1 /*
2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "libadt/vectset.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "compiler/compilerDirectives.hpp"
29 #include "opto/block.hpp"
30 #include "opto/cfgnode.hpp"
31 #include "opto/chaitin.hpp"
32 #include "opto/loopnode.hpp"
33 #include "opto/machnode.hpp"
34 #include "opto/matcher.hpp"
35 #include "opto/opcodes.hpp"
36 #include "opto/rootnode.hpp"
37 #include "utilities/copy.hpp"
38
39 void Block_Array::grow( uint i ) {
40 assert(i >= Max(), "must be an overflow");
41 debug_only(_limit = i+1);
42 if( i < _size ) return;
43 if( !_size ) {
44 _size = 1;
45 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) );
46 _blocks[0] = NULL;
47 }
48 uint old = _size;
49 while( i >= _size ) _size <<= 1; // Double to fit
50 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*));
51 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) );
52 }
53
54 void Block_List::remove(uint i) {
55 assert(i < _cnt, "index out of bounds");
56 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*)));
57 pop(); // shrink list by one block
58 }
59
60 void Block_List::insert(uint i, Block *b) {
61 push(b); // grow list by one block
62 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*)));
63 _blocks[i] = b;
64 }
65
66 #ifndef PRODUCT
67 void Block_List::print() {
68 for (uint i=0; i < size(); i++) {
69 tty->print("B%d ", _blocks[i]->_pre_order);
70 }
71 tty->print("size = %d\n", size());
72 }
73 #endif
74
75 uint Block::code_alignment() {
76 // Check for Root block
77 if (_pre_order == 0) return CodeEntryAlignment;
78 // Check for Start block
79 if (_pre_order == 1) return InteriorEntryAlignment;
80 // Check for loop alignment
81 if (has_loop_alignment()) return loop_alignment();
82
83 return relocInfo::addr_unit(); // no particular alignment
84 }
85
86 uint Block::compute_loop_alignment() {
87 Node *h = head();
88 int unit_sz = relocInfo::addr_unit();
89 if (h->is_Loop() && h->as_Loop()->is_inner_loop()) {
90 // Pre- and post-loops have low trip count so do not bother with
91 // NOPs for align loop head. The constants are hidden from tuning
92 // but only because my "divide by 4" heuristic surely gets nearly
93 // all possible gain (a "do not align at all" heuristic has a
94 // chance of getting a really tiny gain).
95 if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() ||
96 h->as_CountedLoop()->is_post_loop())) {
97 return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz;
98 }
99 // Loops with low backedge frequency should not be aligned.
100 Node *n = h->in(LoopNode::LoopBackControl)->in(0);
101 if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) {
102 return unit_sz; // Loop does not loop, more often than not!
103 }
104 return OptoLoopAlignment; // Otherwise align loop head
105 }
106
107 return unit_sz; // no particular alignment
108 }
109
110 // Compute the size of first 'inst_cnt' instructions in this block.
111 // Return the number of instructions left to compute if the block has
112 // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size
113 // exceeds OptoLoopAlignment.
114 uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt,
115 PhaseRegAlloc* ra) {
116 uint last_inst = number_of_nodes();
117 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) {
118 uint inst_size = get_node(j)->size(ra);
119 if( inst_size > 0 ) {
120 inst_cnt--;
121 uint sz = sum_size + inst_size;
122 if( sz <= (uint)OptoLoopAlignment ) {
123 // Compute size of instructions which fit into fetch buffer only
124 // since all inst_cnt instructions will not fit even if we align them.
125 sum_size = sz;
126 } else {
127 return 0;
128 }
129 }
130 }
131 return inst_cnt;
132 }
133
134 uint Block::find_node( const Node *n ) const {
135 for( uint i = 0; i < number_of_nodes(); i++ ) {
136 if( get_node(i) == n )
137 return i;
138 }
139 ShouldNotReachHere();
140 return 0;
141 }
142
143 // Find and remove n from block list
144 void Block::find_remove( const Node *n ) {
145 remove_node(find_node(n));
146 }
147
148 bool Block::contains(const Node *n) const {
149 return _nodes.contains(n);
150 }
151
152 // Return empty status of a block. Empty blocks contain only the head, other
153 // ideal nodes, and an optional trailing goto.
154 int Block::is_Empty() const {
155
156 // Root or start block is not considered empty
157 if (head()->is_Root() || head()->is_Start()) {
158 return not_empty;
159 }
160
161 int success_result = completely_empty;
162 int end_idx = number_of_nodes() - 1;
163
164 // Check for ending goto
165 if ((end_idx > 0) && (get_node(end_idx)->is_MachGoto())) {
166 success_result = empty_with_goto;
167 end_idx--;
168 }
169
170 // Unreachable blocks are considered empty
171 if (num_preds() <= 1) {
172 return success_result;
173 }
174
175 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes
176 // turn directly into code, because only MachNodes have non-trivial
177 // emit() functions.
178 while ((end_idx > 0) && !get_node(end_idx)->is_Mach()) {
179 end_idx--;
180 }
181
182 // No room for any interesting instructions?
183 if (end_idx == 0) {
184 return success_result;
185 }
186
187 return not_empty;
188 }
189
190 // Return true if the block's code implies that it is likely to be
191 // executed infrequently. Check to see if the block ends in a Halt or
192 // a low probability call.
193 bool Block::has_uncommon_code() const {
194 Node* en = end();
195
196 if (en->is_MachGoto())
197 en = en->in(0);
198 if (en->is_Catch())
199 en = en->in(0);
200 if (en->is_MachProj() && en->in(0)->is_MachCall()) {
201 MachCallNode* call = en->in(0)->as_MachCall();
202 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) {
203 // This is true for slow-path stubs like new_{instance,array},
204 // slow_arraycopy, complete_monitor_locking, uncommon_trap.
205 // The magic number corresponds to the probability of an uncommon_trap,
206 // even though it is a count not a probability.
207 return true;
208 }
209 }
210
211 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode();
212 return op == Op_Halt;
213 }
214
215 // True if block is low enough frequency or guarded by a test which
216 // mostly does not go here.
217 bool PhaseCFG::is_uncommon(const Block* block) {
218 // Initial blocks must never be moved, so are never uncommon.
219 if (block->head()->is_Root() || block->head()->is_Start()) return false;
220
221 // Check for way-low freq
222 if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) return true;
223
224 // Look for code shape indicating uncommon_trap or slow path
225 if (block->has_uncommon_code()) return true;
226
227 const float epsilon = 0.05f;
228 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon);
229 uint uncommon_preds = 0;
230 uint freq_preds = 0;
231 uint uncommon_for_freq_preds = 0;
232
233 for( uint i=1; i< block->num_preds(); i++ ) {
234 Block* guard = get_block_for_node(block->pred(i));
235 // Check to see if this block follows its guard 1 time out of 10000
236 // or less.
237 //
238 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which
239 // we intend to be "uncommon", such as slow-path TLE allocation,
240 // predicted call failure, and uncommon trap triggers.
241 //
242 // Use an epsilon value of 5% to allow for variability in frequency
243 // predictions and floating point calculations. The net effect is
244 // that guard_factor is set to 9500.
245 //
246 // Ignore low-frequency blocks.
247 // The next check is (guard->_freq < 1.e-5 * 9500.).
248 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) {
249 uncommon_preds++;
250 } else {
251 freq_preds++;
252 if(block->_freq < guard->_freq * guard_factor ) {
253 uncommon_for_freq_preds++;
254 }
255 }
256 }
257 if( block->num_preds() > 1 &&
258 // The block is uncommon if all preds are uncommon or
259 (uncommon_preds == (block->num_preds()-1) ||
260 // it is uncommon for all frequent preds.
261 uncommon_for_freq_preds == freq_preds) ) {
262 return true;
263 }
264 return false;
265 }
266
267 #ifndef PRODUCT
268 void Block::dump_bidx(const Block* orig, outputStream* st) const {
269 if (_pre_order) st->print("B%d",_pre_order);
270 else st->print("N%d", head()->_idx);
271
272 if (Verbose && orig != this) {
273 // Dump the original block's idx
274 st->print(" (");
275 orig->dump_bidx(orig, st);
276 st->print(")");
277 }
278 }
279
280 void Block::dump_pred(const PhaseCFG* cfg, Block* orig, outputStream* st) const {
281 if (is_connector()) {
282 for (uint i=1; i<num_preds(); i++) {
283 Block *p = cfg->get_block_for_node(pred(i));
284 p->dump_pred(cfg, orig, st);
285 }
286 } else {
287 dump_bidx(orig, st);
288 st->print(" ");
289 }
290 }
291
292 void Block::dump_head(const PhaseCFG* cfg, outputStream* st) const {
293 // Print the basic block
294 dump_bidx(this, st);
295 st->print(": #\t");
296
297 // Print the incoming CFG edges and the outgoing CFG edges
298 for( uint i=0; i<_num_succs; i++ ) {
299 non_connector_successor(i)->dump_bidx(_succs[i], st);
300 st->print(" ");
301 }
302 st->print("<- ");
303 if( head()->is_block_start() ) {
304 for (uint i=1; i<num_preds(); i++) {
305 Node *s = pred(i);
306 if (cfg != NULL) {
307 Block *p = cfg->get_block_for_node(s);
308 p->dump_pred(cfg, p, st);
309 } else {
310 while (!s->is_block_start())
311 s = s->in(0);
312 st->print("N%d ", s->_idx );
313 }
314 }
315 } else {
316 st->print("BLOCK HEAD IS JUNK ");
317 }
318
319 // Print loop, if any
320 const Block *bhead = this; // Head of self-loop
321 Node *bh = bhead->head();
322
323 if ((cfg != NULL) && bh->is_Loop() && !head()->is_Root()) {
324 LoopNode *loop = bh->as_Loop();
325 const Block *bx = cfg->get_block_for_node(loop->in(LoopNode::LoopBackControl));
326 while (bx->is_connector()) {
327 bx = cfg->get_block_for_node(bx->pred(1));
328 }
329 st->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order);
330 // Dump any loop-specific bits, especially for CountedLoops.
331 loop->dump_spec(st);
332 } else if (has_loop_alignment()) {
333 st->print(" top-of-loop");
334 }
335 st->print(" Freq: %g",_freq);
336 if( Verbose || WizardMode ) {
337 st->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth);
338 st->print(" RegPressure: %d",_reg_pressure);
339 st->print(" IHRP Index: %d",_ihrp_index);
340 st->print(" FRegPressure: %d",_freg_pressure);
341 st->print(" FHRP Index: %d",_fhrp_index);
342 }
343 st->cr();
344 }
345
346 void Block::dump() const {
347 dump(NULL);
348 }
349
350 void Block::dump(const PhaseCFG* cfg) const {
351 dump_head(cfg);
352 for (uint i=0; i< number_of_nodes(); i++) {
353 get_node(i)->dump();
354 }
355 tty->print("\n");
356 }
357 #endif
358
359 PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher)
360 : Phase(CFG)
361 , _block_arena(arena)
362 , _regalloc(NULL)
363 , _scheduling_for_pressure(false)
364 , _root(root)
365 , _matcher(matcher)
366 , _node_to_block_mapping(arena)
367 , _node_latency(NULL)
368 #ifndef PRODUCT
369 , _trace_opto_pipelining(C->directive()->TraceOptoPipeliningOption)
370 #endif
371 #ifdef ASSERT
372 , _raw_oops(arena)
373 #endif
374 {
375 ResourceMark rm;
376 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode,
377 // then Match it into a machine-specific Node. Then clone the machine
378 // Node on demand.
379 Node *x = new GotoNode(NULL);
380 x->init_req(0, x);
381 _goto = matcher.match_tree(x);
382 assert(_goto != NULL, "");
383 _goto->set_req(0,_goto);
384
385 // Build the CFG in Reverse Post Order
386 _number_of_blocks = build_cfg();
387 _root_block = get_block_for_node(_root);
388 }
389
390 // Build a proper looking CFG. Make every block begin with either a StartNode
391 // or a RegionNode. Make every block end with either a Goto, If or Return.
392 // The RootNode both starts and ends it's own block. Do this with a recursive
393 // backwards walk over the control edges.
394 uint PhaseCFG::build_cfg() {
395 Arena *a = Thread::current()->resource_area();
396 VectorSet visited(a);
397
398 // Allocate stack with enough space to avoid frequent realloc
399 Node_Stack nstack(a, C->live_nodes() >> 1);
400 nstack.push(_root, 0);
401 uint sum = 0; // Counter for blocks
402
403 while (nstack.is_nonempty()) {
404 // node and in's index from stack's top
405 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack
406 // only nodes which point to the start of basic block (see below).
407 Node *np = nstack.node();
408 // idx > 0, except for the first node (_root) pushed on stack
409 // at the beginning when idx == 0.
410 // We will use the condition (idx == 0) later to end the build.
411 uint idx = nstack.index();
412 Node *proj = np->in(idx);
413 const Node *x = proj->is_block_proj();
414 // Does the block end with a proper block-ending Node? One of Return,
415 // If or Goto? (This check should be done for visited nodes also).
416 if (x == NULL) { // Does not end right...
417 Node *g = _goto->clone(); // Force it to end in a Goto
418 g->set_req(0, proj);
419 np->set_req(idx, g);
420 x = proj = g;
421 }
422 if (!visited.test_set(x->_idx)) { // Visit this block once
423 // Skip any control-pinned middle'in stuff
424 Node *p = proj;
425 do {
426 proj = p; // Update pointer to last Control
427 p = p->in(0); // Move control forward
428 } while( !p->is_block_proj() &&
429 !p->is_block_start() );
430 // Make the block begin with one of Region or StartNode.
431 if( !p->is_block_start() ) {
432 RegionNode *r = new RegionNode( 2 );
433 r->init_req(1, p); // Insert RegionNode in the way
434 proj->set_req(0, r); // Insert RegionNode in the way
435 p = r;
436 }
437 // 'p' now points to the start of this basic block
438
439 // Put self in array of basic blocks
440 Block *bb = new (_block_arena) Block(_block_arena, p);
441 map_node_to_block(p, bb);
442 map_node_to_block(x, bb);
443 if( x != p ) { // Only for root is x == p
444 bb->push_node((Node*)x);
445 }
446 // Now handle predecessors
447 ++sum; // Count 1 for self block
448 uint cnt = bb->num_preds();
449 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors
450 Node *prevproj = p->in(i); // Get prior input
451 assert( !prevproj->is_Con(), "dead input not removed" );
452 // Check to see if p->in(i) is a "control-dependent" CFG edge -
453 // i.e., it splits at the source (via an IF or SWITCH) and merges
454 // at the destination (via a many-input Region).
455 // This breaks critical edges. The RegionNode to start the block
456 // will be added when <p,i> is pulled off the node stack
457 if ( cnt > 2 ) { // Merging many things?
458 assert( prevproj== bb->pred(i),"");
459 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge?
460 // Force a block on the control-dependent edge
461 Node *g = _goto->clone(); // Force it to end in a Goto
462 g->set_req(0,prevproj);
463 p->set_req(i,g);
464 }
465 }
466 nstack.push(p, i); // 'p' is RegionNode or StartNode
467 }
468 } else { // Post-processing visited nodes
469 nstack.pop(); // remove node from stack
470 // Check if it the fist node pushed on stack at the beginning.
471 if (idx == 0) break; // end of the build
472 // Find predecessor basic block
473 Block *pb = get_block_for_node(x);
474 // Insert into nodes array, if not already there
475 if (!has_block(proj)) {
476 assert( x != proj, "" );
477 // Map basic block of projection
478 map_node_to_block(proj, pb);
479 pb->push_node(proj);
480 }
481 // Insert self as a child of my predecessor block
482 pb->_succs.map(pb->_num_succs++, get_block_for_node(np));
483 assert( pb->get_node(pb->number_of_nodes() - pb->_num_succs)->is_block_proj(),
484 "too many control users, not a CFG?" );
485 }
486 }
487 // Return number of basic blocks for all children and self
488 return sum;
489 }
490
491 // Inserts a goto & corresponding basic block between
492 // block[block_no] and its succ_no'th successor block
493 void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) {
494 // get block with block_no
495 assert(block_no < number_of_blocks(), "illegal block number");
496 Block* in = get_block(block_no);
497 // get successor block succ_no
498 assert(succ_no < in->_num_succs, "illegal successor number");
499 Block* out = in->_succs[succ_no];
500 // Compute frequency of the new block. Do this before inserting
501 // new block in case succ_prob() needs to infer the probability from
502 // surrounding blocks.
503 float freq = in->_freq * in->succ_prob(succ_no);
504 // get ProjNode corresponding to the succ_no'th successor of the in block
505 ProjNode* proj = in->get_node(in->number_of_nodes() - in->_num_succs + succ_no)->as_Proj();
506 // create region for basic block
507 RegionNode* region = new RegionNode(2);
508 region->init_req(1, proj);
509 // setup corresponding basic block
510 Block* block = new (_block_arena) Block(_block_arena, region);
511 map_node_to_block(region, block);
512 C->regalloc()->set_bad(region->_idx);
513 // add a goto node
514 Node* gto = _goto->clone(); // get a new goto node
515 gto->set_req(0, region);
516 // add it to the basic block
517 block->push_node(gto);
518 map_node_to_block(gto, block);
519 C->regalloc()->set_bad(gto->_idx);
520 // hook up successor block
521 block->_succs.map(block->_num_succs++, out);
522 // remap successor's predecessors if necessary
523 for (uint i = 1; i < out->num_preds(); i++) {
524 if (out->pred(i) == proj) out->head()->set_req(i, gto);
525 }
526 // remap predecessor's successor to new block
527 in->_succs.map(succ_no, block);
528 // Set the frequency of the new block
529 block->_freq = freq;
530 // add new basic block to basic block list
531 add_block_at(block_no + 1, block);
532 }
533
534 // Does this block end in a multiway branch that cannot have the default case
535 // flipped for another case?
536 static bool no_flip_branch(Block *b) {
537 int branch_idx = b->number_of_nodes() - b->_num_succs-1;
538 if (branch_idx < 1) {
539 return false;
540 }
541 Node *branch = b->get_node(branch_idx);
542 if (branch->is_Catch()) {
543 return true;
544 }
545 if (branch->is_Mach()) {
546 if (branch->is_MachNullCheck()) {
547 return true;
548 }
549 int iop = branch->as_Mach()->ideal_Opcode();
550 if (iop == Op_FastLock || iop == Op_FastUnlock) {
551 return true;
552 }
553 // Don't flip if branch has an implicit check.
554 if (branch->as_Mach()->is_TrapBasedCheckNode()) {
555 return true;
556 }
557 }
558 return false;
559 }
560
561 // Check for NeverBranch at block end. This needs to become a GOTO to the
562 // true target. NeverBranch are treated as a conditional branch that always
563 // goes the same direction for most of the optimizer and are used to give a
564 // fake exit path to infinite loops. At this late stage they need to turn
565 // into Goto's so that when you enter the infinite loop you indeed hang.
566 void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) {
567 // Find true target
568 int end_idx = b->end_idx();
569 int idx = b->get_node(end_idx+1)->as_Proj()->_con;
570 Block *succ = b->_succs[idx];
571 Node* gto = _goto->clone(); // get a new goto node
572 gto->set_req(0, b->head());
573 Node *bp = b->get_node(end_idx);
574 b->map_node(gto, end_idx); // Slam over NeverBranch
575 map_node_to_block(gto, b);
576 C->regalloc()->set_bad(gto->_idx);
577 b->pop_node(); // Yank projections
578 b->pop_node(); // Yank projections
579 b->_succs.map(0,succ); // Map only successor
580 b->_num_succs = 1;
581 // remap successor's predecessors if necessary
582 uint j;
583 for( j = 1; j < succ->num_preds(); j++)
584 if( succ->pred(j)->in(0) == bp )
585 succ->head()->set_req(j, gto);
586 // Kill alternate exit path
587 Block *dead = b->_succs[1-idx];
588 for( j = 1; j < dead->num_preds(); j++)
589 if( dead->pred(j)->in(0) == bp )
590 break;
591 // Scan through block, yanking dead path from
592 // all regions and phis.
593 dead->head()->del_req(j);
594 for( int k = 1; dead->get_node(k)->is_Phi(); k++ )
595 dead->get_node(k)->del_req(j);
596 }
597
598 // Helper function to move block bx to the slot following b_index. Return
599 // true if the move is successful, otherwise false
600 bool PhaseCFG::move_to_next(Block* bx, uint b_index) {
601 if (bx == NULL) return false;
602
603 // Return false if bx is already scheduled.
604 uint bx_index = bx->_pre_order;
605 if ((bx_index <= b_index) && (get_block(bx_index) == bx)) {
606 return false;
607 }
608
609 // Find the current index of block bx on the block list
610 bx_index = b_index + 1;
611 while (bx_index < number_of_blocks() && get_block(bx_index) != bx) {
612 bx_index++;
613 }
614 assert(get_block(bx_index) == bx, "block not found");
615
616 // If the previous block conditionally falls into bx, return false,
617 // because moving bx will create an extra jump.
618 for(uint k = 1; k < bx->num_preds(); k++ ) {
619 Block* pred = get_block_for_node(bx->pred(k));
620 if (pred == get_block(bx_index - 1)) {
621 if (pred->_num_succs != 1) {
622 return false;
623 }
624 }
625 }
626
627 // Reinsert bx just past block 'b'
628 _blocks.remove(bx_index);
629 _blocks.insert(b_index + 1, bx);
630 return true;
631 }
632
633 // Move empty and uncommon blocks to the end.
634 void PhaseCFG::move_to_end(Block *b, uint i) {
635 int e = b->is_Empty();
636 if (e != Block::not_empty) {
637 if (e == Block::empty_with_goto) {
638 // Remove the goto, but leave the block.
639 b->pop_node();
640 }
641 // Mark this block as a connector block, which will cause it to be
642 // ignored in certain functions such as non_connector_successor().
643 b->set_connector();
644 }
645 // Move the empty block to the end, and don't recheck.
646 _blocks.remove(i);
647 _blocks.push(b);
648 }
649
650 // Set loop alignment for every block
651 void PhaseCFG::set_loop_alignment() {
652 uint last = number_of_blocks();
653 assert(get_block(0) == get_root_block(), "");
654
655 for (uint i = 1; i < last; i++) {
656 Block* block = get_block(i);
657 if (block->head()->is_Loop()) {
658 block->set_loop_alignment(block);
659 }
660 }
661 }
662
663 // Make empty basic blocks to be "connector" blocks, Move uncommon blocks
664 // to the end.
665 void PhaseCFG::remove_empty_blocks() {
666 // Move uncommon blocks to the end
667 uint last = number_of_blocks();
668 assert(get_block(0) == get_root_block(), "");
669
670 for (uint i = 1; i < last; i++) {
671 Block* block = get_block(i);
672 if (block->is_connector()) {
673 break;
674 }
675
676 // Check for NeverBranch at block end. This needs to become a GOTO to the
677 // true target. NeverBranch are treated as a conditional branch that
678 // always goes the same direction for most of the optimizer and are used
679 // to give a fake exit path to infinite loops. At this late stage they
680 // need to turn into Goto's so that when you enter the infinite loop you
681 // indeed hang.
682 if (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) {
683 convert_NeverBranch_to_Goto(block);
684 }
685
686 // Look for uncommon blocks and move to end.
687 if (!C->do_freq_based_layout()) {
688 if (is_uncommon(block)) {
689 move_to_end(block, i);
690 last--; // No longer check for being uncommon!
691 if (no_flip_branch(block)) { // Fall-thru case must follow?
692 // Find the fall-thru block
693 block = get_block(i);
694 move_to_end(block, i);
695 last--;
696 }
697 // backup block counter post-increment
698 i--;
699 }
700 }
701 }
702
703 // Move empty blocks to the end
704 last = number_of_blocks();
705 for (uint i = 1; i < last; i++) {
706 Block* block = get_block(i);
707 if (block->is_Empty() != Block::not_empty) {
708 move_to_end(block, i);
709 last--;
710 i--;
711 }
712 } // End of for all blocks
713 }
714
715 Block *PhaseCFG::fixup_trap_based_check(Node *branch, Block *block, int block_pos, Block *bnext) {
716 // Trap based checks must fall through to the successor with
717 // PROB_ALWAYS.
718 // They should be an If with 2 successors.
719 assert(branch->is_MachIf(), "must be If");
720 assert(block->_num_succs == 2, "must have 2 successors");
721
722 // Get the If node and the projection for the first successor.
723 MachIfNode *iff = block->get_node(block->number_of_nodes()-3)->as_MachIf();
724 ProjNode *proj0 = block->get_node(block->number_of_nodes()-2)->as_Proj();
725 ProjNode *proj1 = block->get_node(block->number_of_nodes()-1)->as_Proj();
726 ProjNode *projt = (proj0->Opcode() == Op_IfTrue) ? proj0 : proj1;
727 ProjNode *projf = (proj0->Opcode() == Op_IfFalse) ? proj0 : proj1;
728
729 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
730 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0");
731 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1");
732
733 ProjNode *proj_always;
734 ProjNode *proj_never;
735 // We must negate the branch if the implicit check doesn't follow
736 // the branch's TRUE path. Then, the new TRUE branch target will
737 // be the old FALSE branch target.
738 if (iff->_prob <= 2*PROB_NEVER) { // There are small rounding errors.
739 proj_never = projt;
740 proj_always = projf;
741 } else {
742 // We must negate the branch if the trap doesn't follow the
743 // branch's TRUE path. Then, the new TRUE branch target will
744 // be the old FALSE branch target.
745 proj_never = projf;
746 proj_always = projt;
747 iff->negate();
748 }
749 assert(iff->_prob <= 2*PROB_NEVER, "Trap based checks are expected to trap never!");
750 // Map the successors properly
751 block->_succs.map(0, get_block_for_node(proj_never ->raw_out(0))); // The target of the trap.
752 block->_succs.map(1, get_block_for_node(proj_always->raw_out(0))); // The fall through target.
753
754 if (block->get_node(block->number_of_nodes() - block->_num_succs + 1) != proj_always) {
755 block->map_node(proj_never, block->number_of_nodes() - block->_num_succs + 0);
756 block->map_node(proj_always, block->number_of_nodes() - block->_num_succs + 1);
757 }
758
759 // Place the fall through block after this block.
760 Block *bs1 = block->non_connector_successor(1);
761 if (bs1 != bnext && move_to_next(bs1, block_pos)) {
762 bnext = bs1;
763 }
764 // If the fall through block still is not the next block, insert a goto.
765 if (bs1 != bnext) {
766 insert_goto_at(block_pos, 1);
767 }
768 return bnext;
769 }
770
771 // Fix up the final control flow for basic blocks.
772 void PhaseCFG::fixup_flow() {
773 // Fixup final control flow for the blocks. Remove jump-to-next
774 // block. If neither arm of an IF follows the conditional branch, we
775 // have to add a second jump after the conditional. We place the
776 // TRUE branch target in succs[0] for both GOTOs and IFs.
777 bool found_fixup_loops = false;
778 for (uint i = 0; i < number_of_blocks(); i++) {
779 Block* block = get_block(i);
780 block->_pre_order = i; // turn pre-order into block-index
781
782 Node *bh = block->head();
783 if (bh->is_Loop()) {
784 LoopNode *loop = bh->as_Loop();
785 if (loop->is_inner_loop() && loop->is_multiversioned() && loop->is_vectorized_loop() && !loop->range_checks_present()) {
786 found_fixup_loops = true;
787 }
788 }
789
790 // Connector blocks need no further processing.
791 if (block->is_connector()) {
792 assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end");
793 continue;
794 }
795 assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors");
796
797 Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL;
798 Block* bs0 = block->non_connector_successor(0);
799
800 // Check for multi-way branches where I cannot negate the test to
801 // exchange the true and false targets.
802 if (no_flip_branch(block)) {
803 // Find fall through case - if must fall into its target.
804 // Get the index of the branch's first successor.
805 int branch_idx = block->number_of_nodes() - block->_num_succs;
806
807 // The branch is 1 before the branch's first successor.
808 Node *branch = block->get_node(branch_idx-1);
809
810 // Handle no-flip branches which have implicit checks and which require
811 // special block ordering and individual semantics of the 'fall through
812 // case'.
813 if ((TrapBasedNullChecks || TrapBasedRangeChecks) &&
814 branch->is_Mach() && branch->as_Mach()->is_TrapBasedCheckNode()) {
815 bnext = fixup_trap_based_check(branch, block, i, bnext);
816 } else {
817 // Else, default handling for no-flip branches
818 for (uint j2 = 0; j2 < block->_num_succs; j2++) {
819 const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj();
820 if (p->_con == 0) {
821 // successor j2 is fall through case
822 if (block->non_connector_successor(j2) != bnext) {
823 // but it is not the next block => insert a goto
824 insert_goto_at(i, j2);
825 }
826 // Put taken branch in slot 0
827 if (j2 == 0 && block->_num_succs == 2) {
828 // Flip targets in succs map
829 Block *tbs0 = block->_succs[0];
830 Block *tbs1 = block->_succs[1];
831 block->_succs.map(0, tbs1);
832 block->_succs.map(1, tbs0);
833 }
834 break;
835 }
836 }
837 }
838
839 // Remove all CatchProjs
840 for (uint j = 0; j < block->_num_succs; j++) {
841 block->pop_node();
842 }
843
844 } else if (block->_num_succs == 1) {
845 // Block ends in a Goto?
846 if (bnext == bs0) {
847 // We fall into next block; remove the Goto
848 block->pop_node();
849 }
850
851 } else if(block->_num_succs == 2) { // Block ends in a If?
852 // Get opcode of 1st projection (matches _succs[0])
853 // Note: Since this basic block has 2 exits, the last 2 nodes must
854 // be projections (in any order), the 3rd last node must be
855 // the IfNode (we have excluded other 2-way exits such as
856 // CatchNodes already).
857 MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach();
858 ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj();
859 ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj();
860
861 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
862 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0");
863 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1");
864
865 Block* bs1 = block->non_connector_successor(1);
866
867 // Check for neither successor block following the current
868 // block ending in a conditional. If so, move one of the
869 // successors after the current one, provided that the
870 // successor was previously unscheduled, but moveable
871 // (i.e., all paths to it involve a branch).
872 if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) {
873 // Choose the more common successor based on the probability
874 // of the conditional branch.
875 Block* bx = bs0;
876 Block* by = bs1;
877
878 // _prob is the probability of taking the true path. Make
879 // p the probability of taking successor #1.
880 float p = iff->as_MachIf()->_prob;
881 if (proj0->Opcode() == Op_IfTrue) {
882 p = 1.0 - p;
883 }
884
885 // Prefer successor #1 if p > 0.5
886 if (p > PROB_FAIR) {
887 bx = bs1;
888 by = bs0;
889 }
890
891 // Attempt the more common successor first
892 if (move_to_next(bx, i)) {
893 bnext = bx;
894 } else if (move_to_next(by, i)) {
895 bnext = by;
896 }
897 }
898
899 // Check for conditional branching the wrong way. Negate
900 // conditional, if needed, so it falls into the following block
901 // and branches to the not-following block.
902
903 // Check for the next block being in succs[0]. We are going to branch
904 // to succs[0], so we want the fall-thru case as the next block in
905 // succs[1].
906 if (bnext == bs0) {
907 // Fall-thru case in succs[0], so flip targets in succs map
908 Block* tbs0 = block->_succs[0];
909 Block* tbs1 = block->_succs[1];
910 block->_succs.map(0, tbs1);
911 block->_succs.map(1, tbs0);
912 // Flip projection for each target
913 ProjNode* tmp = proj0;
914 proj0 = proj1;
915 proj1 = tmp;
916
917 } else if(bnext != bs1) {
918 // Need a double-branch
919 // The existing conditional branch need not change.
920 // Add a unconditional branch to the false target.
921 // Alas, it must appear in its own block and adding a
922 // block this late in the game is complicated. Sigh.
923 insert_goto_at(i, 1);
924 }
925
926 // Make sure we TRUE branch to the target
927 if (proj0->Opcode() == Op_IfFalse) {
928 iff->as_MachIf()->negate();
929 }
930
931 block->pop_node(); // Remove IfFalse & IfTrue projections
932 block->pop_node();
933
934 } else {
935 // Multi-exit block, e.g. a switch statement
936 // But we don't need to do anything here
937 }
938 } // End of for all blocks
939
940 if (found_fixup_loops) {
941 // find all fixup-loops and process them
942 for (uint i = 0; i < number_of_blocks(); i++) {
943 Block* block = get_block(i);
944 Node *bh = block->head();
945 if (bh->is_Loop()) {
946 LoopNode *loop = bh->as_Loop();
947 // fixup loops are only marked for processing when they are predicated and
948 // vectorized else they are just post loops.
949 if (Matcher::has_predicated_vectors()) {
950 if (loop->is_inner_loop() && loop->is_multiversioned() && loop->is_vectorized_loop() && !loop->range_checks_present()) {
951 CFGLoop *cur_loop = block->_loop;
952 // fixup loops can have multiple exits, so we need to find the backedge
953 Block *back_edge = cur_loop->backedge_block();
954 if (back_edge) {
955 // fetch the region of the back edge
956 Node *backedge_region = back_edge->get_node(0);
957 Block *idom = back_edge->_idom;
958 if (backedge_region->is_Region()) {
959 Node *if_true = backedge_region->in(1);
960 if (if_true->Opcode() == Op_IfTrue) {
961 Node *backedge_iff = if_true->in(0);
962 if (backedge_iff->is_MachIf() && idom) {
963 for (uint j = 0; j < idom->number_of_nodes(); j++) {
964 Node *n = idom->get_node(j);
965 if (n == backedge_iff) {
966 MachMskNode *mask = new MachMskNode(true);
967 if (mask) {
968 idom->insert_node(mask, j);
969 map_node_to_block(mask, idom);
970 break;
971 }
972 }
973 }
974 }
975 }
976 }
977 }
978 }
979 }
980 }
981 }
982 }
983 }
984
985
986 // postalloc_expand: Expand nodes after register allocation.
987 //
988 // postalloc_expand has to be called after register allocation, just
989 // before output (i.e. scheduling). It only gets called if
990 // Matcher::require_postalloc_expand is true.
991 //
992 // Background:
993 //
994 // Nodes that are expandend (one compound node requiring several
995 // assembler instructions to be implemented split into two or more
996 // non-compound nodes) after register allocation are not as nice as
997 // the ones expanded before register allocation - they don't
998 // participate in optimizations as global code motion. But after
999 // register allocation we can expand nodes that use registers which
1000 // are not spillable or registers that are not allocated, because the
1001 // old compound node is simply replaced (in its location in the basic
1002 // block) by a new subgraph which does not contain compound nodes any
1003 // more. The scheduler called during output can later on process these
1004 // non-compound nodes.
1005 //
1006 // Implementation:
1007 //
1008 // Nodes requiring postalloc expand are specified in the ad file by using
1009 // a postalloc_expand statement instead of ins_encode. A postalloc_expand
1010 // contains a single call to an encoding, as does an ins_encode
1011 // statement. Instead of an emit() function a postalloc_expand() function
1012 // is generated that doesn't emit assembler but creates a new
1013 // subgraph. The code below calls this postalloc_expand function for each
1014 // node with the appropriate attribute. This function returns the new
1015 // nodes generated in an array passed in the call. The old node,
1016 // potential MachTemps before and potential Projs after it then get
1017 // disconnected and replaced by the new nodes. The instruction
1018 // generating the result has to be the last one in the array. In
1019 // general it is assumed that Projs after the node expanded are
1020 // kills. These kills are not required any more after expanding as
1021 // there are now explicitly visible def-use chains and the Projs are
1022 // removed. This does not hold for calls: They do not only have
1023 // kill-Projs but also Projs defining values. Therefore Projs after
1024 // the node expanded are removed for all but for calls. If a node is
1025 // to be reused, it must be added to the nodes list returned, and it
1026 // will be added again.
1027 //
1028 // Implementing the postalloc_expand function for a node in an enc_class
1029 // is rather tedious. It requires knowledge about many node details, as
1030 // the nodes and the subgraph must be hand crafted. To simplify this,
1031 // adlc generates some utility variables into the postalloc_expand function,
1032 // e.g., holding the operands as specified by the postalloc_expand encoding
1033 // specification, e.g.:
1034 // * unsigned idx_<par_name> holding the index of the node in the ins
1035 // * Node *n_<par_name> holding the node loaded from the ins
1036 // * MachOpnd *op_<par_name> holding the corresponding operand
1037 //
1038 // The ordering of operands can not be determined by looking at a
1039 // rule. Especially if a match rule matches several different trees,
1040 // several nodes are generated from one instruct specification with
1041 // different operand orderings. In this case the adlc generated
1042 // variables are the only way to access the ins and operands
1043 // deterministically.
1044 //
1045 // If assigning a register to a node that contains an oop, don't
1046 // forget to call ra_->set_oop() for the node.
1047 void PhaseCFG::postalloc_expand(PhaseRegAlloc* _ra) {
1048 GrowableArray <Node *> new_nodes(32); // Array with new nodes filled by postalloc_expand function of node.
1049 GrowableArray <Node *> remove(32);
1050 GrowableArray <Node *> succs(32);
1051 unsigned int max_idx = C->unique(); // Remember to distinguish new from old nodes.
1052 DEBUG_ONLY(bool foundNode = false);
1053
1054 // for all blocks
1055 for (uint i = 0; i < number_of_blocks(); i++) {
1056 Block *b = _blocks[i];
1057 // For all instructions in the current block.
1058 for (uint j = 0; j < b->number_of_nodes(); j++) {
1059 Node *n = b->get_node(j);
1060 if (n->is_Mach() && n->as_Mach()->requires_postalloc_expand()) {
1061 #ifdef ASSERT
1062 if (TracePostallocExpand) {
1063 if (!foundNode) {
1064 foundNode = true;
1065 tty->print("POSTALLOC EXPANDING %d %s\n", C->compile_id(),
1066 C->method() ? C->method()->name()->as_utf8() : C->stub_name());
1067 }
1068 tty->print(" postalloc expanding "); n->dump();
1069 if (Verbose) {
1070 tty->print(" with ins:\n");
1071 for (uint k = 0; k < n->len(); ++k) {
1072 if (n->in(k)) { tty->print(" "); n->in(k)->dump(); }
1073 }
1074 }
1075 }
1076 #endif
1077 new_nodes.clear();
1078 // Collect nodes that have to be removed from the block later on.
1079 uint req = n->req();
1080 remove.clear();
1081 for (uint k = 0; k < req; ++k) {
1082 if (n->in(k) && n->in(k)->is_MachTemp()) {
1083 remove.push(n->in(k)); // MachTemps which are inputs to the old node have to be removed.
1084 n->in(k)->del_req(0);
1085 j--;
1086 }
1087 }
1088
1089 // Check whether we can allocate enough nodes. We set a fix limit for
1090 // the size of postalloc expands with this.
1091 uint unique_limit = C->unique() + 40;
1092 if (unique_limit >= _ra->node_regs_max_index()) {
1093 Compile::current()->record_failure("out of nodes in postalloc expand");
1094 return;
1095 }
1096
1097 // Emit (i.e. generate new nodes).
1098 n->as_Mach()->postalloc_expand(&new_nodes, _ra);
1099
1100 assert(C->unique() < unique_limit, "You allocated too many nodes in your postalloc expand.");
1101
1102 // Disconnect the inputs of the old node.
1103 //
1104 // We reuse MachSpillCopy nodes. If we need to expand them, there
1105 // are many, so reusing pays off. If reused, the node already
1106 // has the new ins. n must be the last node on new_nodes list.
1107 if (!n->is_MachSpillCopy()) {
1108 for (int k = req - 1; k >= 0; --k) {
1109 n->del_req(k);
1110 }
1111 }
1112
1113 #ifdef ASSERT
1114 // Check that all nodes have proper operands.
1115 for (int k = 0; k < new_nodes.length(); ++k) {
1116 if (new_nodes.at(k)->_idx < max_idx || !new_nodes.at(k)->is_Mach()) continue; // old node, Proj ...
1117 MachNode *m = new_nodes.at(k)->as_Mach();
1118 for (unsigned int l = 0; l < m->num_opnds(); ++l) {
1119 if (MachOper::notAnOper(m->_opnds[l])) {
1120 outputStream *os = tty;
1121 os->print("Node %s ", m->Name());
1122 os->print("has invalid opnd %d: %p\n", l, m->_opnds[l]);
1123 assert(0, "Invalid operands, see inline trace in hs_err_pid file.");
1124 }
1125 }
1126 }
1127 #endif
1128
1129 // Collect succs of old node in remove (for projections) and in succs (for
1130 // all other nodes) do _not_ collect projections in remove (but in succs)
1131 // in case the node is a call. We need the projections for calls as they are
1132 // associated with registes (i.e. they are defs).
1133 succs.clear();
1134 for (DUIterator k = n->outs(); n->has_out(k); k++) {
1135 if (n->out(k)->is_Proj() && !n->is_MachCall() && !n->is_MachBranch()) {
1136 remove.push(n->out(k));
1137 } else {
1138 succs.push(n->out(k));
1139 }
1140 }
1141 // Replace old node n as input of its succs by last of the new nodes.
1142 for (int k = 0; k < succs.length(); ++k) {
1143 Node *succ = succs.at(k);
1144 for (uint l = 0; l < succ->req(); ++l) {
1145 if (succ->in(l) == n) {
1146 succ->set_req(l, new_nodes.at(new_nodes.length() - 1));
1147 }
1148 }
1149 for (uint l = succ->req(); l < succ->len(); ++l) {
1150 if (succ->in(l) == n) {
1151 succ->set_prec(l, new_nodes.at(new_nodes.length() - 1));
1152 }
1153 }
1154 }
1155
1156 // Index of old node in block.
1157 uint index = b->find_node(n);
1158 // Insert new nodes into block and map them in nodes->blocks array
1159 // and remember last node in n2.
1160 Node *n2 = NULL;
1161 for (int k = 0; k < new_nodes.length(); ++k) {
1162 n2 = new_nodes.at(k);
1163 b->insert_node(n2, ++index);
1164 map_node_to_block(n2, b);
1165 }
1166
1167 // Add old node n to remove and remove them all from block.
1168 remove.push(n);
1169 j--;
1170 #ifdef ASSERT
1171 if (TracePostallocExpand && Verbose) {
1172 tty->print(" removing:\n");
1173 for (int k = 0; k < remove.length(); ++k) {
1174 tty->print(" "); remove.at(k)->dump();
1175 }
1176 tty->print(" inserting:\n");
1177 for (int k = 0; k < new_nodes.length(); ++k) {
1178 tty->print(" "); new_nodes.at(k)->dump();
1179 }
1180 }
1181 #endif
1182 for (int k = 0; k < remove.length(); ++k) {
1183 if (b->contains(remove.at(k))) {
1184 b->find_remove(remove.at(k));
1185 } else {
1186 assert(remove.at(k)->is_Proj() && (remove.at(k)->in(0)->is_MachBranch()), "");
1187 }
1188 }
1189 // If anything has been inserted (n2 != NULL), continue after last node inserted.
1190 // This does not always work. Some postalloc expands don't insert any nodes, if they
1191 // do optimizations (e.g., max(x,x)). In this case we decrement j accordingly.
1192 j = n2 ? b->find_node(n2) : j;
1193 }
1194 }
1195 }
1196
1197 #ifdef ASSERT
1198 if (foundNode) {
1199 tty->print("FINISHED %d %s\n", C->compile_id(),
1200 C->method() ? C->method()->name()->as_utf8() : C->stub_name());
1201 tty->flush();
1202 }
1203 #endif
1204 }
1205
1206
1207 //------------------------------dump-------------------------------------------
1208 #ifndef PRODUCT
1209 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const {
1210 const Node *x = end->is_block_proj();
1211 assert( x, "not a CFG" );
1212
1213 // Do not visit this block again
1214 if( visited.test_set(x->_idx) ) return;
1215
1216 // Skip through this block
1217 const Node *p = x;
1218 do {
1219 p = p->in(0); // Move control forward
1220 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
1221 } while( !p->is_block_start() );
1222
1223 // Recursively visit
1224 for (uint i = 1; i < p->req(); i++) {
1225 _dump_cfg(p->in(i), visited);
1226 }
1227
1228 // Dump the block
1229 get_block_for_node(p)->dump(this);
1230 }
1231
1232 void PhaseCFG::dump( ) const {
1233 tty->print("\n--- CFG --- %d BBs\n", number_of_blocks());
1234 if (_blocks.size()) { // Did we do basic-block layout?
1235 for (uint i = 0; i < number_of_blocks(); i++) {
1236 const Block* block = get_block(i);
1237 block->dump(this);
1238 }
1239 } else { // Else do it with a DFS
1240 VectorSet visited(_block_arena);
1241 _dump_cfg(_root,visited);
1242 }
1243 }
1244
1245 void PhaseCFG::dump_headers() {
1246 for (uint i = 0; i < number_of_blocks(); i++) {
1247 Block* block = get_block(i);
1248 if (block != NULL) {
1249 block->dump_head(this);
1250 }
1251 }
1252 }
1253
1254 void PhaseCFG::verify() const {
1255 #ifdef ASSERT
1256 // Verify sane CFG
1257 for (uint i = 0; i < number_of_blocks(); i++) {
1258 Block* block = get_block(i);
1259 uint cnt = block->number_of_nodes();
1260 uint j;
1261 for (j = 0; j < cnt; j++) {
1262 Node *n = block->get_node(j);
1263 assert(get_block_for_node(n) == block, "");
1264 if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) {
1265 assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block");
1266 }
1267 for (uint k = 0; k < n->req(); k++) {
1268 Node *def = n->in(k);
1269 if (def && def != n) {
1270 assert(get_block_for_node(def) || def->is_Con(), "must have block; constants for debug info ok");
1271 // Verify that instructions in the block is in correct order.
1272 // Uses must follow their definition if they are at the same block.
1273 // Mostly done to check that MachSpillCopy nodes are placed correctly
1274 // when CreateEx node is moved in build_ifg_physical().
1275 if (get_block_for_node(def) == block && !(block->head()->is_Loop() && n->is_Phi()) &&
1276 // See (+++) comment in reg_split.cpp
1277 !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) {
1278 bool is_loop = false;
1279 if (n->is_Phi()) {
1280 for (uint l = 1; l < def->req(); l++) {
1281 if (n == def->in(l)) {
1282 is_loop = true;
1283 break; // Some kind of loop
1284 }
1285 }
1286 }
1287 assert(is_loop || block->find_node(def) < j, "uses must follow definitions");
1288 }
1289 }
1290 }
1291 }
1292
1293 j = block->end_idx();
1294 Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj();
1295 assert(bp, "last instruction must be a block proj");
1296 assert(bp == block->get_node(j), "wrong number of successors for this block");
1297 if (bp->is_Catch()) {
1298 while (block->get_node(--j)->is_MachProj()) {
1299 ;
1300 }
1301 assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call");
1302 } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) {
1303 assert(block->_num_succs == 2, "Conditional branch must have two targets");
1304 }
1305 }
1306 #endif
1307 }
1308 #endif
1309
1310 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) {
1311 Copy::zero_to_bytes( _indices, sizeof(uint)*max );
1312 }
1313
1314 void UnionFind::extend( uint from_idx, uint to_idx ) {
1315 _nesting.check();
1316 if( from_idx >= _max ) {
1317 uint size = 16;
1318 while( size <= from_idx ) size <<=1;
1319 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size );
1320 _max = size;
1321 }
1322 while( _cnt <= from_idx ) _indices[_cnt++] = 0;
1323 _indices[from_idx] = to_idx;
1324 }
1325
1326 void UnionFind::reset( uint max ) {
1327 // Force the Union-Find mapping to be at least this large
1328 extend(max,0);
1329 // Initialize to be the ID mapping.
1330 for( uint i=0; i<max; i++ ) map(i,i);
1331 }
1332
1333 // Straight out of Tarjan's union-find algorithm
1334 uint UnionFind::Find_compress( uint idx ) {
1335 uint cur = idx;
1336 uint next = lookup(cur);
1337 while( next != cur ) { // Scan chain of equivalences
1338 assert( next < cur, "always union smaller" );
1339 cur = next; // until find a fixed-point
1340 next = lookup(cur);
1341 }
1342 // Core of union-find algorithm: update chain of
1343 // equivalences to be equal to the root.
1344 while( idx != next ) {
1345 uint tmp = lookup(idx);
1346 map(idx, next);
1347 idx = tmp;
1348 }
1349 return idx;
1350 }
1351
1352 // Like Find above, but no path compress, so bad asymptotic behavior
1353 uint UnionFind::Find_const( uint idx ) const {
1354 if( idx == 0 ) return idx; // Ignore the zero idx
1355 // Off the end? This can happen during debugging dumps
1356 // when data structures have not finished being updated.
1357 if( idx >= _max ) return idx;
1358 uint next = lookup(idx);
1359 while( next != idx ) { // Scan chain of equivalences
1360 idx = next; // until find a fixed-point
1361 next = lookup(idx);
1362 }
1363 return next;
1364 }
1365
1366 // union 2 sets together.
1367 void UnionFind::Union( uint idx1, uint idx2 ) {
1368 uint src = Find(idx1);
1369 uint dst = Find(idx2);
1370 assert( src, "" );
1371 assert( dst, "" );
1372 assert( src < _max, "oob" );
1373 assert( dst < _max, "oob" );
1374 assert( src < dst, "always union smaller" );
1375 map(dst,src);
1376 }
1377
1378 #ifndef PRODUCT
1379 void Trace::dump( ) const {
1380 tty->print_cr("Trace (freq %f)", first_block()->_freq);
1381 for (Block *b = first_block(); b != NULL; b = next(b)) {
1382 tty->print(" B%d", b->_pre_order);
1383 if (b->head()->is_Loop()) {
1384 tty->print(" (L%d)", b->compute_loop_alignment());
1385 }
1386 if (b->has_loop_alignment()) {
1387 tty->print(" (T%d)", b->code_alignment());
1388 }
1389 }
1390 tty->cr();
1391 }
1392
1393 void CFGEdge::dump( ) const {
1394 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ",
1395 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct);
1396 switch(state()) {
1397 case connected:
1398 tty->print("connected");
1399 break;
1400 case open:
1401 tty->print("open");
1402 break;
1403 case interior:
1404 tty->print("interior");
1405 break;
1406 }
1407 if (infrequent()) {
1408 tty->print(" infrequent");
1409 }
1410 tty->cr();
1411 }
1412 #endif
1413
1414 // Comparison function for edges
1415 static int edge_order(CFGEdge **e0, CFGEdge **e1) {
1416 float freq0 = (*e0)->freq();
1417 float freq1 = (*e1)->freq();
1418 if (freq0 != freq1) {
1419 return freq0 > freq1 ? -1 : 1;
1420 }
1421
1422 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo;
1423 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo;
1424
1425 return dist1 - dist0;
1426 }
1427
1428 // Comparison function for edges
1429 extern "C" int trace_frequency_order(const void *p0, const void *p1) {
1430 Trace *tr0 = *(Trace **) p0;
1431 Trace *tr1 = *(Trace **) p1;
1432 Block *b0 = tr0->first_block();
1433 Block *b1 = tr1->first_block();
1434
1435 // The trace of connector blocks goes at the end;
1436 // we only expect one such trace
1437 if (b0->is_connector() != b1->is_connector()) {
1438 return b1->is_connector() ? -1 : 1;
1439 }
1440
1441 // Pull more frequently executed blocks to the beginning
1442 float freq0 = b0->_freq;
1443 float freq1 = b1->_freq;
1444 if (freq0 != freq1) {
1445 return freq0 > freq1 ? -1 : 1;
1446 }
1447
1448 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo;
1449
1450 return diff;
1451 }
1452
1453 // Find edges of interest, i.e, those which can fall through. Presumes that
1454 // edges which don't fall through are of low frequency and can be generally
1455 // ignored. Initialize the list of traces.
1456 void PhaseBlockLayout::find_edges() {
1457 // Walk the blocks, creating edges and Traces
1458 uint i;
1459 Trace *tr = NULL;
1460 for (i = 0; i < _cfg.number_of_blocks(); i++) {
1461 Block* b = _cfg.get_block(i);
1462 tr = new Trace(b, next, prev);
1463 traces[tr->id()] = tr;
1464
1465 // All connector blocks should be at the end of the list
1466 if (b->is_connector()) break;
1467
1468 // If this block and the next one have a one-to-one successor
1469 // predecessor relationship, simply append the next block
1470 int nfallthru = b->num_fall_throughs();
1471 while (nfallthru == 1 &&
1472 b->succ_fall_through(0)) {
1473 Block *n = b->_succs[0];
1474
1475 // Skip over single-entry connector blocks, we don't want to
1476 // add them to the trace.
1477 while (n->is_connector() && n->num_preds() == 1) {
1478 n = n->_succs[0];
1479 }
1480
1481 // We see a merge point, so stop search for the next block
1482 if (n->num_preds() != 1) break;
1483
1484 i++;
1485 assert(n = _cfg.get_block(i), "expecting next block");
1486 tr->append(n);
1487 uf->map(n->_pre_order, tr->id());
1488 traces[n->_pre_order] = NULL;
1489 nfallthru = b->num_fall_throughs();
1490 b = n;
1491 }
1492
1493 if (nfallthru > 0) {
1494 // Create a CFGEdge for each outgoing
1495 // edge that could be a fall-through.
1496 for (uint j = 0; j < b->_num_succs; j++ ) {
1497 if (b->succ_fall_through(j)) {
1498 Block *target = b->non_connector_successor(j);
1499 float freq = b->_freq * b->succ_prob(j);
1500 int from_pct = (int) ((100 * freq) / b->_freq);
1501 int to_pct = (int) ((100 * freq) / target->_freq);
1502 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct));
1503 }
1504 }
1505 }
1506 }
1507
1508 // Group connector blocks into one trace
1509 for (i++; i < _cfg.number_of_blocks(); i++) {
1510 Block *b = _cfg.get_block(i);
1511 assert(b->is_connector(), "connector blocks at the end");
1512 tr->append(b);
1513 uf->map(b->_pre_order, tr->id());
1514 traces[b->_pre_order] = NULL;
1515 }
1516 }
1517
1518 // Union two traces together in uf, and null out the trace in the list
1519 void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) {
1520 uint old_id = old_trace->id();
1521 uint updated_id = updated_trace->id();
1522
1523 uint lo_id = updated_id;
1524 uint hi_id = old_id;
1525
1526 // If from is greater than to, swap values to meet
1527 // UnionFind guarantee.
1528 if (updated_id > old_id) {
1529 lo_id = old_id;
1530 hi_id = updated_id;
1531
1532 // Fix up the trace ids
1533 traces[lo_id] = traces[updated_id];
1534 updated_trace->set_id(lo_id);
1535 }
1536
1537 // Union the lower with the higher and remove the pointer
1538 // to the higher.
1539 uf->Union(lo_id, hi_id);
1540 traces[hi_id] = NULL;
1541 }
1542
1543 // Append traces together via the most frequently executed edges
1544 void PhaseBlockLayout::grow_traces() {
1545 // Order the edges, and drive the growth of Traces via the most
1546 // frequently executed edges.
1547 edges->sort(edge_order);
1548 for (int i = 0; i < edges->length(); i++) {
1549 CFGEdge *e = edges->at(i);
1550
1551 if (e->state() != CFGEdge::open) continue;
1552
1553 Block *src_block = e->from();
1554 Block *targ_block = e->to();
1555
1556 // Don't grow traces along backedges?
1557 if (!BlockLayoutRotateLoops) {
1558 if (targ_block->_rpo <= src_block->_rpo) {
1559 targ_block->set_loop_alignment(targ_block);
1560 continue;
1561 }
1562 }
1563
1564 Trace *src_trace = trace(src_block);
1565 Trace *targ_trace = trace(targ_block);
1566
1567 // If the edge in question can join two traces at their ends,
1568 // append one trace to the other.
1569 if (src_trace->last_block() == src_block) {
1570 if (src_trace == targ_trace) {
1571 e->set_state(CFGEdge::interior);
1572 if (targ_trace->backedge(e)) {
1573 // Reset i to catch any newly eligible edge
1574 // (Or we could remember the first "open" edge, and reset there)
1575 i = 0;
1576 }
1577 } else if (targ_trace->first_block() == targ_block) {
1578 e->set_state(CFGEdge::connected);
1579 src_trace->append(targ_trace);
1580 union_traces(src_trace, targ_trace);
1581 }
1582 }
1583 }
1584 }
1585
1586 // Embed one trace into another, if the fork or join points are sufficiently
1587 // balanced.
1588 void PhaseBlockLayout::merge_traces(bool fall_thru_only) {
1589 // Walk the edge list a another time, looking at unprocessed edges.
1590 // Fold in diamonds
1591 for (int i = 0; i < edges->length(); i++) {
1592 CFGEdge *e = edges->at(i);
1593
1594 if (e->state() != CFGEdge::open) continue;
1595 if (fall_thru_only) {
1596 if (e->infrequent()) continue;
1597 }
1598
1599 Block *src_block = e->from();
1600 Trace *src_trace = trace(src_block);
1601 bool src_at_tail = src_trace->last_block() == src_block;
1602
1603 Block *targ_block = e->to();
1604 Trace *targ_trace = trace(targ_block);
1605 bool targ_at_start = targ_trace->first_block() == targ_block;
1606
1607 if (src_trace == targ_trace) {
1608 // This may be a loop, but we can't do much about it.
1609 e->set_state(CFGEdge::interior);
1610 continue;
1611 }
1612
1613 if (fall_thru_only) {
1614 // If the edge links the middle of two traces, we can't do anything.
1615 // Mark the edge and continue.
1616 if (!src_at_tail & !targ_at_start) {
1617 continue;
1618 }
1619
1620 // Don't grow traces along backedges?
1621 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) {
1622 continue;
1623 }
1624
1625 // If both ends of the edge are available, why didn't we handle it earlier?
1626 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier.");
1627
1628 if (targ_at_start) {
1629 // Insert the "targ" trace in the "src" trace if the insertion point
1630 // is a two way branch.
1631 // Better profitability check possible, but may not be worth it.
1632 // Someday, see if the this "fork" has an associated "join";
1633 // then make a policy on merging this trace at the fork or join.
1634 // For example, other things being equal, it may be better to place this
1635 // trace at the join point if the "src" trace ends in a two-way, but
1636 // the insertion point is one-way.
1637 assert(src_block->num_fall_throughs() == 2, "unexpected diamond");
1638 e->set_state(CFGEdge::connected);
1639 src_trace->insert_after(src_block, targ_trace);
1640 union_traces(src_trace, targ_trace);
1641 } else if (src_at_tail) {
1642 if (src_trace != trace(_cfg.get_root_block())) {
1643 e->set_state(CFGEdge::connected);
1644 targ_trace->insert_before(targ_block, src_trace);
1645 union_traces(targ_trace, src_trace);
1646 }
1647 }
1648 } else if (e->state() == CFGEdge::open) {
1649 // Append traces, even without a fall-thru connection.
1650 // But leave root entry at the beginning of the block list.
1651 if (targ_trace != trace(_cfg.get_root_block())) {
1652 e->set_state(CFGEdge::connected);
1653 src_trace->append(targ_trace);
1654 union_traces(src_trace, targ_trace);
1655 }
1656 }
1657 }
1658 }
1659
1660 // Order the sequence of the traces in some desirable way, and fixup the
1661 // jumps at the end of each block.
1662 void PhaseBlockLayout::reorder_traces(int count) {
1663 ResourceArea *area = Thread::current()->resource_area();
1664 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count);
1665 Block_List worklist;
1666 int new_count = 0;
1667
1668 // Compact the traces.
1669 for (int i = 0; i < count; i++) {
1670 Trace *tr = traces[i];
1671 if (tr != NULL) {
1672 new_traces[new_count++] = tr;
1673 }
1674 }
1675
1676 // The entry block should be first on the new trace list.
1677 Trace *tr = trace(_cfg.get_root_block());
1678 assert(tr == new_traces[0], "entry trace misplaced");
1679
1680 // Sort the new trace list by frequency
1681 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order);
1682
1683 // Patch up the successor blocks
1684 _cfg.clear_blocks();
1685 for (int i = 0; i < new_count; i++) {
1686 Trace *tr = new_traces[i];
1687 if (tr != NULL) {
1688 tr->fixup_blocks(_cfg);
1689 }
1690 }
1691 }
1692
1693 // Order basic blocks based on frequency
1694 PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg)
1695 : Phase(BlockLayout)
1696 , _cfg(cfg) {
1697 ResourceMark rm;
1698 ResourceArea *area = Thread::current()->resource_area();
1699
1700 // List of traces
1701 int size = _cfg.number_of_blocks() + 1;
1702 traces = NEW_ARENA_ARRAY(area, Trace *, size);
1703 memset(traces, 0, size*sizeof(Trace*));
1704 next = NEW_ARENA_ARRAY(area, Block *, size);
1705 memset(next, 0, size*sizeof(Block *));
1706 prev = NEW_ARENA_ARRAY(area, Block *, size);
1707 memset(prev , 0, size*sizeof(Block *));
1708
1709 // List of edges
1710 edges = new GrowableArray<CFGEdge*>;
1711
1712 // Mapping block index --> block_trace
1713 uf = new UnionFind(size);
1714 uf->reset(size);
1715
1716 // Find edges and create traces.
1717 find_edges();
1718
1719 // Grow traces at their ends via most frequent edges.
1720 grow_traces();
1721
1722 // Merge one trace into another, but only at fall-through points.
1723 // This may make diamonds and other related shapes in a trace.
1724 merge_traces(true);
1725
1726 // Run merge again, allowing two traces to be catenated, even if
1727 // one does not fall through into the other. This appends loosely
1728 // related traces to be near each other.
1729 merge_traces(false);
1730
1731 // Re-order all the remaining traces by frequency
1732 reorder_traces(size);
1733
1734 assert(_cfg.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink");
1735 }
1736
1737
1738 // Edge e completes a loop in a trace. If the target block is head of the
1739 // loop, rotate the loop block so that the loop ends in a conditional branch.
1740 bool Trace::backedge(CFGEdge *e) {
1741 bool loop_rotated = false;
1742 Block *src_block = e->from();
1743 Block *targ_block = e->to();
1744
1745 assert(last_block() == src_block, "loop discovery at back branch");
1746 if (first_block() == targ_block) {
1747 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) {
1748 // Find the last block in the trace that has a conditional
1749 // branch.
1750 Block *b;
1751 for (b = last_block(); b != NULL; b = prev(b)) {
1752 if (b->num_fall_throughs() == 2) {
1753 break;
1754 }
1755 }
1756
1757 if (b != last_block() && b != NULL) {
1758 loop_rotated = true;
1759
1760 // Rotate the loop by doing two-part linked-list surgery.
1761 append(first_block());
1762 break_loop_after(b);
1763 }
1764 }
1765
1766 // Backbranch to the top of a trace
1767 // Scroll forward through the trace from the targ_block. If we find
1768 // a loop head before another loop top, use the the loop head alignment.
1769 for (Block *b = targ_block; b != NULL; b = next(b)) {
1770 if (b->has_loop_alignment()) {
1771 break;
1772 }
1773 if (b->head()->is_Loop()) {
1774 targ_block = b;
1775 break;
1776 }
1777 }
1778
1779 first_block()->set_loop_alignment(targ_block);
1780
1781 } else {
1782 // Backbranch into the middle of a trace
1783 targ_block->set_loop_alignment(targ_block);
1784 }
1785
1786 return loop_rotated;
1787 }
1788
1789 // push blocks onto the CFG list
1790 // ensure that blocks have the correct two-way branch sense
1791 void Trace::fixup_blocks(PhaseCFG &cfg) {
1792 Block *last = last_block();
1793 for (Block *b = first_block(); b != NULL; b = next(b)) {
1794 cfg.add_block(b);
1795 if (!b->is_connector()) {
1796 int nfallthru = b->num_fall_throughs();
1797 if (b != last) {
1798 if (nfallthru == 2) {
1799 // Ensure that the sense of the branch is correct
1800 Block *bnext = next(b);
1801 Block *bs0 = b->non_connector_successor(0);
1802
1803 MachNode *iff = b->get_node(b->number_of_nodes() - 3)->as_Mach();
1804 ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj();
1805 ProjNode *proj1 = b->get_node(b->number_of_nodes() - 1)->as_Proj();
1806
1807 if (bnext == bs0) {
1808 // Fall-thru case in succs[0], should be in succs[1]
1809
1810 // Flip targets in _succs map
1811 Block *tbs0 = b->_succs[0];
1812 Block *tbs1 = b->_succs[1];
1813 b->_succs.map( 0, tbs1 );
1814 b->_succs.map( 1, tbs0 );
1815
1816 // Flip projections to match targets
1817 b->map_node(proj1, b->number_of_nodes() - 2);
1818 b->map_node(proj0, b->number_of_nodes() - 1);
1819 }
1820 }
1821 }
1822 }
1823 }
1824 }