1 /*
   2  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_OPTO_CFGNODE_HPP
  26 #define SHARE_VM_OPTO_CFGNODE_HPP
  27 
  28 #include "opto/multnode.hpp"
  29 #include "opto/node.hpp"
  30 #include "opto/opcodes.hpp"
  31 #include "opto/type.hpp"
  32 
  33 // Portions of code courtesy of Clifford Click
  34 
  35 // Optimization - Graph Style
  36 
  37 class Matcher;
  38 class Node;
  39 class   RegionNode;
  40 class   TypeNode;
  41 class     PhiNode;
  42 class   GotoNode;
  43 class   MultiNode;
  44 class     MultiBranchNode;
  45 class       IfNode;
  46 class       PCTableNode;
  47 class         JumpNode;
  48 class         CatchNode;
  49 class       NeverBranchNode;
  50 class   ProjNode;
  51 class     CProjNode;
  52 class       IfTrueNode;
  53 class       IfFalseNode;
  54 class       CatchProjNode;
  55 class     JProjNode;
  56 class       JumpProjNode;
  57 class     SCMemProjNode;
  58 class PhaseIdealLoop;
  59 
  60 //------------------------------RegionNode-------------------------------------
  61 // The class of RegionNodes, which can be mapped to basic blocks in the
  62 // program.  Their inputs point to Control sources.  PhiNodes (described
  63 // below) have an input point to a RegionNode.  Merged data inputs to PhiNodes
  64 // correspond 1-to-1 with RegionNode inputs.  The zero input of a PhiNode is
  65 // the RegionNode, and the zero input of the RegionNode is itself.
  66 class RegionNode : public Node {
  67 public:
  68   // Node layout (parallels PhiNode):
  69   enum { Region,                // Generally points to self.
  70          Control                // Control arcs are [1..len)
  71   };
  72 
  73   RegionNode( uint required ) : Node(required) {
  74     init_class_id(Class_Region);
  75     init_req(0,this);
  76   }
  77 
  78   Node* is_copy() const {
  79     const Node* r = _in[Region];
  80     if (r == NULL)
  81       return nonnull_req();
  82     return NULL;  // not a copy!
  83   }
  84   PhiNode* has_phi() const;        // returns an arbitrary phi user, or NULL
  85   PhiNode* has_unique_phi() const; // returns the unique phi user, or NULL
  86   // Is this region node unreachable from root?
  87   bool is_unreachable_region(PhaseGVN *phase) const;
  88   virtual int Opcode() const;
  89   virtual bool pinned() const { return (const Node *)in(0) == this; }
  90   virtual bool  is_CFG   () const { return true; }
  91   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
  92   virtual bool depends_only_on_test() const { return false; }
  93   virtual const Type *bottom_type() const { return Type::CONTROL; }
  94   virtual const Type *Value( PhaseTransform *phase ) const;
  95   virtual Node *Identity( PhaseTransform *phase );
  96   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
  97   virtual const RegMask &out_RegMask() const;
  98   bool try_clean_mem_phi(PhaseGVN *phase);
  99 };
 100 
 101 //------------------------------JProjNode--------------------------------------
 102 // jump projection for node that produces multiple control-flow paths
 103 class JProjNode : public ProjNode {
 104  public:
 105   JProjNode( Node* ctrl, uint idx ) : ProjNode(ctrl,idx) {}
 106   virtual int Opcode() const;
 107   virtual bool  is_CFG() const { return true; }
 108   virtual uint  hash() const { return NO_HASH; }  // CFG nodes do not hash
 109   virtual const Node* is_block_proj() const { return in(0); }
 110   virtual const RegMask& out_RegMask() const;
 111   virtual uint  ideal_reg() const { return 0; }
 112 };
 113 
 114 //------------------------------PhiNode----------------------------------------
 115 // PhiNodes merge values from different Control paths.  Slot 0 points to the
 116 // controlling RegionNode.  Other slots map 1-for-1 with incoming control flow
 117 // paths to the RegionNode.  For speed reasons (to avoid another pass) we
 118 // can turn PhiNodes into copys in-place by NULL'ing out their RegionNode
 119 // input in slot 0.
 120 class PhiNode : public TypeNode {
 121   const TypePtr* const _adr_type; // non-null only for Type::MEMORY nodes.
 122   const int _inst_id;     // Instance id of the memory slice.
 123   const int _inst_index;  // Alias index of the instance memory slice.
 124   // Array elements references have the same alias_idx but different offset.
 125   const int _inst_offset; // Offset of the instance memory slice.
 126   // Size is bigger to hold the _adr_type field.
 127   virtual uint hash() const;    // Check the type
 128   virtual uint cmp( const Node &n ) const;
 129   virtual uint size_of() const { return sizeof(*this); }
 130 
 131   // Determine if CMoveNode::is_cmove_id can be used at this join point.
 132   Node* is_cmove_id(PhaseTransform* phase, int true_path);
 133 
 134 public:
 135   // Node layout (parallels RegionNode):
 136   enum { Region,                // Control input is the Phi's region.
 137          Input                  // Input values are [1..len)
 138   };
 139 
 140   PhiNode( Node *r, const Type *t, const TypePtr* at = NULL,
 141            const int iid = TypeOopPtr::InstanceTop,
 142            const int iidx = Compile::AliasIdxTop,
 143            const int ioffs = Type::OffsetTop )
 144     : TypeNode(t,r->req()),
 145       _adr_type(at),
 146       _inst_id(iid),
 147       _inst_index(iidx),
 148       _inst_offset(ioffs)
 149   {
 150     init_class_id(Class_Phi);
 151     init_req(0, r);
 152     verify_adr_type();
 153   }
 154   // create a new phi with in edges matching r and set (initially) to x
 155   static PhiNode* make( Node* r, Node* x );
 156   // extra type arguments override the new phi's bottom_type and adr_type
 157   static PhiNode* make( Node* r, Node* x, const Type *t, const TypePtr* at = NULL );
 158   // create a new phi with narrowed memory type
 159   PhiNode* slice_memory(const TypePtr* adr_type) const;
 160   PhiNode* split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const;
 161   // like make(r, x), but does not initialize the in edges to x
 162   static PhiNode* make_blank( Node* r, Node* x );
 163 
 164   // Accessors
 165   RegionNode* region() const { Node* r = in(Region); assert(!r || r->is_Region(), ""); return (RegionNode*)r; }
 166 
 167   Node* is_copy() const {
 168     // The node is a real phi if _in[0] is a Region node.
 169     DEBUG_ONLY(const Node* r = _in[Region];)
 170     assert(r != NULL && r->is_Region(), "Not valid control");
 171     return NULL;  // not a copy!
 172   }
 173 
 174   bool is_tripcount() const;
 175 
 176   // Determine a unique non-trivial input, if any.
 177   // Ignore casts if it helps.  Return NULL on failure.
 178   Node* unique_input(PhaseTransform *phase);
 179 
 180   // Check for a simple dead loop.
 181   enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
 182   LoopSafety simple_data_loop_check(Node *in) const;
 183   // Is it unsafe data loop? It becomes a dead loop if this phi node removed.
 184   bool is_unsafe_data_reference(Node *in) const;
 185   int  is_diamond_phi(bool check_control_only = false) const;
 186   virtual int Opcode() const;
 187   virtual bool pinned() const { return in(0) != 0; }
 188   virtual const TypePtr *adr_type() const { verify_adr_type(true); return _adr_type; }
 189 
 190   const int inst_id()     const { return _inst_id; }
 191   const int inst_index()  const { return _inst_index; }
 192   const int inst_offset() const { return _inst_offset; }
 193   bool is_same_inst_field(const Type* tp, int id, int index, int offset) {
 194     return type()->basic_type() == tp->basic_type() &&
 195            inst_id()     == id     &&
 196            inst_index()  == index  &&
 197            inst_offset() == offset &&
 198            type()->higher_equal(tp);
 199   }
 200 
 201   virtual const Type *Value( PhaseTransform *phase ) const;
 202   virtual Node *Identity( PhaseTransform *phase );
 203   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 204   virtual const RegMask &out_RegMask() const;
 205   virtual const RegMask &in_RegMask(uint) const;
 206 #ifndef PRODUCT
 207   virtual void dump_spec(outputStream *st) const;
 208 #endif
 209 #ifdef ASSERT
 210   void verify_adr_type(VectorSet& visited, const TypePtr* at) const;
 211   void verify_adr_type(bool recursive = false) const;
 212 #else //ASSERT
 213   void verify_adr_type(bool recursive = false) const {}
 214 #endif //ASSERT
 215 };
 216 
 217 //------------------------------GotoNode---------------------------------------
 218 // GotoNodes perform direct branches.
 219 class GotoNode : public Node {
 220 public:
 221   GotoNode( Node *control ) : Node(control) {}
 222   virtual int Opcode() const;
 223   virtual bool pinned() const { return true; }
 224   virtual bool  is_CFG() const { return true; }
 225   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
 226   virtual const Node *is_block_proj() const { return this; }
 227   virtual bool depends_only_on_test() const { return false; }
 228   virtual const Type *bottom_type() const { return Type::CONTROL; }
 229   virtual const Type *Value( PhaseTransform *phase ) const;
 230   virtual Node *Identity( PhaseTransform *phase );
 231   virtual const RegMask &out_RegMask() const;
 232 };
 233 
 234 //------------------------------CProjNode--------------------------------------
 235 // control projection for node that produces multiple control-flow paths
 236 class CProjNode : public ProjNode {
 237 public:
 238   CProjNode( Node *ctrl, uint idx ) : ProjNode(ctrl,idx) {}
 239   virtual int Opcode() const;
 240   virtual bool  is_CFG() const { return true; }
 241   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
 242   virtual const Node *is_block_proj() const { return in(0); }
 243   virtual const RegMask &out_RegMask() const;
 244   virtual uint ideal_reg() const { return 0; }
 245 };
 246 
 247 //---------------------------MultiBranchNode-----------------------------------
 248 // This class defines a MultiBranchNode, a MultiNode which yields multiple
 249 // control values. These are distinguished from other types of MultiNodes
 250 // which yield multiple values, but control is always and only projection #0.
 251 class MultiBranchNode : public MultiNode {
 252 public:
 253   MultiBranchNode( uint required ) : MultiNode(required) {
 254     init_class_id(Class_MultiBranch);
 255   }
 256   // returns required number of users to be well formed.
 257   virtual int required_outcnt() const = 0;
 258 };
 259 
 260 //------------------------------IfNode-----------------------------------------
 261 // Output selected Control, based on a boolean test
 262 class IfNode : public MultiBranchNode {
 263   // Size is bigger to hold the probability field.  However, _prob does not
 264   // change the semantics so it does not appear in the hash & cmp functions.
 265   virtual uint size_of() const { return sizeof(*this); }
 266 
 267 private:
 268   ProjNode* range_check_trap_proj(int& flip, Node*& l, Node*& r);
 269   ProjNode* range_check_trap_proj() {
 270     int flip_test = 0;
 271     Node* l = NULL;
 272     Node* r = NULL;
 273     return range_check_trap_proj(flip_test, l, r);
 274   }
 275 
 276   // Helper methods for fold_compares
 277   bool cmpi_folds(PhaseIterGVN* igvn);
 278   bool is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn);
 279   bool has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail);
 280   bool has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn);
 281   static void merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn);
 282   static void improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn);
 283   bool is_cmp_with_loadrange(ProjNode* proj);
 284   bool is_null_check(ProjNode* proj, PhaseIterGVN* igvn);
 285   bool is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn);
 286   void reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn);
 287   ProjNode* uncommon_trap_proj(CallStaticJavaNode*& call) const;
 288   bool fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn);
 289 
 290 public:
 291 
 292   // Degrees of branch prediction probability by order of magnitude:
 293   // PROB_UNLIKELY_1e(N) is a 1 in 1eN chance.
 294   // PROB_LIKELY_1e(N) is a 1 - PROB_UNLIKELY_1e(N)
 295 #define PROB_UNLIKELY_MAG(N)    (1e- ## N ## f)
 296 #define PROB_LIKELY_MAG(N)      (1.0f-PROB_UNLIKELY_MAG(N))
 297 
 298   // Maximum and minimum branch prediction probabilties
 299   // 1 in 1,000,000 (magnitude 6)
 300   //
 301   // Although PROB_NEVER == PROB_MIN and PROB_ALWAYS == PROB_MAX
 302   // they are used to distinguish different situations:
 303   //
 304   // The name PROB_MAX (PROB_MIN) is for probabilities which correspond to
 305   // very likely (unlikely) but with a concrete possibility of a rare
 306   // contrary case.  These constants would be used for pinning
 307   // measurements, and as measures for assertions that have high
 308   // confidence, but some evidence of occasional failure.
 309   //
 310   // The name PROB_ALWAYS (PROB_NEVER) is to stand for situations for which
 311   // there is no evidence at all that the contrary case has ever occurred.
 312 
 313 #define PROB_NEVER              PROB_UNLIKELY_MAG(6)
 314 #define PROB_ALWAYS             PROB_LIKELY_MAG(6)
 315 
 316 #define PROB_MIN                PROB_UNLIKELY_MAG(6)
 317 #define PROB_MAX                PROB_LIKELY_MAG(6)
 318 
 319   // Static branch prediction probabilities
 320   // 1 in 10 (magnitude 1)
 321 #define PROB_STATIC_INFREQUENT  PROB_UNLIKELY_MAG(1)
 322 #define PROB_STATIC_FREQUENT    PROB_LIKELY_MAG(1)
 323 
 324   // Fair probability 50/50
 325 #define PROB_FAIR               (0.5f)
 326 
 327   // Unknown probability sentinel
 328 #define PROB_UNKNOWN            (-1.0f)
 329 
 330   // Probability "constructors", to distinguish as a probability any manifest
 331   // constant without a names
 332 #define PROB_LIKELY(x)          ((float) (x))
 333 #define PROB_UNLIKELY(x)        (1.0f - (float)(x))
 334 
 335   // Other probabilities in use, but without a unique name, are documented
 336   // here for lack of a better place:
 337   //
 338   // 1 in 1000 probabilities (magnitude 3):
 339   //     threshold for converting to conditional move
 340   //     likelihood of null check failure if a null HAS been seen before
 341   //     likelihood of slow path taken in library calls
 342   //
 343   // 1 in 10,000 probabilities (magnitude 4):
 344   //     threshold for making an uncommon trap probability more extreme
 345   //     threshold for for making a null check implicit
 346   //     likelihood of needing a gc if eden top moves during an allocation
 347   //     likelihood of a predicted call failure
 348   //
 349   // 1 in 100,000 probabilities (magnitude 5):
 350   //     threshold for ignoring counts when estimating path frequency
 351   //     likelihood of FP clipping failure
 352   //     likelihood of catching an exception from a try block
 353   //     likelihood of null check failure if a null has NOT been seen before
 354   //
 355   // Magic manifest probabilities such as 0.83, 0.7, ... can be found in
 356   // gen_subtype_check() and catch_inline_exceptions().
 357 
 358   float _prob;                  // Probability of true path being taken.
 359   float _fcnt;                  // Frequency counter
 360   IfNode( Node *control, Node *b, float p, float fcnt )
 361     : MultiBranchNode(2), _prob(p), _fcnt(fcnt) {
 362     init_class_id(Class_If);
 363     init_req(0,control);
 364     init_req(1,b);
 365   }
 366   virtual int Opcode() const;
 367   virtual bool pinned() const { return true; }
 368   virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
 369   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 370   virtual const Type *Value( PhaseTransform *phase ) const;
 371   virtual int required_outcnt() const { return 2; }
 372   virtual const RegMask &out_RegMask() const;
 373   void dominated_by(Node* prev_dom, PhaseIterGVN* igvn);
 374   int is_range_check(Node* &range, Node* &index, jint &offset);
 375   Node* fold_compares(PhaseIterGVN* phase);
 376   static Node* up_one_dom(Node* curr, bool linear_only = false);
 377 
 378   // Takes the type of val and filters it through the test represented
 379   // by if_proj and returns a more refined type if one is produced.
 380   // Returns NULL is it couldn't improve the type.
 381   static const TypeInt* filtered_int_type(PhaseGVN* phase, Node* val, Node* if_proj);
 382 
 383 #ifndef PRODUCT
 384   virtual void dump_spec(outputStream *st) const;
 385 #endif
 386 };
 387 
 388 class IfProjNode : public CProjNode {
 389 public:
 390   IfProjNode(IfNode *ifnode, uint idx) : CProjNode(ifnode,idx) {}
 391   virtual Node *Identity(PhaseTransform *phase);
 392 
 393 protected:
 394   // Type of If input when this branch is always taken
 395   virtual bool always_taken(const TypeTuple* t) const = 0;
 396 };
 397 
 398 class IfTrueNode : public IfProjNode {
 399 public:
 400   IfTrueNode( IfNode *ifnode ) : IfProjNode(ifnode,1) {
 401     init_class_id(Class_IfTrue);
 402   }
 403   virtual int Opcode() const;
 404 
 405 protected:
 406   virtual bool always_taken(const TypeTuple* t) const { return t == TypeTuple::IFTRUE; }
 407 };
 408 
 409 class IfFalseNode : public IfProjNode {
 410 public:
 411   IfFalseNode( IfNode *ifnode ) : IfProjNode(ifnode,0) {
 412     init_class_id(Class_IfFalse);
 413   }
 414   virtual int Opcode() const;
 415 
 416 protected:
 417   virtual bool always_taken(const TypeTuple* t) const { return t == TypeTuple::IFFALSE; }
 418 };
 419 
 420 
 421 //------------------------------PCTableNode------------------------------------
 422 // Build an indirect branch table.  Given a control and a table index,
 423 // control is passed to the Projection matching the table index.  Used to
 424 // implement switch statements and exception-handling capabilities.
 425 // Undefined behavior if passed-in index is not inside the table.
 426 class PCTableNode : public MultiBranchNode {
 427   virtual uint hash() const;    // Target count; table size
 428   virtual uint cmp( const Node &n ) const;
 429   virtual uint size_of() const { return sizeof(*this); }
 430 
 431 public:
 432   const uint _size;             // Number of targets
 433 
 434   PCTableNode( Node *ctrl, Node *idx, uint size ) : MultiBranchNode(2), _size(size) {
 435     init_class_id(Class_PCTable);
 436     init_req(0, ctrl);
 437     init_req(1, idx);
 438   }
 439   virtual int Opcode() const;
 440   virtual const Type *Value( PhaseTransform *phase ) const;
 441   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 442   virtual const Type *bottom_type() const;
 443   virtual bool pinned() const { return true; }
 444   virtual int required_outcnt() const { return _size; }
 445 };
 446 
 447 //------------------------------JumpNode---------------------------------------
 448 // Indirect branch.  Uses PCTable above to implement a switch statement.
 449 // It emits as a table load and local branch.
 450 class JumpNode : public PCTableNode {
 451 public:
 452   JumpNode( Node* control, Node* switch_val, uint size) : PCTableNode(control, switch_val, size) {
 453     init_class_id(Class_Jump);
 454   }
 455   virtual int   Opcode() const;
 456   virtual const RegMask& out_RegMask() const;
 457   virtual const Node* is_block_proj() const { return this; }
 458 };
 459 
 460 class JumpProjNode : public JProjNode {
 461   virtual uint hash() const;
 462   virtual uint cmp( const Node &n ) const;
 463   virtual uint size_of() const { return sizeof(*this); }
 464 
 465  private:
 466   const int  _dest_bci;
 467   const uint _proj_no;
 468   const int  _switch_val;
 469  public:
 470   JumpProjNode(Node* jumpnode, uint proj_no, int dest_bci, int switch_val)
 471     : JProjNode(jumpnode, proj_no), _dest_bci(dest_bci), _proj_no(proj_no), _switch_val(switch_val) {
 472     init_class_id(Class_JumpProj);
 473   }
 474 
 475   virtual int Opcode() const;
 476   virtual const Type* bottom_type() const { return Type::CONTROL; }
 477   int  dest_bci()    const { return _dest_bci; }
 478   int  switch_val()  const { return _switch_val; }
 479   uint proj_no()     const { return _proj_no; }
 480 #ifndef PRODUCT
 481   virtual void dump_spec(outputStream *st) const;
 482 #endif
 483 };
 484 
 485 //------------------------------CatchNode--------------------------------------
 486 // Helper node to fork exceptions.  "Catch" catches any exceptions thrown by
 487 // a just-prior call.  Looks like a PCTableNode but emits no code - just the
 488 // table.  The table lookup and branch is implemented by RethrowNode.
 489 class CatchNode : public PCTableNode {
 490 public:
 491   CatchNode( Node *ctrl, Node *idx, uint size ) : PCTableNode(ctrl,idx,size){
 492     init_class_id(Class_Catch);
 493   }
 494   virtual int Opcode() const;
 495   virtual const Type *Value( PhaseTransform *phase ) const;
 496 };
 497 
 498 // CatchProjNode controls which exception handler is targetted after a call.
 499 // It is passed in the bci of the target handler, or no_handler_bci in case
 500 // the projection doesn't lead to an exception handler.
 501 class CatchProjNode : public CProjNode {
 502   virtual uint hash() const;
 503   virtual uint cmp( const Node &n ) const;
 504   virtual uint size_of() const { return sizeof(*this); }
 505 
 506 private:
 507   const int _handler_bci;
 508 
 509 public:
 510   enum {
 511     fall_through_index =  0,      // the fall through projection index
 512     catch_all_index    =  1,      // the projection index for catch-alls
 513     no_handler_bci     = -1       // the bci for fall through or catch-all projs
 514   };
 515 
 516   CatchProjNode(Node* catchnode, uint proj_no, int handler_bci)
 517     : CProjNode(catchnode, proj_no), _handler_bci(handler_bci) {
 518     init_class_id(Class_CatchProj);
 519     assert(proj_no != fall_through_index || handler_bci < 0, "fall through case must have bci < 0");
 520   }
 521 
 522   virtual int Opcode() const;
 523   virtual Node *Identity( PhaseTransform *phase );
 524   virtual const Type *bottom_type() const { return Type::CONTROL; }
 525   int  handler_bci() const        { return _handler_bci; }
 526   bool is_handler_proj() const    { return _handler_bci >= 0; }
 527 #ifndef PRODUCT
 528   virtual void dump_spec(outputStream *st) const;
 529 #endif
 530 };
 531 
 532 
 533 //---------------------------------CreateExNode--------------------------------
 534 // Helper node to create the exception coming back from a call
 535 class CreateExNode : public TypeNode {
 536 public:
 537   CreateExNode(const Type* t, Node* control, Node* i_o) : TypeNode(t, 2) {
 538     init_req(0, control);
 539     init_req(1, i_o);
 540   }
 541   virtual int Opcode() const;
 542   virtual Node *Identity( PhaseTransform *phase );
 543   virtual bool pinned() const { return true; }
 544   uint match_edge(uint idx) const { return 0; }
 545   virtual uint ideal_reg() const { return Op_RegP; }
 546 };
 547 
 548 //------------------------------NeverBranchNode-------------------------------
 549 // The never-taken branch.  Used to give the appearance of exiting infinite
 550 // loops to those algorithms that like all paths to be reachable.  Encodes
 551 // empty.
 552 class NeverBranchNode : public MultiBranchNode {
 553 public:
 554   NeverBranchNode( Node *ctrl ) : MultiBranchNode(1) { init_req(0,ctrl); }
 555   virtual int Opcode() const;
 556   virtual bool pinned() const { return true; };
 557   virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
 558   virtual const Type *Value( PhaseTransform *phase ) const;
 559   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 560   virtual int required_outcnt() const { return 2; }
 561   virtual void emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const { }
 562   virtual uint size(PhaseRegAlloc *ra_) const { return 0; }
 563 #ifndef PRODUCT
 564   virtual void format( PhaseRegAlloc *, outputStream *st ) const;
 565 #endif
 566 };
 567 
 568 #endif // SHARE_VM_OPTO_CFGNODE_HPP