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  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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  23 
  24 //
  25 //                  S U P E R W O R D   T R A N S F O R M
  26 //
  27 // SuperWords are short, fixed length vectors.
  28 //
  29 // Algorithm from:
  30 //
  31 // Exploiting SuperWord Level Parallelism with
  32 //   Multimedia Instruction Sets
  33 // by
  34 //   Samuel Larsen and Saman Amarasighe
  35 //   MIT Laboratory for Computer Science
  36 // date
  37 //   May 2000
  38 // published in
  39 //   ACM SIGPLAN Notices
  40 //   Proceedings of ACM PLDI '00,  Volume 35 Issue 5
  41 //
  42 // Definition 3.1 A Pack is an n-tuple, <s1, ...,sn>, where
  43 // s1,...,sn are independent isomorphic statements in a basic
  44 // block.
  45 //
  46 // Definition 3.2 A PackSet is a set of Packs.
  47 //
  48 // Definition 3.3 A Pair is a Pack of size two, where the
  49 // first statement is considered the left element, and the
  50 // second statement is considered the right element.
  51 
  52 class SWPointer;
  53 class OrderedPair;
  54 
  55 // ========================= Dependence Graph =====================
  56 
  57 class DepMem;
  58 
  59 //------------------------------DepEdge---------------------------
  60 // An edge in the dependence graph.  The edges incident to a dependence
  61 // node are threaded through _next_in for incoming edges and _next_out
  62 // for outgoing edges.
  63 class DepEdge : public ResourceObj {
  64  protected:
  65   DepMem* _pred;
  66   DepMem* _succ;
  67   DepEdge* _next_in;   // list of in edges, null terminated
  68   DepEdge* _next_out;  // list of out edges, null terminated
  69 
  70  public:
  71   DepEdge(DepMem* pred, DepMem* succ, DepEdge* next_in, DepEdge* next_out) :
  72     _pred(pred), _succ(succ), _next_in(next_in), _next_out(next_out) {}
  73 
  74   DepEdge* next_in()  { return _next_in; }
  75   DepEdge* next_out() { return _next_out; }
  76   DepMem*  pred()     { return _pred; }
  77   DepMem*  succ()     { return _succ; }
  78 
  79   void print();
  80 };
  81 
  82 //------------------------------DepMem---------------------------
  83 // A node in the dependence graph.  _in_head starts the threaded list of
  84 // incoming edges, and _out_head starts the list of outgoing edges.
  85 class DepMem : public ResourceObj {
  86  protected:
  87   Node*    _node;     // Corresponding ideal node
  88   DepEdge* _in_head;  // Head of list of in edges, null terminated
  89   DepEdge* _out_head; // Head of list of out edges, null terminated
  90 
  91  public:
  92   DepMem(Node* node) : _node(node), _in_head(NULL), _out_head(NULL) {}
  93 
  94   Node*    node()                { return _node;     }
  95   DepEdge* in_head()             { return _in_head;  }
  96   DepEdge* out_head()            { return _out_head; }
  97   void set_in_head(DepEdge* hd)  { _in_head = hd;    }
  98   void set_out_head(DepEdge* hd) { _out_head = hd;   }
  99 
 100   int in_cnt();  // Incoming edge count
 101   int out_cnt(); // Outgoing edge count
 102 
 103   void print();
 104 };
 105 
 106 //------------------------------DepGraph---------------------------
 107 class DepGraph VALUE_OBJ_CLASS_SPEC {
 108  protected:
 109   Arena* _arena;
 110   GrowableArray<DepMem*> _map;
 111   DepMem* _root;
 112   DepMem* _tail;
 113 
 114  public:
 115   DepGraph(Arena* a) : _arena(a), _map(a, 8,  0, NULL) {
 116     _root = new (_arena) DepMem(NULL);
 117     _tail = new (_arena) DepMem(NULL);
 118   }
 119 
 120   DepMem* root() { return _root; }
 121   DepMem* tail() { return _tail; }
 122 
 123   // Return dependence node corresponding to an ideal node
 124   DepMem* dep(Node* node) { return _map.at(node->_idx); }
 125 
 126   // Make a new dependence graph node for an ideal node.
 127   DepMem* make_node(Node* node);
 128 
 129   // Make a new dependence graph edge dprec->dsucc
 130   DepEdge* make_edge(DepMem* dpred, DepMem* dsucc);
 131 
 132   DepEdge* make_edge(Node* pred,   Node* succ)   { return make_edge(dep(pred), dep(succ)); }
 133   DepEdge* make_edge(DepMem* pred, Node* succ)   { return make_edge(pred,      dep(succ)); }
 134   DepEdge* make_edge(Node* pred,   DepMem* succ) { return make_edge(dep(pred), succ);      }
 135 
 136   void init() { _map.clear(); } // initialize
 137 
 138   void print(Node* n)   { dep(n)->print(); }
 139   void print(DepMem* d) { d->print(); }
 140 };
 141 
 142 //------------------------------DepPreds---------------------------
 143 // Iterator over predecessors in the dependence graph and
 144 // non-memory-graph inputs of ideal nodes.
 145 class DepPreds : public StackObj {
 146 private:
 147   Node*    _n;
 148   int      _next_idx, _end_idx;
 149   DepEdge* _dep_next;
 150   Node*    _current;
 151   bool     _done;
 152 
 153 public:
 154   DepPreds(Node* n, DepGraph& dg);
 155   Node* current() { return _current; }
 156   bool  done()    { return _done; }
 157   void  next();
 158 };
 159 
 160 //------------------------------DepSuccs---------------------------
 161 // Iterator over successors in the dependence graph and
 162 // non-memory-graph outputs of ideal nodes.
 163 class DepSuccs : public StackObj {
 164 private:
 165   Node*    _n;
 166   int      _next_idx, _end_idx;
 167   DepEdge* _dep_next;
 168   Node*    _current;
 169   bool     _done;
 170 
 171 public:
 172   DepSuccs(Node* n, DepGraph& dg);
 173   Node* current() { return _current; }
 174   bool  done()    { return _done; }
 175   void  next();
 176 };
 177 
 178 
 179 // ========================= SuperWord =====================
 180 
 181 // -----------------------------SWNodeInfo---------------------------------
 182 // Per node info needed by SuperWord
 183 class SWNodeInfo VALUE_OBJ_CLASS_SPEC {
 184  public:
 185   int         _alignment; // memory alignment for a node
 186   int         _depth;     // Max expression (DAG) depth from block start
 187   const Type* _velt_type; // vector element type
 188   Node_List*  _my_pack;   // pack containing this node
 189 
 190   SWNodeInfo() : _alignment(-1), _depth(0), _velt_type(NULL), _my_pack(NULL) {}
 191   static const SWNodeInfo initial;
 192 };
 193 
 194 // -----------------------------SuperWord---------------------------------
 195 // Transforms scalar operations into packed (superword) operations.
 196 class SuperWord : public ResourceObj {
 197  private:
 198   PhaseIdealLoop* _phase;
 199   Arena*          _arena;
 200   PhaseIterGVN   &_igvn;
 201 
 202   enum consts { top_align = -1, bottom_align = -666 };
 203 
 204   GrowableArray<Node_List*> _packset;    // Packs for the current block
 205 
 206   GrowableArray<int> _bb_idx;            // Map from Node _idx to index within block
 207 
 208   GrowableArray<Node*> _block;           // Nodes in current block
 209   GrowableArray<Node*> _data_entry;      // Nodes with all inputs from outside
 210   GrowableArray<Node*> _mem_slice_head;  // Memory slice head nodes
 211   GrowableArray<Node*> _mem_slice_tail;  // Memory slice tail nodes
 212 
 213   GrowableArray<SWNodeInfo> _node_info;  // Info needed per node
 214 
 215   MemNode* _align_to_ref;                // Memory reference that pre-loop will align to
 216 
 217   GrowableArray<OrderedPair> _disjoint_ptrs; // runtime disambiguated pointer pairs
 218 
 219   DepGraph _dg; // Dependence graph
 220 
 221   // Scratch pads
 222   VectorSet    _visited;       // Visited set
 223   VectorSet    _post_visited;  // Post-visited set
 224   Node_Stack   _n_idx_list;    // List of (node,index) pairs
 225   GrowableArray<Node*> _nlist; // List of nodes
 226   GrowableArray<Node*> _stk;   // Stack of nodes
 227 
 228  public:
 229   SuperWord(PhaseIdealLoop* phase);
 230 
 231   void transform_loop(IdealLoopTree* lpt);
 232 
 233   // Accessors for SWPointer
 234   PhaseIdealLoop* phase()          { return _phase; }
 235   IdealLoopTree* lpt()             { return _lpt; }
 236   PhiNode* iv()                    { return _iv; }
 237 
 238  private:
 239   IdealLoopTree* _lpt;             // Current loop tree node
 240   LoopNode*      _lp;              // Current LoopNode
 241   Node*          _bb;              // Current basic block
 242   PhiNode*       _iv;              // Induction var
 243 
 244   // Accessors
 245   Arena* arena()                   { return _arena; }
 246 
 247   Node* bb()                       { return _bb; }
 248   void  set_bb(Node* bb)           { _bb = bb; }
 249 
 250   void set_lpt(IdealLoopTree* lpt) { _lpt = lpt; }
 251 
 252   LoopNode* lp()                   { return _lp; }
 253   void      set_lp(LoopNode* lp)   { _lp = lp;
 254                                      _iv = lp->as_CountedLoop()->phi()->as_Phi(); }
 255   int      iv_stride()             { return lp()->as_CountedLoop()->stride_con(); }
 256 
 257   int vector_width_in_bytes()      { return Matcher::vector_width_in_bytes(); }
 258 
 259   MemNode* align_to_ref()            { return _align_to_ref; }
 260   void  set_align_to_ref(MemNode* m) { _align_to_ref = m; }
 261 
 262   Node* ctrl(Node* n) const { return _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n; }
 263 
 264   // block accessors
 265   bool in_bb(Node* n)      { return n != NULL && n->outcnt() > 0 && ctrl(n) == _bb; }
 266   int  bb_idx(Node* n)     { assert(in_bb(n), "must be"); return _bb_idx.at(n->_idx); }
 267   void set_bb_idx(Node* n, int i) { _bb_idx.at_put_grow(n->_idx, i); }
 268 
 269   // visited set accessors
 270   void visited_clear()           { _visited.Clear(); }
 271   void visited_set(Node* n)      { return _visited.set(bb_idx(n)); }
 272   int visited_test(Node* n)      { return _visited.test(bb_idx(n)); }
 273   int visited_test_set(Node* n)  { return _visited.test_set(bb_idx(n)); }
 274   void post_visited_clear()      { _post_visited.Clear(); }
 275   void post_visited_set(Node* n) { return _post_visited.set(bb_idx(n)); }
 276   int post_visited_test(Node* n) { return _post_visited.test(bb_idx(n)); }
 277 
 278   // Ensure node_info contains element "i"
 279   void grow_node_info(int i) { if (i >= _node_info.length()) _node_info.at_put_grow(i, SWNodeInfo::initial); }
 280 
 281   // memory alignment for a node
 282   int alignment(Node* n)                     { return _node_info.adr_at(bb_idx(n))->_alignment; }
 283   void set_alignment(Node* n, int a)         { int i = bb_idx(n); grow_node_info(i); _node_info.adr_at(i)->_alignment = a; }
 284 
 285   // Max expression (DAG) depth from beginning of the block for each node
 286   int depth(Node* n)                         { return _node_info.adr_at(bb_idx(n))->_depth; }
 287   void set_depth(Node* n, int d)             { int i = bb_idx(n); grow_node_info(i); _node_info.adr_at(i)->_depth = d; }
 288 
 289   // vector element type
 290   const Type* velt_type(Node* n)             { return _node_info.adr_at(bb_idx(n))->_velt_type; }
 291   void set_velt_type(Node* n, const Type* t) { int i = bb_idx(n); grow_node_info(i); _node_info.adr_at(i)->_velt_type = t; }
 292 
 293   // my_pack
 294   Node_List* my_pack(Node* n)                { return !in_bb(n) ? NULL : _node_info.adr_at(bb_idx(n))->_my_pack; }
 295   void set_my_pack(Node* n, Node_List* p)    { int i = bb_idx(n); grow_node_info(i); _node_info.adr_at(i)->_my_pack = p; }
 296 
 297   // methods
 298 
 299   // Extract the superword level parallelism
 300   void SLP_extract();
 301   // Find the adjacent memory references and create pack pairs for them.
 302   void find_adjacent_refs();
 303   // Find a memory reference to align the loop induction variable to.
 304   void find_align_to_ref(Node_List &memops);
 305   // Can the preloop align the reference to position zero in the vector?
 306   bool ref_is_alignable(SWPointer& p);
 307   // Construct dependency graph.
 308   void dependence_graph();
 309   // Return a memory slice (node list) in predecessor order starting at "start"
 310   void mem_slice_preds(Node* start, Node* stop, GrowableArray<Node*> &preds);
 311   // Can s1 and s2 be in a pack with s1 immediately preceding s2 and  s1 aligned at "align"
 312   bool stmts_can_pack(Node* s1, Node* s2, int align);
 313   // Does s exist in a pack at position pos?
 314   bool exists_at(Node* s, uint pos);
 315   // Is s1 immediately before s2 in memory?
 316   bool are_adjacent_refs(Node* s1, Node* s2);
 317   // Are s1 and s2 similar?
 318   bool isomorphic(Node* s1, Node* s2);
 319   // Is there no data path from s1 to s2 or s2 to s1?
 320   bool independent(Node* s1, Node* s2);
 321   // Helper for independent
 322   bool independent_path(Node* shallow, Node* deep, uint dp=0);
 323   void set_alignment(Node* s1, Node* s2, int align);
 324   int data_size(Node* s);
 325   // Extend packset by following use->def and def->use links from pack members.
 326   void extend_packlist();
 327   // Extend the packset by visiting operand definitions of nodes in pack p
 328   bool follow_use_defs(Node_List* p);
 329   // Extend the packset by visiting uses of nodes in pack p
 330   bool follow_def_uses(Node_List* p);
 331   // Estimate the savings from executing s1 and s2 as a pack
 332   int est_savings(Node* s1, Node* s2);
 333   int adjacent_profit(Node* s1, Node* s2);
 334   int pack_cost(int ct);
 335   int unpack_cost(int ct);
 336   // Combine packs A and B with A.last == B.first into A.first..,A.last,B.second,..B.last
 337   void combine_packs();
 338   // Construct the map from nodes to packs.
 339   void construct_my_pack_map();
 340   // Remove packs that are not implemented or not profitable.
 341   void filter_packs();
 342   // Adjust the memory graph for the packed operations
 343   void schedule();
 344   // Remove "current" from its current position in the memory graph and insert
 345   // it after the appropriate insert points (lip or uip);
 346   void remove_and_insert(MemNode *current, MemNode *prev, MemNode *lip, Node *uip, Unique_Node_List &schd_before);
 347   // Within a store pack, schedule stores together by moving out the sandwiched memory ops according
 348   // to dependence info; and within a load pack, move loads down to the last executed load.
 349   void co_locate_pack(Node_List* p);
 350   // Convert packs into vector node operations
 351   void output();
 352   // Create a vector operand for the nodes in pack p for operand: in(opd_idx)
 353   VectorNode* vector_opd(Node_List* p, int opd_idx);
 354   // Can code be generated for pack p?
 355   bool implemented(Node_List* p);
 356   // For pack p, are all operands and all uses (with in the block) vector?
 357   bool profitable(Node_List* p);
 358   // If a use of pack p is not a vector use, then replace the use with an extract operation.
 359   void insert_extracts(Node_List* p);
 360   // Is use->in(u_idx) a vector use?
 361   bool is_vector_use(Node* use, int u_idx);
 362   // Construct reverse postorder list of block members
 363   void construct_bb();
 364   // Initialize per node info
 365   void initialize_bb();
 366   // Insert n into block after pos
 367   void bb_insert_after(Node* n, int pos);
 368   // Compute max depth for expressions from beginning of block
 369   void compute_max_depth();
 370   // Compute necessary vector element type for expressions
 371   void compute_vector_element_type();
 372   // Are s1 and s2 in a pack pair and ordered as s1,s2?
 373   bool in_packset(Node* s1, Node* s2);
 374   // Is s in pack p?
 375   Node_List* in_pack(Node* s, Node_List* p);
 376   // Remove the pack at position pos in the packset
 377   void remove_pack_at(int pos);
 378   // Return the node executed first in pack p.
 379   Node* executed_first(Node_List* p);
 380   // Return the node executed last in pack p.
 381   Node* executed_last(Node_List* p);
 382   // Alignment within a vector memory reference
 383   int memory_alignment(MemNode* s, int iv_adjust_in_bytes);
 384   // (Start, end] half-open range defining which operands are vector
 385   void vector_opd_range(Node* n, uint* start, uint* end);
 386   // Smallest type containing range of values
 387   static const Type* container_type(const Type* t);
 388   // Adjust pre-loop limit so that in main loop, a load/store reference
 389   // to align_to_ref will be a position zero in the vector.
 390   void align_initial_loop_index(MemNode* align_to_ref);
 391   // Find pre loop end from main loop.  Returns null if none.
 392   CountedLoopEndNode* get_pre_loop_end(CountedLoopNode *cl);
 393   // Is the use of d1 in u1 at the same operand position as d2 in u2?
 394   bool opnd_positions_match(Node* d1, Node* u1, Node* d2, Node* u2);
 395   void init();
 396 
 397   // print methods
 398   void print_packset();
 399   void print_pack(Node_List* p);
 400   void print_bb();
 401   void print_stmt(Node* s);
 402   char* blank(uint depth);
 403 };
 404 
 405 
 406 //------------------------------SWPointer---------------------------
 407 // Information about an address for dependence checking and vector alignment
 408 class SWPointer VALUE_OBJ_CLASS_SPEC {
 409  protected:
 410   MemNode*   _mem;     // My memory reference node
 411   SuperWord* _slp;     // SuperWord class
 412 
 413   Node* _base;         // NULL if unsafe nonheap reference
 414   Node* _adr;          // address pointer
 415   jint  _scale;        // multipler for iv (in bytes), 0 if no loop iv
 416   jint  _offset;       // constant offset (in bytes)
 417   Node* _invar;        // invariant offset (in bytes), NULL if none
 418   bool  _negate_invar; // if true then use: (0 - _invar)
 419 
 420   PhaseIdealLoop* phase() { return _slp->phase(); }
 421   IdealLoopTree*  lpt()   { return _slp->lpt(); }
 422   PhiNode*        iv()    { return _slp->iv();  } // Induction var
 423 
 424   bool invariant(Node* n) {
 425     Node *n_c = phase()->get_ctrl(n);
 426     return !lpt()->is_member(phase()->get_loop(n_c));
 427   }
 428 
 429   // Match: k*iv + offset
 430   bool scaled_iv_plus_offset(Node* n);
 431   // Match: k*iv where k is a constant that's not zero
 432   bool scaled_iv(Node* n);
 433   // Match: offset is (k [+/- invariant])
 434   bool offset_plus_k(Node* n, bool negate = false);
 435 
 436  public:
 437   enum CMP {
 438     Less          = 1,
 439     Greater       = 2,
 440     Equal         = 4,
 441     NotEqual      = (Less | Greater),
 442     NotComparable = (Less | Greater | Equal)
 443   };
 444 
 445   SWPointer(MemNode* mem, SuperWord* slp);
 446   // Following is used to create a temporary object during
 447   // the pattern match of an address expression.
 448   SWPointer(SWPointer* p);
 449 
 450   bool valid()  { return _adr != NULL; }
 451   bool has_iv() { return _scale != 0; }
 452 
 453   Node* base()            { return _base; }
 454   Node* adr()             { return _adr; }
 455   int   scale_in_bytes()  { return _scale; }
 456   Node* invar()           { return _invar; }
 457   bool  negate_invar()    { return _negate_invar; }
 458   int   offset_in_bytes() { return _offset; }
 459   int   memory_size()     { return _mem->memory_size(); }
 460 
 461   // Comparable?
 462   int cmp(SWPointer& q) {
 463     if (valid() && q.valid() &&
 464         (_adr == q._adr || _base == _adr && q._base == q._adr) &&
 465         _scale == q._scale   &&
 466         _invar == q._invar   &&
 467         _negate_invar == q._negate_invar) {
 468       bool overlap = q._offset <   _offset +   memory_size() &&
 469                        _offset < q._offset + q.memory_size();
 470       return overlap ? Equal : (_offset < q._offset ? Less : Greater);
 471     } else {
 472       return NotComparable;
 473     }
 474   }
 475 
 476   bool not_equal(SWPointer& q)    { return not_equal(cmp(q)); }
 477   bool equal(SWPointer& q)        { return equal(cmp(q)); }
 478   bool comparable(SWPointer& q)   { return comparable(cmp(q)); }
 479   static bool not_equal(int cmp)  { return cmp <= NotEqual; }
 480   static bool equal(int cmp)      { return cmp == Equal; }
 481   static bool comparable(int cmp) { return cmp < NotComparable; }
 482 
 483   void print();
 484 };
 485 
 486 
 487 //------------------------------OrderedPair---------------------------
 488 // Ordered pair of Node*.
 489 class OrderedPair VALUE_OBJ_CLASS_SPEC {
 490  protected:
 491   Node* _p1;
 492   Node* _p2;
 493  public:
 494   OrderedPair() : _p1(NULL), _p2(NULL) {}
 495   OrderedPair(Node* p1, Node* p2) {
 496     if (p1->_idx < p2->_idx) {
 497       _p1 = p1; _p2 = p2;
 498     } else {
 499       _p1 = p2; _p2 = p1;
 500     }
 501   }
 502 
 503   bool operator==(const OrderedPair &rhs) {
 504     return _p1 == rhs._p1 && _p2 == rhs._p2;
 505   }
 506   void print() { tty->print("  (%d, %d)", _p1->_idx, _p2->_idx); }
 507 
 508   static const OrderedPair initial;
 509 };