1 /*
   2  * Copyright (c) 1997, 2008, 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 // Portions of code courtesy of Clifford Click
  26 
  27 // Optimization - Graph Style
  28 
  29 class Matcher;
  30 class Node;
  31 class   RegionNode;
  32 class   TypeNode;
  33 class     PhiNode;
  34 class   GotoNode;
  35 class   MultiNode;
  36 class     MultiBranchNode;
  37 class       IfNode;
  38 class       PCTableNode;
  39 class         JumpNode;
  40 class         CatchNode;
  41 class       NeverBranchNode;
  42 class   ProjNode;
  43 class     CProjNode;
  44 class       IfTrueNode;
  45 class       IfFalseNode;
  46 class       CatchProjNode;
  47 class     JProjNode;
  48 class       JumpProjNode;
  49 class     SCMemProjNode;
  50 class PhaseIdealLoop;
  51 
  52 //------------------------------RegionNode-------------------------------------
  53 // The class of RegionNodes, which can be mapped to basic blocks in the
  54 // program.  Their inputs point to Control sources.  PhiNodes (described
  55 // below) have an input point to a RegionNode.  Merged data inputs to PhiNodes
  56 // correspond 1-to-1 with RegionNode inputs.  The zero input of a PhiNode is
  57 // the RegionNode, and the zero input of the RegionNode is itself.
  58 class RegionNode : public Node {
  59 public:
  60   // Node layout (parallels PhiNode):
  61   enum { Region,                // Generally points to self.
  62          Control                // Control arcs are [1..len)
  63   };
  64 
  65   RegionNode( uint required ) : Node(required) {
  66     init_class_id(Class_Region);
  67     init_req(0,this);
  68   }
  69 
  70   Node* is_copy() const {
  71     const Node* r = _in[Region];
  72     if (r == NULL)
  73       return nonnull_req();
  74     return NULL;  // not a copy!
  75   }
  76   PhiNode* has_phi() const;        // returns an arbitrary phi user, or NULL
  77   PhiNode* has_unique_phi() const; // returns the unique phi user, or NULL
  78   // Is this region node unreachable from root?
  79   bool is_unreachable_region(PhaseGVN *phase) const;
  80   virtual int Opcode() const;
  81   virtual bool pinned() const { return (const Node *)in(0) == this; }
  82   virtual bool  is_CFG   () const { return true; }
  83   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
  84   virtual bool depends_only_on_test() const { return false; }
  85   virtual const Type *bottom_type() const { return Type::CONTROL; }
  86   virtual const Type *Value( PhaseTransform *phase ) const;
  87   virtual Node *Identity( PhaseTransform *phase );
  88   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
  89   virtual const RegMask &out_RegMask() const;
  90 };
  91 
  92 //------------------------------JProjNode--------------------------------------
  93 // jump projection for node that produces multiple control-flow paths
  94 class JProjNode : public ProjNode {
  95  public:
  96   JProjNode( Node* ctrl, uint idx ) : ProjNode(ctrl,idx) {}
  97   virtual int Opcode() const;
  98   virtual bool  is_CFG() const { return true; }
  99   virtual uint  hash() const { return NO_HASH; }  // CFG nodes do not hash
 100   virtual const Node* is_block_proj() const { return in(0); }
 101   virtual const RegMask& out_RegMask() const;
 102   virtual uint  ideal_reg() const { return 0; }
 103 };
 104 
 105 //------------------------------PhiNode----------------------------------------
 106 // PhiNodes merge values from different Control paths.  Slot 0 points to the
 107 // controlling RegionNode.  Other slots map 1-for-1 with incoming control flow
 108 // paths to the RegionNode.  For speed reasons (to avoid another pass) we
 109 // can turn PhiNodes into copys in-place by NULL'ing out their RegionNode
 110 // input in slot 0.
 111 class PhiNode : public TypeNode {
 112   const TypePtr* const _adr_type; // non-null only for Type::MEMORY nodes.
 113   const int _inst_id;     // Instance id of the memory slice.
 114   const int _inst_index;  // Alias index of the instance memory slice.
 115   // Array elements references have the same alias_idx but different offset.
 116   const int _inst_offset; // Offset of the instance memory slice.
 117   // Size is bigger to hold the _adr_type field.
 118   virtual uint hash() const;    // Check the type
 119   virtual uint cmp( const Node &n ) const;
 120   virtual uint size_of() const { return sizeof(*this); }
 121 
 122   // Determine if CMoveNode::is_cmove_id can be used at this join point.
 123   Node* is_cmove_id(PhaseTransform* phase, int true_path);
 124 
 125 public:
 126   // Node layout (parallels RegionNode):
 127   enum { Region,                // Control input is the Phi's region.
 128          Input                  // Input values are [1..len)
 129   };
 130 
 131   PhiNode( Node *r, const Type *t, const TypePtr* at = NULL,
 132            const int iid = TypeOopPtr::InstanceTop,
 133            const int iidx = Compile::AliasIdxTop,
 134            const int ioffs = Type::OffsetTop )
 135     : TypeNode(t,r->req()),
 136       _adr_type(at),
 137       _inst_id(iid),
 138       _inst_index(iidx),
 139       _inst_offset(ioffs)
 140   {
 141     init_class_id(Class_Phi);
 142     init_req(0, r);
 143     verify_adr_type();
 144   }
 145   // create a new phi with in edges matching r and set (initially) to x
 146   static PhiNode* make( Node* r, Node* x );
 147   // extra type arguments override the new phi's bottom_type and adr_type
 148   static PhiNode* make( Node* r, Node* x, const Type *t, const TypePtr* at = NULL );
 149   // create a new phi with narrowed memory type
 150   PhiNode* slice_memory(const TypePtr* adr_type) const;
 151   PhiNode* split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const;
 152   // like make(r, x), but does not initialize the in edges to x
 153   static PhiNode* make_blank( Node* r, Node* x );
 154 
 155   // Accessors
 156   RegionNode* region() const { Node* r = in(Region); assert(!r || r->is_Region(), ""); return (RegionNode*)r; }
 157 
 158   Node* is_copy() const {
 159     // The node is a real phi if _in[0] is a Region node.
 160     DEBUG_ONLY(const Node* r = _in[Region];)
 161     assert(r != NULL && r->is_Region(), "Not valid control");
 162     return NULL;  // not a copy!
 163   }
 164 
 165   bool is_tripcount() const;
 166 
 167   // Determine a unique non-trivial input, if any.
 168   // Ignore casts if it helps.  Return NULL on failure.
 169   Node* unique_input(PhaseTransform *phase);
 170 
 171   // Check for a simple dead loop.
 172   enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
 173   LoopSafety simple_data_loop_check(Node *in) const;
 174   // Is it unsafe data loop? It becomes a dead loop if this phi node removed.
 175   bool is_unsafe_data_reference(Node *in) const;
 176   int  is_diamond_phi() const;
 177   virtual int Opcode() const;
 178   virtual bool pinned() const { return in(0) != 0; }
 179   virtual const TypePtr *adr_type() const { verify_adr_type(true); return _adr_type; }
 180 
 181   const int inst_id()     const { return _inst_id; }
 182   const int inst_index()  const { return _inst_index; }
 183   const int inst_offset() const { return _inst_offset; }
 184   bool is_same_inst_field(const Type* tp, int id, int index, int offset) {
 185     return type()->basic_type() == tp->basic_type() &&
 186            inst_id()     == id     &&
 187            inst_index()  == index  &&
 188            inst_offset() == offset &&
 189            type()->higher_equal(tp);
 190   }
 191 
 192   virtual const Type *Value( PhaseTransform *phase ) const;
 193   virtual Node *Identity( PhaseTransform *phase );
 194   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 195   virtual const RegMask &out_RegMask() const;
 196   virtual const RegMask &in_RegMask(uint) const;
 197 #ifndef PRODUCT
 198   virtual void dump_spec(outputStream *st) const;
 199 #endif
 200 #ifdef ASSERT
 201   void verify_adr_type(VectorSet& visited, const TypePtr* at) const;
 202   void verify_adr_type(bool recursive = false) const;
 203 #else //ASSERT
 204   void verify_adr_type(bool recursive = false) const {}
 205 #endif //ASSERT
 206 };
 207 
 208 //------------------------------GotoNode---------------------------------------
 209 // GotoNodes perform direct branches.
 210 class GotoNode : public Node {
 211 public:
 212   GotoNode( Node *control ) : Node(control) {
 213     init_flags(Flag_is_Goto);
 214   }
 215   virtual int Opcode() const;
 216   virtual bool pinned() const { return true; }
 217   virtual bool  is_CFG() const { return true; }
 218   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
 219   virtual const Node *is_block_proj() const { return this; }
 220   virtual bool depends_only_on_test() const { return false; }
 221   virtual const Type *bottom_type() const { return Type::CONTROL; }
 222   virtual const Type *Value( PhaseTransform *phase ) const;
 223   virtual Node *Identity( PhaseTransform *phase );
 224   virtual const RegMask &out_RegMask() const;
 225 };
 226 
 227 //------------------------------CProjNode--------------------------------------
 228 // control projection for node that produces multiple control-flow paths
 229 class CProjNode : public ProjNode {
 230 public:
 231   CProjNode( Node *ctrl, uint idx ) : ProjNode(ctrl,idx) {}
 232   virtual int Opcode() const;
 233   virtual bool  is_CFG() const { return true; }
 234   virtual uint hash() const { return NO_HASH; }  // CFG nodes do not hash
 235   virtual const Node *is_block_proj() const { return in(0); }
 236   virtual const RegMask &out_RegMask() const;
 237   virtual uint ideal_reg() const { return 0; }
 238 };
 239 
 240 //---------------------------MultiBranchNode-----------------------------------
 241 // This class defines a MultiBranchNode, a MultiNode which yields multiple
 242 // control values. These are distinguished from other types of MultiNodes
 243 // which yield multiple values, but control is always and only projection #0.
 244 class MultiBranchNode : public MultiNode {
 245 public:
 246   MultiBranchNode( uint required ) : MultiNode(required) {
 247     init_class_id(Class_MultiBranch);
 248   }
 249   // returns required number of users to be well formed.
 250   virtual int required_outcnt() const = 0;
 251 };
 252 
 253 //------------------------------IfNode-----------------------------------------
 254 // Output selected Control, based on a boolean test
 255 class IfNode : public MultiBranchNode {
 256   // Size is bigger to hold the probability field.  However, _prob does not
 257   // change the semantics so it does not appear in the hash & cmp functions.
 258   virtual uint size_of() const { return sizeof(*this); }
 259 public:
 260 
 261   // Degrees of branch prediction probability by order of magnitude:
 262   // PROB_UNLIKELY_1e(N) is a 1 in 1eN chance.
 263   // PROB_LIKELY_1e(N) is a 1 - PROB_UNLIKELY_1e(N)
 264 #define PROB_UNLIKELY_MAG(N)    (1e- ## N ## f)
 265 #define PROB_LIKELY_MAG(N)      (1.0f-PROB_UNLIKELY_MAG(N))
 266 
 267   // Maximum and minimum branch prediction probabilties
 268   // 1 in 1,000,000 (magnitude 6)
 269   //
 270   // Although PROB_NEVER == PROB_MIN and PROB_ALWAYS == PROB_MAX
 271   // they are used to distinguish different situations:
 272   //
 273   // The name PROB_MAX (PROB_MIN) is for probabilities which correspond to
 274   // very likely (unlikely) but with a concrete possibility of a rare
 275   // contrary case.  These constants would be used for pinning
 276   // measurements, and as measures for assertions that have high
 277   // confidence, but some evidence of occasional failure.
 278   //
 279   // The name PROB_ALWAYS (PROB_NEVER) is to stand for situations for which
 280   // there is no evidence at all that the contrary case has ever occurred.
 281 
 282 #define PROB_NEVER              PROB_UNLIKELY_MAG(6)
 283 #define PROB_ALWAYS             PROB_LIKELY_MAG(6)
 284 
 285 #define PROB_MIN                PROB_UNLIKELY_MAG(6)
 286 #define PROB_MAX                PROB_LIKELY_MAG(6)
 287 
 288   // Static branch prediction probabilities
 289   // 1 in 10 (magnitude 1)
 290 #define PROB_STATIC_INFREQUENT  PROB_UNLIKELY_MAG(1)
 291 #define PROB_STATIC_FREQUENT    PROB_LIKELY_MAG(1)
 292 
 293   // Fair probability 50/50
 294 #define PROB_FAIR               (0.5f)
 295 
 296   // Unknown probability sentinel
 297 #define PROB_UNKNOWN            (-1.0f)
 298 
 299   // Probability "constructors", to distinguish as a probability any manifest
 300   // constant without a names
 301 #define PROB_LIKELY(x)          ((float) (x))
 302 #define PROB_UNLIKELY(x)        (1.0f - (float)(x))
 303 
 304   // Other probabilities in use, but without a unique name, are documented
 305   // here for lack of a better place:
 306   //
 307   // 1 in 1000 probabilities (magnitude 3):
 308   //     threshold for converting to conditional move
 309   //     likelihood of null check failure if a null HAS been seen before
 310   //     likelihood of slow path taken in library calls
 311   //
 312   // 1 in 10,000 probabilities (magnitude 4):
 313   //     threshold for making an uncommon trap probability more extreme
 314   //     threshold for for making a null check implicit
 315   //     likelihood of needing a gc if eden top moves during an allocation
 316   //     likelihood of a predicted call failure
 317   //
 318   // 1 in 100,000 probabilities (magnitude 5):
 319   //     threshold for ignoring counts when estimating path frequency
 320   //     likelihood of FP clipping failure
 321   //     likelihood of catching an exception from a try block
 322   //     likelihood of null check failure if a null has NOT been seen before
 323   //
 324   // Magic manifest probabilities such as 0.83, 0.7, ... can be found in
 325   // gen_subtype_check() and catch_inline_exceptions().
 326 
 327   float _prob;                  // Probability of true path being taken.
 328   float _fcnt;                  // Frequency counter
 329   IfNode( Node *control, Node *b, float p, float fcnt )
 330     : MultiBranchNode(2), _prob(p), _fcnt(fcnt) {
 331     init_class_id(Class_If);
 332     init_req(0,control);
 333     init_req(1,b);
 334   }
 335   virtual int Opcode() const;
 336   virtual bool pinned() const { return true; }
 337   virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
 338   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 339   virtual const Type *Value( PhaseTransform *phase ) const;
 340   virtual int required_outcnt() const { return 2; }
 341   virtual const RegMask &out_RegMask() const;
 342   void dominated_by(Node* prev_dom, PhaseIterGVN* igvn);
 343   int is_range_check(Node* &range, Node* &index, jint &offset);
 344   Node* fold_compares(PhaseGVN* phase);
 345   static Node* up_one_dom(Node* curr, bool linear_only = false);
 346 
 347   // Takes the type of val and filters it through the test represented
 348   // by if_proj and returns a more refined type if one is produced.
 349   // Returns NULL is it couldn't improve the type.
 350   static const TypeInt* filtered_int_type(PhaseGVN* phase, Node* val, Node* if_proj);
 351 
 352 #ifndef PRODUCT
 353   virtual void dump_spec(outputStream *st) const;
 354 #endif
 355 };
 356 
 357 class IfTrueNode : public CProjNode {
 358 public:
 359   IfTrueNode( IfNode *ifnode ) : CProjNode(ifnode,1) {
 360     init_class_id(Class_IfTrue);
 361   }
 362   virtual int Opcode() const;
 363   virtual Node *Identity( PhaseTransform *phase );
 364 };
 365 
 366 class IfFalseNode : public CProjNode {
 367 public:
 368   IfFalseNode( IfNode *ifnode ) : CProjNode(ifnode,0) {
 369     init_class_id(Class_IfFalse);
 370   }
 371   virtual int Opcode() const;
 372   virtual Node *Identity( PhaseTransform *phase );
 373 };
 374 
 375 
 376 //------------------------------PCTableNode------------------------------------
 377 // Build an indirect branch table.  Given a control and a table index,
 378 // control is passed to the Projection matching the table index.  Used to
 379 // implement switch statements and exception-handling capabilities.
 380 // Undefined behavior if passed-in index is not inside the table.
 381 class PCTableNode : public MultiBranchNode {
 382   virtual uint hash() const;    // Target count; table size
 383   virtual uint cmp( const Node &n ) const;
 384   virtual uint size_of() const { return sizeof(*this); }
 385 
 386 public:
 387   const uint _size;             // Number of targets
 388 
 389   PCTableNode( Node *ctrl, Node *idx, uint size ) : MultiBranchNode(2), _size(size) {
 390     init_class_id(Class_PCTable);
 391     init_req(0, ctrl);
 392     init_req(1, idx);
 393   }
 394   virtual int Opcode() const;
 395   virtual const Type *Value( PhaseTransform *phase ) const;
 396   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 397   virtual const Type *bottom_type() const;
 398   virtual bool pinned() const { return true; }
 399   virtual int required_outcnt() const { return _size; }
 400 };
 401 
 402 //------------------------------JumpNode---------------------------------------
 403 // Indirect branch.  Uses PCTable above to implement a switch statement.
 404 // It emits as a table load and local branch.
 405 class JumpNode : public PCTableNode {
 406 public:
 407   JumpNode( Node* control, Node* switch_val, uint size) : PCTableNode(control, switch_val, size) {
 408     init_class_id(Class_Jump);
 409   }
 410   virtual int   Opcode() const;
 411   virtual const RegMask& out_RegMask() const;
 412   virtual const Node* is_block_proj() const { return this; }
 413 };
 414 
 415 class JumpProjNode : public JProjNode {
 416   virtual uint hash() const;
 417   virtual uint cmp( const Node &n ) const;
 418   virtual uint size_of() const { return sizeof(*this); }
 419 
 420  private:
 421   const int  _dest_bci;
 422   const uint _proj_no;
 423   const int  _switch_val;
 424  public:
 425   JumpProjNode(Node* jumpnode, uint proj_no, int dest_bci, int switch_val)
 426     : JProjNode(jumpnode, proj_no), _dest_bci(dest_bci), _proj_no(proj_no), _switch_val(switch_val) {
 427     init_class_id(Class_JumpProj);
 428   }
 429 
 430   virtual int Opcode() const;
 431   virtual const Type* bottom_type() const { return Type::CONTROL; }
 432   int  dest_bci()    const { return _dest_bci; }
 433   int  switch_val()  const { return _switch_val; }
 434   uint proj_no()     const { return _proj_no; }
 435 #ifndef PRODUCT
 436   virtual void dump_spec(outputStream *st) const;
 437 #endif
 438 };
 439 
 440 //------------------------------CatchNode--------------------------------------
 441 // Helper node to fork exceptions.  "Catch" catches any exceptions thrown by
 442 // a just-prior call.  Looks like a PCTableNode but emits no code - just the
 443 // table.  The table lookup and branch is implemented by RethrowNode.
 444 class CatchNode : public PCTableNode {
 445 public:
 446   CatchNode( Node *ctrl, Node *idx, uint size ) : PCTableNode(ctrl,idx,size){
 447     init_class_id(Class_Catch);
 448   }
 449   virtual int Opcode() const;
 450   virtual const Type *Value( PhaseTransform *phase ) const;
 451 };
 452 
 453 // CatchProjNode controls which exception handler is targetted after a call.
 454 // It is passed in the bci of the target handler, or no_handler_bci in case
 455 // the projection doesn't lead to an exception handler.
 456 class CatchProjNode : public CProjNode {
 457   virtual uint hash() const;
 458   virtual uint cmp( const Node &n ) const;
 459   virtual uint size_of() const { return sizeof(*this); }
 460 
 461 private:
 462   const int _handler_bci;
 463 
 464 public:
 465   enum {
 466     fall_through_index =  0,      // the fall through projection index
 467     catch_all_index    =  1,      // the projection index for catch-alls
 468     no_handler_bci     = -1       // the bci for fall through or catch-all projs
 469   };
 470 
 471   CatchProjNode(Node* catchnode, uint proj_no, int handler_bci)
 472     : CProjNode(catchnode, proj_no), _handler_bci(handler_bci) {
 473     init_class_id(Class_CatchProj);
 474     assert(proj_no != fall_through_index || handler_bci < 0, "fall through case must have bci < 0");
 475   }
 476 
 477   virtual int Opcode() const;
 478   virtual Node *Identity( PhaseTransform *phase );
 479   virtual const Type *bottom_type() const { return Type::CONTROL; }
 480   int  handler_bci() const        { return _handler_bci; }
 481   bool is_handler_proj() const    { return _handler_bci >= 0; }
 482 #ifndef PRODUCT
 483   virtual void dump_spec(outputStream *st) const;
 484 #endif
 485 };
 486 
 487 
 488 //---------------------------------CreateExNode--------------------------------
 489 // Helper node to create the exception coming back from a call
 490 class CreateExNode : public TypeNode {
 491 public:
 492   CreateExNode(const Type* t, Node* control, Node* i_o) : TypeNode(t, 2) {
 493     init_req(0, control);
 494     init_req(1, i_o);
 495   }
 496   virtual int Opcode() const;
 497   virtual Node *Identity( PhaseTransform *phase );
 498   virtual bool pinned() const { return true; }
 499   uint match_edge(uint idx) const { return 0; }
 500   virtual uint ideal_reg() const { return Op_RegP; }
 501 };
 502 
 503 //------------------------------NeverBranchNode-------------------------------
 504 // The never-taken branch.  Used to give the appearance of exiting infinite
 505 // loops to those algorithms that like all paths to be reachable.  Encodes
 506 // empty.
 507 class NeverBranchNode : public MultiBranchNode {
 508 public:
 509   NeverBranchNode( Node *ctrl ) : MultiBranchNode(1) { init_req(0,ctrl); }
 510   virtual int Opcode() const;
 511   virtual bool pinned() const { return true; };
 512   virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
 513   virtual const Type *Value( PhaseTransform *phase ) const;
 514   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
 515   virtual int required_outcnt() const { return 2; }
 516   virtual void emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const { }
 517   virtual uint size(PhaseRegAlloc *ra_) const { return 0; }
 518 #ifndef PRODUCT
 519   virtual void format( PhaseRegAlloc *, outputStream *st ) const;
 520 #endif
 521 };