comparison src/share/vm/opto/block.cpp @ 0:a61af66fc99e

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // Optimization - Graph Style
26
27 #include "incls/_precompiled.incl"
28 #include "incls/_block.cpp.incl"
29
30
31 //-----------------------------------------------------------------------------
32 void Block_Array::grow( uint i ) {
33 assert(i >= Max(), "must be an overflow");
34 debug_only(_limit = i+1);
35 if( i < _size ) return;
36 if( !_size ) {
37 _size = 1;
38 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) );
39 _blocks[0] = NULL;
40 }
41 uint old = _size;
42 while( i >= _size ) _size <<= 1; // Double to fit
43 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*));
44 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) );
45 }
46
47 //=============================================================================
48 void Block_List::remove(uint i) {
49 assert(i < _cnt, "index out of bounds");
50 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*)));
51 pop(); // shrink list by one block
52 }
53
54 void Block_List::insert(uint i, Block *b) {
55 push(b); // grow list by one block
56 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*)));
57 _blocks[i] = b;
58 }
59
60
61 //=============================================================================
62
63 uint Block::code_alignment() {
64 // Check for Root block
65 if( _pre_order == 0 ) return CodeEntryAlignment;
66 // Check for Start block
67 if( _pre_order == 1 ) return InteriorEntryAlignment;
68 // Check for loop alignment
69 Node *h = head();
70 if( h->is_Loop() && h->as_Loop()->is_inner_loop() ) {
71 // Pre- and post-loops have low trip count so do not bother with
72 // NOPs for align loop head. The constants are hidden from tuning
73 // but only because my "divide by 4" heuristic surely gets nearly
74 // all possible gain (a "do not align at all" heuristic has a
75 // chance of getting a really tiny gain).
76 if( h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() ||
77 h->as_CountedLoop()->is_post_loop()) )
78 return (OptoLoopAlignment > 4) ? (OptoLoopAlignment>>2) : 1;
79 // Loops with low backedge frequency should not be aligned.
80 Node *n = h->in(LoopNode::LoopBackControl)->in(0);
81 if( n->is_MachIf() && n->as_MachIf()->_prob < 0.01 ) {
82 return 1; // Loop does not loop, more often than not!
83 }
84 return OptoLoopAlignment; // Otherwise align loop head
85 }
86 return 1; // no particular alignment
87 }
88
89 //-----------------------------------------------------------------------------
90 // Compute the size of first 'inst_cnt' instructions in this block.
91 // Return the number of instructions left to compute if the block has
92 // less then 'inst_cnt' instructions.
93 uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt,
94 PhaseRegAlloc* ra) {
95 uint last_inst = _nodes.size();
96 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) {
97 uint inst_size = _nodes[j]->size(ra);
98 if( inst_size > 0 ) {
99 inst_cnt--;
100 uint sz = sum_size + inst_size;
101 if( sz <= (uint)OptoLoopAlignment ) {
102 // Compute size of instructions which fit into fetch buffer only
103 // since all inst_cnt instructions will not fit even if we align them.
104 sum_size = sz;
105 } else {
106 return 0;
107 }
108 }
109 }
110 return inst_cnt;
111 }
112
113 //-----------------------------------------------------------------------------
114 uint Block::find_node( const Node *n ) const {
115 for( uint i = 0; i < _nodes.size(); i++ ) {
116 if( _nodes[i] == n )
117 return i;
118 }
119 ShouldNotReachHere();
120 return 0;
121 }
122
123 // Find and remove n from block list
124 void Block::find_remove( const Node *n ) {
125 _nodes.remove(find_node(n));
126 }
127
128 //------------------------------is_Empty---------------------------------------
129 // Return empty status of a block. Empty blocks contain only the head, other
130 // ideal nodes, and an optional trailing goto.
131 int Block::is_Empty() const {
132
133 // Root or start block is not considered empty
134 if (head()->is_Root() || head()->is_Start()) {
135 return not_empty;
136 }
137
138 int success_result = completely_empty;
139 int end_idx = _nodes.size()-1;
140
141 // Check for ending goto
142 if ((end_idx > 0) && (_nodes[end_idx]->is_Goto())) {
143 success_result = empty_with_goto;
144 end_idx--;
145 }
146
147 // Unreachable blocks are considered empty
148 if (num_preds() <= 1) {
149 return success_result;
150 }
151
152 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes
153 // turn directly into code, because only MachNodes have non-trivial
154 // emit() functions.
155 while ((end_idx > 0) && !_nodes[end_idx]->is_Mach()) {
156 end_idx--;
157 }
158
159 // No room for any interesting instructions?
160 if (end_idx == 0) {
161 return success_result;
162 }
163
164 return not_empty;
165 }
166
167 //------------------------------has_uncommon_code------------------------------
168 // Return true if the block's code implies that it is not likely to be
169 // executed infrequently. Check to see if the block ends in a Halt or
170 // a low probability call.
171 bool Block::has_uncommon_code() const {
172 Node* en = end();
173
174 if (en->is_Goto())
175 en = en->in(0);
176 if (en->is_Catch())
177 en = en->in(0);
178 if (en->is_Proj() && en->in(0)->is_MachCall()) {
179 MachCallNode* call = en->in(0)->as_MachCall();
180 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) {
181 // This is true for slow-path stubs like new_{instance,array},
182 // slow_arraycopy, complete_monitor_locking, uncommon_trap.
183 // The magic number corresponds to the probability of an uncommon_trap,
184 // even though it is a count not a probability.
185 return true;
186 }
187 }
188
189 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode();
190 return op == Op_Halt;
191 }
192
193 //------------------------------is_uncommon------------------------------------
194 // True if block is low enough frequency or guarded by a test which
195 // mostly does not go here.
196 bool Block::is_uncommon( Block_Array &bbs ) const {
197 // Initial blocks must never be moved, so are never uncommon.
198 if (head()->is_Root() || head()->is_Start()) return false;
199
200 // Check for way-low freq
201 if( _freq < BLOCK_FREQUENCY(0.00001f) ) return true;
202
203 // Look for code shape indicating uncommon_trap or slow path
204 if (has_uncommon_code()) return true;
205
206 const float epsilon = 0.05f;
207 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon);
208 uint uncommon_preds = 0;
209 uint freq_preds = 0;
210 uint uncommon_for_freq_preds = 0;
211
212 for( uint i=1; i<num_preds(); i++ ) {
213 Block* guard = bbs[pred(i)->_idx];
214 // Check to see if this block follows its guard 1 time out of 10000
215 // or less.
216 //
217 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which
218 // we intend to be "uncommon", such as slow-path TLE allocation,
219 // predicted call failure, and uncommon trap triggers.
220 //
221 // Use an epsilon value of 5% to allow for variability in frequency
222 // predictions and floating point calculations. The net effect is
223 // that guard_factor is set to 9500.
224 //
225 // Ignore low-frequency blocks.
226 // The next check is (guard->_freq < 1.e-5 * 9500.).
227 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) {
228 uncommon_preds++;
229 } else {
230 freq_preds++;
231 if( _freq < guard->_freq * guard_factor ) {
232 uncommon_for_freq_preds++;
233 }
234 }
235 }
236 if( num_preds() > 1 &&
237 // The block is uncommon if all preds are uncommon or
238 (uncommon_preds == (num_preds()-1) ||
239 // it is uncommon for all frequent preds.
240 uncommon_for_freq_preds == freq_preds) ) {
241 return true;
242 }
243 return false;
244 }
245
246 //------------------------------dump-------------------------------------------
247 #ifndef PRODUCT
248 void Block::dump_bidx(const Block* orig) const {
249 if (_pre_order) tty->print("B%d",_pre_order);
250 else tty->print("N%d", head()->_idx);
251
252 if (Verbose && orig != this) {
253 // Dump the original block's idx
254 tty->print(" (");
255 orig->dump_bidx(orig);
256 tty->print(")");
257 }
258 }
259
260 void Block::dump_pred(const Block_Array *bbs, Block* orig) const {
261 if (is_connector()) {
262 for (uint i=1; i<num_preds(); i++) {
263 Block *p = ((*bbs)[pred(i)->_idx]);
264 p->dump_pred(bbs, orig);
265 }
266 } else {
267 dump_bidx(orig);
268 tty->print(" ");
269 }
270 }
271
272 void Block::dump_head( const Block_Array *bbs ) const {
273 // Print the basic block
274 dump_bidx(this);
275 tty->print(": #\t");
276
277 // Print the incoming CFG edges and the outgoing CFG edges
278 for( uint i=0; i<_num_succs; i++ ) {
279 non_connector_successor(i)->dump_bidx(_succs[i]);
280 tty->print(" ");
281 }
282 tty->print("<- ");
283 if( head()->is_block_start() ) {
284 for (uint i=1; i<num_preds(); i++) {
285 Node *s = pred(i);
286 if (bbs) {
287 Block *p = (*bbs)[s->_idx];
288 p->dump_pred(bbs, p);
289 } else {
290 while (!s->is_block_start())
291 s = s->in(0);
292 tty->print("N%d ", s->_idx );
293 }
294 }
295 } else
296 tty->print("BLOCK HEAD IS JUNK ");
297
298 // Print loop, if any
299 const Block *bhead = this; // Head of self-loop
300 Node *bh = bhead->head();
301 if( bbs && bh->is_Loop() && !head()->is_Root() ) {
302 LoopNode *loop = bh->as_Loop();
303 const Block *bx = (*bbs)[loop->in(LoopNode::LoopBackControl)->_idx];
304 while (bx->is_connector()) {
305 bx = (*bbs)[bx->pred(1)->_idx];
306 }
307 tty->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order);
308 // Dump any loop-specific bits, especially for CountedLoops.
309 loop->dump_spec(tty);
310 }
311 tty->print(" Freq: %g",_freq);
312 if( Verbose || WizardMode ) {
313 tty->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth);
314 tty->print(" RegPressure: %d",_reg_pressure);
315 tty->print(" IHRP Index: %d",_ihrp_index);
316 tty->print(" FRegPressure: %d",_freg_pressure);
317 tty->print(" FHRP Index: %d",_fhrp_index);
318 }
319 tty->print_cr("");
320 }
321
322 void Block::dump() const { dump(0); }
323
324 void Block::dump( const Block_Array *bbs ) const {
325 dump_head(bbs);
326 uint cnt = _nodes.size();
327 for( uint i=0; i<cnt; i++ )
328 _nodes[i]->dump();
329 tty->print("\n");
330 }
331 #endif
332
333 //=============================================================================
334 //------------------------------PhaseCFG---------------------------------------
335 PhaseCFG::PhaseCFG( Arena *a, RootNode *r, Matcher &m ) :
336 Phase(CFG),
337 _bbs(a),
338 _root(r)
339 #ifndef PRODUCT
340 , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining"))
341 #endif
342 {
343 ResourceMark rm;
344 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode,
345 // then Match it into a machine-specific Node. Then clone the machine
346 // Node on demand.
347 Node *x = new (C, 1) GotoNode(NULL);
348 x->init_req(0, x);
349 _goto = m.match_tree(x);
350 assert(_goto != NULL, "");
351 _goto->set_req(0,_goto);
352
353 // Build the CFG in Reverse Post Order
354 _num_blocks = build_cfg();
355 _broot = _bbs[_root->_idx];
356 }
357
358 //------------------------------build_cfg--------------------------------------
359 // Build a proper looking CFG. Make every block begin with either a StartNode
360 // or a RegionNode. Make every block end with either a Goto, If or Return.
361 // The RootNode both starts and ends it's own block. Do this with a recursive
362 // backwards walk over the control edges.
363 uint PhaseCFG::build_cfg() {
364 Arena *a = Thread::current()->resource_area();
365 VectorSet visited(a);
366
367 // Allocate stack with enough space to avoid frequent realloc
368 Node_Stack nstack(a, C->unique() >> 1);
369 nstack.push(_root, 0);
370 uint sum = 0; // Counter for blocks
371
372 while (nstack.is_nonempty()) {
373 // node and in's index from stack's top
374 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack
375 // only nodes which point to the start of basic block (see below).
376 Node *np = nstack.node();
377 // idx > 0, except for the first node (_root) pushed on stack
378 // at the beginning when idx == 0.
379 // We will use the condition (idx == 0) later to end the build.
380 uint idx = nstack.index();
381 Node *proj = np->in(idx);
382 const Node *x = proj->is_block_proj();
383 // Does the block end with a proper block-ending Node? One of Return,
384 // If or Goto? (This check should be done for visited nodes also).
385 if (x == NULL) { // Does not end right...
386 Node *g = _goto->clone(); // Force it to end in a Goto
387 g->set_req(0, proj);
388 np->set_req(idx, g);
389 x = proj = g;
390 }
391 if (!visited.test_set(x->_idx)) { // Visit this block once
392 // Skip any control-pinned middle'in stuff
393 Node *p = proj;
394 do {
395 proj = p; // Update pointer to last Control
396 p = p->in(0); // Move control forward
397 } while( !p->is_block_proj() &&
398 !p->is_block_start() );
399 // Make the block begin with one of Region or StartNode.
400 if( !p->is_block_start() ) {
401 RegionNode *r = new (C, 2) RegionNode( 2 );
402 r->init_req(1, p); // Insert RegionNode in the way
403 proj->set_req(0, r); // Insert RegionNode in the way
404 p = r;
405 }
406 // 'p' now points to the start of this basic block
407
408 // Put self in array of basic blocks
409 Block *bb = new (_bbs._arena) Block(_bbs._arena,p);
410 _bbs.map(p->_idx,bb);
411 _bbs.map(x->_idx,bb);
412 if( x != p ) // Only for root is x == p
413 bb->_nodes.push((Node*)x);
414
415 // Now handle predecessors
416 ++sum; // Count 1 for self block
417 uint cnt = bb->num_preds();
418 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors
419 Node *prevproj = p->in(i); // Get prior input
420 assert( !prevproj->is_Con(), "dead input not removed" );
421 // Check to see if p->in(i) is a "control-dependent" CFG edge -
422 // i.e., it splits at the source (via an IF or SWITCH) and merges
423 // at the destination (via a many-input Region).
424 // This breaks critical edges. The RegionNode to start the block
425 // will be added when <p,i> is pulled off the node stack
426 if ( cnt > 2 ) { // Merging many things?
427 assert( prevproj== bb->pred(i),"");
428 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge?
429 // Force a block on the control-dependent edge
430 Node *g = _goto->clone(); // Force it to end in a Goto
431 g->set_req(0,prevproj);
432 p->set_req(i,g);
433 }
434 }
435 nstack.push(p, i); // 'p' is RegionNode or StartNode
436 }
437 } else { // Post-processing visited nodes
438 nstack.pop(); // remove node from stack
439 // Check if it the fist node pushed on stack at the beginning.
440 if (idx == 0) break; // end of the build
441 // Find predecessor basic block
442 Block *pb = _bbs[x->_idx];
443 // Insert into nodes array, if not already there
444 if( !_bbs.lookup(proj->_idx) ) {
445 assert( x != proj, "" );
446 // Map basic block of projection
447 _bbs.map(proj->_idx,pb);
448 pb->_nodes.push(proj);
449 }
450 // Insert self as a child of my predecessor block
451 pb->_succs.map(pb->_num_succs++, _bbs[np->_idx]);
452 assert( pb->_nodes[ pb->_nodes.size() - pb->_num_succs ]->is_block_proj(),
453 "too many control users, not a CFG?" );
454 }
455 }
456 // Return number of basic blocks for all children and self
457 return sum;
458 }
459
460 //------------------------------insert_goto_at---------------------------------
461 // Inserts a goto & corresponding basic block between
462 // block[block_no] and its succ_no'th successor block
463 void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) {
464 // get block with block_no
465 assert(block_no < _num_blocks, "illegal block number");
466 Block* in = _blocks[block_no];
467 // get successor block succ_no
468 assert(succ_no < in->_num_succs, "illegal successor number");
469 Block* out = in->_succs[succ_no];
470 // get ProjNode corresponding to the succ_no'th successor of the in block
471 ProjNode* proj = in->_nodes[in->_nodes.size() - in->_num_succs + succ_no]->as_Proj();
472 // create region for basic block
473 RegionNode* region = new (C, 2) RegionNode(2);
474 region->init_req(1, proj);
475 // setup corresponding basic block
476 Block* block = new (_bbs._arena) Block(_bbs._arena, region);
477 _bbs.map(region->_idx, block);
478 C->regalloc()->set_bad(region->_idx);
479 // add a goto node
480 Node* gto = _goto->clone(); // get a new goto node
481 gto->set_req(0, region);
482 // add it to the basic block
483 block->_nodes.push(gto);
484 _bbs.map(gto->_idx, block);
485 C->regalloc()->set_bad(gto->_idx);
486 // hook up successor block
487 block->_succs.map(block->_num_succs++, out);
488 // remap successor's predecessors if necessary
489 for (uint i = 1; i < out->num_preds(); i++) {
490 if (out->pred(i) == proj) out->head()->set_req(i, gto);
491 }
492 // remap predecessor's successor to new block
493 in->_succs.map(succ_no, block);
494 // add new basic block to basic block list
495 _blocks.insert(block_no + 1, block);
496 _num_blocks++;
497 }
498
499 //------------------------------no_flip_branch---------------------------------
500 // Does this block end in a multiway branch that cannot have the default case
501 // flipped for another case?
502 static bool no_flip_branch( Block *b ) {
503 int branch_idx = b->_nodes.size() - b->_num_succs-1;
504 if( branch_idx < 1 ) return false;
505 Node *bra = b->_nodes[branch_idx];
506 if( bra->is_Catch() ) return true;
507 if( bra->is_Mach() ) {
508 if( bra->is_MachNullCheck() ) return true;
509 int iop = bra->as_Mach()->ideal_Opcode();
510 if( iop == Op_FastLock || iop == Op_FastUnlock )
511 return true;
512 }
513 return false;
514 }
515
516 //------------------------------convert_NeverBranch_to_Goto--------------------
517 // Check for NeverBranch at block end. This needs to become a GOTO to the
518 // true target. NeverBranch are treated as a conditional branch that always
519 // goes the same direction for most of the optimizer and are used to give a
520 // fake exit path to infinite loops. At this late stage they need to turn
521 // into Goto's so that when you enter the infinite loop you indeed hang.
522 void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) {
523 // Find true target
524 int end_idx = b->end_idx();
525 int idx = b->_nodes[end_idx+1]->as_Proj()->_con;
526 Block *succ = b->_succs[idx];
527 Node* gto = _goto->clone(); // get a new goto node
528 gto->set_req(0, b->head());
529 Node *bp = b->_nodes[end_idx];
530 b->_nodes.map(end_idx,gto); // Slam over NeverBranch
531 _bbs.map(gto->_idx, b);
532 C->regalloc()->set_bad(gto->_idx);
533 b->_nodes.pop(); // Yank projections
534 b->_nodes.pop(); // Yank projections
535 b->_succs.map(0,succ); // Map only successor
536 b->_num_succs = 1;
537 // remap successor's predecessors if necessary
538 uint j;
539 for( j = 1; j < succ->num_preds(); j++)
540 if( succ->pred(j)->in(0) == bp )
541 succ->head()->set_req(j, gto);
542 // Kill alternate exit path
543 Block *dead = b->_succs[1-idx];
544 for( j = 1; j < dead->num_preds(); j++)
545 if( dead->pred(j)->in(0) == bp )
546 break;
547 // Scan through block, yanking dead path from
548 // all regions and phis.
549 dead->head()->del_req(j);
550 for( int k = 1; dead->_nodes[k]->is_Phi(); k++ )
551 dead->_nodes[k]->del_req(j);
552 }
553
554 //------------------------------MoveToNext-------------------------------------
555 // Helper function to move block bx to the slot following b_index. Return
556 // true if the move is successful, otherwise false
557 bool PhaseCFG::MoveToNext(Block* bx, uint b_index) {
558 if (bx == NULL) return false;
559
560 // Return false if bx is already scheduled.
561 uint bx_index = bx->_pre_order;
562 if ((bx_index <= b_index) && (_blocks[bx_index] == bx)) {
563 return false;
564 }
565
566 // Find the current index of block bx on the block list
567 bx_index = b_index + 1;
568 while( bx_index < _num_blocks && _blocks[bx_index] != bx ) bx_index++;
569 assert(_blocks[bx_index] == bx, "block not found");
570
571 // If the previous block conditionally falls into bx, return false,
572 // because moving bx will create an extra jump.
573 for(uint k = 1; k < bx->num_preds(); k++ ) {
574 Block* pred = _bbs[bx->pred(k)->_idx];
575 if (pred == _blocks[bx_index-1]) {
576 if (pred->_num_succs != 1) {
577 return false;
578 }
579 }
580 }
581
582 // Reinsert bx just past block 'b'
583 _blocks.remove(bx_index);
584 _blocks.insert(b_index + 1, bx);
585 return true;
586 }
587
588 //------------------------------MoveToEnd--------------------------------------
589 // Move empty and uncommon blocks to the end.
590 void PhaseCFG::MoveToEnd(Block *b, uint i) {
591 int e = b->is_Empty();
592 if (e != Block::not_empty) {
593 if (e == Block::empty_with_goto) {
594 // Remove the goto, but leave the block.
595 b->_nodes.pop();
596 }
597 // Mark this block as a connector block, which will cause it to be
598 // ignored in certain functions such as non_connector_successor().
599 b->set_connector();
600 }
601 // Move the empty block to the end, and don't recheck.
602 _blocks.remove(i);
603 _blocks.push(b);
604 }
605
606 //------------------------------RemoveEmpty------------------------------------
607 // Remove empty basic blocks and useless branches.
608 void PhaseCFG::RemoveEmpty() {
609 // Move uncommon blocks to the end
610 uint last = _num_blocks;
611 uint i;
612 assert( _blocks[0] == _broot, "" );
613 for( i = 1; i < last; i++ ) {
614 Block *b = _blocks[i];
615
616 // Check for NeverBranch at block end. This needs to become a GOTO to the
617 // true target. NeverBranch are treated as a conditional branch that
618 // always goes the same direction for most of the optimizer and are used
619 // to give a fake exit path to infinite loops. At this late stage they
620 // need to turn into Goto's so that when you enter the infinite loop you
621 // indeed hang.
622 if( b->_nodes[b->end_idx()]->Opcode() == Op_NeverBranch )
623 convert_NeverBranch_to_Goto(b);
624
625 // Look for uncommon blocks and move to end.
626 if( b->is_uncommon(_bbs) ) {
627 MoveToEnd(b, i);
628 last--; // No longer check for being uncommon!
629 if( no_flip_branch(b) ) { // Fall-thru case must follow?
630 b = _blocks[i]; // Find the fall-thru block
631 MoveToEnd(b, i);
632 last--;
633 }
634 i--; // backup block counter post-increment
635 }
636 }
637
638 // Remove empty blocks
639 uint j1;
640 last = _num_blocks;
641 for( i=0; i < last; i++ ) {
642 Block *b = _blocks[i];
643 if (i > 0) {
644 if (b->is_Empty() != Block::not_empty) {
645 MoveToEnd(b, i);
646 last--;
647 i--;
648 }
649 }
650 } // End of for all blocks
651
652 // Fixup final control flow for the blocks. Remove jump-to-next
653 // block. If neither arm of a IF follows the conditional branch, we
654 // have to add a second jump after the conditional. We place the
655 // TRUE branch target in succs[0] for both GOTOs and IFs.
656 for( i=0; i < _num_blocks; i++ ) {
657 Block *b = _blocks[i];
658 b->_pre_order = i; // turn pre-order into block-index
659
660 // Connector blocks need no further processing.
661 if (b->is_connector()) {
662 assert((i+1) == _num_blocks || _blocks[i+1]->is_connector(),
663 "All connector blocks should sink to the end");
664 continue;
665 }
666 assert(b->is_Empty() != Block::completely_empty,
667 "Empty blocks should be connectors");
668
669 Block *bnext = (i < _num_blocks-1) ? _blocks[i+1] : NULL;
670 Block *bs0 = b->non_connector_successor(0);
671
672 // Check for multi-way branches where I cannot negate the test to
673 // exchange the true and false targets.
674 if( no_flip_branch( b ) ) {
675 // Find fall through case - if must fall into its target
676 int branch_idx = b->_nodes.size() - b->_num_succs;
677 for (uint j2 = 0; j2 < b->_num_succs; j2++) {
678 const ProjNode* p = b->_nodes[branch_idx + j2]->as_Proj();
679 if (p->_con == 0) {
680 // successor j2 is fall through case
681 if (b->non_connector_successor(j2) != bnext) {
682 // but it is not the next block => insert a goto
683 insert_goto_at(i, j2);
684 }
685 // Put taken branch in slot 0
686 if( j2 == 0 && b->_num_succs == 2) {
687 // Flip targets in succs map
688 Block *tbs0 = b->_succs[0];
689 Block *tbs1 = b->_succs[1];
690 b->_succs.map( 0, tbs1 );
691 b->_succs.map( 1, tbs0 );
692 }
693 break;
694 }
695 }
696 // Remove all CatchProjs
697 for (j1 = 0; j1 < b->_num_succs; j1++) b->_nodes.pop();
698
699 } else if (b->_num_succs == 1) {
700 // Block ends in a Goto?
701 if (bnext == bs0) {
702 // We fall into next block; remove the Goto
703 b->_nodes.pop();
704 }
705
706 } else if( b->_num_succs == 2 ) { // Block ends in a If?
707 // Get opcode of 1st projection (matches _succs[0])
708 // Note: Since this basic block has 2 exits, the last 2 nodes must
709 // be projections (in any order), the 3rd last node must be
710 // the IfNode (we have excluded other 2-way exits such as
711 // CatchNodes already).
712 MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach();
713 ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj();
714 ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj();
715
716 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
717 assert(proj0->raw_out(0) == b->_succs[0]->head(), "Mismatch successor 0");
718 assert(proj1->raw_out(0) == b->_succs[1]->head(), "Mismatch successor 1");
719
720 Block *bs1 = b->non_connector_successor(1);
721
722 // Check for neither successor block following the current
723 // block ending in a conditional. If so, move one of the
724 // successors after the current one, provided that the
725 // successor was previously unscheduled, but moveable
726 // (i.e., all paths to it involve a branch).
727 if( bnext != bs0 && bnext != bs1 ) {
728
729 // Choose the more common successor based on the probability
730 // of the conditional branch.
731 Block *bx = bs0;
732 Block *by = bs1;
733
734 // _prob is the probability of taking the true path. Make
735 // p the probability of taking successor #1.
736 float p = iff->as_MachIf()->_prob;
737 if( proj0->Opcode() == Op_IfTrue ) {
738 p = 1.0 - p;
739 }
740
741 // Prefer successor #1 if p > 0.5
742 if (p > PROB_FAIR) {
743 bx = bs1;
744 by = bs0;
745 }
746
747 // Attempt the more common successor first
748 if (MoveToNext(bx, i)) {
749 bnext = bx;
750 } else if (MoveToNext(by, i)) {
751 bnext = by;
752 }
753 }
754
755 // Check for conditional branching the wrong way. Negate
756 // conditional, if needed, so it falls into the following block
757 // and branches to the not-following block.
758
759 // Check for the next block being in succs[0]. We are going to branch
760 // to succs[0], so we want the fall-thru case as the next block in
761 // succs[1].
762 if (bnext == bs0) {
763 // Fall-thru case in succs[0], so flip targets in succs map
764 Block *tbs0 = b->_succs[0];
765 Block *tbs1 = b->_succs[1];
766 b->_succs.map( 0, tbs1 );
767 b->_succs.map( 1, tbs0 );
768 // Flip projection for each target
769 { ProjNode *tmp = proj0; proj0 = proj1; proj1 = tmp; }
770
771 } else if( bnext == bs1 ) { // Fall-thru is already in succs[1]
772
773 } else { // Else need a double-branch
774
775 // The existing conditional branch need not change.
776 // Add a unconditional branch to the false target.
777 // Alas, it must appear in its own block and adding a
778 // block this late in the game is complicated. Sigh.
779 insert_goto_at(i, 1);
780 }
781
782 // Make sure we TRUE branch to the target
783 if( proj0->Opcode() == Op_IfFalse )
784 iff->negate();
785
786 b->_nodes.pop(); // Remove IfFalse & IfTrue projections
787 b->_nodes.pop();
788
789 } else {
790 // Multi-exit block, e.g. a switch statement
791 // But we don't need to do anything here
792 }
793
794 } // End of for all blocks
795
796 }
797
798
799 //------------------------------dump-------------------------------------------
800 #ifndef PRODUCT
801 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const {
802 const Node *x = end->is_block_proj();
803 assert( x, "not a CFG" );
804
805 // Do not visit this block again
806 if( visited.test_set(x->_idx) ) return;
807
808 // Skip through this block
809 const Node *p = x;
810 do {
811 p = p->in(0); // Move control forward
812 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
813 } while( !p->is_block_start() );
814
815 // Recursively visit
816 for( uint i=1; i<p->req(); i++ )
817 _dump_cfg(p->in(i),visited);
818
819 // Dump the block
820 _bbs[p->_idx]->dump(&_bbs);
821 }
822
823 void PhaseCFG::dump( ) const {
824 tty->print("\n--- CFG --- %d BBs\n",_num_blocks);
825 if( _blocks.size() ) { // Did we do basic-block layout?
826 for( uint i=0; i<_num_blocks; i++ )
827 _blocks[i]->dump(&_bbs);
828 } else { // Else do it with a DFS
829 VectorSet visited(_bbs._arena);
830 _dump_cfg(_root,visited);
831 }
832 }
833
834 void PhaseCFG::dump_headers() {
835 for( uint i = 0; i < _num_blocks; i++ ) {
836 if( _blocks[i] == NULL ) continue;
837 _blocks[i]->dump_head(&_bbs);
838 }
839 }
840
841 void PhaseCFG::verify( ) const {
842 // Verify sane CFG
843 for( uint i = 0; i < _num_blocks; i++ ) {
844 Block *b = _blocks[i];
845 uint cnt = b->_nodes.size();
846 uint j;
847 for( j = 0; j < cnt; j++ ) {
848 Node *n = b->_nodes[j];
849 assert( _bbs[n->_idx] == b, "" );
850 if( j >= 1 && n->is_Mach() &&
851 n->as_Mach()->ideal_Opcode() == Op_CreateEx ) {
852 assert( j == 1 || b->_nodes[j-1]->is_Phi(),
853 "CreateEx must be first instruction in block" );
854 }
855 for( uint k = 0; k < n->req(); k++ ) {
856 Node *use = n->in(k);
857 if( use && use != n ) {
858 assert( _bbs[use->_idx] || use->is_Con(),
859 "must have block; constants for debug info ok" );
860 }
861 }
862 }
863
864 j = b->end_idx();
865 Node *bp = (Node*)b->_nodes[b->_nodes.size()-1]->is_block_proj();
866 assert( bp, "last instruction must be a block proj" );
867 assert( bp == b->_nodes[j], "wrong number of successors for this block" );
868 if( bp->is_Catch() ) {
869 while( b->_nodes[--j]->Opcode() == Op_MachProj ) ;
870 assert( b->_nodes[j]->is_Call(), "CatchProj must follow call" );
871 }
872 else if( bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If ) {
873 assert( b->_num_succs == 2, "Conditional branch must have two targets");
874 }
875 }
876 }
877 #endif
878
879 //=============================================================================
880 //------------------------------UnionFind--------------------------------------
881 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) {
882 Copy::zero_to_bytes( _indices, sizeof(uint)*max );
883 }
884
885 void UnionFind::extend( uint from_idx, uint to_idx ) {
886 _nesting.check();
887 if( from_idx >= _max ) {
888 uint size = 16;
889 while( size <= from_idx ) size <<=1;
890 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size );
891 _max = size;
892 }
893 while( _cnt <= from_idx ) _indices[_cnt++] = 0;
894 _indices[from_idx] = to_idx;
895 }
896
897 void UnionFind::reset( uint max ) {
898 assert( max <= max_uint, "Must fit within uint" );
899 // Force the Union-Find mapping to be at least this large
900 extend(max,0);
901 // Initialize to be the ID mapping.
902 for( uint i=0; i<_max; i++ ) map(i,i);
903 }
904
905 //------------------------------Find_compress----------------------------------
906 // Straight out of Tarjan's union-find algorithm
907 uint UnionFind::Find_compress( uint idx ) {
908 uint cur = idx;
909 uint next = lookup(cur);
910 while( next != cur ) { // Scan chain of equivalences
911 assert( next < cur, "always union smaller" );
912 cur = next; // until find a fixed-point
913 next = lookup(cur);
914 }
915 // Core of union-find algorithm: update chain of
916 // equivalences to be equal to the root.
917 while( idx != next ) {
918 uint tmp = lookup(idx);
919 map(idx, next);
920 idx = tmp;
921 }
922 return idx;
923 }
924
925 //------------------------------Find_const-------------------------------------
926 // Like Find above, but no path compress, so bad asymptotic behavior
927 uint UnionFind::Find_const( uint idx ) const {
928 if( idx == 0 ) return idx; // Ignore the zero idx
929 // Off the end? This can happen during debugging dumps
930 // when data structures have not finished being updated.
931 if( idx >= _max ) return idx;
932 uint next = lookup(idx);
933 while( next != idx ) { // Scan chain of equivalences
934 assert( next < idx, "always union smaller" );
935 idx = next; // until find a fixed-point
936 next = lookup(idx);
937 }
938 return next;
939 }
940
941 //------------------------------Union------------------------------------------
942 // union 2 sets together.
943 void UnionFind::Union( uint idx1, uint idx2 ) {
944 uint src = Find(idx1);
945 uint dst = Find(idx2);
946 assert( src, "" );
947 assert( dst, "" );
948 assert( src < _max, "oob" );
949 assert( dst < _max, "oob" );
950 assert( src < dst, "always union smaller" );
951 map(dst,src);
952 }