1 /*
2 * Copyright (c) 1997, 2012, 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.
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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 friend class VMStructs;
49 uint _size; // allocated size, as opposed to formal limit
50 debug_only(uint _limit;) // limit to formal domain
51 protected:
52 Block **_blocks;
53 void grow( uint i ); // Grow array node to fit
54
55 public:
56 Arena *_arena; // Arena to allocate in
57
58 Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) {
59 debug_only(_limit=0);
60 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );
61 for( int i = 0; i < OptoBlockListSize; i++ ) {
62 _blocks[i] = NULL;
63 }
64 }
65 Block *lookup( uint i ) const // Lookup, or NULL for not mapped
66 { return (i<Max()) ? _blocks[i] : (Block*)NULL; }
67 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped
68 { assert( i < Max(), "oob" ); return _blocks[i]; }
69 // Extend the mapping: index i maps to Block *n.
70 void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; }
71 uint Max() const { debug_only(return _limit); return _size; }
72 };
73
74
75 class Block_List : public Block_Array {
76 friend class VMStructs;
77 public:
78 uint _cnt;
79 Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}
80 void push( Block *b ) { map(_cnt++,b); }
81 Block *pop() { return _blocks[--_cnt]; }
82 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}
83 void remove( uint i );
84 void insert( uint i, Block *n );
85 uint size() const { return _cnt; }
86 void reset() { _cnt = 0; }
87 void print();
88 };
89
90
91 class CFGElement : public ResourceObj {
92 friend class VMStructs;
93 public:
94 float _freq; // Execution frequency (estimate)
95
96 CFGElement() : _freq(0.0f) {}
97 virtual bool is_block() { return false; }
98 virtual bool is_loop() { return false; }
99 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; }
100 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; }
101 };
102
103 //------------------------------Block------------------------------------------
104 // This class defines a Basic Block.
105 // Basic blocks are used during the output routines, and are not used during
106 // any optimization pass. They are created late in the game.
107 class Block : public CFGElement {
108 friend class VMStructs;
109 public:
110 // Nodes in this block, in order
111 Node_List _nodes;
112
113 // Basic blocks have a Node which defines Control for all Nodes pinned in
114 // this block. This Node is a RegionNode. Exception-causing Nodes
115 // (division, subroutines) and Phi functions are always pinned. Later,
116 // every Node will get pinned to some block.
117 Node *head() const { return _nodes[0]; }
118
119 // CAUTION: num_preds() is ONE based, so that predecessor numbers match
120 // input edges to Regions and Phis.
121 uint num_preds() const { return head()->req(); }
122 Node *pred(uint i) const { return head()->in(i); }
123
124 // Array of successor blocks, same size as projs array
125 Block_Array _succs;
126
127 // Basic blocks have some number of Nodes which split control to all
128 // following blocks. These Nodes are always Projections. The field in
129 // the Projection and the block-ending Node determine which Block follows.
130 uint _num_succs;
131
132 // Basic blocks also carry all sorts of good old fashioned DFS information
133 // used to find loops, loop nesting depth, dominators, etc.
134 uint _pre_order; // Pre-order DFS number
135
136 // Dominator tree
137 uint _dom_depth; // Depth in dominator tree for fast LCA
138 Block* _idom; // Immediate dominator block
139
140 CFGLoop *_loop; // Loop to which this block belongs
141 uint _rpo; // Number in reverse post order walk
142
143 virtual bool is_block() { return true; }
144 float succ_prob(uint i); // return probability of i'th successor
145 int num_fall_throughs(); // How many fall-through candidate this block has
146 void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code
147 bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate
148 Block* lone_fall_through(); // Return lone fall-through Block or null
149
150 Block* dom_lca(Block* that); // Compute LCA in dominator tree.
151 #ifdef ASSERT
152 bool dominates(Block* that) {
153 int dom_diff = this->_dom_depth - that->_dom_depth;
154 if (dom_diff > 0) return false;
155 for (; dom_diff < 0; dom_diff++) that = that->_idom;
156 return this == that;
157 }
158 #endif
159
160 // Report the alignment required by this block. Must be a power of 2.
161 // The previous block will insert nops to get this alignment.
162 uint code_alignment();
163 uint compute_loop_alignment();
164
165 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
166 // It is currently also used to scale such frequencies relative to
167 // FreqCountInvocations relative to the old value of 1500.
168 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations)
169
170 // Register Pressure (estimate) for Splitting heuristic
171 uint _reg_pressure;
172 uint _ihrp_index;
173 uint _freg_pressure;
174 uint _fhrp_index;
175
176 // Mark and visited bits for an LCA calculation in insert_anti_dependences.
177 // Since they hold unique node indexes, they do not need reinitialization.
178 node_idx_t _raise_LCA_mark;
179 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; }
180 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; }
181 node_idx_t _raise_LCA_visited;
182 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }
183 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; }
184
185 // Estimated size in bytes of first instructions in a loop.
186 uint _first_inst_size;
187 uint first_inst_size() const { return _first_inst_size; }
188 void set_first_inst_size(uint s) { _first_inst_size = s; }
189
190 // Compute the size of first instructions in this block.
191 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
192
193 // Compute alignment padding if the block needs it.
194 // Align a loop if loop's padding is less or equal to padding limit
195 // or the size of first instructions in the loop > padding.
196 uint alignment_padding(int current_offset) {
197 int block_alignment = code_alignment();
198 int max_pad = block_alignment-relocInfo::addr_unit();
199 if( max_pad > 0 ) {
200 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");
201 int current_alignment = current_offset & max_pad;
202 if( current_alignment != 0 ) {
203 uint padding = (block_alignment-current_alignment) & max_pad;
204 if( has_loop_alignment() &&
205 padding > (uint)MaxLoopPad &&
206 first_inst_size() <= padding ) {
207 return 0;
208 }
209 return padding;
210 }
211 }
212 return 0;
213 }
214
215 // Connector blocks. Connector blocks are basic blocks devoid of
216 // instructions, but may have relevant non-instruction Nodes, such as
217 // Phis or MergeMems. Such blocks are discovered and marked during the
218 // RemoveEmpty phase, and elided during Output.
219 bool _connector;
220 void set_connector() { _connector = true; }
221 bool is_connector() const { return _connector; };
222
223 // Loop_alignment will be set for blocks which are at the top of loops.
224 // The block layout pass may rotate loops such that the loop head may not
225 // be the sequentially first block of the loop encountered in the linear
226 // list of blocks. If the layout pass is not run, loop alignment is set
227 // for each block which is the head of a loop.
228 uint _loop_alignment;
229 void set_loop_alignment(Block *loop_top) {
230 uint new_alignment = loop_top->compute_loop_alignment();
231 if (new_alignment > _loop_alignment) {
232 _loop_alignment = new_alignment;
233 }
234 }
235 uint loop_alignment() const { return _loop_alignment; }
236 bool has_loop_alignment() const { return loop_alignment() > 0; }
237
238 // Create a new Block with given head Node.
239 // Creates the (empty) predecessor arrays.
240 Block( Arena *a, Node *headnode )
241 : CFGElement(),
242 _nodes(a),
243 _succs(a),
244 _num_succs(0),
245 _pre_order(0),
246 _idom(0),
247 _loop(NULL),
248 _reg_pressure(0),
249 _ihrp_index(1),
250 _freg_pressure(0),
251 _fhrp_index(1),
252 _raise_LCA_mark(0),
253 _raise_LCA_visited(0),
254 _first_inst_size(999999),
255 _connector(false),
256 _loop_alignment(0) {
257 _nodes.push(headnode);
258 }
259
260 // Index of 'end' Node
261 uint end_idx() const {
262 // %%%%% add a proj after every goto
263 // so (last->is_block_proj() != last) always, then simplify this code
264 // This will not give correct end_idx for block 0 when it only contains root.
265 int last_idx = _nodes.size() - 1;
266 Node *last = _nodes[last_idx];
267 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");
268 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);
269 }
270
271 // Basic blocks have a Node which ends them. This Node determines which
272 // basic block follows this one in the program flow. This Node is either an
273 // IfNode, a GotoNode, a JmpNode, or a ReturnNode.
274 Node *end() const { return _nodes[end_idx()]; }
275
276 // Add an instruction to an existing block. It must go after the head
277 // instruction and before the end instruction.
278 void add_inst( Node *n ) { _nodes.insert(end_idx(),n); }
279 // Find node in block
280 uint find_node( const Node *n ) const;
281 // Find and remove n from block list
282 void find_remove( const Node *n );
283
284 // helper function that adds caller save registers to MachProjNode
285 void add_call_kills(MachProjNode *proj, RegMask& regs, const char* save_policy, bool exclude_soe);
286 // Schedule a call next in the block
287 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, GrowableArray<int> &ready_cnt, MachCallNode *mcall, VectorSet &next_call);
288
289 // Perform basic-block local scheduling
290 Node *select(PhaseCFG *cfg, Node_List &worklist, GrowableArray<int> &ready_cnt, VectorSet &next_call, uint sched_slot);
291 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );
292 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);
293 bool schedule_local(PhaseCFG *cfg, Matcher &m, GrowableArray<int> &ready_cnt, VectorSet &next_call);
294 // Cleanup if any code lands between a Call and his Catch
295 void call_catch_cleanup(Block_Array &bbs, Compile *C);
296 // Detect implicit-null-check opportunities. Basically, find NULL checks
297 // with suitable memory ops nearby. Use the memory op to do the NULL check.
298 // I can generate a memory op if there is not one nearby.
299 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);
300
301 // Return the empty status of a block
302 enum { not_empty, empty_with_goto, completely_empty };
303 int is_Empty() const;
304
305 // Forward through connectors
306 Block* non_connector() {
307 Block* s = this;
308 while (s->is_connector()) {
309 s = s->_succs[0];
310 }
311 return s;
312 }
313
314 // Return true if b is a successor of this block
315 bool has_successor(Block* b) const {
316 for (uint i = 0; i < _num_succs; i++ ) {
317 if (non_connector_successor(i) == b) {
318 return true;
319 }
320 }
321 return false;
322 }
323
324 // Successor block, after forwarding through connectors
325 Block* non_connector_successor(int i) const {
326 return _succs[i]->non_connector();
327 }
328
329 // Examine block's code shape to predict if it is not commonly executed.
330 bool has_uncommon_code() const;
331
332 // Use frequency calculations and code shape to predict if the block
333 // is uncommon.
334 bool is_uncommon( Block_Array &bbs ) const;
335
336 #ifndef PRODUCT
337 // Debugging print of basic block
338 void dump_bidx(const Block* orig, outputStream* st = tty) const;
339 void dump_pred(const Block_Array *bbs, Block* orig, outputStream* st = tty) const;
340 void dump_head( const Block_Array *bbs, outputStream* st = tty ) const;
341 void dump() const;
342 void dump( const Block_Array *bbs ) const;
343 #endif
344 };
345
346
347 //------------------------------PhaseCFG---------------------------------------
348 // Build an array of Basic Block pointers, one per Node.
349 class PhaseCFG : public Phase {
350 friend class VMStructs;
351 private:
352 // Build a proper looking cfg. Return count of basic blocks
353 uint build_cfg();
354
355 // Perform DFS search.
356 // Setup 'vertex' as DFS to vertex mapping.
357 // Setup 'semi' as vertex to DFS mapping.
358 // Set 'parent' to DFS parent.
359 uint DFS( Tarjan *tarjan );
360
361 // Helper function to insert a node into a block
362 void schedule_node_into_block( Node *n, Block *b );
363
364 void replace_block_proj_ctrl( Node *n );
365
366 // Set the basic block for pinned Nodes
367 void schedule_pinned_nodes( VectorSet &visited );
368
369 // I'll need a few machine-specific GotoNodes. Clone from this one.
370 MachNode *_goto;
371
372 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
373 void verify_anti_dependences(Block* LCA, Node* load) {
374 assert(LCA == _bbs[load->_idx], "should already be scheduled");
375 insert_anti_dependences(LCA, load, true);
376 }
377
378 public:
379 PhaseCFG( Arena *a, RootNode *r, Matcher &m );
380
381 uint _num_blocks; // Count of basic blocks
382 Block_List _blocks; // List of basic blocks
383 RootNode *_root; // Root of whole program
384 Block_Array _bbs; // Map Nodes to owning Basic Block
385 Block *_broot; // Basic block of root
386 uint _rpo_ctr;
387 CFGLoop* _root_loop;
388 float _outer_loop_freq; // Outmost loop frequency
389
390 // Per node latency estimation, valid only during GCM
391 GrowableArray<uint> *_node_latency;
392
393 #ifndef PRODUCT
394 bool _trace_opto_pipelining; // tracing flag
395 #endif
396
397 #ifdef ASSERT
398 Unique_Node_List _raw_oops;
399 #endif
400
401 // Build dominators
402 void Dominators();
403
404 // Estimate block frequencies based on IfNode probabilities
405 void Estimate_Block_Frequency();
406
407 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific
408 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.
409 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );
410
411 // Compute the (backwards) latency of a node from the uses
412 void latency_from_uses(Node *n);
413
414 // Compute the (backwards) latency of a node from a single use
415 int latency_from_use(Node *n, const Node *def, Node *use);
416
417 // Compute the (backwards) latency of a node from the uses of this instruction
418 void partial_latency_of_defs(Node *n);
419
420 // Schedule Nodes early in their basic blocks.
421 bool schedule_early(VectorSet &visited, Node_List &roots);
422
423 // For each node, find the latest block it can be scheduled into
424 // and then select the cheapest block between the latest and earliest
425 // block to place the node.
426 void schedule_late(VectorSet &visited, Node_List &stack);
427
428 // Pick a block between early and late that is a cheaper alternative
429 // to late. Helper for schedule_late.
430 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
431
432 // Compute the instruction global latency with a backwards walk
433 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);
434
435 // Set loop alignment
436 void set_loop_alignment();
437
438 // Remove empty basic blocks
439 void remove_empty();
440 void fixup_flow();
441 bool move_to_next(Block* bx, uint b_index);
442 void move_to_end(Block* bx, uint b_index);
443 void insert_goto_at(uint block_no, uint succ_no);
444
445 // Check for NeverBranch at block end. This needs to become a GOTO to the
446 // true target. NeverBranch are treated as a conditional branch that always
447 // goes the same direction for most of the optimizer and are used to give a
448 // fake exit path to infinite loops. At this late stage they need to turn
449 // into Goto's so that when you enter the infinite loop you indeed hang.
450 void convert_NeverBranch_to_Goto(Block *b);
451
452 CFGLoop* create_loop_tree();
453
454 // Insert a node into a block, and update the _bbs
455 void insert( Block *b, uint idx, Node *n ) {
456 b->_nodes.insert( idx, n );
457 _bbs.map( n->_idx, b );
458 }
459
460 #ifndef PRODUCT
461 bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
462
463 // Debugging print of CFG
464 void dump( ) const; // CFG only
465 void _dump_cfg( const Node *end, VectorSet &visited ) const;
466 void verify() const;
467 void dump_headers();
468 #else
469 bool trace_opto_pipelining() const { return false; }
470 #endif
471 };
472
473
474 //------------------------------UnionFind--------------------------------------
475 // Map Block indices to a block-index for a cfg-cover.
476 // Array lookup in the optimized case.
477 class UnionFind : public ResourceObj {
478 uint _cnt, _max;
479 uint* _indices;
480 ReallocMark _nesting; // assertion check for reallocations
481 public:
482 UnionFind( uint max );
483 void reset( uint max ); // Reset to identity map for [0..max]
484
485 uint lookup( uint nidx ) const {
486 return _indices[nidx];
487 }
488 uint operator[] (uint nidx) const { return lookup(nidx); }
489
490 void map( uint from_idx, uint to_idx ) {
491 assert( from_idx < _cnt, "oob" );
492 _indices[from_idx] = to_idx;
493 }
494 void extend( uint from_idx, uint to_idx );
495
496 uint Size() const { return _cnt; }
497
498 uint Find( uint idx ) {
499 assert( idx < 65536, "Must fit into uint");
500 uint uf_idx = lookup(idx);
501 return (uf_idx == idx) ? uf_idx : Find_compress(idx);
502 }
503 uint Find_compress( uint idx );
504 uint Find_const( uint idx ) const;
505 void Union( uint idx1, uint idx2 );
506
507 };
508
509 //----------------------------BlockProbPair---------------------------
510 // Ordered pair of Node*.
511 class BlockProbPair VALUE_OBJ_CLASS_SPEC {
512 protected:
513 Block* _target; // block target
514 float _prob; // probability of edge to block
515 public:
516 BlockProbPair() : _target(NULL), _prob(0.0) {}
517 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}
518
519 Block* get_target() const { return _target; }
520 float get_prob() const { return _prob; }
521 };
522
523 //------------------------------CFGLoop-------------------------------------------
524 class CFGLoop : public CFGElement {
525 friend class VMStructs;
526 int _id;
527 int _depth;
528 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null
529 CFGLoop *_sibling; // null terminated list
530 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops
531 GrowableArray<CFGElement*> _members; // list of members of loop
532 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
533 float _exit_prob; // probability any loop exit is taken on a single loop iteration
534 void update_succ_freq(Block* b, float freq);
535
536 public:
537 CFGLoop(int id) :
538 CFGElement(),
539 _id(id),
540 _depth(0),
541 _parent(NULL),
542 _sibling(NULL),
543 _child(NULL),
544 _exit_prob(1.0f) {}
545 CFGLoop* parent() { return _parent; }
546 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk);
547 void add_member(CFGElement *s) { _members.push(s); }
548 void add_nested_loop(CFGLoop* cl);
549 Block* head() {
550 assert(_members.at(0)->is_block(), "head must be a block");
551 Block* hd = _members.at(0)->as_Block();
552 assert(hd->_loop == this, "just checking");
553 assert(hd->head()->is_Loop(), "must begin with loop head node");
554 return hd;
555 }
556 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL)
557 void compute_loop_depth(int depth);
558 void compute_freq(); // compute frequency with loop assuming head freq 1.0f
559 void scale_freq(); // scale frequency by loop trip count (including outer loops)
560 float outer_loop_freq() const; // frequency of outer loop
561 bool in_loop_nest(Block* b);
562 float trip_count() const { return 1.0f / _exit_prob; }
563 virtual bool is_loop() { return true; }
564 int id() { return _id; }
565
566 #ifndef PRODUCT
567 void dump( ) const;
568 void dump_tree() const;
569 #endif
570 };
571
572
573 //----------------------------------CFGEdge------------------------------------
574 // A edge between two basic blocks that will be embodied by a branch or a
575 // fall-through.
576 class CFGEdge : public ResourceObj {
577 friend class VMStructs;
578 private:
579 Block * _from; // Source basic block
580 Block * _to; // Destination basic block
581 float _freq; // Execution frequency (estimate)
582 int _state;
583 bool _infrequent;
584 int _from_pct;
585 int _to_pct;
586
587 // Private accessors
588 int from_pct() const { return _from_pct; }
589 int to_pct() const { return _to_pct; }
590 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; }
591 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; }
592
593 public:
594 enum {
595 open, // initial edge state; unprocessed
596 connected, // edge used to connect two traces together
597 interior // edge is interior to trace (could be backedge)
598 };
599
600 CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) :
601 _from(from), _to(to), _freq(freq),
602 _from_pct(from_pct), _to_pct(to_pct), _state(open) {
603 _infrequent = from_infrequent() || to_infrequent();
604 }
605
606 float freq() const { return _freq; }
607 Block* from() const { return _from; }
608 Block* to () const { return _to; }
609 int infrequent() const { return _infrequent; }
610 int state() const { return _state; }
611
612 void set_state(int state) { _state = state; }
613
614 #ifndef PRODUCT
615 void dump( ) const;
616 #endif
617 };
618
619
620 //-----------------------------------Trace-------------------------------------
621 // An ordered list of basic blocks.
622 class Trace : public ResourceObj {
623 private:
624 uint _id; // Unique Trace id (derived from initial block)
625 Block ** _next_list; // Array mapping index to next block
626 Block ** _prev_list; // Array mapping index to previous block
627 Block * _first; // First block in the trace
628 Block * _last; // Last block in the trace
629
630 // Return the block that follows "b" in the trace.
631 Block * next(Block *b) const { return _next_list[b->_pre_order]; }
632 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; }
633
634 // Return the block that precedes "b" in the trace.
635 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; }
636 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; }
637
638 // We've discovered a loop in this trace. Reset last to be "b", and first as
639 // the block following "b
640 void break_loop_after(Block *b) {
641 _last = b;
642 _first = next(b);
643 set_prev(_first, NULL);
644 set_next(_last, NULL);
645 }
646
647 public:
648
649 Trace(Block *b, Block **next_list, Block **prev_list) :
650 _first(b),
651 _last(b),
652 _next_list(next_list),
653 _prev_list(prev_list),
654 _id(b->_pre_order) {
655 set_next(b, NULL);
656 set_prev(b, NULL);
657 };
658
659 // Return the id number
660 uint id() const { return _id; }
661 void set_id(uint id) { _id = id; }
662
663 // Return the first block in the trace
664 Block * first_block() const { return _first; }
665
666 // Return the last block in the trace
667 Block * last_block() const { return _last; }
668
669 // Insert a trace in the middle of this one after b
670 void insert_after(Block *b, Trace *tr) {
671 set_next(tr->last_block(), next(b));
672 if (next(b) != NULL) {
673 set_prev(next(b), tr->last_block());
674 }
675
676 set_next(b, tr->first_block());
677 set_prev(tr->first_block(), b);
678
679 if (b == _last) {
680 _last = tr->last_block();
681 }
682 }
683
684 void insert_before(Block *b, Trace *tr) {
685 Block *p = prev(b);
686 assert(p != NULL, "use append instead");
687 insert_after(p, tr);
688 }
689
690 // Append another trace to this one.
691 void append(Trace *tr) {
692 insert_after(_last, tr);
693 }
694
695 // Append a block at the end of this trace
696 void append(Block *b) {
697 set_next(_last, b);
698 set_prev(b, _last);
699 _last = b;
700 }
701
702 // Adjust the the blocks in this trace
703 void fixup_blocks(PhaseCFG &cfg);
704 bool backedge(CFGEdge *e);
705
706 #ifndef PRODUCT
707 void dump( ) const;
708 #endif
709 };
710
711 //------------------------------PhaseBlockLayout-------------------------------
712 // Rearrange blocks into some canonical order, based on edges and their frequencies
713 class PhaseBlockLayout : public Phase {
714 friend class VMStructs;
715 PhaseCFG &_cfg; // Control flow graph
716
717 GrowableArray<CFGEdge *> *edges;
718 Trace **traces;
719 Block **next;
720 Block **prev;
721 UnionFind *uf;
722
723 // Given a block, find its encompassing Trace
724 Trace * trace(Block *b) {
725 return traces[uf->Find_compress(b->_pre_order)];
726 }
727 public:
728 PhaseBlockLayout(PhaseCFG &cfg);
729
730 void find_edges();
731 void grow_traces();
732 void merge_traces(bool loose_connections);
733 void reorder_traces(int count);
734 void union_traces(Trace* from, Trace* to);
735 };
736
737 #endif // SHARE_VM_OPTO_BLOCK_HPP