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products/sources/formale Sprachen/Java/Openjdk/src/hotspot/share/c1/ (Sun/Oracle ^©) Datei vom 13.11.2022 mit Größe 124 kB

Quelle c1_LIRGenerator.cpp 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_Compilation.hpp"
#include "c1/c1_Defs.hpp"
#include "c1/c1_FrameMap.hpp"
#include "c1/c1_Instruction.hpp"
#include "c1/c1_LIRAssembler.hpp"
#include "c1/c1_LIRGenerator.hpp"
#include "c1/c1_ValueStack.hpp"
#include "ci/ciArrayKlass.hpp"
#include "ci/ciInstance.hpp"
#include "ci/ciObjArray.hpp"
#include "ci/ciUtilities.hpp"
#include "compiler/compilerDefinitions.inline.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/c1/barrierSetC1.hpp"
#include "oops/klass.inline.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/vm_version.hpp"
#include "utilities/bitMap.inline.hpp"
#include "utilities/macros.hpp"
#include "utilities/powerOfTwo.hpp"

#ifdef ASSERT
#define __ gen()->lir(__FILE__, __LINE__)->
#else
#define __ gen()->lir()->
#endif

#ifndef PATCHED_ADDR
#define PATCHED_ADDR  (max_jint)
#endif

void PhiResolverState::reset() {
  _virtual_operands.clear();
  _other_operands.clear();
  _vreg_table.clear();
}

//--------------------------------------------------------------
// PhiResolver

// Resolves cycles:
//
//  r1 := r2  becomes  temp := r1
//  r2 := r1           r1 := r2
//                     r2 := temp
// and orders moves:
//
//  r2 := r3  becomes  r1 := r2
//  r1 := r2           r2 := r3

PhiResolver::PhiResolver(LIRGenerator* gen)
: _gen(gen)
, _state(gen->resolver_state())
, _temp(LIR_OprFact::illegalOpr)
{
  // reinitialize the shared state arrays
  _state.reset();
}

void PhiResolver::emit_move(LIR_Opr src, LIR_Opr dest) {
  assert(src->is_valid(), "");
  assert(dest->is_valid(), "");
  __ move(src, dest);
}

void PhiResolver::move_temp_to(LIR_Opr dest) {
  assert(_temp->is_valid(), "");
  emit_move(_temp, dest);
  NOT_PRODUCT(_temp = LIR_OprFact::illegalOpr);
}

void PhiResolver::move_to_temp(LIR_Opr src) {
  assert(_temp->is_illegal(), "");
  _temp = _gen->new_register(src->type());
  emit_move(src, _temp);
}

// Traverse assignment graph in depth first order and generate moves in post order
// ie. two assignments: b := c, a := b start with node c:
// Call graph: move(NULL, c) -> move(c, b) -> move(b, a)
// Generates moves in this order: move b to a and move c to b
// ie. cycle a := b, b := a start with node a
// Call graph: move(NULL, a) -> move(a, b) -> move(b, a)
// Generates moves in this order: move b to temp, move a to b, move temp to a
void PhiResolver::move(ResolveNode* src, ResolveNode* dest) {
  if (!dest->visited()) {
    dest->set_visited();
    for (int i = dest->no_of_destinations()-1; i >= 0; i --) {
      move(dest, dest->destination_at(i));
    }
  } else if (!dest->start_node()) {
    // cylce in graph detected
    assert(_loop == NULL, "only one loop valid!");
    _loop = dest;
    move_to_temp(src->operand());
    return;
  } // else dest is a start node

  if (!dest->assigned()) {
    if (_loop == dest) {
      move_temp_to(dest->operand());
      dest->set_assigned();
    } else if (src != NULL) {
      emit_move(src->operand(), dest->operand());
      dest->set_assigned();
    }
  }
}

PhiResolver::~PhiResolver() {
  int i;
  // resolve any cycles in moves from and to virtual registers
  for (i = virtual_operands().length() - 1; i >= 0; i --) {
    ResolveNode* node = virtual_operands().at(i);
    if (!node->visited()) {
      _loop = NULL;
      move(NULL, node);
      node->set_start_node();
      assert(_temp->is_illegal(), "move_temp_to() call missing");
    }
  }

  // generate move for move from non virtual register to abitrary destination
  for (i = other_operands().length() - 1; i >= 0; i --) {
    ResolveNode* node = other_operands().at(i);
    for (int j = node->no_of_destinations() - 1; j >= 0; j --) {
      emit_move(node->operand(), node->destination_at(j)->operand());
    }
  }
}

ResolveNode* PhiResolver::create_node(LIR_Opr opr, bool source) {
  ResolveNode* node;
  if (opr->is_virtual()) {
    int vreg_num = opr->vreg_number();
    node = vreg_table().at_grow(vreg_num, NULL);
    assert(node == NULL || node->operand() == opr, "");
    if (node == NULL) {
      node = new ResolveNode(opr);
      vreg_table().at_put(vreg_num, node);
    }
    // Make sure that all virtual operands show up in the list when
    // they are used as the source of a move.
    if (source && !virtual_operands().contains(node)) {
      virtual_operands().append(node);
    }
  } else {
    assert(source, "");
    node = new ResolveNode(opr);
    other_operands().append(node);
  }
  return node;
}

void PhiResolver::move(LIR_Opr src, LIR_Opr dest) {
  assert(dest->is_virtual(), "");
  // tty->print("move "); src->print(); tty->print(" to "); dest->print(); tty->cr();
  assert(src->is_valid(), "");
  assert(dest->is_valid(), "");
  ResolveNode* source = source_node(src);
  source->append(destination_node(dest));
}

//--------------------------------------------------------------
// LIRItem

void LIRItem::set_result(LIR_Opr opr) {
  assert(value()->operand()->is_illegal() || value()->operand()->is_constant(), "operand should never change");
  value()->set_operand(opr);

  if (opr->is_virtual()) {
    _gen->_instruction_for_operand.at_put_grow(opr->vreg_number(), value(), NULL);
  }

  _result = opr;
}

void LIRItem::load_item() {
  if (result()->is_illegal()) {
    // update the items result
    _result = value()->operand();
  }
  if (!result()->is_register()) {
    LIR_Opr reg = _gen->new_register(value()->type());
    __ move(result(), reg);
    if (result()->is_constant()) {
      _result = reg;
    } else {
      set_result(reg);
    }
  }
}

void LIRItem::load_for_store(BasicType type) {
  if (_gen->can_store_as_constant(value(), type)) {
    _result = value()->operand();
    if (!_result->is_constant()) {
      _result = LIR_OprFact::value_type(value()->type());
    }
  } else if (type == T_BYTE || type == T_BOOLEAN) {
    load_byte_item();
  } else {
    load_item();
  }
}

void LIRItem::load_item_force(LIR_Opr reg) {
  LIR_Opr r = result();
  if (r != reg) {
#if !defined(ARM) && !defined(E500V2)
    if (r->type() != reg->type()) {
      // moves between different types need an intervening spill slot
      r = _gen->force_to_spill(r, reg->type());
    }
#endif
    __ move(r, reg);
    _result = reg;
  }
}

ciObject* LIRItem::get_jobject_constant() const {
  ObjectType* oc = type()->as_ObjectType();
  if (oc) {
    return oc->constant_value();
  }
  return NULL;
}

jint LIRItem::get_jint_constant() const {
  assert(is_constant() && value() != NULL, "");
  assert(type()->as_IntConstant() != NULL, "type check");
  return type()->as_IntConstant()->value();
}

jint LIRItem::get_address_constant() const {
  assert(is_constant() && value() != NULL, "");
  assert(type()->as_AddressConstant() != NULL, "type check");
  return type()->as_AddressConstant()->value();
}

jfloat LIRItem::get_jfloat_constant() const {
  assert(is_constant() && value() != NULL, "");
  assert(type()->as_FloatConstant() != NULL, "type check");
  return type()->as_FloatConstant()->value();
}

jdouble LIRItem::get_jdouble_constant() const {
  assert(is_constant() && value() != NULL, "");
  assert(type()->as_DoubleConstant() != NULL, "type check");
  return type()->as_DoubleConstant()->value();
}

jlong LIRItem::get_jlong_constant() const {
  assert(is_constant() && value() != NULL, "");
  assert(type()->as_LongConstant() != NULL, "type check");
  return type()->as_LongConstant()->value();
}

//--------------------------------------------------------------

void LIRGenerator::block_do_prolog(BlockBegin* block) {
#ifndef PRODUCT
  if (PrintIRWithLIR) {
    block->print();
  }
#endif

  // set up the list of LIR instructions
  assert(block->lir() == NULL, "LIR list already computed for this block");
  _lir = new LIR_List(compilation(), block);
  block->set_lir(_lir);

  __ branch_destination(block->label());

  if (LIRTraceExecution &&
      Compilation::current()->hir()->start()->block_id() != block->block_id() &&
      !block->is_set(BlockBegin::exception_entry_flag)) {
    assert(block->lir()->instructions_list()->length() == 1, "should come right after br_dst");
    trace_block_entry(block);
  }
}

void LIRGenerator::block_do_epilog(BlockBegin* block) {
#ifndef PRODUCT
  if (PrintIRWithLIR) {
    tty->cr();
  }
#endif

  // LIR_Opr for unpinned constants shouldn't be referenced by other
  // blocks so clear them out after processing the block.
  for (int i = 0; i < _unpinned_constants.length(); i++) {
    _unpinned_constants.at(i)->clear_operand();
  }
  _unpinned_constants.trunc_to(0);

  // clear our any registers for other local constants
  _constants.trunc_to(0);
  _reg_for_constants.trunc_to(0);
}

void LIRGenerator::block_do(BlockBegin* block) {
  CHECK_BAILOUT();

  block_do_prolog(block);
  set_block(block);

  for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
    if (instr->is_pinned()) do_root(instr);
  }

  set_block(NULL);
  block_do_epilog(block);
}

//-------------------------LIRGenerator-----------------------------

// This is where the tree-walk starts; instr must be root;
void LIRGenerator::do_root(Value instr) {
  CHECK_BAILOUT();

  InstructionMark im(compilation(), instr);

  assert(instr->is_pinned(), "use only with roots");
  assert(instr->subst() == instr, "shouldn't have missed substitution");

  instr->visit(this);

  assert(!instr->has_uses() || instr->operand()->is_valid() ||
         instr->as_Constant() != NULL || bailed_out(), "invalid item set");
}

// This is called for each node in tree; the walk stops if a root is reached
void LIRGenerator::walk(Value instr) {
  InstructionMark im(compilation(), instr);
  //stop walk when encounter a root
  if ((instr->is_pinned() && instr->as_Phi() == NULL) || instr->operand()->is_valid()) {
    assert(instr->operand() != LIR_OprFact::illegalOpr || instr->as_Constant() != NULL, "this root has not yet been visited");
  } else {
    assert(instr->subst() == instr, "shouldn't have missed substitution");
    instr->visit(this);
    // assert(instr->use_count() > 0 || instr->as_Phi() != NULL, "leaf instruction must have a use");
  }
}

CodeEmitInfo* LIRGenerator::state_for(Instruction* x, ValueStack* state, bool ignore_xhandler) {
  assert(state != NULL, "state must be defined");

#ifndef PRODUCT
  state->verify();
#endif

  ValueStack* s = state;
  for_each_state(s) {
    if (s->kind() == ValueStack::EmptyExceptionState) {
      assert(s->stack_size() == 0 && s->locals_size() == 0 && (s->locks_size() == 0 || s->locks_size() == 1), "state must be empty");
      continue;
    }

    int index;
    Value value;
    for_each_stack_value(s, index, value) {
      assert(value->subst() == value, "missed substitution");
      if (!value->is_pinned() && value->as_Constant() == NULL && value->as_Local() == NULL) {
        walk(value);
        assert(value->operand()->is_valid(), "must be evaluated now");
      }
    }

    int bci = s->bci();
    IRScope* scope = s->scope();
    ciMethod* method = scope->method();

    MethodLivenessResult liveness = method->liveness_at_bci(bci);
    if (bci == SynchronizationEntryBCI) {
      if (x->as_ExceptionObject() || x->as_Throw()) {
        // all locals are dead on exit from the synthetic unlocker
        liveness.clear();
      } else {
        assert(x->as_MonitorEnter() || x->as_ProfileInvoke(), "only other cases are MonitorEnter and ProfileInvoke");
      }
    }
    if (!liveness.is_valid()) {
      // Degenerate or breakpointed method.
      bailout("Degenerate or breakpointed method");
    } else {
      assert((int)liveness.size() == s->locals_size(), "error in use of liveness");
      for_each_local_value(s, index, value) {
        assert(value->subst() == value, "missed substitution");
        if (liveness.at(index) && !value->type()->is_illegal()) {
          if (!value->is_pinned() && value->as_Constant() == NULL && value->as_Local() == NULL) {
            walk(value);
            assert(value->operand()->is_valid(), "must be evaluated now");
          }
        } else {
          // NULL out this local so that linear scan can assume that all non-NULL values are live.
          s->invalidate_local(index);
        }
      }
    }
  }

  return new CodeEmitInfo(state, ignore_xhandler ? NULL : x->exception_handlers(), x->check_flag(Instruction::DeoptimizeOnException));
}

CodeEmitInfo* LIRGenerator::state_for(Instruction* x) {
  return state_for(x, x->exception_state());
}

void LIRGenerator::klass2reg_with_patching(LIR_Opr r, ciMetadata* obj, CodeEmitInfo* info, bool need_resolve) {
  /* C2 relies on constant pool entries being resolved (ciTypeFlow), so if tiered compilation
   * is active and the class hasn't yet been resolved we need to emit a patch that resolves
   * the class. */
  if ((!CompilerConfig::is_c1_only_no_jvmci() && need_resolve) || !obj->is_loaded() || PatchALot) {
    assert(info != NULL, "info must be set if class is not loaded");
    __ klass2reg_patch(NULL, r, info);
  } else {
    // no patching needed
    __ metadata2reg(obj->constant_encoding(), r);
  }
}

void LIRGenerator::array_range_check(LIR_Opr array, LIR_Opr index,
                                    CodeEmitInfo* null_check_info, CodeEmitInfo* range_check_info) {
  CodeStub* stub = new RangeCheckStub(range_check_info, index, array);
  if (index->is_constant()) {
    cmp_mem_int(lir_cond_belowEqual, array, arrayOopDesc::length_offset_in_bytes(),
                index->as_jint(), null_check_info);
    __ branch(lir_cond_belowEqual, stub); // forward branch
  } else {
    cmp_reg_mem(lir_cond_aboveEqual, index, array,
                arrayOopDesc::length_offset_in_bytes(), T_INT, null_check_info);
    __ branch(lir_cond_aboveEqual, stub); // forward branch
  }
}

void LIRGenerator::arithmetic_op(Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, LIR_Opr tmp_op, CodeEmitInfo* info) {
  LIR_Opr result_op = result;
  LIR_Opr left_op   = left;
  LIR_Opr right_op  = right;

  if (TwoOperandLIRForm && left_op != result_op) {
    assert(right_op != result_op, "malformed");
    __ move(left_op, result_op);
    left_op = result_op;
  }

  switch(code) {
    case Bytecodes::_dadd:
    case Bytecodes::_fadd:
    case Bytecodes::_ladd:
    case Bytecodes::_iadd:  __ add(left_op, right_op, result_op); break;
    case Bytecodes::_fmul:
    case Bytecodes::_lmul:  __ mul(left_op, right_op, result_op); break;

    case Bytecodes::_dmul:  __ mul(left_op, right_op, result_op, tmp_op); break;

    case Bytecodes::_imul:
      {
        bool did_strength_reduce = false;

        if (right->is_constant()) {
          jint c = right->as_jint();
          if (c > 0 && is_power_of_2(c)) {
            // do not need tmp here
            __ shift_left(left_op, exact_log2(c), result_op);
            did_strength_reduce = true;
          } else {
            did_strength_reduce = strength_reduce_multiply(left_op, c, result_op, tmp_op);
          }
        }
        // we couldn't strength reduce so just emit the multiply
        if (!did_strength_reduce) {
          __ mul(left_op, right_op, result_op);
        }
      }
      break;

    case Bytecodes::_dsub:
    case Bytecodes::_fsub:
    case Bytecodes::_lsub:
    case Bytecodes::_isub: __ sub(left_op, right_op, result_op); break;

    case Bytecodes::_fdiv: __ div (left_op, right_op, result_op); break;
    // ldiv and lrem are implemented with a direct runtime call

    case Bytecodes::_ddiv: __ div(left_op, right_op, result_op, tmp_op); break;

    case Bytecodes::_drem:
    case Bytecodes::_frem: __ rem (left_op, right_op, result_op); break;

    default: ShouldNotReachHere();
  }
}

void LIRGenerator::arithmetic_op_int(Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, LIR_Opr tmp) {
  arithmetic_op(code, result, left, right, tmp);
}

void LIRGenerator::arithmetic_op_long(Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, CodeEmitInfo* info) {
  arithmetic_op(code, result, left, right, LIR_OprFact::illegalOpr, info);
}

void LIRGenerator::arithmetic_op_fpu(Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, LIR_Opr tmp) {
  arithmetic_op(code, result, left, right, tmp);
}

void LIRGenerator::shift_op(Bytecodes::Code code, LIR_Opr result_op, LIR_Opr value, LIR_Opr count, LIR_Opr tmp) {

  if (TwoOperandLIRForm && value != result_op
      // Only 32bit right shifts require two operand form on S390.
      S390_ONLY(&& (code == Bytecodes::_ishr || code == Bytecodes::_iushr))) {
    assert(count != result_op, "malformed");
    __ move(value, result_op);
    value = result_op;
  }

  assert(count->is_constant() || count->is_register(), "must be");
  switch(code) {
  case Bytecodes::_ishl:
  case Bytecodes::_lshl: __ shift_left(value, count, result_op, tmp); break;
  case Bytecodes::_ishr:
  case Bytecodes::_lshr: __ shift_right(value, count, result_op, tmp); break;
  case Bytecodes::_iushr:
  case Bytecodes::_lushr: __ unsigned_shift_right(value, count, result_op, tmp); break;
  default: ShouldNotReachHere();
  }
}

void LIRGenerator::logic_op (Bytecodes::Code code, LIR_Opr result_op, LIR_Opr left_op, LIR_Opr right_op) {
  if (TwoOperandLIRForm && left_op != result_op) {
    assert(right_op != result_op, "malformed");
    __ move(left_op, result_op);
    left_op = result_op;
  }

  switch(code) {
    case Bytecodes::_iand:
    case Bytecodes::_land:  __ logical_and(left_op, right_op, result_op); break;

    case Bytecodes::_ior:
    case Bytecodes::_lor:   __ logical_or(left_op, right_op, result_op);  break;

    case Bytecodes::_ixor:
    case Bytecodes::_lxor:  __ logical_xor(left_op, right_op, result_op); break;

    default: ShouldNotReachHere();
  }
}

void LIRGenerator::monitor_enter(LIR_Opr object, LIR_Opr lock, LIR_Opr hdr, LIR_Opr scratch, int monitor_no, CodeEmitInfo* info_for_exception, CodeEmitInfo* info) {
  if (!GenerateSynchronizationCode) return;
  // for slow path, use debug info for state after successful locking
  CodeStub* slow_path = new MonitorEnterStub(object, lock, info);
  __ load_stack_address_monitor(monitor_no, lock);
  // for handling NullPointerException, use debug info representing just the lock stack before this monitorenter
  __ lock_object(hdr, object, lock, scratch, slow_path, info_for_exception);
}

void LIRGenerator::monitor_exit(LIR_Opr object, LIR_Opr lock, LIR_Opr new_hdr, LIR_Opr scratch, int monitor_no) {
  if (!GenerateSynchronizationCode) return;
  // setup registers
  LIR_Opr hdr = lock;
  lock = new_hdr;
  CodeStub* slow_path = new MonitorExitStub(lock, !UseHeavyMonitors, monitor_no);
  __ load_stack_address_monitor(monitor_no, lock);
  __ unlock_object(hdr, object, lock, scratch, slow_path);
}

#ifndef PRODUCT
void LIRGenerator::print_if_not_loaded(const NewInstance* new_instance) {
  if (PrintNotLoaded && !new_instance->klass()->is_loaded()) {
    tty->print_cr(" ###class not loaded at new bci %d", new_instance->printable_bci());
  } else if (PrintNotLoaded && (!CompilerConfig::is_c1_only_no_jvmci() && new_instance->is_unresolved())) {
    tty->print_cr(" ###class not resolved at new bci %d", new_instance->printable_bci());
  }
}
#endif

void LIRGenerator::new_instance(LIR_Opr dst, ciInstanceKlass* klass, bool is_unresolved, LIR_Opr scratch1, LIR_Opr scratch2, LIR_Opr scratch3, LIR_Opr scratch4, LIR_Opr klass_reg, CodeEmitInfo* info) {
  klass2reg_with_patching(klass_reg, klass, info, is_unresolved);
  // If klass is not loaded we do not know if the klass has finalizers:
  if (UseFastNewInstance && klass->is_loaded()
      && !Klass::layout_helper_needs_slow_path(klass->layout_helper())) {

    Runtime1::StubID stub_id = klass->is_initialized() ? Runtime1::fast_new_instance_id : Runtime1::fast_new_instance_init_check_id;

    CodeStub* slow_path = new NewInstanceStub(klass_reg, dst, klass, info, stub_id);

    assert(klass->is_loaded(), "must be loaded");
    // allocate space for instance
    assert(klass->size_helper() > 0, "illegal instance size");
    const int instance_size = align_object_size(klass->size_helper());
    __ allocate_object(dst, scratch1, scratch2, scratch3, scratch4,
                       oopDesc::header_size(), instance_size, klass_reg, !klass->is_initialized(), slow_path);
  } else {
    CodeStub* slow_path = new NewInstanceStub(klass_reg, dst, klass, info, Runtime1::new_instance_id);
    __ branch(lir_cond_always, slow_path);
    __ branch_destination(slow_path->continuation());
  }
}

static bool is_constant_zero(Instruction* inst) {
  IntConstant* c = inst->type()->as_IntConstant();
  if (c) {
    return (c->value() == 0);
  }
  return false;
}

static bool positive_constant(Instruction* inst) {
  IntConstant* c = inst->type()->as_IntConstant();
  if (c) {
    return (c->value() >= 0);
  }
  return false;
}

static ciArrayKlass* as_array_klass(ciType* type) {
  if (type != NULL && type->is_array_klass() && type->is_loaded()) {
    return (ciArrayKlass*)type;
  } else {
    return NULL;
  }
}

static ciType* phi_declared_type(Phi* phi) {
  ciType* t = phi->operand_at(0)->declared_type();
  if (t == NULL) {
    return NULL;
  }
  for(int i = 1; i < phi->operand_count(); i++) {
    if (t != phi->operand_at(i)->declared_type()) {
      return NULL;
    }
  }
  return t;
}

void LIRGenerator::arraycopy_helper(Intrinsic* x, int* flagsp, ciArrayKlass** expected_typep) {
  Instruction* src     = x->argument_at(0);
  Instruction* src_pos = x->argument_at(1);
  Instruction* dst     = x->argument_at(2);
  Instruction* dst_pos = x->argument_at(3);
  Instruction* length  = x->argument_at(4);

  // first try to identify the likely type of the arrays involved
  ciArrayKlass* expected_type = NULL;
  bool is_exact = false, src_objarray = false, dst_objarray = false;
  {
    ciArrayKlass* src_exact_type    = as_array_klass(src->exact_type());
    ciArrayKlass* src_declared_type = as_array_klass(src->declared_type());
    Phi* phi;
    if (src_declared_type == NULL && (phi = src->as_Phi()) != NULL) {
      src_declared_type = as_array_klass(phi_declared_type(phi));
    }
    ciArrayKlass* dst_exact_type    = as_array_klass(dst->exact_type());
    ciArrayKlass* dst_declared_type = as_array_klass(dst->declared_type());
    if (dst_declared_type == NULL && (phi = dst->as_Phi()) != NULL) {
      dst_declared_type = as_array_klass(phi_declared_type(phi));
    }

    if (src_exact_type != NULL && src_exact_type == dst_exact_type) {
      // the types exactly match so the type is fully known
      is_exact = true;
      expected_type = src_exact_type;
    } else if (dst_exact_type != NULL && dst_exact_type->is_obj_array_klass()) {
      ciArrayKlass* dst_type = (ciArrayKlass*) dst_exact_type;
      ciArrayKlass* src_type = NULL;
      if (src_exact_type != NULL && src_exact_type->is_obj_array_klass()) {
        src_type = (ciArrayKlass*) src_exact_type;
      } else if (src_declared_type != NULL && src_declared_type->is_obj_array_klass()) {
        src_type = (ciArrayKlass*) src_declared_type;
      }
      if (src_type != NULL) {
        if (src_type->element_type()->is_subtype_of(dst_type->element_type())) {
          is_exact = true;
          expected_type = dst_type;
        }
      }
    }
    // at least pass along a good guess
    if (expected_type == NULL) expected_type = dst_exact_type;
    if (expected_type == NULL) expected_type = src_declared_type;
    if (expected_type == NULL) expected_type = dst_declared_type;

    src_objarray = (src_exact_type && src_exact_type->is_obj_array_klass()) || (src_declared_type && src_declared_type->is_obj_array_klass());
    dst_objarray = (dst_exact_type && dst_exact_type->is_obj_array_klass()) || (dst_declared_type && dst_declared_type->is_obj_array_klass());
  }

  // if a probable array type has been identified, figure out if any
  // of the required checks for a fast case can be elided.
  int flags = LIR_OpArrayCopy::all_flags;

  if (!src_objarray)
    flags &= ~LIR_OpArrayCopy::src_objarray;
  if (!dst_objarray)
    flags &= ~LIR_OpArrayCopy::dst_objarray;

  if (!x->arg_needs_null_check(0))
    flags &= ~LIR_OpArrayCopy::src_null_check;
  if (!x->arg_needs_null_check(2))
    flags &= ~LIR_OpArrayCopy::dst_null_check;

  if (expected_type != NULL) {
    Value length_limit = NULL;

    IfOp* ifop = length->as_IfOp();
    if (ifop != NULL) {
      // look for expressions like min(v, a.length) which ends up as
      //   x > y ? y : x  or  x >= y ? y : x
      if ((ifop->cond() == If::gtr || ifop->cond() == If::geq) &&
          ifop->x() == ifop->fval() &&
          ifop->y() == ifop->tval()) {
        length_limit = ifop->y();
      }
    }

    // try to skip null checks and range checks
    NewArray* src_array = src->as_NewArray();
    if (src_array != NULL) {
      flags &= ~LIR_OpArrayCopy::src_null_check;
      if (length_limit != NULL &&
          src_array->length() == length_limit &&
          is_constant_zero(src_pos)) {
        flags &= ~LIR_OpArrayCopy::src_range_check;
      }
    }

    NewArray* dst_array = dst->as_NewArray();
    if (dst_array != NULL) {
      flags &= ~LIR_OpArrayCopy::dst_null_check;
      if (length_limit != NULL &&
          dst_array->length() == length_limit &&
          is_constant_zero(dst_pos)) {
        flags &= ~LIR_OpArrayCopy::dst_range_check;
      }
    }

    // check from incoming constant values
    if (positive_constant(src_pos))
      flags &= ~LIR_OpArrayCopy::src_pos_positive_check;
    if (positive_constant(dst_pos))
      flags &= ~LIR_OpArrayCopy::dst_pos_positive_check;
    if (positive_constant(length))
      flags &= ~LIR_OpArrayCopy::length_positive_check;

    // see if the range check can be elided, which might also imply
    // that src or dst is non-null.
    ArrayLength* al = length->as_ArrayLength();
    if (al != NULL) {
      if (al->array() == src) {
        // it's the length of the source array
        flags &= ~LIR_OpArrayCopy::length_positive_check;
        flags &= ~LIR_OpArrayCopy::src_null_check;
        if (is_constant_zero(src_pos))
          flags &= ~LIR_OpArrayCopy::src_range_check;
      }
      if (al->array() == dst) {
        // it's the length of the destination array
        flags &= ~LIR_OpArrayCopy::length_positive_check;
        flags &= ~LIR_OpArrayCopy::dst_null_check;
        if (is_constant_zero(dst_pos))
          flags &= ~LIR_OpArrayCopy::dst_range_check;
      }
    }
    if (is_exact) {
      flags &= ~LIR_OpArrayCopy::type_check;
    }
  }

  IntConstant* src_int = src_pos->type()->as_IntConstant();
  IntConstant* dst_int = dst_pos->type()->as_IntConstant();
  if (src_int && dst_int) {
    int s_offs = src_int->value();
    int d_offs = dst_int->value();
    if (src_int->value() >= dst_int->value()) {
      flags &= ~LIR_OpArrayCopy::overlapping;
    }
    if (expected_type != NULL) {
      BasicType t = expected_type->element_type()->basic_type();
      int element_size = type2aelembytes(t);
      if (((arrayOopDesc::base_offset_in_bytes(t) + s_offs * element_size) % HeapWordSize == 0) &&
          ((arrayOopDesc::base_offset_in_bytes(t) + d_offs * element_size) % HeapWordSize == 0)) {
        flags &= ~LIR_OpArrayCopy::unaligned;
      }
    }
  } else if (src_pos == dst_pos || is_constant_zero(dst_pos)) {
    // src and dest positions are the same, or dst is zero so assume
    // nonoverlapping copy.
    flags &= ~LIR_OpArrayCopy::overlapping;
  }

  if (src == dst) {
    // moving within a single array so no type checks are needed
    if (flags & LIR_OpArrayCopy::type_check) {
      flags &= ~LIR_OpArrayCopy::type_check;
    }
  }
  *flagsp = flags;
  *expected_typep = (ciArrayKlass*)expected_type;
}

LIR_Opr LIRGenerator::round_item(LIR_Opr opr) {
  assert(opr->is_register(), "why spill if item is not register?");

  if (strict_fp_requires_explicit_rounding) {
#ifdef IA32
    if (UseSSE < 1 && opr->is_single_fpu()) {
      LIR_Opr result = new_register(T_FLOAT);
      set_vreg_flag(result, must_start_in_memory);
      assert(opr->is_register(), "only a register can be spilled");
      assert(opr->value_type()->is_float(), "rounding only for floats available");
      __ roundfp(opr, LIR_OprFact::illegalOpr, result);
      return result;
    }
#else
    Unimplemented();
#endif // IA32
  }
  return opr;
}

LIR_Opr LIRGenerator::force_to_spill(LIR_Opr value, BasicType t) {
  assert(type2size[t] == type2size[value->type()],
         "size mismatch: t=%s, value->type()=%s", type2name(t), type2name(value->type()));
  if (!value->is_register()) {
    // force into a register
    LIR_Opr r = new_register(value->type());
    __ move(value, r);
    value = r;
  }

  // create a spill location
  LIR_Opr tmp = new_register(t);
  set_vreg_flag(tmp, LIRGenerator::must_start_in_memory);

  // move from register to spill
  __ move(value, tmp);
  return tmp;
}

void LIRGenerator::profile_branch(If* if_instr, If::Condition cond) {
  if (if_instr->should_profile()) {
    ciMethod* method = if_instr->profiled_method();
    assert(method != NULL, "method should be set if branch is profiled");
    ciMethodData* md = method->method_data_or_null();
    assert(md != NULL, "Sanity");
    ciProfileData* data = md->bci_to_data(if_instr->profiled_bci());
    assert(data != NULL, "must have profiling data");
    assert(data->is_BranchData(), "need BranchData for two-way branches");
    int taken_count_offset     = md->byte_offset_of_slot(data, BranchData::taken_offset());
    int not_taken_count_offset = md->byte_offset_of_slot(data, BranchData::not_taken_offset());
    if (if_instr->is_swapped()) {
      int t = taken_count_offset;
      taken_count_offset = not_taken_count_offset;
      not_taken_count_offset = t;
    }

    LIR_Opr md_reg = new_register(T_METADATA);
    __ metadata2reg(md->constant_encoding(), md_reg);

    LIR_Opr data_offset_reg = new_pointer_register();
    __ cmove(lir_cond(cond),
             LIR_OprFact::intptrConst(taken_count_offset),
             LIR_OprFact::intptrConst(not_taken_count_offset),
             data_offset_reg, as_BasicType(if_instr->x()->type()));

    // MDO cells are intptr_t, so the data_reg width is arch-dependent.
    LIR_Opr data_reg = new_pointer_register();
    LIR_Address* data_addr = new LIR_Address(md_reg, data_offset_reg, data_reg->type());
    __ move(data_addr, data_reg);
    // Use leal instead of add to avoid destroying condition codes on x86
    LIR_Address* fake_incr_value = new LIR_Address(data_reg, DataLayout::counter_increment, T_INT);
    __ leal(LIR_OprFact::address(fake_incr_value), data_reg);
    __ move(data_reg, data_addr);
  }
}

// Phi technique:
// This is about passing live values from one basic block to the other.
// In code generated with Java it is rather rare that more than one
// value is on the stack from one basic block to the other.
// We optimize our technique for efficient passing of one value
// (of type long, int, double..) but it can be extended.
// When entering or leaving a basic block, all registers and all spill
// slots are release and empty. We use the released registers
// and spill slots to pass the live values from one block
// to the other. The topmost value, i.e., the value on TOS of expression
// stack is passed in registers. All other values are stored in spilling
// area. Every Phi has an index which designates its spill slot
// At exit of a basic block, we fill the register(s) and spill slots.
// At entry of a basic block, the block_prolog sets up the content of phi nodes
// and locks necessary registers and spilling slots.

// move current value to referenced phi function
void LIRGenerator::move_to_phi(PhiResolver* resolver, Value cur_val, Value sux_val) {
  Phi* phi = sux_val->as_Phi();
  // cur_val can be null without phi being null in conjunction with inlining
  if (phi != NULL && cur_val != NULL && cur_val != phi && !phi->is_illegal()) {
    if (phi->is_local()) {
      for (int i = 0; i < phi->operand_count(); i++) {
        Value op = phi->operand_at(i);
        if (op != NULL && op->type()->is_illegal()) {
          bailout("illegal phi operand");
        }
      }
    }
    Phi* cur_phi = cur_val->as_Phi();
    if (cur_phi != NULL && cur_phi->is_illegal()) {
      // Phi and local would need to get invalidated
      // (which is unexpected for Linear Scan).
      // But this case is very rare so we simply bail out.
      bailout("propagation of illegal phi");
      return;
    }
    LIR_Opr operand = cur_val->operand();
    if (operand->is_illegal()) {
      assert(cur_val->as_Constant() != NULL || cur_val->as_Local() != NULL,
             "these can be produced lazily");
      operand = operand_for_instruction(cur_val);
    }
    resolver->move(operand, operand_for_instruction(phi));
  }
}

// Moves all stack values into their PHI position
void LIRGenerator::move_to_phi(ValueStack* cur_state) {
  BlockBegin* bb = block();
  if (bb->number_of_sux() == 1) {
    BlockBegin* sux = bb->sux_at(0);
    assert(sux->number_of_preds() > 0, "invalid CFG");

    // a block with only one predecessor never has phi functions
    if (sux->number_of_preds() > 1) {
      PhiResolver resolver(this);

      ValueStack* sux_state = sux->state();
      Value sux_value;
      int index;

      assert(cur_state->scope() == sux_state->scope(), "not matching");
      assert(cur_state->locals_size() == sux_state->locals_size(), "not matching");
      assert(cur_state->stack_size() == sux_state->stack_size(), "not matching");

      for_each_stack_value(sux_state, index, sux_value) {
        move_to_phi(&resolver, cur_state->stack_at(index), sux_value);
      }

      for_each_local_value(sux_state, index, sux_value) {
        move_to_phi(&resolver, cur_state->local_at(index), sux_value);
      }

      assert(cur_state->caller_state() == sux_state->caller_state(), "caller states must be equal");
    }
  }
}

LIR_Opr LIRGenerator::new_register(BasicType type) {
  int vreg_num = _virtual_register_number;
  // Add a little fudge factor for the bailout since the bailout is only checked periodically. This allows us to hand out
  // a few extra registers before we really run out which helps to avoid to trip over assertions.
  if (vreg_num + 20 >= LIR_Opr::vreg_max) {
    bailout("out of virtual registers in LIR generator");
    if (vreg_num + 2 >= LIR_Opr::vreg_max) {
      // Wrap it around and continue until bailout really happens to avoid hitting assertions.
      _virtual_register_number = LIR_Opr::vreg_base;
      vreg_num = LIR_Opr::vreg_base;
    }
  }
  _virtual_register_number += 1;
  LIR_Opr vreg = LIR_OprFact::virtual_register(vreg_num, type);
  assert(vreg != LIR_OprFact::illegal(), "ran out of virtual registers");
  return vreg;
}

// Try to lock using register in hint
LIR_Opr LIRGenerator::rlock(Value instr) {
  return new_register(instr->type());
}

// does an rlock and sets result
LIR_Opr LIRGenerator::rlock_result(Value x) {
  LIR_Opr reg = rlock(x);
  set_result(x, reg);
  return reg;
}

// does an rlock and sets result
LIR_Opr LIRGenerator::rlock_result(Value x, BasicType type) {
  LIR_Opr reg;
  switch (type) {
  case T_BYTE:
  case T_BOOLEAN:
    reg = rlock_byte(type);
    break;
  default:
    reg = rlock(x);
    break;
  }

  set_result(x, reg);
  return reg;
}

//---------------------------------------------------------------------
ciObject* LIRGenerator::get_jobject_constant(Value value) {
  ObjectType* oc = value->type()->as_ObjectType();
  if (oc) {
    return oc->constant_value();
  }
  return NULL;
}

void LIRGenerator::do_ExceptionObject(ExceptionObject* x) {
  assert(block()->is_set(BlockBegin::exception_entry_flag), "ExceptionObject only allowed in exception handler block");
  assert(block()->next() == x, "ExceptionObject must be first instruction of block");

  // no moves are created for phi functions at the begin of exception
  // handlers, so assign operands manually here
  for_each_phi_fun(block(), phi,
                   if (!phi->is_illegal()) { operand_for_instruction(phi); });

  LIR_Opr thread_reg = getThreadPointer();
  __ move_wide(new LIR_Address(thread_reg, in_bytes(JavaThread::exception_oop_offset()), T_OBJECT),
               exceptionOopOpr());
  __ move_wide(LIR_OprFact::oopConst(NULL),
               new LIR_Address(thread_reg, in_bytes(JavaThread::exception_oop_offset()), T_OBJECT));
  __ move_wide(LIR_OprFact::oopConst(NULL),
               new LIR_Address(thread_reg, in_bytes(JavaThread::exception_pc_offset()), T_OBJECT));

  LIR_Opr result = new_register(T_OBJECT);
  __ move(exceptionOopOpr(), result);
  set_result(x, result);
}

//----------------------------------------------------------------------
//----------------------------------------------------------------------
//----------------------------------------------------------------------
//----------------------------------------------------------------------
//                        visitor functions
//----------------------------------------------------------------------
//----------------------------------------------------------------------
//----------------------------------------------------------------------
//----------------------------------------------------------------------

void LIRGenerator::do_Phi(Phi* x) {
  // phi functions are never visited directly
  ShouldNotReachHere();
}

// Code for a constant is generated lazily unless the constant is frequently used and can't be inlined.
void LIRGenerator::do_Constant(Constant* x) {
  if (x->state_before() != NULL) {
    // Any constant with a ValueStack requires patching so emit the patch here
    LIR_Opr reg = rlock_result(x);
    CodeEmitInfo* info = state_for(x, x->state_before());
    __ oop2reg_patch(NULL, reg, info);
  } else if (x->use_count() > 1 && !can_inline_as_constant(x)) {
    if (!x->is_pinned()) {
      // unpinned constants are handled specially so that they can be
      // put into registers when they are used multiple times within a
      // block.  After the block completes their operand will be
      // cleared so that other blocks can't refer to that register.
      set_result(x, load_constant(x));
    } else {
      LIR_Opr res = x->operand();
      if (!res->is_valid()) {
        res = LIR_OprFact::value_type(x->type());
      }
      if (res->is_constant()) {
        LIR_Opr reg = rlock_result(x);
        __ move(res, reg);
      } else {
        set_result(x, res);
      }
    }
  } else {
    set_result(x, LIR_OprFact::value_type(x->type()));
  }
}

void LIRGenerator::do_Local(Local* x) {
  // operand_for_instruction has the side effect of setting the result
  // so there's no need to do it here.
  operand_for_instruction(x);
}

void LIRGenerator::do_Return(Return* x) {
  if (compilation()->env()->dtrace_method_probes()) {
    BasicTypeList signature;
    signature.append(LP64_ONLY(T_LONG) NOT_LP64(T_INT));    // thread
    signature.append(T_METADATA); // Method*
    LIR_OprList* args = new LIR_OprList();
    args->append(getThreadPointer());
    LIR_Opr meth = new_register(T_METADATA);
    __ metadata2reg(method()->constant_encoding(), meth);
    args->append(meth);
    call_runtime(&signature, args, CAST_FROM_FN_PTR(address, SharedRuntime::dtrace_method_exit), voidType, NULL);
  }

  if (x->type()->is_void()) {
    __ return_op(LIR_OprFact::illegalOpr);
  } else {
    LIR_Opr reg = result_register_for(x->type(), /*callee=*/true);
    LIRItem result(x->result(), this);

    result.load_item_force(reg);
    __ return_op(result.result());
  }
  set_no_result(x);
}

// Example: ref.get()
// Combination of LoadField and g1 pre-write barrier
void LIRGenerator::do_Reference_get(Intrinsic* x) {

  const int referent_offset = java_lang_ref_Reference::referent_offset();

  assert(x->number_of_arguments() == 1, "wrong type");

  LIRItem reference(x->argument_at(0), this);
  reference.load_item();

  // need to perform the null check on the reference object
  CodeEmitInfo* info = NULL;
  if (x->needs_null_check()) {
    info = state_for(x);
  }

  LIR_Opr result = rlock_result(x, T_OBJECT);
  access_load_at(IN_HEAP | ON_WEAK_OOP_REF, T_OBJECT,
                 reference, LIR_OprFact::intConst(referent_offset), result);
}

// Example: clazz.isInstance(object)
void LIRGenerator::do_isInstance(Intrinsic* x) {
  assert(x->number_of_arguments() == 2, "wrong type");

  // TODO could try to substitute this node with an equivalent InstanceOf
  // if clazz is known to be a constant Class. This will pick up newly found
  // constants after HIR construction. I'll leave this to a future change.

  // as a first cut, make a simple leaf call to runtime to stay platform independent.
  // could follow the aastore example in a future change.

  LIRItem clazz(x->argument_at(0), this);
  LIRItem object(x->argument_at(1), this);
  clazz.load_item();
  object.load_item();
  LIR_Opr result = rlock_result(x);

  // need to perform null check on clazz
  if (x->needs_null_check()) {
    CodeEmitInfo* info = state_for(x);
    __ null_check(clazz.result(), info);
  }

  LIR_Opr call_result = call_runtime(clazz.value(), object.value(),
                                     CAST_FROM_FN_PTR(address, Runtime1::is_instance_of),
                                     x->type(),
                                     NULL); // NULL CodeEmitInfo results in a leaf call
  __ move(call_result, result);
}

void LIRGenerator::load_klass(LIR_Opr obj, LIR_Opr klass, CodeEmitInfo* null_check_info) {
  __ load_klass(obj, klass, null_check_info);
}

// Example: object.getClass ()
void LIRGenerator::do_getClass(Intrinsic* x) {
  assert(x->number_of_arguments() == 1, "wrong type");

  LIRItem rcvr(x->argument_at(0), this);
  rcvr.load_item();
  LIR_Opr temp = new_register(T_ADDRESS);
  LIR_Opr result = rlock_result(x);

  // need to perform the null check on the rcvr
  CodeEmitInfo* info = NULL;
  if (x->needs_null_check()) {
    info = state_for(x);
  }

  LIR_Opr klass = new_register(T_METADATA);
  load_klass(rcvr.result(), klass, info);
  __ move_wide(new LIR_Address(klass, in_bytes(Klass::java_mirror_offset()), T_ADDRESS), temp);
  // mirror = ((OopHandle)mirror)->resolve();
  access_load(IN_NATIVE, T_OBJECT,
              LIR_OprFact::address(new LIR_Address(temp, T_OBJECT)), result);
}

// java.lang.Class::isPrimitive()
void LIRGenerator::do_isPrimitive(Intrinsic* x) {
  assert(x->number_of_arguments() == 1, "wrong type");

  LIRItem rcvr(x->argument_at(0), this);
  rcvr.load_item();
  LIR_Opr temp = new_register(T_METADATA);
  LIR_Opr result = rlock_result(x);

  CodeEmitInfo* info = NULL;
  if (x->needs_null_check()) {
    info = state_for(x);
  }

  __ move(new LIR_Address(rcvr.result(), java_lang_Class::klass_offset(), T_ADDRESS), temp, info);
  __ cmp(lir_cond_notEqual, temp, LIR_OprFact::metadataConst(0));
  __ cmove(lir_cond_notEqual, LIR_OprFact::intConst(0), LIR_OprFact::intConst(1), result, T_BOOLEAN);
}

// Example: Foo.class.getModifiers()
void LIRGenerator::do_getModifiers(Intrinsic* x) {
  assert(x->number_of_arguments() == 1, "wrong type");

  LIRItem receiver(x->argument_at(0), this);
  receiver.load_item();
  LIR_Opr result = rlock_result(x);

  CodeEmitInfo* info = NULL;
  if (x->needs_null_check()) {
    info = state_for(x);
  }

  // While reading off the universal constant mirror is less efficient than doing
  // another branch and returning the constant answer, this branchless code runs into
  // much less risk of confusion for C1 register allocator. The choice of the universe
  // object here is correct as long as it returns the same modifiers we would expect
  // from the primitive class itself. See spec for Class.getModifiers that provides
  // the typed array klasses with similar modifiers as their component types.

  Klass* univ_klass_obj = Universe::byteArrayKlassObj();
  assert(univ_klass_obj->modifier_flags() == (JVM_ACC_ABSTRACT | JVM_ACC_FINAL | JVM_ACC_PUBLIC), "Sanity");
  LIR_Opr prim_klass = LIR_OprFact::metadataConst(univ_klass_obj);

  LIR_Opr recv_klass = new_register(T_METADATA);
  __ move(new LIR_Address(receiver.result(), java_lang_Class::klass_offset(), T_ADDRESS), recv_klass, info);

  // Check if this is a Java mirror of primitive type, and select the appropriate klass.
  LIR_Opr klass = new_register(T_METADATA);
  __ cmp(lir_cond_equal, recv_klass, LIR_OprFact::metadataConst(0));
  __ cmove(lir_cond_equal, prim_klass, recv_klass, klass, T_ADDRESS);

  // Get the answer.
  __ move(new LIR_Address(klass, in_bytes(Klass::modifier_flags_offset()), T_INT), result);
}

void LIRGenerator::do_getObjectSize(Intrinsic* x) {
  assert(x->number_of_arguments() == 3, "wrong type");
  LIR_Opr result_reg = rlock_result(x);

  LIRItem value(x->argument_at(2), this);
  value.load_item();

  LIR_Opr klass = new_register(T_METADATA);
  load_klass(value.result(), klass, NULL);
  LIR_Opr layout = new_register(T_INT);
  __ move(new LIR_Address(klass, in_bytes(Klass::layout_helper_offset()), T_INT), layout);

  LabelObj* L_done = new LabelObj();
  LabelObj* L_array = new LabelObj();

  __ cmp(lir_cond_lessEqual, layout, 0);
  __ branch(lir_cond_lessEqual, L_array->label());

  // Instance case: the layout helper gives us instance size almost directly,
  // but we need to mask out the _lh_instance_slow_path_bit.

  assert((int) Klass::_lh_instance_slow_path_bit < BytesPerLong, "clear bit");

  LIR_Opr mask = load_immediate(~(jint) right_n_bits(LogBytesPerLong), T_INT);
  __ logical_and(layout, mask, layout);
  __ convert(Bytecodes::_i2l, layout, result_reg);

  __ branch(lir_cond_always, L_done->label());

  // Array case: size is round(header + element_size*arraylength).
  // Since arraylength is different for every array instance, we have to
  // compute the whole thing at runtime.

  __ branch_destination(L_array->label());

  int round_mask = MinObjAlignmentInBytes - 1;

  // Figure out header sizes first.
  LIR_Opr hss = load_immediate(Klass::_lh_header_size_shift, T_INT);
  LIR_Opr hsm = load_immediate(Klass::_lh_header_size_mask, T_INT);

  LIR_Opr header_size = new_register(T_INT);
  __ move(layout, header_size);
  LIR_Opr tmp = new_register(T_INT);
  __ unsigned_shift_right(header_size, hss, header_size, tmp);
  __ logical_and(header_size, hsm, header_size);
  __ add(header_size, LIR_OprFact::intConst(round_mask), header_size);

  // Figure out the array length in bytes
  assert(Klass::_lh_log2_element_size_shift == 0, "use shift in place");
  LIR_Opr l2esm = load_immediate(Klass::_lh_log2_element_size_mask, T_INT);
  __ logical_and(layout, l2esm, layout);

  LIR_Opr length_int = new_register(T_INT);
  __ move(new LIR_Address(value.result(), arrayOopDesc::length_offset_in_bytes(), T_INT), length_int);

#ifdef _LP64
  LIR_Opr length = new_register(T_LONG);
  __ convert(Bytecodes::_i2l, length_int, length);
#endif

  // Shift-left awkwardness. Normally it is just:
  //   __ shift_left(length, layout, length);
  // But C1 cannot perform shift_left with non-constant count, so we end up
  // doing the per-bit loop dance here. x86_32 also does not know how to shift
  // longs, so we have to act on ints.
  LabelObj* L_shift_loop = new LabelObj();
  LabelObj* L_shift_exit = new LabelObj();

  __ branch_destination(L_shift_loop->label());
  __ cmp(lir_cond_equal, layout, 0);
  __ branch(lir_cond_equal, L_shift_exit->label());

#ifdef _LP64
  __ shift_left(length, 1, length);
#else
  __ shift_left(length_int, 1, length_int);
#endif

  __ sub(layout, LIR_OprFact::intConst(1), layout);

  __ branch(lir_cond_always, L_shift_loop->label());
  __ branch_destination(L_shift_exit->label());

  // Mix all up, round, and push to the result.
#ifdef _LP64
  LIR_Opr header_size_long = new_register(T_LONG);
  __ convert(Bytecodes::_i2l, header_size, header_size_long);
  __ add(length, header_size_long, length);
  if (round_mask != 0) {
    LIR_Opr round_mask_opr = load_immediate(~(jlong)round_mask, T_LONG);
    __ logical_and(length, round_mask_opr, length);
  }
  __ move(length, result_reg);
#else
  __ add(length_int, header_size, length_int);
  if (round_mask != 0) {
    LIR_Opr round_mask_opr = load_immediate(~round_mask, T_INT);
    __ logical_and(length_int, round_mask_opr, length_int);
  }
  __ convert(Bytecodes::_i2l, length_int, result_reg);
#endif

  __ branch_destination(L_done->label());
}

void LIRGenerator::do_scopedValueCache(Intrinsic* x) {
  do_JavaThreadField(x, JavaThread::scopedValueCache_offset());
}

// Example: Thread.currentCarrierThread()
void LIRGenerator::do_currentCarrierThread(Intrinsic* x) {
  do_JavaThreadField(x, JavaThread::threadObj_offset());
}

void LIRGenerator::do_vthread(Intrinsic* x) {
  do_JavaThreadField(x, JavaThread::vthread_offset());
}

void LIRGenerator::do_JavaThreadField(Intrinsic* x, ByteSize offset) {
  assert(x->number_of_arguments() == 0, "wrong type");
  LIR_Opr temp = new_register(T_ADDRESS);
  LIR_Opr reg = rlock_result(x);
  __ move(new LIR_Address(getThreadPointer(), in_bytes(offset), T_ADDRESS), temp);
  access_load(IN_NATIVE, T_OBJECT,
              LIR_OprFact::address(new LIR_Address(temp, T_OBJECT)), reg);
}

void LIRGenerator::do_RegisterFinalizer(Intrinsic* x) {
  assert(x->number_of_arguments() == 1, "wrong type");
  LIRItem receiver(x->argument_at(0), this);

  receiver.load_item();
  BasicTypeList signature;
  signature.append(T_OBJECT); // receiver
  LIR_OprList* args = new LIR_OprList();
  args->append(receiver.result());
  CodeEmitInfo* info = state_for(x, x->state());
  call_runtime(&signature, args,
               CAST_FROM_FN_PTR(address, Runtime1::entry_for(Runtime1::register_finalizer_id)),
               voidType, info);

  set_no_result(x);
}

//------------------------local access--------------------------------------

LIR_Opr LIRGenerator::operand_for_instruction(Instruction* x) {
  if (x->operand()->is_illegal()) {
    Constant* c = x->as_Constant();
    if (c != NULL) {
      x->set_operand(LIR_OprFact::value_type(c->type()));
    } else {
      assert(x->as_Phi() || x->as_Local() != NULL, "only for Phi and Local");
      // allocate a virtual register for this local or phi
      x->set_operand(rlock(x));
      _instruction_for_operand.at_put_grow(x->operand()->vreg_number(), x, NULL);
    }
  }
  return x->operand();
}

Instruction* LIRGenerator::instruction_for_opr(LIR_Opr opr) {
  if (opr->is_virtual()) {
    return instruction_for_vreg(opr->vreg_number());
  }
  return NULL;
}

Instruction* LIRGenerator::instruction_for_vreg(int reg_num) {
  if (reg_num < _instruction_for_operand.length()) {
    return _instruction_for_operand.at(reg_num);
  }
  return NULL;
}

void LIRGenerator::set_vreg_flag(int vreg_num, VregFlag f) {
  if (_vreg_flags.size_in_bits() == 0) {
    BitMap2D temp(100, num_vreg_flags);
    _vreg_flags = temp;
  }
  _vreg_flags.at_put_grow(vreg_num, f, true);
}

bool LIRGenerator::is_vreg_flag_set(int vreg_num, VregFlag f) {
  if (!_vreg_flags.is_valid_index(vreg_num, f)) {
    return false;
  }
  return _vreg_flags.at(vreg_num, f);
}

// Block local constant handling.  This code is useful for keeping
// unpinned constants and constants which aren't exposed in the IR in
// registers.  Unpinned Constant instructions have their operands
// cleared when the block is finished so that other blocks can't end
// up referring to their registers.

LIR_Opr LIRGenerator::load_constant(Constant* x) {
  assert(!x->is_pinned(), "only for unpinned constants");
  _unpinned_constants.append(x);
  return load_constant(LIR_OprFact::value_type(x->type())->as_constant_ptr());
}

LIR_Opr LIRGenerator::load_constant(LIR_Const* c) {
  BasicType t = c->type();
  for (int i = 0; i < _constants.length(); i++) {
    LIR_Const* other = _constants.at(i);
    if (t == other->type()) {
      switch (t) {
      case T_INT:
      case T_FLOAT:
        if (c->as_jint_bits() != other->as_jint_bits()) continue;
        break;
      case T_LONG:
      case T_DOUBLE:
        if (c->as_jint_hi_bits() != other->as_jint_hi_bits()) continue;
        if (c->as_jint_lo_bits() != other->as_jint_lo_bits()) continue;
        break;
      case T_OBJECT:
        if (c->as_jobject() != other->as_jobject()) continue;
        break;
      default:
        break;
      }
      return _reg_for_constants.at(i);
    }
  }

  LIR_Opr result = new_register(t);
  __ move((LIR_Opr)c, result);
  _constants.append(c);
  _reg_for_constants.append(result);
  return result;
}

//------------------------field access--------------------------------------

void LIRGenerator::do_CompareAndSwap(Intrinsic* x, ValueType* type) {
  assert(x->number_of_arguments() == 4, "wrong type");
  LIRItem obj   (x->argument_at(0), this);  // object
  LIRItem offset(x->argument_at(1), this);  // offset of field
  LIRItem cmp   (x->argument_at(2), this);  // value to compare with field
  LIRItem val   (x->argument_at(3), this);  // replace field with val if matches cmp
  assert(obj.type()->tag() == objectTag, "invalid type");
  assert(cmp.type()->tag() == type->tag(), "invalid type");
  assert(val.type()->tag() == type->tag(), "invalid type");

  LIR_Opr result = access_atomic_cmpxchg_at(IN_HEAP, as_BasicType(type),
                                            obj, offset, cmp, val);
  set_result(x, result);
}

// Comment copied form templateTable_i486.cpp
// ----------------------------------------------------------------------------
// Volatile variables demand their effects be made known to all CPU's in
// order.  Store buffers on most chips allow reads & writes to reorder; the
// JMM's ReadAfterWrite.java test fails in -Xint mode without some kind of
// memory barrier (i.e., it's not sufficient that the interpreter does not
// reorder volatile references, the hardware also must not reorder them).
//
// According to the new Java Memory Model (JMM):
// (1) All volatiles are serialized wrt to each other.
// ALSO reads & writes act as acquire & release, so:
// (2) A read cannot let unrelated NON-volatile memory refs that happen after
// the read float up to before the read.  It's OK for non-volatile memory refs
// that happen before the volatile read to float down below it.
// (3) Similar a volatile write cannot let unrelated NON-volatile memory refs
// that happen BEFORE the write float down to after the write.  It's OK for
// non-volatile memory refs that happen after the volatile write to float up
// before it.
//
// We only put in barriers around volatile refs (they are expensive), not
// _between_ memory refs (that would require us to track the flavor of the
// previous memory refs).  Requirements (2) and (3) require some barriers
// before volatile stores and after volatile loads.  These nearly cover
// requirement (1) but miss the volatile-store-volatile-load case.  This final
// case is placed after volatile-stores although it could just as well go
// before volatile-loads.

void LIRGenerator::do_StoreField(StoreField* x) {
  bool needs_patching = x->needs_patching();
  bool is_volatile = x->field()->is_volatile();
  BasicType field_type = x->field_type();

  CodeEmitInfo* info = NULL;
  if (needs_patching) {
    assert(x->explicit_null_check() == NULL, "can't fold null check into patching field access");
    info = state_for(x, x->state_before());
  } else if (x->needs_null_check()) {
    NullCheck* nc = x->explicit_null_check();
    if (nc == NULL) {
      info = state_for(x);
    } else {
      info = state_for(nc);
    }
  }

  LIRItem object(x->obj(), this);
  LIRItem value(x->value(),  this);

  object.load_item();

  if (is_volatile || needs_patching) {
    // load item if field is volatile (fewer special cases for volatiles)
    // load item if field not initialized
    // load item if field not constant
    // because of code patching we cannot inline constants
    if (field_type == T_BYTE || field_type == T_BOOLEAN) {
      value.load_byte_item();
    } else  {
      value.load_item();
    }
  } else {
    value.load_for_store(field_type);
  }

  set_no_result(x);

#ifndef PRODUCT
  if (PrintNotLoaded && needs_patching) {
    tty->print_cr(" ###class not loaded at store_%s bci %d",
                  x->is_static() ?  "static" : "field", x->printable_bci());
  }
#endif

  if (x->needs_null_check() &&
      (needs_patching ||
       MacroAssembler::needs_explicit_null_check(x->offset()))) {
    // Emit an explicit null check because the offset is too large.
    // If the class is not loaded and the object is NULL, we need to deoptimize to throw a
    // NoClassDefFoundError in the interpreter instead of an implicit NPE from compiled code.
    __ null_check(object.result(), new CodeEmitInfo(info), /* deoptimize */ needs_patching);
  }

  DecoratorSet decorators = IN_HEAP;
  if (is_volatile) {
    decorators |= MO_SEQ_CST;
  }
  if (needs_patching) {
    decorators |= C1_NEEDS_PATCHING;
  }

  access_store_at(decorators, field_type, object, LIR_OprFact::intConst(x->offset()),
                  value.result(), info != NULL ? new CodeEmitInfo(info) : NULL, info);
}

void LIRGenerator::do_StoreIndexed(StoreIndexed* x) {
  assert(x->is_pinned(),"");
  bool needs_range_check = x->compute_needs_range_check();
  bool use_length = x->length() != NULL;
  bool obj_store = is_reference_type(x->elt_type());
  bool needs_store_check = obj_store && (x->value()->as_Constant() == NULL ||
                                         !get_jobject_constant(x->value())->is_null_object() ||
                                         x->should_profile());

  LIRItem array(x->array(), this);
  LIRItem index(x->index(), this);
  LIRItem value(x->value(), this);
  LIRItem length(this);

  array.load_item();
  index.load_nonconstant();

  if (use_length && needs_range_check) {
    length.set_instruction(x->length());
    length.load_item();

  }
  if (needs_store_check || x->check_boolean()) {
    value.load_item();
  } else {
    value.load_for_store(x->elt_type());
  }

  set_no_result(x);

  // the CodeEmitInfo must be duplicated for each different
  // LIR-instruction because spilling can occur anywhere between two
  // instructions and so the debug information must be different
  CodeEmitInfo* range_check_info = state_for(x);
  CodeEmitInfo* null_check_info = NULL;
  if (x->needs_null_check()) {
    null_check_info = new CodeEmitInfo(range_check_info);
  }

  if (GenerateRangeChecks && needs_range_check) {
    if (use_length) {
      __ cmp(lir_cond_belowEqual, length.result(), index.result());
      __ branch(lir_cond_belowEqual, new RangeCheckStub(range_check_info, index.result(), array.result()));
    } else {
      array_range_check(array.result(), index.result(), null_check_info, range_check_info);
      // range_check also does the null check
      null_check_info = NULL;
    }
  }

  if (GenerateArrayStoreCheck && needs_store_check) {
    CodeEmitInfo* store_check_info = new CodeEmitInfo(range_check_info);
    array_store_check(value.result(), array.result(), store_check_info, x->profiled_method(), x->profiled_bci());
  }

  DecoratorSet decorators = IN_HEAP | IS_ARRAY;
  if (x->check_boolean()) {
    decorators |= C1_MASK_BOOLEAN;
  }

  access_store_at(decorators, x->elt_type(), array, index.result(), value.result(),
                  NULL, null_check_info);
}

void LIRGenerator::access_load_at(DecoratorSet decorators, BasicType type,
                                  LIRItem& base, LIR_Opr offset, LIR_Opr result,
                                  CodeEmitInfo* patch_info, CodeEmitInfo* load_emit_info) {
  decorators |= ACCESS_READ;
  LIRAccess access(this, decorators, base, offset, type, patch_info, load_emit_info);
  if (access.is_raw()) {
    _barrier_set->BarrierSetC1::load_at(access, result);
  } else {
    _barrier_set->load_at(access, result);
  }
}

void LIRGenerator::access_load(DecoratorSet decorators, BasicType type,
                               LIR_Opr addr, LIR_Opr result) {
  decorators |= ACCESS_READ;
  LIRAccess access(this, decorators, LIR_OprFact::illegalOpr, LIR_OprFact::illegalOpr, type);
  access.set_resolved_addr(addr);
  if (access.is_raw()) {
    _barrier_set->BarrierSetC1::load(access, result);
  } else {
    _barrier_set->load(access, result);
  }
}

void LIRGenerator::access_store_at(DecoratorSet decorators, BasicType type,
                                   LIRItem& base, LIR_Opr offset, LIR_Opr value,
                                   CodeEmitInfo* patch_info, CodeEmitInfo* store_emit_info) {
  decorators |= ACCESS_WRITE;
  LIRAccess access(this, decorators, base, offset, type, patch_info, store_emit_info);
  if (access.is_raw()) {
    _barrier_set->BarrierSetC1::store_at(access, value);
  } else {
    _barrier_set->store_at(access, value);
  }
}

LIR_Opr LIRGenerator::access_atomic_cmpxchg_at(DecoratorSet decorators, BasicType type,
                                               LIRItem& base, LIRItem& offset, LIRItem& cmp_value, LIRItem& new_value) {
  decorators |= ACCESS_READ;
  decorators |= ACCESS_WRITE;
  // Atomic operations are SEQ_CST by default
  decorators |= ((decorators & MO_DECORATOR_MASK) == 0) ? MO_SEQ_CST : 0;
  LIRAccess access(this, decorators, base, offset, type);
  if (access.is_raw()) {
    return _barrier_set->BarrierSetC1::atomic_cmpxchg_at(access, cmp_value, new_value);
  } else {
    return _barrier_set->atomic_cmpxchg_at(access, cmp_value, new_value);
  }
}

LIR_Opr LIRGenerator::access_atomic_xchg_at(DecoratorSet decorators, BasicType type,
                                            LIRItem& base, LIRItem& offset, LIRItem& value) {
  decorators |= ACCESS_READ;
  decorators |= ACCESS_WRITE;
  // Atomic operations are SEQ_CST by default
  decorators |= ((decorators & MO_DECORATOR_MASK) == 0) ? MO_SEQ_CST : 0;
  LIRAccess access(this, decorators, base, offset, type);
  if (access.is_raw()) {
    return _barrier_set->BarrierSetC1::atomic_xchg_at(access, value);
  } else {
    return _barrier_set->atomic_xchg_at(access, value);
  }
}

LIR_Opr LIRGenerator::access_atomic_add_at(DecoratorSet decorators, BasicType type,
                                           LIRItem& base, LIRItem& offset, LIRItem& value) {
  decorators |= ACCESS_READ;
  decorators |= ACCESS_WRITE;
  // Atomic operations are SEQ_CST by default
  decorators |= ((decorators & MO_DECORATOR_MASK) == 0) ? MO_SEQ_CST : 0;
  LIRAccess access(this, decorators, base, offset, type);
  if (access.is_raw()) {
    return _barrier_set->BarrierSetC1::atomic_add_at(access, value);
  } else {
    return _barrier_set->atomic_add_at(access, value);
  }
}

void LIRGenerator::do_LoadField(LoadField* x) {
  bool needs_patching = x->needs_patching();
  bool is_volatile = x->field()->is_volatile();
  BasicType field_type = x->field_type();

  CodeEmitInfo* info = NULL;
  if (needs_patching) {
    assert(x->explicit_null_check() == NULL, "can't fold null check into patching field access");
    info = state_for(x, x->state_before());
  } else if (x->needs_null_check()) {
    NullCheck* nc = x->explicit_null_check();
    if (nc == NULL) {
      info = state_for(x);
    } else {
      info = state_for(nc);
    }
  }

  LIRItem object(x->obj(), this);

  object.load_item();

#ifndef PRODUCT
  if (PrintNotLoaded && needs_patching) {
    tty->print_cr(" ###class not loaded at load_%s bci %d",
                  x->is_static() ?  "static" : "field", x->printable_bci());
  }
#endif

  bool stress_deopt = StressLoopInvariantCodeMotion && info && info->deoptimize_on_exception();
  if (x->needs_null_check() &&
      (needs_patching ||
       MacroAssembler::needs_explicit_null_check(x->offset()) ||
       stress_deopt)) {
    LIR_Opr obj = object.result();
    if (stress_deopt) {
      obj = new_register(T_OBJECT);
      __ move(LIR_OprFact::oopConst(NULL), obj);
    }
    // Emit an explicit null check because the offset is too large.
    // If the class is not loaded and the object is NULL, we need to deoptimize to throw a
    // NoClassDefFoundError in the interpreter instead of an implicit NPE from compiled code.
    __ null_check(obj, new CodeEmitInfo(info), /* deoptimize */ needs_patching);
  }

  DecoratorSet decorators = IN_HEAP;
  if (is_volatile) {
    decorators |= MO_SEQ_CST;
  }
  if (needs_patching) {
    decorators |= C1_NEEDS_PATCHING;
  }

  LIR_Opr result = rlock_result(x, field_type);
  access_load_at(decorators, field_type,
                 object, LIR_OprFact::intConst(x->offset()), result,
                 info ? new CodeEmitInfo(info) : NULL, info);
}

// int/long jdk.internal.util.Preconditions.checkIndex
--> --------------------

--> maximum size reached

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

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