1 /*
2 * Copyright (c) 1997, 2010, 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.
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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
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23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/block.hpp"
28 #include "opto/cfgnode.hpp"
29 #include "opto/chaitin.hpp"
30 #include "opto/coalesce.hpp"
31 #include "opto/connode.hpp"
32 #include "opto/indexSet.hpp"
33 #include "opto/machnode.hpp"
34 #include "opto/matcher.hpp"
35 #include "opto/regmask.hpp"
36
37 //=============================================================================
38 //------------------------------reset_uf_map-----------------------------------
39 void PhaseChaitin::reset_uf_map( uint maxlrg ) {
40 _maxlrg = maxlrg;
41 // Force the Union-Find mapping to be at least this large
42 _uf_map.extend(_maxlrg,0);
43 // Initialize it to be the ID mapping.
44 for( uint i=0; i<_maxlrg; i++ )
45 _uf_map.map(i,i);
46 }
47
48 //------------------------------compress_uf_map--------------------------------
49 // Make all Nodes map directly to their final live range; no need for
50 // the Union-Find mapping after this call.
51 void PhaseChaitin::compress_uf_map_for_nodes( ) {
52 // For all Nodes, compress mapping
53 uint unique = _names.Size();
54 for( uint i=0; i<unique; i++ ) {
55 uint lrg = _names[i];
56 uint compressed_lrg = Find(lrg);
57 if( lrg != compressed_lrg )
58 _names.map(i,compressed_lrg);
59 }
60 }
61
62 //------------------------------Find-------------------------------------------
63 // Straight out of Tarjan's union-find algorithm
64 uint PhaseChaitin::Find_compress( uint lrg ) {
65 uint cur = lrg;
66 uint next = _uf_map[cur];
67 while( next != cur ) { // Scan chain of equivalences
68 assert( next < cur, "always union smaller" );
69 cur = next; // until find a fixed-point
70 next = _uf_map[cur];
71 }
72 // Core of union-find algorithm: update chain of
73 // equivalences to be equal to the root.
74 while( lrg != next ) {
75 uint tmp = _uf_map[lrg];
76 _uf_map.map(lrg, next);
77 lrg = tmp;
78 }
79 return lrg;
80 }
81
82 //------------------------------Find-------------------------------------------
83 // Straight out of Tarjan's union-find algorithm
84 uint PhaseChaitin::Find_compress( const Node *n ) {
85 uint lrg = Find_compress(_names[n->_idx]);
86 _names.map(n->_idx,lrg);
87 return lrg;
88 }
89
90 //------------------------------Find_const-------------------------------------
91 // Like Find above, but no path compress, so bad asymptotic behavior
92 uint PhaseChaitin::Find_const( uint lrg ) const {
93 if( !lrg ) return lrg; // Ignore the zero LRG
94 // Off the end? This happens during debugging dumps when you got
95 // brand new live ranges but have not told the allocator yet.
96 if( lrg >= _maxlrg ) return lrg;
97 uint next = _uf_map[lrg];
98 while( next != lrg ) { // Scan chain of equivalences
99 assert( next < lrg, "always union smaller" );
100 lrg = next; // until find a fixed-point
101 next = _uf_map[lrg];
102 }
103 return next;
104 }
105
106 //------------------------------Find-------------------------------------------
107 // Like Find above, but no path compress, so bad asymptotic behavior
108 uint PhaseChaitin::Find_const( const Node *n ) const {
109 if( n->_idx >= _names.Size() ) return 0; // not mapped, usual for debug dump
110 return Find_const( _names[n->_idx] );
111 }
112
113 //------------------------------Union------------------------------------------
114 // union 2 sets together.
115 void PhaseChaitin::Union( const Node *src_n, const Node *dst_n ) {
116 uint src = Find(src_n);
117 uint dst = Find(dst_n);
118 assert( src, "" );
119 assert( dst, "" );
120 assert( src < _maxlrg, "oob" );
121 assert( dst < _maxlrg, "oob" );
122 assert( src < dst, "always union smaller" );
123 _uf_map.map(dst,src);
124 }
125
126 //------------------------------new_lrg----------------------------------------
127 void PhaseChaitin::new_lrg( const Node *x, uint lrg ) {
128 // Make the Node->LRG mapping
129 _names.extend(x->_idx,lrg);
130 // Make the Union-Find mapping an identity function
131 _uf_map.extend(lrg,lrg);
132 }
133
134 //------------------------------clone_projs------------------------------------
135 // After cloning some rematerialized instruction, clone any MachProj's that
136 // follow it. Example: Intel zero is XOR, kills flags. Sparc FP constants
137 // use G3 as an address temp.
138 int PhaseChaitin::clone_projs( Block *b, uint idx, Node *con, Node *copy, uint &maxlrg ) {
139 Block *bcon = _cfg._bbs[con->_idx];
140 uint cindex = bcon->find_node(con);
141 Node *con_next = bcon->_nodes[cindex+1];
142 if( con_next->in(0) != con || con_next->Opcode() != Op_MachProj )
143 return false; // No MachProj's follow
144
145 // Copy kills after the cloned constant
146 Node *kills = con_next->clone();
147 kills->set_req( 0, copy );
148 b->_nodes.insert( idx, kills );
149 _cfg._bbs.map( kills->_idx, b );
150 new_lrg( kills, maxlrg++ );
151 return true;
152 }
153
154 //------------------------------compact----------------------------------------
155 // Renumber the live ranges to compact them. Makes the IFG smaller.
156 void PhaseChaitin::compact() {
157 // Current the _uf_map contains a series of short chains which are headed
158 // by a self-cycle. All the chains run from big numbers to little numbers.
159 // The Find() call chases the chains & shortens them for the next Find call.
160 // We are going to change this structure slightly. Numbers above a moving
161 // wave 'i' are unchanged. Numbers below 'j' point directly to their
162 // compacted live range with no further chaining. There are no chains or
163 // cycles below 'i', so the Find call no longer works.
164 uint j=1;
165 uint i;
166 for( i=1; i < _maxlrg; i++ ) {
167 uint lr = _uf_map[i];
168 // Ignore unallocated live ranges
169 if( !lr ) continue;
170 assert( lr <= i, "" );
171 _uf_map.map(i, ( lr == i ) ? j++ : _uf_map[lr]);
172 }
173 if( false ) // PrintOptoCompactLiveRanges
174 printf("Compacted %d LRs from %d\n",i-j,i);
175 // Now change the Node->LR mapping to reflect the compacted names
176 uint unique = _names.Size();
177 for( i=0; i<unique; i++ )
178 _names.map(i,_uf_map[_names[i]]);
179
180 // Reset the Union-Find mapping
181 reset_uf_map(j);
182
183 }
184
185 //=============================================================================
186 //------------------------------Dump-------------------------------------------
187 #ifndef PRODUCT
188 void PhaseCoalesce::dump( Node *n ) const {
189 // Being a const function means I cannot use 'Find'
190 uint r = _phc.Find(n);
191 tty->print("L%d/N%d ",r,n->_idx);
192 }
193
194 //------------------------------dump-------------------------------------------
195 void PhaseCoalesce::dump() const {
196 // I know I have a block layout now, so I can print blocks in a loop
197 for( uint i=0; i<_phc._cfg._num_blocks; i++ ) {
198 uint j;
199 Block *b = _phc._cfg._blocks[i];
200 // Print a nice block header
201 tty->print("B%d: ",b->_pre_order);
202 for( j=1; j<b->num_preds(); j++ )
203 tty->print("B%d ", _phc._cfg._bbs[b->pred(j)->_idx]->_pre_order);
204 tty->print("-> ");
205 for( j=0; j<b->_num_succs; j++ )
206 tty->print("B%d ",b->_succs[j]->_pre_order);
207 tty->print(" IDom: B%d/#%d\n", b->_idom ? b->_idom->_pre_order : 0, b->_dom_depth);
208 uint cnt = b->_nodes.size();
209 for( j=0; j<cnt; j++ ) {
210 Node *n = b->_nodes[j];
211 dump( n );
212 tty->print("\t%s\t",n->Name());
213
214 // Dump the inputs
215 uint k; // Exit value of loop
216 for( k=0; k<n->req(); k++ ) // For all required inputs
217 if( n->in(k) ) dump( n->in(k) );
218 else tty->print("_ ");
219 int any_prec = 0;
220 for( ; k<n->len(); k++ ) // For all precedence inputs
221 if( n->in(k) ) {
222 if( !any_prec++ ) tty->print(" |");
223 dump( n->in(k) );
224 }
225
226 // Dump node-specific info
227 n->dump_spec(tty);
228 tty->print("\n");
229
230 }
231 tty->print("\n");
232 }
233 }
234 #endif
235
236 //------------------------------combine_these_two------------------------------
237 // Combine the live ranges def'd by these 2 Nodes. N2 is an input to N1.
238 void PhaseCoalesce::combine_these_two( Node *n1, Node *n2 ) {
239 uint lr1 = _phc.Find(n1);
240 uint lr2 = _phc.Find(n2);
241 if( lr1 != lr2 && // Different live ranges already AND
242 !_phc._ifg->test_edge_sq( lr1, lr2 ) ) { // Do not interfere
243 LRG *lrg1 = &_phc.lrgs(lr1);
244 LRG *lrg2 = &_phc.lrgs(lr2);
245 // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
246
247 // Now, why is int->oop OK? We end up declaring a raw-pointer as an oop
248 // and in general that's a bad thing. However, int->oop conversions only
249 // happen at GC points, so the lifetime of the misclassified raw-pointer
250 // is from the CheckCastPP (that converts it to an oop) backwards up
251 // through a merge point and into the slow-path call, and around the
252 // diamond up to the heap-top check and back down into the slow-path call.
253 // The misclassified raw pointer is NOT live across the slow-path call,
254 // and so does not appear in any GC info, so the fact that it is
255 // misclassified is OK.
256
257 if( (lrg1->_is_oop || !lrg2->_is_oop) && // not an oop->int cast AND
258 // Compatible final mask
259 lrg1->mask().overlap( lrg2->mask() ) ) {
260 // Merge larger into smaller.
261 if( lr1 > lr2 ) {
262 uint tmp = lr1; lr1 = lr2; lr2 = tmp;
263 Node *n = n1; n1 = n2; n2 = n;
264 LRG *ltmp = lrg1; lrg1 = lrg2; lrg2 = ltmp;
265 }
266 // Union lr2 into lr1
267 _phc.Union( n1, n2 );
268 if (lrg1->_maxfreq < lrg2->_maxfreq)
269 lrg1->_maxfreq = lrg2->_maxfreq;
270 // Merge in the IFG
271 _phc._ifg->Union( lr1, lr2 );
272 // Combine register restrictions
273 lrg1->AND(lrg2->mask());
274 }
275 }
276 }
277
278 //------------------------------coalesce_driver--------------------------------
279 // Copy coalescing
280 void PhaseCoalesce::coalesce_driver( ) {
281
282 verify();
283 // Coalesce from high frequency to low
284 for( uint i=0; i<_phc._cfg._num_blocks; i++ )
285 coalesce( _phc._blks[i] );
286
287 }
288
289 //------------------------------insert_copy_with_overlap-----------------------
290 // I am inserting copies to come out of SSA form. In the general case, I am
291 // doing a parallel renaming. I'm in the Named world now, so I can't do a
292 // general parallel renaming. All the copies now use "names" (live-ranges)
293 // to carry values instead of the explicit use-def chains. Suppose I need to
294 // insert 2 copies into the same block. They copy L161->L128 and L128->L132.
295 // If I insert them in the wrong order then L128 will get clobbered before it
296 // can get used by the second copy. This cannot happen in the SSA model;
297 // direct use-def chains get me the right value. It DOES happen in the named
298 // model so I have to handle the reordering of copies.
299 //
300 // In general, I need to topo-sort the placed copies to avoid conflicts.
301 // Its possible to have a closed cycle of copies (e.g., recirculating the same
302 // values around a loop). In this case I need a temp to break the cycle.
303 void PhaseAggressiveCoalesce::insert_copy_with_overlap( Block *b, Node *copy, uint dst_name, uint src_name ) {
304
305 // Scan backwards for the locations of the last use of the dst_name.
306 // I am about to clobber the dst_name, so the copy must be inserted
307 // after the last use. Last use is really first-use on a backwards scan.
308 uint i = b->end_idx()-1;
309 while( 1 ) {
310 Node *n = b->_nodes[i];
311 // Check for end of virtual copies; this is also the end of the
312 // parallel renaming effort.
313 if( n->_idx < _unique ) break;
314 uint idx = n->is_Copy();
315 assert( idx || n->is_Con() || n->Opcode() == Op_MachProj, "Only copies during parallel renaming" );
316 if( idx && _phc.Find(n->in(idx)) == dst_name ) break;
317 i--;
318 }
319 uint last_use_idx = i;
320
321 // Also search for any kill of src_name that exits the block.
322 // Since the copy uses src_name, I have to come before any kill.
323 uint kill_src_idx = b->end_idx();
324 // There can be only 1 kill that exits any block and that is
325 // the last kill. Thus it is the first kill on a backwards scan.
326 i = b->end_idx()-1;
327 while( 1 ) {
328 Node *n = b->_nodes[i];
329 // Check for end of virtual copies; this is also the end of the
330 // parallel renaming effort.
331 if( n->_idx < _unique ) break;
332 assert( n->is_Copy() || n->is_Con() || n->Opcode() == Op_MachProj, "Only copies during parallel renaming" );
333 if( _phc.Find(n) == src_name ) {
334 kill_src_idx = i;
335 break;
336 }
337 i--;
338 }
339 // Need a temp? Last use of dst comes after the kill of src?
340 if( last_use_idx >= kill_src_idx ) {
341 // Need to break a cycle with a temp
342 uint idx = copy->is_Copy();
343 Node *tmp = copy->clone();
344 _phc.new_lrg(tmp,_phc._maxlrg++);
345 // Insert new temp between copy and source
346 tmp ->set_req(idx,copy->in(idx));
347 copy->set_req(idx,tmp);
348 // Save source in temp early, before source is killed
349 b->_nodes.insert(kill_src_idx,tmp);
350 _phc._cfg._bbs.map( tmp->_idx, b );
351 last_use_idx++;
352 }
353
354 // Insert just after last use
355 b->_nodes.insert(last_use_idx+1,copy);
356 }
357
358 //------------------------------insert_copies----------------------------------
359 void PhaseAggressiveCoalesce::insert_copies( Matcher &matcher ) {
360 // We do LRGs compressing and fix a liveout data only here since the other
361 // place in Split() is guarded by the assert which we never hit.
362 _phc.compress_uf_map_for_nodes();
363 // Fix block's liveout data for compressed live ranges.
364 for(uint lrg = 1; lrg < _phc._maxlrg; lrg++ ) {
365 uint compressed_lrg = _phc.Find(lrg);
366 if( lrg != compressed_lrg ) {
367 for( uint bidx = 0; bidx < _phc._cfg._num_blocks; bidx++ ) {
368 IndexSet *liveout = _phc._live->live(_phc._cfg._blocks[bidx]);
369 if( liveout->member(lrg) ) {
370 liveout->remove(lrg);
371 liveout->insert(compressed_lrg);
372 }
373 }
374 }
375 }
376
377 // All new nodes added are actual copies to replace virtual copies.
378 // Nodes with index less than '_unique' are original, non-virtual Nodes.
379 _unique = C->unique();
380
381 for( uint i=0; i<_phc._cfg._num_blocks; i++ ) {
382 Block *b = _phc._cfg._blocks[i];
383 uint cnt = b->num_preds(); // Number of inputs to the Phi
384
385 for( uint l = 1; l<b->_nodes.size(); l++ ) {
386 Node *n = b->_nodes[l];
387
388 // Do not use removed-copies, use copied value instead
389 uint ncnt = n->req();
390 for( uint k = 1; k<ncnt; k++ ) {
391 Node *copy = n->in(k);
392 uint cidx = copy->is_Copy();
393 if( cidx ) {
394 Node *def = copy->in(cidx);
395 if( _phc.Find(copy) == _phc.Find(def) )
396 n->set_req(k,def);
397 }
398 }
399
400 // Remove any explicit copies that get coalesced.
401 uint cidx = n->is_Copy();
402 if( cidx ) {
403 Node *def = n->in(cidx);
404 if( _phc.Find(n) == _phc.Find(def) ) {
405 n->replace_by(def);
406 n->set_req(cidx,NULL);
407 b->_nodes.remove(l);
408 l--;
409 continue;
410 }
411 }
412
413 if( n->is_Phi() ) {
414 // Get the chosen name for the Phi
415 uint phi_name = _phc.Find( n );
416 // Ignore the pre-allocated specials
417 if( !phi_name ) continue;
418 // Check for mismatch inputs to Phi
419 for( uint j = 1; j<cnt; j++ ) {
420 Node *m = n->in(j);
421 uint src_name = _phc.Find(m);
422 if( src_name != phi_name ) {
423 Block *pred = _phc._cfg._bbs[b->pred(j)->_idx];
424 Node *copy;
425 assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
426 // Rematerialize constants instead of copying them
427 if( m->is_Mach() && m->as_Mach()->is_Con() &&
428 m->as_Mach()->rematerialize() ) {
429 copy = m->clone();
430 // Insert the copy in the predecessor basic block
431 pred->add_inst(copy);
432 // Copy any flags as well
433 _phc.clone_projs( pred, pred->end_idx(), m, copy, _phc._maxlrg );
434 } else {
435 const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
436 copy = new (C) MachSpillCopyNode(m,*rm,*rm);
437 // Find a good place to insert. Kinda tricky, use a subroutine
438 insert_copy_with_overlap(pred,copy,phi_name,src_name);
439 }
440 // Insert the copy in the use-def chain
441 n->set_req( j, copy );
442 _phc._cfg._bbs.map( copy->_idx, pred );
443 // Extend ("register allocate") the names array for the copy.
444 _phc._names.extend( copy->_idx, phi_name );
445 } // End of if Phi names do not match
446 } // End of for all inputs to Phi
447 } else { // End of if Phi
448
449 // Now check for 2-address instructions
450 uint idx;
451 if( n->is_Mach() && (idx=n->as_Mach()->two_adr()) ) {
452 // Get the chosen name for the Node
453 uint name = _phc.Find( n );
454 assert( name, "no 2-address specials" );
455 // Check for name mis-match on the 2-address input
456 Node *m = n->in(idx);
457 if( _phc.Find(m) != name ) {
458 Node *copy;
459 assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
460 // At this point it is unsafe to extend live ranges (6550579).
461 // Rematerialize only constants as we do for Phi above.
462 if( m->is_Mach() && m->as_Mach()->is_Con() &&
463 m->as_Mach()->rematerialize() ) {
464 copy = m->clone();
465 // Insert the copy in the basic block, just before us
466 b->_nodes.insert( l++, copy );
467 if( _phc.clone_projs( b, l, m, copy, _phc._maxlrg ) )
468 l++;
469 } else {
470 const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
471 copy = new (C) MachSpillCopyNode( m, *rm, *rm );
472 // Insert the copy in the basic block, just before us
473 b->_nodes.insert( l++, copy );
474 }
475 // Insert the copy in the use-def chain
476 n->set_req(idx, copy );
477 // Extend ("register allocate") the names array for the copy.
478 _phc._names.extend( copy->_idx, name );
479 _phc._cfg._bbs.map( copy->_idx, b );
480 }
481
482 } // End of is two-adr
483
484 // Insert a copy at a debug use for a lrg which has high frequency
485 if( b->_freq < OPTO_DEBUG_SPLIT_FREQ || b->is_uncommon(_phc._cfg._bbs) ) {
486 // Walk the debug inputs to the node and check for lrg freq
487 JVMState* jvms = n->jvms();
488 uint debug_start = jvms ? jvms->debug_start() : 999999;
489 uint debug_end = jvms ? jvms->debug_end() : 999999;
490 for(uint inpidx = debug_start; inpidx < debug_end; inpidx++) {
491 // Do not split monitors; they are only needed for debug table
492 // entries and need no code.
493 if( jvms->is_monitor_use(inpidx) ) continue;
494 Node *inp = n->in(inpidx);
495 uint nidx = _phc.n2lidx(inp);
496 LRG &lrg = lrgs(nidx);
497
498 // If this lrg has a high frequency use/def
499 if( lrg._maxfreq >= _phc.high_frequency_lrg() ) {
500 // If the live range is also live out of this block (like it
501 // would be for a fast/slow idiom), the normal spill mechanism
502 // does an excellent job. If it is not live out of this block
503 // (like it would be for debug info to uncommon trap) splitting
504 // the live range now allows a better allocation in the high
505 // frequency blocks.
506 // Build_IFG_virtual has converted the live sets to
507 // live-IN info, not live-OUT info.
508 uint k;
509 for( k=0; k < b->_num_succs; k++ )
510 if( _phc._live->live(b->_succs[k])->member( nidx ) )
511 break; // Live in to some successor block?
512 if( k < b->_num_succs )
513 continue; // Live out; do not pre-split
514 // Split the lrg at this use
515 const RegMask *rm = C->matcher()->idealreg2spillmask[inp->ideal_reg()];
516 Node *copy = new (C) MachSpillCopyNode( inp, *rm, *rm );
517 // Insert the copy in the use-def chain
518 n->set_req(inpidx, copy );
519 // Insert the copy in the basic block, just before us
520 b->_nodes.insert( l++, copy );
521 // Extend ("register allocate") the names array for the copy.
522 _phc.new_lrg( copy, _phc._maxlrg++ );
523 _phc._cfg._bbs.map( copy->_idx, b );
524 //tty->print_cr("Split a debug use in Aggressive Coalesce");
525 } // End of if high frequency use/def
526 } // End of for all debug inputs
527 } // End of if low frequency safepoint
528
529 } // End of if Phi
530
531 } // End of for all instructions
532 } // End of for all blocks
533 }
534
535 //=============================================================================
536 //------------------------------coalesce---------------------------------------
537 // Aggressive (but pessimistic) copy coalescing of a single block
538
539 // The following coalesce pass represents a single round of aggressive
540 // pessimistic coalesce. "Aggressive" means no attempt to preserve
541 // colorability when coalescing. This occasionally means more spills, but
542 // it also means fewer rounds of coalescing for better code - and that means
543 // faster compiles.
544
545 // "Pessimistic" means we do not hit the fixed point in one pass (and we are
546 // reaching for the least fixed point to boot). This is typically solved
547 // with a few more rounds of coalescing, but the compiler must run fast. We
548 // could optimistically coalescing everything touching PhiNodes together
549 // into one big live range, then check for self-interference. Everywhere
550 // the live range interferes with self it would have to be split. Finding
551 // the right split points can be done with some heuristics (based on
552 // expected frequency of edges in the live range). In short, it's a real
553 // research problem and the timeline is too short to allow such research.
554 // Further thoughts: (1) build the LR in a pass, (2) find self-interference
555 // in another pass, (3) per each self-conflict, split, (4) split by finding
556 // the low-cost cut (min-cut) of the LR, (5) edges in the LR are weighted
557 // according to the GCM algorithm (or just exec freq on CFG edges).
558
559 void PhaseAggressiveCoalesce::coalesce( Block *b ) {
560 // Copies are still "virtual" - meaning we have not made them explicitly
561 // copies. Instead, Phi functions of successor blocks have mis-matched
562 // live-ranges. If I fail to coalesce, I'll have to insert a copy to line
563 // up the live-ranges. Check for Phis in successor blocks.
564 uint i;
565 for( i=0; i<b->_num_succs; i++ ) {
566 Block *bs = b->_succs[i];
567 // Find index of 'b' in 'bs' predecessors
568 uint j=1;
569 while( _phc._cfg._bbs[bs->pred(j)->_idx] != b ) j++;
570 // Visit all the Phis in successor block
571 for( uint k = 1; k<bs->_nodes.size(); k++ ) {
572 Node *n = bs->_nodes[k];
573 if( !n->is_Phi() ) break;
574 combine_these_two( n, n->in(j) );
575 }
576 } // End of for all successor blocks
577
578
579 // Check _this_ block for 2-address instructions and copies.
580 uint cnt = b->end_idx();
581 for( i = 1; i<cnt; i++ ) {
582 Node *n = b->_nodes[i];
583 uint idx;
584 // 2-address instructions have a virtual Copy matching their input
585 // to their output
586 if( n->is_Mach() && (idx = n->as_Mach()->two_adr()) ) {
587 MachNode *mach = n->as_Mach();
588 combine_these_two( mach, mach->in(idx) );
589 }
590 } // End of for all instructions in block
591 }
592
593 //=============================================================================
594 //------------------------------PhaseConservativeCoalesce----------------------
595 PhaseConservativeCoalesce::PhaseConservativeCoalesce( PhaseChaitin &chaitin ) : PhaseCoalesce(chaitin) {
596 _ulr.initialize(_phc._maxlrg);
597 }
598
599 //------------------------------verify-----------------------------------------
600 void PhaseConservativeCoalesce::verify() {
601 #ifdef ASSERT
602 _phc.set_was_low();
603 #endif
604 }
605
606 //------------------------------union_helper-----------------------------------
607 void PhaseConservativeCoalesce::union_helper( Node *lr1_node, Node *lr2_node, uint lr1, uint lr2, Node *src_def, Node *dst_copy, Node *src_copy, Block *b, uint bindex ) {
608 // Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
609 // union-find tree
610 _phc.Union( lr1_node, lr2_node );
611
612 // Single-def live range ONLY if both live ranges are single-def.
613 // If both are single def, then src_def powers one live range
614 // and def_copy powers the other. After merging, src_def powers
615 // the combined live range.
616 lrgs(lr1)._def = (lrgs(lr1).is_multidef() ||
617 lrgs(lr2).is_multidef() )
618 ? NodeSentinel : src_def;
619 lrgs(lr2)._def = NULL; // No def for lrg 2
620 lrgs(lr2).Clear(); // Force empty mask for LRG 2
621 //lrgs(lr2)._size = 0; // Live-range 2 goes dead
622 lrgs(lr1)._is_oop |= lrgs(lr2)._is_oop;
623 lrgs(lr2)._is_oop = 0; // In particular, not an oop for GC info
624
625 if (lrgs(lr1)._maxfreq < lrgs(lr2)._maxfreq)
626 lrgs(lr1)._maxfreq = lrgs(lr2)._maxfreq;
627
628 // Copy original value instead. Intermediate copies go dead, and
629 // the dst_copy becomes useless.
630 int didx = dst_copy->is_Copy();
631 dst_copy->set_req( didx, src_def );
632 // Add copy to free list
633 // _phc.free_spillcopy(b->_nodes[bindex]);
634 assert( b->_nodes[bindex] == dst_copy, "" );
635 dst_copy->replace_by( dst_copy->in(didx) );
636 dst_copy->set_req( didx, NULL);
637 b->_nodes.remove(bindex);
638 if( bindex < b->_ihrp_index ) b->_ihrp_index--;
639 if( bindex < b->_fhrp_index ) b->_fhrp_index--;
640
641 // Stretched lr1; add it to liveness of intermediate blocks
642 Block *b2 = _phc._cfg._bbs[src_copy->_idx];
643 while( b != b2 ) {
644 b = _phc._cfg._bbs[b->pred(1)->_idx];
645 _phc._live->live(b)->insert(lr1);
646 }
647 }
648
649 //------------------------------compute_separating_interferences---------------
650 // Factored code from copy_copy that computes extra interferences from
651 // lengthening a live range by double-coalescing.
652 uint PhaseConservativeCoalesce::compute_separating_interferences(Node *dst_copy, Node *src_copy, Block *b, uint bindex, RegMask &rm, uint reg_degree, uint rm_size, uint lr1, uint lr2 ) {
653
654 assert(!lrgs(lr1)._fat_proj, "cannot coalesce fat_proj");
655 assert(!lrgs(lr2)._fat_proj, "cannot coalesce fat_proj");
656 Node *prev_copy = dst_copy->in(dst_copy->is_Copy());
657 Block *b2 = b;
658 uint bindex2 = bindex;
659 while( 1 ) {
660 // Find previous instruction
661 bindex2--; // Chain backwards 1 instruction
662 while( bindex2 == 0 ) { // At block start, find prior block
663 assert( b2->num_preds() == 2, "cannot double coalesce across c-flow" );
664 b2 = _phc._cfg._bbs[b2->pred(1)->_idx];
665 bindex2 = b2->end_idx()-1;
666 }
667 // Get prior instruction
668 assert(bindex2 < b2->_nodes.size(), "index out of bounds");
669 Node *x = b2->_nodes[bindex2];
670 if( x == prev_copy ) { // Previous copy in copy chain?
671 if( prev_copy == src_copy)// Found end of chain and all interferences
672 break; // So break out of loop
673 // Else work back one in copy chain
674 prev_copy = prev_copy->in(prev_copy->is_Copy());
675 } else { // Else collect interferences
676 uint lidx = _phc.Find(x);
677 // Found another def of live-range being stretched?
678 if( lidx == lr1 ) return max_juint;
679 if( lidx == lr2 ) return max_juint;
680
681 // If we attempt to coalesce across a bound def
682 if( lrgs(lidx).is_bound() ) {
683 // Do not let the coalesced LRG expect to get the bound color
684 rm.SUBTRACT( lrgs(lidx).mask() );
685 // Recompute rm_size
686 rm_size = rm.Size();
687 //if( rm._flags ) rm_size += 1000000;
688 if( reg_degree >= rm_size ) return max_juint;
689 }
690 if( rm.overlap(lrgs(lidx).mask()) ) {
691 // Insert lidx into union LRG; returns TRUE if actually inserted
692 if( _ulr.insert(lidx) ) {
693 // Infinite-stack neighbors do not alter colorability, as they
694 // can always color to some other color.
695 if( !lrgs(lidx).mask().is_AllStack() ) {
696 // If this coalesce will make any new neighbor uncolorable,
697 // do not coalesce.
698 if( lrgs(lidx).just_lo_degree() )
699 return max_juint;
700 // Bump our degree
701 if( ++reg_degree >= rm_size )
702 return max_juint;
703 } // End of if not infinite-stack neighbor
704 } // End of if actually inserted
705 } // End of if live range overlaps
706 } // End of else collect interferences for 1 node
707 } // End of while forever, scan back for interferences
708 return reg_degree;
709 }
710
711 //------------------------------update_ifg-------------------------------------
712 void PhaseConservativeCoalesce::update_ifg(uint lr1, uint lr2, IndexSet *n_lr1, IndexSet *n_lr2) {
713 // Some original neighbors of lr1 might have gone away
714 // because the constrained register mask prevented them.
715 // Remove lr1 from such neighbors.
716 IndexSetIterator one(n_lr1);
717 uint neighbor;
718 LRG &lrg1 = lrgs(lr1);
719 while ((neighbor = one.next()) != 0)
720 if( !_ulr.member(neighbor) )
721 if( _phc._ifg->neighbors(neighbor)->remove(lr1) )
722 lrgs(neighbor).inc_degree( -lrg1.compute_degree(lrgs(neighbor)) );
723
724
725 // lr2 is now called (coalesced into) lr1.
726 // Remove lr2 from the IFG.
727 IndexSetIterator two(n_lr2);
728 LRG &lrg2 = lrgs(lr2);
729 while ((neighbor = two.next()) != 0)
730 if( _phc._ifg->neighbors(neighbor)->remove(lr2) )
731 lrgs(neighbor).inc_degree( -lrg2.compute_degree(lrgs(neighbor)) );
732
733 // Some neighbors of intermediate copies now interfere with the
734 // combined live range.
735 IndexSetIterator three(&_ulr);
736 while ((neighbor = three.next()) != 0)
737 if( _phc._ifg->neighbors(neighbor)->insert(lr1) )
738 lrgs(neighbor).inc_degree( lrg1.compute_degree(lrgs(neighbor)) );
739 }
740
741 //------------------------------record_bias------------------------------------
742 static void record_bias( const PhaseIFG *ifg, int lr1, int lr2 ) {
743 // Tag copy bias here
744 if( !ifg->lrgs(lr1)._copy_bias )
745 ifg->lrgs(lr1)._copy_bias = lr2;
746 if( !ifg->lrgs(lr2)._copy_bias )
747 ifg->lrgs(lr2)._copy_bias = lr1;
748 }
749
750 //------------------------------copy_copy--------------------------------------
751 // See if I can coalesce a series of multiple copies together. I need the
752 // final dest copy and the original src copy. They can be the same Node.
753 // Compute the compatible register masks.
754 bool PhaseConservativeCoalesce::copy_copy( Node *dst_copy, Node *src_copy, Block *b, uint bindex ) {
755
756 if( !dst_copy->is_SpillCopy() ) return false;
757 if( !src_copy->is_SpillCopy() ) return false;
758 Node *src_def = src_copy->in(src_copy->is_Copy());
759 uint lr1 = _phc.Find(dst_copy);
760 uint lr2 = _phc.Find(src_def );
761
762 // Same live ranges already?
763 if( lr1 == lr2 ) return false;
764
765 // Interfere?
766 if( _phc._ifg->test_edge_sq( lr1, lr2 ) ) return false;
767
768 // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
769 if( !lrgs(lr1)._is_oop && lrgs(lr2)._is_oop ) // not an oop->int cast
770 return false;
771
772 // Coalescing between an aligned live range and a mis-aligned live range?
773 // No, no! Alignment changes how we count degree.
774 if( lrgs(lr1)._fat_proj != lrgs(lr2)._fat_proj )
775 return false;
776
777 // Sort; use smaller live-range number
778 Node *lr1_node = dst_copy;
779 Node *lr2_node = src_def;
780 if( lr1 > lr2 ) {
781 uint tmp = lr1; lr1 = lr2; lr2 = tmp;
782 lr1_node = src_def; lr2_node = dst_copy;
783 }
784
785 // Check for compatibility of the 2 live ranges by
786 // intersecting their allowed register sets.
787 RegMask rm = lrgs(lr1).mask();
788 rm.AND(lrgs(lr2).mask());
789 // Number of bits free
790 uint rm_size = rm.Size();
791
792 if (UseFPUForSpilling && rm.is_AllStack() ) {
793 // Don't coalesce when frequency difference is large
794 Block *dst_b = _phc._cfg._bbs[dst_copy->_idx];
795 Block *src_def_b = _phc._cfg._bbs[src_def->_idx];
796 if (src_def_b->_freq > 10*dst_b->_freq )
797 return false;
798 }
799
800 // If we can use any stack slot, then effective size is infinite
801 if( rm.is_AllStack() ) rm_size += 1000000;
802 // Incompatible masks, no way to coalesce
803 if( rm_size == 0 ) return false;
804
805 // Another early bail-out test is when we are double-coalescing and the
806 // 2 copies are separated by some control flow.
807 if( dst_copy != src_copy ) {
808 Block *src_b = _phc._cfg._bbs[src_copy->_idx];
809 Block *b2 = b;
810 while( b2 != src_b ) {
811 if( b2->num_preds() > 2 ){// Found merge-point
812 _phc._lost_opp_cflow_coalesce++;
813 // extra record_bias commented out because Chris believes it is not
814 // productive. Since we can record only 1 bias, we want to choose one
815 // that stands a chance of working and this one probably does not.
816 //record_bias( _phc._lrgs, lr1, lr2 );
817 return false; // To hard to find all interferences
818 }
819 b2 = _phc._cfg._bbs[b2->pred(1)->_idx];
820 }
821 }
822
823 // Union the two interference sets together into '_ulr'
824 uint reg_degree = _ulr.lrg_union( lr1, lr2, rm_size, _phc._ifg, rm );
825
826 if( reg_degree >= rm_size ) {
827 record_bias( _phc._ifg, lr1, lr2 );
828 return false;
829 }
830
831 // Now I need to compute all the interferences between dst_copy and
832 // src_copy. I'm not willing visit the entire interference graph, so
833 // I limit my search to things in dst_copy's block or in a straight
834 // line of previous blocks. I give up at merge points or when I get
835 // more interferences than my degree. I can stop when I find src_copy.
836 if( dst_copy != src_copy ) {
837 reg_degree = compute_separating_interferences(dst_copy, src_copy, b, bindex, rm, rm_size, reg_degree, lr1, lr2 );
838 if( reg_degree == max_juint ) {
839 record_bias( _phc._ifg, lr1, lr2 );
840 return false;
841 }
842 } // End of if dst_copy & src_copy are different
843
844
845 // ---- THE COMBINED LRG IS COLORABLE ----
846
847 // YEAH - Now coalesce this copy away
848 assert( lrgs(lr1).num_regs() == lrgs(lr2).num_regs(), "" );
849
850 IndexSet *n_lr1 = _phc._ifg->neighbors(lr1);
851 IndexSet *n_lr2 = _phc._ifg->neighbors(lr2);
852
853 // Update the interference graph
854 update_ifg(lr1, lr2, n_lr1, n_lr2);
855
856 _ulr.remove(lr1);
857
858 // Uncomment the following code to trace Coalescing in great detail.
859 //
860 //if (false) {
861 // tty->cr();
862 // tty->print_cr("#######################################");
863 // tty->print_cr("union %d and %d", lr1, lr2);
864 // n_lr1->dump();
865 // n_lr2->dump();
866 // tty->print_cr("resulting set is");
867 // _ulr.dump();
868 //}
869
870 // Replace n_lr1 with the new combined live range. _ulr will use
871 // n_lr1's old memory on the next iteration. n_lr2 is cleared to
872 // send its internal memory to the free list.
873 _ulr.swap(n_lr1);
874 _ulr.clear();
875 n_lr2->clear();
876
877 lrgs(lr1).set_degree( _phc._ifg->effective_degree(lr1) );
878 lrgs(lr2).set_degree( 0 );
879
880 // Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
881 // union-find tree
882 union_helper( lr1_node, lr2_node, lr1, lr2, src_def, dst_copy, src_copy, b, bindex );
883 // Combine register restrictions
884 lrgs(lr1).set_mask(rm);
885 lrgs(lr1).compute_set_mask_size();
886 lrgs(lr1)._cost += lrgs(lr2)._cost;
887 lrgs(lr1)._area += lrgs(lr2)._area;
888
889 // While its uncommon to successfully coalesce live ranges that started out
890 // being not-lo-degree, it can happen. In any case the combined coalesced
891 // live range better Simplify nicely.
892 lrgs(lr1)._was_lo = 1;
893
894 // kinda expensive to do all the time
895 //tty->print_cr("warning: slow verify happening");
896 //_phc._ifg->verify( &_phc );
897 return true;
898 }
899
900 //------------------------------coalesce---------------------------------------
901 // Conservative (but pessimistic) copy coalescing of a single block
902 void PhaseConservativeCoalesce::coalesce( Block *b ) {
903 // Bail out on infrequent blocks
904 if( b->is_uncommon(_phc._cfg._bbs) )
905 return;
906 // Check this block for copies.
907 for( uint i = 1; i<b->end_idx(); i++ ) {
908 // Check for actual copies on inputs. Coalesce a copy into its
909 // input if use and copy's input are compatible.
910 Node *copy1 = b->_nodes[i];
911 uint idx1 = copy1->is_Copy();
912 if( !idx1 ) continue; // Not a copy
913
914 if( copy_copy(copy1,copy1,b,i) ) {
915 i--; // Retry, same location in block
916 PhaseChaitin::_conserv_coalesce++; // Collect stats on success
917 continue;
918 }
919
920 /* do not attempt pairs. About 1/2 of all pairs can be removed by
921 post-alloc. The other set are too few to bother.
922 Node *copy2 = copy1->in(idx1);
923 uint idx2 = copy2->is_Copy();
924 if( !idx2 ) continue;
925 if( copy_copy(copy1,copy2,b,i) ) {
926 i--; // Retry, same location in block
927 PhaseChaitin::_conserv_coalesce_pair++; // Collect stats on success
928 continue;
929 }
930 */
931 }
932 }