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 /*

  * Copyright (c) 2005, 2016, 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

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 #ifndef SHARE_VM_C1_C1_LIRGENERATOR_HPP

 #define SHARE_VM_C1_C1_LIRGENERATOR_HPP

 #include "c1/c1_Instruction.hpp"

 #include "c1/c1_LIR.hpp"

 #include "ci/ciMethodData.hpp"

 #include "jfr/support/jfrIntrinsics.hpp"

 #include "utilities/sizes.hpp"

 // The classes responsible for code emission and register allocation

 class LIRGenerator;

 class LIREmitter;

 class Invoke;

 class SwitchRange;

 class LIRItem;

 define_array(LIRItemArray, LIRItem*)

 define_stack(LIRItemList, LIRItemArray)

 class SwitchRange: public CompilationResourceObj {

  private:

   int _low_key;

   int _high_key;

   BlockBegin* _sux;

  public:

   SwitchRange(int start_key, BlockBegin* sux): _low_key(start_key), _high_key(start_key), _sux(sux) {}

   void set_high_key(int key) { _high_key = key; }

   int high_key() const { return _high_key; }

   int low_key() const { return _low_key; }

   BlockBegin* sux() const { return _sux; }

 };

 define_array(SwitchRangeArray, SwitchRange*)

 define_stack(SwitchRangeList, SwitchRangeArray)

 class ResolveNode;

 define_array(NodeArray, ResolveNode*);

 define_stack(NodeList, NodeArray);

 // Node objects form a directed graph of LIR_Opr

 // Edges between Nodes represent moves from one Node to its destinations

 class ResolveNode: public CompilationResourceObj {

  private:

   LIR_Opr    _operand;       // the source or destinaton

   NodeList   _destinations;  // for the operand

   bool       _assigned;      // Value assigned to this Node?

   bool       _visited;       // Node already visited?

   bool       _start_node;    // Start node already visited?

  public:

   ResolveNode(LIR_Opr operand)

     : _operand(operand)

     , _assigned(false)

     , _visited(false)

     , _start_node(false) {};

   // accessors

   LIR_Opr operand() const           { return _operand; }

   int no_of_destinations() const    { return _destinations.length(); }

   ResolveNode* destination_at(int i)     { return _destinations[i]; }

   bool assigned() const             { return _assigned; }

   bool visited() const              { return _visited; }

   bool start_node() const           { return _start_node; }

   // modifiers

   void append(ResolveNode* dest)         { _destinations.append(dest); }

   void set_assigned()               { _assigned = true; }

   void set_visited()                { _visited = true; }

   void set_start_node()             { _start_node = true; }

 };

 // This is shared state to be used by the PhiResolver so the operand

 // arrays don't have to be reallocated for reach resolution.

 class PhiResolverState: public CompilationResourceObj {

   friend class PhiResolver;

  private:

   NodeList _virtual_operands; // Nodes where the operand is a virtual register

   NodeList _other_operands;   // Nodes where the operand is not a virtual register

   NodeList _vreg_table;       // Mapping from virtual register to Node

  public:

   PhiResolverState() {}

   void reset(int max_vregs);

 };

 // class used to move value of phi operand to phi function

 class PhiResolver: public CompilationResourceObj {

  private:

   LIRGenerator*     _gen;

   PhiResolverState& _state; // temporary state cached by LIRGenerator

   ResolveNode*   _loop;

   LIR_Opr _temp;

   // access to shared state arrays

   NodeList& virtual_operands() { return _state._virtual_operands; }

   NodeList& other_operands()   { return _state._other_operands;   }

   NodeList& vreg_table()       { return _state._vreg_table;       }

   ResolveNode* create_node(LIR_Opr opr, bool source);

   ResolveNode* source_node(LIR_Opr opr)      { return create_node(opr, true); }

   ResolveNode* destination_node(LIR_Opr opr) { return create_node(opr, false); }

   void emit_move(LIR_Opr src, LIR_Opr dest);

   void move_to_temp(LIR_Opr src);

   void move_temp_to(LIR_Opr dest);

   void move(ResolveNode* src, ResolveNode* dest);

   LIRGenerator* gen() {

     return _gen;

   }

  public:

   PhiResolver(LIRGenerator* _lir_gen, int max_vregs);

   ~PhiResolver();

   void move(LIR_Opr src, LIR_Opr dest);

 };

 // only the classes below belong in the same file

 class LIRGenerator: public InstructionVisitor, public BlockClosure {

  private:

   Compilation*  _compilation;

   ciMethod*     _method;    // method that we are compiling

   PhiResolverState  _resolver_state;

   BlockBegin*   _block;

   int           _virtual_register_number;

   Values        _instruction_for_operand;

   BitMap2D      _vreg_flags; // flags which can be set on a per-vreg basis

   LIR_List*     _lir;

   BarrierSet*   _bs;

   LIRGenerator* gen() {

     return this;

   }

   void print_if_not_loaded(const NewInstance* new_instance) PRODUCT_RETURN;

 #ifdef ASSERT

   LIR_List* lir(const char * file, int line) const {

     _lir->set_file_and_line(file, line);

     return _lir;

   }

 #endif

   LIR_List* lir() const {

     return _lir;

   }

   // a simple cache of constants used within a block

   GrowableArray<LIR_Const*>       _constants;

   LIR_OprList                     _reg_for_constants;

   Values                          _unpinned_constants;

   friend class PhiResolver;

   // unified bailout support

   void bailout(const char* msg) const            { compilation()->bailout(msg); }

   bool bailed_out() const                        { return compilation()->bailed_out(); }

   void block_do_prolog(BlockBegin* block);

   void block_do_epilog(BlockBegin* block);

   // register allocation

   LIR_Opr rlock(Value instr);                      // lock a free register

   LIR_Opr rlock_result(Value instr);

   LIR_Opr rlock_result(Value instr, BasicType type);

   LIR_Opr rlock_byte(BasicType type);

   LIR_Opr rlock_callee_saved(BasicType type);

   // get a constant into a register and get track of what register was used

   LIR_Opr load_constant(Constant* x);

   LIR_Opr load_constant(LIR_Const* constant);

   // Given an immediate value, return an operand usable in logical ops.

   LIR_Opr load_immediate(int x, BasicType type);

   void  set_result(Value x, LIR_Opr opr)           {

     assert(opr->is_valid(), "must set to valid value");

     assert(x->operand()->is_illegal(), "operand should never change");

     assert(!opr->is_register() || opr->is_virtual(), "should never set result to a physical register");

     x->set_operand(opr);

     assert(opr == x->operand(), "must be");

     if (opr->is_virtual()) {

       _instruction_for_operand.at_put_grow(opr->vreg_number(), x, NULL);

     }

   }

   void  set_no_result(Value x)                     { assert(!x->has_uses(), "can't have use"); x->clear_operand(); }

   friend class LIRItem;

   LIR_Opr round_item(LIR_Opr opr);

   LIR_Opr force_to_spill(LIR_Opr value, BasicType t);

   PhiResolverState& resolver_state() { return _resolver_state; }

   void  move_to_phi(PhiResolver* resolver, Value cur_val, Value sux_val);

   void  move_to_phi(ValueStack* cur_state);

   // code emission

   void do_ArithmeticOp_Long   (ArithmeticOp*    x);

   void do_ArithmeticOp_Int    (ArithmeticOp*    x);

   void do_ArithmeticOp_FPU    (ArithmeticOp*    x);

   // platform dependent

   LIR_Opr getThreadPointer();

   void do_RegisterFinalizer(Intrinsic* x);

   void do_isInstance(Intrinsic* x);

   void do_getClass(Intrinsic* x);

   void do_currentThread(Intrinsic* x);

   void do_MathIntrinsic(Intrinsic* x);

   void do_ArrayCopy(Intrinsic* x);

   void do_CompareAndSwap(Intrinsic* x, ValueType* type);

   void do_NIOCheckIndex(Intrinsic* x);

   void do_FPIntrinsics(Intrinsic* x);

   void do_Reference_get(Intrinsic* x);

   void do_update_CRC32(Intrinsic* x);

   void do_UnsafePrefetch(UnsafePrefetch* x, bool is_store);

   LIR_Opr call_runtime(BasicTypeArray* signature, LIRItemList* args, address entry, ValueType* result_type, CodeEmitInfo* info);

   LIR_Opr call_runtime(BasicTypeArray* signature, LIR_OprList* args, address entry, ValueType* result_type, CodeEmitInfo* info);

   // convenience functions

   LIR_Opr call_runtime(Value arg1, address entry, ValueType* result_type, CodeEmitInfo* info);

   LIR_Opr call_runtime(Value arg1, Value arg2, address entry, ValueType* result_type, CodeEmitInfo* info);

   // GC Barriers

   // generic interface

   void pre_barrier(LIR_Opr addr_opr, LIR_Opr pre_val, bool do_load, bool patch, CodeEmitInfo* info);

   void post_barrier(LIR_OprDesc* addr, LIR_OprDesc* new_val);

   // specific implementations

   // pre barriers

   void G1SATBCardTableModRef_pre_barrier(LIR_Opr addr_opr, LIR_Opr pre_val,

                                          bool do_load, bool patch, CodeEmitInfo* info);

   // post barriers

   void G1SATBCardTableModRef_post_barrier(LIR_OprDesc* addr, LIR_OprDesc* new_val);

   void CardTableModRef_post_barrier(LIR_OprDesc* addr, LIR_OprDesc* new_val);

 #ifdef CARDTABLEMODREF_POST_BARRIER_HELPER

   void CardTableModRef_post_barrier_helper(LIR_OprDesc* addr, LIR_Const* card_table_base);

 #endif

   static LIR_Opr result_register_for(ValueType* type, bool callee = false);

   ciObject* get_jobject_constant(Value value);

   LIRItemList* invoke_visit_arguments(Invoke* x);

   void invoke_load_arguments(Invoke* x, LIRItemList* args, const LIR_OprList* arg_list);

   void trace_block_entry(BlockBegin* block);

   // volatile field operations are never patchable because a klass

   // must be loaded to know it's volatile which means that the offset

   // it always known as well.

   void volatile_field_store(LIR_Opr value, LIR_Address* address, CodeEmitInfo* info);

   void volatile_field_load(LIR_Address* address, LIR_Opr result, CodeEmitInfo* info);

   void put_Object_unsafe(LIR_Opr src, LIR_Opr offset, LIR_Opr data, BasicType type, bool is_volatile);

   void get_Object_unsafe(LIR_Opr dest, LIR_Opr src, LIR_Opr offset, BasicType type, bool is_volatile);

   void arithmetic_call_op (Bytecodes::Code code, LIR_Opr result, LIR_OprList* args);

   void increment_counter(address counter, BasicType type, int step = 1);

   void increment_counter(LIR_Address* addr, int step = 1);

   // is_strictfp is only needed for mul and div (and only generates different code on i486)

   void arithmetic_op(Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, bool is_strictfp, LIR_Opr tmp, CodeEmitInfo* info = NULL);

   // machine dependent.  returns true if it emitted code for the multiply

   bool strength_reduce_multiply(LIR_Opr left, int constant, LIR_Opr result, LIR_Opr tmp);

   void store_stack_parameter (LIR_Opr opr, ByteSize offset_from_sp_in_bytes);

   void klass2reg_with_patching(LIR_Opr r, ciMetadata* obj, CodeEmitInfo* info, bool need_resolve = false);

   // this loads the length and compares against the index

   void array_range_check          (LIR_Opr array, LIR_Opr index, CodeEmitInfo* null_check_info, CodeEmitInfo* range_check_info);

   // For java.nio.Buffer.checkIndex

   void nio_range_check            (LIR_Opr buffer, LIR_Opr index, LIR_Opr result, CodeEmitInfo* info);

   void arithmetic_op_int  (Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, LIR_Opr tmp);

   void arithmetic_op_long (Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, CodeEmitInfo* info = NULL);

   void arithmetic_op_fpu  (Bytecodes::Code code, LIR_Opr result, LIR_Opr left, LIR_Opr right, bool is_strictfp, LIR_Opr tmp = LIR_OprFact::illegalOpr);

   void shift_op   (Bytecodes::Code code, LIR_Opr dst_reg, LIR_Opr value, LIR_Opr count, LIR_Opr tmp);

   void logic_op   (Bytecodes::Code code, LIR_Opr dst_reg, LIR_Opr left, LIR_Opr right);

   void monitor_enter (LIR_Opr object, LIR_Opr lock, LIR_Opr hdr, LIR_Opr scratch, int monitor_no, CodeEmitInfo* info_for_exception, CodeEmitInfo* info);

   void monitor_exit  (LIR_Opr object, LIR_Opr lock, LIR_Opr hdr, LIR_Opr scratch, int monitor_no);

   void 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);

   // machine dependent

   void cmp_mem_int(LIR_Condition condition, LIR_Opr base, int disp, int c, CodeEmitInfo* info);

   void cmp_reg_mem(LIR_Condition condition, LIR_Opr reg, LIR_Opr base, int disp, BasicType type, CodeEmitInfo* info);

   void cmp_reg_mem(LIR_Condition condition, LIR_Opr reg, LIR_Opr base, LIR_Opr disp, BasicType type, CodeEmitInfo* info);

   void arraycopy_helper(Intrinsic* x, int* flags, ciArrayKlass** expected_type);

   // returns a LIR_Address to address an array location.  May also

   // emit some code as part of address calculation.  If

   // needs_card_mark is true then compute the full address for use by

   // both the store and the card mark.

   LIR_Address* generate_address(LIR_Opr base,

                                 LIR_Opr index, int shift,

                                 int disp,

                                 BasicType type);

   LIR_Address* generate_address(LIR_Opr base, int disp, BasicType type) {

     return generate_address(base, LIR_OprFact::illegalOpr, 0, disp, type);

   }

   LIR_Address* emit_array_address(LIR_Opr array_opr, LIR_Opr index_opr, BasicType type, bool needs_card_mark);

   // the helper for generate_address

   void add_large_constant(LIR_Opr src, int c, LIR_Opr dest);

   // machine preferences and characteristics

   bool can_inline_as_constant(Value i) const;

   bool can_inline_as_constant(LIR_Const* c) const;

   bool can_store_as_constant(Value i, BasicType type) const;

   LIR_Opr safepoint_poll_register();

   void profile_branch(If* if_instr, If::Condition cond);

   void increment_event_counter_impl(CodeEmitInfo* info,

                                     ciMethod *method, int frequency,

                                     int bci, bool backedge, bool notify);

   void increment_event_counter(CodeEmitInfo* info, int bci, bool backedge);

   void increment_invocation_counter(CodeEmitInfo *info) {

     if (compilation()->count_invocations()) {

       increment_event_counter(info, InvocationEntryBci, false);

     }

   }

   void increment_backedge_counter(CodeEmitInfo* info, int bci) {

     if (compilation()->count_backedges()) {

       increment_event_counter(info, bci, true);

     }

   }

   CodeEmitInfo* state_for(Instruction* x, ValueStack* state, bool ignore_xhandler = false);

   CodeEmitInfo* state_for(Instruction* x);

   // allocates a virtual register for this instruction if

   // one isn't already allocated.  Only for Phi and Local.

   LIR_Opr operand_for_instruction(Instruction *x);

   void set_block(BlockBegin* block)              { _block = block; }

   void block_prolog(BlockBegin* block);

   void block_epilog(BlockBegin* block);

   void do_root (Instruction* instr);

   void walk    (Instruction* instr);

   void bind_block_entry(BlockBegin* block);

   void start_block(BlockBegin* block);

   LIR_Opr new_register(BasicType type);

   LIR_Opr new_register(Value value)              { return new_register(as_BasicType(value->type())); }

   LIR_Opr new_register(ValueType* type)          { return new_register(as_BasicType(type)); }

   // returns a register suitable for doing pointer math

   LIR_Opr new_pointer_register() {

 #ifdef _LP64

     return new_register(T_LONG);

 #else

     return new_register(T_INT);

 #endif

   }

   static LIR_Condition lir_cond(If::Condition cond) {

     LIR_Condition l = lir_cond_unknown;

     switch (cond) {

     case If::eql: l = lir_cond_equal;        break;

     case If::neq: l = lir_cond_notEqual;     break;

     case If::lss: l = lir_cond_less;         break;

     case If::leq: l = lir_cond_lessEqual;    break;

     case If::geq: l = lir_cond_greaterEqual; break;

     case If::gtr: l = lir_cond_greater;      break;

     case If::aeq: l = lir_cond_aboveEqual;   break;

     case If::beq: l = lir_cond_belowEqual;   break;

     default: fatal("You must pass valid If::Condition");

     };

     return l;

   }

 #ifdef __SOFTFP__

   void do_soft_float_compare(If *x);

 #endif // __SOFTFP__

   void init();

   SwitchRangeArray* create_lookup_ranges(TableSwitch* x);

   SwitchRangeArray* create_lookup_ranges(LookupSwitch* x);

   void do_SwitchRanges(SwitchRangeArray* x, LIR_Opr value, BlockBegin* default_sux);

   void do_RuntimeCall(address routine, int expected_arguments, Intrinsic* x);

 #ifdef JFR_HAVE_INTRINSICS

   void do_ClassIDIntrinsic(Intrinsic* x);

   void do_getEventWriter(Intrinsic* x);

 #endif

   ciKlass* profile_type(ciMethodData* md, int md_first_offset, int md_offset, intptr_t profiled_k,

                         Value arg, LIR_Opr& mdp, bool not_null, ciKlass* signature_at_call_k,

                         ciKlass* callee_signature_k);

   void profile_arguments(ProfileCall* x);

   void profile_parameters(Base* x);

   void profile_parameters_at_call(ProfileCall* x);

   LIR_Opr maybe_mask_boolean(StoreIndexed* x, LIR_Opr array, LIR_Opr value, CodeEmitInfo*& null_check_info);

  public:

   Compilation*  compilation() const              { return _compilation; }

   FrameMap*     frame_map() const                { return _compilation->frame_map(); }

   ciMethod*     method() const                   { return _method; }

   BlockBegin*   block() const                    { return _block; }

   IRScope*      scope() const                    { return block()->scope(); }

   int max_virtual_register_number() const        { return _virtual_register_number; }

   void block_do(BlockBegin* block);

   // Flags that can be set on vregs

   enum VregFlag {

       must_start_in_memory = 0  // needs to be assigned a memory location at beginning, but may then be loaded in a register

     , callee_saved     = 1    // must be in a callee saved register

     , byte_reg         = 2    // must be in a byte register

     , num_vreg_flags

   };

   LIRGenerator(Compilation* compilation, ciMethod* method)

     : _compilation(compilation)

     , _method(method)

     , _virtual_register_number(LIR_OprDesc::vreg_base)

     , _vreg_flags(NULL, 0, num_vreg_flags) {

     init();

   }

   // for virtual registers, maps them back to Phi's or Local's

   Instruction* instruction_for_opr(LIR_Opr opr);

   Instruction* instruction_for_vreg(int reg_num);

   void set_vreg_flag   (int vreg_num, VregFlag f);

   bool is_vreg_flag_set(int vreg_num, VregFlag f);

   void set_vreg_flag   (LIR_Opr opr,  VregFlag f) { set_vreg_flag(opr->vreg_number(), f); }

   bool is_vreg_flag_set(LIR_Opr opr,  VregFlag f) { return is_vreg_flag_set(opr->vreg_number(), f); }

   // statics

   static LIR_Opr exceptionOopOpr();

   static LIR_Opr exceptionPcOpr();

   static LIR_Opr divInOpr();

   static LIR_Opr divOutOpr();

   static LIR_Opr remOutOpr();

   static LIR_Opr shiftCountOpr();

   LIR_Opr syncTempOpr();

   LIR_Opr atomicLockOpr();

   // returns a register suitable for saving the thread in a

   // call_runtime_leaf if one is needed.

   LIR_Opr getThreadTemp();

   // visitor functionality

   virtual void do_Phi            (Phi*             x);

   virtual void do_Local          (Local*           x);

   virtual void do_Constant       (Constant*        x);

   virtual void do_LoadField      (LoadField*       x);

   virtual void do_StoreField     (StoreField*      x);

   virtual void do_ArrayLength    (ArrayLength*     x);

   virtual void do_LoadIndexed    (LoadIndexed*     x);

   virtual void do_StoreIndexed   (StoreIndexed*    x);

   virtual void do_NegateOp       (NegateOp*        x);

   virtual void do_ArithmeticOp   (ArithmeticOp*    x);

   virtual void do_ShiftOp        (ShiftOp*         x);

   virtual void do_LogicOp        (LogicOp*         x);

   virtual void do_CompareOp      (CompareOp*       x);

   virtual void do_IfOp           (IfOp*            x);

   virtual void do_Convert        (Convert*         x);

   virtual void do_NullCheck      (NullCheck*       x);

   virtual void do_TypeCast       (TypeCast*        x);

   virtual void do_Invoke         (Invoke*          x);

   virtual void do_NewInstance    (NewInstance*     x);

   virtual void do_NewTypeArray   (NewTypeArray*    x);

   virtual void do_NewObjectArray (NewObjectArray*  x);

   virtual void do_NewMultiArray  (NewMultiArray*   x);

   virtual void do_CheckCast      (CheckCast*       x);

   virtual void do_InstanceOf     (InstanceOf*      x);

   virtual void do_MonitorEnter   (MonitorEnter*    x);

   virtual void do_MonitorExit    (MonitorExit*     x);

   virtual void do_Intrinsic      (Intrinsic*       x);

   virtual void do_BlockBegin     (BlockBegin*      x);

   virtual void do_Goto           (Goto*            x);

   virtual void do_If             (If*              x);

   virtual void do_IfInstanceOf   (IfInstanceOf*    x);

   virtual void do_TableSwitch    (TableSwitch*     x);

   virtual void do_LookupSwitch   (LookupSwitch*    x);

   virtual void do_Return         (Return*          x);

   virtual void do_Throw          (Throw*           x);

   virtual void do_Base           (Base*            x);

   virtual void do_OsrEntry       (OsrEntry*        x);

   virtual void do_ExceptionObject(ExceptionObject* x);

   virtual void do_RoundFP        (RoundFP*         x);

   virtual void do_UnsafeGetRaw   (UnsafeGetRaw*    x);

   virtual void do_UnsafePutRaw   (UnsafePutRaw*    x);

   virtual void do_UnsafeGetObject(UnsafeGetObject* x);

   virtual void do_UnsafePutObject(UnsafePutObject* x);

   virtual void do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x);

   virtual void do_UnsafePrefetchRead (UnsafePrefetchRead*  x);

   virtual void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);

   virtual void do_ProfileCall    (ProfileCall*     x);

   virtual void do_ProfileReturnType (ProfileReturnType* x);

   virtual void do_ProfileInvoke  (ProfileInvoke*   x);

   virtual void do_RuntimeCall    (RuntimeCall*     x);

   virtual void do_MemBar         (MemBar*          x);

   virtual void do_RangeCheckPredicate(RangeCheckPredicate* x);

 #ifdef ASSERT

   virtual void do_Assert         (Assert*          x);

 #endif

 #ifdef C1_LIRGENERATOR_MD_HPP

 #include C1_LIRGENERATOR_MD_HPP

 #endif

 };

 class LIRItem: public CompilationResourceObj {

  private:

   Value         _value;

   LIRGenerator* _gen;

   LIR_Opr       _result;

   bool          _destroys_register;

   LIR_Opr       _new_result;

   LIRGenerator* gen() const { return _gen; }

  public:

   LIRItem(Value value, LIRGenerator* gen) {

     _destroys_register = false;

     _gen = gen;

     set_instruction(value);

   }

   LIRItem(LIRGenerator* gen) {

     _destroys_register = false;

     _gen = gen;

     _result = LIR_OprFact::illegalOpr;

     set_instruction(NULL);

   }

   void set_instruction(Value value) {

     _value = value;

     _result = LIR_OprFact::illegalOpr;

     if (_value != NULL) {

       _gen->walk(_value);

       _result = _value->operand();

     }

     _new_result = LIR_OprFact::illegalOpr;

   }

   Value value() const          { return _value;          }

   ValueType* type() const      { return value()->type(); }

   LIR_Opr result()             {

     assert(!_destroys_register || (!_result->is_register() || _result->is_virtual()),

            "shouldn't use set_destroys_register with physical regsiters");

     if (_destroys_register && _result->is_register()) {

       if (_new_result->is_illegal()) {

         _new_result = _gen->new_register(type());

         gen()->lir()->move(_result, _new_result);

       }

       return _new_result;

     } else {

       return _result;

     }

     return _result;

   }

   void set_result(LIR_Opr opr);

   void load_item();

   void load_byte_item();

   void load_nonconstant();

   // load any values which can't be expressed as part of a single store instruction

   void load_for_store(BasicType store_type);

   void load_item_force(LIR_Opr reg);

   void dont_load_item() {

     // do nothing

   }

   void set_destroys_register() {

     _destroys_register = true;

   }

   bool is_constant() const { return value()->as_Constant() != NULL; }

   bool is_stack()          { return result()->is_stack(); }

   bool is_register()       { return result()->is_register(); }

   ciObject* get_jobject_constant() const;

   jint      get_jint_constant() const;

   jlong     get_jlong_constant() const;

   jfloat    get_jfloat_constant() const;

   jdouble   get_jdouble_constant() const;

   jint      get_address_constant() const;

 };

 #endif // SHARE_VM_C1_C1_LIRGENERATOR_HPP