(mileage_of(method()));

  // Initialize flags and trap history.
  _nof_decompiles = 0;
  _nof_overflow_recompiles = 0;
  _nof_overflow_traps = 0;
  assert(sizeof(_trap_hist) % sizeof(HeapWord) == 0, "align");
  Copy::zero_to_words((HeapWord*) &_trap_hist,
                      sizeof(_trap_hist) / sizeof(HeapWord));

  // Go through the bytecodes and allocate and initialize the
  // corresponding data cells.
  int data_size = 0;
  int empty_bc_count = 0;  // number of bytecodes lacking data
  BytecodeStream stream(method);
  Bytecodes::Code c;
  while ((c = stream.next()) >= 0) {
    int size_in_bytes = initialize_data(&stream, data_size);
    data_size += size_in_bytes;
    if (size_in_bytes == 0)  empty_bc_count += 1;
  }
  _data_size = data_size;
  int object_size = in_bytes(data_offset()) + data_size;

  // Add some extra DataLayout cells (at least one) to track stray traps.
  int extra_data_count = compute_extra_data_count(data_size, empty_bc_count);
  int extra_size = extra_data_count * DataLayout::compute_size_in_bytes(0);

  // Add a cell to record information about modified arguments.
  // Set up _args_modified array after traps cells so that
  // the code for traps cells works.
  DataLayout *dp = data_layout_at(data_size + extra_size);

  int arg_size = method->size_of_parameters();
  dp->initialize(DataLayout::arg_info_data_tag, 0, arg_size+1);

  object_size += extra_size + DataLayout::compute_size_in_bytes(arg_size+1);

  // Set an initial hint. Don't use set_hint_di() because
  // first_di() may be out of bounds if data_size is 0.
  // In that situation, _hint_di is never used, but at
  // least well-defined.
  _hint_di = first_di();

  post_initialize(&stream);

  set_object_is_parsable(object_size);
}

// Get a measure of how much mileage the method has on it.
int methodDataOopDesc::mileage_of(methodOop method) {
  int mileage = 0;
  if (TieredCompilation) {
    mileage = MAX2(method->invocation_count(), method->backedge_count());
  } else {
    int iic = method->interpreter_invocation_count();
    if (mileage < iic)  mileage = iic;
    InvocationCounter* ic = method->invocation_counter();
    InvocationCounter* bc = method->backedge_counter();
    int icval = ic->count();
    if (ic->carry()) icval += CompileThreshold;
    if (mileage < icval)  mileage = icval;
    int bcval = bc->count();
    if (bc->carry()) bcval += CompileThreshold;
    if (mileage < bcval)  mileage = bcval;
  }
  return mileage;
}

bool methodDataOopDesc::is_mature() const {
  return CompilationPolicy::policy()->is_mature(_method);
}

// Translate a bci to its corresponding data index (di).
address methodDataOopDesc::bci_to_dp(int bci) {
  ResourceMark rm;
  ProfileData* data = data_before(bci);
  ProfileData* prev = NULL;
  for ( ; is_valid(data); data = next_data(data)) {
    if (data->bci() >= bci) {
      if (data->bci() == bci)  set_hint_di(dp_to_di(data->dp()));
      else if (prev != NULL)   set_hint_di(dp_to_di(prev->dp()));
      return data->dp();
    }
    prev = data;
  }
  return (address)limit_data_position();
}

// Translate a bci to its corresponding data, or NULL.
ProfileData* methodDataOopDesc::bci_to_data(int bci) {
  ProfileData* data = data_before(bci);
  for ( ; is_valid(data); data = next_data(data)) {
    if (data->bci() == bci) {
      set_hint_di(dp_to_di(data->dp()));
      return data;
    } else if (data->bci() > bci) {
      break;
    }
  }
  return bci_to_extra_data(bci, false);
}

// Translate a bci to its corresponding extra data, or NULL.
ProfileData* methodDataOopDesc::bci_to_extra_data(int bci, bool create_if_missing) {
  DataLayout* dp    = extra_data_base();
  DataLayout* end   = extra_data_limit();
  DataLayout* avail = NULL;
  for (; dp < end; dp = next_extra(dp)) {
    // No need for "OrderAccess::load_acquire" ops,
    // since the data structure is monotonic.
    if (dp->tag() == DataLayout::no_tag)  break;
    if (dp->tag() == DataLayout::arg_info_data_tag) {
      dp = end; // ArgInfoData is at the end of extra data section.
      break;
    }
    if (dp->bci() == bci) {
      assert(dp->tag() == DataLayout::bit_data_tag, "sane");
      return new BitData(dp);
    }
  }
  if (create_if_missing && dp < end) {
    // Allocate this one.  There is no mutual exclusion,
    // so two threads could allocate different BCIs to the
    // same data layout.  This means these extra data
    // records, like most other MDO contents, must not be
    // trusted too much.
    DataLayout temp;
    temp.initialize(DataLayout::bit_data_tag, bci, 0);
    dp->release_set_header(temp.header());
    assert(dp->tag() == DataLayout::bit_data_tag, "sane");
    //NO: assert(dp->bci() == bci, "no concurrent allocation");
    return new BitData(dp);
  }
  return NULL;
}

ArgInfoData *methodDataOopDesc::arg_info() {
  DataLayout* dp    = extra_data_base();
  DataLayout* end   = extra_data_limit();
  for (; dp < end; dp = next_extra(dp)) {
    if (dp->tag() == DataLayout::arg_info_data_tag)
      return new ArgInfoData(dp);
  }
  return NULL;
}

#ifndef PRODUCT
void methodDataOopDesc::print_data_on(outputStream* st) {
  ResourceMark rm;
  ProfileData* data = first_data();
  for ( ; is_valid(data); data = next_data(data)) {
    st->print("%d", dp_to_di(data->dp()));
    st->fill_to(6);
    data->print_data_on(st);
  }
  st->print_cr("--- Extra data:");
  DataLayout* dp    = extra_data_base();
  DataLayout* end   = extra_data_limit();
  for (; dp < end; dp = next_extra(dp)) {
    // No need for "OrderAccess::load_acquire" ops,
    // since the data structure is monotonic.
    if (dp->tag() == DataLayout::no_tag)  continue;
    if (dp->tag() == DataLayout::bit_data_tag) {
      data = new BitData(dp);
    } else {
      assert(dp->tag() == DataLayout::arg_info_data_tag, "must be BitData or ArgInfo");
      data = new ArgInfoData(dp);
      dp = end; // ArgInfoData is at the end of extra data section.
    }
    st->print("%d", dp_to_di(data->dp()));
    st->fill_to(6);
    data->print_data_on(st);
  }
}
#endif

void methodDataOopDesc::verify_data_on(outputStream* st) {
  NEEDS_CLEANUP;
  // not yet implemented.
}