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 for (uint i = 0; i < number_of_blocks(); i++) {
778 Block* block = get_block(i);
779 block->_pre_order = i; // turn pre-order into block-index
780
781 // Connector blocks need no further processing.
782 if (block->is_connector()) {
783 assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end");
784 continue;
785 }
786 assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors");
787
788 Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL;
789 Block* bs0 = block->non_connector_successor(0);
790
791 // Check for multi-way branches where I cannot negate the test to
792 // exchange the true and false targets.
793 if (no_flip_branch(block)) {
794 // Find fall through case - if must fall into its target.
795 // Get the index of the branch's first successor.
796 int branch_idx = block->number_of_nodes() - block->_num_succs;
797
798 // The branch is 1 before the branch's first successor.
799 Node *branch = block->get_node(branch_idx-1);
800
801 // Handle no-flip branches which have implicit checks and which require
802 // special block ordering and individual semantics of the 'fall through
803 // case'.
804 if ((TrapBasedNullChecks || TrapBasedRangeChecks) &&
805 branch->is_Mach() && branch->as_Mach()->is_TrapBasedCheckNode()) {
806 bnext = fixup_trap_based_check(branch, block, i, bnext);
807 } else {
808 // Else, default handling for no-flip branches
809 for (uint j2 = 0; j2 < block->_num_succs; j2++) {
810 const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj();
811 if (p->_con == 0) {
812 // successor j2 is fall through case
813 if (block->non_connector_successor(j2) != bnext) {
814 // but it is not the next block => insert a goto
815 insert_goto_at(i, j2);
816 }
817 // Put taken branch in slot 0
818 if (j2 == 0 && block->_num_succs == 2) {
819 // Flip targets in succs map
820 Block *tbs0 = block->_succs[0];
821 Block *tbs1 = block->_succs[1];
822 block->_succs.map(0, tbs1);
823 block->_succs.map(1, tbs0);
824 }
825 break;
826 }
827 }
828 }
829
830 // Remove all CatchProjs
831 for (uint j = 0; j < block->_num_succs; j++) {
832 block->pop_node();
833 }
834
835 } else if (block->_num_succs == 1) {
836 // Block ends in a Goto?
837 if (bnext == bs0) {
838 // We fall into next block; remove the Goto
839 block->pop_node();
840 }
841
842 } else if(block->_num_succs == 2) { // Block ends in a If?
843 // Get opcode of 1st projection (matches _succs[0])
844 // Note: Since this basic block has 2 exits, the last 2 nodes must
845 // be projections (in any order), the 3rd last node must be
846 // the IfNode (we have excluded other 2-way exits such as
847 // CatchNodes already).
848 MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach();
849 ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj();
850 ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj();
851
852 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
853 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0");
854 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1");
855
856 Block* bs1 = block->non_connector_successor(1);
857
858 // Check for neither successor block following the current
859 // block ending in a conditional. If so, move one of the
860 // successors after the current one, provided that the
861 // successor was previously unscheduled, but moveable
862 // (i.e., all paths to it involve a branch).
863 if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) {
864 // Choose the more common successor based on the probability
865 // of the conditional branch.
866 Block* bx = bs0;
867 Block* by = bs1;
868
869 // _prob is the probability of taking the true path. Make
870 // p the probability of taking successor #1.
871 float p = iff->as_MachIf()->_prob;
872 if (proj0->Opcode() == Op_IfTrue) {
873 p = 1.0 - p;
874 }
875
876 // Prefer successor #1 if p > 0.5
877 if (p > PROB_FAIR) {
878 bx = bs1;
879 by = bs0;
880 }
881
882 // Attempt the more common successor first
883 if (move_to_next(bx, i)) {
884 bnext = bx;
885 } else if (move_to_next(by, i)) {
886 bnext = by;
887 }
888 }
889
890 // Check for conditional branching the wrong way. Negate
891 // conditional, if needed, so it falls into the following block
892 // and branches to the not-following block.
893
894 // Check for the next block being in succs[0]. We are going to branch
895 // to succs[0], so we want the fall-thru case as the next block in
896 // succs[1].
897 if (bnext == bs0) {
898 // Fall-thru case in succs[0], so flip targets in succs map
899 Block* tbs0 = block->_succs[0];
900 Block* tbs1 = block->_succs[1];
901 block->_succs.map(0, tbs1);
902 block->_succs.map(1, tbs0);
903 // Flip projection for each target
904 ProjNode* tmp = proj0;
905 proj0 = proj1;
906 proj1 = tmp;
907
908 } else if(bnext != bs1) {
909 // Need a double-branch
910 // The existing conditional branch need not change.
911 // Add a unconditional branch to the false target.
912 // Alas, it must appear in its own block and adding a
913 // block this late in the game is complicated. Sigh.
914 insert_goto_at(i, 1);
915 }
916
917 // Make sure we TRUE branch to the target
918 if (proj0->Opcode() == Op_IfFalse) {
919 iff->as_MachIf()->negate();
920 }
921
922 block->pop_node(); // Remove IfFalse & IfTrue projections
923 block->pop_node();
924
925 } else {
926 // Multi-exit block, e.g. a switch statement
927 // But we don't need to do anything here
928 }
929 } // End of for all blocks
930 }
931
932
933 // postalloc_expand: Expand nodes after register allocation.
934 //
935 // postalloc_expand has to be called after register allocation, just
936 // before output (i.e. scheduling). It only gets called if
937 // Matcher::require_postalloc_expand is true.
938 //
939 // Background:
940 //
941 // Nodes that are expandend (one compound node requiring several
942 // assembler instructions to be implemented split into two or more
943 // non-compound nodes) after register allocation are not as nice as
944 // the ones expanded before register allocation - they don't
945 // participate in optimizations as global code motion. But after
946 // register allocation we can expand nodes that use registers which
947 // are not spillable or registers that are not allocated, because the
948 // old compound node is simply replaced (in its location in the basic
949 // block) by a new subgraph which does not contain compound nodes any
950 // more. The scheduler called during output can later on process these
951 // non-compound nodes.
952 //
953 // Implementation:
954 //
955 // Nodes requiring postalloc expand are specified in the ad file by using
956 // a postalloc_expand statement instead of ins_encode. A postalloc_expand
957 // contains a single call to an encoding, as does an ins_encode
958 // statement. Instead of an emit() function a postalloc_expand() function
959 // is generated that doesn't emit assembler but creates a new
960 // subgraph. The code below calls this postalloc_expand function for each
961 // node with the appropriate attribute. This function returns the new
962 // nodes generated in an array passed in the call. The old node,
963 // potential MachTemps before and potential Projs after it then get
964 // disconnected and replaced by the new nodes. The instruction
965 // generating the result has to be the last one in the array. In
966 // general it is assumed that Projs after the node expanded are
967 // kills. These kills are not required any more after expanding as
968 // there are now explicitly visible def-use chains and the Projs are
969 // removed. This does not hold for calls: They do not only have
970 // kill-Projs but also Projs defining values. Therefore Projs after
971 // the node expanded are removed for all but for calls. If a node is
972 // to be reused, it must be added to the nodes list returned, and it
973 // will be added again.
974 //
975 // Implementing the postalloc_expand function for a node in an enc_class
976 // is rather tedious. It requires knowledge about many node details, as
977 // the nodes and the subgraph must be hand crafted. To simplify this,
978 // adlc generates some utility variables into the postalloc_expand function,
979 // e.g., holding the operands as specified by the postalloc_expand encoding
980 // specification, e.g.:
981 // * unsigned idx_<par_name> holding the index of the node in the ins
982 // * Node *n_<par_name> holding the node loaded from the ins
983 // * MachOpnd *op_<par_name> holding the corresponding operand
984 //
985 // The ordering of operands can not be determined by looking at a
986 // rule. Especially if a match rule matches several different trees,
987 // several nodes are generated from one instruct specification with
988 // different operand orderings. In this case the adlc generated
989 // variables are the only way to access the ins and operands
990 // deterministically.
991 //
992 // If assigning a register to a node that contains an oop, don't
993 // forget to call ra_->set_oop() for the node.
994 void PhaseCFG::postalloc_expand(PhaseRegAlloc* _ra) {
995 GrowableArray <Node *> new_nodes(32); // Array with new nodes filled by postalloc_expand function of node.
996 GrowableArray <Node *> remove(32);
997 GrowableArray <Node *> succs(32);
998 unsigned int max_idx = C->unique(); // Remember to distinguish new from old nodes.
999 DEBUG_ONLY(bool foundNode = false);
1000
1001 // for all blocks
1002 for (uint i = 0; i < number_of_blocks(); i++) {
1003 Block *b = _blocks[i];
1004 // For all instructions in the current block.
1005 for (uint j = 0; j < b->number_of_nodes(); j++) {
1006 Node *n = b->get_node(j);
1007 if (n->is_Mach() && n->as_Mach()->requires_postalloc_expand()) {
1008 #ifdef ASSERT
1009 if (TracePostallocExpand) {
1010 if (!foundNode) {
1011 foundNode = true;
1012 tty->print("POSTALLOC EXPANDING %d %s\n", C->compile_id(),
1013 C->method() ? C->method()->name()->as_utf8() : C->stub_name());
1014 }
1015 tty->print(" postalloc expanding "); n->dump();
1016 if (Verbose) {
1017 tty->print(" with ins:\n");
1018 for (uint k = 0; k < n->len(); ++k) {
1019 if (n->in(k)) { tty->print(" "); n->in(k)->dump(); }
1020 }
1021 }
1022 }
1023 #endif
1024 new_nodes.clear();
1025 // Collect nodes that have to be removed from the block later on.
1026 uint req = n->req();
1027 remove.clear();
1028 for (uint k = 0; k < req; ++k) {
1029 if (n->in(k) && n->in(k)->is_MachTemp()) {
1030 remove.push(n->in(k)); // MachTemps which are inputs to the old node have to be removed.
1031 n->in(k)->del_req(0);
1032 j--;
1033 }
1034 }
1035
1036 // Check whether we can allocate enough nodes. We set a fix limit for
1037 // the size of postalloc expands with this.
1038 uint unique_limit = C->unique() + 40;
1039 if (unique_limit >= _ra->node_regs_max_index()) {
1040 Compile::current()->record_failure("out of nodes in postalloc expand");
1041 return;
1042 }
1043
1044 // Emit (i.e. generate new nodes).
1045 n->as_Mach()->postalloc_expand(&new_nodes, _ra);
1046
1047 assert(C->unique() < unique_limit, "You allocated too many nodes in your postalloc expand.");
1048
1049 // Disconnect the inputs of the old node.
1050 //
1051 // We reuse MachSpillCopy nodes. If we need to expand them, there
1052 // are many, so reusing pays off. If reused, the node already
1053 // has the new ins. n must be the last node on new_nodes list.
1054 if (!n->is_MachSpillCopy()) {
1055 for (int k = req - 1; k >= 0; --k) {
1056 n->del_req(k);
1057 }
1058 }
1059
1060 #ifdef ASSERT
1061 // Check that all nodes have proper operands.
1062 for (int k = 0; k < new_nodes.length(); ++k) {
1063 if (new_nodes.at(k)->_idx < max_idx || !new_nodes.at(k)->is_Mach()) continue; // old node, Proj ...
1064 MachNode *m = new_nodes.at(k)->as_Mach();
1065 for (unsigned int l = 0; l < m->num_opnds(); ++l) {
1066 if (MachOper::notAnOper(m->_opnds[l])) {
1067 outputStream *os = tty;
1068 os->print("Node %s ", m->Name());
1069 os->print("has invalid opnd %d: %p\n", l, m->_opnds[l]);
1070 assert(0, "Invalid operands, see inline trace in hs_err_pid file.");
1071 }
1072 }
1073 }
1074 #endif
1075
1076 // Collect succs of old node in remove (for projections) and in succs (for
1077 // all other nodes) do _not_ collect projections in remove (but in succs)
1078 // in case the node is a call. We need the projections for calls as they are
1079 // associated with registes (i.e. they are defs).
1080 succs.clear();
1081 for (DUIterator k = n->outs(); n->has_out(k); k++) {
1082 if (n->out(k)->is_Proj() && !n->is_MachCall() && !n->is_MachBranch()) {
1083 remove.push(n->out(k));
1084 } else {
1085 succs.push(n->out(k));
1086 }
1087 }
1088 // Replace old node n as input of its succs by last of the new nodes.
1089 for (int k = 0; k < succs.length(); ++k) {
1090 Node *succ = succs.at(k);
1091 for (uint l = 0; l < succ->req(); ++l) {
1092 if (succ->in(l) == n) {
1093 succ->set_req(l, new_nodes.at(new_nodes.length() - 1));
1094 }
1095 }
1096 for (uint l = succ->req(); l < succ->len(); ++l) {
1097 if (succ->in(l) == n) {
1098 succ->set_prec(l, new_nodes.at(new_nodes.length() - 1));
1099 }
1100 }
1101 }
1102
1103 // Index of old node in block.
1104 uint index = b->find_node(n);
1105 // Insert new nodes into block and map them in nodes->blocks array
1106 // and remember last node in n2.
1107 Node *n2 = NULL;
1108 for (int k = 0; k < new_nodes.length(); ++k) {
1109 n2 = new_nodes.at(k);
1110 b->insert_node(n2, ++index);
1111 map_node_to_block(n2, b);
1112 }
1113
1114 // Add old node n to remove and remove them all from block.
1115 remove.push(n);
1116 j--;
1117 #ifdef ASSERT
1118 if (TracePostallocExpand && Verbose) {
1119 tty->print(" removing:\n");
1120 for (int k = 0; k < remove.length(); ++k) {
1121 tty->print(" "); remove.at(k)->dump();
1122 }
1123 tty->print(" inserting:\n");
1124 for (int k = 0; k < new_nodes.length(); ++k) {
1125 tty->print(" "); new_nodes.at(k)->dump();
1126 }
1127 }
1128 #endif
1129 for (int k = 0; k < remove.length(); ++k) {
1130 if (b->contains(remove.at(k))) {
1131 b->find_remove(remove.at(k));
1132 } else {
1133 assert(remove.at(k)->is_Proj() && (remove.at(k)->in(0)->is_MachBranch()), "");
1134 }
1135 }
1136 // If anything has been inserted (n2 != NULL), continue after last node inserted.
1137 // This does not always work. Some postalloc expands don't insert any nodes, if they
1138 // do optimizations (e.g., max(x,x)). In this case we decrement j accordingly.
1139 j = n2 ? b->find_node(n2) : j;
1140 }
1141 }
1142 }
1143
1144 #ifdef ASSERT
1145 if (foundNode) {
1146 tty->print("FINISHED %d %s\n", C->compile_id(),
1147 C->method() ? C->method()->name()->as_utf8() : C->stub_name());
1148 tty->flush();
1149 }
1150 #endif
1151 }
1152
1153
1154 //------------------------------dump-------------------------------------------
1155 #ifndef PRODUCT
1156 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const {
1157 const Node *x = end->is_block_proj();
1158 assert( x, "not a CFG" );
1159
1160 // Do not visit this block again
1161 if( visited.test_set(x->_idx) ) return;
1162
1163 // Skip through this block
1164 const Node *p = x;
1165 do {
1166 p = p->in(0); // Move control forward
1167 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
1168 } while( !p->is_block_start() );
1169
1170 // Recursively visit
1171 for (uint i = 1; i < p->req(); i++) {
1172 _dump_cfg(p->in(i), visited);
1173 }
1174
1175 // Dump the block
1176 get_block_for_node(p)->dump(this);
1177 }
1178
1179 void PhaseCFG::dump( ) const {
1180 tty->print("\n--- CFG --- %d BBs\n", number_of_blocks());
1181 if (_blocks.size()) { // Did we do basic-block layout?
1182 for (uint i = 0; i < number_of_blocks(); i++) {
1183 const Block* block = get_block(i);
1184 block->dump(this);
1185 }
1186 } else { // Else do it with a DFS
1187 VectorSet visited(_block_arena);
1188 _dump_cfg(_root,visited);
1189 }
1190 }
1191
1192 void PhaseCFG::dump_headers() {
1193 for (uint i = 0; i < number_of_blocks(); i++) {
1194 Block* block = get_block(i);
1195 if (block != NULL) {
1196 block->dump_head(this);
1197 }
1198 }
1199 }
1200
1201 void PhaseCFG::verify() const {
1202 #ifdef ASSERT
1203 // Verify sane CFG
1204 for (uint i = 0; i < number_of_blocks(); i++) {
1205 Block* block = get_block(i);
1206 uint cnt = block->number_of_nodes();
1207 uint j;
1208 for (j = 0; j < cnt; j++) {
1209 Node *n = block->get_node(j);
1210 assert(get_block_for_node(n) == block, "");
1211 if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) {
1212 assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block");
1213 }
1214 for (uint k = 0; k < n->req(); k++) {
1215 Node *def = n->in(k);
1216 if (def && def != n) {
1217 assert(get_block_for_node(def) || def->is_Con(), "must have block; constants for debug info ok");
1218 // Verify that instructions in the block is in correct order.
1219 // Uses must follow their definition if they are at the same block.
1220 // Mostly done to check that MachSpillCopy nodes are placed correctly
1221 // when CreateEx node is moved in build_ifg_physical().
1222 if (get_block_for_node(def) == block && !(block->head()->is_Loop() && n->is_Phi()) &&
1223 // See (+++) comment in reg_split.cpp
1224 !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) {
1225 bool is_loop = false;
1226 if (n->is_Phi()) {
1227 for (uint l = 1; l < def->req(); l++) {
1228 if (n == def->in(l)) {
1229 is_loop = true;
1230 break; // Some kind of loop
1231 }
1232 }
1233 }
1234 assert(is_loop || block->find_node(def) < j, "uses must follow definitions");
1235 }
1236 }
1237 }
1238 }
1239
1240 j = block->end_idx();
1241 Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj();
1242 assert(bp, "last instruction must be a block proj");
1243 assert(bp == block->get_node(j), "wrong number of successors for this block");
1244 if (bp->is_Catch()) {
1245 while (block->get_node(--j)->is_MachProj()) {
1246 ;
1247 }
1248 assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call");
1249 } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) {
1250 assert(block->_num_succs == 2, "Conditional branch must have two targets");
1251 }
1252 }
1253 #endif
1254 }
1255 #endif
1256
1257 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) {
1258 Copy::zero_to_bytes( _indices, sizeof(uint)*max );
1259 }
1260
1261 void UnionFind::extend( uint from_idx, uint to_idx ) {
1262 _nesting.check();
1263 if( from_idx >= _max ) {
1264 uint size = 16;
1265 while( size <= from_idx ) size <<=1;
1266 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size );
1267 _max = size;
1268 }
1269 while( _cnt <= from_idx ) _indices[_cnt++] = 0;
1270 _indices[from_idx] = to_idx;
1271 }
1272
1273 void UnionFind::reset( uint max ) {
1274 // Force the Union-Find mapping to be at least this large
1275 extend(max,0);
1276 // Initialize to be the ID mapping.
1277 for( uint i=0; i<max; i++ ) map(i,i);
1278 }
1279
1280 // Straight out of Tarjan's union-find algorithm
1281 uint UnionFind::Find_compress( uint idx ) {
1282 uint cur = idx;
1283 uint next = lookup(cur);
1284 while( next != cur ) { // Scan chain of equivalences
1285 assert( next < cur, "always union smaller" );
1286 cur = next; // until find a fixed-point
1287 next = lookup(cur);
1288 }
1289 // Core of union-find algorithm: update chain of
1290 // equivalences to be equal to the root.
1291 while( idx != next ) {
1292 uint tmp = lookup(idx);
1293 map(idx, next);
1294 idx = tmp;
1295 }
1296 return idx;
1297 }
1298
1299 // Like Find above, but no path compress, so bad asymptotic behavior
1300 uint UnionFind::Find_const( uint idx ) const {
1301 if( idx == 0 ) return idx; // Ignore the zero idx
1302 // Off the end? This can happen during debugging dumps
1303 // when data structures have not finished being updated.
1304 if( idx >= _max ) return idx;
1305 uint next = lookup(idx);
1306 while( next != idx ) { // Scan chain of equivalences
1307 idx = next; // until find a fixed-point
1308 next = lookup(idx);
1309 }
1310 return next;
1311 }
1312
1313 // union 2 sets together.
1314 void UnionFind::Union( uint idx1, uint idx2 ) {
1315 uint src = Find(idx1);
1316 uint dst = Find(idx2);
1317 assert( src, "" );
1318 assert( dst, "" );
1319 assert( src < _max, "oob" );
1320 assert( dst < _max, "oob" );
1321 assert( src < dst, "always union smaller" );
1322 map(dst,src);
1323 }
1324
1325 #ifndef PRODUCT
1326 void Trace::dump( ) const {
1327 tty->print_cr("Trace (freq %f)", first_block()->_freq);
1328 for (Block *b = first_block(); b != NULL; b = next(b)) {
1329 tty->print(" B%d", b->_pre_order);
1330 if (b->head()->is_Loop()) {
1331 tty->print(" (L%d)", b->compute_loop_alignment());
1332 }
1333 if (b->has_loop_alignment()) {
1334 tty->print(" (T%d)", b->code_alignment());
1335 }
1336 }
1337 tty->cr();
1338 }
1339
1340 void CFGEdge::dump( ) const {
1341 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ",
1342 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct);
1343 switch(state()) {
1344 case connected:
1345 tty->print("connected");
1346 break;
1347 case open:
1348 tty->print("open");
1349 break;
1350 case interior:
1351 tty->print("interior");
1352 break;
1353 }
1354 if (infrequent()) {
1355 tty->print(" infrequent");
1356 }
1357 tty->cr();
1358 }
1359 #endif
1360
1361 // Comparison function for edges
1362 static int edge_order(CFGEdge **e0, CFGEdge **e1) {
1363 float freq0 = (*e0)->freq();
1364 float freq1 = (*e1)->freq();
1365 if (freq0 != freq1) {
1366 return freq0 > freq1 ? -1 : 1;
1367 }
1368
1369 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo;
1370 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo;
1371
1372 return dist1 - dist0;
1373 }
1374
1375 // Comparison function for edges
1376 extern "C" int trace_frequency_order(const void *p0, const void *p1) {
1377 Trace *tr0 = *(Trace **) p0;
1378 Trace *tr1 = *(Trace **) p1;
1379 Block *b0 = tr0->first_block();
1380 Block *b1 = tr1->first_block();
1381
1382 // The trace of connector blocks goes at the end;
1383 // we only expect one such trace
1384 if (b0->is_connector() != b1->is_connector()) {
1385 return b1->is_connector() ? -1 : 1;
1386 }
1387
1388 // Pull more frequently executed blocks to the beginning
1389 float freq0 = b0->_freq;
1390 float freq1 = b1->_freq;
1391 if (freq0 != freq1) {
1392 return freq0 > freq1 ? -1 : 1;
1393 }
1394
1395 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo;
1396
1397 return diff;
1398 }
1399
1400 // Find edges of interest, i.e, those which can fall through. Presumes that
1401 // edges which don't fall through are of low frequency and can be generally
1402 // ignored. Initialize the list of traces.
1403 void PhaseBlockLayout::find_edges() {
1404 // Walk the blocks, creating edges and Traces
1405 uint i;
1406 Trace *tr = NULL;
1407 for (i = 0; i < _cfg.number_of_blocks(); i++) {
1408 Block* b = _cfg.get_block(i);
1409 tr = new Trace(b, next, prev);
1410 traces[tr->id()] = tr;
1411
1412 // All connector blocks should be at the end of the list
1413 if (b->is_connector()) break;
1414
1415 // If this block and the next one have a one-to-one successor
1416 // predecessor relationship, simply append the next block
1417 int nfallthru = b->num_fall_throughs();
1418 while (nfallthru == 1 &&
1419 b->succ_fall_through(0)) {
1420 Block *n = b->_succs[0];
1421
1422 // Skip over single-entry connector blocks, we don't want to
1423 // add them to the trace.
1424 while (n->is_connector() && n->num_preds() == 1) {
1425 n = n->_succs[0];
1426 }
1427
1428 // We see a merge point, so stop search for the next block
1429 if (n->num_preds() != 1) break;
1430
1431 i++;
1432 assert(n = _cfg.get_block(i), "expecting next block");
1433 tr->append(n);
1434 uf->map(n->_pre_order, tr->id());
1435 traces[n->_pre_order] = NULL;
1436 nfallthru = b->num_fall_throughs();
1437 b = n;
1438 }
1439
1440 if (nfallthru > 0) {
1441 // Create a CFGEdge for each outgoing
1442 // edge that could be a fall-through.
1443 for (uint j = 0; j < b->_num_succs; j++ ) {
1444 if (b->succ_fall_through(j)) {
1445 Block *target = b->non_connector_successor(j);
1446 float freq = b->_freq * b->succ_prob(j);
1447 int from_pct = (int) ((100 * freq) / b->_freq);
1448 int to_pct = (int) ((100 * freq) / target->_freq);
1449 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct));
1450 }
1451 }
1452 }
1453 }
1454
1455 // Group connector blocks into one trace
1456 for (i++; i < _cfg.number_of_blocks(); i++) {
1457 Block *b = _cfg.get_block(i);
1458 assert(b->is_connector(), "connector blocks at the end");
1459 tr->append(b);
1460 uf->map(b->_pre_order, tr->id());
1461 traces[b->_pre_order] = NULL;
1462 }
1463 }
1464
1465 // Union two traces together in uf, and null out the trace in the list
1466 void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) {
1467 uint old_id = old_trace->id();
1468 uint updated_id = updated_trace->id();
1469
1470 uint lo_id = updated_id;
1471 uint hi_id = old_id;
1472
1473 // If from is greater than to, swap values to meet
1474 // UnionFind guarantee.
1475 if (updated_id > old_id) {
1476 lo_id = old_id;
1477 hi_id = updated_id;
1478
1479 // Fix up the trace ids
1480 traces[lo_id] = traces[updated_id];
1481 updated_trace->set_id(lo_id);
1482 }
1483
1484 // Union the lower with the higher and remove the pointer
1485 // to the higher.
1486 uf->Union(lo_id, hi_id);
1487 traces[hi_id] = NULL;
1488 }
1489
1490 // Append traces together via the most frequently executed edges
1491 void PhaseBlockLayout::grow_traces() {
1492 // Order the edges, and drive the growth of Traces via the most
1493 // frequently executed edges.
1494 edges->sort(edge_order);
1495 for (int i = 0; i < edges->length(); i++) {
1496 CFGEdge *e = edges->at(i);
1497
1498 if (e->state() != CFGEdge::open) continue;
1499
1500 Block *src_block = e->from();
1501 Block *targ_block = e->to();
1502
1503 // Don't grow traces along backedges?
1504 if (!BlockLayoutRotateLoops) {
1505 if (targ_block->_rpo <= src_block->_rpo) {
1506 targ_block->set_loop_alignment(targ_block);
1507 continue;
1508 }
1509 }
1510
1511 Trace *src_trace = trace(src_block);
1512 Trace *targ_trace = trace(targ_block);
1513
1514 // If the edge in question can join two traces at their ends,
1515 // append one trace to the other.
1516 if (src_trace->last_block() == src_block) {
1517 if (src_trace == targ_trace) {
1518 e->set_state(CFGEdge::interior);
1519 if (targ_trace->backedge(e)) {
1520 // Reset i to catch any newly eligible edge
1521 // (Or we could remember the first "open" edge, and reset there)
1522 i = 0;
1523 }
1524 } else if (targ_trace->first_block() == targ_block) {
1525 e->set_state(CFGEdge::connected);
1526 src_trace->append(targ_trace);
1527 union_traces(src_trace, targ_trace);
1528 }
1529 }
1530 }
1531 }
1532
1533 // Embed one trace into another, if the fork or join points are sufficiently
1534 // balanced.
1535 void PhaseBlockLayout::merge_traces(bool fall_thru_only) {
1536 // Walk the edge list a another time, looking at unprocessed edges.
1537 // Fold in diamonds
1538 for (int i = 0; i < edges->length(); i++) {
1539 CFGEdge *e = edges->at(i);
1540
1541 if (e->state() != CFGEdge::open) continue;
1542 if (fall_thru_only) {
1543 if (e->infrequent()) continue;
1544 }
1545
1546 Block *src_block = e->from();
1547 Trace *src_trace = trace(src_block);
1548 bool src_at_tail = src_trace->last_block() == src_block;
1549
1550 Block *targ_block = e->to();
1551 Trace *targ_trace = trace(targ_block);
1552 bool targ_at_start = targ_trace->first_block() == targ_block;
1553
1554 if (src_trace == targ_trace) {
1555 // This may be a loop, but we can't do much about it.
1556 e->set_state(CFGEdge::interior);
1557 continue;
1558 }
1559
1560 if (fall_thru_only) {
1561 // If the edge links the middle of two traces, we can't do anything.
1562 // Mark the edge and continue.
1563 if (!src_at_tail & !targ_at_start) {
1564 continue;
1565 }
1566
1567 // Don't grow traces along backedges?
1568 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) {
1569 continue;
1570 }
1571
1572 // If both ends of the edge are available, why didn't we handle it earlier?
1573 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier.");
1574
1575 if (targ_at_start) {
1576 // Insert the "targ" trace in the "src" trace if the insertion point
1577 // is a two way branch.
1578 // Better profitability check possible, but may not be worth it.
1579 // Someday, see if the this "fork" has an associated "join";
1580 // then make a policy on merging this trace at the fork or join.
1581 // For example, other things being equal, it may be better to place this
1582 // trace at the join point if the "src" trace ends in a two-way, but
1583 // the insertion point is one-way.
1584 assert(src_block->num_fall_throughs() == 2, "unexpected diamond");
1585 e->set_state(CFGEdge::connected);
1586 src_trace->insert_after(src_block, targ_trace);
1587 union_traces(src_trace, targ_trace);
1588 } else if (src_at_tail) {
1589 if (src_trace != trace(_cfg.get_root_block())) {
1590 e->set_state(CFGEdge::connected);
1591 targ_trace->insert_before(targ_block, src_trace);
1592 union_traces(targ_trace, src_trace);
1593 }
1594 }
1595 } else if (e->state() == CFGEdge::open) {
1596 // Append traces, even without a fall-thru connection.
1597 // But leave root entry at the beginning of the block list.
1598 if (targ_trace != trace(_cfg.get_root_block())) {
1599 e->set_state(CFGEdge::connected);
1600 src_trace->append(targ_trace);
1601 union_traces(src_trace, targ_trace);
1602 }
1603 }
1604 }
1605 }
1606
1607 // Order the sequence of the traces in some desirable way, and fixup the
1608 // jumps at the end of each block.
1609 void PhaseBlockLayout::reorder_traces(int count) {
1610 ResourceArea *area = Thread::current()->resource_area();
1611 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count);
1612 Block_List worklist;
1613 int new_count = 0;
1614
1615 // Compact the traces.
1616 for (int i = 0; i < count; i++) {
1617 Trace *tr = traces[i];
1618 if (tr != NULL) {
1619 new_traces[new_count++] = tr;
1620 }
1621 }
1622
1623 // The entry block should be first on the new trace list.
1624 Trace *tr = trace(_cfg.get_root_block());
1625 assert(tr == new_traces[0], "entry trace misplaced");
1626
1627 // Sort the new trace list by frequency
1628 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order);
1629
1630 // Patch up the successor blocks
1631 _cfg.clear_blocks();
1632 for (int i = 0; i < new_count; i++) {
1633 Trace *tr = new_traces[i];
1634 if (tr != NULL) {
1635 tr->fixup_blocks(_cfg);
1636 }
1637 }
1638 }
1639
1640 // Order basic blocks based on frequency
1641 PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg)
1642 : Phase(BlockLayout)
1643 , _cfg(cfg) {
1644 ResourceMark rm;
1645 ResourceArea *area = Thread::current()->resource_area();
1646
1647 // List of traces
1648 int size = _cfg.number_of_blocks() + 1;
1649 traces = NEW_ARENA_ARRAY(area, Trace *, size);
1650 memset(traces, 0, size*sizeof(Trace*));
1651 next = NEW_ARENA_ARRAY(area, Block *, size);
1652 memset(next, 0, size*sizeof(Block *));
1653 prev = NEW_ARENA_ARRAY(area, Block *, size);
1654 memset(prev , 0, size*sizeof(Block *));
1655
1656 // List of edges
1657 edges = new GrowableArray<CFGEdge*>;
1658
1659 // Mapping block index --> block_trace
1660 uf = new UnionFind(size);
1661 uf->reset(size);
1662
1663 // Find edges and create traces.
1664 find_edges();
1665
1666 // Grow traces at their ends via most frequent edges.
1667 grow_traces();
1668
1669 // Merge one trace into another, but only at fall-through points.
1670 // This may make diamonds and other related shapes in a trace.
1671 merge_traces(true);
1672
1673 // Run merge again, allowing two traces to be catenated, even if
1674 // one does not fall through into the other. This appends loosely
1675 // related traces to be near each other.
1676 merge_traces(false);
1677
1678 // Re-order all the remaining traces by frequency
1679 reorder_traces(size);
1680
1681 assert(_cfg.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink");
1682 }
1683
1684
1685 // Edge e completes a loop in a trace. If the target block is head of the
1686 // loop, rotate the loop block so that the loop ends in a conditional branch.
1687 bool Trace::backedge(CFGEdge *e) {
1688 bool loop_rotated = false;
1689 Block *src_block = e->from();
1690 Block *targ_block = e->to();
1691
1692 assert(last_block() == src_block, "loop discovery at back branch");
1693 if (first_block() == targ_block) {
1694 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) {
1695 // Find the last block in the trace that has a conditional
1696 // branch.
1697 Block *b;
1698 for (b = last_block(); b != NULL; b = prev(b)) {
1699 if (b->num_fall_throughs() == 2) {
1700 break;
1701 }
1702 }
1703
1704 if (b != last_block() && b != NULL) {
1705 loop_rotated = true;
1706
1707 // Rotate the loop by doing two-part linked-list surgery.
1708 append(first_block());
1709 break_loop_after(b);
1710 }
1711 }
1712
1713 // Backbranch to the top of a trace
1714 // Scroll forward through the trace from the targ_block. If we find
1715 // a loop head before another loop top, use the the loop head alignment.
1716 for (Block *b = targ_block; b != NULL; b = next(b)) {
1717 if (b->has_loop_alignment()) {
1718 break;
1719 }
1720 if (b->head()->is_Loop()) {
1721 targ_block = b;
1722 break;
1723 }
1724 }
1725
1726 first_block()->set_loop_alignment(targ_block);
1727
1728 } else {
1729 // Backbranch into the middle of a trace
1730 targ_block->set_loop_alignment(targ_block);
1731 }
1732
1733 return loop_rotated;
1734 }
1735
1736 // push blocks onto the CFG list
1737 // ensure that blocks have the correct two-way branch sense
1738 void Trace::fixup_blocks(PhaseCFG &cfg) {
1739 Block *last = last_block();
1740 for (Block *b = first_block(); b != NULL; b = next(b)) {
1741 cfg.add_block(b);
1742 if (!b->is_connector()) {
1743 int nfallthru = b->num_fall_throughs();
1744 if (b != last) {
1745 if (nfallthru == 2) {
1746 // Ensure that the sense of the branch is correct
1747 Block *bnext = next(b);
1748 Block *bs0 = b->non_connector_successor(0);
1749
1750 MachNode *iff = b->get_node(b->number_of_nodes() - 3)->as_Mach();
1751 ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj();
1752 ProjNode *proj1 = b->get_node(b->number_of_nodes() - 1)->as_Proj();
1753
1754 if (bnext == bs0) {
1755 // Fall-thru case in succs[0], should be in succs[1]
1756
1757 // Flip targets in _succs map
1758 Block *tbs0 = b->_succs[0];
1759 Block *tbs1 = b->_succs[1];
1760 b->_succs.map( 0, tbs1 );
1761 b->_succs.map( 1, tbs0 );
1762
1763 // Flip projections to match targets
1764 b->map_node(proj1, b->number_of_nodes() - 2);
1765 b->map_node(proj0, b->number_of_nodes() - 1);
1766 }
1767 }
1768 }
1769 }
1770 }
1771 }