1 /*
2 * Copyright (c) 1999, 2024, 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 "compiler/oopMap.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "utilities/bitMap.inline.hpp"
35
36
37 // Implementation of XHandlers
38 //
39 // Note: This code could eventually go away if we are
40 // just using the ciExceptionHandlerStream.
41
42 XHandlers::XHandlers(ciMethod* method) : _list(method->exception_table_length()) {
43 ciExceptionHandlerStream s(method);
44 while (!s.is_done()) {
45 _list.append(new XHandler(s.handler()));
46 s.next();
47 }
48 assert(s.count() == method->exception_table_length(), "exception table lengths inconsistent");
49 }
50
51 // deep copy of all XHandler contained in list
52 XHandlers::XHandlers(XHandlers* other) :
53 _list(other->length())
54 {
55 for (int i = 0; i < other->length(); i++) {
56 _list.append(new XHandler(other->handler_at(i)));
57 }
58 }
59
60 // Returns whether a particular exception type can be caught. Also
61 // returns true if klass is unloaded or any exception handler
62 // classes are unloaded. type_is_exact indicates whether the throw
63 // is known to be exactly that class or it might throw a subtype.
64 bool XHandlers::could_catch(ciInstanceKlass* klass, bool type_is_exact) const {
65 // the type is unknown so be conservative
66 if (!klass->is_loaded()) {
67 return true;
68 }
69
70 for (int i = 0; i < length(); i++) {
71 XHandler* handler = handler_at(i);
72 if (handler->is_catch_all()) {
73 // catch of ANY
74 return true;
75 }
76 ciInstanceKlass* handler_klass = handler->catch_klass();
77 // if it's unknown it might be catchable
78 if (!handler_klass->is_loaded()) {
79 return true;
80 }
81 // if the throw type is definitely a subtype of the catch type
82 // then it can be caught.
83 if (klass->is_subtype_of(handler_klass)) {
84 return true;
85 }
86 if (!type_is_exact) {
87 // If the type isn't exactly known then it can also be caught by
88 // catch statements where the inexact type is a subtype of the
89 // catch type.
90 // given: foo extends bar extends Exception
91 // throw bar can be caught by catch foo, catch bar, and catch
92 // Exception, however it can't be caught by any handlers without
93 // bar in its type hierarchy.
94 if (handler_klass->is_subtype_of(klass)) {
95 return true;
96 }
97 }
98 }
99
100 return false;
101 }
102
103
104 bool XHandlers::equals(XHandlers* others) const {
105 if (others == nullptr) return false;
106 if (length() != others->length()) return false;
107
108 for (int i = 0; i < length(); i++) {
109 if (!handler_at(i)->equals(others->handler_at(i))) return false;
110 }
111 return true;
112 }
113
114 bool XHandler::equals(XHandler* other) const {
115 assert(entry_pco() != -1 && other->entry_pco() != -1, "must have entry_pco");
116
117 if (entry_pco() != other->entry_pco()) return false;
118 if (scope_count() != other->scope_count()) return false;
119 if (_desc != other->_desc) return false;
120
121 assert(entry_block() == other->entry_block(), "entry_block must be equal when entry_pco is equal");
122 return true;
123 }
124
125
126 // Implementation of IRScope
127 BlockBegin* IRScope::build_graph(Compilation* compilation, int osr_bci) {
128 GraphBuilder gm(compilation, this);
129 NOT_PRODUCT(if (PrintValueNumbering && Verbose) gm.print_stats());
130 if (compilation->bailed_out()) return nullptr;
131 return gm.start();
132 }
133
134
135 IRScope::IRScope(Compilation* compilation, IRScope* caller, int caller_bci, ciMethod* method, int osr_bci, bool create_graph)
136 : _compilation(compilation)
137 , _callees(2)
138 , _requires_phi_function(method->max_locals())
139 {
140 _caller = caller;
141 _level = caller == nullptr ? 0 : caller->level() + 1;
142 _method = method;
143 _xhandlers = new XHandlers(method);
144 _number_of_locks = 0;
145 _monitor_pairing_ok = method->has_balanced_monitors();
146 _wrote_final = false;
147 _wrote_fields = false;
148 _wrote_volatile = false;
149 _start = nullptr;
150
151 if (osr_bci != -1) {
152 // selective creation of phi functions is not possibel in osr-methods
153 _requires_phi_function.set_range(0, method->max_locals());
154 }
155
156 assert(method->holder()->is_loaded() , "method holder must be loaded");
157
158 // build graph if monitor pairing is ok
159 if (create_graph && monitor_pairing_ok()) _start = build_graph(compilation, osr_bci);
160 }
161
162
163 int IRScope::max_stack() const {
164 int my_max = method()->max_stack();
165 int callee_max = 0;
166 for (int i = 0; i < number_of_callees(); i++) {
167 callee_max = MAX2(callee_max, callee_no(i)->max_stack());
168 }
169 return my_max + callee_max;
170 }
171
172
173 bool IRScopeDebugInfo::should_reexecute() {
174 ciMethod* cur_method = scope()->method();
175 int cur_bci = bci();
176 if (cur_method != nullptr && cur_bci != SynchronizationEntryBCI) {
177 Bytecodes::Code code = cur_method->java_code_at_bci(cur_bci);
178 return Interpreter::bytecode_should_reexecute(code);
179 } else
180 return false;
181 }
182
183
184 // Implementation of CodeEmitInfo
185
186 // Stack must be NON-null
187 CodeEmitInfo::CodeEmitInfo(ValueStack* stack, XHandlers* exception_handlers, bool deoptimize_on_exception)
188 : _scope_debug_info(nullptr)
189 , _scope(stack->scope())
190 , _exception_handlers(exception_handlers)
191 , _oop_map(nullptr)
192 , _stack(stack)
193 , _is_method_handle_invoke(false)
194 , _deoptimize_on_exception(deoptimize_on_exception)
195 , _force_reexecute(false) {
196 assert(_stack != nullptr, "must be non null");
197 }
198
199
200 CodeEmitInfo::CodeEmitInfo(CodeEmitInfo* info, ValueStack* stack)
201 : _scope_debug_info(nullptr)
202 , _scope(info->_scope)
203 , _exception_handlers(nullptr)
204 , _oop_map(nullptr)
205 , _stack(stack == nullptr ? info->_stack : stack)
206 , _is_method_handle_invoke(info->_is_method_handle_invoke)
207 , _deoptimize_on_exception(info->_deoptimize_on_exception)
208 , _force_reexecute(info->_force_reexecute) {
209
210 // deep copy of exception handlers
211 if (info->_exception_handlers != nullptr) {
212 _exception_handlers = new XHandlers(info->_exception_handlers);
213 }
214 }
215
216
217 void CodeEmitInfo::record_debug_info(DebugInformationRecorder* recorder, int pc_offset) {
218 // record the safepoint before recording the debug info for enclosing scopes
219 recorder->add_safepoint(pc_offset, _oop_map->deep_copy());
220 bool reexecute = _force_reexecute || _scope_debug_info->should_reexecute();
221 _scope_debug_info->record_debug_info(recorder, pc_offset, reexecute, _is_method_handle_invoke);
222 recorder->end_safepoint(pc_offset);
223 }
224
225
226 void CodeEmitInfo::add_register_oop(LIR_Opr opr) {
227 assert(_oop_map != nullptr, "oop map must already exist");
228 assert(opr->is_single_cpu(), "should not call otherwise");
229
230 VMReg name = frame_map()->regname(opr);
231 _oop_map->set_oop(name);
232 }
233
234 // Mirror the stack size calculation in the deopt code
235 // How much stack space would we need at this point in the program in
236 // case of deoptimization?
237 int CodeEmitInfo::interpreter_frame_size() const {
238 ValueStack* state = _stack;
239 int size = 0;
240 int callee_parameters = 0;
241 int callee_locals = 0;
242 int extra_args = state->scope()->method()->max_stack() - state->stack_size();
243
244 while (state != nullptr) {
245 int locks = state->locks_size();
246 int temps = state->stack_size();
247 bool is_top_frame = (state == _stack);
248 ciMethod* method = state->scope()->method();
249
250 int frame_size = BytesPerWord * Interpreter::size_activation(method->max_stack(),
251 temps + callee_parameters,
252 extra_args,
253 locks,
254 callee_parameters,
255 callee_locals,
256 is_top_frame);
257 size += frame_size;
258
259 callee_parameters = method->size_of_parameters();
260 callee_locals = method->max_locals();
261 extra_args = 0;
262 state = state->caller_state();
263 }
264 return size + Deoptimization::last_frame_adjust(0, callee_locals) * BytesPerWord;
265 }
266
267 // Implementation of IR
268
269 IR::IR(Compilation* compilation, ciMethod* method, int osr_bci) :
270 _num_loops(0) {
271 // setup IR fields
272 _compilation = compilation;
273 _top_scope = new IRScope(compilation, nullptr, -1, method, osr_bci, true);
274 _code = nullptr;
275 }
276
277
278 void IR::optimize_blocks() {
279 Optimizer opt(this);
280 if (!compilation()->profile_branches()) {
281 if (DoCEE) {
282 opt.eliminate_conditional_expressions();
283 #ifndef PRODUCT
284 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after CEE"); print(true); }
285 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after CEE"); print(false); }
286 #endif
287 }
288 if (EliminateBlocks) {
289 opt.eliminate_blocks();
290 #ifndef PRODUCT
291 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after block elimination"); print(true); }
292 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after block elimination"); print(false); }
293 #endif
294 }
295 }
296 }
297
298 void IR::eliminate_null_checks() {
299 Optimizer opt(this);
300 if (EliminateNullChecks) {
301 opt.eliminate_null_checks();
302 #ifndef PRODUCT
303 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after null check elimination"); print(true); }
304 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after null check elimination"); print(false); }
305 #endif
306 }
307 }
308
309 // The functionality of this class is to insert a new block between
310 // the 'from' and 'to' block of a critical edge.
311 // It first collects the block pairs, and then processes them.
312 //
313 // Some instructions may introduce more than one edge between two blocks.
314 // By checking if the current 'to' block sets critical_edge_split_flag
315 // (all new blocks set this flag) we can avoid repeated processing.
316 // This is why BlockPair contains the index rather than the original 'to' block.
317 class CriticalEdgeFinder: public BlockClosure {
318 BlockPairList blocks;
319
320 public:
321 CriticalEdgeFinder(IR* ir) {
322 ir->iterate_preorder(this);
323 }
324
325 void block_do(BlockBegin* bb) {
326 BlockEnd* be = bb->end();
327 int nos = be->number_of_sux();
328 if (nos >= 2) {
329 for (int i = 0; i < nos; i++) {
330 BlockBegin* sux = be->sux_at(i);
331 if (sux->number_of_preds() >= 2) {
332 blocks.append(new BlockPair(bb, i));
333 }
334 }
335 }
336 }
337
338 void split_edges() {
339 for (int i = 0; i < blocks.length(); i++) {
340 BlockPair* pair = blocks.at(i);
341 BlockBegin* from = pair->from();
342 int index = pair->index();
343 BlockBegin* to = from->end()->sux_at(index);
344 if (to->is_set(BlockBegin::critical_edge_split_flag)) {
345 // inserted
346 continue;
347 }
348 BlockBegin* split = from->insert_block_between(to);
349 #ifndef PRODUCT
350 if ((PrintIR || PrintIR1) && Verbose) {
351 tty->print_cr("Split critical edge B%d -> B%d (new block B%d)",
352 from->block_id(), to->block_id(), split->block_id());
353 }
354 #endif
355 }
356 }
357 };
358
359 void IR::split_critical_edges() {
360 CriticalEdgeFinder cef(this);
361 cef.split_edges();
362 }
363
364
365 class UseCountComputer: public ValueVisitor, BlockClosure {
366 private:
367 void visit(Value* n) {
368 // Local instructions and Phis for expression stack values at the
369 // start of basic blocks are not added to the instruction list
370 if (!(*n)->is_linked() && (*n)->can_be_linked()) {
371 assert(false, "a node was not appended to the graph");
372 Compilation::current()->bailout("a node was not appended to the graph");
373 }
374 // use n's input if not visited before
375 if (!(*n)->is_pinned() && !(*n)->has_uses()) {
376 // note: a) if the instruction is pinned, it will be handled by compute_use_count
377 // b) if the instruction has uses, it was touched before
378 // => in both cases we don't need to update n's values
379 uses_do(n);
380 }
381 // use n
382 (*n)->_use_count++;
383 }
384
385 Values* worklist;
386 int depth;
387 enum {
388 max_recurse_depth = 20
389 };
390
391 void uses_do(Value* n) {
392 depth++;
393 if (depth > max_recurse_depth) {
394 // don't allow the traversal to recurse too deeply
395 worklist->push(*n);
396 } else {
397 (*n)->input_values_do(this);
398 // special handling for some instructions
399 if ((*n)->as_BlockEnd() != nullptr) {
400 // note on BlockEnd:
401 // must 'use' the stack only if the method doesn't
402 // terminate, however, in those cases stack is empty
403 (*n)->state_values_do(this);
404 }
405 }
406 depth--;
407 }
408
409 void block_do(BlockBegin* b) {
410 depth = 0;
411 // process all pinned nodes as the roots of expression trees
412 for (Instruction* n = b; n != nullptr; n = n->next()) {
413 if (n->is_pinned()) uses_do(&n);
414 }
415 assert(depth == 0, "should have counted back down");
416
417 // now process any unpinned nodes which recursed too deeply
418 while (worklist->length() > 0) {
419 Value t = worklist->pop();
420 if (!t->is_pinned()) {
421 // compute the use count
422 uses_do(&t);
423
424 // pin the instruction so that LIRGenerator doesn't recurse
425 // too deeply during it's evaluation.
426 t->pin();
427 }
428 }
429 assert(depth == 0, "should have counted back down");
430 }
431
432 UseCountComputer() {
433 worklist = new Values();
434 depth = 0;
435 }
436
437 public:
438 static void compute(BlockList* blocks) {
439 UseCountComputer ucc;
440 blocks->iterate_backward(&ucc);
441 }
442 };
443
444
445 // helper macro for short definition of trace-output inside code
446 #ifdef ASSERT
447 #define TRACE_LINEAR_SCAN(level, code) \
448 if (TraceLinearScanLevel >= level) { \
449 code; \
450 }
451 #else
452 #define TRACE_LINEAR_SCAN(level, code)
453 #endif
454
455 class ComputeLinearScanOrder : public StackObj {
456 private:
457 int _max_block_id; // the highest block_id of a block
458 int _num_blocks; // total number of blocks (smaller than _max_block_id)
459 int _num_loops; // total number of loops
460 bool _iterative_dominators;// method requires iterative computation of dominatiors
461
462 BlockList* _linear_scan_order; // the resulting list of blocks in correct order
463
464 ResourceBitMap _visited_blocks; // used for recursive processing of blocks
465 ResourceBitMap _active_blocks; // used for recursive processing of blocks
466 ResourceBitMap _dominator_blocks; // temporary BitMap used for computation of dominator
467 intArray _forward_branches; // number of incoming forward branches for each block
468 BlockList _loop_end_blocks; // list of all loop end blocks collected during count_edges
469 BitMap2D _loop_map; // two-dimensional bit set: a bit is set if a block is contained in a loop
470 BlockList _work_list; // temporary list (used in mark_loops and compute_order)
471 BlockList _loop_headers;
472
473 Compilation* _compilation;
474
475 // accessors for _visited_blocks and _active_blocks
476 void init_visited() { _active_blocks.clear(); _visited_blocks.clear(); }
477 bool is_visited(BlockBegin* b) const { return _visited_blocks.at(b->block_id()); }
478 bool is_active(BlockBegin* b) const { return _active_blocks.at(b->block_id()); }
479 void set_visited(BlockBegin* b) { assert(!is_visited(b), "already set"); _visited_blocks.set_bit(b->block_id()); }
480 void set_active(BlockBegin* b) { assert(!is_active(b), "already set"); _active_blocks.set_bit(b->block_id()); }
481 void clear_active(BlockBegin* b) { assert(is_active(b), "not already"); _active_blocks.clear_bit(b->block_id()); }
482
483 // accessors for _forward_branches
484 void inc_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) + 1); }
485 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()); }
486
487 // accessors for _loop_map
488 bool is_block_in_loop (int loop_idx, BlockBegin* b) const { return _loop_map.at(loop_idx, b->block_id()); }
489 void set_block_in_loop (int loop_idx, BlockBegin* b) { _loop_map.set_bit(loop_idx, b->block_id()); }
490 void clear_block_in_loop(int loop_idx, int block_id) { _loop_map.clear_bit(loop_idx, block_id); }
491
492 // count edges between blocks
493 void count_edges(BlockBegin* cur, BlockBegin* parent);
494
495 // loop detection
496 void mark_loops();
497 void clear_non_natural_loops(BlockBegin* start_block);
498 void assign_loop_depth(BlockBegin* start_block);
499
500 // computation of final block order
501 BlockBegin* common_dominator(BlockBegin* a, BlockBegin* b);
502 void compute_dominator(BlockBegin* cur, BlockBegin* parent);
503 void compute_dominator_impl(BlockBegin* cur, BlockBegin* parent);
504 int compute_weight(BlockBegin* cur);
505 bool ready_for_processing(BlockBegin* cur);
506 void sort_into_work_list(BlockBegin* b);
507 void append_block(BlockBegin* cur);
508 void compute_order(BlockBegin* start_block);
509
510 // fixup of dominators for non-natural loops
511 bool compute_dominators_iter();
512 void compute_dominators();
513
514 // debug functions
515 DEBUG_ONLY(void print_blocks();)
516 DEBUG_ONLY(void verify();)
517
518 Compilation* compilation() const { return _compilation; }
519 public:
520 ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block);
521
522 // accessors for final result
523 BlockList* linear_scan_order() const { return _linear_scan_order; }
524 int num_loops() const { return _num_loops; }
525 };
526
527
528 ComputeLinearScanOrder::ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block) :
529 _max_block_id(BlockBegin::number_of_blocks()),
530 _num_blocks(0),
531 _num_loops(0),
532 _iterative_dominators(false),
533 _linear_scan_order(nullptr), // initialized later with correct size
534 _visited_blocks(_max_block_id),
535 _active_blocks(_max_block_id),
536 _dominator_blocks(_max_block_id),
537 _forward_branches(_max_block_id, _max_block_id, 0),
538 _loop_end_blocks(8),
539 _loop_map(0), // initialized later with correct size
540 _work_list(8),
541 _compilation(c)
542 {
543 TRACE_LINEAR_SCAN(2, tty->print_cr("***** computing linear-scan block order"));
544
545 count_edges(start_block, nullptr);
546
547 if (compilation()->is_profiling()) {
548 ciMethod *method = compilation()->method();
549 if (!method->is_accessor()) {
550 ciMethodData* md = method->method_data_or_null();
551 assert(md != nullptr, "Sanity");
552 md->set_compilation_stats(_num_loops, _num_blocks);
553 }
554 }
555
556 if (_num_loops > 0) {
557 mark_loops();
558 clear_non_natural_loops(start_block);
559 assign_loop_depth(start_block);
560 }
561
562 compute_order(start_block);
563 compute_dominators();
564
565 DEBUG_ONLY(print_blocks());
566 DEBUG_ONLY(verify());
567 }
568
569
570 // Traverse the CFG:
571 // * count total number of blocks
572 // * count all incoming edges and backward incoming edges
573 // * number loop header blocks
574 // * create a list with all loop end blocks
575 void ComputeLinearScanOrder::count_edges(BlockBegin* cur, BlockBegin* parent) {
576 TRACE_LINEAR_SCAN(3, tty->print_cr("Enter count_edges for block B%d coming from B%d", cur->block_id(), parent != nullptr ? parent->block_id() : -1));
577 assert(cur->dominator() == nullptr, "dominator already initialized");
578
579 if (is_active(cur)) {
580 TRACE_LINEAR_SCAN(3, tty->print_cr("backward branch"));
581 assert(is_visited(cur), "block must be visisted when block is active");
582 assert(parent != nullptr, "must have parent");
583
584 cur->set(BlockBegin::backward_branch_target_flag);
585
586 // When a loop header is also the start of an exception handler, then the backward branch is
587 // an exception edge. Because such edges are usually critical edges which cannot be split, the
588 // loop must be excluded here from processing.
589 if (cur->is_set(BlockBegin::exception_entry_flag)) {
590 // Make sure that dominators are correct in this weird situation
591 _iterative_dominators = true;
592 return;
593 }
594
595 cur->set(BlockBegin::linear_scan_loop_header_flag);
596 parent->set(BlockBegin::linear_scan_loop_end_flag);
597
598 assert(parent->number_of_sux() == 1 && parent->sux_at(0) == cur,
599 "loop end blocks must have one successor (critical edges are split)");
600
601 _loop_end_blocks.append(parent);
602 return;
603 }
604
605 // increment number of incoming forward branches
606 inc_forward_branches(cur);
607
608 if (is_visited(cur)) {
609 TRACE_LINEAR_SCAN(3, tty->print_cr("block already visited"));
610 return;
611 }
612
613 _num_blocks++;
614 set_visited(cur);
615 set_active(cur);
616
617 // recursive call for all successors
618 int i;
619 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
620 count_edges(cur->sux_at(i), cur);
621 }
622 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
623 count_edges(cur->exception_handler_at(i), cur);
624 }
625
626 clear_active(cur);
627
628 // Each loop has a unique number.
629 // When multiple loops are nested, assign_loop_depth assumes that the
630 // innermost loop has the lowest number. This is guaranteed by setting
631 // the loop number after the recursive calls for the successors above
632 // have returned.
633 if (cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
634 assert(cur->loop_index() == -1, "cannot set loop-index twice");
635 TRACE_LINEAR_SCAN(3, tty->print_cr("Block B%d is loop header of loop %d", cur->block_id(), _num_loops));
636
637 cur->set_loop_index(_num_loops);
638 _loop_headers.append(cur);
639 _num_loops++;
640 }
641
642 TRACE_LINEAR_SCAN(3, tty->print_cr("Finished count_edges for block B%d", cur->block_id()));
643 }
644
645
646 void ComputeLinearScanOrder::mark_loops() {
647 TRACE_LINEAR_SCAN(3, tty->print_cr("----- marking loops"));
648
649 _loop_map = BitMap2D(_num_loops, _max_block_id);
650
651 for (int i = _loop_end_blocks.length() - 1; i >= 0; i--) {
652 BlockBegin* loop_end = _loop_end_blocks.at(i);
653 BlockBegin* loop_start = loop_end->sux_at(0);
654 int loop_idx = loop_start->loop_index();
655
656 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));
657 assert(loop_end->is_set(BlockBegin::linear_scan_loop_end_flag), "loop end flag must be set");
658 assert(loop_end->number_of_sux() == 1, "incorrect number of successors");
659 assert(loop_start->is_set(BlockBegin::linear_scan_loop_header_flag), "loop header flag must be set");
660 assert(loop_idx >= 0 && loop_idx < _num_loops, "loop index not set");
661 assert(_work_list.is_empty(), "work list must be empty before processing");
662
663 // add the end-block of the loop to the working list
664 _work_list.push(loop_end);
665 set_block_in_loop(loop_idx, loop_end);
666 do {
667 BlockBegin* cur = _work_list.pop();
668
669 TRACE_LINEAR_SCAN(3, tty->print_cr(" processing B%d", cur->block_id()));
670 assert(is_block_in_loop(loop_idx, cur), "bit in loop map must be set when block is in work list");
671
672 // recursive processing of all predecessors ends when start block of loop is reached
673 if (cur != loop_start && !cur->is_set(BlockBegin::osr_entry_flag)) {
674 for (int j = cur->number_of_preds() - 1; j >= 0; j--) {
675 BlockBegin* pred = cur->pred_at(j);
676
677 if (!is_block_in_loop(loop_idx, pred) /*&& !pred->is_set(BlockBeginosr_entry_flag)*/) {
678 // this predecessor has not been processed yet, so add it to work list
679 TRACE_LINEAR_SCAN(3, tty->print_cr(" pushing B%d", pred->block_id()));
680 _work_list.push(pred);
681 set_block_in_loop(loop_idx, pred);
682 }
683 }
684 }
685 } while (!_work_list.is_empty());
686 }
687 }
688
689
690 // check for non-natural loops (loops where the loop header does not dominate
691 // all other loop blocks = loops with multiple entries).
692 // such loops are ignored
693 void ComputeLinearScanOrder::clear_non_natural_loops(BlockBegin* start_block) {
694 for (int i = _num_loops - 1; i >= 0; i--) {
695 if (is_block_in_loop(i, start_block)) {
696 // loop i contains the entry block of the method
697 // -> this is not a natural loop, so ignore it
698 TRACE_LINEAR_SCAN(2, tty->print_cr("Loop %d is non-natural, so it is ignored", i));
699
700 BlockBegin *loop_header = _loop_headers.at(i);
701 assert(loop_header->is_set(BlockBegin::linear_scan_loop_header_flag), "Must be loop header");
702
703 for (int j = 0; j < loop_header->number_of_preds(); j++) {
704 BlockBegin *pred = loop_header->pred_at(j);
705 pred->clear(BlockBegin::linear_scan_loop_end_flag);
706 }
707
708 loop_header->clear(BlockBegin::linear_scan_loop_header_flag);
709
710 for (int block_id = _max_block_id - 1; block_id >= 0; block_id--) {
711 clear_block_in_loop(i, block_id);
712 }
713 _iterative_dominators = true;
714 }
715 }
716 }
717
718 void ComputeLinearScanOrder::assign_loop_depth(BlockBegin* start_block) {
719 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing loop-depth and weight"));
720 init_visited();
721
722 assert(_work_list.is_empty(), "work list must be empty before processing");
723 _work_list.append(start_block);
724
725 do {
726 BlockBegin* cur = _work_list.pop();
727
728 if (!is_visited(cur)) {
729 set_visited(cur);
730 TRACE_LINEAR_SCAN(4, tty->print_cr("Computing loop depth for block B%d", cur->block_id()));
731
732 // compute loop-depth and loop-index for the block
733 assert(cur->loop_depth() == 0, "cannot set loop-depth twice");
734 int i;
735 int loop_depth = 0;
736 int min_loop_idx = -1;
737 for (i = _num_loops - 1; i >= 0; i--) {
738 if (is_block_in_loop(i, cur)) {
739 loop_depth++;
740 min_loop_idx = i;
741 }
742 }
743 cur->set_loop_depth(loop_depth);
744 cur->set_loop_index(min_loop_idx);
745
746 // append all unvisited successors to work list
747 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
748 _work_list.append(cur->sux_at(i));
749 }
750 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
751 _work_list.append(cur->exception_handler_at(i));
752 }
753 }
754 } while (!_work_list.is_empty());
755 }
756
757
758 BlockBegin* ComputeLinearScanOrder::common_dominator(BlockBegin* a, BlockBegin* b) {
759 assert(a != nullptr && b != nullptr, "must have input blocks");
760
761 _dominator_blocks.clear();
762 while (a != nullptr) {
763 _dominator_blocks.set_bit(a->block_id());
764 assert(a->dominator() != nullptr || a == _linear_scan_order->at(0), "dominator must be initialized");
765 a = a->dominator();
766 }
767 while (b != nullptr && !_dominator_blocks.at(b->block_id())) {
768 assert(b->dominator() != nullptr || b == _linear_scan_order->at(0), "dominator must be initialized");
769 b = b->dominator();
770 }
771
772 assert(b != nullptr, "could not find dominator");
773 return b;
774 }
775
776 void ComputeLinearScanOrder::compute_dominator(BlockBegin* cur, BlockBegin* parent) {
777 init_visited();
778 compute_dominator_impl(cur, parent);
779 }
780
781 void ComputeLinearScanOrder::compute_dominator_impl(BlockBegin* cur, BlockBegin* parent) {
782 // Mark as visited to avoid recursive calls with same parent
783 set_visited(cur);
784
785 if (cur->dominator() == nullptr) {
786 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: initializing dominator of B%d to B%d", cur->block_id(), parent->block_id()));
787 cur->set_dominator(parent);
788
789 } else if (!(cur->is_set(BlockBegin::linear_scan_loop_header_flag) && parent->is_set(BlockBegin::linear_scan_loop_end_flag))) {
790 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()));
791 // Does not hold for exception blocks
792 assert(cur->number_of_preds() > 1 || cur->is_set(BlockBegin::exception_entry_flag), "");
793 cur->set_dominator(common_dominator(cur->dominator(), parent));
794 }
795
796 // Additional edge to xhandler of all our successors
797 // range check elimination needs that the state at the end of a
798 // block be valid in every block it dominates so cur must dominate
799 // the exception handlers of its successors.
800 int num_cur_xhandler = cur->number_of_exception_handlers();
801 for (int j = 0; j < num_cur_xhandler; j++) {
802 BlockBegin* xhandler = cur->exception_handler_at(j);
803 if (!is_visited(xhandler)) {
804 compute_dominator_impl(xhandler, parent);
805 }
806 }
807 }
808
809
810 int ComputeLinearScanOrder::compute_weight(BlockBegin* cur) {
811 BlockBegin* single_sux = nullptr;
812 if (cur->number_of_sux() == 1) {
813 single_sux = cur->sux_at(0);
814 }
815
816 // limit loop-depth to 15 bit (only for security reason, it will never be so big)
817 int weight = (cur->loop_depth() & 0x7FFF) << 16;
818
819 // general macro for short definition of weight flags
820 // the first instance of INC_WEIGHT_IF has the highest priority
821 int cur_bit = 15;
822 #define INC_WEIGHT_IF(condition) if ((condition)) { weight |= (1 << cur_bit); } cur_bit--;
823
824 // this is necessary for the (very rare) case that two successive blocks have
825 // the same loop depth, but a different loop index (can happen for endless loops
826 // with exception handlers)
827 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_header_flag));
828
829 // loop end blocks (blocks that end with a backward branch) are added
830 // after all other blocks of the loop.
831 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_end_flag));
832
833 // critical edge split blocks are preferred because than they have a bigger
834 // proability to be completely empty
835 INC_WEIGHT_IF(cur->is_set(BlockBegin::critical_edge_split_flag));
836
837 // exceptions should not be thrown in normal control flow, so these blocks
838 // are added as late as possible
839 INC_WEIGHT_IF(cur->end()->as_Throw() == nullptr && (single_sux == nullptr || single_sux->end()->as_Throw() == nullptr));
840 INC_WEIGHT_IF(cur->end()->as_Return() == nullptr && (single_sux == nullptr || single_sux->end()->as_Return() == nullptr));
841
842 // exceptions handlers are added as late as possible
843 INC_WEIGHT_IF(!cur->is_set(BlockBegin::exception_entry_flag));
844
845 // guarantee that weight is > 0
846 weight |= 1;
847
848 #undef INC_WEIGHT_IF
849 assert(cur_bit >= 0, "too many flags");
850 assert(weight > 0, "weight cannot become negative");
851
852 return weight;
853 }
854
855 bool ComputeLinearScanOrder::ready_for_processing(BlockBegin* cur) {
856 // Discount the edge just traveled.
857 // When the number drops to zero, all forward branches were processed
858 if (dec_forward_branches(cur) != 0) {
859 return false;
860 }
861
862 assert(_linear_scan_order->find(cur) == -1, "block already processed (block can be ready only once)");
863 assert(_work_list.find(cur) == -1, "block already in work-list (block can be ready only once)");
864 return true;
865 }
866
867 void ComputeLinearScanOrder::sort_into_work_list(BlockBegin* cur) {
868 assert(_work_list.find(cur) == -1, "block already in work list");
869
870 int cur_weight = compute_weight(cur);
871
872 // the linear_scan_number is used to cache the weight of a block
873 cur->set_linear_scan_number(cur_weight);
874
875 #ifndef PRODUCT
876 if (StressLinearScan) {
877 _work_list.insert_before(0, cur);
878 return;
879 }
880 #endif
881
882 _work_list.append(nullptr); // provide space for new element
883
884 int insert_idx = _work_list.length() - 1;
885 while (insert_idx > 0 && _work_list.at(insert_idx - 1)->linear_scan_number() > cur_weight) {
886 _work_list.at_put(insert_idx, _work_list.at(insert_idx - 1));
887 insert_idx--;
888 }
889 _work_list.at_put(insert_idx, cur);
890
891 TRACE_LINEAR_SCAN(3, tty->print_cr("Sorted B%d into worklist. new worklist:", cur->block_id()));
892 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()));
893
894 #ifdef ASSERT
895 for (int i = 0; i < _work_list.length(); i++) {
896 assert(_work_list.at(i)->linear_scan_number() > 0, "weight not set");
897 assert(i == 0 || _work_list.at(i - 1)->linear_scan_number() <= _work_list.at(i)->linear_scan_number(), "incorrect order in worklist");
898 }
899 #endif
900 }
901
902 void ComputeLinearScanOrder::append_block(BlockBegin* cur) {
903 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()));
904 assert(_linear_scan_order->find(cur) == -1, "cannot add the same block twice");
905
906 // currently, the linear scan order and code emit order are equal.
907 // therefore the linear_scan_number and the weight of a block must also
908 // be equal.
909 cur->set_linear_scan_number(_linear_scan_order->length());
910 _linear_scan_order->append(cur);
911 }
912
913 void ComputeLinearScanOrder::compute_order(BlockBegin* start_block) {
914 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing final block order"));
915
916 // the start block is always the first block in the linear scan order
917 _linear_scan_order = new BlockList(_num_blocks);
918 append_block(start_block);
919
920 assert(start_block->end()->as_Base() != nullptr, "start block must end with Base-instruction");
921 BlockBegin* std_entry = ((Base*)start_block->end())->std_entry();
922 BlockBegin* osr_entry = ((Base*)start_block->end())->osr_entry();
923
924 BlockBegin* sux_of_osr_entry = nullptr;
925 if (osr_entry != nullptr) {
926 // special handling for osr entry:
927 // ignore the edge between the osr entry and its successor for processing
928 // the osr entry block is added manually below
929 assert(osr_entry->number_of_sux() == 1, "osr entry must have exactly one successor");
930 assert(osr_entry->sux_at(0)->number_of_preds() >= 2, "successor of osr entry must have two predecessors (otherwise it is not present in normal control flow");
931
932 sux_of_osr_entry = osr_entry->sux_at(0);
933 dec_forward_branches(sux_of_osr_entry);
934
935 compute_dominator(osr_entry, start_block);
936 _iterative_dominators = true;
937 }
938 compute_dominator(std_entry, start_block);
939
940 // start processing with standard entry block
941 assert(_work_list.is_empty(), "list must be empty before processing");
942
943 if (ready_for_processing(std_entry)) {
944 sort_into_work_list(std_entry);
945 } else {
946 assert(false, "the std_entry must be ready for processing (otherwise, the method has no start block)");
947 }
948
949 do {
950 BlockBegin* cur = _work_list.pop();
951
952 if (cur == sux_of_osr_entry) {
953 // the osr entry block is ignored in normal processing, it is never added to the
954 // work list. Instead, it is added as late as possible manually here.
955 append_block(osr_entry);
956 compute_dominator(cur, osr_entry);
957 }
958 append_block(cur);
959
960 int i;
961 int num_sux = cur->number_of_sux();
962 // changed loop order to get "intuitive" order of if- and else-blocks
963 for (i = 0; i < num_sux; i++) {
964 BlockBegin* sux = cur->sux_at(i);
965 compute_dominator(sux, cur);
966 if (ready_for_processing(sux)) {
967 sort_into_work_list(sux);
968 }
969 }
970 num_sux = cur->number_of_exception_handlers();
971 for (i = 0; i < num_sux; i++) {
972 BlockBegin* sux = cur->exception_handler_at(i);
973 if (ready_for_processing(sux)) {
974 sort_into_work_list(sux);
975 }
976 }
977 } while (_work_list.length() > 0);
978 }
979
980
981 bool ComputeLinearScanOrder::compute_dominators_iter() {
982 bool changed = false;
983 int num_blocks = _linear_scan_order->length();
984
985 assert(_linear_scan_order->at(0)->dominator() == nullptr, "must not have dominator");
986 assert(_linear_scan_order->at(0)->number_of_preds() == 0, "must not have predecessors");
987 for (int i = 1; i < num_blocks; i++) {
988 BlockBegin* block = _linear_scan_order->at(i);
989
990 BlockBegin* dominator = block->pred_at(0);
991 int num_preds = block->number_of_preds();
992
993 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: Processing B%d", block->block_id()));
994
995 for (int j = 0; j < num_preds; j++) {
996
997 BlockBegin *pred = block->pred_at(j);
998 TRACE_LINEAR_SCAN(4, tty->print_cr(" DOM: Subrocessing B%d", pred->block_id()));
999
1000 if (block->is_set(BlockBegin::exception_entry_flag)) {
1001 dominator = common_dominator(dominator, pred);
1002 int num_pred_preds = pred->number_of_preds();
1003 for (int k = 0; k < num_pred_preds; k++) {
1004 dominator = common_dominator(dominator, pred->pred_at(k));
1005 }
1006 } else {
1007 dominator = common_dominator(dominator, pred);
1008 }
1009 }
1010
1011 if (dominator != block->dominator()) {
1012 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()));
1013
1014 block->set_dominator(dominator);
1015 changed = true;
1016 }
1017 }
1018 return changed;
1019 }
1020
1021 void ComputeLinearScanOrder::compute_dominators() {
1022 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing dominators (iterative computation reqired: %d)", _iterative_dominators));
1023
1024 // iterative computation of dominators is only required for methods with non-natural loops
1025 // and OSR-methods. For all other methods, the dominators computed when generating the
1026 // linear scan block order are correct.
1027 if (_iterative_dominators) {
1028 do {
1029 TRACE_LINEAR_SCAN(1, tty->print_cr("DOM: next iteration of fix-point calculation"));
1030 } while (compute_dominators_iter());
1031 }
1032
1033 // check that dominators are correct
1034 assert(!compute_dominators_iter(), "fix point not reached");
1035
1036 // Add Blocks to dominates-Array
1037 int num_blocks = _linear_scan_order->length();
1038 for (int i = 0; i < num_blocks; i++) {
1039 BlockBegin* block = _linear_scan_order->at(i);
1040
1041 BlockBegin *dom = block->dominator();
1042 if (dom) {
1043 assert(dom->dominator_depth() != -1, "Dominator must have been visited before");
1044 dom->dominates()->append(block);
1045 block->set_dominator_depth(dom->dominator_depth() + 1);
1046 } else {
1047 block->set_dominator_depth(0);
1048 }
1049 }
1050 }
1051
1052
1053 #ifdef ASSERT
1054 void ComputeLinearScanOrder::print_blocks() {
1055 if (TraceLinearScanLevel >= 2) {
1056 tty->print_cr("----- loop information:");
1057 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1058 BlockBegin* cur = _linear_scan_order->at(block_idx);
1059
1060 tty->print("%4d: B%2d: ", cur->linear_scan_number(), cur->block_id());
1061 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1062 tty->print ("%d ", is_block_in_loop(loop_idx, cur));
1063 }
1064 tty->print_cr(" -> loop_index: %2d, loop_depth: %2d", cur->loop_index(), cur->loop_depth());
1065 }
1066 }
1067
1068 if (TraceLinearScanLevel >= 1) {
1069 tty->print_cr("----- linear-scan block order:");
1070 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1071 BlockBegin* cur = _linear_scan_order->at(block_idx);
1072 tty->print("%4d: B%2d loop: %2d depth: %2d", cur->linear_scan_number(), cur->block_id(), cur->loop_index(), cur->loop_depth());
1073
1074 tty->print(cur->is_set(BlockBegin::exception_entry_flag) ? " ex" : " ");
1075 tty->print(cur->is_set(BlockBegin::critical_edge_split_flag) ? " ce" : " ");
1076 tty->print(cur->is_set(BlockBegin::linear_scan_loop_header_flag) ? " lh" : " ");
1077 tty->print(cur->is_set(BlockBegin::linear_scan_loop_end_flag) ? " le" : " ");
1078
1079 if (cur->dominator() != nullptr) {
1080 tty->print(" dom: B%d ", cur->dominator()->block_id());
1081 } else {
1082 tty->print(" dom: null ");
1083 }
1084
1085 if (cur->number_of_preds() > 0) {
1086 tty->print(" preds: ");
1087 for (int j = 0; j < cur->number_of_preds(); j++) {
1088 BlockBegin* pred = cur->pred_at(j);
1089 tty->print("B%d ", pred->block_id());
1090 }
1091 }
1092 if (cur->number_of_sux() > 0) {
1093 tty->print(" sux: ");
1094 for (int j = 0; j < cur->number_of_sux(); j++) {
1095 BlockBegin* sux = cur->sux_at(j);
1096 tty->print("B%d ", sux->block_id());
1097 }
1098 }
1099 if (cur->number_of_exception_handlers() > 0) {
1100 tty->print(" ex: ");
1101 for (int j = 0; j < cur->number_of_exception_handlers(); j++) {
1102 BlockBegin* ex = cur->exception_handler_at(j);
1103 tty->print("B%d ", ex->block_id());
1104 }
1105 }
1106 tty->cr();
1107 }
1108 }
1109 }
1110
1111 void ComputeLinearScanOrder::verify() {
1112 assert(_linear_scan_order->length() == _num_blocks, "wrong number of blocks in list");
1113
1114 if (StressLinearScan) {
1115 // blocks are scrambled when StressLinearScan is used
1116 return;
1117 }
1118
1119 // check that all successors of a block have a higher linear-scan-number
1120 // and that all predecessors of a block have a lower linear-scan-number
1121 // (only backward branches of loops are ignored)
1122 int i;
1123 for (i = 0; i < _linear_scan_order->length(); i++) {
1124 BlockBegin* cur = _linear_scan_order->at(i);
1125
1126 assert(cur->linear_scan_number() == i, "incorrect linear_scan_number");
1127 assert(cur->linear_scan_number() >= 0 && cur->linear_scan_number() == _linear_scan_order->find(cur), "incorrect linear_scan_number");
1128
1129 int j;
1130 for (j = cur->number_of_sux() - 1; j >= 0; j--) {
1131 BlockBegin* sux = cur->sux_at(j);
1132
1133 assert(sux->linear_scan_number() >= 0 && sux->linear_scan_number() == _linear_scan_order->find(sux), "incorrect linear_scan_number");
1134 if (!sux->is_set(BlockBegin::backward_branch_target_flag)) {
1135 assert(cur->linear_scan_number() < sux->linear_scan_number(), "invalid order");
1136 }
1137 if (cur->loop_depth() == sux->loop_depth()) {
1138 assert(cur->loop_index() == sux->loop_index() || sux->is_set(BlockBegin::linear_scan_loop_header_flag), "successive blocks with same loop depth must have same loop index");
1139 }
1140 }
1141
1142 for (j = cur->number_of_preds() - 1; j >= 0; j--) {
1143 BlockBegin* pred = cur->pred_at(j);
1144
1145 assert(pred->linear_scan_number() >= 0 && pred->linear_scan_number() == _linear_scan_order->find(pred), "incorrect linear_scan_number");
1146 if (!cur->is_set(BlockBegin::backward_branch_target_flag)) {
1147 assert(cur->linear_scan_number() > pred->linear_scan_number(), "invalid order");
1148 }
1149 if (cur->loop_depth() == pred->loop_depth()) {
1150 assert(cur->loop_index() == pred->loop_index() || cur->is_set(BlockBegin::linear_scan_loop_header_flag), "successive blocks with same loop depth must have same loop index");
1151 }
1152
1153 assert(cur->dominator()->linear_scan_number() <= cur->pred_at(j)->linear_scan_number(), "dominator must be before predecessors");
1154 }
1155
1156 // check dominator
1157 if (i == 0) {
1158 assert(cur->dominator() == nullptr, "first block has no dominator");
1159 } else {
1160 assert(cur->dominator() != nullptr, "all but first block must have dominator");
1161 }
1162 // Assertion does not hold for exception handlers
1163 assert(cur->number_of_preds() != 1 || cur->dominator() == cur->pred_at(0) || cur->is_set(BlockBegin::exception_entry_flag), "Single predecessor must also be dominator");
1164 }
1165
1166 // check that all loops are continuous
1167 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1168 int block_idx = 0;
1169 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "the first block must not be present in any loop");
1170
1171 // skip blocks before the loop
1172 while (block_idx < _num_blocks && !is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1173 block_idx++;
1174 }
1175 // skip blocks of loop
1176 while (block_idx < _num_blocks && is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1177 block_idx++;
1178 }
1179 // after the first non-loop block, there must not be another loop-block
1180 while (block_idx < _num_blocks) {
1181 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "loop not continuous in linear-scan order");
1182 block_idx++;
1183 }
1184 }
1185 }
1186 #endif // ASSERT
1187
1188
1189 void IR::compute_code() {
1190 assert(is_valid(), "IR must be valid");
1191
1192 ComputeLinearScanOrder compute_order(compilation(), start());
1193 _num_loops = compute_order.num_loops();
1194 _code = compute_order.linear_scan_order();
1195 }
1196
1197
1198 void IR::compute_use_counts() {
1199 // make sure all values coming out of this block get evaluated.
1200 int num_blocks = _code->length();
1201 for (int i = 0; i < num_blocks; i++) {
1202 _code->at(i)->end()->state()->pin_stack_for_linear_scan();
1203 }
1204
1205 // compute use counts
1206 UseCountComputer::compute(_code);
1207 }
1208
1209
1210 void IR::iterate_preorder(BlockClosure* closure) {
1211 assert(is_valid(), "IR must be valid");
1212 start()->iterate_preorder(closure);
1213 }
1214
1215
1216 void IR::iterate_postorder(BlockClosure* closure) {
1217 assert(is_valid(), "IR must be valid");
1218 start()->iterate_postorder(closure);
1219 }
1220
1221 void IR::iterate_linear_scan_order(BlockClosure* closure) {
1222 linear_scan_order()->iterate_forward(closure);
1223 }
1224
1225
1226 #ifndef PRODUCT
1227 class BlockPrinter: public BlockClosure {
1228 private:
1229 InstructionPrinter* _ip;
1230 bool _cfg_only;
1231 bool _live_only;
1232
1233 public:
1234 BlockPrinter(InstructionPrinter* ip, bool cfg_only, bool live_only = false) {
1235 _ip = ip;
1236 _cfg_only = cfg_only;
1237 _live_only = live_only;
1238 }
1239
1240 virtual void block_do(BlockBegin* block) {
1241 if (_cfg_only) {
1242 _ip->print_instr(block); tty->cr();
1243 } else {
1244 block->print_block(*_ip, _live_only);
1245 }
1246 }
1247 };
1248
1249
1250 void IR::print(BlockBegin* start, bool cfg_only, bool live_only) {
1251 ttyLocker ttyl;
1252 InstructionPrinter ip(!cfg_only);
1253 BlockPrinter bp(&ip, cfg_only, live_only);
1254 start->iterate_preorder(&bp);
1255 tty->cr();
1256 }
1257
1258 void IR::print(bool cfg_only, bool live_only) {
1259 if (is_valid()) {
1260 print(start(), cfg_only, live_only);
1261 } else {
1262 tty->print_cr("invalid IR");
1263 }
1264 }
1265 #endif // PRODUCT
1266
1267 #ifdef ASSERT
1268 class EndNotNullValidator : public BlockClosure {
1269 public:
1270 virtual void block_do(BlockBegin* block) {
1271 assert(block->end() != nullptr, "Expect block end to exist.");
1272 }
1273 };
1274
1275 class XentryFlagValidator : public BlockClosure {
1276 public:
1277 virtual void block_do(BlockBegin* block) {
1278 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1279 assert(!block->end()->sux_at(i)->is_set(BlockBegin::exception_entry_flag), "must not be xhandler");
1280 }
1281 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1282 assert(block->exception_handler_at(i)->is_set(BlockBegin::exception_entry_flag), "must be xhandler");
1283 }
1284 }
1285 };
1286
1287 typedef GrowableArray<BlockList*> BlockListList;
1288
1289 // Validation goals:
1290 // - code() length == blocks length
1291 // - code() contents == blocks content
1292 // - Each block's computed predecessors match sux lists (length)
1293 // - Each block's computed predecessors match sux lists (set content)
1294 class PredecessorAndCodeValidator : public BlockClosure {
1295 private:
1296 BlockListList* _predecessors; // Each index i will hold predecessors of block with id i
1297 BlockList* _blocks;
1298
1299 static int cmp(BlockBegin** a, BlockBegin** b) {
1300 return (*a)->block_id() - (*b)->block_id();
1301 }
1302
1303 public:
1304 PredecessorAndCodeValidator(IR* hir) {
1305 ResourceMark rm;
1306 _predecessors = new BlockListList(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), nullptr);
1307 _blocks = new BlockList(BlockBegin::number_of_blocks());
1308
1309 hir->start()->iterate_preorder(this);
1310 if (hir->code() != nullptr) {
1311 assert(hir->code()->length() == _blocks->length(), "must match");
1312 for (int i = 0; i < _blocks->length(); i++) {
1313 assert(hir->code()->contains(_blocks->at(i)), "should be in both lists");
1314 }
1315 }
1316
1317 for (int i = 0; i < _blocks->length(); i++) {
1318 BlockBegin* block = _blocks->at(i);
1319 verify_block_preds_against_collected_preds(block);
1320 }
1321 }
1322
1323 virtual void block_do(BlockBegin* block) {
1324 _blocks->append(block);
1325 collect_predecessors(block);
1326 }
1327
1328 private:
1329 void collect_predecessors(BlockBegin* block) {
1330 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1331 collect_predecessor(block, block->end()->sux_at(i));
1332 }
1333 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1334 collect_predecessor(block, block->exception_handler_at(i));
1335 }
1336 }
1337
1338 void collect_predecessor(BlockBegin* const pred, const BlockBegin* sux) {
1339 BlockList* preds = _predecessors->at_grow(sux->block_id(), nullptr);
1340 if (preds == nullptr) {
1341 preds = new BlockList();
1342 _predecessors->at_put(sux->block_id(), preds);
1343 }
1344 preds->append(pred);
1345 }
1346
1347 void verify_block_preds_against_collected_preds(const BlockBegin* block) const {
1348 BlockList* preds = _predecessors->at(block->block_id());
1349 if (preds == nullptr) {
1350 assert(block->number_of_preds() == 0, "should be the same");
1351 return;
1352 }
1353 assert(preds->length() == block->number_of_preds(), "should be the same");
1354
1355 // clone the pred list so we can mutate it
1356 BlockList* pred_copy = new BlockList();
1357 for (int j = 0; j < block->number_of_preds(); j++) {
1358 pred_copy->append(block->pred_at(j));
1359 }
1360 // sort them in the same order
1361 preds->sort(cmp);
1362 pred_copy->sort(cmp);
1363 for (int j = 0; j < block->number_of_preds(); j++) {
1364 assert(preds->at(j) == pred_copy->at(j), "must match");
1365 }
1366 }
1367 };
1368
1369 class VerifyBlockBeginField : public BlockClosure {
1370 public:
1371 virtual void block_do(BlockBegin* block) {
1372 for (Instruction* cur = block; cur != nullptr; cur = cur->next()) {
1373 assert(cur->block() == block, "Block begin is not correct");
1374 }
1375 }
1376 };
1377
1378 class ValidateEdgeMutuality : public BlockClosure {
1379 public:
1380 virtual void block_do(BlockBegin* block) {
1381 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1382 assert(block->end()->sux_at(i)->is_predecessor(block), "Block's successor should have it as predecessor");
1383 }
1384
1385 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1386 assert(block->exception_handler_at(i)->is_predecessor(block), "Block's exception handler should have it as predecessor");
1387 }
1388
1389 for (int i = 0; i < block->number_of_preds(); i++) {
1390 assert(block->pred_at(i) != nullptr, "Predecessor must exist");
1391 assert(block->pred_at(i)->end() != nullptr, "Predecessor end must exist");
1392 bool is_sux = block->pred_at(i)->end()->is_sux(block);
1393 bool is_xhandler = block->pred_at(i)->is_exception_handler(block);
1394 assert(is_sux || is_xhandler, "Block's predecessor should have it as successor or xhandler");
1395 }
1396 }
1397 };
1398
1399 void IR::expand_with_neighborhood(BlockList& blocks) {
1400 int original_size = blocks.length();
1401 for (int h = 0; h < original_size; h++) {
1402 BlockBegin* block = blocks.at(h);
1403
1404 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1405 if (!blocks.contains(block->end()->sux_at(i))) {
1406 blocks.append(block->end()->sux_at(i));
1407 }
1408 }
1409
1410 for (int i = 0; i < block->number_of_preds(); i++) {
1411 if (!blocks.contains(block->pred_at(i))) {
1412 blocks.append(block->pred_at(i));
1413 }
1414 }
1415
1416 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1417 if (!blocks.contains(block->exception_handler_at(i))) {
1418 blocks.append(block->exception_handler_at(i));
1419 }
1420 }
1421 }
1422 }
1423
1424 void IR::verify_local(BlockList& blocks) {
1425 EndNotNullValidator ennv;
1426 blocks.iterate_forward(&ennv);
1427
1428 ValidateEdgeMutuality vem;
1429 blocks.iterate_forward(&vem);
1430
1431 VerifyBlockBeginField verifier;
1432 blocks.iterate_forward(&verifier);
1433 }
1434
1435 void IR::verify() {
1436 XentryFlagValidator xe;
1437 iterate_postorder(&xe);
1438
1439 PredecessorAndCodeValidator pv(this);
1440
1441 EndNotNullValidator ennv;
1442 iterate_postorder(&ennv);
1443
1444 ValidateEdgeMutuality vem;
1445 iterate_postorder(&vem);
1446
1447 VerifyBlockBeginField verifier;
1448 iterate_postorder(&verifier);
1449 }
1450 #endif // ASSERT
1451
1452 void SubstitutionResolver::visit(Value* v) {
1453 Value v0 = *v;
1454 if (v0) {
1455 Value vs = v0->subst();
1456 if (vs != v0) {
1457 *v = v0->subst();
1458 }
1459 }
1460 }
1461
1462 #ifdef ASSERT
1463 class SubstitutionChecker: public ValueVisitor {
1464 void visit(Value* v) {
1465 Value v0 = *v;
1466 if (v0) {
1467 Value vs = v0->subst();
1468 assert(vs == v0, "missed substitution");
1469 }
1470 }
1471 };
1472 #endif
1473
1474
1475 void SubstitutionResolver::block_do(BlockBegin* block) {
1476 Instruction* last = nullptr;
1477 for (Instruction* n = block; n != nullptr;) {
1478 n->values_do(this);
1479 // need to remove this instruction from the instruction stream
1480 if (n->subst() != n) {
1481 guarantee(last != nullptr, "must have last");
1482 last->set_next(n->next());
1483 } else {
1484 last = n;
1485 }
1486 n = last->next();
1487 }
1488
1489 #ifdef ASSERT
1490 SubstitutionChecker check_substitute;
1491 if (block->state()) block->state()->values_do(&check_substitute);
1492 block->block_values_do(&check_substitute);
1493 if (block->end() && block->end()->state()) block->end()->state()->values_do(&check_substitute);
1494 #endif
1495 }