shared/c2/barrierSetC2.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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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#ifndef SHARE_GC_SHARED_C2_BARRIERSETC2_HPP
#define SHARE_GC_SHARED_C2_BARRIERSETC2_HPP

#include "memory/allocation.hpp"
#include "oops/accessDecorators.hpp"
#include "opto/loopnode.hpp"
#include "opto/memnode.hpp"
#include "utilities/globalDefinitions.hpp"

// This means the access is mismatched. This means the value of an access
// is not equivalent to the value pointed to by the address.
const DecoratorSet C2_MISMATCHED             = DECORATOR_LAST << 1;
// The access may not be aligned to its natural size.
const DecoratorSet C2_UNALIGNED              = DECORATOR_LAST << 2;
// The atomic cmpxchg is weak, meaning that spurious false negatives are allowed,
// but never false positives.
const DecoratorSet C2_WEAK_CMPXCHG           = DECORATOR_LAST << 3;
// This denotes that a load has control dependency.
const DecoratorSet C2_CONTROL_DEPENDENT_LOAD = DECORATOR_LAST << 4;
// This denotes that a load that must be pinned.
const DecoratorSet C2_PINNED_LOAD            = DECORATOR_LAST << 5;
// This denotes that the access is produced from the sun.misc.Unsafe intrinsics.
const DecoratorSet C2_UNSAFE_ACCESS          = DECORATOR_LAST << 6;
// This denotes that the access mutates state.
const DecoratorSet C2_WRITE_ACCESS           = DECORATOR_LAST << 7;
// This denotes that the access reads state.
const DecoratorSet C2_READ_ACCESS            = DECORATOR_LAST << 8;

class GraphKit;
class IdealKit;
class Node;
class Type;
class TypePtr;
class PhaseMacroExpand;

// This class wraps a node and a type.
class C2AccessValue: public StackObj {
protected:
  Node* _node;
  const Type* _type;

public:
  C2AccessValue(Node* node, const Type* type) :
    _node(node),
    _type(type) {}

  Node* node() const        { return _node; }
  const Type* type() const  { return _type; }

  void set_node(Node* node) { _node = node; }
};

// This class wraps a node and a pointer type.
class C2AccessValuePtr: public C2AccessValue {
  int _alias_idx;

public:
  C2AccessValuePtr(Node* node, const TypePtr* type) :
    C2AccessValue(node, reinterpret_cast<const Type*>(type)) {}

  const TypePtr* type() const { return reinterpret_cast<const TypePtr*>(_type); }
  int alias_idx() const       { return _alias_idx; }
};

// This class wraps a bunch of context parameters thare are passed around in the
// BarrierSetC2 backend hierarchy, for loads and stores, to reduce boiler plate.
class C2Access: public StackObj {
protected:
  GraphKit*         _kit;
  DecoratorSet      _decorators;
  BasicType         _type;
  Node*             _base;
  C2AccessValuePtr& _addr;
  Node*             _raw_access;

  void fixup_decorators();
  void* barrier_set_state() const;

public:
  C2Access(GraphKit* kit, DecoratorSet decorators,
           BasicType type, Node* base, C2AccessValuePtr& addr) :
    _kit(kit),
    _decorators(decorators),
    _type(type),
    _base(base),
    _addr(addr),
    _raw_access(NULL)
  {
    fixup_decorators();
  }

  GraphKit* kit() const           { return _kit; }
  DecoratorSet decorators() const { return _decorators; }
  Node* base() const              { return _base; }
  C2AccessValuePtr& addr() const  { return _addr; }
  BasicType type() const          { return _type; }
  bool is_oop() const             { return _type == T_OBJECT || _type == T_ARRAY; }
  bool is_raw() const             { return (_decorators & AS_RAW) != 0; }
  Node* raw_access() const        { return _raw_access; }

  void set_raw_access(Node* raw_access) { _raw_access = raw_access; }
  virtual void set_memory() {} // no-op for normal accesses, but not for atomic accesses.

  MemNode::MemOrd mem_node_mo() const;
  bool needs_cpu_membar() const;

  template <typename T>
  T barrier_set_state_as() const {
    return reinterpret_cast<T>(barrier_set_state());
  }
};

// This class wraps a bunch of context parameters thare are passed around in the
// BarrierSetC2 backend hierarchy, for atomic accesses, to reduce boiler plate.
class C2AtomicAccess: public C2Access {
  Node* _memory;
  uint  _alias_idx;
  bool  _needs_pinning;

public:
  C2AtomicAccess(GraphKit* kit, DecoratorSet decorators, BasicType type,
                 Node* base, C2AccessValuePtr& addr, uint alias_idx) :
    C2Access(kit, decorators, type, base, addr),
    _memory(NULL),
    _alias_idx(alias_idx),
    _needs_pinning(true) {}

  // Set the memory node based on the current memory slice.
  virtual void set_memory();

  Node* memory() const       { return _memory; }
  uint alias_idx() const     { return _alias_idx; }
  bool needs_pinning() const { return _needs_pinning; }

  void set_needs_pinning(bool value)    { _needs_pinning = value; }
};

// This is the top-level class for the backend of the Access API in C2.
// The top-level class is responsible for performing raw accesses. The
// various GC barrier sets inherit from the BarrierSetC2 class to sprinkle
// barriers into the accesses.
class BarrierSetC2: public CHeapObj<mtGC> {
protected:
  virtual void resolve_address(C2Access& access) const;
  virtual Node* store_at_resolved(C2Access& access, C2AccessValue& val) const;
  virtual Node* load_at_resolved(C2Access& access, const Type* val_type) const;

  virtual Node* atomic_cmpxchg_val_at_resolved(C2AtomicAccess& access, Node* expected_val,
                                               Node* new_val, const Type* val_type) const;
  virtual Node* atomic_cmpxchg_bool_at_resolved(C2AtomicAccess& access, Node* expected_val,
                                                Node* new_val, const Type* value_type) const;
  virtual Node* atomic_xchg_at_resolved(C2AtomicAccess& access, Node* new_val, const Type* val_type) const;
  virtual Node* atomic_add_at_resolved(C2AtomicAccess& access, Node* new_val, const Type* val_type) const;

public:
  // This is the entry-point for the backend to perform accesses through the Access API.
  virtual Node* store_at(C2Access& access, C2AccessValue& val) const;
  virtual Node* load_at(C2Access& access, const Type* val_type) const;

  virtual Node* atomic_cmpxchg_val_at(C2AtomicAccess& access, Node* expected_val,
                                      Node* new_val, const Type* val_type) const;
  virtual Node* atomic_cmpxchg_bool_at(C2AtomicAccess& access, Node* expected_val,
                                       Node* new_val, const Type* val_type) const;
  virtual Node* atomic_xchg_at(C2AtomicAccess& access, Node* new_val, const Type* value_type) const;
  virtual Node* atomic_add_at(C2AtomicAccess& access, Node* new_val, const Type* value_type) const;

  virtual void clone(GraphKit* kit, Node* src, Node* dst, Node* size, bool is_array) const;

  virtual Node* ideal_node(PhaseGVN* phase, Node* n, bool can_reshape) const { return NULL; }
  virtual Node* identity_node(PhaseGVN* phase, Node* n) const { return n; }

  // These are general helper methods used by C2
  virtual bool array_copy_requires_gc_barriers(BasicType type) const { return false; }
  virtual void clone_at_expansion(PhaseMacroExpand* phase, ArrayCopyNode* ac) const;

  // Support for GC barriers emitted during parsing
  virtual bool has_load_barriers() const { return false; }
  virtual bool is_gc_barrier_node(Node* node) const { return false; }
  virtual Node* step_over_gc_barrier(Node* c) const { return c; }

  // Support for macro expanded GC barriers
  virtual void register_potential_barrier_node(Node* node) const { }
  virtual void unregister_potential_barrier_node(Node* node) const { }
  virtual void eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const { }
  virtual void enqueue_useful_gc_barrier(Unique_Node_List &worklist, Node* node) const {}
  virtual void eliminate_useless_gc_barriers(Unique_Node_List &useful) const {}
  virtual void add_users_to_worklist(Unique_Node_List* worklist) const {}

  // Allow barrier sets to have shared state that is preserved across a compilation unit.
  // This could for example comprise macro nodes to be expanded during macro expansion.
  virtual void* create_barrier_state(Arena* comp_arena) const { return NULL; }
  // If the BarrierSetC2 state has kept macro nodes in its compilation unit state to be
  // expanded later, then now is the time to do so.
  virtual bool expand_macro_nodes(PhaseMacroExpand* macro) const { return false; }
  virtual void verify_gc_barriers(bool post_parse) const {}
};

#endif // SHARE_GC_SHARED_C2_BARRIERSETC2_HPP