1 /*
2 * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "c1/c1_Compilation.hpp"
27 #include "c1/c1_FrameMap.hpp"
28 #include "c1/c1_GraphBuilder.hpp"
29 #include "c1/c1_IR.hpp"
30 #include "c1/c1_InstructionPrinter.hpp"
31 #include "c1/c1_Optimizer.hpp"
32 #include "utilities/bitMap.inline.hpp"
33
34
35 // Implementation of XHandlers
36 //
37 // Note: This code could eventually go away if we are
38 // just using the ciExceptionHandlerStream.
39
40 XHandlers::XHandlers(ciMethod* method) : _list(method->exception_table_length()) {
41 ciExceptionHandlerStream s(method);
42 while (!s.is_done()) {
43 _list.append(new XHandler(s.handler()));
44 s.next();
45 }
46 assert(s.count() == method->exception_table_length(), "exception table lengths inconsistent");
47 }
48
49 // deep copy of all XHandler contained in list
50 XHandlers::XHandlers(XHandlers* other) :
51 _list(other->length())
52 {
53 for (int i = 0; i < other->length(); i++) {
54 _list.append(new XHandler(other->handler_at(i)));
55 }
56 }
57
58 // Returns whether a particular exception type can be caught. Also
59 // returns true if klass is unloaded or any exception handler
60 // classes are unloaded. type_is_exact indicates whether the throw
61 // is known to be exactly that class or it might throw a subtype.
62 bool XHandlers::could_catch(ciInstanceKlass* klass, bool type_is_exact) const {
63 // the type is unknown so be conservative
64 if (!klass->is_loaded()) {
65 return true;
66 }
67
68 for (int i = 0; i < length(); i++) {
69 XHandler* handler = handler_at(i);
70 if (handler->is_catch_all()) {
71 // catch of ANY
72 return true;
73 }
74 ciInstanceKlass* handler_klass = handler->catch_klass();
75 // if it's unknown it might be catchable
76 if (!handler_klass->is_loaded()) {
77 return true;
78 }
79 // if the throw type is definitely a subtype of the catch type
80 // then it can be caught.
81 if (klass->is_subtype_of(handler_klass)) {
82 return true;
83 }
84 if (!type_is_exact) {
85 // If the type isn't exactly known then it can also be caught by
86 // catch statements where the inexact type is a subtype of the
87 // catch type.
88 // given: foo extends bar extends Exception
89 // throw bar can be caught by catch foo, catch bar, and catch
90 // Exception, however it can't be caught by any handlers without
91 // bar in its type hierarchy.
92 if (handler_klass->is_subtype_of(klass)) {
93 return true;
94 }
95 }
96 }
97
98 return false;
99 }
100
101
102 bool XHandlers::equals(XHandlers* others) const {
103 if (others == NULL) return false;
104 if (length() != others->length()) return false;
105
106 for (int i = 0; i < length(); i++) {
107 if (!handler_at(i)->equals(others->handler_at(i))) return false;
108 }
109 return true;
110 }
111
112 bool XHandler::equals(XHandler* other) const {
113 assert(entry_pco() != -1 && other->entry_pco() != -1, "must have entry_pco");
114
115 if (entry_pco() != other->entry_pco()) return false;
116 if (scope_count() != other->scope_count()) return false;
117 if (_desc != other->_desc) return false;
118
119 assert(entry_block() == other->entry_block(), "entry_block must be equal when entry_pco is equal");
120 return true;
121 }
122
123
124 // Implementation of IRScope
125 BlockBegin* IRScope::build_graph(Compilation* compilation, int osr_bci) {
126 GraphBuilder gm(compilation, this);
127 NOT_PRODUCT(if (PrintValueNumbering && Verbose) gm.print_stats());
128 if (compilation->bailed_out()) return NULL;
129 return gm.start();
130 }
131
132
133 IRScope::IRScope(Compilation* compilation, IRScope* caller, int caller_bci, ciMethod* method, int osr_bci, bool create_graph)
134 : _callees(2)
135 , _compilation(compilation)
136 , _requires_phi_function(method->max_locals())
137 {
138 _caller = caller;
139 _level = caller == NULL ? 0 : caller->level() + 1;
140 _method = method;
141 _xhandlers = new XHandlers(method);
142 _number_of_locks = 0;
143 _monitor_pairing_ok = method->has_balanced_monitors();
144 _start = NULL;
145
146 if (osr_bci == -1) {
147 _requires_phi_function.clear();
148 } else {
149 // selective creation of phi functions is not possibel in osr-methods
150 _requires_phi_function.set_range(0, method->max_locals());
151 }
152
153 assert(method->holder()->is_loaded() , "method holder must be loaded");
154
155 // build graph if monitor pairing is ok
156 if (create_graph && monitor_pairing_ok()) _start = build_graph(compilation, osr_bci);
157 }
158
159
160 int IRScope::max_stack() const {
161 int my_max = method()->max_stack();
162 int callee_max = 0;
163 for (int i = 0; i < number_of_callees(); i++) {
164 callee_max = MAX2(callee_max, callee_no(i)->max_stack());
165 }
166 return my_max + callee_max;
167 }
168
169
170 bool IRScopeDebugInfo::should_reexecute() {
171 ciMethod* cur_method = scope()->method();
172 int cur_bci = bci();
173 if (cur_method != NULL && cur_bci != SynchronizationEntryBCI) {
174 Bytecodes::Code code = cur_method->java_code_at_bci(cur_bci);
175 return Interpreter::bytecode_should_reexecute(code);
176 } else
177 return false;
178 }
179
180
181 // Implementation of CodeEmitInfo
182
183 // Stack must be NON-null
184 CodeEmitInfo::CodeEmitInfo(ValueStack* stack, XHandlers* exception_handlers)
185 : _scope(stack->scope())
186 , _scope_debug_info(NULL)
187 , _oop_map(NULL)
188 , _stack(stack)
189 , _exception_handlers(exception_handlers)
190 , _is_method_handle_invoke(false) {
191 assert(_stack != NULL, "must be non null");
192 }
193
194
195 CodeEmitInfo::CodeEmitInfo(CodeEmitInfo* info, ValueStack* stack)
196 : _scope(info->_scope)
197 , _exception_handlers(NULL)
198 , _scope_debug_info(NULL)
199 , _oop_map(NULL)
200 , _stack(stack == NULL ? info->_stack : stack)
201 , _is_method_handle_invoke(info->_is_method_handle_invoke) {
202
203 // deep copy of exception handlers
204 if (info->_exception_handlers != NULL) {
205 _exception_handlers = new XHandlers(info->_exception_handlers);
206 }
207 }
208
209
210 void CodeEmitInfo::record_debug_info(DebugInformationRecorder* recorder, int pc_offset) {
211 // record the safepoint before recording the debug info for enclosing scopes
212 recorder->add_safepoint(pc_offset, _oop_map->deep_copy());
213 _scope_debug_info->record_debug_info(recorder, pc_offset, true/*topmost*/, _is_method_handle_invoke);
214 recorder->end_safepoint(pc_offset);
215 }
216
217
218 void CodeEmitInfo::add_register_oop(LIR_Opr opr) {
219 assert(_oop_map != NULL, "oop map must already exist");
220 assert(opr->is_single_cpu(), "should not call otherwise");
221
222 VMReg name = frame_map()->regname(opr);
223 _oop_map->set_oop(name);
224 }
225
226
227
228
229 // Implementation of IR
230
231 IR::IR(Compilation* compilation, ciMethod* method, int osr_bci) :
232 _locals_size(in_WordSize(-1))
233 , _num_loops(0) {
234 // setup IR fields
235 _compilation = compilation;
236 _top_scope = new IRScope(compilation, NULL, -1, method, osr_bci, true);
237 _code = NULL;
238 }
239
240
241 void IR::optimize() {
242 Optimizer opt(this);
243 if (!compilation()->profile_branches()) {
244 if (DoCEE) {
245 opt.eliminate_conditional_expressions();
246 #ifndef PRODUCT
247 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after CEE"); print(true); }
248 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after CEE"); print(false); }
249 #endif
250 }
251 if (EliminateBlocks) {
252 opt.eliminate_blocks();
253 #ifndef PRODUCT
254 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after block elimination"); print(true); }
255 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after block elimination"); print(false); }
256 #endif
257 }
258 }
259 if (EliminateNullChecks) {
260 opt.eliminate_null_checks();
261 #ifndef PRODUCT
262 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after null check elimination"); print(true); }
263 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after null check elimination"); print(false); }
264 #endif
265 }
266 }
267
268
269 static int sort_pairs(BlockPair** a, BlockPair** b) {
270 if ((*a)->from() == (*b)->from()) {
271 return (*a)->to()->block_id() - (*b)->to()->block_id();
272 } else {
273 return (*a)->from()->block_id() - (*b)->from()->block_id();
274 }
275 }
276
277
278 class CriticalEdgeFinder: public BlockClosure {
279 BlockPairList blocks;
280 IR* _ir;
281
282 public:
283 CriticalEdgeFinder(IR* ir): _ir(ir) {}
284 void block_do(BlockBegin* bb) {
285 BlockEnd* be = bb->end();
286 int nos = be->number_of_sux();
287 if (nos >= 2) {
288 for (int i = 0; i < nos; i++) {
289 BlockBegin* sux = be->sux_at(i);
290 if (sux->number_of_preds() >= 2) {
291 blocks.append(new BlockPair(bb, sux));
292 }
293 }
294 }
295 }
296
297 void split_edges() {
298 BlockPair* last_pair = NULL;
299 blocks.sort(sort_pairs);
300 for (int i = 0; i < blocks.length(); i++) {
301 BlockPair* pair = blocks.at(i);
302 if (last_pair != NULL && pair->is_same(last_pair)) continue;
303 BlockBegin* from = pair->from();
304 BlockBegin* to = pair->to();
305 BlockBegin* split = from->insert_block_between(to);
306 #ifndef PRODUCT
307 if ((PrintIR || PrintIR1) && Verbose) {
308 tty->print_cr("Split critical edge B%d -> B%d (new block B%d)",
309 from->block_id(), to->block_id(), split->block_id());
310 }
311 #endif
312 last_pair = pair;
313 }
314 }
315 };
316
317 void IR::split_critical_edges() {
318 CriticalEdgeFinder cef(this);
319
320 iterate_preorder(&cef);
321 cef.split_edges();
322 }
323
324
325 class UseCountComputer: public ValueVisitor, BlockClosure {
326 private:
327 void visit(Value* n) {
328 // Local instructions and Phis for expression stack values at the
329 // start of basic blocks are not added to the instruction list
330 if (!(*n)->is_linked()&& (*n)->can_be_linked()) {
331 assert(false, "a node was not appended to the graph");
332 Compilation::current()->bailout("a node was not appended to the graph");
333 }
334 // use n's input if not visited before
335 if (!(*n)->is_pinned() && !(*n)->has_uses()) {
336 // note: a) if the instruction is pinned, it will be handled by compute_use_count
337 // b) if the instruction has uses, it was touched before
338 // => in both cases we don't need to update n's values
339 uses_do(n);
340 }
341 // use n
342 (*n)->_use_count++;
343 }
344
345 Values* worklist;
346 int depth;
347 enum {
348 max_recurse_depth = 20
349 };
350
351 void uses_do(Value* n) {
352 depth++;
353 if (depth > max_recurse_depth) {
354 // don't allow the traversal to recurse too deeply
355 worklist->push(*n);
356 } else {
357 (*n)->input_values_do(this);
358 // special handling for some instructions
359 if ((*n)->as_BlockEnd() != NULL) {
360 // note on BlockEnd:
361 // must 'use' the stack only if the method doesn't
362 // terminate, however, in those cases stack is empty
363 (*n)->state_values_do(this);
364 }
365 }
366 depth--;
367 }
368
369 void block_do(BlockBegin* b) {
370 depth = 0;
371 // process all pinned nodes as the roots of expression trees
372 for (Instruction* n = b; n != NULL; n = n->next()) {
373 if (n->is_pinned()) uses_do(&n);
374 }
375 assert(depth == 0, "should have counted back down");
376
377 // now process any unpinned nodes which recursed too deeply
378 while (worklist->length() > 0) {
379 Value t = worklist->pop();
380 if (!t->is_pinned()) {
381 // compute the use count
382 uses_do(&t);
383
384 // pin the instruction so that LIRGenerator doesn't recurse
385 // too deeply during it's evaluation.
386 t->pin();
387 }
388 }
389 assert(depth == 0, "should have counted back down");
390 }
391
392 UseCountComputer() {
393 worklist = new Values();
394 depth = 0;
395 }
396
397 public:
398 static void compute(BlockList* blocks) {
399 UseCountComputer ucc;
400 blocks->iterate_backward(&ucc);
401 }
402 };
403
404
405 // helper macro for short definition of trace-output inside code
406 #ifndef PRODUCT
407 #define TRACE_LINEAR_SCAN(level, code) \
408 if (TraceLinearScanLevel >= level) { \
409 code; \
410 }
411 #else
412 #define TRACE_LINEAR_SCAN(level, code)
413 #endif
414
415 class ComputeLinearScanOrder : public StackObj {
416 private:
417 int _max_block_id; // the highest block_id of a block
418 int _num_blocks; // total number of blocks (smaller than _max_block_id)
419 int _num_loops; // total number of loops
420 bool _iterative_dominators;// method requires iterative computation of dominatiors
421
422 BlockList* _linear_scan_order; // the resulting list of blocks in correct order
423
424 BitMap _visited_blocks; // used for recursive processing of blocks
425 BitMap _active_blocks; // used for recursive processing of blocks
426 BitMap _dominator_blocks; // temproary BitMap used for computation of dominator
427 intArray _forward_branches; // number of incoming forward branches for each block
428 BlockList _loop_end_blocks; // list of all loop end blocks collected during count_edges
429 BitMap2D _loop_map; // two-dimensional bit set: a bit is set if a block is contained in a loop
430 BlockList _work_list; // temporary list (used in mark_loops and compute_order)
431
432 Compilation* _compilation;
433
434 // accessors for _visited_blocks and _active_blocks
435 void init_visited() { _active_blocks.clear(); _visited_blocks.clear(); }
436 bool is_visited(BlockBegin* b) const { return _visited_blocks.at(b->block_id()); }
437 bool is_active(BlockBegin* b) const { return _active_blocks.at(b->block_id()); }
438 void set_visited(BlockBegin* b) { assert(!is_visited(b), "already set"); _visited_blocks.set_bit(b->block_id()); }
439 void set_active(BlockBegin* b) { assert(!is_active(b), "already set"); _active_blocks.set_bit(b->block_id()); }
440 void clear_active(BlockBegin* b) { assert(is_active(b), "not already"); _active_blocks.clear_bit(b->block_id()); }
441
442 // accessors for _forward_branches
443 void inc_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) + 1); }
444 int dec_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) - 1); return _forward_branches.at(b->block_id()); }
445
446 // accessors for _loop_map
447 bool is_block_in_loop (int loop_idx, BlockBegin* b) const { return _loop_map.at(loop_idx, b->block_id()); }
448 void set_block_in_loop (int loop_idx, BlockBegin* b) { _loop_map.set_bit(loop_idx, b->block_id()); }
449 void clear_block_in_loop(int loop_idx, int block_id) { _loop_map.clear_bit(loop_idx, block_id); }
450
451 // count edges between blocks
452 void count_edges(BlockBegin* cur, BlockBegin* parent);
453
454 // loop detection
455 void mark_loops();
456 void clear_non_natural_loops(BlockBegin* start_block);
457 void assign_loop_depth(BlockBegin* start_block);
458
459 // computation of final block order
460 BlockBegin* common_dominator(BlockBegin* a, BlockBegin* b);
461 void compute_dominator(BlockBegin* cur, BlockBegin* parent);
462 int compute_weight(BlockBegin* cur);
463 bool ready_for_processing(BlockBegin* cur);
464 void sort_into_work_list(BlockBegin* b);
465 void append_block(BlockBegin* cur);
466 void compute_order(BlockBegin* start_block);
467
468 // fixup of dominators for non-natural loops
469 bool compute_dominators_iter();
470 void compute_dominators();
471
472 // debug functions
473 NOT_PRODUCT(void print_blocks();)
474 DEBUG_ONLY(void verify();)
475
476 Compilation* compilation() const { return _compilation; }
477 public:
478 ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block);
479
480 // accessors for final result
481 BlockList* linear_scan_order() const { return _linear_scan_order; }
482 int num_loops() const { return _num_loops; }
483 };
484
485
486 ComputeLinearScanOrder::ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block) :
487 _max_block_id(BlockBegin::number_of_blocks()),
488 _num_blocks(0),
489 _num_loops(0),
490 _iterative_dominators(false),
491 _visited_blocks(_max_block_id),
492 _active_blocks(_max_block_id),
493 _dominator_blocks(_max_block_id),
494 _forward_branches(_max_block_id, 0),
495 _loop_end_blocks(8),
496 _work_list(8),
497 _linear_scan_order(NULL), // initialized later with correct size
498 _loop_map(0, 0), // initialized later with correct size
499 _compilation(c)
500 {
501 TRACE_LINEAR_SCAN(2, "***** computing linear-scan block order");
502
503 init_visited();
504 count_edges(start_block, NULL);
505
506 if (compilation()->is_profiling()) {
507 compilation()->method()->method_data()->set_compilation_stats(_num_loops, _num_blocks);
508 }
509
510 if (_num_loops > 0) {
511 mark_loops();
512 clear_non_natural_loops(start_block);
513 assign_loop_depth(start_block);
514 }
515
516 compute_order(start_block);
517 compute_dominators();
518
519 NOT_PRODUCT(print_blocks());
520 DEBUG_ONLY(verify());
521 }
522
523
524 // Traverse the CFG:
525 // * count total number of blocks
526 // * count all incoming edges and backward incoming edges
527 // * number loop header blocks
528 // * create a list with all loop end blocks
529 void ComputeLinearScanOrder::count_edges(BlockBegin* cur, BlockBegin* parent) {
530 TRACE_LINEAR_SCAN(3, tty->print_cr("Enter count_edges for block B%d coming from B%d", cur->block_id(), parent != NULL ? parent->block_id() : -1));
531 assert(cur->dominator() == NULL, "dominator already initialized");
532
533 if (is_active(cur)) {
534 TRACE_LINEAR_SCAN(3, tty->print_cr("backward branch"));
535 assert(is_visited(cur), "block must be visisted when block is active");
536 assert(parent != NULL, "must have parent");
537
538 cur->set(BlockBegin::linear_scan_loop_header_flag);
539 cur->set(BlockBegin::backward_branch_target_flag);
540
541 parent->set(BlockBegin::linear_scan_loop_end_flag);
542
543 // When a loop header is also the start of an exception handler, then the backward branch is
544 // an exception edge. Because such edges are usually critical edges which cannot be split, the
545 // loop must be excluded here from processing.
546 if (cur->is_set(BlockBegin::exception_entry_flag)) {
547 // Make sure that dominators are correct in this weird situation
548 _iterative_dominators = true;
549 return;
550 }
551 assert(parent->number_of_sux() == 1 && parent->sux_at(0) == cur,
552 "loop end blocks must have one successor (critical edges are split)");
553
554 _loop_end_blocks.append(parent);
555 return;
556 }
557
558 // increment number of incoming forward branches
559 inc_forward_branches(cur);
560
561 if (is_visited(cur)) {
562 TRACE_LINEAR_SCAN(3, tty->print_cr("block already visited"));
563 return;
564 }
565
566 _num_blocks++;
567 set_visited(cur);
568 set_active(cur);
569
570 // recursive call for all successors
571 int i;
572 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
573 count_edges(cur->sux_at(i), cur);
574 }
575 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
576 count_edges(cur->exception_handler_at(i), cur);
577 }
578
579 clear_active(cur);
580
581 // Each loop has a unique number.
582 // When multiple loops are nested, assign_loop_depth assumes that the
583 // innermost loop has the lowest number. This is guaranteed by setting
584 // the loop number after the recursive calls for the successors above
585 // have returned.
586 if (cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
587 assert(cur->loop_index() == -1, "cannot set loop-index twice");
588 TRACE_LINEAR_SCAN(3, tty->print_cr("Block B%d is loop header of loop %d", cur->block_id(), _num_loops));
589
590 cur->set_loop_index(_num_loops);
591 _num_loops++;
592 }
593
594 TRACE_LINEAR_SCAN(3, tty->print_cr("Finished count_edges for block B%d", cur->block_id()));
595 }
596
597
598 void ComputeLinearScanOrder::mark_loops() {
599 TRACE_LINEAR_SCAN(3, tty->print_cr("----- marking loops"));
600
601 _loop_map = BitMap2D(_num_loops, _max_block_id);
602 _loop_map.clear();
603
604 for (int i = _loop_end_blocks.length() - 1; i >= 0; i--) {
605 BlockBegin* loop_end = _loop_end_blocks.at(i);
606 BlockBegin* loop_start = loop_end->sux_at(0);
607 int loop_idx = loop_start->loop_index();
608
609 TRACE_LINEAR_SCAN(3, tty->print_cr("Processing loop from B%d to B%d (loop %d):", loop_start->block_id(), loop_end->block_id(), loop_idx));
610 assert(loop_end->is_set(BlockBegin::linear_scan_loop_end_flag), "loop end flag must be set");
611 assert(loop_end->number_of_sux() == 1, "incorrect number of successors");
612 assert(loop_start->is_set(BlockBegin::linear_scan_loop_header_flag), "loop header flag must be set");
613 assert(loop_idx >= 0 && loop_idx < _num_loops, "loop index not set");
614 assert(_work_list.is_empty(), "work list must be empty before processing");
615
616 // add the end-block of the loop to the working list
617 _work_list.push(loop_end);
618 set_block_in_loop(loop_idx, loop_end);
619 do {
620 BlockBegin* cur = _work_list.pop();
621
622 TRACE_LINEAR_SCAN(3, tty->print_cr(" processing B%d", cur->block_id()));
623 assert(is_block_in_loop(loop_idx, cur), "bit in loop map must be set when block is in work list");
624
625 // recursive processing of all predecessors ends when start block of loop is reached
626 if (cur != loop_start && !cur->is_set(BlockBegin::osr_entry_flag)) {
627 for (int j = cur->number_of_preds() - 1; j >= 0; j--) {
628 BlockBegin* pred = cur->pred_at(j);
629
630 if (!is_block_in_loop(loop_idx, pred) /*&& !pred->is_set(BlockBeginosr_entry_flag)*/) {
631 // this predecessor has not been processed yet, so add it to work list
632 TRACE_LINEAR_SCAN(3, tty->print_cr(" pushing B%d", pred->block_id()));
633 _work_list.push(pred);
634 set_block_in_loop(loop_idx, pred);
635 }
636 }
637 }
638 } while (!_work_list.is_empty());
639 }
640 }
641
642
643 // check for non-natural loops (loops where the loop header does not dominate
644 // all other loop blocks = loops with mulitple entries).
645 // such loops are ignored
646 void ComputeLinearScanOrder::clear_non_natural_loops(BlockBegin* start_block) {
647 for (int i = _num_loops - 1; i >= 0; i--) {
648 if (is_block_in_loop(i, start_block)) {
649 // loop i contains the entry block of the method
650 // -> this is not a natural loop, so ignore it
651 TRACE_LINEAR_SCAN(2, tty->print_cr("Loop %d is non-natural, so it is ignored", i));
652
653 for (int block_id = _max_block_id - 1; block_id >= 0; block_id--) {
654 clear_block_in_loop(i, block_id);
655 }
656 _iterative_dominators = true;
657 }
658 }
659 }
660
661 void ComputeLinearScanOrder::assign_loop_depth(BlockBegin* start_block) {
662 TRACE_LINEAR_SCAN(3, "----- computing loop-depth and weight");
663 init_visited();
664
665 assert(_work_list.is_empty(), "work list must be empty before processing");
666 _work_list.append(start_block);
667
668 do {
669 BlockBegin* cur = _work_list.pop();
670
671 if (!is_visited(cur)) {
672 set_visited(cur);
673 TRACE_LINEAR_SCAN(4, tty->print_cr("Computing loop depth for block B%d", cur->block_id()));
674
675 // compute loop-depth and loop-index for the block
676 assert(cur->loop_depth() == 0, "cannot set loop-depth twice");
677 int i;
678 int loop_depth = 0;
679 int min_loop_idx = -1;
680 for (i = _num_loops - 1; i >= 0; i--) {
681 if (is_block_in_loop(i, cur)) {
682 loop_depth++;
683 min_loop_idx = i;
684 }
685 }
686 cur->set_loop_depth(loop_depth);
687 cur->set_loop_index(min_loop_idx);
688
689 // append all unvisited successors to work list
690 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
691 _work_list.append(cur->sux_at(i));
692 }
693 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
694 _work_list.append(cur->exception_handler_at(i));
695 }
696 }
697 } while (!_work_list.is_empty());
698 }
699
700
701 BlockBegin* ComputeLinearScanOrder::common_dominator(BlockBegin* a, BlockBegin* b) {
702 assert(a != NULL && b != NULL, "must have input blocks");
703
704 _dominator_blocks.clear();
705 while (a != NULL) {
706 _dominator_blocks.set_bit(a->block_id());
707 assert(a->dominator() != NULL || a == _linear_scan_order->at(0), "dominator must be initialized");
708 a = a->dominator();
709 }
710 while (b != NULL && !_dominator_blocks.at(b->block_id())) {
711 assert(b->dominator() != NULL || b == _linear_scan_order->at(0), "dominator must be initialized");
712 b = b->dominator();
713 }
714
715 assert(b != NULL, "could not find dominator");
716 return b;
717 }
718
719 void ComputeLinearScanOrder::compute_dominator(BlockBegin* cur, BlockBegin* parent) {
720 if (cur->dominator() == NULL) {
721 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: initializing dominator of B%d to B%d", cur->block_id(), parent->block_id()));
722 cur->set_dominator(parent);
723
724 } else if (!(cur->is_set(BlockBegin::linear_scan_loop_header_flag) && parent->is_set(BlockBegin::linear_scan_loop_end_flag))) {
725 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: computing dominator of B%d: common dominator of B%d and B%d is B%d", cur->block_id(), parent->block_id(), cur->dominator()->block_id(), common_dominator(cur->dominator(), parent)->block_id()));
726 assert(cur->number_of_preds() > 1, "");
727 cur->set_dominator(common_dominator(cur->dominator(), parent));
728 }
729 }
730
731
732 int ComputeLinearScanOrder::compute_weight(BlockBegin* cur) {
733 BlockBegin* single_sux = NULL;
734 if (cur->number_of_sux() == 1) {
735 single_sux = cur->sux_at(0);
736 }
737
738 // limit loop-depth to 15 bit (only for security reason, it will never be so big)
739 int weight = (cur->loop_depth() & 0x7FFF) << 16;
740
741 // general macro for short definition of weight flags
742 // the first instance of INC_WEIGHT_IF has the highest priority
743 int cur_bit = 15;
744 #define INC_WEIGHT_IF(condition) if ((condition)) { weight |= (1 << cur_bit); } cur_bit--;
745
746 // this is necessery for the (very rare) case that two successing blocks have
747 // the same loop depth, but a different loop index (can happen for endless loops
748 // with exception handlers)
749 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_header_flag));
750
751 // loop end blocks (blocks that end with a backward branch) are added
752 // after all other blocks of the loop.
753 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_end_flag));
754
755 // critical edge split blocks are prefered because than they have a bigger
756 // proability to be completely empty
757 INC_WEIGHT_IF(cur->is_set(BlockBegin::critical_edge_split_flag));
758
759 // exceptions should not be thrown in normal control flow, so these blocks
760 // are added as late as possible
761 INC_WEIGHT_IF(cur->end()->as_Throw() == NULL && (single_sux == NULL || single_sux->end()->as_Throw() == NULL));
762 INC_WEIGHT_IF(cur->end()->as_Return() == NULL && (single_sux == NULL || single_sux->end()->as_Return() == NULL));
763
764 // exceptions handlers are added as late as possible
765 INC_WEIGHT_IF(!cur->is_set(BlockBegin::exception_entry_flag));
766
767 // guarantee that weight is > 0
768 weight |= 1;
769
770 #undef INC_WEIGHT_IF
771 assert(cur_bit >= 0, "too many flags");
772 assert(weight > 0, "weight cannot become negative");
773
774 return weight;
775 }
776
777 bool ComputeLinearScanOrder::ready_for_processing(BlockBegin* cur) {
778 // Discount the edge just traveled.
779 // When the number drops to zero, all forward branches were processed
780 if (dec_forward_branches(cur) != 0) {
781 return false;
782 }
783
784 assert(_linear_scan_order->index_of(cur) == -1, "block already processed (block can be ready only once)");
785 assert(_work_list.index_of(cur) == -1, "block already in work-list (block can be ready only once)");
786 return true;
787 }
788
789 void ComputeLinearScanOrder::sort_into_work_list(BlockBegin* cur) {
790 assert(_work_list.index_of(cur) == -1, "block already in work list");
791
792 int cur_weight = compute_weight(cur);
793
794 // the linear_scan_number is used to cache the weight of a block
795 cur->set_linear_scan_number(cur_weight);
796
797 #ifndef PRODUCT
798 if (StressLinearScan) {
799 _work_list.insert_before(0, cur);
800 return;
801 }
802 #endif
803
804 _work_list.append(NULL); // provide space for new element
805
806 int insert_idx = _work_list.length() - 1;
807 while (insert_idx > 0 && _work_list.at(insert_idx - 1)->linear_scan_number() > cur_weight) {
808 _work_list.at_put(insert_idx, _work_list.at(insert_idx - 1));
809 insert_idx--;
810 }
811 _work_list.at_put(insert_idx, cur);
812
813 TRACE_LINEAR_SCAN(3, tty->print_cr("Sorted B%d into worklist. new worklist:", cur->block_id()));
814 TRACE_LINEAR_SCAN(3, for (int i = 0; i < _work_list.length(); i++) tty->print_cr("%8d B%2d weight:%6x", i, _work_list.at(i)->block_id(), _work_list.at(i)->linear_scan_number()));
815
816 #ifdef ASSERT
817 for (int i = 0; i < _work_list.length(); i++) {
818 assert(_work_list.at(i)->linear_scan_number() > 0, "weight not set");
819 assert(i == 0 || _work_list.at(i - 1)->linear_scan_number() <= _work_list.at(i)->linear_scan_number(), "incorrect order in worklist");
820 }
821 #endif
822 }
823
824 void ComputeLinearScanOrder::append_block(BlockBegin* cur) {
825 TRACE_LINEAR_SCAN(3, tty->print_cr("appending block B%d (weight 0x%6x) to linear-scan order", cur->block_id(), cur->linear_scan_number()));
826 assert(_linear_scan_order->index_of(cur) == -1, "cannot add the same block twice");
827
828 // currently, the linear scan order and code emit order are equal.
829 // therefore the linear_scan_number and the weight of a block must also
830 // be equal.
831 cur->set_linear_scan_number(_linear_scan_order->length());
832 _linear_scan_order->append(cur);
833 }
834
835 void ComputeLinearScanOrder::compute_order(BlockBegin* start_block) {
836 TRACE_LINEAR_SCAN(3, "----- computing final block order");
837
838 // the start block is always the first block in the linear scan order
839 _linear_scan_order = new BlockList(_num_blocks);
840 append_block(start_block);
841
842 assert(start_block->end()->as_Base() != NULL, "start block must end with Base-instruction");
843 BlockBegin* std_entry = ((Base*)start_block->end())->std_entry();
844 BlockBegin* osr_entry = ((Base*)start_block->end())->osr_entry();
845
846 BlockBegin* sux_of_osr_entry = NULL;
847 if (osr_entry != NULL) {
848 // special handling for osr entry:
849 // ignore the edge between the osr entry and its successor for processing
850 // the osr entry block is added manually below
851 assert(osr_entry->number_of_sux() == 1, "osr entry must have exactly one successor");
852 assert(osr_entry->sux_at(0)->number_of_preds() >= 2, "sucessor of osr entry must have two predecessors (otherwise it is not present in normal control flow");
853
854 sux_of_osr_entry = osr_entry->sux_at(0);
855 dec_forward_branches(sux_of_osr_entry);
856
857 compute_dominator(osr_entry, start_block);
858 _iterative_dominators = true;
859 }
860 compute_dominator(std_entry, start_block);
861
862 // start processing with standard entry block
863 assert(_work_list.is_empty(), "list must be empty before processing");
864
865 if (ready_for_processing(std_entry)) {
866 sort_into_work_list(std_entry);
867 } else {
868 assert(false, "the std_entry must be ready for processing (otherwise, the method has no start block)");
869 }
870
871 do {
872 BlockBegin* cur = _work_list.pop();
873
874 if (cur == sux_of_osr_entry) {
875 // the osr entry block is ignored in normal processing, it is never added to the
876 // work list. Instead, it is added as late as possible manually here.
877 append_block(osr_entry);
878 compute_dominator(cur, osr_entry);
879 }
880 append_block(cur);
881
882 int i;
883 int num_sux = cur->number_of_sux();
884 // changed loop order to get "intuitive" order of if- and else-blocks
885 for (i = 0; i < num_sux; i++) {
886 BlockBegin* sux = cur->sux_at(i);
887 compute_dominator(sux, cur);
888 if (ready_for_processing(sux)) {
889 sort_into_work_list(sux);
890 }
891 }
892 num_sux = cur->number_of_exception_handlers();
893 for (i = 0; i < num_sux; i++) {
894 BlockBegin* sux = cur->exception_handler_at(i);
895 compute_dominator(sux, cur);
896 if (ready_for_processing(sux)) {
897 sort_into_work_list(sux);
898 }
899 }
900 } while (_work_list.length() > 0);
901 }
902
903
904 bool ComputeLinearScanOrder::compute_dominators_iter() {
905 bool changed = false;
906 int num_blocks = _linear_scan_order->length();
907
908 assert(_linear_scan_order->at(0)->dominator() == NULL, "must not have dominator");
909 assert(_linear_scan_order->at(0)->number_of_preds() == 0, "must not have predecessors");
910 for (int i = 1; i < num_blocks; i++) {
911 BlockBegin* block = _linear_scan_order->at(i);
912
913 BlockBegin* dominator = block->pred_at(0);
914 int num_preds = block->number_of_preds();
915 for (int i = 1; i < num_preds; i++) {
916 dominator = common_dominator(dominator, block->pred_at(i));
917 }
918
919 if (dominator != block->dominator()) {
920 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: updating dominator of B%d from B%d to B%d", block->block_id(), block->dominator()->block_id(), dominator->block_id()));
921
922 block->set_dominator(dominator);
923 changed = true;
924 }
925 }
926 return changed;
927 }
928
929 void ComputeLinearScanOrder::compute_dominators() {
930 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing dominators (iterative computation reqired: %d)", _iterative_dominators));
931
932 // iterative computation of dominators is only required for methods with non-natural loops
933 // and OSR-methods. For all other methods, the dominators computed when generating the
934 // linear scan block order are correct.
935 if (_iterative_dominators) {
936 do {
937 TRACE_LINEAR_SCAN(1, tty->print_cr("DOM: next iteration of fix-point calculation"));
938 } while (compute_dominators_iter());
939 }
940
941 // check that dominators are correct
942 assert(!compute_dominators_iter(), "fix point not reached");
943 }
944
945
946 #ifndef PRODUCT
947 void ComputeLinearScanOrder::print_blocks() {
948 if (TraceLinearScanLevel >= 2) {
949 tty->print_cr("----- loop information:");
950 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
951 BlockBegin* cur = _linear_scan_order->at(block_idx);
952
953 tty->print("%4d: B%2d: ", cur->linear_scan_number(), cur->block_id());
954 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
955 tty->print ("%d ", is_block_in_loop(loop_idx, cur));
956 }
957 tty->print_cr(" -> loop_index: %2d, loop_depth: %2d", cur->loop_index(), cur->loop_depth());
958 }
959 }
960
961 if (TraceLinearScanLevel >= 1) {
962 tty->print_cr("----- linear-scan block order:");
963 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
964 BlockBegin* cur = _linear_scan_order->at(block_idx);
965 tty->print("%4d: B%2d loop: %2d depth: %2d", cur->linear_scan_number(), cur->block_id(), cur->loop_index(), cur->loop_depth());
966
967 tty->print(cur->is_set(BlockBegin::exception_entry_flag) ? " ex" : " ");
968 tty->print(cur->is_set(BlockBegin::critical_edge_split_flag) ? " ce" : " ");
969 tty->print(cur->is_set(BlockBegin::linear_scan_loop_header_flag) ? " lh" : " ");
970 tty->print(cur->is_set(BlockBegin::linear_scan_loop_end_flag) ? " le" : " ");
971
972 if (cur->dominator() != NULL) {
973 tty->print(" dom: B%d ", cur->dominator()->block_id());
974 } else {
975 tty->print(" dom: NULL ");
976 }
977
978 if (cur->number_of_preds() > 0) {
979 tty->print(" preds: ");
980 for (int j = 0; j < cur->number_of_preds(); j++) {
981 BlockBegin* pred = cur->pred_at(j);
982 tty->print("B%d ", pred->block_id());
983 }
984 }
985 if (cur->number_of_sux() > 0) {
986 tty->print(" sux: ");
987 for (int j = 0; j < cur->number_of_sux(); j++) {
988 BlockBegin* sux = cur->sux_at(j);
989 tty->print("B%d ", sux->block_id());
990 }
991 }
992 if (cur->number_of_exception_handlers() > 0) {
993 tty->print(" ex: ");
994 for (int j = 0; j < cur->number_of_exception_handlers(); j++) {
995 BlockBegin* ex = cur->exception_handler_at(j);
996 tty->print("B%d ", ex->block_id());
997 }
998 }
999 tty->cr();
1000 }
1001 }
1002 }
1003 #endif
1004
1005 #ifdef ASSERT
1006 void ComputeLinearScanOrder::verify() {
1007 assert(_linear_scan_order->length() == _num_blocks, "wrong number of blocks in list");
1008
1009 if (StressLinearScan) {
1010 // blocks are scrambled when StressLinearScan is used
1011 return;
1012 }
1013
1014 // check that all successors of a block have a higher linear-scan-number
1015 // and that all predecessors of a block have a lower linear-scan-number
1016 // (only backward branches of loops are ignored)
1017 int i;
1018 for (i = 0; i < _linear_scan_order->length(); i++) {
1019 BlockBegin* cur = _linear_scan_order->at(i);
1020
1021 assert(cur->linear_scan_number() == i, "incorrect linear_scan_number");
1022 assert(cur->linear_scan_number() >= 0 && cur->linear_scan_number() == _linear_scan_order->index_of(cur), "incorrect linear_scan_number");
1023
1024 int j;
1025 for (j = cur->number_of_sux() - 1; j >= 0; j--) {
1026 BlockBegin* sux = cur->sux_at(j);
1027
1028 assert(sux->linear_scan_number() >= 0 && sux->linear_scan_number() == _linear_scan_order->index_of(sux), "incorrect linear_scan_number");
1029 if (!cur->is_set(BlockBegin::linear_scan_loop_end_flag)) {
1030 assert(cur->linear_scan_number() < sux->linear_scan_number(), "invalid order");
1031 }
1032 if (cur->loop_depth() == sux->loop_depth()) {
1033 assert(cur->loop_index() == sux->loop_index() || sux->is_set(BlockBegin::linear_scan_loop_header_flag), "successing blocks with same loop depth must have same loop index");
1034 }
1035 }
1036
1037 for (j = cur->number_of_preds() - 1; j >= 0; j--) {
1038 BlockBegin* pred = cur->pred_at(j);
1039
1040 assert(pred->linear_scan_number() >= 0 && pred->linear_scan_number() == _linear_scan_order->index_of(pred), "incorrect linear_scan_number");
1041 if (!cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
1042 assert(cur->linear_scan_number() > pred->linear_scan_number(), "invalid order");
1043 }
1044 if (cur->loop_depth() == pred->loop_depth()) {
1045 assert(cur->loop_index() == pred->loop_index() || cur->is_set(BlockBegin::linear_scan_loop_header_flag), "successing blocks with same loop depth must have same loop index");
1046 }
1047
1048 assert(cur->dominator()->linear_scan_number() <= cur->pred_at(j)->linear_scan_number(), "dominator must be before predecessors");
1049 }
1050
1051 // check dominator
1052 if (i == 0) {
1053 assert(cur->dominator() == NULL, "first block has no dominator");
1054 } else {
1055 assert(cur->dominator() != NULL, "all but first block must have dominator");
1056 }
1057 assert(cur->number_of_preds() != 1 || cur->dominator() == cur->pred_at(0), "Single predecessor must also be dominator");
1058 }
1059
1060 // check that all loops are continuous
1061 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1062 int block_idx = 0;
1063 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "the first block must not be present in any loop");
1064
1065 // skip blocks before the loop
1066 while (block_idx < _num_blocks && !is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1067 block_idx++;
1068 }
1069 // skip blocks of loop
1070 while (block_idx < _num_blocks && is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1071 block_idx++;
1072 }
1073 // after the first non-loop block, there must not be another loop-block
1074 while (block_idx < _num_blocks) {
1075 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "loop not continuous in linear-scan order");
1076 block_idx++;
1077 }
1078 }
1079 }
1080 #endif
1081
1082
1083 void IR::compute_code() {
1084 assert(is_valid(), "IR must be valid");
1085
1086 ComputeLinearScanOrder compute_order(compilation(), start());
1087 _num_loops = compute_order.num_loops();
1088 _code = compute_order.linear_scan_order();
1089 }
1090
1091
1092 void IR::compute_use_counts() {
1093 // make sure all values coming out of this block get evaluated.
1094 int num_blocks = _code->length();
1095 for (int i = 0; i < num_blocks; i++) {
1096 _code->at(i)->end()->state()->pin_stack_for_linear_scan();
1097 }
1098
1099 // compute use counts
1100 UseCountComputer::compute(_code);
1101 }
1102
1103
1104 void IR::iterate_preorder(BlockClosure* closure) {
1105 assert(is_valid(), "IR must be valid");
1106 start()->iterate_preorder(closure);
1107 }
1108
1109
1110 void IR::iterate_postorder(BlockClosure* closure) {
1111 assert(is_valid(), "IR must be valid");
1112 start()->iterate_postorder(closure);
1113 }
1114
1115 void IR::iterate_linear_scan_order(BlockClosure* closure) {
1116 linear_scan_order()->iterate_forward(closure);
1117 }
1118
1119
1120 #ifndef PRODUCT
1121 class BlockPrinter: public BlockClosure {
1122 private:
1123 InstructionPrinter* _ip;
1124 bool _cfg_only;
1125 bool _live_only;
1126
1127 public:
1128 BlockPrinter(InstructionPrinter* ip, bool cfg_only, bool live_only = false) {
1129 _ip = ip;
1130 _cfg_only = cfg_only;
1131 _live_only = live_only;
1132 }
1133
1134 virtual void block_do(BlockBegin* block) {
1135 if (_cfg_only) {
1136 _ip->print_instr(block); tty->cr();
1137 } else {
1138 block->print_block(*_ip, _live_only);
1139 }
1140 }
1141 };
1142
1143
1144 void IR::print(BlockBegin* start, bool cfg_only, bool live_only) {
1145 ttyLocker ttyl;
1146 InstructionPrinter ip(!cfg_only);
1147 BlockPrinter bp(&ip, cfg_only, live_only);
1148 start->iterate_preorder(&bp);
1149 tty->cr();
1150 }
1151
1152 void IR::print(bool cfg_only, bool live_only) {
1153 if (is_valid()) {
1154 print(start(), cfg_only, live_only);
1155 } else {
1156 tty->print_cr("invalid IR");
1157 }
1158 }
1159
1160
1161 define_array(BlockListArray, BlockList*)
1162 define_stack(BlockListList, BlockListArray)
1163
1164 class PredecessorValidator : public BlockClosure {
1165 private:
1166 BlockListList* _predecessors;
1167 BlockList* _blocks;
1168
1169 static int cmp(BlockBegin** a, BlockBegin** b) {
1170 return (*a)->block_id() - (*b)->block_id();
1171 }
1172
1173 public:
1174 PredecessorValidator(IR* hir) {
1175 ResourceMark rm;
1176 _predecessors = new BlockListList(BlockBegin::number_of_blocks(), NULL);
1177 _blocks = new BlockList();
1178
1179 int i;
1180 hir->start()->iterate_preorder(this);
1181 if (hir->code() != NULL) {
1182 assert(hir->code()->length() == _blocks->length(), "must match");
1183 for (i = 0; i < _blocks->length(); i++) {
1184 assert(hir->code()->contains(_blocks->at(i)), "should be in both lists");
1185 }
1186 }
1187
1188 for (i = 0; i < _blocks->length(); i++) {
1189 BlockBegin* block = _blocks->at(i);
1190 BlockList* preds = _predecessors->at(block->block_id());
1191 if (preds == NULL) {
1192 assert(block->number_of_preds() == 0, "should be the same");
1193 continue;
1194 }
1195
1196 // clone the pred list so we can mutate it
1197 BlockList* pred_copy = new BlockList();
1198 int j;
1199 for (j = 0; j < block->number_of_preds(); j++) {
1200 pred_copy->append(block->pred_at(j));
1201 }
1202 // sort them in the same order
1203 preds->sort(cmp);
1204 pred_copy->sort(cmp);
1205 int length = MIN2(preds->length(), block->number_of_preds());
1206 for (j = 0; j < block->number_of_preds(); j++) {
1207 assert(preds->at(j) == pred_copy->at(j), "must match");
1208 }
1209
1210 assert(preds->length() == block->number_of_preds(), "should be the same");
1211 }
1212 }
1213
1214 virtual void block_do(BlockBegin* block) {
1215 _blocks->append(block);
1216 BlockEnd* be = block->end();
1217 int n = be->number_of_sux();
1218 int i;
1219 for (i = 0; i < n; i++) {
1220 BlockBegin* sux = be->sux_at(i);
1221 assert(!sux->is_set(BlockBegin::exception_entry_flag), "must not be xhandler");
1222
1223 BlockList* preds = _predecessors->at_grow(sux->block_id(), NULL);
1224 if (preds == NULL) {
1225 preds = new BlockList();
1226 _predecessors->at_put(sux->block_id(), preds);
1227 }
1228 preds->append(block);
1229 }
1230
1231 n = block->number_of_exception_handlers();
1232 for (i = 0; i < n; i++) {
1233 BlockBegin* sux = block->exception_handler_at(i);
1234 assert(sux->is_set(BlockBegin::exception_entry_flag), "must be xhandler");
1235
1236 BlockList* preds = _predecessors->at_grow(sux->block_id(), NULL);
1237 if (preds == NULL) {
1238 preds = new BlockList();
1239 _predecessors->at_put(sux->block_id(), preds);
1240 }
1241 preds->append(block);
1242 }
1243 }
1244 };
1245
1246 void IR::verify() {
1247 #ifdef ASSERT
1248 PredecessorValidator pv(this);
1249 #endif
1250 }
1251
1252 #endif // PRODUCT
1253
1254 void SubstitutionResolver::visit(Value* v) {
1255 Value v0 = *v;
1256 if (v0) {
1257 Value vs = v0->subst();
1258 if (vs != v0) {
1259 *v = v0->subst();
1260 }
1261 }
1262 }
1263
1264 #ifdef ASSERT
1265 class SubstitutionChecker: public ValueVisitor {
1266 void visit(Value* v) {
1267 Value v0 = *v;
1268 if (v0) {
1269 Value vs = v0->subst();
1270 assert(vs == v0, "missed substitution");
1271 }
1272 }
1273 };
1274 #endif
1275
1276
1277 void SubstitutionResolver::block_do(BlockBegin* block) {
1278 Instruction* last = NULL;
1279 for (Instruction* n = block; n != NULL;) {
1280 n->values_do(this);
1281 // need to remove this instruction from the instruction stream
1282 if (n->subst() != n) {
1283 assert(last != NULL, "must have last");
1284 last->set_next(n->next());
1285 } else {
1286 last = n;
1287 }
1288 n = last->next();
1289 }
1290
1291 #ifdef ASSERT
1292 SubstitutionChecker check_substitute;
1293 if (block->state()) block->state()->values_do(&check_substitute);
1294 block->block_values_do(&check_substitute);
1295 if (block->end() && block->end()->state()) block->end()->state()->values_do(&check_substitute);
1296 #endif
1297 }