src/share/vm/opto/block.hpp

Tue, 03 Aug 2010 15:55:03 -0700

author
kvn
date
Tue, 03 Aug 2010 15:55:03 -0700
changeset 2040
0e35fa8ebccd
parent 1907
c18cbe5936b8
child 2314
f95d63e2154a
permissions
-rw-r--r--

6973963: SEGV in ciBlock::start_bci() with EA
Summary: Added more checks into ResourceObj and growableArray to verify correctness of allocation type.
Reviewed-by: never, coleenp, dholmes

     1 /*
     2  * Copyright (c) 1997, 2009, 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  */
    25 // Optimization - Graph Style
    27 class Block;
    28 class CFGLoop;
    29 class MachCallNode;
    30 class Matcher;
    31 class RootNode;
    32 class VectorSet;
    33 struct Tarjan;
    35 //------------------------------Block_Array------------------------------------
    36 // Map dense integer indices to Blocks.  Uses classic doubling-array trick.
    37 // Abstractly provides an infinite array of Block*'s, initialized to NULL.
    38 // Note that the constructor just zeros things, and since I use Arena
    39 // allocation I do not need a destructor to reclaim storage.
    40 class Block_Array : public ResourceObj {
    41   uint _size;                   // allocated size, as opposed to formal limit
    42   debug_only(uint _limit;)      // limit to formal domain
    43 protected:
    44   Block **_blocks;
    45   void grow( uint i );          // Grow array node to fit
    47 public:
    48   Arena *_arena;                // Arena to allocate in
    50   Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) {
    51     debug_only(_limit=0);
    52     _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );
    53     for( int i = 0; i < OptoBlockListSize; i++ ) {
    54       _blocks[i] = NULL;
    55     }
    56   }
    57   Block *lookup( uint i ) const // Lookup, or NULL for not mapped
    58   { return (i<Max()) ? _blocks[i] : (Block*)NULL; }
    59   Block *operator[] ( uint i ) const // Lookup, or assert for not mapped
    60   { assert( i < Max(), "oob" ); return _blocks[i]; }
    61   // Extend the mapping: index i maps to Block *n.
    62   void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; }
    63   uint Max() const { debug_only(return _limit); return _size; }
    64 };
    67 class Block_List : public Block_Array {
    68 public:
    69   uint _cnt;
    70   Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}
    71   void push( Block *b ) { map(_cnt++,b); }
    72   Block *pop() { return _blocks[--_cnt]; }
    73   Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}
    74   void remove( uint i );
    75   void insert( uint i, Block *n );
    76   uint size() const { return _cnt; }
    77   void reset() { _cnt = 0; }
    78   void print();
    79 };
    82 class CFGElement : public ResourceObj {
    83  public:
    84   float _freq; // Execution frequency (estimate)
    86   CFGElement() : _freq(0.0f) {}
    87   virtual bool is_block() { return false; }
    88   virtual bool is_loop()  { return false; }
    89   Block*   as_Block() { assert(is_block(), "must be block"); return (Block*)this; }
    90   CFGLoop* as_CFGLoop()  { assert(is_loop(),  "must be loop");  return (CFGLoop*)this;  }
    91 };
    93 //------------------------------Block------------------------------------------
    94 // This class defines a Basic Block.
    95 // Basic blocks are used during the output routines, and are not used during
    96 // any optimization pass.  They are created late in the game.
    97 class Block : public CFGElement {
    98  public:
    99   // Nodes in this block, in order
   100   Node_List _nodes;
   102   // Basic blocks have a Node which defines Control for all Nodes pinned in
   103   // this block.  This Node is a RegionNode.  Exception-causing Nodes
   104   // (division, subroutines) and Phi functions are always pinned.  Later,
   105   // every Node will get pinned to some block.
   106   Node *head() const { return _nodes[0]; }
   108   // CAUTION: num_preds() is ONE based, so that predecessor numbers match
   109   // input edges to Regions and Phis.
   110   uint num_preds() const { return head()->req(); }
   111   Node *pred(uint i) const { return head()->in(i); }
   113   // Array of successor blocks, same size as projs array
   114   Block_Array _succs;
   116   // Basic blocks have some number of Nodes which split control to all
   117   // following blocks.  These Nodes are always Projections.  The field in
   118   // the Projection and the block-ending Node determine which Block follows.
   119   uint _num_succs;
   121   // Basic blocks also carry all sorts of good old fashioned DFS information
   122   // used to find loops, loop nesting depth, dominators, etc.
   123   uint _pre_order;              // Pre-order DFS number
   125   // Dominator tree
   126   uint _dom_depth;              // Depth in dominator tree for fast LCA
   127   Block* _idom;                 // Immediate dominator block
   129   CFGLoop *_loop;               // Loop to which this block belongs
   130   uint _rpo;                    // Number in reverse post order walk
   132   virtual bool is_block() { return true; }
   133   float succ_prob(uint i);      // return probability of i'th successor
   134   int num_fall_throughs();      // How many fall-through candidate this block has
   135   void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code
   136   bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate
   137   Block* lone_fall_through();   // Return lone fall-through Block or null
   139   Block* dom_lca(Block* that);  // Compute LCA in dominator tree.
   140 #ifdef ASSERT
   141   bool dominates(Block* that) {
   142     int dom_diff = this->_dom_depth - that->_dom_depth;
   143     if (dom_diff > 0)  return false;
   144     for (; dom_diff < 0; dom_diff++)  that = that->_idom;
   145     return this == that;
   146   }
   147 #endif
   149   // Report the alignment required by this block.  Must be a power of 2.
   150   // The previous block will insert nops to get this alignment.
   151   uint code_alignment();
   152   uint compute_loop_alignment();
   154   // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
   155   // It is currently also used to scale such frequencies relative to
   156   // FreqCountInvocations relative to the old value of 1500.
   157 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations)
   159   // Register Pressure (estimate) for Splitting heuristic
   160   uint _reg_pressure;
   161   uint _ihrp_index;
   162   uint _freg_pressure;
   163   uint _fhrp_index;
   165   // Mark and visited bits for an LCA calculation in insert_anti_dependences.
   166   // Since they hold unique node indexes, they do not need reinitialization.
   167   node_idx_t _raise_LCA_mark;
   168   void    set_raise_LCA_mark(node_idx_t x)    { _raise_LCA_mark = x; }
   169   node_idx_t  raise_LCA_mark() const          { return _raise_LCA_mark; }
   170   node_idx_t _raise_LCA_visited;
   171   void    set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }
   172   node_idx_t  raise_LCA_visited() const       { return _raise_LCA_visited; }
   174   // Estimated size in bytes of first instructions in a loop.
   175   uint _first_inst_size;
   176   uint first_inst_size() const     { return _first_inst_size; }
   177   void set_first_inst_size(uint s) { _first_inst_size = s; }
   179   // Compute the size of first instructions in this block.
   180   uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
   182   // Compute alignment padding if the block needs it.
   183   // Align a loop if loop's padding is less or equal to padding limit
   184   // or the size of first instructions in the loop > padding.
   185   uint alignment_padding(int current_offset) {
   186     int block_alignment = code_alignment();
   187     int max_pad = block_alignment-relocInfo::addr_unit();
   188     if( max_pad > 0 ) {
   189       assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");
   190       int current_alignment = current_offset & max_pad;
   191       if( current_alignment != 0 ) {
   192         uint padding = (block_alignment-current_alignment) & max_pad;
   193         if( has_loop_alignment() &&
   194             padding > (uint)MaxLoopPad &&
   195             first_inst_size() <= padding ) {
   196           return 0;
   197         }
   198         return padding;
   199       }
   200     }
   201     return 0;
   202   }
   204   // Connector blocks. Connector blocks are basic blocks devoid of
   205   // instructions, but may have relevant non-instruction Nodes, such as
   206   // Phis or MergeMems. Such blocks are discovered and marked during the
   207   // RemoveEmpty phase, and elided during Output.
   208   bool _connector;
   209   void set_connector() { _connector = true; }
   210   bool is_connector() const { return _connector; };
   212   // Loop_alignment will be set for blocks which are at the top of loops.
   213   // The block layout pass may rotate loops such that the loop head may not
   214   // be the sequentially first block of the loop encountered in the linear
   215   // list of blocks.  If the layout pass is not run, loop alignment is set
   216   // for each block which is the head of a loop.
   217   uint _loop_alignment;
   218   void set_loop_alignment(Block *loop_top) {
   219     uint new_alignment = loop_top->compute_loop_alignment();
   220     if (new_alignment > _loop_alignment) {
   221       _loop_alignment = new_alignment;
   222     }
   223   }
   224   uint loop_alignment() const { return _loop_alignment; }
   225   bool has_loop_alignment() const { return loop_alignment() > 0; }
   227   // Create a new Block with given head Node.
   228   // Creates the (empty) predecessor arrays.
   229   Block( Arena *a, Node *headnode )
   230     : CFGElement(),
   231       _nodes(a),
   232       _succs(a),
   233       _num_succs(0),
   234       _pre_order(0),
   235       _idom(0),
   236       _loop(NULL),
   237       _reg_pressure(0),
   238       _ihrp_index(1),
   239       _freg_pressure(0),
   240       _fhrp_index(1),
   241       _raise_LCA_mark(0),
   242       _raise_LCA_visited(0),
   243       _first_inst_size(999999),
   244       _connector(false),
   245       _loop_alignment(0) {
   246     _nodes.push(headnode);
   247   }
   249   // Index of 'end' Node
   250   uint end_idx() const {
   251     // %%%%% add a proj after every goto
   252     // so (last->is_block_proj() != last) always, then simplify this code
   253     // This will not give correct end_idx for block 0 when it only contains root.
   254     int last_idx = _nodes.size() - 1;
   255     Node *last  = _nodes[last_idx];
   256     assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");
   257     return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);
   258   }
   260   // Basic blocks have a Node which ends them.  This Node determines which
   261   // basic block follows this one in the program flow.  This Node is either an
   262   // IfNode, a GotoNode, a JmpNode, or a ReturnNode.
   263   Node *end() const { return _nodes[end_idx()]; }
   265   // Add an instruction to an existing block.  It must go after the head
   266   // instruction and before the end instruction.
   267   void add_inst( Node *n ) { _nodes.insert(end_idx(),n); }
   268   // Find node in block
   269   uint find_node( const Node *n ) const;
   270   // Find and remove n from block list
   271   void find_remove( const Node *n );
   273   // Schedule a call next in the block
   274   uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call);
   276   // Perform basic-block local scheduling
   277   Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot);
   278   void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );
   279   void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);
   280   bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call);
   281   // Cleanup if any code lands between a Call and his Catch
   282   void call_catch_cleanup(Block_Array &bbs);
   283   // Detect implicit-null-check opportunities.  Basically, find NULL checks
   284   // with suitable memory ops nearby.  Use the memory op to do the NULL check.
   285   // I can generate a memory op if there is not one nearby.
   286   void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);
   288   // Return the empty status of a block
   289   enum { not_empty, empty_with_goto, completely_empty };
   290   int is_Empty() const;
   292   // Forward through connectors
   293   Block* non_connector() {
   294     Block* s = this;
   295     while (s->is_connector()) {
   296       s = s->_succs[0];
   297     }
   298     return s;
   299   }
   301   // Return true if b is a successor of this block
   302   bool has_successor(Block* b) const {
   303     for (uint i = 0; i < _num_succs; i++ ) {
   304       if (non_connector_successor(i) == b) {
   305         return true;
   306       }
   307     }
   308     return false;
   309   }
   311   // Successor block, after forwarding through connectors
   312   Block* non_connector_successor(int i) const {
   313     return _succs[i]->non_connector();
   314   }
   316   // Examine block's code shape to predict if it is not commonly executed.
   317   bool has_uncommon_code() const;
   319   // Use frequency calculations and code shape to predict if the block
   320   // is uncommon.
   321   bool is_uncommon( Block_Array &bbs ) const;
   323 #ifndef PRODUCT
   324   // Debugging print of basic block
   325   void dump_bidx(const Block* orig) const;
   326   void dump_pred(const Block_Array *bbs, Block* orig) const;
   327   void dump_head( const Block_Array *bbs ) const;
   328   void dump( ) const;
   329   void dump( const Block_Array *bbs ) const;
   330 #endif
   331 };
   334 //------------------------------PhaseCFG---------------------------------------
   335 // Build an array of Basic Block pointers, one per Node.
   336 class PhaseCFG : public Phase {
   337  private:
   338   // Build a proper looking cfg.  Return count of basic blocks
   339   uint build_cfg();
   341   // Perform DFS search.
   342   // Setup 'vertex' as DFS to vertex mapping.
   343   // Setup 'semi' as vertex to DFS mapping.
   344   // Set 'parent' to DFS parent.
   345   uint DFS( Tarjan *tarjan );
   347   // Helper function to insert a node into a block
   348   void schedule_node_into_block( Node *n, Block *b );
   350   void replace_block_proj_ctrl( Node *n );
   352   // Set the basic block for pinned Nodes
   353   void schedule_pinned_nodes( VectorSet &visited );
   355   // I'll need a few machine-specific GotoNodes.  Clone from this one.
   356   MachNode *_goto;
   358   Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
   359   void verify_anti_dependences(Block* LCA, Node* load) {
   360     assert(LCA == _bbs[load->_idx], "should already be scheduled");
   361     insert_anti_dependences(LCA, load, true);
   362   }
   364  public:
   365   PhaseCFG( Arena *a, RootNode *r, Matcher &m );
   367   uint _num_blocks;             // Count of basic blocks
   368   Block_List _blocks;           // List of basic blocks
   369   RootNode *_root;              // Root of whole program
   370   Block_Array _bbs;             // Map Nodes to owning Basic Block
   371   Block *_broot;                // Basic block of root
   372   uint _rpo_ctr;
   373   CFGLoop* _root_loop;
   374   float _outer_loop_freq;       // Outmost loop frequency
   376   // Per node latency estimation, valid only during GCM
   377   GrowableArray<uint> *_node_latency;
   379 #ifndef PRODUCT
   380   bool _trace_opto_pipelining;  // tracing flag
   381 #endif
   383 #ifdef ASSERT
   384   Unique_Node_List _raw_oops;
   385 #endif
   387   // Build dominators
   388   void Dominators();
   390   // Estimate block frequencies based on IfNode probabilities
   391   void Estimate_Block_Frequency();
   393   // Global Code Motion.  See Click's PLDI95 paper.  Place Nodes in specific
   394   // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.
   395   void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );
   397   // Compute the (backwards) latency of a node from the uses
   398   void latency_from_uses(Node *n);
   400   // Compute the (backwards) latency of a node from a single use
   401   int latency_from_use(Node *n, const Node *def, Node *use);
   403   // Compute the (backwards) latency of a node from the uses of this instruction
   404   void partial_latency_of_defs(Node *n);
   406   // Schedule Nodes early in their basic blocks.
   407   bool schedule_early(VectorSet &visited, Node_List &roots);
   409   // For each node, find the latest block it can be scheduled into
   410   // and then select the cheapest block between the latest and earliest
   411   // block to place the node.
   412   void schedule_late(VectorSet &visited, Node_List &stack);
   414   // Pick a block between early and late that is a cheaper alternative
   415   // to late. Helper for schedule_late.
   416   Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
   418   // Compute the instruction global latency with a backwards walk
   419   void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);
   421   // Set loop alignment
   422   void set_loop_alignment();
   424   // Remove empty basic blocks
   425   void remove_empty();
   426   void fixup_flow();
   427   bool move_to_next(Block* bx, uint b_index);
   428   void move_to_end(Block* bx, uint b_index);
   429   void insert_goto_at(uint block_no, uint succ_no);
   431   // Check for NeverBranch at block end.  This needs to become a GOTO to the
   432   // true target.  NeverBranch are treated as a conditional branch that always
   433   // goes the same direction for most of the optimizer and are used to give a
   434   // fake exit path to infinite loops.  At this late stage they need to turn
   435   // into Goto's so that when you enter the infinite loop you indeed hang.
   436   void convert_NeverBranch_to_Goto(Block *b);
   438   CFGLoop* create_loop_tree();
   440   // Insert a node into a block, and update the _bbs
   441   void insert( Block *b, uint idx, Node *n ) {
   442     b->_nodes.insert( idx, n );
   443     _bbs.map( n->_idx, b );
   444   }
   446 #ifndef PRODUCT
   447   bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
   449   // Debugging print of CFG
   450   void dump( ) const;           // CFG only
   451   void _dump_cfg( const Node *end, VectorSet &visited  ) const;
   452   void verify() const;
   453   void dump_headers();
   454 #else
   455   bool trace_opto_pipelining() const { return false; }
   456 #endif
   457 };
   460 //------------------------------UnionFind--------------------------------------
   461 // Map Block indices to a block-index for a cfg-cover.
   462 // Array lookup in the optimized case.
   463 class UnionFind : public ResourceObj {
   464   uint _cnt, _max;
   465   uint* _indices;
   466   ReallocMark _nesting;  // assertion check for reallocations
   467 public:
   468   UnionFind( uint max );
   469   void reset( uint max );  // Reset to identity map for [0..max]
   471   uint lookup( uint nidx ) const {
   472     return _indices[nidx];
   473   }
   474   uint operator[] (uint nidx) const { return lookup(nidx); }
   476   void map( uint from_idx, uint to_idx ) {
   477     assert( from_idx < _cnt, "oob" );
   478     _indices[from_idx] = to_idx;
   479   }
   480   void extend( uint from_idx, uint to_idx );
   482   uint Size() const { return _cnt; }
   484   uint Find( uint idx ) {
   485     assert( idx < 65536, "Must fit into uint");
   486     uint uf_idx = lookup(idx);
   487     return (uf_idx == idx) ? uf_idx : Find_compress(idx);
   488   }
   489   uint Find_compress( uint idx );
   490   uint Find_const( uint idx ) const;
   491   void Union( uint idx1, uint idx2 );
   493 };
   495 //----------------------------BlockProbPair---------------------------
   496 // Ordered pair of Node*.
   497 class BlockProbPair VALUE_OBJ_CLASS_SPEC {
   498 protected:
   499   Block* _target;      // block target
   500   float  _prob;        // probability of edge to block
   501 public:
   502   BlockProbPair() : _target(NULL), _prob(0.0) {}
   503   BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}
   505   Block* get_target() const { return _target; }
   506   float get_prob() const { return _prob; }
   507 };
   509 //------------------------------CFGLoop-------------------------------------------
   510 class CFGLoop : public CFGElement {
   511   int _id;
   512   int _depth;
   513   CFGLoop *_parent;      // root of loop tree is the method level "pseudo" loop, it's parent is null
   514   CFGLoop *_sibling;     // null terminated list
   515   CFGLoop *_child;       // first child, use child's sibling to visit all immediately nested loops
   516   GrowableArray<CFGElement*> _members; // list of members of loop
   517   GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
   518   float _exit_prob;       // probability any loop exit is taken on a single loop iteration
   519   void update_succ_freq(Block* b, float freq);
   521  public:
   522   CFGLoop(int id) :
   523     CFGElement(),
   524     _id(id),
   525     _depth(0),
   526     _parent(NULL),
   527     _sibling(NULL),
   528     _child(NULL),
   529     _exit_prob(1.0f) {}
   530   CFGLoop* parent() { return _parent; }
   531   void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk);
   532   void add_member(CFGElement *s) { _members.push(s); }
   533   void add_nested_loop(CFGLoop* cl);
   534   Block* head() {
   535     assert(_members.at(0)->is_block(), "head must be a block");
   536     Block* hd = _members.at(0)->as_Block();
   537     assert(hd->_loop == this, "just checking");
   538     assert(hd->head()->is_Loop(), "must begin with loop head node");
   539     return hd;
   540   }
   541   Block* backedge_block(); // Return the block on the backedge of the loop (else NULL)
   542   void compute_loop_depth(int depth);
   543   void compute_freq(); // compute frequency with loop assuming head freq 1.0f
   544   void scale_freq();   // scale frequency by loop trip count (including outer loops)
   545   float outer_loop_freq() const; // frequency of outer loop
   546   bool in_loop_nest(Block* b);
   547   float trip_count() const { return 1.0f / _exit_prob; }
   548   virtual bool is_loop()  { return true; }
   549   int id() { return _id; }
   551 #ifndef PRODUCT
   552   void dump( ) const;
   553   void dump_tree() const;
   554 #endif
   555 };
   558 //----------------------------------CFGEdge------------------------------------
   559 // A edge between two basic blocks that will be embodied by a branch or a
   560 // fall-through.
   561 class CFGEdge : public ResourceObj {
   562  private:
   563   Block * _from;        // Source basic block
   564   Block * _to;          // Destination basic block
   565   float _freq;          // Execution frequency (estimate)
   566   int   _state;
   567   bool  _infrequent;
   568   int   _from_pct;
   569   int   _to_pct;
   571   // Private accessors
   572   int  from_pct() const { return _from_pct; }
   573   int  to_pct()   const { return _to_pct;   }
   574   int  from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; }
   575   int  to_infrequent()   const { return to_pct()   < BlockLayoutMinDiamondPercentage; }
   577  public:
   578   enum {
   579     open,               // initial edge state; unprocessed
   580     connected,          // edge used to connect two traces together
   581     interior            // edge is interior to trace (could be backedge)
   582   };
   584   CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) :
   585     _from(from), _to(to), _freq(freq),
   586     _from_pct(from_pct), _to_pct(to_pct), _state(open) {
   587     _infrequent = from_infrequent() || to_infrequent();
   588   }
   590   float  freq() const { return _freq; }
   591   Block* from() const { return _from; }
   592   Block* to  () const { return _to;   }
   593   int  infrequent() const { return _infrequent; }
   594   int state() const { return _state; }
   596   void set_state(int state) { _state = state; }
   598 #ifndef PRODUCT
   599   void dump( ) const;
   600 #endif
   601 };
   604 //-----------------------------------Trace-------------------------------------
   605 // An ordered list of basic blocks.
   606 class Trace : public ResourceObj {
   607  private:
   608   uint _id;             // Unique Trace id (derived from initial block)
   609   Block ** _next_list;  // Array mapping index to next block
   610   Block ** _prev_list;  // Array mapping index to previous block
   611   Block * _first;       // First block in the trace
   612   Block * _last;        // Last block in the trace
   614   // Return the block that follows "b" in the trace.
   615   Block * next(Block *b) const { return _next_list[b->_pre_order]; }
   616   void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; }
   618   // Return the block that precedes "b" in the trace.
   619   Block * prev(Block *b) const { return _prev_list[b->_pre_order]; }
   620   void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; }
   622   // We've discovered a loop in this trace. Reset last to be "b", and first as
   623   // the block following "b
   624   void break_loop_after(Block *b) {
   625     _last = b;
   626     _first = next(b);
   627     set_prev(_first, NULL);
   628     set_next(_last, NULL);
   629   }
   631  public:
   633   Trace(Block *b, Block **next_list, Block **prev_list) :
   634     _first(b),
   635     _last(b),
   636     _next_list(next_list),
   637     _prev_list(prev_list),
   638     _id(b->_pre_order) {
   639     set_next(b, NULL);
   640     set_prev(b, NULL);
   641   };
   643   // Return the id number
   644   uint id() const { return _id; }
   645   void set_id(uint id) { _id = id; }
   647   // Return the first block in the trace
   648   Block * first_block() const { return _first; }
   650   // Return the last block in the trace
   651   Block * last_block() const { return _last; }
   653   // Insert a trace in the middle of this one after b
   654   void insert_after(Block *b, Trace *tr) {
   655     set_next(tr->last_block(), next(b));
   656     if (next(b) != NULL) {
   657       set_prev(next(b), tr->last_block());
   658     }
   660     set_next(b, tr->first_block());
   661     set_prev(tr->first_block(), b);
   663     if (b == _last) {
   664       _last = tr->last_block();
   665     }
   666   }
   668   void insert_before(Block *b, Trace *tr) {
   669     Block *p = prev(b);
   670     assert(p != NULL, "use append instead");
   671     insert_after(p, tr);
   672   }
   674   // Append another trace to this one.
   675   void append(Trace *tr) {
   676     insert_after(_last, tr);
   677   }
   679   // Append a block at the end of this trace
   680   void append(Block *b) {
   681     set_next(_last, b);
   682     set_prev(b, _last);
   683     _last = b;
   684   }
   686   // Adjust the the blocks in this trace
   687   void fixup_blocks(PhaseCFG &cfg);
   688   bool backedge(CFGEdge *e);
   690 #ifndef PRODUCT
   691   void dump( ) const;
   692 #endif
   693 };
   695 //------------------------------PhaseBlockLayout-------------------------------
   696 // Rearrange blocks into some canonical order, based on edges and their frequencies
   697 class PhaseBlockLayout : public Phase {
   698   PhaseCFG &_cfg;               // Control flow graph
   700   GrowableArray<CFGEdge *> *edges;
   701   Trace **traces;
   702   Block **next;
   703   Block **prev;
   704   UnionFind *uf;
   706   // Given a block, find its encompassing Trace
   707   Trace * trace(Block *b) {
   708     return traces[uf->Find_compress(b->_pre_order)];
   709   }
   710  public:
   711   PhaseBlockLayout(PhaseCFG &cfg);
   713   void find_edges();
   714   void grow_traces();
   715   void merge_traces(bool loose_connections);
   716   void reorder_traces(int count);
   717   void union_traces(Trace* from, Trace* to);
   718 };

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