1 /*
2 * Copyright (c) 1997, 2025, 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
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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23 */
24
25 #ifndef SHARE_OPTO_BLOCK_HPP
26 #define SHARE_OPTO_BLOCK_HPP
27
28 #include "opto/multnode.hpp"
29 #include "opto/node.hpp"
30 #include "opto/phase.hpp"
31 #include "utilities/powerOfTwo.hpp"
32
33 // Optimization - Graph Style
34
35 class Block;
36 class CFGLoop;
37 class MachCallNode;
38 class Matcher;
39 class RootNode;
40 class VectorSet;
41 class PhaseChaitin;
42 struct Tarjan;
43
44 //------------------------------Block_Array------------------------------------
45 // Map dense integer indices to Blocks. Uses classic doubling-array trick.
46 // Abstractly provides an infinite array of Block*'s, initialized to null.
47 // Note that the constructor just zeros things, and since I use Arena
48 // allocation I do not need a destructor to reclaim storage.
49 class Block_Array : public ArenaObj {
50 uint _size; // allocated size, as opposed to formal limit
51 DEBUG_ONLY(uint _limit;) // limit to formal domain
52 Arena *_arena; // Arena to allocate in
53 ReallocMark _nesting; // Safety checks for arena reallocation
54 protected:
55 Block **_blocks;
56 void grow( uint i ); // Grow array node to fit
57
58 public:
59 Block_Array(Arena *a) : _size(OptoBlockListSize), _arena(a) {
60 DEBUG_ONLY(_limit=0);
61 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );
62 for( int i = 0; i < OptoBlockListSize; i++ ) {
63 _blocks[i] = nullptr;
64 }
65 }
66 Block *lookup( uint i ) const // Lookup, or null for not mapped
67 { return (i<Max()) ? _blocks[i] : (Block*)nullptr; }
68 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped
69 { assert( i < Max(), "oob" ); return _blocks[i]; }
70 // Extend the mapping: index i maps to Block *n.
71 void map( uint i, Block *n ) { grow(i); _blocks[i] = n; }
72 uint Max() const { DEBUG_ONLY(return _limit); return _size; }
73 };
74
75
76 class Block_List : public Block_Array {
77 public:
78 uint _cnt;
79 Block_List() : Block_List(Thread::current()->resource_area()) { }
80 Block_List(Arena* a) : Block_Array(a), _cnt(0) { }
81
82 void push( Block *b ) { map(_cnt++,b); }
83 Block *pop() { return _blocks[--_cnt]; }
84 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}
85 void remove( uint i );
86 void insert( uint i, Block *n );
87 uint size() const { return _cnt; }
88 void reset() { _cnt = 0; }
89 void print();
90 };
91
92
93 class CFGElement : public AnyObj {
94 public:
95 double _freq; // Execution frequency (estimate)
96
97 CFGElement() : _freq(0.0) {}
98 virtual bool is_block() { return false; }
99 virtual bool is_loop() { return false; }
100 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; }
101 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; }
102 };
103
104 //------------------------------Block------------------------------------------
105 // This class defines a Basic Block.
106 // Basic blocks are used during the output routines, and are not used during
107 // any optimization pass. They are created late in the game.
108 class Block : public CFGElement {
109
110 private:
111 // Nodes in this block, in order
112 Node_List _nodes;
113
114 public:
115
116 // Get the node at index 'at_index', if 'at_index' is out of bounds return null
117 Node* get_node(uint at_index) const {
118 return _nodes[at_index];
119 }
120
121 // Get the number of nodes in this block
122 uint number_of_nodes() const {
123 return _nodes.size();
124 }
125
126 // Map a node 'node' to index 'to_index' in the block, if the index is out of bounds the size of the node list is increased
127 void map_node(Node* node, uint to_index) {
128 _nodes.map(to_index, node);
129 }
130
131 // Insert a node 'node' at index 'at_index', moving all nodes that are on a higher index one step, if 'at_index' is out of bounds we crash
132 void insert_node(Node* node, uint at_index) {
133 _nodes.insert(at_index, node);
134 }
135
136 // Remove a node at index 'at_index'
137 void remove_node(uint at_index) {
138 _nodes.remove(at_index);
139 }
140
141 // Push a node 'node' onto the node list
142 void push_node(Node* node) {
143 _nodes.push(node);
144 }
145
146 // Pop the last node off the node list
147 Node* pop_node() {
148 return _nodes.pop();
149 }
150
151 // Basic blocks have a Node which defines Control for all Nodes pinned in
152 // this block. This Node is a RegionNode. Exception-causing Nodes
153 // (division, subroutines) and Phi functions are always pinned. Later,
154 // every Node will get pinned to some block.
155 Node *head() const { return get_node(0); }
156
157 // CAUTION: num_preds() is ONE based, so that predecessor numbers match
158 // input edges to Regions and Phis.
159 uint num_preds() const { return head()->req(); }
160 Node *pred(uint i) const { return head()->in(i); }
161
162 // Array of successor blocks, same size as projs array
163 Block_Array _succs;
164
165 // Basic blocks have some number of Nodes which split control to all
166 // following blocks. These Nodes are always Projections. The field in
167 // the Projection and the block-ending Node determine which Block follows.
168 uint _num_succs;
169
170 // Basic blocks also carry all sorts of good old fashioned DFS information
171 // used to find loops, loop nesting depth, dominators, etc.
172 uint _pre_order; // Pre-order DFS number
173
174 // Dominator tree
175 uint _dom_depth; // Depth in dominator tree for fast LCA
176 Block* _idom; // Immediate dominator block
177
178 CFGLoop *_loop; // Loop to which this block belongs
179 uint _rpo; // Number in reverse post order walk
180
181 virtual bool is_block() { return true; }
182 float succ_prob(uint i); // return probability of i'th successor
183 int num_fall_throughs(); // How many fall-through candidate this block has
184 void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code
185 bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate
186 Block* lone_fall_through(); // Return lone fall-through Block or null
187
188 Block* dom_lca(Block* that); // Compute LCA in dominator tree.
189
190 bool dominates(Block* that) {
191 int dom_diff = this->_dom_depth - that->_dom_depth;
192 if (dom_diff > 0) return false;
193 for (; dom_diff < 0; dom_diff++) that = that->_idom;
194 return this == that;
195 }
196
197 // Report the alignment required by this block. Must be a power of 2.
198 // The previous block will insert nops to get this alignment.
199 uint code_alignment() const;
200 uint compute_loop_alignment();
201
202 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
203 // It is currently also used to scale such frequencies relative to
204 // FreqCountInvocations relative to the old value of 1500.
205 #define BLOCK_FREQUENCY(f) ((f * (double) 1500) / FreqCountInvocations)
206
207 // Register Pressure (estimate) for Splitting heuristic
208 uint _reg_pressure;
209 uint _ihrp_index;
210 uint _freg_pressure;
211 uint _fhrp_index;
212
213 // Mark and visited bits for an LCA calculation in raise_above_anti_dependences.
214 // Since they hold unique node indexes, they do not need reinitialization.
215 node_idx_t _raise_LCA_mark;
216 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; }
217 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; }
218 node_idx_t _raise_LCA_visited;
219 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }
220 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; }
221
222 // Estimated size in bytes of first instructions in a loop.
223 uint _first_inst_size;
224 uint first_inst_size() const { return _first_inst_size; }
225 void set_first_inst_size(uint s) { _first_inst_size = s; }
226
227 // Compute the size of first instructions in this block.
228 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
229
230 // Compute alignment padding if the block needs it.
231 // Align a loop if loop's padding is less or equal to padding limit
232 // or the size of first instructions in the loop > padding.
233 uint alignment_padding(int current_offset) {
234 int block_alignment = code_alignment();
235 int max_pad = block_alignment-relocInfo::addr_unit();
236 if( max_pad > 0 ) {
237 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");
238 int current_alignment = current_offset & max_pad;
239 if( current_alignment != 0 ) {
240 uint padding = (block_alignment-current_alignment) & max_pad;
241 if( has_loop_alignment() &&
242 padding > (uint)MaxLoopPad &&
243 first_inst_size() <= padding ) {
244 return 0;
245 }
246 return padding;
247 }
248 }
249 return 0;
250 }
251
252 // Connector blocks. Connector blocks are basic blocks devoid of
253 // instructions, but may have relevant non-instruction Nodes, such as
254 // Phis or MergeMems. Such blocks are discovered and marked during the
255 // RemoveEmpty phase, and elided during Output.
256 bool _connector;
257 void set_connector() { _connector = true; }
258 bool is_connector() const { return _connector; };
259
260 // Loop_alignment will be set for blocks which are at the top of loops.
261 // The block layout pass may rotate loops such that the loop head may not
262 // be the sequentially first block of the loop encountered in the linear
263 // list of blocks. If the layout pass is not run, loop alignment is set
264 // for each block which is the head of a loop.
265 uint _loop_alignment;
266 void set_loop_alignment(Block *loop_top) {
267 uint new_alignment = loop_top->compute_loop_alignment();
268 if (new_alignment > _loop_alignment) {
269 _loop_alignment = new_alignment;
270 }
271 }
272 uint loop_alignment() const { return _loop_alignment; }
273 bool has_loop_alignment() const { return loop_alignment() > 0; }
274
275 // Create a new Block with given head Node.
276 // Creates the (empty) predecessor arrays.
277 Block( Arena *a, Node *headnode )
278 : CFGElement(),
279 _nodes(a),
280 _succs(a),
281 _num_succs(0),
282 _pre_order(0),
283 _idom(nullptr),
284 _loop(nullptr),
285 _reg_pressure(0),
286 _ihrp_index(1),
287 _freg_pressure(0),
288 _fhrp_index(1),
289 _raise_LCA_mark(0),
290 _raise_LCA_visited(0),
291 _first_inst_size(999999),
292 _connector(false),
293 _loop_alignment(0) {
294 _nodes.push(headnode);
295 }
296
297 // Index of 'end' Node
298 uint end_idx() const {
299 // %%%%% add a proj after every goto
300 // so (last->is_block_proj() != last) always, then simplify this code
301 // This will not give correct end_idx for block 0 when it only contains root.
302 int last_idx = _nodes.size() - 1;
303 Node *last = _nodes[last_idx];
304 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");
305 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);
306 }
307
308 // Basic blocks have a Node which ends them. This Node determines which
309 // basic block follows this one in the program flow. This Node is either an
310 // IfNode, a GotoNode, a JmpNode, or a ReturnNode.
311 Node *end() const { return _nodes[end_idx()]; }
312
313 // Add an instruction to an existing block. It must go after the head
314 // instruction and before the end instruction.
315 void add_inst( Node *n ) { insert_node(n, end_idx()); }
316 // Find node in block. Fails if node not in block.
317 uint find_node( const Node *n ) const;
318 // Find and remove n from block list
319 void find_remove( const Node *n );
320 // Check whether the node is in the block.
321 bool contains (const Node *n) const;
322
323 // Whether the block is not root-like and does not have any predecessors.
324 bool is_trivially_unreachable() const;
325
326 // Return the empty status of a block
327 enum { not_empty, empty_with_goto, completely_empty };
328 int is_Empty() const;
329
330 // Forward through connectors
331 Block* non_connector() {
332 Block* s = this;
333 while (s->is_connector()) {
334 s = s->_succs[0];
335 }
336 return s;
337 }
338
339 // Return true if b is a successor of this block
340 bool has_successor(Block* b) const {
341 for (uint i = 0; i < _num_succs; i++ ) {
342 if (non_connector_successor(i) == b) {
343 return true;
344 }
345 }
346 return false;
347 }
348
349 // Successor block, after forwarding through connectors
350 Block* non_connector_successor(int i) const {
351 return _succs[i]->non_connector();
352 }
353
354 // Examine block's code shape to predict if it is not commonly executed.
355 bool has_uncommon_code() const;
356
357 #ifndef PRODUCT
358 // Debugging print of basic block
359 void dump_bidx(const Block* orig, outputStream* st = tty) const;
360 void dump_pred(const PhaseCFG* cfg, Block* orig, outputStream* st = tty) const;
361 void dump_head(const PhaseCFG* cfg, outputStream* st = tty) const;
362 void dump() const;
363 void dump(const PhaseCFG* cfg) const;
364 #endif
365 };
366
367
368 //------------------------------PhaseCFG---------------------------------------
369 // Build an array of Basic Block pointers, one per Node.
370 class PhaseCFG : public Phase {
371 private:
372 // Root of whole program
373 RootNode* _root;
374
375 // The block containing the root node
376 Block* _root_block;
377
378 // List of basic blocks that are created during CFG creation
379 Block_List _blocks;
380
381 // Count of basic blocks
382 uint _number_of_blocks;
383
384 // Arena for the blocks to be stored in
385 Arena* _block_arena;
386
387 // Info used for scheduling
388 PhaseChaitin* _regalloc;
389
390 // Register pressure heuristic used?
391 bool _scheduling_for_pressure;
392
393 // The matcher for this compilation
394 Matcher& _matcher;
395
396 // Map nodes to owning basic block
397 Block_Array _node_to_block_mapping;
398
399 // Loop from the root
400 CFGLoop* _root_loop;
401
402 // Outmost loop frequency
403 double _outer_loop_frequency;
404
405 // Per node latency estimation, valid only during GCM
406 GrowableArray<uint>* _node_latency;
407
408 // Build a proper looking cfg. Return count of basic blocks
409 uint build_cfg();
410
411 // Build the dominator tree so that we know where we can move instructions
412 void build_dominator_tree();
413
414 // Estimate block frequencies based on IfNode probabilities, so that we know where we want to move instructions
415 void estimate_block_frequency();
416
417 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific
418 // basic blocks; i.e. _node_to_block_mapping now maps _idx for all Nodes to some Block.
419 // Move nodes to ensure correctness from GVN and also try to move nodes out of loops.
420 void global_code_motion();
421
422 // Schedule Nodes early in their basic blocks.
423 bool schedule_early(VectorSet &visited, Node_Stack &roots);
424
425 // For each node, find the latest block it can be scheduled into
426 // and then select the cheapest block between the latest and earliest
427 // block to place the node.
428 void schedule_late(VectorSet &visited, Node_Stack &stack);
429
430 // Compute the (backwards) latency of a node from a single use
431 int latency_from_use(Node *n, const Node *def, Node *use);
432
433 // Compute the (backwards) latency of a node from the uses of this instruction
434 void partial_latency_of_defs(Node *n);
435
436 // Compute the instruction global latency with a backwards walk
437 void compute_latencies_backwards(VectorSet &visited, Node_Stack &stack);
438
439 // Check if a block between early and LCA block of uses is cheaper by
440 // frequency-based policy, latency-based policy and random-based policy
441 bool is_cheaper_block(Block* LCA, Node* self, uint target_latency,
442 uint end_latency, double least_freq,
443 int cand_cnt, bool in_latency);
444
445 // Pick a block between early and late that is a cheaper alternative
446 // to late. Helper for schedule_late.
447 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
448
449 bool schedule_local(Block* block, GrowableArray<int>& ready_cnt, VectorSet& next_call, intptr_t* recacl_pressure_nodes);
450 void set_next_call(const Block* block, Node* n, VectorSet& next_call) const;
451 void needed_for_next_call(Block* block, Node* this_call, VectorSet& next_call);
452
453 // Perform basic-block local scheduling
454 Node* select(Block* block, Node_List& worklist, GrowableArray<int>& ready_cnt, VectorSet& next_call, uint sched_slot,
455 intptr_t* recacl_pressure_nodes);
456 void adjust_register_pressure(Node* n, Block* block, intptr_t *recalc_pressure_nodes, bool finalize_mode);
457
458 // Schedule a call next in the block
459 uint sched_call(Block* block, uint node_cnt, Node_List& worklist, GrowableArray<int>& ready_cnt, MachCallNode* mcall, VectorSet& next_call);
460
461 // Cleanup if any code lands between a Call and his Catch
462 void call_catch_cleanup(Block* block);
463
464 Node* catch_cleanup_find_cloned_def(Block* use_blk, Node* def, Block* def_blk, int n_clone_idx);
465 void catch_cleanup_inter_block(Node *use, Block *use_blk, Node *def, Block *def_blk, int n_clone_idx);
466
467 // Detect implicit-null-check opportunities. Basically, find null checks
468 // with suitable memory ops nearby. Use the memory op to do the null check.
469 // I can generate a memory op if there is not one nearby.
470 void implicit_null_check(Block* block, Node *proj, Node *val, int allowed_reasons);
471
472 // Perform a Depth First Search (DFS).
473 // Setup 'vertex' as DFS to vertex mapping.
474 // Setup 'semi' as vertex to DFS mapping.
475 // Set 'parent' to DFS parent.
476 uint do_DFS(Tarjan* tarjan, uint rpo_counter);
477
478 // Helper function to insert a node into a block
479 void schedule_node_into_block( Node *n, Block *b );
480
481 void replace_block_proj_ctrl( Node *n );
482
483 // Set the basic block for pinned Nodes
484 void schedule_pinned_nodes( VectorSet &visited );
485
486 // I'll need a few machine-specific GotoNodes. Clone from this one.
487 // Used when building the CFG and creating end nodes for blocks.
488 MachNode* _goto;
489
490 Block* raise_above_anti_dependences(Block* LCA, Node* load, bool verify = false);
491 void verify_anti_dependences(Block* LCA, Node* load) const {
492 assert(LCA == get_block_for_node(load), "should already be scheduled");
493 const_cast<PhaseCFG*>(this)->raise_above_anti_dependences(LCA, load, true);
494 }
495
496 bool move_to_next(Block* bx, uint b_index);
497 void move_to_end(Block* bx, uint b_index);
498
499 void insert_goto_at(uint block_no, uint succ_no);
500
501 // Check for NeverBranch at block end. This needs to become a GOTO to the
502 // true target. NeverBranch are treated as a conditional branch that always
503 // goes the same direction for most of the optimizer and are used to give a
504 // fake exit path to infinite loops. At this late stage they need to turn
505 // into Goto's so that when you enter the infinite loop you indeed hang.
506 void convert_NeverBranch_to_Goto(Block *b);
507
508 CFGLoop* create_loop_tree();
509 bool is_dominator(Node* dom_node, Node* node);
510 bool is_CFG(Node* n);
511 bool is_control_proj_or_safepoint(Node* n) const;
512 Block* find_block_for_node(Node* n) const;
513 bool is_dominating_control(Node* dom_ctrl, Node* n);
514 #ifndef PRODUCT
515 bool _trace_opto_pipelining; // tracing flag
516 #endif
517
518 public:
519 PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher);
520
521 void set_latency_for_node(Node* node, int latency) {
522 _node_latency->at_put_grow(node->_idx, latency);
523 }
524
525 uint get_latency_for_node(Node* node) {
526 return _node_latency->at_grow(node->_idx);
527 }
528
529 // Get the outer most frequency
530 double get_outer_loop_frequency() const {
531 return _outer_loop_frequency;
532 }
533
534 // Get the root node of the CFG
535 RootNode* get_root_node() const {
536 return _root;
537 }
538
539 // Get the block of the root node
540 Block* get_root_block() const {
541 return _root_block;
542 }
543
544 // Add a block at a position and moves the later ones one step
545 void add_block_at(uint pos, Block* block) {
546 _blocks.insert(pos, block);
547 _number_of_blocks++;
548 }
549
550 // Adds a block to the top of the block list
551 void add_block(Block* block) {
552 _blocks.push(block);
553 _number_of_blocks++;
554 }
555
556 // Clear the list of blocks
557 void clear_blocks() {
558 _blocks.reset();
559 _number_of_blocks = 0;
560 }
561
562 // Get the block at position pos in _blocks
563 Block* get_block(uint pos) const {
564 return _blocks[pos];
565 }
566
567 // Number of blocks
568 uint number_of_blocks() const {
569 return _number_of_blocks;
570 }
571
572 // set which block this node should reside in
573 void map_node_to_block(const Node* node, Block* block) {
574 _node_to_block_mapping.map(node->_idx, block);
575 }
576
577 // removes the mapping from a node to a block
578 void unmap_node_from_block(const Node* node) {
579 _node_to_block_mapping.map(node->_idx, nullptr);
580 }
581
582 // get the block in which this node resides
583 Block* get_block_for_node(const Node* node) const {
584 return _node_to_block_mapping[node->_idx];
585 }
586
587 // does this node reside in a block; return true
588 bool has_block(const Node* node) const {
589 return (_node_to_block_mapping.lookup(node->_idx) != nullptr);
590 }
591
592 // Use frequency calculations and code shape to predict if the block
593 // is uncommon.
594 bool is_uncommon(const Block* block);
595
596 #ifdef ASSERT
597 Unique_Node_List _raw_oops;
598 #endif
599
600 // Do global code motion by first building dominator tree and estimate block frequency
601 // Returns true on success
602 bool do_global_code_motion();
603
604 // Compute the (backwards) latency of a node from the uses
605 void latency_from_uses(Node *n);
606
607 // Set loop alignment
608 void set_loop_alignment();
609
610 // Remove empty basic blocks
611 void remove_empty_blocks();
612 Block *fixup_trap_based_check(Node *branch, Block *block, int block_pos, Block *bnext);
613 void fixup_flow();
614 // Remove all blocks that are transitively unreachable. Such blocks can be
615 // found e.g. after PhaseCFG::convert_NeverBranch_to_Goto(). This function
616 // assumes post-fixup_flow() block indices (Block::_pre_order, Block::_rpo).
617 void remove_unreachable_blocks();
618
619 // Insert a node into a block at index and map the node to the block
620 void insert(Block *b, uint idx, Node *n) {
621 b->insert_node(n , idx);
622 map_node_to_block(n, b);
623 }
624
625 // Check all nodes and postalloc_expand them if necessary.
626 void postalloc_expand(PhaseRegAlloc* _ra);
627
628 #ifndef PRODUCT
629 bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
630
631 // Debugging print of CFG
632 void dump( ) const; // CFG only
633 void _dump_cfg( const Node *end, VectorSet &visited ) const;
634 void dump_headers();
635 #else
636 bool trace_opto_pipelining() const { return false; }
637 #endif
638
639 bool unrelated_load_in_store_null_block(Node* store, Node* load);
640
641 // Check that block b is in the home loop (or an ancestor) of n, if n is a
642 // memory writer.
643 void verify_memory_writer_placement(const Block* b, const Node* n) const NOT_DEBUG_RETURN;
644 // Check local dominator tree invariants.
645 void verify_dominator_tree() const NOT_DEBUG_RETURN;
646 void verify() const NOT_DEBUG_RETURN;
647 };
648
649
650 //------------------------------UnionFind--------------------------------------
651 // Map Block indices to a block-index for a cfg-cover.
652 // Array lookup in the optimized case.
653 class UnionFind : public ResourceObj {
654 uint _cnt, _max;
655 uint* _indices;
656 ReallocMark _nesting; // Safety checks for arena reallocation
657 public:
658 UnionFind( uint max );
659 void reset( uint max ); // Reset to identity map for [0..max]
660
661 uint lookup( uint nidx ) const {
662 return _indices[nidx];
663 }
664 uint operator[] (uint nidx) const { return lookup(nidx); }
665
666 void map( uint from_idx, uint to_idx ) {
667 assert( from_idx < _cnt, "oob" );
668 _indices[from_idx] = to_idx;
669 }
670 void extend( uint from_idx, uint to_idx );
671
672 uint Size() const { return _cnt; }
673
674 uint Find( uint idx ) {
675 assert( idx < 65536, "Must fit into uint");
676 uint uf_idx = lookup(idx);
677 return (uf_idx == idx) ? uf_idx : Find_compress(idx);
678 }
679 uint Find_compress( uint idx );
680 uint Find_const( uint idx ) const;
681 void Union( uint idx1, uint idx2 );
682
683 };
684
685 //----------------------------BlockProbPair---------------------------
686 // Ordered pair of Node*.
687 class BlockProbPair {
688 protected:
689 Block* _target; // block target
690 double _prob; // probability of edge to block
691 public:
692 BlockProbPair() : _target(nullptr), _prob(0.0) {}
693 BlockProbPair(Block* b, double p) : _target(b), _prob(p) {}
694
695 Block* get_target() const { return _target; }
696 double get_prob() const { return _prob; }
697 };
698
699 //------------------------------CFGLoop-------------------------------------------
700 class CFGLoop : public CFGElement {
701 int _id;
702 int _depth;
703 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null
704 CFGLoop *_sibling; // null terminated list
705 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops
706 GrowableArray<CFGElement*> _members; // list of members of loop
707 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
708 double _exit_prob; // probability any loop exit is taken on a single loop iteration
709 void update_succ_freq(Block* b, double freq);
710
711 public:
712 CFGLoop(int id) :
713 CFGElement(),
714 _id(id),
715 _depth(0),
716 _parent(nullptr),
717 _sibling(nullptr),
718 _child(nullptr),
719 _exit_prob(1.0f) {}
720 CFGLoop* parent() { return _parent; }
721 void push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg);
722 void add_member(CFGElement *s) { _members.push(s); }
723 void add_nested_loop(CFGLoop* cl);
724 Block* head() {
725 assert(_members.at(0)->is_block(), "head must be a block");
726 Block* hd = _members.at(0)->as_Block();
727 assert(hd->_loop == this, "just checking");
728 assert(hd->head()->is_Loop(), "must begin with loop head node");
729 return hd;
730 }
731 Block* backedge_block(); // Return the block on the backedge of the loop (else null)
732 void compute_loop_depth(int depth);
733 void compute_freq(); // compute frequency with loop assuming head freq 1.0f
734 void scale_freq(); // scale frequency by loop trip count (including outer loops)
735 double outer_loop_freq() const; // frequency of outer loop
736 bool in_loop_nest(Block* b);
737 double trip_count() const { return 1.0 / _exit_prob; }
738 virtual bool is_loop() { return true; }
739 int id() { return _id; }
740 int depth() { return _depth; }
741
742 #ifndef PRODUCT
743 void dump( ) const;
744 void dump_tree() const;
745 #endif
746 };
747
748
749 //----------------------------------CFGEdge------------------------------------
750 // A edge between two basic blocks that will be embodied by a branch or a
751 // fall-through.
752 class CFGEdge : public ResourceObj {
753 private:
754 Block * _from; // Source basic block
755 Block * _to; // Destination basic block
756 double _freq; // Execution frequency (estimate)
757 int _state;
758 bool _infrequent;
759 int _from_pct;
760 int _to_pct;
761
762 // Private accessors
763 int from_pct() const { return _from_pct; }
764 int to_pct() const { return _to_pct; }
765 int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; }
766 int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; }
767
768 public:
769 enum {
770 open, // initial edge state; unprocessed
771 connected, // edge used to connect two traces together
772 interior // edge is interior to trace (could be backedge)
773 };
774
775 CFGEdge(Block *from, Block *to, double freq, int from_pct, int to_pct) :
776 _from(from), _to(to), _freq(freq),
777 _state(open), _from_pct(from_pct), _to_pct(to_pct) {
778 _infrequent = from_infrequent() || to_infrequent();
779 }
780
781 double freq() const { return _freq; }
782 Block* from() const { return _from; }
783 Block* to () const { return _to; }
784 int infrequent() const { return _infrequent; }
785 int state() const { return _state; }
786
787 void set_state(int state) { _state = state; }
788
789 #ifndef PRODUCT
790 void dump( ) const;
791 #endif
792 };
793
794
795 //-----------------------------------Trace-------------------------------------
796 // An ordered list of basic blocks.
797 class Trace : public ResourceObj {
798 private:
799 uint _id; // Unique Trace id (derived from initial block)
800 Block ** _next_list; // Array mapping index to next block
801 Block ** _prev_list; // Array mapping index to previous block
802 Block * _first; // First block in the trace
803 Block * _last; // Last block in the trace
804
805 void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; }
806
807 // Return the block that precedes "b" in the trace.
808 Block * prev(Block *b) const { return _prev_list[b->_pre_order]; }
809 void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; }
810
811 // We've discovered a loop in this trace. Reset last to be "b", and first as
812 // the block following "b
813 void break_loop_after(Block *b) {
814 _last = b;
815 _first = next(b);
816 set_prev(_first, nullptr);
817 set_next(_last, nullptr);
818 }
819
820 public:
821
822 Trace(Block *b, Block **next_list, Block **prev_list) :
823 _id(b->_pre_order),
824 _next_list(next_list),
825 _prev_list(prev_list),
826 _first(b),
827 _last(b) {
828 set_next(b, nullptr);
829 set_prev(b, nullptr);
830 };
831
832 // Return the id number
833 uint id() const { return _id; }
834 void set_id(uint id) { _id = id; }
835
836 // Return the first block in the trace
837 Block * first_block() const { return _first; }
838
839 // Return the last block in the trace
840 Block * last_block() const { return _last; }
841
842 // Return the block that follows "b" in the trace.
843 Block * next(Block *b) const { return _next_list[b->_pre_order]; }
844
845 // Insert a trace in the middle of this one after b
846 void insert_after(Block *b, Trace *tr) {
847 set_next(tr->last_block(), next(b));
848 if (next(b) != nullptr) {
849 set_prev(next(b), tr->last_block());
850 }
851
852 set_next(b, tr->first_block());
853 set_prev(tr->first_block(), b);
854
855 if (b == _last) {
856 _last = tr->last_block();
857 }
858 }
859
860 void insert_before(Block *b, Trace *tr) {
861 Block *p = prev(b);
862 assert(p != nullptr, "use append instead");
863 insert_after(p, tr);
864 }
865
866 // Append another trace to this one.
867 void append(Trace *tr) {
868 insert_after(_last, tr);
869 }
870
871 // Append a block at the end of this trace
872 void append(Block *b) {
873 set_next(_last, b);
874 set_prev(b, _last);
875 _last = b;
876 }
877
878 bool backedge(CFGEdge *e);
879
880 #ifndef PRODUCT
881 void dump( ) const;
882 #endif
883 };
884
885 //------------------------------PhaseBlockLayout-------------------------------
886 // Rearrange blocks into some canonical order, based on edges and their frequencies
887 class PhaseBlockLayout : public Phase {
888 PhaseCFG &_cfg; // Control flow graph
889
890 GrowableArray<CFGEdge *> *edges;
891 Trace **traces;
892 Block **next;
893 Block **prev;
894 UnionFind *uf;
895
896 // Given a block, find its encompassing Trace
897 Trace * trace(Block *b) {
898 return traces[uf->Find_compress(b->_pre_order)];
899 }
900 public:
901 PhaseBlockLayout(PhaseCFG &cfg);
902
903 void find_edges();
904 void grow_traces();
905 void merge_traces(bool loose_connections);
906 void reorder_traces(int count);
907 void union_traces(Trace* from, Trace* to);
908 };
909
910 #endif // SHARE_OPTO_BLOCK_HPP