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Datei: Sprache: C

/*
* Copyright (c) 2005, 2022, 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 "c1/c1_CFGPrinter.hpp"
#include "c1/c1_CodeStubs.hpp"
#include "c1/c1_Compilation.hpp"
#include "c1/c1_FrameMap.hpp"
#include "c1/c1_IR.hpp"
#include "c1/c1_LIRGenerator.hpp"
#include "c1/c1_LinearScan.hpp"
#include "c1/c1_ValueStack.hpp"
#include "code/vmreg.inline.hpp"
#include "runtime/timerTrace.hpp"
#include "utilities/bitMap.inline.hpp"

#ifndef PRODUCT

  static LinearScanStatistic _stat_before_alloc;
  static LinearScanStatistic _stat_after_asign;
  static LinearScanStatistic _stat_final;

  static LinearScanTimers _total_timer;

  // helper macro for short definition of timer
  #define TIME_LINEAR_SCAN(timer_name)  TraceTime _block_timer("", _total_timer.timer(LinearScanTimers::timer_name), TimeLinearScan || TimeEachLinearScan, Verbose);

#else
  #define TIME_LINEAR_SCAN(timer_name)
#endif

#ifdef ASSERT

  // helper macro for short definition of trace-output inside code
  #define TRACE_LINEAR_SCAN(level, code)       \
    if (TraceLinearScanLevel >= level) {       \
      code;                                    \
    }
#else
  #define TRACE_LINEAR_SCAN(level, code)
#endif

// Map BasicType to spill size in 32-bit words, matching VMReg's notion of words
#ifdef _LP64
static int type2spill_size[T_CONFLICT+1]={ -1, 0, 0, 0, 1, 1, 1, 2, 1, 1, 1, 2, 2, 2, 0, 2,  1, 2, 1, -1};
#else
static int type2spill_size[T_CONFLICT+1]={ -1, 0, 0, 0, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 0, 1, -1, 1, 1, -1};
#endif

// Implementation of LinearScan

LinearScan::LinearScan(IR* ir, LIRGenerator* gen, FrameMap* frame_map)
: _compilation(ir->compilation())
, _ir(ir)
, _gen(gen)
, _frame_map(frame_map)
, _cached_blocks(*ir->linear_scan_order())
, _num_virtual_regs(gen->max_virtual_register_number())
, _has_fpu_registers(false)
, _num_calls(-1)
, _max_spills(0)
, _unused_spill_slot(-1)
, _intervals(0)   // initialized later with correct length
, _new_intervals_from_allocation(NULL)
, _sorted_intervals(NULL)
, _needs_full_resort(false)
, _lir_ops(0)     // initialized later with correct length
, _block_of_op(0) // initialized later with correct length
, _has_info(0)
, _has_call(0)
, _interval_in_loop(0)  // initialized later with correct length
, _scope_value_cache(0) // initialized later with correct length
#ifdef IA32
, _fpu_stack_allocator(NULL)
#endif
{
  assert(this->ir() != NULL,          "check if valid");
  assert(this->compilation() != NULL, "check if valid");
  assert(this->gen() != NULL,         "check if valid");
  assert(this->frame_map() != NULL,   "check if valid");
}

// ********** functions for converting LIR-Operands to register numbers
//
// Emulate a flat register file comprising physical integer registers,
// physical floating-point registers and virtual registers, in that order.
// Virtual registers already have appropriate numbers, since V0 is
// the number of physical registers.
// Returns -1 for hi word if opr is a single word operand.
//
// Note: the inverse operation (calculating an operand for register numbers)
//       is done in calc_operand_for_interval()

int LinearScan::reg_num(LIR_Opr opr) {
  assert(opr->is_register(), "should not call this otherwise");

  if (opr->is_virtual_register()) {
    assert(opr->vreg_number() >= nof_regs, "found a virtual register with a fixed-register number");
    return opr->vreg_number();
  } else if (opr->is_single_cpu()) {
    return opr->cpu_regnr();
  } else if (opr->is_double_cpu()) {
    return opr->cpu_regnrLo();
#ifdef X86
  } else if (opr->is_single_xmm()) {
    return opr->fpu_regnr() + pd_first_xmm_reg;
  } else if (opr->is_double_xmm()) {
    return opr->fpu_regnrLo() + pd_first_xmm_reg;
#endif
  } else if (opr->is_single_fpu()) {
    return opr->fpu_regnr() + pd_first_fpu_reg;
  } else if (opr->is_double_fpu()) {
    return opr->fpu_regnrLo() + pd_first_fpu_reg;
  } else {
    ShouldNotReachHere();
    return -1;
  }
}

int LinearScan::reg_numHi(LIR_Opr opr) {
  assert(opr->is_register(), "should not call this otherwise");

  if (opr->is_virtual_register()) {
    return -1;
  } else if (opr->is_single_cpu()) {
    return -1;
  } else if (opr->is_double_cpu()) {
    return opr->cpu_regnrHi();
#ifdef X86
  } else if (opr->is_single_xmm()) {
    return -1;
  } else if (opr->is_double_xmm()) {
    return -1;
#endif
  } else if (opr->is_single_fpu()) {
    return -1;
  } else if (opr->is_double_fpu()) {
    return opr->fpu_regnrHi() + pd_first_fpu_reg;
  } else {
    ShouldNotReachHere();
    return -1;
  }
}

// ********** functions for classification of intervals

bool LinearScan::is_precolored_interval(const Interval* i) {
  return i->reg_num() < LinearScan::nof_regs;
}

bool LinearScan::is_virtual_interval(const Interval* i) {
  return i->reg_num() >= LIR_Opr::vreg_base;
}

bool LinearScan::is_precolored_cpu_interval(const Interval* i) {
  return i->reg_num() < LinearScan::nof_cpu_regs;
}

bool LinearScan::is_virtual_cpu_interval(const Interval* i) {
#if defined(__SOFTFP__) || defined(E500V2)
  return i->reg_num() >= LIR_Opr::vreg_base;
#else
  return i->reg_num() >= LIR_Opr::vreg_base && (i->type() != T_FLOAT && i->type() != T_DOUBLE);
#endif // __SOFTFP__ or E500V2
}

bool LinearScan::is_precolored_fpu_interval(const Interval* i) {
  return i->reg_num() >= LinearScan::nof_cpu_regs && i->reg_num() < LinearScan::nof_regs;
}

bool LinearScan::is_virtual_fpu_interval(const Interval* i) {
#if defined(__SOFTFP__) || defined(E500V2)
  return false;
#else
  return i->reg_num() >= LIR_Opr::vreg_base && (i->type() == T_FLOAT || i->type() == T_DOUBLE);
#endif // __SOFTFP__ or E500V2
}

bool LinearScan::is_in_fpu_register(const Interval* i) {
  // fixed intervals not needed for FPU stack allocation
  return i->reg_num() >= nof_regs && pd_first_fpu_reg <= i->assigned_reg() && i->assigned_reg() <= pd_last_fpu_reg;
}

bool LinearScan::is_oop_interval(const Interval* i) {
  // fixed intervals never contain oops
  return i->reg_num() >= nof_regs && i->type() == T_OBJECT;
}

// ********** General helper functions

// compute next unused stack index that can be used for spilling
int LinearScan::allocate_spill_slot(bool double_word) {
  int spill_slot;
  if (double_word) {
    if ((_max_spills & 1) == 1) {
      // alignment of double-word values
      // the hole because of the alignment is filled with the next single-word value
      assert(_unused_spill_slot == -1, "wasting a spill slot");
      _unused_spill_slot = _max_spills;
      _max_spills++;
    }
    spill_slot = _max_spills;
    _max_spills += 2;

  } else if (_unused_spill_slot != -1) {
    // re-use hole that was the result of a previous double-word alignment
    spill_slot = _unused_spill_slot;
    _unused_spill_slot = -1;

  } else {
    spill_slot = _max_spills;
    _max_spills++;
  }

  int result = spill_slot + LinearScan::nof_regs + frame_map()->argcount();

  // if too many slots used, bailout compilation.
  if (result > 2000) {
    bailout("too many stack slots used");
  }

  return result;
}

void LinearScan::assign_spill_slot(Interval* it) {
  // assign the canonical spill slot of the parent (if a part of the interval
  // is already spilled) or allocate a new spill slot
  if (it->canonical_spill_slot() >= 0) {
    it->assign_reg(it->canonical_spill_slot());
  } else {
    int spill = allocate_spill_slot(type2spill_size[it->type()] == 2);
    it->set_canonical_spill_slot(spill);
    it->assign_reg(spill);
  }
}

void LinearScan::propagate_spill_slots() {
  if (!frame_map()->finalize_frame(max_spills())) {
    bailout("frame too large");
  }
}

// create a new interval with a predefined reg_num
// (only used for parent intervals that are created during the building phase)
Interval* LinearScan::create_interval(int reg_num) {
  assert(_intervals.at(reg_num) == NULL, "overwriting existing interval");

  Interval* interval = new Interval(reg_num);
  _intervals.at_put(reg_num, interval);

  // assign register number for precolored intervals
  if (reg_num < LIR_Opr::vreg_base) {
    interval->assign_reg(reg_num);
  }
  return interval;
}

// assign a new reg_num to the interval and append it to the list of intervals
// (only used for child intervals that are created during register allocation)
void LinearScan::append_interval(Interval* it) {
  it->set_reg_num(_intervals.length());
  _intervals.append(it);
  IntervalList* new_intervals = _new_intervals_from_allocation;
  if (new_intervals == NULL) {
    new_intervals = _new_intervals_from_allocation = new IntervalList();
  }
  new_intervals->append(it);
}

// copy the vreg-flags if an interval is split
void LinearScan::copy_register_flags(Interval* from, Interval* to) {
  if (gen()->is_vreg_flag_set(from->reg_num(), LIRGenerator::byte_reg)) {
    gen()->set_vreg_flag(to->reg_num(), LIRGenerator::byte_reg);
  }
  if (gen()->is_vreg_flag_set(from->reg_num(), LIRGenerator::callee_saved)) {
    gen()->set_vreg_flag(to->reg_num(), LIRGenerator::callee_saved);
  }

  // Note: do not copy the must_start_in_memory flag because it is not necessary for child
  //       intervals (only the very beginning of the interval must be in memory)
}

// ********** spill move optimization
// eliminate moves from register to stack if stack slot is known to be correct

// called during building of intervals
void LinearScan::change_spill_definition_pos(Interval* interval, int def_pos) {
  assert(interval->is_split_parent(), "can only be called for split parents");

  switch (interval->spill_state()) {
    case noDefinitionFound:
      assert(interval->spill_definition_pos() == -1, "must no be set before");
      interval->set_spill_definition_pos(def_pos);
      interval->set_spill_state(oneDefinitionFound);
      break;

    case oneDefinitionFound:
      assert(def_pos <= interval->spill_definition_pos(), "positions are processed in reverse order when intervals are created");
      if (def_pos < interval->spill_definition_pos() - 2) {
        // second definition found, so no spill optimization possible for this interval
        interval->set_spill_state(noOptimization);
      } else {
        // two consecutive definitions (because of two-operand LIR form)
        assert(block_of_op_with_id(def_pos) == block_of_op_with_id(interval->spill_definition_pos()), "block must be equal");
      }
      break;

    case noOptimization:
      // nothing to do
      break;

    default:
      assert(false, "other states not allowed at this time");
  }
}

// called during register allocation
void LinearScan::change_spill_state(Interval* interval, int spill_pos) {
  switch (interval->spill_state()) {
    case oneDefinitionFound: {
      int def_loop_depth = block_of_op_with_id(interval->spill_definition_pos())->loop_depth();
      int spill_loop_depth = block_of_op_with_id(spill_pos)->loop_depth();

      if (def_loop_depth < spill_loop_depth) {
        // the loop depth of the spilling position is higher then the loop depth
        // at the definition of the interval -> move write to memory out of loop
        // by storing at definitin of the interval
        interval->set_spill_state(storeAtDefinition);
      } else {
        // the interval is currently spilled only once, so for now there is no
        // reason to store the interval at the definition
        interval->set_spill_state(oneMoveInserted);
      }
      break;
    }

    case oneMoveInserted: {
      // the interval is spilled more then once, so it is better to store it to
      // memory at the definition
      interval->set_spill_state(storeAtDefinition);
      break;
    }

    case storeAtDefinition:
    case startInMemory:
    case noOptimization:
    case noDefinitionFound:
      // nothing to do
      break;

    default:
      assert(false, "other states not allowed at this time");
  }
}

bool LinearScan::must_store_at_definition(const Interval* i) {
  return i->is_split_parent() && i->spill_state() == storeAtDefinition;
}

// called once before assignment of register numbers
void LinearScan::eliminate_spill_moves() {
  TIME_LINEAR_SCAN(timer_eliminate_spill_moves);
  TRACE_LINEAR_SCAN(3, tty->print_cr("***** Eliminating unnecessary spill moves"));

  // collect all intervals that must be stored after their definion.
  // the list is sorted by Interval::spill_definition_pos
  Interval* interval;
  Interval* temp_list;
  create_unhandled_lists(&interval, &temp_list, must_store_at_definition, NULL);

#ifdef ASSERT
  Interval* prev = NULL;
  Interval* temp = interval;
  while (temp != Interval::end()) {
    assert(temp->spill_definition_pos() > 0, "invalid spill definition pos");
    if (prev != NULL) {
      assert(temp->from() >= prev->from(), "intervals not sorted");
      assert(temp->spill_definition_pos() >= prev->spill_definition_pos(), "when intervals are sorted by from, then they must also be sorted by spill_definition_pos");
    }

    assert(temp->canonical_spill_slot() >= LinearScan::nof_regs, "interval has no spill slot assigned");
    assert(temp->spill_definition_pos() >= temp->from(), "invalid order");
    assert(temp->spill_definition_pos() <= temp->from() + 2, "only intervals defined once at their start-pos can be optimized");

    TRACE_LINEAR_SCAN(4, tty->print_cr("interval %d (from %d to %d) must be stored at %d", temp->reg_num(), temp->from(), temp->to(), temp->spill_definition_pos()));

    temp = temp->next();
  }
#endif

  LIR_InsertionBuffer insertion_buffer;
  int num_blocks = block_count();
  for (int i = 0; i < num_blocks; i++) {
    BlockBegin* block = block_at(i);
    LIR_OpList* instructions = block->lir()->instructions_list();
    int         num_inst = instructions->length();
    bool        has_new = false;

    // iterate all instructions of the block. skip the first because it is always a label
    for (int j = 1; j < num_inst; j++) {
      LIR_Op* op = instructions->at(j);
      int op_id = op->id();

      if (op_id == -1) {
        // remove move from register to stack if the stack slot is guaranteed to be correct.
        // only moves that have been inserted by LinearScan can be removed.
        assert(op->code() == lir_move, "only moves can have a op_id of -1");
        assert(op->as_Op1() != NULL, "move must be LIR_Op1");
        assert(op->as_Op1()->result_opr()->is_virtual(), "LinearScan inserts only moves to virtual registers");

        LIR_Op1* op1 = (LIR_Op1*)op;
        Interval* interval = interval_at(op1->result_opr()->vreg_number());

        if (interval->assigned_reg() >= LinearScan::nof_regs && interval->always_in_memory()) {
          // move target is a stack slot that is always correct, so eliminate instruction
          TRACE_LINEAR_SCAN(4, tty->print_cr("eliminating move from interval %d to %d", op1->in_opr()->vreg_number(), op1->result_opr()->vreg_number()));
          instructions->at_put(j, NULL); // NULL-instructions are deleted by assign_reg_num
        }

      } else {
        // insert move from register to stack just after the beginning of the interval
        assert(interval == Interval::end() || interval->spill_definition_pos() >= op_id, "invalid order");
        assert(interval == Interval::end() || (interval->is_split_parent() && interval->spill_state() == storeAtDefinition), "invalid interval");

        while (interval != Interval::end() && interval->spill_definition_pos() == op_id) {
          if (!has_new) {
            // prepare insertion buffer (appended when all instructions of the block are processed)
            insertion_buffer.init(block->lir());
            has_new = true;
          }

          LIR_Opr from_opr = operand_for_interval(interval);
          LIR_Opr to_opr = canonical_spill_opr(interval);
          assert(from_opr->is_fixed_cpu() || from_opr->is_fixed_fpu(), "from operand must be a register");
          assert(to_opr->is_stack(), "to operand must be a stack slot");

          insertion_buffer.move(j, from_opr, to_opr);
          TRACE_LINEAR_SCAN(4, tty->print_cr("inserting move after definition of interval %d to stack slot %d at op_id %d", interval->reg_num(), interval->canonical_spill_slot() - LinearScan::nof_regs, op_id));

          interval = interval->next();
        }
      }
    } // end of instruction iteration

    if (has_new) {
      block->lir()->append(&insertion_buffer);
    }
  } // end of block iteration

  assert(interval == Interval::end(), "missed an interval");
}

// ********** Phase 1: number all instructions in all blocks
// Compute depth-first and linear scan block orders, and number LIR_Op nodes for linear scan.

void LinearScan::number_instructions() {
  {
    // dummy-timer to measure the cost of the timer itself
    // (this time is then subtracted from all other timers to get the real value)
    TIME_LINEAR_SCAN(timer_do_nothing);
  }
  TIME_LINEAR_SCAN(timer_number_instructions);

  // Assign IDs to LIR nodes and build a mapping, lir_ops, from ID to LIR_Op node.
  int num_blocks = block_count();
  int num_instructions = 0;
  int i;
  for (i = 0; i < num_blocks; i++) {
    num_instructions += block_at(i)->lir()->instructions_list()->length();
  }

  // initialize with correct length
  _lir_ops = LIR_OpArray(num_instructions, num_instructions, NULL);
  _block_of_op = BlockBeginArray(num_instructions, num_instructions, NULL);

  int op_id = 0;
  int idx = 0;

  for (i = 0; i < num_blocks; i++) {
    BlockBegin* block = block_at(i);
    block->set_first_lir_instruction_id(op_id);
    LIR_OpList* instructions = block->lir()->instructions_list();

    int num_inst = instructions->length();
    for (int j = 0; j < num_inst; j++) {
      LIR_Op* op = instructions->at(j);
      op->set_id(op_id);

      _lir_ops.at_put(idx, op);
      _block_of_op.at_put(idx, block);
      assert(lir_op_with_id(op_id) == op, "must match");

      idx++;
      op_id += 2; // numbering of lir_ops by two
    }
    block->set_last_lir_instruction_id(op_id - 2);
  }
  assert(idx == num_instructions, "must match");
  assert(idx * 2 == op_id, "must match");

  _has_call.initialize(num_instructions);
  _has_info.initialize(num_instructions);
}

// ********** Phase 2: compute local live sets separately for each block
// (sets live_gen and live_kill for each block)

void LinearScan::set_live_gen_kill(Value value, LIR_Op* op, BitMap& live_gen, BitMap& live_kill) {
  LIR_Opr opr = value->operand();
  Constant* con = value->as_Constant();

  // check some asumptions about debug information
  assert(!value->type()->is_illegal(), "if this local is used by the interpreter it shouldn't be of indeterminate type");
  assert(con == NULL || opr->is_virtual() || opr->is_constant() || opr->is_illegal(), "assumption: Constant instructions have only constant operands");
  assert(con != NULL || opr->is_virtual(), "assumption: non-Constant instructions have only virtual operands");

  if ((con == NULL || con->is_pinned()) && opr->is_register()) {
    assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
    int reg = opr->vreg_number();
    if (!live_kill.at(reg)) {
      live_gen.set_bit(reg);
      TRACE_LINEAR_SCAN(4, tty->print_cr(" Setting live_gen for value %c%d, LIR op_id %d, register number %d", value->type()->tchar(), value->id(), op->id(), reg));
    }
  }
}

void LinearScan::compute_local_live_sets() {
  TIME_LINEAR_SCAN(timer_compute_local_live_sets);

  int  num_blocks = block_count();
  int  live_size = live_set_size();
  bool local_has_fpu_registers = false;
  int  local_num_calls = 0;
  LIR_OpVisitState visitor;

  BitMap2D local_interval_in_loop = BitMap2D(_num_virtual_regs, num_loops());

  // iterate all blocks
  for (int i = 0; i < num_blocks; i++) {
    BlockBegin* block = block_at(i);

    ResourceBitMap live_gen(live_size);
    ResourceBitMap live_kill(live_size);

    if (block->is_set(BlockBegin::exception_entry_flag)) {
      // Phi functions at the begin of an exception handler are
      // implicitly defined (= killed) at the beginning of the block.
      for_each_phi_fun(block, phi,
        if (!phi->is_illegal()) { live_kill.set_bit(phi->operand()->vreg_number()); }
      );
    }

    LIR_OpList* instructions = block->lir()->instructions_list();
    int num_inst = instructions->length();

    // iterate all instructions of the block. skip the first because it is always a label
    assert(visitor.no_operands(instructions->at(0)), "first operation must always be a label");
    for (int j = 1; j < num_inst; j++) {
      LIR_Op* op = instructions->at(j);

      // visit operation to collect all operands
      visitor.visit(op);

      if (visitor.has_call()) {
        _has_call.set_bit(op->id() >> 1);
        local_num_calls++;
      }
      if (visitor.info_count() > 0) {
        _has_info.set_bit(op->id() >> 1);
      }

      // iterate input operands of instruction
      int k, n, reg;
      n = visitor.opr_count(LIR_OpVisitState::inputMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::inputMode, k);
        assert(opr->is_register(), "visitor should only return register operands");

        if (opr->is_virtual_register()) {
          assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
          reg = opr->vreg_number();
          if (!live_kill.at(reg)) {
            live_gen.set_bit(reg);
            TRACE_LINEAR_SCAN(4, tty->print_cr(" Setting live_gen for register %d at instruction %d", reg, op->id()));
          }
          if (block->loop_index() >= 0) {
            local_interval_in_loop.set_bit(reg, block->loop_index());
          }
          local_has_fpu_registers = local_has_fpu_registers || opr->is_virtual_fpu();
        }

#ifdef ASSERT
        // fixed intervals are never live at block boundaries, so
        // they need not be processed in live sets.
        // this is checked by these assertions to be sure about it.
        // the entry block may have incoming values in registers, which is ok.
        if (!opr->is_virtual_register() && block != ir()->start()) {
          reg = reg_num(opr);
          if (is_processed_reg_num(reg)) {
            assert(live_kill.at(reg), "using fixed register that is not defined in this block");
          }
          reg = reg_numHi(opr);
          if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
            assert(live_kill.at(reg), "using fixed register that is not defined in this block");
          }
        }
#endif
      }

      // Add uses of live locals from interpreter's point of view for proper debug information generation
      n = visitor.info_count();
      for (k = 0; k < n; k++) {
        CodeEmitInfo* info = visitor.info_at(k);
        ValueStack* stack = info->stack();
        for_each_state_value(stack, value,
          set_live_gen_kill(value, op, live_gen, live_kill);
          local_has_fpu_registers = local_has_fpu_registers || value->type()->is_float_kind();
        );
      }

      // iterate temp operands of instruction
      n = visitor.opr_count(LIR_OpVisitState::tempMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::tempMode, k);
        assert(opr->is_register(), "visitor should only return register operands");

        if (opr->is_virtual_register()) {
          assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
          reg = opr->vreg_number();
          live_kill.set_bit(reg);
          if (block->loop_index() >= 0) {
            local_interval_in_loop.set_bit(reg, block->loop_index());
          }
          local_has_fpu_registers = local_has_fpu_registers || opr->is_virtual_fpu();
        }

#ifdef ASSERT
        // fixed intervals are never live at block boundaries, so
        // they need not be processed in live sets
        // process them only in debug mode so that this can be checked
        if (!opr->is_virtual_register()) {
          reg = reg_num(opr);
          if (is_processed_reg_num(reg)) {
            live_kill.set_bit(reg_num(opr));
          }
          reg = reg_numHi(opr);
          if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
            live_kill.set_bit(reg);
          }
        }
#endif
      }

      // iterate output operands of instruction
      n = visitor.opr_count(LIR_OpVisitState::outputMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::outputMode, k);
        assert(opr->is_register(), "visitor should only return register operands");

        if (opr->is_virtual_register()) {
          assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
          reg = opr->vreg_number();
          live_kill.set_bit(reg);
          if (block->loop_index() >= 0) {
            local_interval_in_loop.set_bit(reg, block->loop_index());
          }
          local_has_fpu_registers = local_has_fpu_registers || opr->is_virtual_fpu();
        }

#ifdef ASSERT
        // fixed intervals are never live at block boundaries, so
        // they need not be processed in live sets
        // process them only in debug mode so that this can be checked
        if (!opr->is_virtual_register()) {
          reg = reg_num(opr);
          if (is_processed_reg_num(reg)) {
            live_kill.set_bit(reg_num(opr));
          }
          reg = reg_numHi(opr);
          if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
            live_kill.set_bit(reg);
          }
        }
#endif
      }
    } // end of instruction iteration

    block->set_live_gen (live_gen);
    block->set_live_kill(live_kill);
    block->set_live_in  (ResourceBitMap(live_size));
    block->set_live_out (ResourceBitMap(live_size));

    TRACE_LINEAR_SCAN(4, tty->print("live_gen B%d ", block->block_id()); print_bitmap(block->live_gen()));
    TRACE_LINEAR_SCAN(4, tty->print("live_kill B%d ", block->block_id()); print_bitmap(block->live_kill()));
  } // end of block iteration

  // propagate local calculated information into LinearScan object
  _has_fpu_registers = local_has_fpu_registers;
  compilation()->set_has_fpu_code(local_has_fpu_registers);

  _num_calls = local_num_calls;
  _interval_in_loop = local_interval_in_loop;
}

// ********** Phase 3: perform a backward dataflow analysis to compute global live sets
// (sets live_in and live_out for each block)

void LinearScan::compute_global_live_sets() {
  TIME_LINEAR_SCAN(timer_compute_global_live_sets);

  int  num_blocks = block_count();
  bool change_occurred;
  bool change_occurred_in_block;
  int  iteration_count = 0;
  ResourceBitMap live_out(live_set_size()); // scratch set for calculations

  // Perform a backward dataflow analysis to compute live_out and live_in for each block.
  // The loop is executed until a fixpoint is reached (no changes in an iteration)
  // Exception handlers must be processed because not all live values are
  // present in the state array, e.g. because of global value numbering
  do {
    change_occurred = false;

    // iterate all blocks in reverse order
    for (int i = num_blocks - 1; i >= 0; i--) {
      BlockBegin* block = block_at(i);

      change_occurred_in_block = false;

      // live_out(block) is the union of live_in(sux), for successors sux of block
      int n = block->number_of_sux();
      int e = block->number_of_exception_handlers();
      if (n + e > 0) {
        // block has successors
        if (n > 0) {
          live_out.set_from(block->sux_at(0)->live_in());
          for (int j = 1; j < n; j++) {
            live_out.set_union(block->sux_at(j)->live_in());
          }
        } else {
          live_out.clear();
        }
        for (int j = 0; j < e; j++) {
          live_out.set_union(block->exception_handler_at(j)->live_in());
        }

        if (!block->live_out().is_same(live_out)) {
          // A change occurred.  Swap the old and new live out sets to avoid copying.
          ResourceBitMap temp = block->live_out();
          block->set_live_out(live_out);
          live_out = temp;

          change_occurred = true;
          change_occurred_in_block = true;
        }
      }

      if (iteration_count == 0 || change_occurred_in_block) {
        // live_in(block) is the union of live_gen(block) with (live_out(block) & !live_kill(block))
        // note: live_in has to be computed only in first iteration or if live_out has changed!
        ResourceBitMap live_in = block->live_in();
        live_in.set_from(block->live_out());
        live_in.set_difference(block->live_kill());
        live_in.set_union(block->live_gen());
      }

#ifdef ASSERT
      if (TraceLinearScanLevel >= 4) {
        char c = ' ';
        if (iteration_count == 0 || change_occurred_in_block) {
          c = '*';
        }
        tty->print("(%d) live_in%c B%d ", iteration_count, c, block->block_id()); print_bitmap(block->live_in());
        tty->print("(%d) live_out%c B%d ", iteration_count, c, block->block_id()); print_bitmap(block->live_out());
      }
#endif
    }
    iteration_count++;

    if (change_occurred && iteration_count > 50) {
      BAILOUT("too many iterations in compute_global_live_sets");
    }
  } while (change_occurred);

#ifdef ASSERT
  // check that fixed intervals are not live at block boundaries
  // (live set must be empty at fixed intervals)
  for (int i = 0; i < num_blocks; i++) {
    BlockBegin* block = block_at(i);
    for (int j = 0; j < LIR_Opr::vreg_base; j++) {
      assert(block->live_in().at(j)  == false, "live_in set of fixed register must be empty");
      assert(block->live_out().at(j) == false, "live_out set of fixed register must be empty");
      assert(block->live_gen().at(j) == false, "live_gen set of fixed register must be empty");
    }
  }
#endif

  // check that the live_in set of the first block is empty
  ResourceBitMap live_in_args(ir()->start()->live_in().size());
  if (!ir()->start()->live_in().is_same(live_in_args)) {
#ifdef ASSERT
    tty->print_cr("Error: live_in set of first block must be empty (when this fails, virtual registers are used before they are defined)");
    tty->print_cr("affected registers:");
    print_bitmap(ir()->start()->live_in());

    // print some additional information to simplify debugging
    for (unsigned int i = 0; i < ir()->start()->live_in().size(); i++) {
      if (ir()->start()->live_in().at(i)) {
        Instruction* instr = gen()->instruction_for_vreg(i);
        tty->print_cr("* vreg %d (HIR instruction %c%d)", i, instr == NULL ? ' ' : instr->type()->tchar(), instr == NULL ? 0 : instr->id());

        for (int j = 0; j < num_blocks; j++) {
          BlockBegin* block = block_at(j);
          if (block->live_gen().at(i)) {
            tty->print_cr(" used in block B%d", block->block_id());
          }
          if (block->live_kill().at(i)) {
            tty->print_cr(" defined in block B%d", block->block_id());
          }
        }
      }
    }

#endif
    // when this fails, virtual registers are used before they are defined.
    assert(false, "live_in set of first block must be empty");
    // bailout of if this occurs in product mode.
    bailout("live_in set of first block not empty");
  }
}

// ********** Phase 4: build intervals
// (fills the list _intervals)

void LinearScan::add_use(Value value, int from, int to, IntervalUseKind use_kind) {
  assert(!value->type()->is_illegal(), "if this value is used by the interpreter it shouldn't be of indeterminate type");
  LIR_Opr opr = value->operand();
  Constant* con = value->as_Constant();

  if ((con == NULL || con->is_pinned()) && opr->is_register()) {
    assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
    add_use(opr, from, to, use_kind);
  }
}

void LinearScan::add_def(LIR_Opr opr, int def_pos, IntervalUseKind use_kind) {
  TRACE_LINEAR_SCAN(2, tty->print(" def "); opr->print(tty); tty->print_cr(" def_pos %d (%d)", def_pos, use_kind));
  assert(opr->is_register(), "should not be called otherwise");

  if (opr->is_virtual_register()) {
    assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
    add_def(opr->vreg_number(), def_pos, use_kind, opr->type_register());

  } else {
    int reg = reg_num(opr);
    if (is_processed_reg_num(reg)) {
      add_def(reg, def_pos, use_kind, opr->type_register());
    }
    reg = reg_numHi(opr);
    if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
      add_def(reg, def_pos, use_kind, opr->type_register());
    }
  }
}

void LinearScan::add_use(LIR_Opr opr, int from, int to, IntervalUseKind use_kind) {
  TRACE_LINEAR_SCAN(2, tty->print(" use "); opr->print(tty); tty->print_cr(" from %d to %d (%d)", from, to, use_kind));
  assert(opr->is_register(), "should not be called otherwise");

  if (opr->is_virtual_register()) {
    assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
    add_use(opr->vreg_number(), from, to, use_kind, opr->type_register());

  } else {
    int reg = reg_num(opr);
    if (is_processed_reg_num(reg)) {
      add_use(reg, from, to, use_kind, opr->type_register());
    }
    reg = reg_numHi(opr);
    if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
      add_use(reg, from, to, use_kind, opr->type_register());
    }
  }
}

void LinearScan::add_temp(LIR_Opr opr, int temp_pos, IntervalUseKind use_kind) {
  TRACE_LINEAR_SCAN(2, tty->print(" temp "); opr->print(tty); tty->print_cr(" temp_pos %d (%d)", temp_pos, use_kind));
  assert(opr->is_register(), "should not be called otherwise");

  if (opr->is_virtual_register()) {
    assert(reg_num(opr) == opr->vreg_number() && !is_valid_reg_num(reg_numHi(opr)), "invalid optimization below");
    add_temp(opr->vreg_number(), temp_pos, use_kind, opr->type_register());

  } else {
    int reg = reg_num(opr);
    if (is_processed_reg_num(reg)) {
      add_temp(reg, temp_pos, use_kind, opr->type_register());
    }
    reg = reg_numHi(opr);
    if (is_valid_reg_num(reg) && is_processed_reg_num(reg)) {
      add_temp(reg, temp_pos, use_kind, opr->type_register());
    }
  }
}

void LinearScan::add_def(int reg_num, int def_pos, IntervalUseKind use_kind, BasicType type) {
  Interval* interval = interval_at(reg_num);
  if (interval != NULL) {
    assert(interval->reg_num() == reg_num, "wrong interval");

    if (type != T_ILLEGAL) {
      interval->set_type(type);
    }

    Range* r = interval->first();
    if (r->from() <= def_pos) {
      // Update the starting point (when a range is first created for a use, its
      // start is the beginning of the current block until a def is encountered.)
      r->set_from(def_pos);
      interval->add_use_pos(def_pos, use_kind);

    } else {
      // Dead value - make vacuous interval
      // also add use_kind for dead intervals
      interval->add_range(def_pos, def_pos + 1);
      interval->add_use_pos(def_pos, use_kind);
      TRACE_LINEAR_SCAN(2, tty->print_cr("Warning: def of reg %d at %d occurs without use", reg_num, def_pos));
    }

  } else {
    // Dead value - make vacuous interval
    // also add use_kind for dead intervals
    interval = create_interval(reg_num);
    if (type != T_ILLEGAL) {
      interval->set_type(type);
    }

    interval->add_range(def_pos, def_pos + 1);
    interval->add_use_pos(def_pos, use_kind);
    TRACE_LINEAR_SCAN(2, tty->print_cr("Warning: dead value %d at %d in live intervals", reg_num, def_pos));
  }

  change_spill_definition_pos(interval, def_pos);
  if (use_kind == noUse && interval->spill_state() <= startInMemory) {
        // detection of method-parameters and roundfp-results
        // TODO: move this directly to position where use-kind is computed
    interval->set_spill_state(startInMemory);
  }
}

void LinearScan::add_use(int reg_num, int from, int to, IntervalUseKind use_kind, BasicType type) {
  Interval* interval = interval_at(reg_num);
  if (interval == NULL) {
    interval = create_interval(reg_num);
  }
  assert(interval->reg_num() == reg_num, "wrong interval");

  if (type != T_ILLEGAL) {
    interval->set_type(type);
  }

  interval->add_range(from, to);
  interval->add_use_pos(to, use_kind);
}

void LinearScan::add_temp(int reg_num, int temp_pos, IntervalUseKind use_kind, BasicType type) {
  Interval* interval = interval_at(reg_num);
  if (interval == NULL) {
    interval = create_interval(reg_num);
  }
  assert(interval->reg_num() == reg_num, "wrong interval");

  if (type != T_ILLEGAL) {
    interval->set_type(type);
  }

  interval->add_range(temp_pos, temp_pos + 1);
  interval->add_use_pos(temp_pos, use_kind);
}

// the results of this functions are used for optimizing spilling and reloading
// if the functions return shouldHaveRegister and the interval is spilled,
// it is not reloaded to a register.
IntervalUseKind LinearScan::use_kind_of_output_operand(LIR_Op* op, LIR_Opr opr) {
  if (op->code() == lir_move) {
    assert(op->as_Op1() != NULL, "lir_move must be LIR_Op1");
    LIR_Op1* move = (LIR_Op1*)op;
    LIR_Opr res = move->result_opr();
    bool result_in_memory = res->is_virtual() && gen()->is_vreg_flag_set(res->vreg_number(), LIRGenerator::must_start_in_memory);

    if (result_in_memory) {
      // Begin of an interval with must_start_in_memory set.
      // This interval will always get a stack slot first, so return noUse.
      return noUse;

    } else if (move->in_opr()->is_stack()) {
      // method argument (condition must be equal to handle_method_arguments)
      return noUse;

    } else if (move->in_opr()->is_register() && move->result_opr()->is_register()) {
      // Move from register to register
      if (block_of_op_with_id(op->id())->is_set(BlockBegin::osr_entry_flag)) {
        // special handling of phi-function moves inside osr-entry blocks
        // input operand must have a register instead of output operand (leads to better register allocation)
        return shouldHaveRegister;
      }
    }
  }

  if (opr->is_virtual() &&
      gen()->is_vreg_flag_set(opr->vreg_number(), LIRGenerator::must_start_in_memory)) {
    // result is a stack-slot, so prevent immediate reloading
    return noUse;
  }

  // all other operands require a register
  return mustHaveRegister;
}

IntervalUseKind LinearScan::use_kind_of_input_operand(LIR_Op* op, LIR_Opr opr) {
  if (op->code() == lir_move) {
    assert(op->as_Op1() != NULL, "lir_move must be LIR_Op1");
    LIR_Op1* move = (LIR_Op1*)op;
    LIR_Opr res = move->result_opr();
    bool result_in_memory = res->is_virtual() && gen()->is_vreg_flag_set(res->vreg_number(), LIRGenerator::must_start_in_memory);

    if (result_in_memory) {
      // Move to an interval with must_start_in_memory set.
      // To avoid moves from stack to stack (not allowed) force the input operand to a register
      return mustHaveRegister;

    } else if (move->in_opr()->is_register() && move->result_opr()->is_register()) {
      // Move from register to register
      if (block_of_op_with_id(op->id())->is_set(BlockBegin::osr_entry_flag)) {
        // special handling of phi-function moves inside osr-entry blocks
        // input operand must have a register instead of output operand (leads to better register allocation)
        return mustHaveRegister;
      }

      // The input operand is not forced to a register (moves from stack to register are allowed),
      // but it is faster if the input operand is in a register
      return shouldHaveRegister;
    }
  }

#if defined(X86) || defined(S390)
  if (op->code() == lir_cmove) {
    // conditional moves can handle stack operands
    assert(op->result_opr()->is_register(), "result must always be in a register");
    return shouldHaveRegister;
  }

  // optimizations for second input operand of arithmehtic operations on Intel
  // this operand is allowed to be on the stack in some cases
  BasicType opr_type = opr->type_register();
  if (opr_type == T_FLOAT || opr_type == T_DOUBLE) {
    if (IA32_ONLY( (UseSSE == 1 && opr_type == T_FLOAT) || UseSSE >= 2 ) NOT_IA32( true )) {
      // SSE float instruction (T_DOUBLE only supported with SSE2)
      switch (op->code()) {
        case lir_cmp:
        case lir_add:
        case lir_sub:
        case lir_mul:
        case lir_div:
        {
          assert(op->as_Op2() != NULL, "must be LIR_Op2");
          LIR_Op2* op2 = (LIR_Op2*)op;
          if (op2->in_opr1() != op2->in_opr2() && op2->in_opr2() == opr) {
            assert((op2->result_opr()->is_register() || op->code() == lir_cmp) && op2->in_opr1()->is_register(), "cannot mark second operand as stack if others are not in register");
            return shouldHaveRegister;
          }
        }
        default:
          break;
      }
    } else {
      // FPU stack float instruction
      switch (op->code()) {
        case lir_add:
        case lir_sub:
        case lir_mul:
        case lir_div:
        {
          assert(op->as_Op2() != NULL, "must be LIR_Op2");
          LIR_Op2* op2 = (LIR_Op2*)op;
          if (op2->in_opr1() != op2->in_opr2() && op2->in_opr2() == opr) {
            assert((op2->result_opr()->is_register() || op->code() == lir_cmp) && op2->in_opr1()->is_register(), "cannot mark second operand as stack if others are not in register");
            return shouldHaveRegister;
          }
        }
        default:
          break;
      }
    }
    // We want to sometimes use logical operations on pointers, in particular in GC barriers.
    // Since 64bit logical operations do not current support operands on stack, we have to make sure
    // T_OBJECT doesn't get spilled along with T_LONG.
  } else if (opr_type != T_LONG LP64_ONLY(&& opr_type != T_OBJECT)) {
    // integer instruction (note: long operands must always be in register)
    switch (op->code()) {
      case lir_cmp:
      case lir_add:
      case lir_sub:
      case lir_logic_and:
      case lir_logic_or:
      case lir_logic_xor:
      {
        assert(op->as_Op2() != NULL, "must be LIR_Op2");
        LIR_Op2* op2 = (LIR_Op2*)op;
        if (op2->in_opr1() != op2->in_opr2() && op2->in_opr2() == opr) {
          assert((op2->result_opr()->is_register() || op->code() == lir_cmp) && op2->in_opr1()->is_register(), "cannot mark second operand as stack if others are not in register");
          return shouldHaveRegister;
        }
      }
      default:
        break;
    }
  }
#endif // X86 || S390

  // all other operands require a register
  return mustHaveRegister;
}

void LinearScan::handle_method_arguments(LIR_Op* op) {
  // special handling for method arguments (moves from stack to virtual register):
  // the interval gets no register assigned, but the stack slot.
  // it is split before the first use by the register allocator.

  if (op->code() == lir_move) {
    assert(op->as_Op1() != NULL, "must be LIR_Op1");
    LIR_Op1* move = (LIR_Op1*)op;

    if (move->in_opr()->is_stack()) {
#ifdef ASSERT
      int arg_size = compilation()->method()->arg_size();
      LIR_Opr o = move->in_opr();
      if (o->is_single_stack()) {
        assert(o->single_stack_ix() >= 0 && o->single_stack_ix() < arg_size, "out of range");
      } else if (o->is_double_stack()) {
        assert(o->double_stack_ix() >= 0 && o->double_stack_ix() < arg_size, "out of range");
      } else {
        ShouldNotReachHere();
      }

      assert(move->id() > 0, "invalid id");
      assert(block_of_op_with_id(move->id())->number_of_preds() == 0, "move from stack must be in first block");
      assert(move->result_opr()->is_virtual(), "result of move must be a virtual register");

      TRACE_LINEAR_SCAN(4, tty->print_cr("found move from stack slot %d to vreg %d", o->is_single_stack() ? o->single_stack_ix() : o->double_stack_ix(), reg_num(move->result_opr())));
#endif

      Interval* interval = interval_at(reg_num(move->result_opr()));

      int stack_slot = LinearScan::nof_regs + (move->in_opr()->is_single_stack() ? move->in_opr()->single_stack_ix() : move->in_opr()->double_stack_ix());
      interval->set_canonical_spill_slot(stack_slot);
      interval->assign_reg(stack_slot);
    }
  }
}

void LinearScan::handle_doubleword_moves(LIR_Op* op) {
  // special handling for doubleword move from memory to register:
  // in this case the registers of the input address and the result
  // registers must not overlap -> add a temp range for the input registers
  if (op->code() == lir_move) {
    assert(op->as_Op1() != NULL, "must be LIR_Op1");
    LIR_Op1* move = (LIR_Op1*)op;

    if (move->result_opr()->is_double_cpu() && move->in_opr()->is_pointer()) {
      LIR_Address* address = move->in_opr()->as_address_ptr();
      if (address != NULL) {
        if (address->base()->is_valid()) {
          add_temp(address->base(), op->id(), noUse);
        }
        if (address->index()->is_valid()) {
          add_temp(address->index(), op->id(), noUse);
        }
      }
    }
  }
}

void LinearScan::add_register_hints(LIR_Op* op) {
  switch (op->code()) {
    case lir_move:      // fall through
    case lir_convert: {
      assert(op->as_Op1() != NULL, "lir_move, lir_convert must be LIR_Op1");
      LIR_Op1* move = (LIR_Op1*)op;

      LIR_Opr move_from = move->in_opr();
      LIR_Opr move_to = move->result_opr();

      if (move_to->is_register() && move_from->is_register()) {
        Interval* from = interval_at(reg_num(move_from));
        Interval* to = interval_at(reg_num(move_to));
        if (from != NULL && to != NULL) {
          to->set_register_hint(from);
          TRACE_LINEAR_SCAN(4, tty->print_cr("operation at op_id %d: added hint from interval %d to %d", move->id(), from->reg_num(), to->reg_num()));
        }
      }
      break;
    }
    case lir_cmove: {
      assert(op->as_Op4() != NULL, "lir_cmove must be LIR_Op4");
      LIR_Op4* cmove = (LIR_Op4*)op;

      LIR_Opr move_from = cmove->in_opr1();
      LIR_Opr move_to   = cmove->result_opr();

      if (move_to->is_register() && move_from->is_register()) {
        Interval* from = interval_at(reg_num(move_from));
        Interval* to = interval_at(reg_num(move_to));
        if (from != NULL && to != NULL) {
          to->set_register_hint(from);
          TRACE_LINEAR_SCAN(4, tty->print_cr("operation at op_id %d: added hint from interval %d to %d", cmove->id(), from->reg_num(), to->reg_num()));
        }
      }
      break;
    }
    default:
      break;
  }
}

void LinearScan::build_intervals() {
  TIME_LINEAR_SCAN(timer_build_intervals);

  // initialize interval list with expected number of intervals
  // (32 is added to have some space for split children without having to resize the list)
  _intervals = IntervalList(num_virtual_regs() + 32);
  // initialize all slots that are used by build_intervals
  _intervals.at_put_grow(num_virtual_regs() - 1, NULL, NULL);

  // create a list with all caller-save registers (cpu, fpu, xmm)
  // when an instruction is a call, a temp range is created for all these registers
  int num_caller_save_registers = 0;
  int caller_save_registers[LinearScan::nof_regs];

  int i;
  for (i = 0; i < FrameMap::nof_caller_save_cpu_regs(); i++) {
    LIR_Opr opr = FrameMap::caller_save_cpu_reg_at(i);
    assert(opr->is_valid() && opr->is_register(), "FrameMap should not return invalid operands");
    assert(reg_numHi(opr) == -1, "missing addition of range for hi-register");
    caller_save_registers[num_caller_save_registers++] = reg_num(opr);
  }

  // temp ranges for fpu registers are only created when the method has
  // virtual fpu operands. Otherwise no allocation for fpu registers is
  // performed and so the temp ranges would be useless
  if (has_fpu_registers()) {
#ifdef X86
    if (UseSSE < 2) {
#endif // X86
      for (i = 0; i < FrameMap::nof_caller_save_fpu_regs; i++) {
        LIR_Opr opr = FrameMap::caller_save_fpu_reg_at(i);
        assert(opr->is_valid() && opr->is_register(), "FrameMap should not return invalid operands");
        assert(reg_numHi(opr) == -1, "missing addition of range for hi-register");
        caller_save_registers[num_caller_save_registers++] = reg_num(opr);
      }
#ifdef X86
    }
#endif // X86

#ifdef X86
    if (UseSSE > 0) {
      int num_caller_save_xmm_regs = FrameMap::get_num_caller_save_xmms();
      for (i = 0; i < num_caller_save_xmm_regs; i ++) {
        LIR_Opr opr = FrameMap::caller_save_xmm_reg_at(i);
        assert(opr->is_valid() && opr->is_register(), "FrameMap should not return invalid operands");
        assert(reg_numHi(opr) == -1, "missing addition of range for hi-register");
        caller_save_registers[num_caller_save_registers++] = reg_num(opr);
      }
    }
#endif // X86
  }
  assert(num_caller_save_registers <= LinearScan::nof_regs, "out of bounds");

  LIR_OpVisitState visitor;

  // iterate all blocks in reverse order
  for (i = block_count() - 1; i >= 0; i--) {
    BlockBegin* block = block_at(i);
    LIR_OpList* instructions = block->lir()->instructions_list();
    int         block_from =   block->first_lir_instruction_id();
    int         block_to =     block->last_lir_instruction_id();

    assert(block_from == instructions->at(0)->id(), "must be");
    assert(block_to   == instructions->at(instructions->length() - 1)->id(), "must be");

    // Update intervals for registers live at the end of this block;
    ResourceBitMap live = block->live_out();
    int size = (int)live.size();
    for (int number = (int)live.get_next_one_offset(0, size); number < size; number = (int)live.get_next_one_offset(number + 1, size)) {
      assert(live.at(number), "should not stop here otherwise");
      assert(number >= LIR_Opr::vreg_base, "fixed intervals must not be live on block bounds");
      TRACE_LINEAR_SCAN(2, tty->print_cr("live in %d to %d", number, block_to + 2));

      add_use(number, block_from, block_to + 2, noUse, T_ILLEGAL);

      // add special use positions for loop-end blocks when the
      // interval is used anywhere inside this loop.  It's possible
      // that the block was part of a non-natural loop, so it might
      // have an invalid loop index.
      if (block->is_set(BlockBegin::linear_scan_loop_end_flag) &&
          block->loop_index() != -1 &&
          is_interval_in_loop(number, block->loop_index())) {
        interval_at(number)->add_use_pos(block_to + 1, loopEndMarker);
      }
    }

    // iterate all instructions of the block in reverse order.
    // skip the first instruction because it is always a label
    // definitions of intervals are processed before uses
    assert(visitor.no_operands(instructions->at(0)), "first operation must always be a label");
    for (int j = instructions->length() - 1; j >= 1; j--) {
      LIR_Op* op = instructions->at(j);
      int op_id = op->id();

      // visit operation to collect all operands
      visitor.visit(op);

      // add a temp range for each register if operation destroys caller-save registers
      if (visitor.has_call()) {
        for (int k = 0; k < num_caller_save_registers; k++) {
          add_temp(caller_save_registers[k], op_id, noUse, T_ILLEGAL);
        }
        TRACE_LINEAR_SCAN(4, tty->print_cr("operation destroys all caller-save registers"));
      }

      // Add any platform dependent temps
      pd_add_temps(op);

      // visit definitions (output and temp operands)
      int k, n;
      n = visitor.opr_count(LIR_OpVisitState::outputMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::outputMode, k);
        assert(opr->is_register(), "visitor should only return register operands");
        add_def(opr, op_id, use_kind_of_output_operand(op, opr));
      }

      n = visitor.opr_count(LIR_OpVisitState::tempMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::tempMode, k);
        assert(opr->is_register(), "visitor should only return register operands");
        add_temp(opr, op_id, mustHaveRegister);
      }

      // visit uses (input operands)
      n = visitor.opr_count(LIR_OpVisitState::inputMode);
      for (k = 0; k < n; k++) {
        LIR_Opr opr = visitor.opr_at(LIR_OpVisitState::inputMode, k);
        assert(opr->is_register(), "visitor should only return register operands");
        add_use(opr, block_from, op_id, use_kind_of_input_operand(op, opr));
      }

      // Add uses of live locals from interpreter's point of view for proper
      // debug information generation
      // Treat these operands as temp values (if the life range is extended
      // to a call site, the value would be in a register at the call otherwise)
      n = visitor.info_count();
      for (k = 0; k < n; k++) {
        CodeEmitInfo* info = visitor.info_at(k);
        ValueStack* stack = info->stack();
        for_each_state_value(stack, value,
          add_use(value, block_from, op_id + 1, noUse);
        );
      }

      // special steps for some instructions (especially moves)
      handle_method_arguments(op);
      handle_doubleword_moves(op);
      add_register_hints(op);

    } // end of instruction iteration
  } // end of block iteration

  // add the range [0, 1[ to all fixed intervals
  // -> the register allocator need not handle unhandled fixed intervals
  for (int n = 0; n < LinearScan::nof_regs; n++) {
    Interval* interval = interval_at(n);
    if (interval != NULL) {
      interval->add_range(0, 1);
    }
  }
}

// ********** Phase 5: actual register allocation

int LinearScan::interval_cmp(Interval** a, Interval** b) {
  if (*a != NULL) {
    if (*b != NULL) {
      return (*a)->from() - (*b)->from();
    } else {
      return -1;
    }
  } else {
    if (*b != NULL) {
      return 1;
    } else {
      return 0;
    }
  }
}

#ifndef PRODUCT
int interval_cmp(Interval* const& l, Interval* const& r) {
  return l->from() - r->from();
}

bool find_interval(Interval* interval, IntervalArray* intervals) {
  bool found;
  int idx = intervals->find_sorted<Interval*, interval_cmp>(interval, found);

  if (!found) {
    return false;
  }

  int from = interval->from();

  // The index we've found using binary search is pointing to an interval
  // that is defined in the same place as the interval we were looking for.
  // So now we have to look around that index and find exact interval.
  for (int i = idx; i >= 0; i--) {
    if (intervals->at(i) == interval) {
      return true;
    }
    if (intervals->at(i)->from() != from) {
      break;
    }
  }

  for (int i = idx + 1; i < intervals->length(); i++) {
    if (intervals->at(i) == interval) {
      return true;
    }
    if (intervals->at(i)->from() != from) {
      break;
    }
  }

  return false;
}

bool LinearScan::is_sorted(IntervalArray* intervals) {
  int from = -1;
  int null_count = 0;

  for (int i = 0; i < intervals->length(); i++) {
    Interval* it = intervals->at(i);
    if (it != NULL) {
      assert(from <= it->from(), "Intervals are unordered");
      from = it->from();
    } else {
      null_count++;
    }
  }

  assert(null_count == 0, "Sorted intervals should not contain nulls");

  null_count = 0;

  for (int i = 0; i < interval_count(); i++) {
    Interval* interval = interval_at(i);
    if (interval != NULL) {
      assert(find_interval(interval, intervals), "Lists do not contain same intervals");
    } else {
      null_count++;
    }
  }

  assert(interval_count() - null_count == intervals->length(),
      "Sorted list should contain the same amount of non-NULL intervals as unsorted list");

  return true;
}
#endif

void LinearScan::add_to_list(Interval** first, Interval** prev, Interval* interval) {
  if (*prev != NULL) {
    (*prev)->set_next(interval);
  } else {
    *first = interval;
  }
  *prev = interval;
}

void LinearScan::create_unhandled_lists(Interval** list1, Interval** list2, bool (is_list1)(const Interval* i), bool (is_list2)(const Interval* i)) {
  assert(is_sorted(_sorted_intervals), "interval list is not sorted");

  *list1 = *list2 = Interval::end();

  Interval* list1_prev = NULL;
  Interval* list2_prev = NULL;
  Interval* v;

  const int n = _sorted_intervals->length();
  for (int i = 0; i < n; i++) {
    v = _sorted_intervals->at(i);
    if (v == NULL) continue;

    if (is_list1(v)) {
      add_to_list(list1, &list1_prev, v);
    } else if (is_list2 == NULL || is_list2(v)) {
      add_to_list(list2, &list2_prev, v);
    }
  }

  if (list1_prev != NULL) list1_prev->set_next(Interval::end());
  if (list2_prev != NULL) list2_prev->set_next(Interval::end());

  assert(list1_prev == NULL || list1_prev->next() == Interval::end(), "linear list ends not with sentinel");
  assert(list2_prev == NULL || list2_prev->next() == Interval::end(), "linear list ends not with sentinel");
}

void LinearScan::sort_intervals_before_allocation() {
  TIME_LINEAR_SCAN(timer_sort_intervals_before);

  if (_needs_full_resort) {
    // There is no known reason why this should occur but just in case...
    assert(false, "should never occur");
    // Re-sort existing interval list because an Interval::from() has changed
    _sorted_intervals->sort(interval_cmp);
    _needs_full_resort = false;
  }

  IntervalList* unsorted_list = &_intervals;
  int unsorted_len = unsorted_list->length();
  int sorted_len = 0;
  int unsorted_idx;
  int sorted_idx = 0;
  int sorted_from_max = -1;

  // calc number of items for sorted list (sorted list must not contain NULL values)
  for (unsorted_idx = 0; unsorted_idx < unsorted_len; unsorted_idx++) {
    if (unsorted_list->at(unsorted_idx) != NULL) {
      sorted_len++;
    }
  }
  IntervalArray* sorted_list = new IntervalArray(sorted_len, sorted_len, NULL);

  // special sorting algorithm: the original interval-list is almost sorted,
  // only some intervals are swapped. So this is much faster than a complete QuickSort
  for (unsorted_idx = 0; unsorted_idx < unsorted_len; unsorted_idx++) {
    Interval* cur_interval = unsorted_list->at(unsorted_idx);

    if (cur_interval != NULL) {
      int cur_from = cur_interval->from();

      if (sorted_from_max <= cur_from) {
        sorted_list->at_put(sorted_idx++, cur_interval);
        sorted_from_max = cur_interval->from();
      } else {
        // the assumption that the intervals are already sorted failed,
        // so this interval must be sorted in manually
        int j;
        for (j = sorted_idx - 1; j >= 0 && cur_from < sorted_list->at(j)->from(); j--) {
          sorted_list->at_put(j + 1, sorted_list->at(j));
        }
        sorted_list->at_put(j + 1, cur_interval);
        sorted_idx++;
      }
    }
  }
  _sorted_intervals = sorted_list;
  assert(is_sorted(_sorted_intervals), "intervals unsorted");
}

void LinearScan::sort_intervals_after_allocation() {
  TIME_LINEAR_SCAN(timer_sort_intervals_after);

  if (_needs_full_resort) {
    // Re-sort existing interval list because an Interval::from() has changed
    _sorted_intervals->sort(interval_cmp);
    _needs_full_resort = false;
  }

  IntervalArray* old_list = _sorted_intervals;
  IntervalList* new_list = _new_intervals_from_allocation;
  int old_len = old_list->length();
  int new_len = new_list == NULL ? 0 : new_list->length();

  if (new_len == 0) {
    // no intervals have been added during allocation, so sorted list is already up to date
    assert(is_sorted(_sorted_intervals), "intervals unsorted");
    return;
  }

  // conventional sort-algorithm for new intervals
  new_list->sort(interval_cmp);

  // merge old and new list (both already sorted) into one combined list
  int combined_list_len = old_len + new_len;
  IntervalArray* combined_list = new IntervalArray(combined_list_len, combined_list_len, NULL);
  int old_idx = 0;
  int new_idx = 0;

  while (old_idx + new_idx < old_len + new_len) {
    if (new_idx >= new_len || (old_idx < old_len && old_list->at(old_idx)->from() <= new_list->at(new_idx)->from())) {
      combined_list->at_put(old_idx + new_idx, old_list->at(old_idx));
      old_idx++;
    } else {
      combined_list->at_put(old_idx + new_idx, new_list->at(new_idx));
      new_idx++;
    }
  }

  _sorted_intervals = combined_list;
  assert(is_sorted(_sorted_intervals), "intervals unsorted");
}

void LinearScan::allocate_registers() {
  TIME_LINEAR_SCAN(timer_allocate_registers);

  Interval* precolored_cpu_intervals, *not_precolored_cpu_intervals;
  Interval* precolored_fpu_intervals, *not_precolored_fpu_intervals;

  // collect cpu intervals
  create_unhandled_lists(&precolored_cpu_intervals, ¬_precolored_cpu_intervals,
                         is_precolored_cpu_interval, is_virtual_cpu_interval);

  // collect fpu intervals
  create_unhandled_lists(&precolored_fpu_intervals, ¬_precolored_fpu_intervals,
                         is_precolored_fpu_interval, is_virtual_fpu_interval);
  // this fpu interval collection cannot be moved down below with the allocation section as
  // the cpu_lsw.walk() changes interval positions.

  if (!has_fpu_registers()) {
#ifdef ASSERT
    assert(not_precolored_fpu_intervals == Interval::end(), "missed an uncolored fpu interval");
#else
    if (not_precolored_fpu_intervals != Interval::end()) {
      BAILOUT("missed an uncolored fpu interval");
    }
#endif
  }

  // allocate cpu registers
  LinearScanWalker cpu_lsw(this, precolored_cpu_intervals, not_precolored_cpu_intervals);
  cpu_lsw.walk();
  cpu_lsw.finish_allocation();

  if (has_fpu_registers()) {
    // allocate fpu registers
    LinearScanWalker fpu_lsw(this, precolored_fpu_intervals, not_precolored_fpu_intervals);
    fpu_lsw.walk();
    fpu_lsw.finish_allocation();
  }
}

// ********** Phase 6: resolve data flow
// (insert moves at edges between blocks if intervals have been split)

// wrapper for Interval::split_child_at_op_id that performs a bailout in product mode
// instead of returning NULL
Interval* LinearScan::split_child_at_op_id(Interval* interval, int op_id, LIR_OpVisitState::OprMode mode) {
  Interval* result = interval->split_child_at_op_id(op_id, mode);
  if (result != NULL) {
    return result;
  }

  assert(false, "must find an interval, but do a clean bailout in product mode");
  result = new Interval(LIR_Opr::vreg_base);
  result->assign_reg(0);
  result->set_type(T_INT);
  BAILOUT_("LinearScan: interval is NULL", result);
}

Interval* LinearScan::interval_at_block_begin(BlockBegin* block, int reg_num) {
  assert(LinearScan::nof_regs <= reg_num && reg_num < num_virtual_regs(), "register number out of bounds");
  assert(interval_at(reg_num) != NULL, "no interval found");

  return split_child_at_op_id(interval_at(reg_num), block->first_lir_instruction_id(), LIR_OpVisitState::outputMode);
}

Interval* LinearScan::interval_at_block_end(BlockBegin* block, int reg_num) {
  assert(LinearScan::nof_regs <= reg_num && reg_num < num_virtual_regs(), "register number out of bounds");
  assert(interval_at(reg_num) != NULL, "no interval found");

  return split_child_at_op_id(interval_at(reg_num), block->last_lir_instruction_id() + 1, LIR_OpVisitState::outputMode);
}

Interval* LinearScan::interval_at_op_id(int reg_num, int op_id) {
  assert(LinearScan::nof_regs <= reg_num && reg_num < num_virtual_regs(), "register number out of bounds");
  assert(interval_at(reg_num) != NULL, "no interval found");

  return split_child_at_op_id(interval_at(reg_num), op_id, LIR_OpVisitState::inputMode);
}

void LinearScan::resolve_collect_mappings(BlockBegin* from_block, BlockBegin* to_block, MoveResolver &move_resolver) {
  DEBUG_ONLY(move_resolver.check_empty());

  const int size = live_set_size();
  const ResourceBitMap live_at_edge = to_block->live_in();

  // visit all registers where the live_at_edge bit is set
  for (int r = (int)live_at_edge.get_next_one_offset(0, size); r < size; r = (int)live_at_edge.get_next_one_offset(r + 1, size)) {
    assert(r < num_virtual_regs(), "live information set for not existing interval");
    assert(from_block->live_out().at(r) && to_block->live_in().at(r), "interval not live at this edge");

    Interval* from_interval = interval_at_block_end(from_block, r);
    Interval* to_interval = interval_at_block_begin(to_block, r);

    if (from_interval != to_interval && (from_interval->assigned_reg() != to_interval->assigned_reg() || from_interval->assigned_regHi() != to_interval->assigned_regHi())) {
      // need to insert move instruction
      move_resolver.add_mapping(from_interval, to_interval);
    }
  }
}

void LinearScan::resolve_find_insert_pos(BlockBegin* from_block, BlockBegin* to_block, MoveResolver &move_resolver) {
--> --------------------

--> maximum size reached

--> --------------------

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