Mercurial > hg > graal-compiler
comparison src/share/vm/opto/block.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 756b58154237 |
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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 } |