Mercurial > hg > truffle
annotate src/share/vm/opto/block.cpp @ 17557:c96a3381e55e
8035283: Second phase of branch shortening doesn't account for loop alignment
Summary: added missing check for loop padding case.
Reviewed-by: kvn, jrose
author | poonam |
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date | Fri, 28 Feb 2014 02:43:16 -0800 |
parents | 55fb97c4c58d |
children | abec000618bf |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "libadt/vectset.hpp" | |
27 #include "memory/allocation.inline.hpp" | |
28 #include "opto/block.hpp" | |
29 #include "opto/cfgnode.hpp" | |
30 #include "opto/chaitin.hpp" | |
31 #include "opto/loopnode.hpp" | |
32 #include "opto/machnode.hpp" | |
33 #include "opto/matcher.hpp" | |
34 #include "opto/opcodes.hpp" | |
35 #include "opto/rootnode.hpp" | |
36 #include "utilities/copy.hpp" | |
0 | 37 |
38 void Block_Array::grow( uint i ) { | |
39 assert(i >= Max(), "must be an overflow"); | |
40 debug_only(_limit = i+1); | |
41 if( i < _size ) return; | |
42 if( !_size ) { | |
43 _size = 1; | |
44 _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) ); | |
45 _blocks[0] = NULL; | |
46 } | |
47 uint old = _size; | |
48 while( i >= _size ) _size <<= 1; // Double to fit | |
49 _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*)); | |
50 Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) ); | |
51 } | |
52 | |
53 void Block_List::remove(uint i) { | |
54 assert(i < _cnt, "index out of bounds"); | |
55 Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*))); | |
56 pop(); // shrink list by one block | |
57 } | |
58 | |
59 void Block_List::insert(uint i, Block *b) { | |
60 push(b); // grow list by one block | |
61 Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*))); | |
62 _blocks[i] = b; | |
63 } | |
64 | |
418 | 65 #ifndef PRODUCT |
66 void Block_List::print() { | |
67 for (uint i=0; i < size(); i++) { | |
68 tty->print("B%d ", _blocks[i]->_pre_order); | |
69 } | |
70 tty->print("size = %d\n", size()); | |
71 } | |
72 #endif | |
0 | 73 |
74 uint Block::code_alignment() { | |
75 // Check for Root block | |
3851 | 76 if (_pre_order == 0) return CodeEntryAlignment; |
0 | 77 // Check for Start block |
3851 | 78 if (_pre_order == 1) return InteriorEntryAlignment; |
0 | 79 // Check for loop alignment |
3851 | 80 if (has_loop_alignment()) return loop_alignment(); |
418 | 81 |
3851 | 82 return relocInfo::addr_unit(); // no particular alignment |
418 | 83 } |
84 | |
85 uint Block::compute_loop_alignment() { | |
0 | 86 Node *h = head(); |
3851 | 87 int unit_sz = relocInfo::addr_unit(); |
88 if (h->is_Loop() && h->as_Loop()->is_inner_loop()) { | |
0 | 89 // Pre- and post-loops have low trip count so do not bother with |
90 // NOPs for align loop head. The constants are hidden from tuning | |
91 // but only because my "divide by 4" heuristic surely gets nearly | |
92 // all possible gain (a "do not align at all" heuristic has a | |
93 // chance of getting a really tiny gain). | |
3851 | 94 if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() || |
95 h->as_CountedLoop()->is_post_loop())) { | |
96 return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz; | |
97 } | |
0 | 98 // Loops with low backedge frequency should not be aligned. |
99 Node *n = h->in(LoopNode::LoopBackControl)->in(0); | |
3851 | 100 if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) { |
101 return unit_sz; // Loop does not loop, more often than not! | |
0 | 102 } |
103 return OptoLoopAlignment; // Otherwise align loop head | |
104 } | |
418 | 105 |
3851 | 106 return unit_sz; // no particular alignment |
0 | 107 } |
108 | |
109 // Compute the size of first 'inst_cnt' instructions in this block. | |
110 // Return the number of instructions left to compute if the block has | |
418 | 111 // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size |
112 // exceeds OptoLoopAlignment. | |
0 | 113 uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt, |
114 PhaseRegAlloc* ra) { | |
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115 uint last_inst = number_of_nodes(); |
0 | 116 for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { |
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117 uint inst_size = get_node(j)->size(ra); |
0 | 118 if( inst_size > 0 ) { |
119 inst_cnt--; | |
120 uint sz = sum_size + inst_size; | |
121 if( sz <= (uint)OptoLoopAlignment ) { | |
122 // Compute size of instructions which fit into fetch buffer only | |
123 // since all inst_cnt instructions will not fit even if we align them. | |
124 sum_size = sz; | |
125 } else { | |
126 return 0; | |
127 } | |
128 } | |
129 } | |
130 return inst_cnt; | |
131 } | |
132 | |
133 uint Block::find_node( const Node *n ) const { | |
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134 for( uint i = 0; i < number_of_nodes(); i++ ) { |
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135 if( get_node(i) == n ) |
0 | 136 return i; |
137 } | |
138 ShouldNotReachHere(); | |
139 return 0; | |
140 } | |
141 | |
142 // Find and remove n from block list | |
143 void Block::find_remove( const Node *n ) { | |
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144 remove_node(find_node(n)); |
0 | 145 } |
146 | |
147 // Return empty status of a block. Empty blocks contain only the head, other | |
148 // ideal nodes, and an optional trailing goto. | |
149 int Block::is_Empty() const { | |
150 | |
151 // Root or start block is not considered empty | |
152 if (head()->is_Root() || head()->is_Start()) { | |
153 return not_empty; | |
154 } | |
155 | |
156 int success_result = completely_empty; | |
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157 int end_idx = number_of_nodes() - 1; |
0 | 158 |
159 // Check for ending goto | |
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160 if ((end_idx > 0) && (get_node(end_idx)->is_MachGoto())) { |
0 | 161 success_result = empty_with_goto; |
162 end_idx--; | |
163 } | |
164 | |
165 // Unreachable blocks are considered empty | |
166 if (num_preds() <= 1) { | |
167 return success_result; | |
168 } | |
169 | |
170 // Ideal nodes are allowable in empty blocks: skip them Only MachNodes | |
171 // turn directly into code, because only MachNodes have non-trivial | |
172 // emit() functions. | |
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173 while ((end_idx > 0) && !get_node(end_idx)->is_Mach()) { |
0 | 174 end_idx--; |
175 } | |
176 | |
177 // No room for any interesting instructions? | |
178 if (end_idx == 0) { | |
179 return success_result; | |
180 } | |
181 | |
182 return not_empty; | |
183 } | |
184 | |
605 | 185 // Return true if the block's code implies that it is likely to be |
0 | 186 // executed infrequently. Check to see if the block ends in a Halt or |
187 // a low probability call. | |
188 bool Block::has_uncommon_code() const { | |
189 Node* en = end(); | |
190 | |
3842 | 191 if (en->is_MachGoto()) |
0 | 192 en = en->in(0); |
193 if (en->is_Catch()) | |
194 en = en->in(0); | |
3842 | 195 if (en->is_MachProj() && en->in(0)->is_MachCall()) { |
0 | 196 MachCallNode* call = en->in(0)->as_MachCall(); |
197 if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { | |
198 // This is true for slow-path stubs like new_{instance,array}, | |
199 // slow_arraycopy, complete_monitor_locking, uncommon_trap. | |
200 // The magic number corresponds to the probability of an uncommon_trap, | |
201 // even though it is a count not a probability. | |
202 return true; | |
203 } | |
204 } | |
205 | |
206 int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); | |
207 return op == Op_Halt; | |
208 } | |
209 | |
210 // True if block is low enough frequency or guarded by a test which | |
211 // mostly does not go here. | |
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212 bool PhaseCFG::is_uncommon(const Block* block) { |
0 | 213 // Initial blocks must never be moved, so are never uncommon. |
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214 if (block->head()->is_Root() || block->head()->is_Start()) return false; |
0 | 215 |
216 // Check for way-low freq | |
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217 if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) return true; |
0 | 218 |
219 // Look for code shape indicating uncommon_trap or slow path | |
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220 if (block->has_uncommon_code()) return true; |
0 | 221 |
222 const float epsilon = 0.05f; | |
223 const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon); | |
224 uint uncommon_preds = 0; | |
225 uint freq_preds = 0; | |
226 uint uncommon_for_freq_preds = 0; | |
227 | |
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228 for( uint i=1; i< block->num_preds(); i++ ) { |
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229 Block* guard = get_block_for_node(block->pred(i)); |
0 | 230 // Check to see if this block follows its guard 1 time out of 10000 |
231 // or less. | |
232 // | |
233 // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which | |
234 // we intend to be "uncommon", such as slow-path TLE allocation, | |
235 // predicted call failure, and uncommon trap triggers. | |
236 // | |
237 // Use an epsilon value of 5% to allow for variability in frequency | |
238 // predictions and floating point calculations. The net effect is | |
239 // that guard_factor is set to 9500. | |
240 // | |
241 // Ignore low-frequency blocks. | |
242 // The next check is (guard->_freq < 1.e-5 * 9500.). | |
243 if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) { | |
244 uncommon_preds++; | |
245 } else { | |
246 freq_preds++; | |
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247 if(block->_freq < guard->_freq * guard_factor ) { |
0 | 248 uncommon_for_freq_preds++; |
249 } | |
250 } | |
251 } | |
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252 if( block->num_preds() > 1 && |
0 | 253 // The block is uncommon if all preds are uncommon or |
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254 (uncommon_preds == (block->num_preds()-1) || |
0 | 255 // it is uncommon for all frequent preds. |
256 uncommon_for_freq_preds == freq_preds) ) { | |
257 return true; | |
258 } | |
259 return false; | |
260 } | |
261 | |
262 #ifndef PRODUCT | |
3851 | 263 void Block::dump_bidx(const Block* orig, outputStream* st) const { |
264 if (_pre_order) st->print("B%d",_pre_order); | |
265 else st->print("N%d", head()->_idx); | |
0 | 266 |
267 if (Verbose && orig != this) { | |
268 // Dump the original block's idx | |
3851 | 269 st->print(" ("); |
270 orig->dump_bidx(orig, st); | |
271 st->print(")"); | |
0 | 272 } |
273 } | |
274 | |
12023 | 275 void Block::dump_pred(const PhaseCFG* cfg, Block* orig, outputStream* st) const { |
0 | 276 if (is_connector()) { |
277 for (uint i=1; i<num_preds(); i++) { | |
12023 | 278 Block *p = cfg->get_block_for_node(pred(i)); |
279 p->dump_pred(cfg, orig, st); | |
0 | 280 } |
281 } else { | |
3851 | 282 dump_bidx(orig, st); |
283 st->print(" "); | |
0 | 284 } |
285 } | |
286 | |
12023 | 287 void Block::dump_head(const PhaseCFG* cfg, outputStream* st) const { |
0 | 288 // Print the basic block |
3851 | 289 dump_bidx(this, st); |
290 st->print(": #\t"); | |
0 | 291 |
292 // Print the incoming CFG edges and the outgoing CFG edges | |
293 for( uint i=0; i<_num_succs; i++ ) { | |
3851 | 294 non_connector_successor(i)->dump_bidx(_succs[i], st); |
295 st->print(" "); | |
0 | 296 } |
3851 | 297 st->print("<- "); |
0 | 298 if( head()->is_block_start() ) { |
299 for (uint i=1; i<num_preds(); i++) { | |
300 Node *s = pred(i); | |
12023 | 301 if (cfg != NULL) { |
302 Block *p = cfg->get_block_for_node(s); | |
303 p->dump_pred(cfg, p, st); | |
0 | 304 } else { |
305 while (!s->is_block_start()) | |
306 s = s->in(0); | |
3851 | 307 st->print("N%d ", s->_idx ); |
0 | 308 } |
309 } | |
12023 | 310 } else { |
3851 | 311 st->print("BLOCK HEAD IS JUNK "); |
12023 | 312 } |
0 | 313 |
314 // Print loop, if any | |
315 const Block *bhead = this; // Head of self-loop | |
316 Node *bh = bhead->head(); | |
12023 | 317 |
318 if ((cfg != NULL) && bh->is_Loop() && !head()->is_Root()) { | |
0 | 319 LoopNode *loop = bh->as_Loop(); |
12023 | 320 const Block *bx = cfg->get_block_for_node(loop->in(LoopNode::LoopBackControl)); |
0 | 321 while (bx->is_connector()) { |
12023 | 322 bx = cfg->get_block_for_node(bx->pred(1)); |
0 | 323 } |
3851 | 324 st->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order); |
0 | 325 // Dump any loop-specific bits, especially for CountedLoops. |
3851 | 326 loop->dump_spec(st); |
418 | 327 } else if (has_loop_alignment()) { |
3851 | 328 st->print(" top-of-loop"); |
0 | 329 } |
3851 | 330 st->print(" Freq: %g",_freq); |
0 | 331 if( Verbose || WizardMode ) { |
3851 | 332 st->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth); |
333 st->print(" RegPressure: %d",_reg_pressure); | |
334 st->print(" IHRP Index: %d",_ihrp_index); | |
335 st->print(" FRegPressure: %d",_freg_pressure); | |
336 st->print(" FHRP Index: %d",_fhrp_index); | |
0 | 337 } |
3851 | 338 st->print_cr(""); |
0 | 339 } |
340 | |
12023 | 341 void Block::dump() const { |
342 dump(NULL); | |
343 } | |
0 | 344 |
12023 | 345 void Block::dump(const PhaseCFG* cfg) const { |
346 dump_head(cfg); | |
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347 for (uint i=0; i< number_of_nodes(); i++) { |
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348 get_node(i)->dump(); |
12023 | 349 } |
0 | 350 tty->print("\n"); |
351 } | |
352 #endif | |
353 | |
12023 | 354 PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher) |
355 : Phase(CFG) | |
356 , _block_arena(arena) | |
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357 , _root(root) |
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358 , _matcher(matcher) |
12023 | 359 , _node_to_block_mapping(arena) |
360 , _node_latency(NULL) | |
0 | 361 #ifndef PRODUCT |
12023 | 362 , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining")) |
0 | 363 #endif |
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364 #ifdef ASSERT |
12023 | 365 , _raw_oops(arena) |
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366 #endif |
0 | 367 { |
368 ResourceMark rm; | |
369 // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, | |
370 // then Match it into a machine-specific Node. Then clone the machine | |
371 // Node on demand. | |
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372 Node *x = new (C) GotoNode(NULL); |
0 | 373 x->init_req(0, x); |
12023 | 374 _goto = matcher.match_tree(x); |
0 | 375 assert(_goto != NULL, ""); |
376 _goto->set_req(0,_goto); | |
377 | |
378 // Build the CFG in Reverse Post Order | |
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379 _number_of_blocks = build_cfg(); |
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380 _root_block = get_block_for_node(_root); |
0 | 381 } |
382 | |
383 // Build a proper looking CFG. Make every block begin with either a StartNode | |
384 // or a RegionNode. Make every block end with either a Goto, If or Return. | |
385 // The RootNode both starts and ends it's own block. Do this with a recursive | |
386 // backwards walk over the control edges. | |
387 uint PhaseCFG::build_cfg() { | |
388 Arena *a = Thread::current()->resource_area(); | |
389 VectorSet visited(a); | |
390 | |
391 // Allocate stack with enough space to avoid frequent realloc | |
392 Node_Stack nstack(a, C->unique() >> 1); | |
393 nstack.push(_root, 0); | |
394 uint sum = 0; // Counter for blocks | |
395 | |
396 while (nstack.is_nonempty()) { | |
397 // node and in's index from stack's top | |
398 // 'np' is _root (see above) or RegionNode, StartNode: we push on stack | |
399 // only nodes which point to the start of basic block (see below). | |
400 Node *np = nstack.node(); | |
401 // idx > 0, except for the first node (_root) pushed on stack | |
402 // at the beginning when idx == 0. | |
403 // We will use the condition (idx == 0) later to end the build. | |
404 uint idx = nstack.index(); | |
405 Node *proj = np->in(idx); | |
406 const Node *x = proj->is_block_proj(); | |
407 // Does the block end with a proper block-ending Node? One of Return, | |
408 // If or Goto? (This check should be done for visited nodes also). | |
409 if (x == NULL) { // Does not end right... | |
410 Node *g = _goto->clone(); // Force it to end in a Goto | |
411 g->set_req(0, proj); | |
412 np->set_req(idx, g); | |
413 x = proj = g; | |
414 } | |
415 if (!visited.test_set(x->_idx)) { // Visit this block once | |
416 // Skip any control-pinned middle'in stuff | |
417 Node *p = proj; | |
418 do { | |
419 proj = p; // Update pointer to last Control | |
420 p = p->in(0); // Move control forward | |
421 } while( !p->is_block_proj() && | |
422 !p->is_block_start() ); | |
423 // Make the block begin with one of Region or StartNode. | |
424 if( !p->is_block_start() ) { | |
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425 RegionNode *r = new (C) RegionNode( 2 ); |
0 | 426 r->init_req(1, p); // Insert RegionNode in the way |
427 proj->set_req(0, r); // Insert RegionNode in the way | |
428 p = r; | |
429 } | |
430 // 'p' now points to the start of this basic block | |
431 | |
432 // Put self in array of basic blocks | |
12023 | 433 Block *bb = new (_block_arena) Block(_block_arena, p); |
434 map_node_to_block(p, bb); | |
435 map_node_to_block(x, bb); | |
3851 | 436 if( x != p ) { // Only for root is x == p |
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437 bb->push_node((Node*)x); |
3851 | 438 } |
0 | 439 // Now handle predecessors |
440 ++sum; // Count 1 for self block | |
441 uint cnt = bb->num_preds(); | |
442 for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors | |
443 Node *prevproj = p->in(i); // Get prior input | |
444 assert( !prevproj->is_Con(), "dead input not removed" ); | |
445 // Check to see if p->in(i) is a "control-dependent" CFG edge - | |
446 // i.e., it splits at the source (via an IF or SWITCH) and merges | |
447 // at the destination (via a many-input Region). | |
448 // This breaks critical edges. The RegionNode to start the block | |
449 // will be added when <p,i> is pulled off the node stack | |
450 if ( cnt > 2 ) { // Merging many things? | |
451 assert( prevproj== bb->pred(i),""); | |
452 if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? | |
453 // Force a block on the control-dependent edge | |
454 Node *g = _goto->clone(); // Force it to end in a Goto | |
455 g->set_req(0,prevproj); | |
456 p->set_req(i,g); | |
457 } | |
458 } | |
459 nstack.push(p, i); // 'p' is RegionNode or StartNode | |
460 } | |
461 } else { // Post-processing visited nodes | |
462 nstack.pop(); // remove node from stack | |
463 // Check if it the fist node pushed on stack at the beginning. | |
464 if (idx == 0) break; // end of the build | |
465 // Find predecessor basic block | |
12023 | 466 Block *pb = get_block_for_node(x); |
0 | 467 // Insert into nodes array, if not already there |
12023 | 468 if (!has_block(proj)) { |
0 | 469 assert( x != proj, "" ); |
470 // Map basic block of projection | |
12023 | 471 map_node_to_block(proj, pb); |
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472 pb->push_node(proj); |
0 | 473 } |
474 // Insert self as a child of my predecessor block | |
12023 | 475 pb->_succs.map(pb->_num_succs++, get_block_for_node(np)); |
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476 assert( pb->get_node(pb->number_of_nodes() - pb->_num_succs)->is_block_proj(), |
0 | 477 "too many control users, not a CFG?" ); |
478 } | |
479 } | |
480 // Return number of basic blocks for all children and self | |
481 return sum; | |
482 } | |
483 | |
484 // Inserts a goto & corresponding basic block between | |
485 // block[block_no] and its succ_no'th successor block | |
486 void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { | |
487 // get block with block_no | |
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488 assert(block_no < number_of_blocks(), "illegal block number"); |
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489 Block* in = get_block(block_no); |
0 | 490 // get successor block succ_no |
491 assert(succ_no < in->_num_succs, "illegal successor number"); | |
492 Block* out = in->_succs[succ_no]; | |
308 | 493 // Compute frequency of the new block. Do this before inserting |
494 // new block in case succ_prob() needs to infer the probability from | |
495 // surrounding blocks. | |
496 float freq = in->_freq * in->succ_prob(succ_no); | |
0 | 497 // get ProjNode corresponding to the succ_no'th successor of the in block |
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498 ProjNode* proj = in->get_node(in->number_of_nodes() - in->_num_succs + succ_no)->as_Proj(); |
0 | 499 // create region for basic block |
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500 RegionNode* region = new (C) RegionNode(2); |
0 | 501 region->init_req(1, proj); |
502 // setup corresponding basic block | |
12023 | 503 Block* block = new (_block_arena) Block(_block_arena, region); |
504 map_node_to_block(region, block); | |
0 | 505 C->regalloc()->set_bad(region->_idx); |
506 // add a goto node | |
507 Node* gto = _goto->clone(); // get a new goto node | |
508 gto->set_req(0, region); | |
509 // add it to the basic block | |
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510 block->push_node(gto); |
12023 | 511 map_node_to_block(gto, block); |
0 | 512 C->regalloc()->set_bad(gto->_idx); |
513 // hook up successor block | |
514 block->_succs.map(block->_num_succs++, out); | |
515 // remap successor's predecessors if necessary | |
516 for (uint i = 1; i < out->num_preds(); i++) { | |
517 if (out->pred(i) == proj) out->head()->set_req(i, gto); | |
518 } | |
519 // remap predecessor's successor to new block | |
520 in->_succs.map(succ_no, block); | |
308 | 521 // Set the frequency of the new block |
522 block->_freq = freq; | |
0 | 523 // add new basic block to basic block list |
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524 add_block_at(block_no + 1, block); |
0 | 525 } |
526 | |
527 // Does this block end in a multiway branch that cannot have the default case | |
528 // flipped for another case? | |
529 static bool no_flip_branch( Block *b ) { | |
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530 int branch_idx = b->number_of_nodes() - b->_num_succs-1; |
0 | 531 if( branch_idx < 1 ) return false; |
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532 Node *bra = b->get_node(branch_idx); |
418 | 533 if( bra->is_Catch() ) |
534 return true; | |
0 | 535 if( bra->is_Mach() ) { |
418 | 536 if( bra->is_MachNullCheck() ) |
537 return true; | |
0 | 538 int iop = bra->as_Mach()->ideal_Opcode(); |
539 if( iop == Op_FastLock || iop == Op_FastUnlock ) | |
540 return true; | |
541 } | |
542 return false; | |
543 } | |
544 | |
545 // Check for NeverBranch at block end. This needs to become a GOTO to the | |
546 // true target. NeverBranch are treated as a conditional branch that always | |
547 // goes the same direction for most of the optimizer and are used to give a | |
548 // fake exit path to infinite loops. At this late stage they need to turn | |
549 // into Goto's so that when you enter the infinite loop you indeed hang. | |
550 void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { | |
551 // Find true target | |
552 int end_idx = b->end_idx(); | |
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553 int idx = b->get_node(end_idx+1)->as_Proj()->_con; |
0 | 554 Block *succ = b->_succs[idx]; |
555 Node* gto = _goto->clone(); // get a new goto node | |
556 gto->set_req(0, b->head()); | |
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557 Node *bp = b->get_node(end_idx); |
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558 b->map_node(gto, end_idx); // Slam over NeverBranch |
12023 | 559 map_node_to_block(gto, b); |
0 | 560 C->regalloc()->set_bad(gto->_idx); |
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561 b->pop_node(); // Yank projections |
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562 b->pop_node(); // Yank projections |
0 | 563 b->_succs.map(0,succ); // Map only successor |
564 b->_num_succs = 1; | |
565 // remap successor's predecessors if necessary | |
566 uint j; | |
567 for( j = 1; j < succ->num_preds(); j++) | |
568 if( succ->pred(j)->in(0) == bp ) | |
569 succ->head()->set_req(j, gto); | |
570 // Kill alternate exit path | |
571 Block *dead = b->_succs[1-idx]; | |
572 for( j = 1; j < dead->num_preds(); j++) | |
573 if( dead->pred(j)->in(0) == bp ) | |
574 break; | |
575 // Scan through block, yanking dead path from | |
576 // all regions and phis. | |
577 dead->head()->del_req(j); | |
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578 for( int k = 1; dead->get_node(k)->is_Phi(); k++ ) |
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579 dead->get_node(k)->del_req(j); |
0 | 580 } |
581 | |
582 // Helper function to move block bx to the slot following b_index. Return | |
583 // true if the move is successful, otherwise false | |
418 | 584 bool PhaseCFG::move_to_next(Block* bx, uint b_index) { |
0 | 585 if (bx == NULL) return false; |
586 | |
587 // Return false if bx is already scheduled. | |
588 uint bx_index = bx->_pre_order; | |
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589 if ((bx_index <= b_index) && (get_block(bx_index) == bx)) { |
0 | 590 return false; |
591 } | |
592 | |
593 // Find the current index of block bx on the block list | |
594 bx_index = b_index + 1; | |
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595 while (bx_index < number_of_blocks() && get_block(bx_index) != bx) { |
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596 bx_index++; |
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597 } |
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598 assert(get_block(bx_index) == bx, "block not found"); |
0 | 599 |
600 // If the previous block conditionally falls into bx, return false, | |
601 // because moving bx will create an extra jump. | |
602 for(uint k = 1; k < bx->num_preds(); k++ ) { | |
12023 | 603 Block* pred = get_block_for_node(bx->pred(k)); |
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604 if (pred == get_block(bx_index - 1)) { |
0 | 605 if (pred->_num_succs != 1) { |
606 return false; | |
607 } | |
608 } | |
609 } | |
610 | |
611 // Reinsert bx just past block 'b' | |
612 _blocks.remove(bx_index); | |
613 _blocks.insert(b_index + 1, bx); | |
614 return true; | |
615 } | |
616 | |
617 // Move empty and uncommon blocks to the end. | |
418 | 618 void PhaseCFG::move_to_end(Block *b, uint i) { |
0 | 619 int e = b->is_Empty(); |
620 if (e != Block::not_empty) { | |
621 if (e == Block::empty_with_goto) { | |
622 // Remove the goto, but leave the block. | |
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623 b->pop_node(); |
0 | 624 } |
625 // Mark this block as a connector block, which will cause it to be | |
626 // ignored in certain functions such as non_connector_successor(). | |
627 b->set_connector(); | |
628 } | |
629 // Move the empty block to the end, and don't recheck. | |
630 _blocks.remove(i); | |
631 _blocks.push(b); | |
632 } | |
633 | |
418 | 634 // Set loop alignment for every block |
635 void PhaseCFG::set_loop_alignment() { | |
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636 uint last = number_of_blocks(); |
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637 assert(get_block(0) == get_root_block(), ""); |
418 | 638 |
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639 for (uint i = 1; i < last; i++) { |
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640 Block* block = get_block(i); |
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641 if (block->head()->is_Loop()) { |
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642 block->set_loop_alignment(block); |
418 | 643 } |
644 } | |
645 } | |
646 | |
647 // Make empty basic blocks to be "connector" blocks, Move uncommon blocks | |
648 // to the end. | |
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649 void PhaseCFG::remove_empty_blocks() { |
0 | 650 // Move uncommon blocks to the end |
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651 uint last = number_of_blocks(); |
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652 assert(get_block(0) == get_root_block(), ""); |
418 | 653 |
654 for (uint i = 1; i < last; i++) { | |
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655 Block* block = get_block(i); |
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656 if (block->is_connector()) { |
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657 break; |
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658 } |
0 | 659 |
660 // Check for NeverBranch at block end. This needs to become a GOTO to the | |
661 // true target. NeverBranch are treated as a conditional branch that | |
662 // always goes the same direction for most of the optimizer and are used | |
663 // to give a fake exit path to infinite loops. At this late stage they | |
664 // need to turn into Goto's so that when you enter the infinite loop you | |
665 // indeed hang. | |
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666 if (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) { |
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667 convert_NeverBranch_to_Goto(block); |
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668 } |
0 | 669 |
670 // Look for uncommon blocks and move to end. | |
418 | 671 if (!C->do_freq_based_layout()) { |
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672 if (is_uncommon(block)) { |
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673 move_to_end(block, i); |
418 | 674 last--; // No longer check for being uncommon! |
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675 if (no_flip_branch(block)) { // Fall-thru case must follow? |
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676 // Find the fall-thru block |
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677 block = get_block(i); |
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678 move_to_end(block, i); |
418 | 679 last--; |
680 } | |
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681 // backup block counter post-increment |
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682 i--; |
0 | 683 } |
684 } | |
685 } | |
686 | |
418 | 687 // Move empty blocks to the end |
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688 last = number_of_blocks(); |
418 | 689 for (uint i = 1; i < last; i++) { |
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690 Block* block = get_block(i); |
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691 if (block->is_Empty() != Block::not_empty) { |
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692 move_to_end(block, i); |
418 | 693 last--; |
694 i--; | |
0 | 695 } |
696 } // End of for all blocks | |
418 | 697 } |
0 | 698 |
418 | 699 // Fix up the final control flow for basic blocks. |
700 void PhaseCFG::fixup_flow() { | |
0 | 701 // Fixup final control flow for the blocks. Remove jump-to-next |
702 // block. If neither arm of a IF follows the conditional branch, we | |
703 // have to add a second jump after the conditional. We place the | |
704 // TRUE branch target in succs[0] for both GOTOs and IFs. | |
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705 for (uint i = 0; i < number_of_blocks(); i++) { |
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706 Block* block = get_block(i); |
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707 block->_pre_order = i; // turn pre-order into block-index |
0 | 708 |
709 // Connector blocks need no further processing. | |
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710 if (block->is_connector()) { |
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711 assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end"); |
0 | 712 continue; |
713 } | |
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714 assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors"); |
0 | 715 |
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716 Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL; |
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717 Block* bs0 = block->non_connector_successor(0); |
0 | 718 |
719 // Check for multi-way branches where I cannot negate the test to | |
720 // exchange the true and false targets. | |
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721 if (no_flip_branch(block)) { |
0 | 722 // Find fall through case - if must fall into its target |
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723 int branch_idx = block->number_of_nodes() - block->_num_succs; |
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724 for (uint j2 = 0; j2 < block->_num_succs; j2++) { |
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725 const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj(); |
0 | 726 if (p->_con == 0) { |
727 // successor j2 is fall through case | |
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728 if (block->non_connector_successor(j2) != bnext) { |
0 | 729 // but it is not the next block => insert a goto |
730 insert_goto_at(i, j2); | |
731 } | |
732 // Put taken branch in slot 0 | |
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733 if (j2 == 0 && block->_num_succs == 2) { |
0 | 734 // Flip targets in succs map |
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735 Block *tbs0 = block->_succs[0]; |
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736 Block *tbs1 = block->_succs[1]; |
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737 block->_succs.map(0, tbs1); |
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738 block->_succs.map(1, tbs0); |
0 | 739 } |
740 break; | |
741 } | |
742 } | |
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743 |
0 | 744 // Remove all CatchProjs |
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745 for (uint j = 0; j < block->_num_succs; j++) { |
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746 block->pop_node(); |
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747 } |
0 | 748 |
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749 } else if (block->_num_succs == 1) { |
0 | 750 // Block ends in a Goto? |
751 if (bnext == bs0) { | |
752 // We fall into next block; remove the Goto | |
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753 block->pop_node(); |
0 | 754 } |
755 | |
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756 } else if(block->_num_succs == 2) { // Block ends in a If? |
0 | 757 // Get opcode of 1st projection (matches _succs[0]) |
758 // Note: Since this basic block has 2 exits, the last 2 nodes must | |
759 // be projections (in any order), the 3rd last node must be | |
760 // the IfNode (we have excluded other 2-way exits such as | |
761 // CatchNodes already). | |
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762 MachNode* iff = block->get_node(block->number_of_nodes() - 3)->as_Mach(); |
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763 ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj(); |
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764 ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj(); |
0 | 765 |
766 // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. | |
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767 assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); |
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768 assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); |
0 | 769 |
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770 Block* bs1 = block->non_connector_successor(1); |
0 | 771 |
772 // Check for neither successor block following the current | |
773 // block ending in a conditional. If so, move one of the | |
774 // successors after the current one, provided that the | |
775 // successor was previously unscheduled, but moveable | |
776 // (i.e., all paths to it involve a branch). | |
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777 if (!C->do_freq_based_layout() && bnext != bs0 && bnext != bs1) { |
0 | 778 // Choose the more common successor based on the probability |
779 // of the conditional branch. | |
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780 Block* bx = bs0; |
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781 Block* by = bs1; |
0 | 782 |
783 // _prob is the probability of taking the true path. Make | |
784 // p the probability of taking successor #1. | |
785 float p = iff->as_MachIf()->_prob; | |
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786 if (proj0->Opcode() == Op_IfTrue) { |
0 | 787 p = 1.0 - p; |
788 } | |
789 | |
790 // Prefer successor #1 if p > 0.5 | |
791 if (p > PROB_FAIR) { | |
792 bx = bs1; | |
793 by = bs0; | |
794 } | |
795 | |
796 // Attempt the more common successor first | |
418 | 797 if (move_to_next(bx, i)) { |
0 | 798 bnext = bx; |
418 | 799 } else if (move_to_next(by, i)) { |
0 | 800 bnext = by; |
801 } | |
802 } | |
803 | |
804 // Check for conditional branching the wrong way. Negate | |
805 // conditional, if needed, so it falls into the following block | |
806 // and branches to the not-following block. | |
807 | |
808 // Check for the next block being in succs[0]. We are going to branch | |
809 // to succs[0], so we want the fall-thru case as the next block in | |
810 // succs[1]. | |
811 if (bnext == bs0) { | |
812 // Fall-thru case in succs[0], so flip targets in succs map | |
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813 Block* tbs0 = block->_succs[0]; |
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814 Block* tbs1 = block->_succs[1]; |
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815 block->_succs.map(0, tbs1); |
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816 block->_succs.map(1, tbs0); |
0 | 817 // Flip projection for each target |
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818 ProjNode* tmp = proj0; |
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819 proj0 = proj1; |
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820 proj1 = tmp; |
0 | 821 |
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822 } else if(bnext != bs1) { |
418 | 823 // Need a double-branch |
0 | 824 // The existing conditional branch need not change. |
825 // Add a unconditional branch to the false target. | |
826 // Alas, it must appear in its own block and adding a | |
827 // block this late in the game is complicated. Sigh. | |
828 insert_goto_at(i, 1); | |
829 } | |
830 | |
831 // Make sure we TRUE branch to the target | |
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832 if (proj0->Opcode() == Op_IfFalse) { |
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833 iff->as_MachIf()->negate(); |
418 | 834 } |
0 | 835 |
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836 block->pop_node(); // Remove IfFalse & IfTrue projections |
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837 block->pop_node(); |
0 | 838 |
839 } else { | |
840 // Multi-exit block, e.g. a switch statement | |
841 // But we don't need to do anything here | |
842 } | |
843 } // End of for all blocks | |
844 } | |
845 | |
846 | |
847 #ifndef PRODUCT | |
848 void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const { | |
849 const Node *x = end->is_block_proj(); | |
850 assert( x, "not a CFG" ); | |
851 | |
852 // Do not visit this block again | |
853 if( visited.test_set(x->_idx) ) return; | |
854 | |
855 // Skip through this block | |
856 const Node *p = x; | |
857 do { | |
858 p = p->in(0); // Move control forward | |
859 assert( !p->is_block_proj() || p->is_Root(), "not a CFG" ); | |
860 } while( !p->is_block_start() ); | |
861 | |
862 // Recursively visit | |
12023 | 863 for (uint i = 1; i < p->req(); i++) { |
864 _dump_cfg(p->in(i), visited); | |
865 } | |
0 | 866 |
867 // Dump the block | |
12023 | 868 get_block_for_node(p)->dump(this); |
0 | 869 } |
870 | |
871 void PhaseCFG::dump( ) const { | |
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872 tty->print("\n--- CFG --- %d BBs\n", number_of_blocks()); |
12023 | 873 if (_blocks.size()) { // Did we do basic-block layout? |
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874 for (uint i = 0; i < number_of_blocks(); i++) { |
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875 const Block* block = get_block(i); |
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876 block->dump(this); |
12023 | 877 } |
0 | 878 } else { // Else do it with a DFS |
12023 | 879 VectorSet visited(_block_arena); |
0 | 880 _dump_cfg(_root,visited); |
881 } | |
882 } | |
883 | |
884 void PhaseCFG::dump_headers() { | |
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885 for (uint i = 0; i < number_of_blocks(); i++) { |
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886 Block* block = get_block(i); |
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887 if (block != NULL) { |
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888 block->dump_head(this); |
12023 | 889 } |
0 | 890 } |
891 } | |
892 | |
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893 void PhaseCFG::verify() const { |
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894 #ifdef ASSERT |
0 | 895 // Verify sane CFG |
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896 for (uint i = 0; i < number_of_blocks(); i++) { |
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897 Block* block = get_block(i); |
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898 uint cnt = block->number_of_nodes(); |
0 | 899 uint j; |
4115 | 900 for (j = 0; j < cnt; j++) { |
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901 Node *n = block->get_node(j); |
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902 assert(get_block_for_node(n) == block, ""); |
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903 if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) { |
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904 assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block"); |
0 | 905 } |
4115 | 906 for (uint k = 0; k < n->req(); k++) { |
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907 Node *def = n->in(k); |
4115 | 908 if (def && def != n) { |
12023 | 909 assert(get_block_for_node(def) || def->is_Con(), "must have block; constants for debug info ok"); |
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910 // Verify that instructions in the block is in correct order. |
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911 // Uses must follow their definition if they are at the same block. |
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912 // Mostly done to check that MachSpillCopy nodes are placed correctly |
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913 // when CreateEx node is moved in build_ifg_physical(). |
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914 if (get_block_for_node(def) == block && !(block->head()->is_Loop() && n->is_Phi()) && |
566
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915 // See (+++) comment in reg_split.cpp |
4115 | 916 !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) { |
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917 bool is_loop = false; |
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918 if (n->is_Phi()) { |
4115 | 919 for (uint l = 1; l < def->req(); l++) { |
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920 if (n == def->in(l)) { |
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921 is_loop = true; |
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922 break; // Some kind of loop |
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923 } |
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924 } |
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925 } |
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926 assert(is_loop || block->find_node(def) < j, "uses must follow definitions"); |
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927 } |
0 | 928 } |
929 } | |
930 } | |
931 | |
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932 j = block->end_idx(); |
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933 Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj(); |
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934 assert(bp, "last instruction must be a block proj"); |
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935 assert(bp == block->get_node(j), "wrong number of successors for this block"); |
4115 | 936 if (bp->is_Catch()) { |
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937 while (block->get_node(--j)->is_MachProj()) { |
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938 ; |
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939 } |
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940 assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call"); |
4115 | 941 } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) { |
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942 assert(block->_num_succs == 2, "Conditional branch must have two targets"); |
0 | 943 } |
944 } | |
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945 #endif |
0 | 946 } |
947 #endif | |
948 | |
949 UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) { | |
950 Copy::zero_to_bytes( _indices, sizeof(uint)*max ); | |
951 } | |
952 | |
953 void UnionFind::extend( uint from_idx, uint to_idx ) { | |
954 _nesting.check(); | |
955 if( from_idx >= _max ) { | |
956 uint size = 16; | |
957 while( size <= from_idx ) size <<=1; | |
958 _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size ); | |
959 _max = size; | |
960 } | |
961 while( _cnt <= from_idx ) _indices[_cnt++] = 0; | |
962 _indices[from_idx] = to_idx; | |
963 } | |
964 | |
965 void UnionFind::reset( uint max ) { | |
966 assert( max <= max_uint, "Must fit within uint" ); | |
967 // Force the Union-Find mapping to be at least this large | |
968 extend(max,0); | |
969 // Initialize to be the ID mapping. | |
418 | 970 for( uint i=0; i<max; i++ ) map(i,i); |
0 | 971 } |
972 | |
973 // Straight out of Tarjan's union-find algorithm | |
974 uint UnionFind::Find_compress( uint idx ) { | |
975 uint cur = idx; | |
976 uint next = lookup(cur); | |
977 while( next != cur ) { // Scan chain of equivalences | |
978 assert( next < cur, "always union smaller" ); | |
979 cur = next; // until find a fixed-point | |
980 next = lookup(cur); | |
981 } | |
982 // Core of union-find algorithm: update chain of | |
983 // equivalences to be equal to the root. | |
984 while( idx != next ) { | |
985 uint tmp = lookup(idx); | |
986 map(idx, next); | |
987 idx = tmp; | |
988 } | |
989 return idx; | |
990 } | |
991 | |
992 // Like Find above, but no path compress, so bad asymptotic behavior | |
993 uint UnionFind::Find_const( uint idx ) const { | |
994 if( idx == 0 ) return idx; // Ignore the zero idx | |
995 // Off the end? This can happen during debugging dumps | |
996 // when data structures have not finished being updated. | |
997 if( idx >= _max ) return idx; | |
998 uint next = lookup(idx); | |
999 while( next != idx ) { // Scan chain of equivalences | |
1000 idx = next; // until find a fixed-point | |
1001 next = lookup(idx); | |
1002 } | |
1003 return next; | |
1004 } | |
1005 | |
1006 // union 2 sets together. | |
1007 void UnionFind::Union( uint idx1, uint idx2 ) { | |
1008 uint src = Find(idx1); | |
1009 uint dst = Find(idx2); | |
1010 assert( src, "" ); | |
1011 assert( dst, "" ); | |
1012 assert( src < _max, "oob" ); | |
1013 assert( dst < _max, "oob" ); | |
1014 assert( src < dst, "always union smaller" ); | |
1015 map(dst,src); | |
1016 } | |
418 | 1017 |
1018 #ifndef PRODUCT | |
1019 void Trace::dump( ) const { | |
1020 tty->print_cr("Trace (freq %f)", first_block()->_freq); | |
1021 for (Block *b = first_block(); b != NULL; b = next(b)) { | |
1022 tty->print(" B%d", b->_pre_order); | |
1023 if (b->head()->is_Loop()) { | |
1024 tty->print(" (L%d)", b->compute_loop_alignment()); | |
1025 } | |
1026 if (b->has_loop_alignment()) { | |
1027 tty->print(" (T%d)", b->code_alignment()); | |
1028 } | |
1029 } | |
1030 tty->cr(); | |
1031 } | |
1032 | |
1033 void CFGEdge::dump( ) const { | |
1034 tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ", | |
1035 from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct); | |
1036 switch(state()) { | |
1037 case connected: | |
1038 tty->print("connected"); | |
1039 break; | |
1040 case open: | |
1041 tty->print("open"); | |
1042 break; | |
1043 case interior: | |
1044 tty->print("interior"); | |
1045 break; | |
1046 } | |
1047 if (infrequent()) { | |
1048 tty->print(" infrequent"); | |
1049 } | |
1050 tty->cr(); | |
1051 } | |
1052 #endif | |
1053 | |
1054 // Comparison function for edges | |
1055 static int edge_order(CFGEdge **e0, CFGEdge **e1) { | |
1056 float freq0 = (*e0)->freq(); | |
1057 float freq1 = (*e1)->freq(); | |
1058 if (freq0 != freq1) { | |
1059 return freq0 > freq1 ? -1 : 1; | |
1060 } | |
1061 | |
1062 int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo; | |
1063 int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo; | |
1064 | |
1065 return dist1 - dist0; | |
1066 } | |
1067 | |
1068 // Comparison function for edges | |
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1069 extern "C" int trace_frequency_order(const void *p0, const void *p1) { |
418 | 1070 Trace *tr0 = *(Trace **) p0; |
1071 Trace *tr1 = *(Trace **) p1; | |
1072 Block *b0 = tr0->first_block(); | |
1073 Block *b1 = tr1->first_block(); | |
1074 | |
1075 // The trace of connector blocks goes at the end; | |
1076 // we only expect one such trace | |
1077 if (b0->is_connector() != b1->is_connector()) { | |
1078 return b1->is_connector() ? -1 : 1; | |
1079 } | |
1080 | |
1081 // Pull more frequently executed blocks to the beginning | |
1082 float freq0 = b0->_freq; | |
1083 float freq1 = b1->_freq; | |
1084 if (freq0 != freq1) { | |
1085 return freq0 > freq1 ? -1 : 1; | |
1086 } | |
1087 | |
1088 int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo; | |
1089 | |
1090 return diff; | |
1091 } | |
1092 | |
1093 // Find edges of interest, i.e, those which can fall through. Presumes that | |
1094 // edges which don't fall through are of low frequency and can be generally | |
1095 // ignored. Initialize the list of traces. | |
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1096 void PhaseBlockLayout::find_edges() { |
418 | 1097 // Walk the blocks, creating edges and Traces |
1098 uint i; | |
1099 Trace *tr = NULL; | |
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1100 for (i = 0; i < _cfg.number_of_blocks(); i++) { |
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1101 Block* b = _cfg.get_block(i); |
418 | 1102 tr = new Trace(b, next, prev); |
1103 traces[tr->id()] = tr; | |
1104 | |
1105 // All connector blocks should be at the end of the list | |
1106 if (b->is_connector()) break; | |
1107 | |
1108 // If this block and the next one have a one-to-one successor | |
1109 // predecessor relationship, simply append the next block | |
1110 int nfallthru = b->num_fall_throughs(); | |
1111 while (nfallthru == 1 && | |
1112 b->succ_fall_through(0)) { | |
1113 Block *n = b->_succs[0]; | |
1114 | |
1115 // Skip over single-entry connector blocks, we don't want to | |
1116 // add them to the trace. | |
1117 while (n->is_connector() && n->num_preds() == 1) { | |
1118 n = n->_succs[0]; | |
1119 } | |
1120 | |
1121 // We see a merge point, so stop search for the next block | |
1122 if (n->num_preds() != 1) break; | |
1123 | |
1124 i++; | |
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1125 assert(n = _cfg.get_block(i), "expecting next block"); |
418 | 1126 tr->append(n); |
1127 uf->map(n->_pre_order, tr->id()); | |
1128 traces[n->_pre_order] = NULL; | |
1129 nfallthru = b->num_fall_throughs(); | |
1130 b = n; | |
1131 } | |
1132 | |
1133 if (nfallthru > 0) { | |
1134 // Create a CFGEdge for each outgoing | |
1135 // edge that could be a fall-through. | |
1136 for (uint j = 0; j < b->_num_succs; j++ ) { | |
1137 if (b->succ_fall_through(j)) { | |
1138 Block *target = b->non_connector_successor(j); | |
1139 float freq = b->_freq * b->succ_prob(j); | |
1140 int from_pct = (int) ((100 * freq) / b->_freq); | |
1141 int to_pct = (int) ((100 * freq) / target->_freq); | |
1142 edges->append(new CFGEdge(b, target, freq, from_pct, to_pct)); | |
1143 } | |
1144 } | |
1145 } | |
1146 } | |
1147 | |
1148 // Group connector blocks into one trace | |
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1149 for (i++; i < _cfg.number_of_blocks(); i++) { |
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1150 Block *b = _cfg.get_block(i); |
418 | 1151 assert(b->is_connector(), "connector blocks at the end"); |
1152 tr->append(b); | |
1153 uf->map(b->_pre_order, tr->id()); | |
1154 traces[b->_pre_order] = NULL; | |
1155 } | |
1156 } | |
1157 | |
1158 // Union two traces together in uf, and null out the trace in the list | |
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1159 void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) { |
418 | 1160 uint old_id = old_trace->id(); |
1161 uint updated_id = updated_trace->id(); | |
1162 | |
1163 uint lo_id = updated_id; | |
1164 uint hi_id = old_id; | |
1165 | |
1166 // If from is greater than to, swap values to meet | |
1167 // UnionFind guarantee. | |
1168 if (updated_id > old_id) { | |
1169 lo_id = old_id; | |
1170 hi_id = updated_id; | |
1171 | |
1172 // Fix up the trace ids | |
1173 traces[lo_id] = traces[updated_id]; | |
1174 updated_trace->set_id(lo_id); | |
1175 } | |
1176 | |
1177 // Union the lower with the higher and remove the pointer | |
1178 // to the higher. | |
1179 uf->Union(lo_id, hi_id); | |
1180 traces[hi_id] = NULL; | |
1181 } | |
1182 | |
1183 // Append traces together via the most frequently executed edges | |
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1184 void PhaseBlockLayout::grow_traces() { |
418 | 1185 // Order the edges, and drive the growth of Traces via the most |
1186 // frequently executed edges. | |
1187 edges->sort(edge_order); | |
1188 for (int i = 0; i < edges->length(); i++) { | |
1189 CFGEdge *e = edges->at(i); | |
1190 | |
1191 if (e->state() != CFGEdge::open) continue; | |
1192 | |
1193 Block *src_block = e->from(); | |
1194 Block *targ_block = e->to(); | |
1195 | |
1196 // Don't grow traces along backedges? | |
1197 if (!BlockLayoutRotateLoops) { | |
1198 if (targ_block->_rpo <= src_block->_rpo) { | |
1199 targ_block->set_loop_alignment(targ_block); | |
1200 continue; | |
1201 } | |
1202 } | |
1203 | |
1204 Trace *src_trace = trace(src_block); | |
1205 Trace *targ_trace = trace(targ_block); | |
1206 | |
1207 // If the edge in question can join two traces at their ends, | |
1208 // append one trace to the other. | |
1209 if (src_trace->last_block() == src_block) { | |
1210 if (src_trace == targ_trace) { | |
1211 e->set_state(CFGEdge::interior); | |
1212 if (targ_trace->backedge(e)) { | |
1213 // Reset i to catch any newly eligible edge | |
1214 // (Or we could remember the first "open" edge, and reset there) | |
1215 i = 0; | |
1216 } | |
1217 } else if (targ_trace->first_block() == targ_block) { | |
1218 e->set_state(CFGEdge::connected); | |
1219 src_trace->append(targ_trace); | |
1220 union_traces(src_trace, targ_trace); | |
1221 } | |
1222 } | |
1223 } | |
1224 } | |
1225 | |
1226 // Embed one trace into another, if the fork or join points are sufficiently | |
1227 // balanced. | |
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1228 void PhaseBlockLayout::merge_traces(bool fall_thru_only) { |
418 | 1229 // Walk the edge list a another time, looking at unprocessed edges. |
1230 // Fold in diamonds | |
1231 for (int i = 0; i < edges->length(); i++) { | |
1232 CFGEdge *e = edges->at(i); | |
1233 | |
1234 if (e->state() != CFGEdge::open) continue; | |
1235 if (fall_thru_only) { | |
1236 if (e->infrequent()) continue; | |
1237 } | |
1238 | |
1239 Block *src_block = e->from(); | |
1240 Trace *src_trace = trace(src_block); | |
1241 bool src_at_tail = src_trace->last_block() == src_block; | |
1242 | |
1243 Block *targ_block = e->to(); | |
1244 Trace *targ_trace = trace(targ_block); | |
1245 bool targ_at_start = targ_trace->first_block() == targ_block; | |
1246 | |
1247 if (src_trace == targ_trace) { | |
1248 // This may be a loop, but we can't do much about it. | |
1249 e->set_state(CFGEdge::interior); | |
1250 continue; | |
1251 } | |
1252 | |
1253 if (fall_thru_only) { | |
1254 // If the edge links the middle of two traces, we can't do anything. | |
1255 // Mark the edge and continue. | |
1256 if (!src_at_tail & !targ_at_start) { | |
1257 continue; | |
1258 } | |
1259 | |
1260 // Don't grow traces along backedges? | |
1261 if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) { | |
1262 continue; | |
1263 } | |
1264 | |
1265 // If both ends of the edge are available, why didn't we handle it earlier? | |
1266 assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier."); | |
1267 | |
1268 if (targ_at_start) { | |
1269 // Insert the "targ" trace in the "src" trace if the insertion point | |
1270 // is a two way branch. | |
1271 // Better profitability check possible, but may not be worth it. | |
1272 // Someday, see if the this "fork" has an associated "join"; | |
1273 // then make a policy on merging this trace at the fork or join. | |
1274 // For example, other things being equal, it may be better to place this | |
1275 // trace at the join point if the "src" trace ends in a two-way, but | |
1276 // the insertion point is one-way. | |
1277 assert(src_block->num_fall_throughs() == 2, "unexpected diamond"); | |
1278 e->set_state(CFGEdge::connected); | |
1279 src_trace->insert_after(src_block, targ_trace); | |
1280 union_traces(src_trace, targ_trace); | |
1281 } else if (src_at_tail) { | |
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1282 if (src_trace != trace(_cfg.get_root_block())) { |
418 | 1283 e->set_state(CFGEdge::connected); |
1284 targ_trace->insert_before(targ_block, src_trace); | |
1285 union_traces(targ_trace, src_trace); | |
1286 } | |
1287 } | |
1288 } else if (e->state() == CFGEdge::open) { | |
1289 // Append traces, even without a fall-thru connection. | |
605 | 1290 // But leave root entry at the beginning of the block list. |
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1291 if (targ_trace != trace(_cfg.get_root_block())) { |
418 | 1292 e->set_state(CFGEdge::connected); |
1293 src_trace->append(targ_trace); | |
1294 union_traces(src_trace, targ_trace); | |
1295 } | |
1296 } | |
1297 } | |
1298 } | |
1299 | |
1300 // Order the sequence of the traces in some desirable way, and fixup the | |
1301 // jumps at the end of each block. | |
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1302 void PhaseBlockLayout::reorder_traces(int count) { |
418 | 1303 ResourceArea *area = Thread::current()->resource_area(); |
1304 Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count); | |
1305 Block_List worklist; | |
1306 int new_count = 0; | |
1307 | |
1308 // Compact the traces. | |
1309 for (int i = 0; i < count; i++) { | |
1310 Trace *tr = traces[i]; | |
1311 if (tr != NULL) { | |
1312 new_traces[new_count++] = tr; | |
1313 } | |
1314 } | |
1315 | |
1316 // The entry block should be first on the new trace list. | |
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1317 Trace *tr = trace(_cfg.get_root_block()); |
418 | 1318 assert(tr == new_traces[0], "entry trace misplaced"); |
1319 | |
1320 // Sort the new trace list by frequency | |
1321 qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order); | |
1322 | |
1323 // Patch up the successor blocks | |
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1324 _cfg.clear_blocks(); |
418 | 1325 for (int i = 0; i < new_count; i++) { |
1326 Trace *tr = new_traces[i]; | |
1327 if (tr != NULL) { | |
1328 tr->fixup_blocks(_cfg); | |
1329 } | |
1330 } | |
1331 } | |
1332 | |
1333 // Order basic blocks based on frequency | |
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1334 PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg) |
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1335 : Phase(BlockLayout) |
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1336 , _cfg(cfg) { |
418 | 1337 ResourceMark rm; |
1338 ResourceArea *area = Thread::current()->resource_area(); | |
1339 | |
1340 // List of traces | |
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1341 int size = _cfg.number_of_blocks() + 1; |
418 | 1342 traces = NEW_ARENA_ARRAY(area, Trace *, size); |
1343 memset(traces, 0, size*sizeof(Trace*)); | |
1344 next = NEW_ARENA_ARRAY(area, Block *, size); | |
1345 memset(next, 0, size*sizeof(Block *)); | |
1346 prev = NEW_ARENA_ARRAY(area, Block *, size); | |
1347 memset(prev , 0, size*sizeof(Block *)); | |
1348 | |
1349 // List of edges | |
1350 edges = new GrowableArray<CFGEdge*>; | |
1351 | |
1352 // Mapping block index --> block_trace | |
1353 uf = new UnionFind(size); | |
1354 uf->reset(size); | |
1355 | |
1356 // Find edges and create traces. | |
1357 find_edges(); | |
1358 | |
1359 // Grow traces at their ends via most frequent edges. | |
1360 grow_traces(); | |
1361 | |
1362 // Merge one trace into another, but only at fall-through points. | |
1363 // This may make diamonds and other related shapes in a trace. | |
1364 merge_traces(true); | |
1365 | |
1366 // Run merge again, allowing two traces to be catenated, even if | |
1367 // one does not fall through into the other. This appends loosely | |
1368 // related traces to be near each other. | |
1369 merge_traces(false); | |
1370 | |
1371 // Re-order all the remaining traces by frequency | |
1372 reorder_traces(size); | |
1373 | |
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1374 assert(_cfg.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink"); |
418 | 1375 } |
1376 | |
1377 | |
1378 // Edge e completes a loop in a trace. If the target block is head of the | |
1379 // loop, rotate the loop block so that the loop ends in a conditional branch. | |
1380 bool Trace::backedge(CFGEdge *e) { | |
1381 bool loop_rotated = false; | |
1382 Block *src_block = e->from(); | |
1383 Block *targ_block = e->to(); | |
1384 | |
1385 assert(last_block() == src_block, "loop discovery at back branch"); | |
1386 if (first_block() == targ_block) { | |
1387 if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) { | |
1388 // Find the last block in the trace that has a conditional | |
1389 // branch. | |
1390 Block *b; | |
1391 for (b = last_block(); b != NULL; b = prev(b)) { | |
1392 if (b->num_fall_throughs() == 2) { | |
1393 break; | |
1394 } | |
1395 } | |
1396 | |
1397 if (b != last_block() && b != NULL) { | |
1398 loop_rotated = true; | |
1399 | |
1400 // Rotate the loop by doing two-part linked-list surgery. | |
1401 append(first_block()); | |
1402 break_loop_after(b); | |
1403 } | |
1404 } | |
1405 | |
1406 // Backbranch to the top of a trace | |
605 | 1407 // Scroll forward through the trace from the targ_block. If we find |
418 | 1408 // a loop head before another loop top, use the the loop head alignment. |
1409 for (Block *b = targ_block; b != NULL; b = next(b)) { | |
1410 if (b->has_loop_alignment()) { | |
1411 break; | |
1412 } | |
1413 if (b->head()->is_Loop()) { | |
1414 targ_block = b; | |
1415 break; | |
1416 } | |
1417 } | |
1418 | |
1419 first_block()->set_loop_alignment(targ_block); | |
1420 | |
1421 } else { | |
1422 // Backbranch into the middle of a trace | |
1423 targ_block->set_loop_alignment(targ_block); | |
1424 } | |
1425 | |
1426 return loop_rotated; | |
1427 } | |
1428 | |
1429 // push blocks onto the CFG list | |
1430 // ensure that blocks have the correct two-way branch sense | |
1431 void Trace::fixup_blocks(PhaseCFG &cfg) { | |
1432 Block *last = last_block(); | |
1433 for (Block *b = first_block(); b != NULL; b = next(b)) { | |
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1434 cfg.add_block(b); |
418 | 1435 if (!b->is_connector()) { |
1436 int nfallthru = b->num_fall_throughs(); | |
1437 if (b != last) { | |
1438 if (nfallthru == 2) { | |
1439 // Ensure that the sense of the branch is correct | |
1440 Block *bnext = next(b); | |
1441 Block *bs0 = b->non_connector_successor(0); | |
1442 | |
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1443 MachNode *iff = b->get_node(b->number_of_nodes() - 3)->as_Mach(); |
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1444 ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj(); |
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1445 ProjNode *proj1 = b->get_node(b->number_of_nodes() - 1)->as_Proj(); |
418 | 1446 |
1447 if (bnext == bs0) { | |
1448 // Fall-thru case in succs[0], should be in succs[1] | |
1449 | |
1450 // Flip targets in _succs map | |
1451 Block *tbs0 = b->_succs[0]; | |
1452 Block *tbs1 = b->_succs[1]; | |
1453 b->_succs.map( 0, tbs1 ); | |
1454 b->_succs.map( 1, tbs0 ); | |
1455 | |
1456 // Flip projections to match targets | |
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1457 b->map_node(proj1, b->number_of_nodes() - 2); |
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1458 b->map_node(proj0, b->number_of_nodes() - 1); |
418 | 1459 } |
1460 } | |
1461 } | |
1462 } | |
1463 } | |
1464 } |