Mon, 26 Sep 2011 10:24:05 -0700
7081933: Use zeroing elimination optimization for large array
Summary: Don't zero new typeArray during runtime call if the allocation is followed by arraycopy into it.
Reviewed-by: twisti
1 /*
2 * Copyright (c) 1997, 2011, 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
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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,
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23 */
25 #ifndef SHARE_VM_OPTO_BLOCK_HPP
26 #define SHARE_VM_OPTO_BLOCK_HPP
28 #include "opto/multnode.hpp"
29 #include "opto/node.hpp"
30 #include "opto/phase.hpp"
32 // Optimization - Graph Style
34 class Block;
35 class CFGLoop;
36 class MachCallNode;
37 class Matcher;
38 class RootNode;
39 class VectorSet;
40 struct Tarjan;
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
55 public:
56 Arena *_arena; // Arena to allocate in
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 };
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 };
91 class CFGElement : public ResourceObj {
92 friend class VMStructs;
93 public:
94 float _freq; // Execution frequency (estimate)
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 };
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;
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]; }
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); }
124 // Array of successor blocks, same size as projs array
125 Block_Array _succs;
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;
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
136 // Dominator tree
137 uint _dom_depth; // Depth in dominator tree for fast LCA
138 Block* _idom; // Immediate dominator block
140 CFGLoop *_loop; // Loop to which this block belongs
141 uint _rpo; // Number in reverse post order walk
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
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
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();
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)
170 // Register Pressure (estimate) for Splitting heuristic
171 uint _reg_pressure;
172 uint _ihrp_index;
173 uint _freg_pressure;
174 uint _fhrp_index;
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; }
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; }
190 // Compute the size of first instructions in this block.
191 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
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 }
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; };
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; }
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 }
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 }
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()]; }
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 );
284 // Schedule a call next in the block
285 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call);
287 // Perform basic-block local scheduling
288 Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot);
289 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );
290 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);
291 bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call);
292 // Cleanup if any code lands between a Call and his Catch
293 void call_catch_cleanup(Block_Array &bbs);
294 // Detect implicit-null-check opportunities. Basically, find NULL checks
295 // with suitable memory ops nearby. Use the memory op to do the NULL check.
296 // I can generate a memory op if there is not one nearby.
297 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);
299 // Return the empty status of a block
300 enum { not_empty, empty_with_goto, completely_empty };
301 int is_Empty() const;
303 // Forward through connectors
304 Block* non_connector() {
305 Block* s = this;
306 while (s->is_connector()) {
307 s = s->_succs[0];
308 }
309 return s;
310 }
312 // Return true if b is a successor of this block
313 bool has_successor(Block* b) const {
314 for (uint i = 0; i < _num_succs; i++ ) {
315 if (non_connector_successor(i) == b) {
316 return true;
317 }
318 }
319 return false;
320 }
322 // Successor block, after forwarding through connectors
323 Block* non_connector_successor(int i) const {
324 return _succs[i]->non_connector();
325 }
327 // Examine block's code shape to predict if it is not commonly executed.
328 bool has_uncommon_code() const;
330 // Use frequency calculations and code shape to predict if the block
331 // is uncommon.
332 bool is_uncommon( Block_Array &bbs ) const;
334 #ifndef PRODUCT
335 // Debugging print of basic block
336 void dump_bidx(const Block* orig, outputStream* st = tty) const;
337 void dump_pred(const Block_Array *bbs, Block* orig, outputStream* st = tty) const;
338 void dump_head( const Block_Array *bbs, outputStream* st = tty ) const;
339 void dump() const;
340 void dump( const Block_Array *bbs ) const;
341 #endif
342 };
345 //------------------------------PhaseCFG---------------------------------------
346 // Build an array of Basic Block pointers, one per Node.
347 class PhaseCFG : public Phase {
348 friend class VMStructs;
349 private:
350 // Build a proper looking cfg. Return count of basic blocks
351 uint build_cfg();
353 // Perform DFS search.
354 // Setup 'vertex' as DFS to vertex mapping.
355 // Setup 'semi' as vertex to DFS mapping.
356 // Set 'parent' to DFS parent.
357 uint DFS( Tarjan *tarjan );
359 // Helper function to insert a node into a block
360 void schedule_node_into_block( Node *n, Block *b );
362 void replace_block_proj_ctrl( Node *n );
364 // Set the basic block for pinned Nodes
365 void schedule_pinned_nodes( VectorSet &visited );
367 // I'll need a few machine-specific GotoNodes. Clone from this one.
368 MachNode *_goto;
370 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
371 void verify_anti_dependences(Block* LCA, Node* load) {
372 assert(LCA == _bbs[load->_idx], "should already be scheduled");
373 insert_anti_dependences(LCA, load, true);
374 }
376 public:
377 PhaseCFG( Arena *a, RootNode *r, Matcher &m );
379 uint _num_blocks; // Count of basic blocks
380 Block_List _blocks; // List of basic blocks
381 RootNode *_root; // Root of whole program
382 Block_Array _bbs; // Map Nodes to owning Basic Block
383 Block *_broot; // Basic block of root
384 uint _rpo_ctr;
385 CFGLoop* _root_loop;
386 float _outer_loop_freq; // Outmost loop frequency
388 // Per node latency estimation, valid only during GCM
389 GrowableArray<uint> *_node_latency;
391 #ifndef PRODUCT
392 bool _trace_opto_pipelining; // tracing flag
393 #endif
395 #ifdef ASSERT
396 Unique_Node_List _raw_oops;
397 #endif
399 // Build dominators
400 void Dominators();
402 // Estimate block frequencies based on IfNode probabilities
403 void Estimate_Block_Frequency();
405 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific
406 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.
407 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );
409 // Compute the (backwards) latency of a node from the uses
410 void latency_from_uses(Node *n);
412 // Compute the (backwards) latency of a node from a single use
413 int latency_from_use(Node *n, const Node *def, Node *use);
415 // Compute the (backwards) latency of a node from the uses of this instruction
416 void partial_latency_of_defs(Node *n);
418 // Schedule Nodes early in their basic blocks.
419 bool schedule_early(VectorSet &visited, Node_List &roots);
421 // For each node, find the latest block it can be scheduled into
422 // and then select the cheapest block between the latest and earliest
423 // block to place the node.
424 void schedule_late(VectorSet &visited, Node_List &stack);
426 // Pick a block between early and late that is a cheaper alternative
427 // to late. Helper for schedule_late.
428 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
430 // Compute the instruction global latency with a backwards walk
431 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);
433 // Set loop alignment
434 void set_loop_alignment();
436 // Remove empty basic blocks
437 void remove_empty();
438 void fixup_flow();
439 bool move_to_next(Block* bx, uint b_index);
440 void move_to_end(Block* bx, uint b_index);
441 void insert_goto_at(uint block_no, uint succ_no);
443 // Check for NeverBranch at block end. This needs to become a GOTO to the
444 // true target. NeverBranch are treated as a conditional branch that always
445 // goes the same direction for most of the optimizer and are used to give a
446 // fake exit path to infinite loops. At this late stage they need to turn
447 // into Goto's so that when you enter the infinite loop you indeed hang.
448 void convert_NeverBranch_to_Goto(Block *b);
450 CFGLoop* create_loop_tree();
452 // Insert a node into a block, and update the _bbs
453 void insert( Block *b, uint idx, Node *n ) {
454 b->_nodes.insert( idx, n );
455 _bbs.map( n->_idx, b );
456 }
458 #ifndef PRODUCT
459 bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
461 // Debugging print of CFG
462 void dump( ) const; // CFG only
463 void _dump_cfg( const Node *end, VectorSet &visited ) const;
464 void verify() const;
465 void dump_headers();
466 #else
467 bool trace_opto_pipelining() const { return false; }
468 #endif
469 };
472 //------------------------------UnionFind--------------------------------------
473 // Map Block indices to a block-index for a cfg-cover.
474 // Array lookup in the optimized case.
475 class UnionFind : public ResourceObj {
476 uint _cnt, _max;
477 uint* _indices;
478 ReallocMark _nesting; // assertion check for reallocations
479 public:
480 UnionFind( uint max );
481 void reset( uint max ); // Reset to identity map for [0..max]
483 uint lookup( uint nidx ) const {
484 return _indices[nidx];
485 }
486 uint operator[] (uint nidx) const { return lookup(nidx); }
488 void map( uint from_idx, uint to_idx ) {
489 assert( from_idx < _cnt, "oob" );
490 _indices[from_idx] = to_idx;
491 }
492 void extend( uint from_idx, uint to_idx );
494 uint Size() const { return _cnt; }
496 uint Find( uint idx ) {
497 assert( idx < 65536, "Must fit into uint");
498 uint uf_idx = lookup(idx);
499 return (uf_idx == idx) ? uf_idx : Find_compress(idx);
500 }
501 uint Find_compress( uint idx );
502 uint Find_const( uint idx ) const;
503 void Union( uint idx1, uint idx2 );
505 };
507 //----------------------------BlockProbPair---------------------------
508 // Ordered pair of Node*.
509 class BlockProbPair VALUE_OBJ_CLASS_SPEC {
510 protected:
511 Block* _target; // block target
512 float _prob; // probability of edge to block
513 public:
514 BlockProbPair() : _target(NULL), _prob(0.0) {}
515 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}
517 Block* get_target() const { return _target; }
518 float get_prob() const { return _prob; }
519 };
521 //------------------------------CFGLoop-------------------------------------------
522 class CFGLoop : public CFGElement {
523 friend class VMStructs;
524 int _id;
525 int _depth;
526 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null
527 CFGLoop *_sibling; // null terminated list
528 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops
529 GrowableArray<CFGElement*> _members; // list of members of loop
530 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
531 float _exit_prob; // probability any loop exit is taken on a single loop iteration
532 void update_succ_freq(Block* b, float freq);
534 public:
535 CFGLoop(int id) :
536 CFGElement(),
537 _id(id),
538 _depth(0),
539 _parent(NULL),
540 _sibling(NULL),
541 _child(NULL),
542 _exit_prob(1.0f) {}
543 CFGLoop* parent() { return _parent; }
544 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk);
545 void add_member(CFGElement *s) { _members.push(s); }
546 void add_nested_loop(CFGLoop* cl);
547 Block* head() {
548 assert(_members.at(0)->is_block(), "head must be a block");
549 Block* hd = _members.at(0)->as_Block();
550 assert(hd->_loop == this, "just checking");
551 assert(hd->head()->is_Loop(), "must begin with loop head node");
552 return hd;
553 }
554 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL)
555 void compute_loop_depth(int depth);
556 void compute_freq(); // compute frequency with loop assuming head freq 1.0f
557 void scale_freq(); // scale frequency by loop trip count (including outer loops)
558 float outer_loop_freq() const; // frequency of outer loop
559 bool in_loop_nest(Block* b);
560 float trip_count() const { return 1.0f / _exit_prob; }
561 virtual bool is_loop() { return true; }
562 int id() { return _id; }
564 #ifndef PRODUCT
565 void dump( ) const;
566 void dump_tree() const;
567 #endif
568 };
571 //----------------------------------CFGEdge------------------------------------
572 // A edge between two basic blocks that will be embodied by a branch or a
573 // fall-through.
574 class CFGEdge : public ResourceObj {
575 friend class VMStructs;
576 private:
577 Block * _from; // Source basic block
578 Block * _to; // Destination basic block
579 float _freq; // Execution frequency (estimate)
580 int _state;
581 bool _infrequent;
582 int _from_pct;
583 int _to_pct;
585 // Private accessors
586 int from_pct() const { return _from_pct; }
587 int to_pct() const { return _to_pct; }
588 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; }
589 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; }
591 public:
592 enum {
593 open, // initial edge state; unprocessed
594 connected, // edge used to connect two traces together
595 interior // edge is interior to trace (could be backedge)
596 };
598 CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) :
599 _from(from), _to(to), _freq(freq),
600 _from_pct(from_pct), _to_pct(to_pct), _state(open) {
601 _infrequent = from_infrequent() || to_infrequent();
602 }
604 float freq() const { return _freq; }
605 Block* from() const { return _from; }
606 Block* to () const { return _to; }
607 int infrequent() const { return _infrequent; }
608 int state() const { return _state; }
610 void set_state(int state) { _state = state; }
612 #ifndef PRODUCT
613 void dump( ) const;
614 #endif
615 };
618 //-----------------------------------Trace-------------------------------------
619 // An ordered list of basic blocks.
620 class Trace : public ResourceObj {
621 private:
622 uint _id; // Unique Trace id (derived from initial block)
623 Block ** _next_list; // Array mapping index to next block
624 Block ** _prev_list; // Array mapping index to previous block
625 Block * _first; // First block in the trace
626 Block * _last; // Last block in the trace
628 // Return the block that follows "b" in the trace.
629 Block * next(Block *b) const { return _next_list[b->_pre_order]; }
630 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; }
632 // Return the block that precedes "b" in the trace.
633 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; }
634 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; }
636 // We've discovered a loop in this trace. Reset last to be "b", and first as
637 // the block following "b
638 void break_loop_after(Block *b) {
639 _last = b;
640 _first = next(b);
641 set_prev(_first, NULL);
642 set_next(_last, NULL);
643 }
645 public:
647 Trace(Block *b, Block **next_list, Block **prev_list) :
648 _first(b),
649 _last(b),
650 _next_list(next_list),
651 _prev_list(prev_list),
652 _id(b->_pre_order) {
653 set_next(b, NULL);
654 set_prev(b, NULL);
655 };
657 // Return the id number
658 uint id() const { return _id; }
659 void set_id(uint id) { _id = id; }
661 // Return the first block in the trace
662 Block * first_block() const { return _first; }
664 // Return the last block in the trace
665 Block * last_block() const { return _last; }
667 // Insert a trace in the middle of this one after b
668 void insert_after(Block *b, Trace *tr) {
669 set_next(tr->last_block(), next(b));
670 if (next(b) != NULL) {
671 set_prev(next(b), tr->last_block());
672 }
674 set_next(b, tr->first_block());
675 set_prev(tr->first_block(), b);
677 if (b == _last) {
678 _last = tr->last_block();
679 }
680 }
682 void insert_before(Block *b, Trace *tr) {
683 Block *p = prev(b);
684 assert(p != NULL, "use append instead");
685 insert_after(p, tr);
686 }
688 // Append another trace to this one.
689 void append(Trace *tr) {
690 insert_after(_last, tr);
691 }
693 // Append a block at the end of this trace
694 void append(Block *b) {
695 set_next(_last, b);
696 set_prev(b, _last);
697 _last = b;
698 }
700 // Adjust the the blocks in this trace
701 void fixup_blocks(PhaseCFG &cfg);
702 bool backedge(CFGEdge *e);
704 #ifndef PRODUCT
705 void dump( ) const;
706 #endif
707 };
709 //------------------------------PhaseBlockLayout-------------------------------
710 // Rearrange blocks into some canonical order, based on edges and their frequencies
711 class PhaseBlockLayout : public Phase {
712 friend class VMStructs;
713 PhaseCFG &_cfg; // Control flow graph
715 GrowableArray<CFGEdge *> *edges;
716 Trace **traces;
717 Block **next;
718 Block **prev;
719 UnionFind *uf;
721 // Given a block, find its encompassing Trace
722 Trace * trace(Block *b) {
723 return traces[uf->Find_compress(b->_pre_order)];
724 }
725 public:
726 PhaseBlockLayout(PhaseCFG &cfg);
728 void find_edges();
729 void grow_traces();
730 void merge_traces(bool loose_connections);
731 void reorder_traces(int count);
732 void union_traces(Trace* from, Trace* to);
733 };
735 #endif // SHARE_VM_OPTO_BLOCK_HPP