1 /*
2 * Copyright 1997-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // Optimization - Graph Style
26
27 #include "incls/_precompiled.incl"
28 #include "incls/_block.cpp.incl"
29
30
31 //-----------------------------------------------------------------------------
32 void Block_Array::grow( uint i ) {
33 assert(i >= Max(), "must be an overflow");
34 debug_only(_limit = i+1);
35 if( i < _size ) return;
36 if( !_size ) {
37 _size = 1;
38 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) );
39 _blocks[0] = NULL;
40 }
41 uint old = _size;
42 while( i >= _size ) _size <<= 1; // Double to fit
43 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*));
44 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) );
45 }
46
47 //=============================================================================
48 void Block_List::remove(uint i) {
49 assert(i < _cnt, "index out of bounds");
50 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*)));
51 pop(); // shrink list by one block
52 }
53
54 void Block_List::insert(uint i, Block *b) {
55 push(b); // grow list by one block
56 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*)));
57 _blocks[i] = b;
58 }
59
60 #ifndef PRODUCT
61 void Block_List::print() {
62 for (uint i=0; i < size(); i++) {
63 tty->print("B%d ", _blocks[i]->_pre_order);
64 }
65 tty->print("size = %d\n", size());
66 }
67 #endif
68
69 //=============================================================================
70
71 uint Block::code_alignment() {
72 // Check for Root block
73 if( _pre_order == 0 ) return CodeEntryAlignment;
74 // Check for Start block
75 if( _pre_order == 1 ) return InteriorEntryAlignment;
76 // Check for loop alignment
77 if (has_loop_alignment()) return loop_alignment();
78
79 return 1; // no particular alignment
80 }
81
82 uint Block::compute_loop_alignment() {
83 Node *h = head();
84 if( h->is_Loop() && h->as_Loop()->is_inner_loop() ) {
85 // Pre- and post-loops have low trip count so do not bother with
86 // NOPs for align loop head. The constants are hidden from tuning
87 // but only because my "divide by 4" heuristic surely gets nearly
88 // all possible gain (a "do not align at all" heuristic has a
89 // chance of getting a really tiny gain).
90 if( h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() ||
91 h->as_CountedLoop()->is_post_loop()) )
92 return (OptoLoopAlignment > 4) ? (OptoLoopAlignment>>2) : 1;
93 // Loops with low backedge frequency should not be aligned.
94 Node *n = h->in(LoopNode::LoopBackControl)->in(0);
95 if( n->is_MachIf() && n->as_MachIf()->_prob < 0.01 ) {
96 return 1; // Loop does not loop, more often than not!
97 }
98 return OptoLoopAlignment; // Otherwise align loop head
99 }
100
101 return 1; // no particular alignment
102 }
103
104 //-----------------------------------------------------------------------------
105 // Compute the size of first 'inst_cnt' instructions in this block.
106 // Return the number of instructions left to compute if the block has
107 // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size
108 // exceeds OptoLoopAlignment.
109 uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt,
110 PhaseRegAlloc* ra) {
111 uint last_inst = _nodes.size();
112 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) {
113 uint inst_size = _nodes[j]->size(ra);
114 if( inst_size > 0 ) {
115 inst_cnt--;
116 uint sz = sum_size + inst_size;
117 if( sz <= (uint)OptoLoopAlignment ) {
118 // Compute size of instructions which fit into fetch buffer only
119 // since all inst_cnt instructions will not fit even if we align them.
120 sum_size = sz;
121 } else {
122 return 0;
123 }
124 }
125 }
126 return inst_cnt;
127 }
128
129 //-----------------------------------------------------------------------------
130 uint Block::find_node( const Node *n ) const {
131 for( uint i = 0; i < _nodes.size(); i++ ) {
132 if( _nodes[i] == n )
133 return i;
134 }
135 ShouldNotReachHere();
136 return 0;
137 }
138
139 // Find and remove n from block list
140 void Block::find_remove( const Node *n ) {
141 _nodes.remove(find_node(n));
142 }
143
144 //------------------------------is_Empty---------------------------------------
145 // Return empty status of a block. Empty blocks contain only the head, other
146 // ideal nodes, and an optional trailing goto.
147 int Block::is_Empty() const {
148
149 // Root or start block is not considered empty
150 if (head()->is_Root() || head()->is_Start()) {
151 return not_empty;
152 }
153
154 int success_result = completely_empty;
155 int end_idx = _nodes.size()-1;
156
157 // Check for ending goto
158 if ((end_idx > 0) && (_nodes[end_idx]->is_Goto())) {
159 success_result = empty_with_goto;
160 end_idx--;
161 }
162
163 // Unreachable blocks are considered empty
164 if (num_preds() <= 1) {
165 return success_result;
166 }
167
168 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes
169 // turn directly into code, because only MachNodes have non-trivial
170 // emit() functions.
171 while ((end_idx > 0) && !_nodes[end_idx]->is_Mach()) {
172 end_idx--;
173 }
174
175 // No room for any interesting instructions?
176 if (end_idx == 0) {
177 return success_result;
178 }
179
180 return not_empty;
181 }
182
183 //------------------------------has_uncommon_code------------------------------
184 // Return true if the block's code implies that it is not likely to be
185 // executed infrequently. Check to see if the block ends in a Halt or
186 // a low probability call.
187 bool Block::has_uncommon_code() const {
188 Node* en = end();
189
190 if (en->is_Goto())
191 en = en->in(0);
192 if (en->is_Catch())
193 en = en->in(0);
194 if (en->is_Proj() && en->in(0)->is_MachCall()) {
195 MachCallNode* call = en->in(0)->as_MachCall();
196 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) {
197 // This is true for slow-path stubs like new_{instance,array},
198 // slow_arraycopy, complete_monitor_locking, uncommon_trap.
199 // The magic number corresponds to the probability of an uncommon_trap,
200 // even though it is a count not a probability.
201 return true;
202 }
203 }
204
205 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode();
206 return op == Op_Halt;
207 }
208
209 //------------------------------is_uncommon------------------------------------
210 // True if block is low enough frequency or guarded by a test which
211 // mostly does not go here.
212 bool Block::is_uncommon( Block_Array &bbs ) const {
213 // Initial blocks must never be moved, so are never uncommon.
214 if (head()->is_Root() || head()->is_Start()) return false;
215
216 // Check for way-low freq
217 if( _freq < BLOCK_FREQUENCY(0.00001f) ) return true;
218
219 // Look for code shape indicating uncommon_trap or slow path
220 if (has_uncommon_code()) return true;
221
222 const float epsilon = 0.05f;
223 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon);
224 uint uncommon_preds = 0;
225 uint freq_preds = 0;
226 uint uncommon_for_freq_preds = 0;
227
228 for( uint i=1; i<num_preds(); i++ ) {
229 Block* guard = bbs[pred(i)->_idx];
230 // Check to see if this block follows its guard 1 time out of 10000
231 // or less.
232 //
233 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which
234 // we intend to be "uncommon", such as slow-path TLE allocation,
235 // predicted call failure, and uncommon trap triggers.
236 //
237 // Use an epsilon value of 5% to allow for variability in frequency
238 // predictions and floating point calculations. The net effect is
239 // that guard_factor is set to 9500.
240 //
241 // Ignore low-frequency blocks.
242 // The next check is (guard->_freq < 1.e-5 * 9500.).
243 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) {
244 uncommon_preds++;
245 } else {
246 freq_preds++;
247 if( _freq < guard->_freq * guard_factor ) {
248 uncommon_for_freq_preds++;
249 }
250 }
251 }
252 if( num_preds() > 1 &&
253 // The block is uncommon if all preds are uncommon or
254 (uncommon_preds == (num_preds()-1) ||
255 // it is uncommon for all frequent preds.
256 uncommon_for_freq_preds == freq_preds) ) {
257 return true;
258 }
259 return false;
260 }
261
262 //------------------------------dump-------------------------------------------
263 #ifndef PRODUCT
264 void Block::dump_bidx(const Block* orig) const {
265 if (_pre_order) tty->print("B%d",_pre_order);
266 else tty->print("N%d", head()->_idx);
267
268 if (Verbose && orig != this) {
269 // Dump the original block's idx
270 tty->print(" (");
271 orig->dump_bidx(orig);
272 tty->print(")");
273 }
274 }
275
276 void Block::dump_pred(const Block_Array *bbs, Block* orig) const {
277 if (is_connector()) {
278 for (uint i=1; i<num_preds(); i++) {
279 Block *p = ((*bbs)[pred(i)->_idx]);
280 p->dump_pred(bbs, orig);
281 }
282 } else {
283 dump_bidx(orig);
284 tty->print(" ");
285 }
286 }
287
288 void Block::dump_head( const Block_Array *bbs ) const {
289 // Print the basic block
290 dump_bidx(this);
291 tty->print(": #\t");
292
293 // Print the incoming CFG edges and the outgoing CFG edges
294 for( uint i=0; i<_num_succs; i++ ) {
295 non_connector_successor(i)->dump_bidx(_succs[i]);
296 tty->print(" ");
297 }
298 tty->print("<- ");
299 if( head()->is_block_start() ) {
300 for (uint i=1; i<num_preds(); i++) {
301 Node *s = pred(i);
302 if (bbs) {
303 Block *p = (*bbs)[s->_idx];
304 p->dump_pred(bbs, p);
305 } else {
306 while (!s->is_block_start())
307 s = s->in(0);
308 tty->print("N%d ", s->_idx );
309 }
310 }
311 } else
312 tty->print("BLOCK HEAD IS JUNK ");
313
314 // Print loop, if any
315 const Block *bhead = this; // Head of self-loop
316 Node *bh = bhead->head();
317 if( bbs && bh->is_Loop() && !head()->is_Root() ) {
318 LoopNode *loop = bh->as_Loop();
319 const Block *bx = (*bbs)[loop->in(LoopNode::LoopBackControl)->_idx];
320 while (bx->is_connector()) {
321 bx = (*bbs)[bx->pred(1)->_idx];
322 }
323 tty->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order);
324 // Dump any loop-specific bits, especially for CountedLoops.
325 loop->dump_spec(tty);
326 } else if (has_loop_alignment()) {
327 tty->print(" top-of-loop");
328 }
329 tty->print(" Freq: %g",_freq);
330 if( Verbose || WizardMode ) {
331 tty->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth);
332 tty->print(" RegPressure: %d",_reg_pressure);
333 tty->print(" IHRP Index: %d",_ihrp_index);
334 tty->print(" FRegPressure: %d",_freg_pressure);
335 tty->print(" FHRP Index: %d",_fhrp_index);
336 }
337 tty->print_cr("");
338 }
339
340 void Block::dump() const { dump(0); }
341
342 void Block::dump( const Block_Array *bbs ) const {
343 dump_head(bbs);
344 uint cnt = _nodes.size();
345 for( uint i=0; i<cnt; i++ )
346 _nodes[i]->dump();
347 tty->print("\n");
348 }
349 #endif
350
351 //=============================================================================
352 //------------------------------PhaseCFG---------------------------------------
353 PhaseCFG::PhaseCFG( Arena *a, RootNode *r, Matcher &m ) :
354 Phase(CFG),
355 _bbs(a),
356 _root(r)
357 #ifndef PRODUCT
358 , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining"))
359 #endif
360 {
361 ResourceMark rm;
362 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode,
363 // then Match it into a machine-specific Node. Then clone the machine
364 // Node on demand.
365 Node *x = new (C, 1) GotoNode(NULL);
366 x->init_req(0, x);
367 _goto = m.match_tree(x);
368 assert(_goto != NULL, "");
369 _goto->set_req(0,_goto);
370
371 // Build the CFG in Reverse Post Order
372 _num_blocks = build_cfg();
373 _broot = _bbs[_root->_idx];
374 }
375
376 //------------------------------build_cfg--------------------------------------
377 // Build a proper looking CFG. Make every block begin with either a StartNode
378 // or a RegionNode. Make every block end with either a Goto, If or Return.
379 // The RootNode both starts and ends it's own block. Do this with a recursive
380 // backwards walk over the control edges.
381 uint PhaseCFG::build_cfg() {
382 Arena *a = Thread::current()->resource_area();
383 VectorSet visited(a);
384
385 // Allocate stack with enough space to avoid frequent realloc
386 Node_Stack nstack(a, C->unique() >> 1);
387 nstack.push(_root, 0);
388 uint sum = 0; // Counter for blocks
389
390 while (nstack.is_nonempty()) {
391 // node and in's index from stack's top
392 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack
393 // only nodes which point to the start of basic block (see below).
394 Node *np = nstack.node();
395 // idx > 0, except for the first node (_root) pushed on stack
396 // at the beginning when idx == 0.
397 // We will use the condition (idx == 0) later to end the build.
398 uint idx = nstack.index();
399 Node *proj = np->in(idx);
400 const Node *x = proj->is_block_proj();
401 // Does the block end with a proper block-ending Node? One of Return,
402 // If or Goto? (This check should be done for visited nodes also).
403 if (x == NULL) { // Does not end right...
404 Node *g = _goto->clone(); // Force it to end in a Goto
405 g->set_req(0, proj);
406 np->set_req(idx, g);
407 x = proj = g;
408 }
409 if (!visited.test_set(x->_idx)) { // Visit this block once
410 // Skip any control-pinned middle'in stuff
411 Node *p = proj;
412 do {
413 proj = p; // Update pointer to last Control
414 p = p->in(0); // Move control forward
415 } while( !p->is_block_proj() &&
416 !p->is_block_start() );
417 // Make the block begin with one of Region or StartNode.
418 if( !p->is_block_start() ) {
419 RegionNode *r = new (C, 2) RegionNode( 2 );
420 r->init_req(1, p); // Insert RegionNode in the way
421 proj->set_req(0, r); // Insert RegionNode in the way
422 p = r;
423 }
424 // 'p' now points to the start of this basic block
425
426 // Put self in array of basic blocks
427 Block *bb = new (_bbs._arena) Block(_bbs._arena,p);
428 _bbs.map(p->_idx,bb);
429 _bbs.map(x->_idx,bb);
430 if( x != p ) // Only for root is x == p
431 bb->_nodes.push((Node*)x);
432
433 // Now handle predecessors
434 ++sum; // Count 1 for self block
435 uint cnt = bb->num_preds();
436 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors
437 Node *prevproj = p->in(i); // Get prior input
438 assert( !prevproj->is_Con(), "dead input not removed" );
439 // Check to see if p->in(i) is a "control-dependent" CFG edge -
440 // i.e., it splits at the source (via an IF or SWITCH) and merges
441 // at the destination (via a many-input Region).
442 // This breaks critical edges. The RegionNode to start the block
443 // will be added when <p,i> is pulled off the node stack
444 if ( cnt > 2 ) { // Merging many things?
445 assert( prevproj== bb->pred(i),"");
446 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge?
447 // Force a block on the control-dependent edge
448 Node *g = _goto->clone(); // Force it to end in a Goto
449 g->set_req(0,prevproj);
450 p->set_req(i,g);
451 }
452 }
453 nstack.push(p, i); // 'p' is RegionNode or StartNode
454 }
455 } else { // Post-processing visited nodes
456 nstack.pop(); // remove node from stack
457 // Check if it the fist node pushed on stack at the beginning.
458 if (idx == 0) break; // end of the build
459 // Find predecessor basic block
460 Block *pb = _bbs[x->_idx];
461 // Insert into nodes array, if not already there
462 if( !_bbs.lookup(proj->_idx) ) {
463 assert( x != proj, "" );
464 // Map basic block of projection
465 _bbs.map(proj->_idx,pb);
466 pb->_nodes.push(proj);
467 }
468 // Insert self as a child of my predecessor block
469 pb->_succs.map(pb->_num_succs++, _bbs[np->_idx]);
470 assert( pb->_nodes[ pb->_nodes.size() - pb->_num_succs ]->is_block_proj(),
471 "too many control users, not a CFG?" );
472 }
473 }
474 // Return number of basic blocks for all children and self
475 return sum;
476 }
477
478 //------------------------------insert_goto_at---------------------------------
479 // Inserts a goto & corresponding basic block between
480 // block[block_no] and its succ_no'th successor block
481 void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) {
482 // get block with block_no
483 assert(block_no < _num_blocks, "illegal block number");
484 Block* in = _blocks[block_no];
485 // get successor block succ_no
486 assert(succ_no < in->_num_succs, "illegal successor number");
487 Block* out = in->_succs[succ_no];
488 // Compute frequency of the new block. Do this before inserting
489 // new block in case succ_prob() needs to infer the probability from
490 // surrounding blocks.
491 float freq = in->_freq * in->succ_prob(succ_no);
492 // get ProjNode corresponding to the succ_no'th successor of the in block
493 ProjNode* proj = in->_nodes[in->_nodes.size() - in->_num_succs + succ_no]->as_Proj();
494 // create region for basic block
495 RegionNode* region = new (C, 2) RegionNode(2);
496 region->init_req(1, proj);
497 // setup corresponding basic block
498 Block* block = new (_bbs._arena) Block(_bbs._arena, region);
499 _bbs.map(region->_idx, block);
500 C->regalloc()->set_bad(region->_idx);
501 // add a goto node
502 Node* gto = _goto->clone(); // get a new goto node
503 gto->set_req(0, region);
504 // add it to the basic block
505 block->_nodes.push(gto);
506 _bbs.map(gto->_idx, block);
507 C->regalloc()->set_bad(gto->_idx);
508 // hook up successor block
509 block->_succs.map(block->_num_succs++, out);
510 // remap successor's predecessors if necessary
511 for (uint i = 1; i < out->num_preds(); i++) {
512 if (out->pred(i) == proj) out->head()->set_req(i, gto);
513 }
514 // remap predecessor's successor to new block
515 in->_succs.map(succ_no, block);
516 // Set the frequency of the new block
517 block->_freq = freq;
518 // add new basic block to basic block list
519 _blocks.insert(block_no + 1, block);
520 _num_blocks++;
521 }
522
523 //------------------------------no_flip_branch---------------------------------
524 // Does this block end in a multiway branch that cannot have the default case
525 // flipped for another case?
526 static bool no_flip_branch( Block *b ) {
527 int branch_idx = b->_nodes.size() - b->_num_succs-1;
528 if( branch_idx < 1 ) return false;
529 Node *bra = b->_nodes[branch_idx];
530 if( bra->is_Catch() )
531 return true;
532 if( bra->is_Mach() ) {
533 if( bra->is_MachNullCheck() )
534 return true;
535 int iop = bra->as_Mach()->ideal_Opcode();
536 if( iop == Op_FastLock || iop == Op_FastUnlock )
537 return true;
538 }
539 return false;
540 }
541
542 //------------------------------convert_NeverBranch_to_Goto--------------------
543 // Check for NeverBranch at block end. This needs to become a GOTO to the
544 // true target. NeverBranch are treated as a conditional branch that always
545 // goes the same direction for most of the optimizer and are used to give a
546 // fake exit path to infinite loops. At this late stage they need to turn
547 // into Goto's so that when you enter the infinite loop you indeed hang.
548 void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) {
549 // Find true target
550 int end_idx = b->end_idx();
551 int idx = b->_nodes[end_idx+1]->as_Proj()->_con;
552 Block *succ = b->_succs[idx];
553 Node* gto = _goto->clone(); // get a new goto node
554 gto->set_req(0, b->head());
555 Node *bp = b->_nodes[end_idx];
556 b->_nodes.map(end_idx,gto); // Slam over NeverBranch
557 _bbs.map(gto->_idx, b);
558 C->regalloc()->set_bad(gto->_idx);
559 b->_nodes.pop(); // Yank projections
560 b->_nodes.pop(); // Yank projections
561 b->_succs.map(0,succ); // Map only successor
562 b->_num_succs = 1;
563 // remap successor's predecessors if necessary
564 uint j;
565 for( j = 1; j < succ->num_preds(); j++)
566 if( succ->pred(j)->in(0) == bp )
567 succ->head()->set_req(j, gto);
568 // Kill alternate exit path
569 Block *dead = b->_succs[1-idx];
570 for( j = 1; j < dead->num_preds(); j++)
571 if( dead->pred(j)->in(0) == bp )
572 break;
573 // Scan through block, yanking dead path from
574 // all regions and phis.
575 dead->head()->del_req(j);
576 for( int k = 1; dead->_nodes[k]->is_Phi(); k++ )
577 dead->_nodes[k]->del_req(j);
578 }
579
580 //------------------------------move_to_next-----------------------------------
581 // Helper function to move block bx to the slot following b_index. Return
582 // true if the move is successful, otherwise false
583 bool PhaseCFG::move_to_next(Block* bx, uint b_index) {
584 if (bx == NULL) return false;
585
586 // Return false if bx is already scheduled.
587 uint bx_index = bx->_pre_order;
588 if ((bx_index <= b_index) && (_blocks[bx_index] == bx)) {
589 return false;
590 }
591
592 // Find the current index of block bx on the block list
593 bx_index = b_index + 1;
594 while( bx_index < _num_blocks && _blocks[bx_index] != bx ) bx_index++;
595 assert(_blocks[bx_index] == bx, "block not found");
596
597 // If the previous block conditionally falls into bx, return false,
598 // because moving bx will create an extra jump.
599 for(uint k = 1; k < bx->num_preds(); k++ ) {
600 Block* pred = _bbs[bx->pred(k)->_idx];
601 if (pred == _blocks[bx_index-1]) {
602 if (pred->_num_succs != 1) {
603 return false;
604 }
605 }
606 }
607
608 // Reinsert bx just past block 'b'
609 _blocks.remove(bx_index);
610 _blocks.insert(b_index + 1, bx);
611 return true;
612 }
613
614 //------------------------------move_to_end------------------------------------
615 // Move empty and uncommon blocks to the end.
616 void PhaseCFG::move_to_end(Block *b, uint i) {
617 int e = b->is_Empty();
618 if (e != Block::not_empty) {
619 if (e == Block::empty_with_goto) {
620 // Remove the goto, but leave the block.
621 b->_nodes.pop();
622 }
623 // Mark this block as a connector block, which will cause it to be
624 // ignored in certain functions such as non_connector_successor().
625 b->set_connector();
626 }
627 // Move the empty block to the end, and don't recheck.
628 _blocks.remove(i);
629 _blocks.push(b);
630 }
631
632 //---------------------------set_loop_alignment--------------------------------
633 // Set loop alignment for every block
634 void PhaseCFG::set_loop_alignment() {
635 uint last = _num_blocks;
636 assert( _blocks[0] == _broot, "" );
637
638 for (uint i = 1; i < last; i++ ) {
639 Block *b = _blocks[i];
640 if (b->head()->is_Loop()) {
641 b->set_loop_alignment(b);
642 }
643 }
644 }
645
646 //-----------------------------remove_empty------------------------------------
647 // Make empty basic blocks to be "connector" blocks, Move uncommon blocks
648 // to the end.
649 void PhaseCFG::remove_empty() {
650 // Move uncommon blocks to the end
651 uint last = _num_blocks;
652 assert( _blocks[0] == _broot, "" );
653
654 for (uint i = 1; i < last; i++) {
655 Block *b = _blocks[i];
656 if (b->is_connector()) break;
657
658 // Check for NeverBranch at block end. This needs to become a GOTO to the
659 // true target. NeverBranch are treated as a conditional branch that
660 // always goes the same direction for most of the optimizer and are used
661 // to give a fake exit path to infinite loops. At this late stage they
662 // need to turn into Goto's so that when you enter the infinite loop you
663 // indeed hang.
664 if( b->_nodes[b->end_idx()]->Opcode() == Op_NeverBranch )
665 convert_NeverBranch_to_Goto(b);
666
667 // Look for uncommon blocks and move to end.
668 if (!C->do_freq_based_layout()) {
669 if( b->is_uncommon(_bbs) ) {
670 move_to_end(b, i);
671 last--; // No longer check for being uncommon!
672 if( no_flip_branch(b) ) { // Fall-thru case must follow?
673 b = _blocks[i]; // Find the fall-thru block
674 move_to_end(b, i);
675 last--;
676 }
677 i--; // backup block counter post-increment
678 }
679 }
680 }
681
682 // Move empty blocks to the end
683 last = _num_blocks;
684 for (uint i = 1; i < last; i++) {
685 Block *b = _blocks[i];
686 if (b->is_Empty() != Block::not_empty) {
687 move_to_end(b, i);
688 last--;
689 i--;
690 }
691 } // End of for all blocks
692 }
693
694 //-----------------------------fixup_flow--------------------------------------
695 // Fix up the final control flow for basic blocks.
696 void PhaseCFG::fixup_flow() {
697 // Fixup final control flow for the blocks. Remove jump-to-next
698 // block. If neither arm of a IF follows the conditional branch, we
699 // have to add a second jump after the conditional. We place the
700 // TRUE branch target in succs[0] for both GOTOs and IFs.
701 for (uint i=0; i < _num_blocks; i++) {
702 Block *b = _blocks[i];
703 b->_pre_order = i; // turn pre-order into block-index
704
705 // Connector blocks need no further processing.
706 if (b->is_connector()) {
707 assert((i+1) == _num_blocks || _blocks[i+1]->is_connector(),
708 "All connector blocks should sink to the end");
709 continue;
710 }
711 assert(b->is_Empty() != Block::completely_empty,
712 "Empty blocks should be connectors");
713
714 Block *bnext = (i < _num_blocks-1) ? _blocks[i+1] : NULL;
715 Block *bs0 = b->non_connector_successor(0);
716
717 // Check for multi-way branches where I cannot negate the test to
718 // exchange the true and false targets.
719 if( no_flip_branch( b ) ) {
720 // Find fall through case - if must fall into its target
721 int branch_idx = b->_nodes.size() - b->_num_succs;
722 for (uint j2 = 0; j2 < b->_num_succs; j2++) {
723 const ProjNode* p = b->_nodes[branch_idx + j2]->as_Proj();
724 if (p->_con == 0) {
725 // successor j2 is fall through case
726 if (b->non_connector_successor(j2) != bnext) {
727 // but it is not the next block => insert a goto
728 insert_goto_at(i, j2);
729 }
730 // Put taken branch in slot 0
731 if( j2 == 0 && b->_num_succs == 2) {
732 // Flip targets in succs map
733 Block *tbs0 = b->_succs[0];
734 Block *tbs1 = b->_succs[1];
735 b->_succs.map( 0, tbs1 );
736 b->_succs.map( 1, tbs0 );
737 }
738 break;
739 }
740 }
741 // Remove all CatchProjs
742 for (uint j1 = 0; j1 < b->_num_succs; j1++) b->_nodes.pop();
743
744 } else if (b->_num_succs == 1) {
745 // Block ends in a Goto?
746 if (bnext == bs0) {
747 // We fall into next block; remove the Goto
748 b->_nodes.pop();
749 }
750
751 } else if( b->_num_succs == 2 ) { // Block ends in a If?
752 // Get opcode of 1st projection (matches _succs[0])
753 // Note: Since this basic block has 2 exits, the last 2 nodes must
754 // be projections (in any order), the 3rd last node must be
755 // the IfNode (we have excluded other 2-way exits such as
756 // CatchNodes already).
757 MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach();
758 ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj();
759 ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj();
760
761 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
762 assert(proj0->raw_out(0) == b->_succs[0]->head(), "Mismatch successor 0");
763 assert(proj1->raw_out(0) == b->_succs[1]->head(), "Mismatch successor 1");
764
765 Block *bs1 = b->non_connector_successor(1);
766
767 // Check for neither successor block following the current
768 // block ending in a conditional. If so, move one of the
769 // successors after the current one, provided that the
770 // successor was previously unscheduled, but moveable
771 // (i.e., all paths to it involve a branch).
772 if( !C->do_freq_based_layout() && bnext != bs0 && bnext != bs1 ) {
773 // Choose the more common successor based on the probability
774 // of the conditional branch.
775 Block *bx = bs0;
776 Block *by = bs1;
777
778 // _prob is the probability of taking the true path. Make
779 // p the probability of taking successor #1.
780 float p = iff->as_MachIf()->_prob;
781 if( proj0->Opcode() == Op_IfTrue ) {
782 p = 1.0 - p;
783 }
784
785 // Prefer successor #1 if p > 0.5
786 if (p > PROB_FAIR) {
787 bx = bs1;
788 by = bs0;
789 }
790
791 // Attempt the more common successor first
792 if (move_to_next(bx, i)) {
793 bnext = bx;
794 } else if (move_to_next(by, i)) {
795 bnext = by;
796 }
797 }
798
799 // Check for conditional branching the wrong way. Negate
800 // conditional, if needed, so it falls into the following block
801 // and branches to the not-following block.
802
803 // Check for the next block being in succs[0]. We are going to branch
804 // to succs[0], so we want the fall-thru case as the next block in
805 // succs[1].
806 if (bnext == bs0) {
807 // Fall-thru case in succs[0], so flip targets in succs map
808 Block *tbs0 = b->_succs[0];
809 Block *tbs1 = b->_succs[1];
810 b->_succs.map( 0, tbs1 );
811 b->_succs.map( 1, tbs0 );
812 // Flip projection for each target
813 { ProjNode *tmp = proj0; proj0 = proj1; proj1 = tmp; }
814
815 } else if( bnext != bs1 ) {
816 // Need a double-branch
817 // The existing conditional branch need not change.
818 // Add a unconditional branch to the false target.
819 // Alas, it must appear in its own block and adding a
820 // block this late in the game is complicated. Sigh.
821 insert_goto_at(i, 1);
822 }
823
824 // Make sure we TRUE branch to the target
825 if( proj0->Opcode() == Op_IfFalse ) {
826 iff->negate();
827 }
828
829 b->_nodes.pop(); // Remove IfFalse & IfTrue projections
830 b->_nodes.pop();
831
832 } else {
833 // Multi-exit block, e.g. a switch statement
834 // But we don't need to do anything here
835 }
836 } // End of for all blocks
837 }
838
839
840 //------------------------------dump-------------------------------------------
841 #ifndef PRODUCT
842 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const {
843 const Node *x = end->is_block_proj();
844 assert( x, "not a CFG" );
845
846 // Do not visit this block again
847 if( visited.test_set(x->_idx) ) return;
848
849 // Skip through this block
850 const Node *p = x;
851 do {
852 p = p->in(0); // Move control forward
853 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
854 } while( !p->is_block_start() );
855
856 // Recursively visit
857 for( uint i=1; i<p->req(); i++ )
858 _dump_cfg(p->in(i),visited);
859
860 // Dump the block
861 _bbs[p->_idx]->dump(&_bbs);
862 }
863
864 void PhaseCFG::dump( ) const {
865 tty->print("\n--- CFG --- %d BBs\n",_num_blocks);
866 if( _blocks.size() ) { // Did we do basic-block layout?
867 for( uint i=0; i<_num_blocks; i++ )
868 _blocks[i]->dump(&_bbs);
869 } else { // Else do it with a DFS
870 VectorSet visited(_bbs._arena);
871 _dump_cfg(_root,visited);
872 }
873 }
874
875 void PhaseCFG::dump_headers() {
876 for( uint i = 0; i < _num_blocks; i++ ) {
877 if( _blocks[i] == NULL ) continue;
878 _blocks[i]->dump_head(&_bbs);
879 }
880 }
881
882 void PhaseCFG::verify( ) const {
883 // Verify sane CFG
884 for( uint i = 0; i < _num_blocks; i++ ) {
885 Block *b = _blocks[i];
886 uint cnt = b->_nodes.size();
887 uint j;
888 for( j = 0; j < cnt; j++ ) {
889 Node *n = b->_nodes[j];
890 assert( _bbs[n->_idx] == b, "" );
891 if( j >= 1 && n->is_Mach() &&
892 n->as_Mach()->ideal_Opcode() == Op_CreateEx ) {
893 assert( j == 1 || b->_nodes[j-1]->is_Phi(),
894 "CreateEx must be first instruction in block" );
895 }
896 for( uint k = 0; k < n->req(); k++ ) {
897 Node *use = n->in(k);
898 if( use && use != n ) {
899 assert( _bbs[use->_idx] || use->is_Con(),
900 "must have block; constants for debug info ok" );
901 }
902 }
903 }
904
905 j = b->end_idx();
906 Node *bp = (Node*)b->_nodes[b->_nodes.size()-1]->is_block_proj();
907 assert( bp, "last instruction must be a block proj" );
908 assert( bp == b->_nodes[j], "wrong number of successors for this block" );
909 if( bp->is_Catch() ) {
910 while( b->_nodes[--j]->Opcode() == Op_MachProj ) ;
911 assert( b->_nodes[j]->is_Call(), "CatchProj must follow call" );
912 }
913 else if( bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If ) {
914 assert( b->_num_succs == 2, "Conditional branch must have two targets");
915 }
916 }
917 }
918 #endif
919
920 //=============================================================================
921 //------------------------------UnionFind--------------------------------------
922 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) {
923 Copy::zero_to_bytes( _indices, sizeof(uint)*max );
924 }
925
926 void UnionFind::extend( uint from_idx, uint to_idx ) {
927 _nesting.check();
928 if( from_idx >= _max ) {
929 uint size = 16;
930 while( size <= from_idx ) size <<=1;
931 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size );
932 _max = size;
933 }
934 while( _cnt <= from_idx ) _indices[_cnt++] = 0;
935 _indices[from_idx] = to_idx;
936 }
937
938 void UnionFind::reset( uint max ) {
939 assert( max <= max_uint, "Must fit within uint" );
940 // Force the Union-Find mapping to be at least this large
941 extend(max,0);
942 // Initialize to be the ID mapping.
943 for( uint i=0; i<max; i++ ) map(i,i);
944 }
945
946 //------------------------------Find_compress----------------------------------
947 // Straight out of Tarjan's union-find algorithm
948 uint UnionFind::Find_compress( uint idx ) {
949 uint cur = idx;
950 uint next = lookup(cur);
951 while( next != cur ) { // Scan chain of equivalences
952 assert( next < cur, "always union smaller" );
953 cur = next; // until find a fixed-point
954 next = lookup(cur);
955 }
956 // Core of union-find algorithm: update chain of
957 // equivalences to be equal to the root.
958 while( idx != next ) {
959 uint tmp = lookup(idx);
960 map(idx, next);
961 idx = tmp;
962 }
963 return idx;
964 }
965
966 //------------------------------Find_const-------------------------------------
967 // Like Find above, but no path compress, so bad asymptotic behavior
968 uint UnionFind::Find_const( uint idx ) const {
969 if( idx == 0 ) return idx; // Ignore the zero idx
970 // Off the end? This can happen during debugging dumps
971 // when data structures have not finished being updated.
972 if( idx >= _max ) return idx;
973 uint next = lookup(idx);
974 while( next != idx ) { // Scan chain of equivalences
975 idx = next; // until find a fixed-point
976 next = lookup(idx);
977 }
978 return next;
979 }
980
981 //------------------------------Union------------------------------------------
982 // union 2 sets together.
983 void UnionFind::Union( uint idx1, uint idx2 ) {
984 uint src = Find(idx1);
985 uint dst = Find(idx2);
986 assert( src, "" );
987 assert( dst, "" );
988 assert( src < _max, "oob" );
989 assert( dst < _max, "oob" );
990 assert( src < dst, "always union smaller" );
991 map(dst,src);
992 }
993
994 #ifndef PRODUCT
995 static void edge_dump(GrowableArray<CFGEdge *> *edges) {
996 tty->print_cr("---- Edges ----");
997 for (int i = 0; i < edges->length(); i++) {
998 CFGEdge *e = edges->at(i);
999 if (e != NULL) {
1000 edges->at(i)->dump();
1001 }
1002 }
1003 }
1004
1005 static void trace_dump(Trace *traces[], int count) {
1006 tty->print_cr("---- Traces ----");
1007 for (int i = 0; i < count; i++) {
1008 Trace *tr = traces[i];
1009 if (tr != NULL) {
1010 tr->dump();
1011 }
1012 }
1013 }
1014
1015 void Trace::dump( ) const {
1016 tty->print_cr("Trace (freq %f)", first_block()->_freq);
1017 for (Block *b = first_block(); b != NULL; b = next(b)) {
1018 tty->print(" B%d", b->_pre_order);
1019 if (b->head()->is_Loop()) {
1020 tty->print(" (L%d)", b->compute_loop_alignment());
1021 }
1022 if (b->has_loop_alignment()) {
1023 tty->print(" (T%d)", b->code_alignment());
1024 }
1025 }
1026 tty->cr();
1027 }
1028
1029 void CFGEdge::dump( ) const {
1030 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ",
1031 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct);
1032 switch(state()) {
1033 case connected:
1034 tty->print("connected");
1035 break;
1036 case open:
1037 tty->print("open");
1038 break;
1039 case interior:
1040 tty->print("interior");
1041 break;
1042 }
1043 if (infrequent()) {
1044 tty->print(" infrequent");
1045 }
1046 tty->cr();
1047 }
1048 #endif
1049
1050 //=============================================================================
1051
1052 //------------------------------edge_order-------------------------------------
1053 // Comparison function for edges
1054 static int edge_order(CFGEdge **e0, CFGEdge **e1) {
1055 float freq0 = (*e0)->freq();
1056 float freq1 = (*e1)->freq();
1057 if (freq0 != freq1) {
1058 return freq0 > freq1 ? -1 : 1;
1059 }
1060
1061 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo;
1062 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo;
1063
1064 return dist1 - dist0;
1065 }
1066
1067 //------------------------------trace_frequency_order--------------------------
1068 // Comparison function for edges
1069 static int trace_frequency_order(const void *p0, const void *p1) {
1070 Trace *tr0 = *(Trace **) p0;
1071 Trace *tr1 = *(Trace **) p1;
1072 Block *b0 = tr0->first_block();
1073 Block *b1 = tr1->first_block();
1074
1075 // The trace of connector blocks goes at the end;
1076 // we only expect one such trace
1077 if (b0->is_connector() != b1->is_connector()) {
1078 return b1->is_connector() ? -1 : 1;
1079 }
1080
1081 // Pull more frequently executed blocks to the beginning
1082 float freq0 = b0->_freq;
1083 float freq1 = b1->_freq;
1084 if (freq0 != freq1) {
1085 return freq0 > freq1 ? -1 : 1;
1086 }
1087
1088 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo;
1089
1090 return diff;
1091 }
1092
1093 //------------------------------find_edges-------------------------------------
1094 // Find edges of interest, i.e, those which can fall through. Presumes that
1095 // edges which don't fall through are of low frequency and can be generally
1096 // ignored. Initialize the list of traces.
1097 void PhaseBlockLayout::find_edges()
1098 {
1099 // Walk the blocks, creating edges and Traces
1100 uint i;
1101 Trace *tr = NULL;
1102 for (i = 0; i < _cfg._num_blocks; i++) {
1103 Block *b = _cfg._blocks[i];
1104 tr = new Trace(b, next, prev);
1105 traces[tr->id()] = tr;
1106
1107 // All connector blocks should be at the end of the list
1108 if (b->is_connector()) break;
1109
1110 // If this block and the next one have a one-to-one successor
1111 // predecessor relationship, simply append the next block
1112 int nfallthru = b->num_fall_throughs();
1113 while (nfallthru == 1 &&
1114 b->succ_fall_through(0)) {
1115 Block *n = b->_succs[0];
1116
1117 // Skip over single-entry connector blocks, we don't want to
1118 // add them to the trace.
1119 while (n->is_connector() && n->num_preds() == 1) {
1120 n = n->_succs[0];
1121 }
1122
1123 // We see a merge point, so stop search for the next block
1124 if (n->num_preds() != 1) break;
1125
1126 i++;
1127 assert(n = _cfg._blocks[i], "expecting next block");
1128 tr->append(n);
1129 uf->map(n->_pre_order, tr->id());
1130 traces[n->_pre_order] = NULL;
1131 nfallthru = b->num_fall_throughs();
1132 b = n;
1133 }
1134
1135 if (nfallthru > 0) {
1136 // Create a CFGEdge for each outgoing
1137 // edge that could be a fall-through.
1138 for (uint j = 0; j < b->_num_succs; j++ ) {
1139 if (b->succ_fall_through(j)) {
1140 Block *target = b->non_connector_successor(j);
1141 float freq = b->_freq * b->succ_prob(j);
1142 int from_pct = (int) ((100 * freq) / b->_freq);
1143 int to_pct = (int) ((100 * freq) / target->_freq);
1144 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct));
1145 }
1146 }
1147 }
1148 }
1149
1150 // Group connector blocks into one trace
1151 for (i++; i < _cfg._num_blocks; i++) {
1152 Block *b = _cfg._blocks[i];
1153 assert(b->is_connector(), "connector blocks at the end");
1154 tr->append(b);
1155 uf->map(b->_pre_order, tr->id());
1156 traces[b->_pre_order] = NULL;
1157 }
1158 }
1159
1160 //------------------------------union_traces----------------------------------
1161 // Union two traces together in uf, and null out the trace in the list
1162 void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace)
1163 {
1164 uint old_id = old_trace->id();
1165 uint updated_id = updated_trace->id();
1166
1167 uint lo_id = updated_id;
1168 uint hi_id = old_id;
1169
1170 // If from is greater than to, swap values to meet
1171 // UnionFind guarantee.
1172 if (updated_id > old_id) {
1173 lo_id = old_id;
1174 hi_id = updated_id;
1175
1176 // Fix up the trace ids
1177 traces[lo_id] = traces[updated_id];
1178 updated_trace->set_id(lo_id);
1179 }
1180
1181 // Union the lower with the higher and remove the pointer
1182 // to the higher.
1183 uf->Union(lo_id, hi_id);
1184 traces[hi_id] = NULL;
1185 }
1186
1187 //------------------------------grow_traces-------------------------------------
1188 // Append traces together via the most frequently executed edges
1189 void PhaseBlockLayout::grow_traces()
1190 {
1191 // Order the edges, and drive the growth of Traces via the most
1192 // frequently executed edges.
1193 edges->sort(edge_order);
1194 for (int i = 0; i < edges->length(); i++) {
1195 CFGEdge *e = edges->at(i);
1196
1197 if (e->state() != CFGEdge::open) continue;
1198
1199 Block *src_block = e->from();
1200 Block *targ_block = e->to();
1201
1202 // Don't grow traces along backedges?
1203 if (!BlockLayoutRotateLoops) {
1204 if (targ_block->_rpo <= src_block->_rpo) {
1205 targ_block->set_loop_alignment(targ_block);
1206 continue;
1207 }
1208 }
1209
1210 Trace *src_trace = trace(src_block);
1211 Trace *targ_trace = trace(targ_block);
1212
1213 // If the edge in question can join two traces at their ends,
1214 // append one trace to the other.
1215 if (src_trace->last_block() == src_block) {
1216 if (src_trace == targ_trace) {
1217 e->set_state(CFGEdge::interior);
1218 if (targ_trace->backedge(e)) {
1219 // Reset i to catch any newly eligible edge
1220 // (Or we could remember the first "open" edge, and reset there)
1221 i = 0;
1222 }
1223 } else if (targ_trace->first_block() == targ_block) {
1224 e->set_state(CFGEdge::connected);
1225 src_trace->append(targ_trace);
1226 union_traces(src_trace, targ_trace);
1227 }
1228 }
1229 }
1230 }
1231
1232 //------------------------------merge_traces-----------------------------------
1233 // Embed one trace into another, if the fork or join points are sufficiently
1234 // balanced.
1235 void PhaseBlockLayout::merge_traces(bool fall_thru_only)
1236 {
1237 // Walk the edge list a another time, looking at unprocessed edges.
1238 // Fold in diamonds
1239 for (int i = 0; i < edges->length(); i++) {
1240 CFGEdge *e = edges->at(i);
1241
1242 if (e->state() != CFGEdge::open) continue;
1243 if (fall_thru_only) {
1244 if (e->infrequent()) continue;
1245 }
1246
1247 Block *src_block = e->from();
1248 Trace *src_trace = trace(src_block);
1249 bool src_at_tail = src_trace->last_block() == src_block;
1250
1251 Block *targ_block = e->to();
1252 Trace *targ_trace = trace(targ_block);
1253 bool targ_at_start = targ_trace->first_block() == targ_block;
1254
1255 if (src_trace == targ_trace) {
1256 // This may be a loop, but we can't do much about it.
1257 e->set_state(CFGEdge::interior);
1258 continue;
1259 }
1260
1261 if (fall_thru_only) {
1262 // If the edge links the middle of two traces, we can't do anything.
1263 // Mark the edge and continue.
1264 if (!src_at_tail & !targ_at_start) {
1265 continue;
1266 }
1267
1268 // Don't grow traces along backedges?
1269 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) {
1270 continue;
1271 }
1272
1273 // If both ends of the edge are available, why didn't we handle it earlier?
1274 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier.");
1275
1276 if (targ_at_start) {
1277 // Insert the "targ" trace in the "src" trace if the insertion point
1278 // is a two way branch.
1279 // Better profitability check possible, but may not be worth it.
1280 // Someday, see if the this "fork" has an associated "join";
1281 // then make a policy on merging this trace at the fork or join.
1282 // For example, other things being equal, it may be better to place this
1283 // trace at the join point if the "src" trace ends in a two-way, but
1284 // the insertion point is one-way.
1285 assert(src_block->num_fall_throughs() == 2, "unexpected diamond");
1286 e->set_state(CFGEdge::connected);
1287 src_trace->insert_after(src_block, targ_trace);
1288 union_traces(src_trace, targ_trace);
1289 } else if (src_at_tail) {
1290 if (src_trace != trace(_cfg._broot)) {
1291 e->set_state(CFGEdge::connected);
1292 targ_trace->insert_before(targ_block, src_trace);
1293 union_traces(targ_trace, src_trace);
1294 }
1295 }
1296 } else if (e->state() == CFGEdge::open) {
1297 // Append traces, even without a fall-thru connection.
1298 // But leave root entry at the begining of the block list.
1299 if (targ_trace != trace(_cfg._broot)) {
1300 e->set_state(CFGEdge::connected);
1301 src_trace->append(targ_trace);
1302 union_traces(src_trace, targ_trace);
1303 }
1304 }
1305 }
1306 }
1307
1308 //----------------------------reorder_traces-----------------------------------
1309 // Order the sequence of the traces in some desirable way, and fixup the
1310 // jumps at the end of each block.
1311 void PhaseBlockLayout::reorder_traces(int count)
1312 {
1313 ResourceArea *area = Thread::current()->resource_area();
1314 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count);
1315 Block_List worklist;
1316 int new_count = 0;
1317
1318 // Compact the traces.
1319 for (int i = 0; i < count; i++) {
1320 Trace *tr = traces[i];
1321 if (tr != NULL) {
1322 new_traces[new_count++] = tr;
1323 }
1324 }
1325
1326 // The entry block should be first on the new trace list.
1327 Trace *tr = trace(_cfg._broot);
1328 assert(tr == new_traces[0], "entry trace misplaced");
1329
1330 // Sort the new trace list by frequency
1331 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order);
1332
1333 // Patch up the successor blocks
1334 _cfg._blocks.reset();
1335 _cfg._num_blocks = 0;
1336 for (int i = 0; i < new_count; i++) {
1337 Trace *tr = new_traces[i];
1338 if (tr != NULL) {
1339 tr->fixup_blocks(_cfg);
1340 }
1341 }
1342 }
1343
1344 //------------------------------PhaseBlockLayout-------------------------------
1345 // Order basic blocks based on frequency
1346 PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg) :
1347 Phase(BlockLayout),
1348 _cfg(cfg)
1349 {
1350 ResourceMark rm;
1351 ResourceArea *area = Thread::current()->resource_area();
1352
1353 // List of traces
1354 int size = _cfg._num_blocks + 1;
1355 traces = NEW_ARENA_ARRAY(area, Trace *, size);
1356 memset(traces, 0, size*sizeof(Trace*));
1357 next = NEW_ARENA_ARRAY(area, Block *, size);
1358 memset(next, 0, size*sizeof(Block *));
1359 prev = NEW_ARENA_ARRAY(area, Block *, size);
1360 memset(prev , 0, size*sizeof(Block *));
1361
1362 // List of edges
1363 edges = new GrowableArray<CFGEdge*>;
1364
1365 // Mapping block index --> block_trace
1366 uf = new UnionFind(size);
1367 uf->reset(size);
1368
1369 // Find edges and create traces.
1370 find_edges();
1371
1372 // Grow traces at their ends via most frequent edges.
1373 grow_traces();
1374
1375 // Merge one trace into another, but only at fall-through points.
1376 // This may make diamonds and other related shapes in a trace.
1377 merge_traces(true);
1378
1379 // Run merge again, allowing two traces to be catenated, even if
1380 // one does not fall through into the other. This appends loosely
1381 // related traces to be near each other.
1382 merge_traces(false);
1383
1384 // Re-order all the remaining traces by frequency
1385 reorder_traces(size);
1386
1387 assert(_cfg._num_blocks >= (uint) (size - 1), "number of blocks can not shrink");
1388 }
1389
1390
1391 //------------------------------backedge---------------------------------------
1392 // Edge e completes a loop in a trace. If the target block is head of the
1393 // loop, rotate the loop block so that the loop ends in a conditional branch.
1394 bool Trace::backedge(CFGEdge *e) {
1395 bool loop_rotated = false;
1396 Block *src_block = e->from();
1397 Block *targ_block = e->to();
1398
1399 assert(last_block() == src_block, "loop discovery at back branch");
1400 if (first_block() == targ_block) {
1401 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) {
1402 // Find the last block in the trace that has a conditional
1403 // branch.
1404 Block *b;
1405 for (b = last_block(); b != NULL; b = prev(b)) {
1406 if (b->num_fall_throughs() == 2) {
1407 break;
1408 }
1409 }
1410
1411 if (b != last_block() && b != NULL) {
1412 loop_rotated = true;
1413
1414 // Rotate the loop by doing two-part linked-list surgery.
1415 append(first_block());
1416 break_loop_after(b);
1417 }
1418 }
1419
1420 // Backbranch to the top of a trace
1421 // Scroll foward through the trace from the targ_block. If we find
1422 // a loop head before another loop top, use the the loop head alignment.
1423 for (Block *b = targ_block; b != NULL; b = next(b)) {
1424 if (b->has_loop_alignment()) {
1425 break;
1426 }
1427 if (b->head()->is_Loop()) {
1428 targ_block = b;
1429 break;
1430 }
1431 }
1432
1433 first_block()->set_loop_alignment(targ_block);
1434
1435 } else {
1436 // Backbranch into the middle of a trace
1437 targ_block->set_loop_alignment(targ_block);
1438 }
1439
1440 return loop_rotated;
1441 }
1442
1443 //------------------------------fixup_blocks-----------------------------------
1444 // push blocks onto the CFG list
1445 // ensure that blocks have the correct two-way branch sense
1446 void Trace::fixup_blocks(PhaseCFG &cfg) {
1447 Block *last = last_block();
1448 for (Block *b = first_block(); b != NULL; b = next(b)) {
1449 cfg._blocks.push(b);
1450 cfg._num_blocks++;
1451 if (!b->is_connector()) {
1452 int nfallthru = b->num_fall_throughs();
1453 if (b != last) {
1454 if (nfallthru == 2) {
1455 // Ensure that the sense of the branch is correct
1456 Block *bnext = next(b);
1457 Block *bs0 = b->non_connector_successor(0);
1458
1459 MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach();
1460 ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj();
1461 ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj();
1462
1463 if (bnext == bs0) {
1464 // Fall-thru case in succs[0], should be in succs[1]
1465
1466 // Flip targets in _succs map
1467 Block *tbs0 = b->_succs[0];
1468 Block *tbs1 = b->_succs[1];
1469 b->_succs.map( 0, tbs1 );
1470 b->_succs.map( 1, tbs0 );
1471
1472 // Flip projections to match targets
1473 b->_nodes.map(b->_nodes.size()-2, proj1);
1474 b->_nodes.map(b->_nodes.size()-1, proj0);
1475 }
1476 }
1477 }
1478 }
1479 }
1480 }