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.
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23 */
24
25 #ifndef SHARE_VM_OPTO_BLOCK_HPP
26 #define SHARE_VM_OPTO_BLOCK_HPP
27
28 #include "opto/multnode.hpp"
29 #include "opto/node.hpp"
30 #include "opto/phase.hpp"
31
32 // Optimization - Graph Style
33
34 class Block;
35 class CFGLoop;
36 class MachCallNode;
37 class Matcher;
38 class RootNode;
39 class VectorSet;
40 struct Tarjan;
41
42 //------------------------------Block_Array------------------------------------
43 // Map dense integer indices to Blocks. Uses classic doubling-array trick.
44 // Abstractly provides an infinite array of Block*'s, initialized to NULL.
45 // Note that the constructor just zeros things, and since I use Arena
46 // allocation I do not need a destructor to reclaim storage.
47 class Block_Array : public ResourceObj {
48 uint _size; // allocated size, as opposed to formal limit
49 debug_only(uint _limit;) // limit to formal domain
50 protected:
51 Block **_blocks;
52 void grow( uint i ); // Grow array node to fit
53
54 public:
55 Arena *_arena; // Arena to allocate in
56
57 Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) {
58 debug_only(_limit=0);
59 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );
60 for( int i = 0; i < OptoBlockListSize; i++ ) {
61 _blocks[i] = NULL;
62 }
63 }
64 Block *lookup( uint i ) const // Lookup, or NULL for not mapped
65 { return (i<Max()) ? _blocks[i] : (Block*)NULL; }
66 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped
67 { assert( i < Max(), "oob" ); return _blocks[i]; }
68 // Extend the mapping: index i maps to Block *n.
69 void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; }
70 uint Max() const { debug_only(return _limit); return _size; }
71 };
72
73
74 class Block_List : public Block_Array {
75 public:
76 uint _cnt;
77 Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}
78 void push( Block *b ) { map(_cnt++,b); }
79 Block *pop() { return _blocks[--_cnt]; }
80 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}
81 void remove( uint i );
82 void insert( uint i, Block *n );
83 uint size() const { return _cnt; }
84 void reset() { _cnt = 0; }
85 void print();
86 };
87
88
89 class CFGElement : public ResourceObj {
90 public:
91 float _freq; // Execution frequency (estimate)
92
93 CFGElement() : _freq(0.0f) {}
94 virtual bool is_block() { return false; }
95 virtual bool is_loop() { return false; }
96 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; }
97 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; }
98 };
99
100 //------------------------------Block------------------------------------------
101 // This class defines a Basic Block.
102 // Basic blocks are used during the output routines, and are not used during
103 // any optimization pass. They are created late in the game.
104 class Block : public CFGElement {
105 public:
106 // Nodes in this block, in order
107 Node_List _nodes;
108
109 // Basic blocks have a Node which defines Control for all Nodes pinned in
110 // this block. This Node is a RegionNode. Exception-causing Nodes
111 // (division, subroutines) and Phi functions are always pinned. Later,
112 // every Node will get pinned to some block.
113 Node *head() const { return _nodes[0]; }
114
115 // CAUTION: num_preds() is ONE based, so that predecessor numbers match
116 // input edges to Regions and Phis.
117 uint num_preds() const { return head()->req(); }
118 Node *pred(uint i) const { return head()->in(i); }
119
120 // Array of successor blocks, same size as projs array
121 Block_Array _succs;
122
123 // Basic blocks have some number of Nodes which split control to all
124 // following blocks. These Nodes are always Projections. The field in
125 // the Projection and the block-ending Node determine which Block follows.
126 uint _num_succs;
127
128 // Basic blocks also carry all sorts of good old fashioned DFS information
129 // used to find loops, loop nesting depth, dominators, etc.
130 uint _pre_order; // Pre-order DFS number
131
132 // Dominator tree
133 uint _dom_depth; // Depth in dominator tree for fast LCA
134 Block* _idom; // Immediate dominator block
135
136 CFGLoop *_loop; // Loop to which this block belongs
137 uint _rpo; // Number in reverse post order walk
138
139 virtual bool is_block() { return true; }
140 float succ_prob(uint i); // return probability of i'th successor
141 int num_fall_throughs(); // How many fall-through candidate this block has
142 void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code
143 bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate
144 Block* lone_fall_through(); // Return lone fall-through Block or null
145
146 Block* dom_lca(Block* that); // Compute LCA in dominator tree.
147 #ifdef ASSERT
148 bool dominates(Block* that) {
149 int dom_diff = this->_dom_depth - that->_dom_depth;
150 if (dom_diff > 0) return false;
151 for (; dom_diff < 0; dom_diff++) that = that->_idom;
152 return this == that;
153 }
154 #endif
155
156 // Report the alignment required by this block. Must be a power of 2.
157 // The previous block will insert nops to get this alignment.
158 uint code_alignment();
159 uint compute_loop_alignment();
160
161 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
162 // It is currently also used to scale such frequencies relative to
163 // FreqCountInvocations relative to the old value of 1500.
164 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations)
165
166 // Register Pressure (estimate) for Splitting heuristic
167 uint _reg_pressure;
168 uint _ihrp_index;
169 uint _freg_pressure;
170 uint _fhrp_index;
171
172 // Mark and visited bits for an LCA calculation in insert_anti_dependences.
173 // Since they hold unique node indexes, they do not need reinitialization.
174 node_idx_t _raise_LCA_mark;
175 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; }
176 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; }
177 node_idx_t _raise_LCA_visited;
178 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }
179 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; }
180
181 // Estimated size in bytes of first instructions in a loop.
182 uint _first_inst_size;
183 uint first_inst_size() const { return _first_inst_size; }
184 void set_first_inst_size(uint s) { _first_inst_size = s; }
185
186 // Compute the size of first instructions in this block.
187 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
188
189 // Compute alignment padding if the block needs it.
190 // Align a loop if loop's padding is less or equal to padding limit
191 // or the size of first instructions in the loop > padding.
192 uint alignment_padding(int current_offset) {
193 int block_alignment = code_alignment();
194 int max_pad = block_alignment-relocInfo::addr_unit();
195 if( max_pad > 0 ) {
196 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");
197 int current_alignment = current_offset & max_pad;
198 if( current_alignment != 0 ) {
199 uint padding = (block_alignment-current_alignment) & max_pad;
200 if( has_loop_alignment() &&
201 padding > (uint)MaxLoopPad &&
202 first_inst_size() <= padding ) {
203 return 0;
204 }
205 return padding;
206 }
207 }
208 return 0;
209 }
210
211 // Connector blocks. Connector blocks are basic blocks devoid of
212 // instructions, but may have relevant non-instruction Nodes, such as
213 // Phis or MergeMems. Such blocks are discovered and marked during the
214 // RemoveEmpty phase, and elided during Output.
215 bool _connector;
216 void set_connector() { _connector = true; }
217 bool is_connector() const { return _connector; };
218
219 // Loop_alignment will be set for blocks which are at the top of loops.
220 // The block layout pass may rotate loops such that the loop head may not
221 // be the sequentially first block of the loop encountered in the linear
222 // list of blocks. If the layout pass is not run, loop alignment is set
223 // for each block which is the head of a loop.
224 uint _loop_alignment;
225 void set_loop_alignment(Block *loop_top) {
226 uint new_alignment = loop_top->compute_loop_alignment();
227 if (new_alignment > _loop_alignment) {
228 _loop_alignment = new_alignment;
229 }
230 }
231 uint loop_alignment() const { return _loop_alignment; }
232 bool has_loop_alignment() const { return loop_alignment() > 0; }
233
234 // Create a new Block with given head Node.
235 // Creates the (empty) predecessor arrays.
236 Block( Arena *a, Node *headnode )
237 : CFGElement(),
238 _nodes(a),
239 _succs(a),
240 _num_succs(0),
241 _pre_order(0),
242 _idom(0),
243 _loop(NULL),
244 _reg_pressure(0),
245 _ihrp_index(1),
246 _freg_pressure(0),
247 _fhrp_index(1),
248 _raise_LCA_mark(0),
249 _raise_LCA_visited(0),
250 _first_inst_size(999999),
251 _connector(false),
252 _loop_alignment(0) {
253 _nodes.push(headnode);
254 }
255
256 // Index of 'end' Node
257 uint end_idx() const {
258 // %%%%% add a proj after every goto
259 // so (last->is_block_proj() != last) always, then simplify this code
260 // This will not give correct end_idx for block 0 when it only contains root.
261 int last_idx = _nodes.size() - 1;
262 Node *last = _nodes[last_idx];
263 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");
264 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);
265 }
266
267 // Basic blocks have a Node which ends them. This Node determines which
268 // basic block follows this one in the program flow. This Node is either an
269 // IfNode, a GotoNode, a JmpNode, or a ReturnNode.
270 Node *end() const { return _nodes[end_idx()]; }
271
272 // Add an instruction to an existing block. It must go after the head
273 // instruction and before the end instruction.
274 void add_inst( Node *n ) { _nodes.insert(end_idx(),n); }
275 // Find node in block
276 uint find_node( const Node *n ) const;
277 // Find and remove n from block list
278 void find_remove( const Node *n );
279
280 // Schedule a call next in the block
281 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call);
282
283 // Perform basic-block local scheduling
284 Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot);
285 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );
286 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);
287 bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call);
288 // Cleanup if any code lands between a Call and his Catch
289 void call_catch_cleanup(Block_Array &bbs);
290 // Detect implicit-null-check opportunities. Basically, find NULL checks
291 // with suitable memory ops nearby. Use the memory op to do the NULL check.
292 // I can generate a memory op if there is not one nearby.
293 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);
294
295 // Return the empty status of a block
296 enum { not_empty, empty_with_goto, completely_empty };
297 int is_Empty() const;
298
299 // Forward through connectors
300 Block* non_connector() {
301 Block* s = this;
302 while (s->is_connector()) {
303 s = s->_succs[0];
304 }
305 return s;
306 }
307
308 // Return true if b is a successor of this block
309 bool has_successor(Block* b) const {
310 for (uint i = 0; i < _num_succs; i++ ) {
311 if (non_connector_successor(i) == b) {
312 return true;
313 }
314 }
315 return false;
316 }
317
318 // Successor block, after forwarding through connectors
319 Block* non_connector_successor(int i) const {
320 return _succs[i]->non_connector();
321 }
322
323 // Examine block's code shape to predict if it is not commonly executed.
324 bool has_uncommon_code() const;
325
326 // Use frequency calculations and code shape to predict if the block
327 // is uncommon.
328 bool is_uncommon( Block_Array &bbs ) const;
329
330 #ifndef PRODUCT
331 // Debugging print of basic block
332 void dump_bidx(const Block* orig) const;
333 void dump_pred(const Block_Array *bbs, Block* orig) const;
334 void dump_head( const Block_Array *bbs ) const;
335 void dump( ) const;
336 void dump( const Block_Array *bbs ) const;
337 #endif
338 };
339
340
341 //------------------------------PhaseCFG---------------------------------------
342 // Build an array of Basic Block pointers, one per Node.
343 class PhaseCFG : public Phase {
344 private:
345 // Build a proper looking cfg. Return count of basic blocks
346 uint build_cfg();
347
348 // Perform DFS search.
349 // Setup 'vertex' as DFS to vertex mapping.
350 // Setup 'semi' as vertex to DFS mapping.
351 // Set 'parent' to DFS parent.
352 uint DFS( Tarjan *tarjan );
353
354 // Helper function to insert a node into a block
355 void schedule_node_into_block( Node *n, Block *b );
356
357 void replace_block_proj_ctrl( Node *n );
358
359 // Set the basic block for pinned Nodes
360 void schedule_pinned_nodes( VectorSet &visited );
361
362 // I'll need a few machine-specific GotoNodes. Clone from this one.
363 MachNode *_goto;
364
365 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
366 void verify_anti_dependences(Block* LCA, Node* load) {
367 assert(LCA == _bbs[load->_idx], "should already be scheduled");
368 insert_anti_dependences(LCA, load, true);
369 }
370
371 public:
372 PhaseCFG( Arena *a, RootNode *r, Matcher &m );
373
374 uint _num_blocks; // Count of basic blocks
375 Block_List _blocks; // List of basic blocks
376 RootNode *_root; // Root of whole program
377 Block_Array _bbs; // Map Nodes to owning Basic Block
378 Block *_broot; // Basic block of root
379 uint _rpo_ctr;
380 CFGLoop* _root_loop;
381 float _outer_loop_freq; // Outmost loop frequency
382
383 // Per node latency estimation, valid only during GCM
384 GrowableArray<uint> *_node_latency;
385
386 #ifndef PRODUCT
387 bool _trace_opto_pipelining; // tracing flag
388 #endif
389
390 #ifdef ASSERT
391 Unique_Node_List _raw_oops;
392 #endif
393
394 // Build dominators
395 void Dominators();
396
397 // Estimate block frequencies based on IfNode probabilities
398 void Estimate_Block_Frequency();
399
400 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific
401 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.
402 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );
403
404 // Compute the (backwards) latency of a node from the uses
405 void latency_from_uses(Node *n);
406
407 // Compute the (backwards) latency of a node from a single use
408 int latency_from_use(Node *n, const Node *def, Node *use);
409
410 // Compute the (backwards) latency of a node from the uses of this instruction
411 void partial_latency_of_defs(Node *n);
412
413 // Schedule Nodes early in their basic blocks.
414 bool schedule_early(VectorSet &visited, Node_List &roots);
415
416 // For each node, find the latest block it can be scheduled into
417 // and then select the cheapest block between the latest and earliest
418 // block to place the node.
419 void schedule_late(VectorSet &visited, Node_List &stack);
420
421 // Pick a block between early and late that is a cheaper alternative
422 // to late. Helper for schedule_late.
423 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
424
425 // Compute the instruction global latency with a backwards walk
426 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);
427
428 // Set loop alignment
429 void set_loop_alignment();
430
431 // Remove empty basic blocks
432 void remove_empty();
433 void fixup_flow();
434 bool move_to_next(Block* bx, uint b_index);
435 void move_to_end(Block* bx, uint b_index);
436 void insert_goto_at(uint block_no, uint succ_no);
437
438 // Check for NeverBranch at block end. This needs to become a GOTO to the
439 // true target. NeverBranch are treated as a conditional branch that always
440 // goes the same direction for most of the optimizer and are used to give a
441 // fake exit path to infinite loops. At this late stage they need to turn
442 // into Goto's so that when you enter the infinite loop you indeed hang.
443 void convert_NeverBranch_to_Goto(Block *b);
444
445 CFGLoop* create_loop_tree();
446
447 // Insert a node into a block, and update the _bbs
448 void insert( Block *b, uint idx, Node *n ) {
449 b->_nodes.insert( idx, n );
450 _bbs.map( n->_idx, b );
451 }
452
453 #ifndef PRODUCT
454 bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
455
456 // Debugging print of CFG
457 void dump( ) const; // CFG only
458 void _dump_cfg( const Node *end, VectorSet &visited ) const;
459 void verify() const;
460 void dump_headers();
461 #else
462 bool trace_opto_pipelining() const { return false; }
463 #endif
464 };
465
466
467 //------------------------------UnionFind--------------------------------------
468 // Map Block indices to a block-index for a cfg-cover.
469 // Array lookup in the optimized case.
470 class UnionFind : public ResourceObj {
471 uint _cnt, _max;
472 uint* _indices;
473 ReallocMark _nesting; // assertion check for reallocations
474 public:
475 UnionFind( uint max );
476 void reset( uint max ); // Reset to identity map for [0..max]
477
478 uint lookup( uint nidx ) const {
479 return _indices[nidx];
480 }
481 uint operator[] (uint nidx) const { return lookup(nidx); }
482
483 void map( uint from_idx, uint to_idx ) {
484 assert( from_idx < _cnt, "oob" );
485 _indices[from_idx] = to_idx;
486 }
487 void extend( uint from_idx, uint to_idx );
488
489 uint Size() const { return _cnt; }
490
491 uint Find( uint idx ) {
492 assert( idx < 65536, "Must fit into uint");
493 uint uf_idx = lookup(idx);
494 return (uf_idx == idx) ? uf_idx : Find_compress(idx);
495 }
496 uint Find_compress( uint idx );
497 uint Find_const( uint idx ) const;
498 void Union( uint idx1, uint idx2 );
499
500 };
501
502 //----------------------------BlockProbPair---------------------------
503 // Ordered pair of Node*.
504 class BlockProbPair VALUE_OBJ_CLASS_SPEC {
505 protected:
506 Block* _target; // block target
507 float _prob; // probability of edge to block
508 public:
509 BlockProbPair() : _target(NULL), _prob(0.0) {}
510 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}
511
512 Block* get_target() const { return _target; }
513 float get_prob() const { return _prob; }
514 };
515
516 //------------------------------CFGLoop-------------------------------------------
517 class CFGLoop : public CFGElement {
518 int _id;
519 int _depth;
520 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null
521 CFGLoop *_sibling; // null terminated list
522 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops
523 GrowableArray<CFGElement*> _members; // list of members of loop
524 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
525 float _exit_prob; // probability any loop exit is taken on a single loop iteration
526 void update_succ_freq(Block* b, float freq);
527
528 public:
529 CFGLoop(int id) :
530 CFGElement(),
531 _id(id),
532 _depth(0),
533 _parent(NULL),
534 _sibling(NULL),
535 _child(NULL),
536 _exit_prob(1.0f) {}
537 CFGLoop* parent() { return _parent; }
538 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk);
539 void add_member(CFGElement *s) { _members.push(s); }
540 void add_nested_loop(CFGLoop* cl);
541 Block* head() {
542 assert(_members.at(0)->is_block(), "head must be a block");
543 Block* hd = _members.at(0)->as_Block();
544 assert(hd->_loop == this, "just checking");
545 assert(hd->head()->is_Loop(), "must begin with loop head node");
546 return hd;
547 }
548 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL)
549 void compute_loop_depth(int depth);
550 void compute_freq(); // compute frequency with loop assuming head freq 1.0f
551 void scale_freq(); // scale frequency by loop trip count (including outer loops)
552 float outer_loop_freq() const; // frequency of outer loop
553 bool in_loop_nest(Block* b);
554 float trip_count() const { return 1.0f / _exit_prob; }
555 virtual bool is_loop() { return true; }
556 int id() { return _id; }
557
558 #ifndef PRODUCT
559 void dump( ) const;
560 void dump_tree() const;
561 #endif
562 };
563
564
565 //----------------------------------CFGEdge------------------------------------
566 // A edge between two basic blocks that will be embodied by a branch or a
567 // fall-through.
568 class CFGEdge : public ResourceObj {
569 private:
570 Block * _from; // Source basic block
571 Block * _to; // Destination basic block
572 float _freq; // Execution frequency (estimate)
573 int _state;
574 bool _infrequent;
575 int _from_pct;
576 int _to_pct;
577
578 // Private accessors
579 int from_pct() const { return _from_pct; }
580 int to_pct() const { return _to_pct; }
581 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; }
582 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; }
583
584 public:
585 enum {
586 open, // initial edge state; unprocessed
587 connected, // edge used to connect two traces together
588 interior // edge is interior to trace (could be backedge)
589 };
590
591 CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) :
592 _from(from), _to(to), _freq(freq),
593 _from_pct(from_pct), _to_pct(to_pct), _state(open) {
594 _infrequent = from_infrequent() || to_infrequent();
595 }
596
597 float freq() const { return _freq; }
598 Block* from() const { return _from; }
599 Block* to () const { return _to; }
600 int infrequent() const { return _infrequent; }
601 int state() const { return _state; }
602
603 void set_state(int state) { _state = state; }
604
605 #ifndef PRODUCT
606 void dump( ) const;
607 #endif
608 };
609
610
611 //-----------------------------------Trace-------------------------------------
612 // An ordered list of basic blocks.
613 class Trace : public ResourceObj {
614 private:
615 uint _id; // Unique Trace id (derived from initial block)
616 Block ** _next_list; // Array mapping index to next block
617 Block ** _prev_list; // Array mapping index to previous block
618 Block * _first; // First block in the trace
619 Block * _last; // Last block in the trace
620
621 // Return the block that follows "b" in the trace.
622 Block * next(Block *b) const { return _next_list[b->_pre_order]; }
623 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; }
624
625 // Return the block that precedes "b" in the trace.
626 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; }
627 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; }
628
629 // We've discovered a loop in this trace. Reset last to be "b", and first as
630 // the block following "b
631 void break_loop_after(Block *b) {
632 _last = b;
633 _first = next(b);
634 set_prev(_first, NULL);
635 set_next(_last, NULL);
636 }
637
638 public:
639
640 Trace(Block *b, Block **next_list, Block **prev_list) :
641 _first(b),
642 _last(b),
643 _next_list(next_list),
644 _prev_list(prev_list),
645 _id(b->_pre_order) {
646 set_next(b, NULL);
647 set_prev(b, NULL);
648 };
649
650 // Return the id number
651 uint id() const { return _id; }
652 void set_id(uint id) { _id = id; }
653
654 // Return the first block in the trace
655 Block * first_block() const { return _first; }
656
657 // Return the last block in the trace
658 Block * last_block() const { return _last; }
659
660 // Insert a trace in the middle of this one after b
661 void insert_after(Block *b, Trace *tr) {
662 set_next(tr->last_block(), next(b));
663 if (next(b) != NULL) {
664 set_prev(next(b), tr->last_block());
665 }
666
667 set_next(b, tr->first_block());
668 set_prev(tr->first_block(), b);
669
670 if (b == _last) {
671 _last = tr->last_block();
672 }
673 }
674
675 void insert_before(Block *b, Trace *tr) {
676 Block *p = prev(b);
677 assert(p != NULL, "use append instead");
678 insert_after(p, tr);
679 }
680
681 // Append another trace to this one.
682 void append(Trace *tr) {
683 insert_after(_last, tr);
684 }
685
686 // Append a block at the end of this trace
687 void append(Block *b) {
688 set_next(_last, b);
689 set_prev(b, _last);
690 _last = b;
691 }
692
693 // Adjust the the blocks in this trace
694 void fixup_blocks(PhaseCFG &cfg);
695 bool backedge(CFGEdge *e);
696
697 #ifndef PRODUCT
698 void dump( ) const;
699 #endif
700 };
701
702 //------------------------------PhaseBlockLayout-------------------------------
703 // Rearrange blocks into some canonical order, based on edges and their frequencies
704 class PhaseBlockLayout : public Phase {
705 PhaseCFG &_cfg; // Control flow graph
706
707 GrowableArray<CFGEdge *> *edges;
708 Trace **traces;
709 Block **next;
710 Block **prev;
711 UnionFind *uf;
712
713 // Given a block, find its encompassing Trace
714 Trace * trace(Block *b) {
715 return traces[uf->Find_compress(b->_pre_order)];
716 }
717 public:
718 PhaseBlockLayout(PhaseCFG &cfg);
719
720 void find_edges();
721 void grow_traces();
722 void merge_traces(bool loose_connections);
723 void reorder_traces(int count);
724 void union_traces(Trace* from, Trace* to);
725 };
726
727 #endif // SHARE_VM_OPTO_BLOCK_HPP