locknode.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * 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.
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#include "opto/locknode.hpp"
#include "opto/parse.hpp"
#include "opto/rootnode.hpp"
#include "opto/runtime.hpp"

//=============================================================================
const RegMask &BoxLockNode::in_RegMask(uint i) const {
  return _inmask;
}

const RegMask &BoxLockNode::out_RegMask() const {
  return *Matcher::idealreg2regmask[Op_RegP];
}

uint BoxLockNode::size_of() const { return sizeof(*this); }

BoxLockNode::BoxLockNode( int slot ) : Node( Compile::current()->root() ),
                                       _slot(slot), _kind(BoxLockNode::Regular) {
  init_class_id(Class_BoxLock);
  init_flags(Flag_rematerialize);
  OptoReg::Name reg = OptoReg::stack2reg(_slot);
  if (!RegMask::can_represent(reg, Compile::current()->sync_stack_slots())) {
    Compile::current()->record_method_not_compilable("must be able to represent all monitor slots in reg mask");
    return;
  }
  _inmask.Insert(reg);
}

uint BoxLockNode::hash() const {
  if (EliminateNestedLocks) {
    return NO_HASH; // Each locked region has own BoxLock node
  }
  return Node::hash() + _slot + (is_eliminated() ? Compile::current()->fixed_slots() : 0);
}

bool BoxLockNode::cmp( const Node &n ) const {
  if (EliminateNestedLocks) {
    return (&n == this); // Always fail except on self
  }
  const BoxLockNode &bn = (const BoxLockNode &)n;
  return (bn._slot == _slot) && (bn.is_eliminated() == is_eliminated());
}

Node* BoxLockNode::Identity(PhaseGVN* phase) {
  if (!EliminateNestedLocks && !this->is_eliminated()) {
    Node* n = phase->hash_find(this);
    if (n == nullptr || n == this) {
      return this;
    }
    BoxLockNode* old_box = n->as_BoxLock();
    // Set corresponding status (_kind) when commoning BoxLock nodes.
    if (this->_kind != old_box->_kind) {
      if (this->is_unbalanced()) {
        old_box->set_unbalanced();
      }
      if (!old_box->is_unbalanced()) {
        // Only Regular or Coarsened status should be here:
        // Nested and Local are set only when EliminateNestedLocks is on.
        if (old_box->is_regular()) {
          assert(this->is_coarsened(),"unexpected kind: %s", _kind_name[(int)this->_kind]);
          old_box->set_coarsened();
        } else {
          assert(this->is_regular(),"unexpected kind: %s", _kind_name[(int)this->_kind]);
          assert(old_box->is_coarsened(),"unexpected kind: %s", _kind_name[(int)old_box->_kind]);
        }
      }
    }
    return old_box;
  }
  return this;
}

BoxLockNode* BoxLockNode::box_node(Node* box) {
  // Chase down the BoxNode after RA which may spill box nodes.
  while (!box->is_BoxLock()) {
    //    if (box_node->is_SpillCopy()) {
    //      Node *m = box_node->in(1);
    //      if (m->is_Mach() && m->as_Mach()->ideal_Opcode() == Op_StoreP) {
    //        box_node = m->in(m->as_Mach()->operand_index(2));
    //        continue;
    //      }
    //    }
    assert(box->is_SpillCopy() || box->is_Phi(), "Bad spill of Lock.");
    // Only BoxLock nodes with the same stack slot are merged.
    // So it is enough to trace one path to find the slot value.
    box = box->in(1);
  }
  return box->as_BoxLock();
}

OptoReg::Name BoxLockNode::reg(Node* box) {
  return box_node(box)->in_RegMask(0).find_first_elem();
}

// Is BoxLock node used for one simple lock region (same box and obj)?
bool BoxLockNode::is_simple_lock_region(LockNode** unique_lock, Node* obj, Node** bad_lock) {
  if (is_unbalanced()) {
    return false;
  }
  LockNode* lock = nullptr;
  bool has_one_lock = false;
  for (uint i = 0; i < this->outcnt(); i++) {
    Node* n = this->raw_out(i);
    assert(!n->is_Phi(), "should not merge BoxLock nodes");
    if (n->is_AbstractLock()) {
      AbstractLockNode* alock = n->as_AbstractLock();
      // Check lock's box since box could be referenced by Lock's debug info.
      if (alock->box_node() == this) {
        if (alock->obj_node()->eqv_uncast(obj)) {
          if ((unique_lock != nullptr) && alock->is_Lock()) {
            if (lock == nullptr) {
              lock = alock->as_Lock();
              has_one_lock = true;
            } else if (lock != alock->as_Lock()) {
              has_one_lock = false;
              if (bad_lock != nullptr) {
                *bad_lock = alock;
              }
            }
          }
        } else {
          if (bad_lock != nullptr) {
            *bad_lock = alock;
          }
          return false; // Different objects
        }
      }
    }
  }
#ifdef ASSERT
  // Verify that FastLock and Safepoint reference only this lock region.
  for (uint i = 0; i < this->outcnt(); i++) {
    Node* n = this->raw_out(i);
    if (n->is_FastLock()) {
      FastLockNode* flock = n->as_FastLock();
      assert((flock->box_node() == this) && flock->obj_node()->eqv_uncast(obj),"");
    }
    // Don't check monitor info in safepoints since the referenced object could
    // be different from the locked object. It could be Phi node of different
    // cast nodes which point to this locked object.
    // We assume that no other objects could be referenced in monitor info
    // associated with this BoxLock node because all associated locks and
    // unlocks are reference only this one object.
  }
#endif
  if (unique_lock != nullptr && has_one_lock) {
    *unique_lock = lock;
  }
  return true;
}

//=============================================================================
//-----------------------------hash--------------------------------------------
uint FastLockNode::hash() const { return NO_HASH; }

uint FastLockNode::size_of() const { return sizeof(*this); }

//------------------------------cmp--------------------------------------------
bool FastLockNode::cmp( const Node &n ) const {
  return (&n == this);                // Always fail except on self
}

//=============================================================================
//-----------------------------hash--------------------------------------------
uint FastUnlockNode::hash() const { return NO_HASH; }

//------------------------------cmp--------------------------------------------
bool FastUnlockNode::cmp( const Node &n ) const {
  return (&n == this);                // Always fail except on self
}

//=============================================================================
//------------------------------do_monitor_enter-------------------------------
void Parse::do_monitor_enter() {
  kill_dead_locals();

  // Null check; get casted pointer.
  Node* obj = null_check(peek());
  // Check for locking null object
  if (stopped()) return;

  // the monitor object is not part of debug info expression stack
  pop();

  // Insert a FastLockNode which takes as arguments the current thread pointer,
  // the obj pointer & the address of the stack slot pair used for the lock.
  shared_lock(obj);
}

//------------------------------do_monitor_exit--------------------------------
void Parse::do_monitor_exit() {
  kill_dead_locals();

  pop();                        // Pop oop to unlock
  // Because monitors are guaranteed paired (else we bail out), we know
  // the matching Lock for this Unlock.  Hence we know there is no need
  // for a null check on Unlock.
  shared_unlock(map()->peek_monitor_box(), map()->peek_monitor_obj());
}