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 _wrote_stable = false;
150 _start = nullptr;
151
152 if (osr_bci != -1) {
153 // selective creation of phi functions is not possibel in osr-methods
154 _requires_phi_function.set_range(0, method->max_locals());
155 }
156
157 assert(method->holder()->is_loaded() , "method holder must be loaded");
158
159 // build graph if monitor pairing is ok
160 if (create_graph && monitor_pairing_ok()) _start = build_graph(compilation, osr_bci);
161 }
162
163
164 int IRScope::max_stack() const {
165 int my_max = method()->max_stack();
166 int callee_max = 0;
167 for (int i = 0; i < number_of_callees(); i++) {
168 callee_max = MAX2(callee_max, callee_no(i)->max_stack());
169 }
170 return my_max + callee_max;
171 }
172
173
174 bool IRScopeDebugInfo::should_reexecute() {
175 if (_should_reexecute) {
176 return true;
177 }
178 ciMethod* cur_method = scope()->method();
179 int cur_bci = bci();
180 if (cur_method != nullptr && cur_bci != SynchronizationEntryBCI) {
181 Bytecodes::Code code = cur_method->java_code_at_bci(cur_bci);
182 return Interpreter::bytecode_should_reexecute(code);
183 } else
184 return false;
185 }
186
187 // Implementation of CodeEmitInfo
188
189 // Stack must be NON-null
190 CodeEmitInfo::CodeEmitInfo(ValueStack* stack, XHandlers* exception_handlers, bool deoptimize_on_exception)
191 : _scope_debug_info(nullptr)
192 , _scope(stack->scope())
193 , _exception_handlers(exception_handlers)
194 , _oop_map(nullptr)
195 , _stack(stack)
196 , _is_method_handle_invoke(false)
197 , _deoptimize_on_exception(deoptimize_on_exception)
198 , _force_reexecute(false) {
199 assert(_stack != nullptr, "must be non null");
200 }
201
202
203 CodeEmitInfo::CodeEmitInfo(CodeEmitInfo* info, ValueStack* stack)
204 : _scope_debug_info(nullptr)
205 , _scope(info->_scope)
206 , _exception_handlers(nullptr)
207 , _oop_map(nullptr)
208 , _stack(stack == nullptr ? info->_stack : stack)
209 , _is_method_handle_invoke(info->_is_method_handle_invoke)
210 , _deoptimize_on_exception(info->_deoptimize_on_exception)
211 , _force_reexecute(info->_force_reexecute) {
212
213 // deep copy of exception handlers
214 if (info->_exception_handlers != nullptr) {
215 _exception_handlers = new XHandlers(info->_exception_handlers);
216 }
217 }
218
219
220 void CodeEmitInfo::record_debug_info(DebugInformationRecorder* recorder, int pc_offset, bool maybe_return_as_fields) {
221 // record the safepoint before recording the debug info for enclosing scopes
222 recorder->add_safepoint(pc_offset, _oop_map->deep_copy());
223 bool reexecute = _force_reexecute || _scope_debug_info->should_reexecute();
224 _scope_debug_info->record_debug_info(recorder, pc_offset, reexecute, _is_method_handle_invoke, maybe_return_as_fields);
225 recorder->end_safepoint(pc_offset);
226 }
227
228
229 void CodeEmitInfo::add_register_oop(LIR_Opr opr) {
230 assert(_oop_map != nullptr, "oop map must already exist");
231 assert(opr->is_single_cpu(), "should not call otherwise");
232
233 VMReg name = frame_map()->regname(opr);
234 _oop_map->set_oop(name);
235 }
236
237 // Mirror the stack size calculation in the deopt code
238 // How much stack space would we need at this point in the program in
239 // case of deoptimization?
240 int CodeEmitInfo::interpreter_frame_size() const {
241 ValueStack* state = _stack;
242 int size = 0;
243 int callee_parameters = 0;
244 int callee_locals = 0;
245 int extra_args = state->scope()->method()->max_stack() - state->stack_size();
246
247 while (state != nullptr) {
248 int locks = state->locks_size();
249 int temps = state->stack_size();
250 bool is_top_frame = (state == _stack);
251 ciMethod* method = state->scope()->method();
252
253 int frame_size = BytesPerWord * Interpreter::size_activation(method->max_stack(),
254 temps + callee_parameters,
255 extra_args,
256 locks,
257 callee_parameters,
258 callee_locals,
259 is_top_frame);
260 size += frame_size;
261
262 callee_parameters = method->size_of_parameters();
263 callee_locals = method->max_locals();
264 extra_args = 0;
265 state = state->caller_state();
266 }
267 return size + Deoptimization::last_frame_adjust(0, callee_locals) * BytesPerWord;
268 }
269
270 // Implementation of IR
271
272 IR::IR(Compilation* compilation, ciMethod* method, int osr_bci) :
273 _num_loops(0) {
274 // setup IR fields
275 _compilation = compilation;
276 _top_scope = new IRScope(compilation, nullptr, -1, method, osr_bci, true);
277 _code = nullptr;
278 }
279
280
281 void IR::optimize_blocks() {
282 Optimizer opt(this);
283 if (!compilation()->profile_branches()) {
284 if (DoCEE) {
285 opt.eliminate_conditional_expressions();
286 #ifndef PRODUCT
287 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after CEE"); print(true); }
288 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after CEE"); print(false); }
289 #endif
290 }
291 if (EliminateBlocks) {
292 opt.eliminate_blocks();
293 #ifndef PRODUCT
294 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after block elimination"); print(true); }
295 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after block elimination"); print(false); }
296 #endif
297 }
298 }
299 }
300
301 void IR::eliminate_null_checks() {
302 Optimizer opt(this);
303 if (EliminateNullChecks) {
304 opt.eliminate_null_checks();
305 #ifndef PRODUCT
306 if (PrintCFG || PrintCFG1) { tty->print_cr("CFG after null check elimination"); print(true); }
307 if (PrintIR || PrintIR1 ) { tty->print_cr("IR after null check elimination"); print(false); }
308 #endif
309 }
310 }
311
312 // The functionality of this class is to insert a new block between
313 // the 'from' and 'to' block of a critical edge.
314 // It first collects the block pairs, and then processes them.
315 //
316 // Some instructions may introduce more than one edge between two blocks.
317 // By checking if the current 'to' block sets critical_edge_split_flag
318 // (all new blocks set this flag) we can avoid repeated processing.
319 // This is why BlockPair contains the index rather than the original 'to' block.
320 class CriticalEdgeFinder: public BlockClosure {
321 BlockPairList blocks;
322
323 public:
324 CriticalEdgeFinder(IR* ir) {
325 ir->iterate_preorder(this);
326 }
327
328 void block_do(BlockBegin* bb) {
329 BlockEnd* be = bb->end();
330 int nos = be->number_of_sux();
331 if (nos >= 2) {
332 for (int i = 0; i < nos; i++) {
333 BlockBegin* sux = be->sux_at(i);
334 if (sux->number_of_preds() >= 2) {
335 blocks.append(new BlockPair(bb, i));
336 }
337 }
338 }
339 }
340
341 void split_edges() {
342 for (int i = 0; i < blocks.length(); i++) {
343 BlockPair* pair = blocks.at(i);
344 BlockBegin* from = pair->from();
345 int index = pair->index();
346 BlockBegin* to = from->end()->sux_at(index);
347 if (to->is_set(BlockBegin::critical_edge_split_flag)) {
348 // inserted
349 continue;
350 }
351 BlockBegin* split = from->insert_block_between(to);
352 #ifndef PRODUCT
353 if ((PrintIR || PrintIR1) && Verbose) {
354 tty->print_cr("Split critical edge B%d -> B%d (new block B%d)",
355 from->block_id(), to->block_id(), split->block_id());
356 }
357 #endif
358 }
359 }
360 };
361
362 void IR::split_critical_edges() {
363 CriticalEdgeFinder cef(this);
364 cef.split_edges();
365 }
366
367
368 class UseCountComputer: public ValueVisitor, BlockClosure {
369 private:
370 void visit(Value* n) {
371 // Local instructions and Phis for expression stack values at the
372 // start of basic blocks are not added to the instruction list
373 if (!(*n)->is_linked() && (*n)->can_be_linked()) {
374 assert(false, "a node was not appended to the graph");
375 Compilation::current()->bailout("a node was not appended to the graph");
376 }
377 // use n's input if not visited before
378 if (!(*n)->is_pinned() && !(*n)->has_uses()) {
379 // note: a) if the instruction is pinned, it will be handled by compute_use_count
380 // b) if the instruction has uses, it was touched before
381 // => in both cases we don't need to update n's values
382 uses_do(n);
383 }
384 // use n
385 (*n)->_use_count++;
386 }
387
388 Values* worklist;
389 int depth;
390 enum {
391 max_recurse_depth = 20
392 };
393
394 void uses_do(Value* n) {
395 depth++;
396 if (depth > max_recurse_depth) {
397 // don't allow the traversal to recurse too deeply
398 worklist->push(*n);
399 } else {
400 (*n)->input_values_do(this);
401 // special handling for some instructions
402 if ((*n)->as_BlockEnd() != nullptr) {
403 // note on BlockEnd:
404 // must 'use' the stack only if the method doesn't
405 // terminate, however, in those cases stack is empty
406 (*n)->state_values_do(this);
407 }
408 }
409 depth--;
410 }
411
412 void block_do(BlockBegin* b) {
413 depth = 0;
414 // process all pinned nodes as the roots of expression trees
415 for (Instruction* n = b; n != nullptr; n = n->next()) {
416 if (n->is_pinned()) uses_do(&n);
417 }
418 assert(depth == 0, "should have counted back down");
419
420 // now process any unpinned nodes which recursed too deeply
421 while (worklist->length() > 0) {
422 Value t = worklist->pop();
423 if (!t->is_pinned()) {
424 // compute the use count
425 uses_do(&t);
426
427 // pin the instruction so that LIRGenerator doesn't recurse
428 // too deeply during it's evaluation.
429 t->pin();
430 }
431 }
432 assert(depth == 0, "should have counted back down");
433 }
434
435 UseCountComputer() {
436 worklist = new Values();
437 depth = 0;
438 }
439
440 public:
441 static void compute(BlockList* blocks) {
442 UseCountComputer ucc;
443 blocks->iterate_backward(&ucc);
444 }
445 };
446
447
448 // helper macro for short definition of trace-output inside code
449 #ifdef ASSERT
450 #define TRACE_LINEAR_SCAN(level, code) \
451 if (TraceLinearScanLevel >= level) { \
452 code; \
453 }
454 #else
455 #define TRACE_LINEAR_SCAN(level, code)
456 #endif
457
458 class ComputeLinearScanOrder : public StackObj {
459 private:
460 int _max_block_id; // the highest block_id of a block
461 int _num_blocks; // total number of blocks (smaller than _max_block_id)
462 int _num_loops; // total number of loops
463 bool _iterative_dominators;// method requires iterative computation of dominatiors
464
465 BlockList* _linear_scan_order; // the resulting list of blocks in correct order
466
467 ResourceBitMap _visited_blocks; // used for recursive processing of blocks
468 ResourceBitMap _active_blocks; // used for recursive processing of blocks
469 ResourceBitMap _dominator_blocks; // temporary BitMap used for computation of dominator
470 intArray _forward_branches; // number of incoming forward branches for each block
471 BlockList _loop_end_blocks; // list of all loop end blocks collected during count_edges
472 BitMap2D _loop_map; // two-dimensional bit set: a bit is set if a block is contained in a loop
473 BlockList _work_list; // temporary list (used in mark_loops and compute_order)
474 BlockList _loop_headers;
475
476 Compilation* _compilation;
477
478 // accessors for _visited_blocks and _active_blocks
479 void init_visited() { _active_blocks.clear(); _visited_blocks.clear(); }
480 bool is_visited(BlockBegin* b) const { return _visited_blocks.at(b->block_id()); }
481 bool is_active(BlockBegin* b) const { return _active_blocks.at(b->block_id()); }
482 void set_visited(BlockBegin* b) { assert(!is_visited(b), "already set"); _visited_blocks.set_bit(b->block_id()); }
483 void set_active(BlockBegin* b) { assert(!is_active(b), "already set"); _active_blocks.set_bit(b->block_id()); }
484 void clear_active(BlockBegin* b) { assert(is_active(b), "not already"); _active_blocks.clear_bit(b->block_id()); }
485
486 // accessors for _forward_branches
487 void inc_forward_branches(BlockBegin* b) { _forward_branches.at_put(b->block_id(), _forward_branches.at(b->block_id()) + 1); }
488 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()); }
489
490 // accessors for _loop_map
491 bool is_block_in_loop (int loop_idx, BlockBegin* b) const { return _loop_map.at(loop_idx, b->block_id()); }
492 void set_block_in_loop (int loop_idx, BlockBegin* b) { _loop_map.set_bit(loop_idx, b->block_id()); }
493 void clear_block_in_loop(int loop_idx, int block_id) { _loop_map.clear_bit(loop_idx, block_id); }
494
495 // count edges between blocks
496 void count_edges(BlockBegin* cur, BlockBegin* parent);
497
498 // loop detection
499 void mark_loops();
500 void clear_non_natural_loops(BlockBegin* start_block);
501 void assign_loop_depth(BlockBegin* start_block);
502
503 // computation of final block order
504 BlockBegin* common_dominator(BlockBegin* a, BlockBegin* b);
505 void compute_dominator(BlockBegin* cur, BlockBegin* parent);
506 void compute_dominator_impl(BlockBegin* cur, BlockBegin* parent);
507 int compute_weight(BlockBegin* cur);
508 bool ready_for_processing(BlockBegin* cur);
509 void sort_into_work_list(BlockBegin* b);
510 void append_block(BlockBegin* cur);
511 void compute_order(BlockBegin* start_block);
512
513 // fixup of dominators for non-natural loops
514 bool compute_dominators_iter();
515 void compute_dominators();
516
517 // debug functions
518 DEBUG_ONLY(void print_blocks();)
519 DEBUG_ONLY(void verify();)
520
521 Compilation* compilation() const { return _compilation; }
522 public:
523 ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block);
524
525 // accessors for final result
526 BlockList* linear_scan_order() const { return _linear_scan_order; }
527 int num_loops() const { return _num_loops; }
528 };
529
530
531 ComputeLinearScanOrder::ComputeLinearScanOrder(Compilation* c, BlockBegin* start_block) :
532 _max_block_id(BlockBegin::number_of_blocks()),
533 _num_blocks(0),
534 _num_loops(0),
535 _iterative_dominators(false),
536 _linear_scan_order(nullptr), // initialized later with correct size
537 _visited_blocks(_max_block_id),
538 _active_blocks(_max_block_id),
539 _dominator_blocks(_max_block_id),
540 _forward_branches(_max_block_id, _max_block_id, 0),
541 _loop_end_blocks(8),
542 _loop_map(0), // initialized later with correct size
543 _work_list(8),
544 _compilation(c)
545 {
546 TRACE_LINEAR_SCAN(2, tty->print_cr("***** computing linear-scan block order"));
547
548 count_edges(start_block, nullptr);
549
550 if (compilation()->is_profiling()) {
551 ciMethod *method = compilation()->method();
552 if (!method->is_accessor()) {
553 ciMethodData* md = method->method_data_or_null();
554 assert(md != nullptr, "Sanity");
555 md->set_compilation_stats(_num_loops, _num_blocks);
556 }
557 }
558
559 if (_num_loops > 0) {
560 mark_loops();
561 clear_non_natural_loops(start_block);
562 assign_loop_depth(start_block);
563 }
564
565 compute_order(start_block);
566 compute_dominators();
567
568 DEBUG_ONLY(print_blocks());
569 DEBUG_ONLY(verify());
570 }
571
572
573 // Traverse the CFG:
574 // * count total number of blocks
575 // * count all incoming edges and backward incoming edges
576 // * number loop header blocks
577 // * create a list with all loop end blocks
578 void ComputeLinearScanOrder::count_edges(BlockBegin* cur, BlockBegin* parent) {
579 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));
580 assert(cur->dominator() == nullptr, "dominator already initialized");
581
582 if (is_active(cur)) {
583 TRACE_LINEAR_SCAN(3, tty->print_cr("backward branch"));
584 assert(is_visited(cur), "block must be visisted when block is active");
585 assert(parent != nullptr, "must have parent");
586
587 cur->set(BlockBegin::backward_branch_target_flag);
588
589 // When a loop header is also the start of an exception handler, then the backward branch is
590 // an exception edge. Because such edges are usually critical edges which cannot be split, the
591 // loop must be excluded here from processing.
592 if (cur->is_set(BlockBegin::exception_entry_flag)) {
593 // Make sure that dominators are correct in this weird situation
594 _iterative_dominators = true;
595 return;
596 }
597
598 cur->set(BlockBegin::linear_scan_loop_header_flag);
599 parent->set(BlockBegin::linear_scan_loop_end_flag);
600
601 assert(parent->number_of_sux() == 1 && parent->sux_at(0) == cur,
602 "loop end blocks must have one successor (critical edges are split)");
603
604 _loop_end_blocks.append(parent);
605 return;
606 }
607
608 // increment number of incoming forward branches
609 inc_forward_branches(cur);
610
611 if (is_visited(cur)) {
612 TRACE_LINEAR_SCAN(3, tty->print_cr("block already visited"));
613 return;
614 }
615
616 _num_blocks++;
617 set_visited(cur);
618 set_active(cur);
619
620 // recursive call for all successors
621 int i;
622 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
623 count_edges(cur->sux_at(i), cur);
624 }
625 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
626 count_edges(cur->exception_handler_at(i), cur);
627 }
628
629 clear_active(cur);
630
631 // Each loop has a unique number.
632 // When multiple loops are nested, assign_loop_depth assumes that the
633 // innermost loop has the lowest number. This is guaranteed by setting
634 // the loop number after the recursive calls for the successors above
635 // have returned.
636 if (cur->is_set(BlockBegin::linear_scan_loop_header_flag)) {
637 assert(cur->loop_index() == -1, "cannot set loop-index twice");
638 TRACE_LINEAR_SCAN(3, tty->print_cr("Block B%d is loop header of loop %d", cur->block_id(), _num_loops));
639
640 cur->set_loop_index(_num_loops);
641 _loop_headers.append(cur);
642 _num_loops++;
643 }
644
645 TRACE_LINEAR_SCAN(3, tty->print_cr("Finished count_edges for block B%d", cur->block_id()));
646 }
647
648
649 void ComputeLinearScanOrder::mark_loops() {
650 TRACE_LINEAR_SCAN(3, tty->print_cr("----- marking loops"));
651
652 _loop_map = BitMap2D(_num_loops, _max_block_id);
653
654 for (int i = _loop_end_blocks.length() - 1; i >= 0; i--) {
655 BlockBegin* loop_end = _loop_end_blocks.at(i);
656 BlockBegin* loop_start = loop_end->sux_at(0);
657 int loop_idx = loop_start->loop_index();
658
659 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));
660 assert(loop_end->is_set(BlockBegin::linear_scan_loop_end_flag), "loop end flag must be set");
661 assert(loop_end->number_of_sux() == 1, "incorrect number of successors");
662 assert(loop_start->is_set(BlockBegin::linear_scan_loop_header_flag), "loop header flag must be set");
663 assert(loop_idx >= 0 && loop_idx < _num_loops, "loop index not set");
664 assert(_work_list.is_empty(), "work list must be empty before processing");
665
666 // add the end-block of the loop to the working list
667 _work_list.push(loop_end);
668 set_block_in_loop(loop_idx, loop_end);
669 do {
670 BlockBegin* cur = _work_list.pop();
671
672 TRACE_LINEAR_SCAN(3, tty->print_cr(" processing B%d", cur->block_id()));
673 assert(is_block_in_loop(loop_idx, cur), "bit in loop map must be set when block is in work list");
674
675 // recursive processing of all predecessors ends when start block of loop is reached
676 if (cur != loop_start && !cur->is_set(BlockBegin::osr_entry_flag)) {
677 for (int j = cur->number_of_preds() - 1; j >= 0; j--) {
678 BlockBegin* pred = cur->pred_at(j);
679
680 if (!is_block_in_loop(loop_idx, pred) /*&& !pred->is_set(BlockBeginosr_entry_flag)*/) {
681 // this predecessor has not been processed yet, so add it to work list
682 TRACE_LINEAR_SCAN(3, tty->print_cr(" pushing B%d", pred->block_id()));
683 _work_list.push(pred);
684 set_block_in_loop(loop_idx, pred);
685 }
686 }
687 }
688 } while (!_work_list.is_empty());
689 }
690 }
691
692
693 // check for non-natural loops (loops where the loop header does not dominate
694 // all other loop blocks = loops with multiple entries).
695 // such loops are ignored
696 void ComputeLinearScanOrder::clear_non_natural_loops(BlockBegin* start_block) {
697 for (int i = _num_loops - 1; i >= 0; i--) {
698 if (is_block_in_loop(i, start_block)) {
699 // loop i contains the entry block of the method
700 // -> this is not a natural loop, so ignore it
701 TRACE_LINEAR_SCAN(2, tty->print_cr("Loop %d is non-natural, so it is ignored", i));
702
703 BlockBegin *loop_header = _loop_headers.at(i);
704 assert(loop_header->is_set(BlockBegin::linear_scan_loop_header_flag), "Must be loop header");
705
706 for (int j = 0; j < loop_header->number_of_preds(); j++) {
707 BlockBegin *pred = loop_header->pred_at(j);
708 pred->clear(BlockBegin::linear_scan_loop_end_flag);
709 }
710
711 loop_header->clear(BlockBegin::linear_scan_loop_header_flag);
712
713 for (int block_id = _max_block_id - 1; block_id >= 0; block_id--) {
714 clear_block_in_loop(i, block_id);
715 }
716 _iterative_dominators = true;
717 }
718 }
719 }
720
721 void ComputeLinearScanOrder::assign_loop_depth(BlockBegin* start_block) {
722 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing loop-depth and weight"));
723 init_visited();
724
725 assert(_work_list.is_empty(), "work list must be empty before processing");
726 _work_list.append(start_block);
727
728 do {
729 BlockBegin* cur = _work_list.pop();
730
731 if (!is_visited(cur)) {
732 set_visited(cur);
733 TRACE_LINEAR_SCAN(4, tty->print_cr("Computing loop depth for block B%d", cur->block_id()));
734
735 // compute loop-depth and loop-index for the block
736 assert(cur->loop_depth() == 0, "cannot set loop-depth twice");
737 int i;
738 int loop_depth = 0;
739 int min_loop_idx = -1;
740 for (i = _num_loops - 1; i >= 0; i--) {
741 if (is_block_in_loop(i, cur)) {
742 loop_depth++;
743 min_loop_idx = i;
744 }
745 }
746 cur->set_loop_depth(loop_depth);
747 cur->set_loop_index(min_loop_idx);
748
749 // append all unvisited successors to work list
750 for (i = cur->number_of_sux() - 1; i >= 0; i--) {
751 _work_list.append(cur->sux_at(i));
752 }
753 for (i = cur->number_of_exception_handlers() - 1; i >= 0; i--) {
754 _work_list.append(cur->exception_handler_at(i));
755 }
756 }
757 } while (!_work_list.is_empty());
758 }
759
760
761 BlockBegin* ComputeLinearScanOrder::common_dominator(BlockBegin* a, BlockBegin* b) {
762 assert(a != nullptr && b != nullptr, "must have input blocks");
763
764 _dominator_blocks.clear();
765 while (a != nullptr) {
766 _dominator_blocks.set_bit(a->block_id());
767 assert(a->dominator() != nullptr || a == _linear_scan_order->at(0), "dominator must be initialized");
768 a = a->dominator();
769 }
770 while (b != nullptr && !_dominator_blocks.at(b->block_id())) {
771 assert(b->dominator() != nullptr || b == _linear_scan_order->at(0), "dominator must be initialized");
772 b = b->dominator();
773 }
774
775 assert(b != nullptr, "could not find dominator");
776 return b;
777 }
778
779 void ComputeLinearScanOrder::compute_dominator(BlockBegin* cur, BlockBegin* parent) {
780 init_visited();
781 compute_dominator_impl(cur, parent);
782 }
783
784 void ComputeLinearScanOrder::compute_dominator_impl(BlockBegin* cur, BlockBegin* parent) {
785 // Mark as visited to avoid recursive calls with same parent
786 set_visited(cur);
787
788 if (cur->dominator() == nullptr) {
789 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: initializing dominator of B%d to B%d", cur->block_id(), parent->block_id()));
790 cur->set_dominator(parent);
791
792 } else if (!(cur->is_set(BlockBegin::linear_scan_loop_header_flag) && parent->is_set(BlockBegin::linear_scan_loop_end_flag))) {
793 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()));
794 // Does not hold for exception blocks
795 assert(cur->number_of_preds() > 1 || cur->is_set(BlockBegin::exception_entry_flag), "");
796 cur->set_dominator(common_dominator(cur->dominator(), parent));
797 }
798
799 // Additional edge to xhandler of all our successors
800 // range check elimination needs that the state at the end of a
801 // block be valid in every block it dominates so cur must dominate
802 // the exception handlers of its successors.
803 int num_cur_xhandler = cur->number_of_exception_handlers();
804 for (int j = 0; j < num_cur_xhandler; j++) {
805 BlockBegin* xhandler = cur->exception_handler_at(j);
806 if (!is_visited(xhandler)) {
807 compute_dominator_impl(xhandler, parent);
808 }
809 }
810 }
811
812
813 int ComputeLinearScanOrder::compute_weight(BlockBegin* cur) {
814 BlockBegin* single_sux = nullptr;
815 if (cur->number_of_sux() == 1) {
816 single_sux = cur->sux_at(0);
817 }
818
819 // limit loop-depth to 15 bit (only for security reason, it will never be so big)
820 int weight = (cur->loop_depth() & 0x7FFF) << 16;
821
822 // general macro for short definition of weight flags
823 // the first instance of INC_WEIGHT_IF has the highest priority
824 int cur_bit = 15;
825 #define INC_WEIGHT_IF(condition) if ((condition)) { weight |= (1 << cur_bit); } cur_bit--;
826
827 // this is necessary for the (very rare) case that two successive blocks have
828 // the same loop depth, but a different loop index (can happen for endless loops
829 // with exception handlers)
830 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_header_flag));
831
832 // loop end blocks (blocks that end with a backward branch) are added
833 // after all other blocks of the loop.
834 INC_WEIGHT_IF(!cur->is_set(BlockBegin::linear_scan_loop_end_flag));
835
836 // critical edge split blocks are preferred because than they have a bigger
837 // proability to be completely empty
838 INC_WEIGHT_IF(cur->is_set(BlockBegin::critical_edge_split_flag));
839
840 // exceptions should not be thrown in normal control flow, so these blocks
841 // are added as late as possible
842 INC_WEIGHT_IF(cur->end()->as_Throw() == nullptr && (single_sux == nullptr || single_sux->end()->as_Throw() == nullptr));
843 INC_WEIGHT_IF(cur->end()->as_Return() == nullptr && (single_sux == nullptr || single_sux->end()->as_Return() == nullptr));
844
845 // exceptions handlers are added as late as possible
846 INC_WEIGHT_IF(!cur->is_set(BlockBegin::exception_entry_flag));
847
848 // guarantee that weight is > 0
849 weight |= 1;
850
851 #undef INC_WEIGHT_IF
852 assert(cur_bit >= 0, "too many flags");
853 assert(weight > 0, "weight cannot become negative");
854
855 return weight;
856 }
857
858 bool ComputeLinearScanOrder::ready_for_processing(BlockBegin* cur) {
859 // Discount the edge just traveled.
860 // When the number drops to zero, all forward branches were processed
861 if (dec_forward_branches(cur) != 0) {
862 return false;
863 }
864
865 assert(_linear_scan_order->find(cur) == -1, "block already processed (block can be ready only once)");
866 assert(_work_list.find(cur) == -1, "block already in work-list (block can be ready only once)");
867 return true;
868 }
869
870 void ComputeLinearScanOrder::sort_into_work_list(BlockBegin* cur) {
871 assert(_work_list.find(cur) == -1, "block already in work list");
872
873 int cur_weight = compute_weight(cur);
874
875 // the linear_scan_number is used to cache the weight of a block
876 cur->set_linear_scan_number(cur_weight);
877
878 #ifndef PRODUCT
879 if (StressLinearScan) {
880 _work_list.insert_before(0, cur);
881 return;
882 }
883 #endif
884
885 _work_list.append(nullptr); // provide space for new element
886
887 int insert_idx = _work_list.length() - 1;
888 while (insert_idx > 0 && _work_list.at(insert_idx - 1)->linear_scan_number() > cur_weight) {
889 _work_list.at_put(insert_idx, _work_list.at(insert_idx - 1));
890 insert_idx--;
891 }
892 _work_list.at_put(insert_idx, cur);
893
894 TRACE_LINEAR_SCAN(3, tty->print_cr("Sorted B%d into worklist. new worklist:", cur->block_id()));
895 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()));
896
897 #ifdef ASSERT
898 for (int i = 0; i < _work_list.length(); i++) {
899 assert(_work_list.at(i)->linear_scan_number() > 0, "weight not set");
900 assert(i == 0 || _work_list.at(i - 1)->linear_scan_number() <= _work_list.at(i)->linear_scan_number(), "incorrect order in worklist");
901 }
902 #endif
903 }
904
905 void ComputeLinearScanOrder::append_block(BlockBegin* cur) {
906 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()));
907 assert(_linear_scan_order->find(cur) == -1, "cannot add the same block twice");
908
909 // currently, the linear scan order and code emit order are equal.
910 // therefore the linear_scan_number and the weight of a block must also
911 // be equal.
912 cur->set_linear_scan_number(_linear_scan_order->length());
913 _linear_scan_order->append(cur);
914 }
915
916 void ComputeLinearScanOrder::compute_order(BlockBegin* start_block) {
917 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing final block order"));
918
919 // the start block is always the first block in the linear scan order
920 _linear_scan_order = new BlockList(_num_blocks);
921 append_block(start_block);
922
923 assert(start_block->end()->as_Base() != nullptr, "start block must end with Base-instruction");
924 BlockBegin* std_entry = ((Base*)start_block->end())->std_entry();
925 BlockBegin* osr_entry = ((Base*)start_block->end())->osr_entry();
926
927 BlockBegin* sux_of_osr_entry = nullptr;
928 if (osr_entry != nullptr) {
929 // special handling for osr entry:
930 // ignore the edge between the osr entry and its successor for processing
931 // the osr entry block is added manually below
932 assert(osr_entry->number_of_sux() == 1, "osr entry must have exactly one successor");
933 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");
934
935 sux_of_osr_entry = osr_entry->sux_at(0);
936 dec_forward_branches(sux_of_osr_entry);
937
938 compute_dominator(osr_entry, start_block);
939 _iterative_dominators = true;
940 }
941 compute_dominator(std_entry, start_block);
942
943 // start processing with standard entry block
944 assert(_work_list.is_empty(), "list must be empty before processing");
945
946 if (ready_for_processing(std_entry)) {
947 sort_into_work_list(std_entry);
948 } else {
949 assert(false, "the std_entry must be ready for processing (otherwise, the method has no start block)");
950 }
951
952 do {
953 BlockBegin* cur = _work_list.pop();
954
955 if (cur == sux_of_osr_entry) {
956 // the osr entry block is ignored in normal processing, it is never added to the
957 // work list. Instead, it is added as late as possible manually here.
958 append_block(osr_entry);
959 compute_dominator(cur, osr_entry);
960 }
961 append_block(cur);
962
963 int i;
964 int num_sux = cur->number_of_sux();
965 // changed loop order to get "intuitive" order of if- and else-blocks
966 for (i = 0; i < num_sux; i++) {
967 BlockBegin* sux = cur->sux_at(i);
968 compute_dominator(sux, cur);
969 if (ready_for_processing(sux)) {
970 sort_into_work_list(sux);
971 }
972 }
973 num_sux = cur->number_of_exception_handlers();
974 for (i = 0; i < num_sux; i++) {
975 BlockBegin* sux = cur->exception_handler_at(i);
976 if (ready_for_processing(sux)) {
977 sort_into_work_list(sux);
978 }
979 }
980 } while (_work_list.length() > 0);
981 }
982
983
984 bool ComputeLinearScanOrder::compute_dominators_iter() {
985 bool changed = false;
986 int num_blocks = _linear_scan_order->length();
987
988 assert(_linear_scan_order->at(0)->dominator() == nullptr, "must not have dominator");
989 assert(_linear_scan_order->at(0)->number_of_preds() == 0, "must not have predecessors");
990 for (int i = 1; i < num_blocks; i++) {
991 BlockBegin* block = _linear_scan_order->at(i);
992
993 BlockBegin* dominator = block->pred_at(0);
994 int num_preds = block->number_of_preds();
995
996 TRACE_LINEAR_SCAN(4, tty->print_cr("DOM: Processing B%d", block->block_id()));
997
998 for (int j = 0; j < num_preds; j++) {
999
1000 BlockBegin *pred = block->pred_at(j);
1001 TRACE_LINEAR_SCAN(4, tty->print_cr(" DOM: Subrocessing B%d", pred->block_id()));
1002
1003 if (block->is_set(BlockBegin::exception_entry_flag)) {
1004 dominator = common_dominator(dominator, pred);
1005 int num_pred_preds = pred->number_of_preds();
1006 for (int k = 0; k < num_pred_preds; k++) {
1007 dominator = common_dominator(dominator, pred->pred_at(k));
1008 }
1009 } else {
1010 dominator = common_dominator(dominator, pred);
1011 }
1012 }
1013
1014 if (dominator != block->dominator()) {
1015 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()));
1016
1017 block->set_dominator(dominator);
1018 changed = true;
1019 }
1020 }
1021 return changed;
1022 }
1023
1024 void ComputeLinearScanOrder::compute_dominators() {
1025 TRACE_LINEAR_SCAN(3, tty->print_cr("----- computing dominators (iterative computation reqired: %d)", _iterative_dominators));
1026
1027 // iterative computation of dominators is only required for methods with non-natural loops
1028 // and OSR-methods. For all other methods, the dominators computed when generating the
1029 // linear scan block order are correct.
1030 if (_iterative_dominators) {
1031 do {
1032 TRACE_LINEAR_SCAN(1, tty->print_cr("DOM: next iteration of fix-point calculation"));
1033 } while (compute_dominators_iter());
1034 }
1035
1036 // check that dominators are correct
1037 assert(!compute_dominators_iter(), "fix point not reached");
1038
1039 // Add Blocks to dominates-Array
1040 int num_blocks = _linear_scan_order->length();
1041 for (int i = 0; i < num_blocks; i++) {
1042 BlockBegin* block = _linear_scan_order->at(i);
1043
1044 BlockBegin *dom = block->dominator();
1045 if (dom) {
1046 assert(dom->dominator_depth() != -1, "Dominator must have been visited before");
1047 dom->dominates()->append(block);
1048 block->set_dominator_depth(dom->dominator_depth() + 1);
1049 } else {
1050 block->set_dominator_depth(0);
1051 }
1052 }
1053 }
1054
1055
1056 #ifdef ASSERT
1057 void ComputeLinearScanOrder::print_blocks() {
1058 if (TraceLinearScanLevel >= 2) {
1059 tty->print_cr("----- loop information:");
1060 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1061 BlockBegin* cur = _linear_scan_order->at(block_idx);
1062
1063 tty->print("%4d: B%2d: ", cur->linear_scan_number(), cur->block_id());
1064 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1065 tty->print ("%d ", is_block_in_loop(loop_idx, cur));
1066 }
1067 tty->print_cr(" -> loop_index: %2d, loop_depth: %2d", cur->loop_index(), cur->loop_depth());
1068 }
1069 }
1070
1071 if (TraceLinearScanLevel >= 1) {
1072 tty->print_cr("----- linear-scan block order:");
1073 for (int block_idx = 0; block_idx < _linear_scan_order->length(); block_idx++) {
1074 BlockBegin* cur = _linear_scan_order->at(block_idx);
1075 tty->print("%4d: B%2d loop: %2d depth: %2d", cur->linear_scan_number(), cur->block_id(), cur->loop_index(), cur->loop_depth());
1076
1077 tty->print(cur->is_set(BlockBegin::exception_entry_flag) ? " ex" : " ");
1078 tty->print(cur->is_set(BlockBegin::critical_edge_split_flag) ? " ce" : " ");
1079 tty->print(cur->is_set(BlockBegin::linear_scan_loop_header_flag) ? " lh" : " ");
1080 tty->print(cur->is_set(BlockBegin::linear_scan_loop_end_flag) ? " le" : " ");
1081
1082 if (cur->dominator() != nullptr) {
1083 tty->print(" dom: B%d ", cur->dominator()->block_id());
1084 } else {
1085 tty->print(" dom: null ");
1086 }
1087
1088 if (cur->number_of_preds() > 0) {
1089 tty->print(" preds: ");
1090 for (int j = 0; j < cur->number_of_preds(); j++) {
1091 BlockBegin* pred = cur->pred_at(j);
1092 tty->print("B%d ", pred->block_id());
1093 }
1094 }
1095 if (cur->number_of_sux() > 0) {
1096 tty->print(" sux: ");
1097 for (int j = 0; j < cur->number_of_sux(); j++) {
1098 BlockBegin* sux = cur->sux_at(j);
1099 tty->print("B%d ", sux->block_id());
1100 }
1101 }
1102 if (cur->number_of_exception_handlers() > 0) {
1103 tty->print(" ex: ");
1104 for (int j = 0; j < cur->number_of_exception_handlers(); j++) {
1105 BlockBegin* ex = cur->exception_handler_at(j);
1106 tty->print("B%d ", ex->block_id());
1107 }
1108 }
1109 tty->cr();
1110 }
1111 }
1112 }
1113
1114 void ComputeLinearScanOrder::verify() {
1115 assert(_linear_scan_order->length() == _num_blocks, "wrong number of blocks in list");
1116
1117 if (StressLinearScan) {
1118 // blocks are scrambled when StressLinearScan is used
1119 return;
1120 }
1121
1122 // check that all successors of a block have a higher linear-scan-number
1123 // and that all predecessors of a block have a lower linear-scan-number
1124 // (only backward branches of loops are ignored)
1125 int i;
1126 for (i = 0; i < _linear_scan_order->length(); i++) {
1127 BlockBegin* cur = _linear_scan_order->at(i);
1128
1129 assert(cur->linear_scan_number() == i, "incorrect linear_scan_number");
1130 assert(cur->linear_scan_number() >= 0 && cur->linear_scan_number() == _linear_scan_order->find(cur), "incorrect linear_scan_number");
1131
1132 int j;
1133 for (j = cur->number_of_sux() - 1; j >= 0; j--) {
1134 BlockBegin* sux = cur->sux_at(j);
1135
1136 assert(sux->linear_scan_number() >= 0 && sux->linear_scan_number() == _linear_scan_order->find(sux), "incorrect linear_scan_number");
1137 if (!sux->is_set(BlockBegin::backward_branch_target_flag)) {
1138 assert(cur->linear_scan_number() < sux->linear_scan_number(), "invalid order");
1139 }
1140 if (cur->loop_depth() == sux->loop_depth()) {
1141 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");
1142 }
1143 }
1144
1145 for (j = cur->number_of_preds() - 1; j >= 0; j--) {
1146 BlockBegin* pred = cur->pred_at(j);
1147
1148 assert(pred->linear_scan_number() >= 0 && pred->linear_scan_number() == _linear_scan_order->find(pred), "incorrect linear_scan_number");
1149 if (!cur->is_set(BlockBegin::backward_branch_target_flag)) {
1150 assert(cur->linear_scan_number() > pred->linear_scan_number(), "invalid order");
1151 }
1152 if (cur->loop_depth() == pred->loop_depth()) {
1153 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");
1154 }
1155
1156 assert(cur->dominator()->linear_scan_number() <= cur->pred_at(j)->linear_scan_number(), "dominator must be before predecessors");
1157 }
1158
1159 // check dominator
1160 if (i == 0) {
1161 assert(cur->dominator() == nullptr, "first block has no dominator");
1162 } else {
1163 assert(cur->dominator() != nullptr, "all but first block must have dominator");
1164 }
1165 // Assertion does not hold for exception handlers
1166 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");
1167 }
1168
1169 // check that all loops are continuous
1170 for (int loop_idx = 0; loop_idx < _num_loops; loop_idx++) {
1171 int block_idx = 0;
1172 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "the first block must not be present in any loop");
1173
1174 // skip blocks before the loop
1175 while (block_idx < _num_blocks && !is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1176 block_idx++;
1177 }
1178 // skip blocks of loop
1179 while (block_idx < _num_blocks && is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx))) {
1180 block_idx++;
1181 }
1182 // after the first non-loop block, there must not be another loop-block
1183 while (block_idx < _num_blocks) {
1184 assert(!is_block_in_loop(loop_idx, _linear_scan_order->at(block_idx)), "loop not continuous in linear-scan order");
1185 block_idx++;
1186 }
1187 }
1188 }
1189 #endif // ASSERT
1190
1191
1192 void IR::compute_code() {
1193 assert(is_valid(), "IR must be valid");
1194
1195 ComputeLinearScanOrder compute_order(compilation(), start());
1196 _num_loops = compute_order.num_loops();
1197 _code = compute_order.linear_scan_order();
1198 }
1199
1200
1201 void IR::compute_use_counts() {
1202 // make sure all values coming out of this block get evaluated.
1203 int num_blocks = _code->length();
1204 for (int i = 0; i < num_blocks; i++) {
1205 _code->at(i)->end()->state()->pin_stack_for_linear_scan();
1206 }
1207
1208 // compute use counts
1209 UseCountComputer::compute(_code);
1210 }
1211
1212
1213 void IR::iterate_preorder(BlockClosure* closure) {
1214 assert(is_valid(), "IR must be valid");
1215 start()->iterate_preorder(closure);
1216 }
1217
1218
1219 void IR::iterate_postorder(BlockClosure* closure) {
1220 assert(is_valid(), "IR must be valid");
1221 start()->iterate_postorder(closure);
1222 }
1223
1224 void IR::iterate_linear_scan_order(BlockClosure* closure) {
1225 linear_scan_order()->iterate_forward(closure);
1226 }
1227
1228
1229 #ifndef PRODUCT
1230 class BlockPrinter: public BlockClosure {
1231 private:
1232 InstructionPrinter* _ip;
1233 bool _cfg_only;
1234 bool _live_only;
1235
1236 public:
1237 BlockPrinter(InstructionPrinter* ip, bool cfg_only, bool live_only = false) {
1238 _ip = ip;
1239 _cfg_only = cfg_only;
1240 _live_only = live_only;
1241 }
1242
1243 virtual void block_do(BlockBegin* block) {
1244 if (_cfg_only) {
1245 _ip->print_instr(block); tty->cr();
1246 } else {
1247 block->print_block(*_ip, _live_only);
1248 }
1249 }
1250 };
1251
1252
1253 void IR::print(BlockBegin* start, bool cfg_only, bool live_only) {
1254 ttyLocker ttyl;
1255 InstructionPrinter ip(!cfg_only);
1256 BlockPrinter bp(&ip, cfg_only, live_only);
1257 start->iterate_preorder(&bp);
1258 tty->cr();
1259 }
1260
1261 void IR::print(bool cfg_only, bool live_only) {
1262 if (is_valid()) {
1263 print(start(), cfg_only, live_only);
1264 } else {
1265 tty->print_cr("invalid IR");
1266 }
1267 }
1268 #endif // PRODUCT
1269
1270 #ifdef ASSERT
1271 class EndNotNullValidator : public BlockClosure {
1272 public:
1273 virtual void block_do(BlockBegin* block) {
1274 assert(block->end() != nullptr, "Expect block end to exist.");
1275 }
1276 };
1277
1278 class XentryFlagValidator : public BlockClosure {
1279 public:
1280 virtual void block_do(BlockBegin* block) {
1281 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1282 assert(!block->end()->sux_at(i)->is_set(BlockBegin::exception_entry_flag), "must not be xhandler");
1283 }
1284 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1285 assert(block->exception_handler_at(i)->is_set(BlockBegin::exception_entry_flag), "must be xhandler");
1286 }
1287 }
1288 };
1289
1290 typedef GrowableArray<BlockList*> BlockListList;
1291
1292 // Validation goals:
1293 // - code() length == blocks length
1294 // - code() contents == blocks content
1295 // - Each block's computed predecessors match sux lists (length)
1296 // - Each block's computed predecessors match sux lists (set content)
1297 class PredecessorAndCodeValidator : public BlockClosure {
1298 private:
1299 BlockListList* _predecessors; // Each index i will hold predecessors of block with id i
1300 BlockList* _blocks;
1301
1302 static int cmp(BlockBegin** a, BlockBegin** b) {
1303 return (*a)->block_id() - (*b)->block_id();
1304 }
1305
1306 public:
1307 PredecessorAndCodeValidator(IR* hir) {
1308 ResourceMark rm;
1309 _predecessors = new BlockListList(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), nullptr);
1310 _blocks = new BlockList(BlockBegin::number_of_blocks());
1311
1312 hir->start()->iterate_preorder(this);
1313 if (hir->code() != nullptr) {
1314 assert(hir->code()->length() == _blocks->length(), "must match");
1315 for (int i = 0; i < _blocks->length(); i++) {
1316 assert(hir->code()->contains(_blocks->at(i)), "should be in both lists");
1317 }
1318 }
1319
1320 for (int i = 0; i < _blocks->length(); i++) {
1321 BlockBegin* block = _blocks->at(i);
1322 verify_block_preds_against_collected_preds(block);
1323 }
1324 }
1325
1326 virtual void block_do(BlockBegin* block) {
1327 _blocks->append(block);
1328 collect_predecessors(block);
1329 }
1330
1331 private:
1332 void collect_predecessors(BlockBegin* block) {
1333 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1334 collect_predecessor(block, block->end()->sux_at(i));
1335 }
1336 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1337 collect_predecessor(block, block->exception_handler_at(i));
1338 }
1339 }
1340
1341 void collect_predecessor(BlockBegin* const pred, const BlockBegin* sux) {
1342 BlockList* preds = _predecessors->at_grow(sux->block_id(), nullptr);
1343 if (preds == nullptr) {
1344 preds = new BlockList();
1345 _predecessors->at_put(sux->block_id(), preds);
1346 }
1347 preds->append(pred);
1348 }
1349
1350 void verify_block_preds_against_collected_preds(const BlockBegin* block) const {
1351 BlockList* preds = _predecessors->at(block->block_id());
1352 if (preds == nullptr) {
1353 assert(block->number_of_preds() == 0, "should be the same");
1354 return;
1355 }
1356 assert(preds->length() == block->number_of_preds(), "should be the same");
1357
1358 // clone the pred list so we can mutate it
1359 BlockList* pred_copy = new BlockList();
1360 for (int j = 0; j < block->number_of_preds(); j++) {
1361 pred_copy->append(block->pred_at(j));
1362 }
1363 // sort them in the same order
1364 preds->sort(cmp);
1365 pred_copy->sort(cmp);
1366 for (int j = 0; j < block->number_of_preds(); j++) {
1367 assert(preds->at(j) == pred_copy->at(j), "must match");
1368 }
1369 }
1370 };
1371
1372 class VerifyBlockBeginField : public BlockClosure {
1373 public:
1374 virtual void block_do(BlockBegin* block) {
1375 for (Instruction* cur = block; cur != nullptr; cur = cur->next()) {
1376 assert(cur->block() == block, "Block begin is not correct");
1377 }
1378 }
1379 };
1380
1381 class ValidateEdgeMutuality : public BlockClosure {
1382 public:
1383 virtual void block_do(BlockBegin* block) {
1384 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1385 assert(block->end()->sux_at(i)->is_predecessor(block), "Block's successor should have it as predecessor");
1386 }
1387
1388 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1389 assert(block->exception_handler_at(i)->is_predecessor(block), "Block's exception handler should have it as predecessor");
1390 }
1391
1392 for (int i = 0; i < block->number_of_preds(); i++) {
1393 assert(block->pred_at(i) != nullptr, "Predecessor must exist");
1394 assert(block->pred_at(i)->end() != nullptr, "Predecessor end must exist");
1395 bool is_sux = block->pred_at(i)->end()->is_sux(block);
1396 bool is_xhandler = block->pred_at(i)->is_exception_handler(block);
1397 assert(is_sux || is_xhandler, "Block's predecessor should have it as successor or xhandler");
1398 }
1399 }
1400 };
1401
1402 void IR::expand_with_neighborhood(BlockList& blocks) {
1403 int original_size = blocks.length();
1404 for (int h = 0; h < original_size; h++) {
1405 BlockBegin* block = blocks.at(h);
1406
1407 for (int i = 0; i < block->end()->number_of_sux(); i++) {
1408 if (!blocks.contains(block->end()->sux_at(i))) {
1409 blocks.append(block->end()->sux_at(i));
1410 }
1411 }
1412
1413 for (int i = 0; i < block->number_of_preds(); i++) {
1414 if (!blocks.contains(block->pred_at(i))) {
1415 blocks.append(block->pred_at(i));
1416 }
1417 }
1418
1419 for (int i = 0; i < block->number_of_exception_handlers(); i++) {
1420 if (!blocks.contains(block->exception_handler_at(i))) {
1421 blocks.append(block->exception_handler_at(i));
1422 }
1423 }
1424 }
1425 }
1426
1427 void IR::verify_local(BlockList& blocks) {
1428 EndNotNullValidator ennv;
1429 blocks.iterate_forward(&ennv);
1430
1431 ValidateEdgeMutuality vem;
1432 blocks.iterate_forward(&vem);
1433
1434 VerifyBlockBeginField verifier;
1435 blocks.iterate_forward(&verifier);
1436 }
1437
1438 void IR::verify() {
1439 XentryFlagValidator xe;
1440 iterate_postorder(&xe);
1441
1442 PredecessorAndCodeValidator pv(this);
1443
1444 EndNotNullValidator ennv;
1445 iterate_postorder(&ennv);
1446
1447 ValidateEdgeMutuality vem;
1448 iterate_postorder(&vem);
1449
1450 VerifyBlockBeginField verifier;
1451 iterate_postorder(&verifier);
1452 }
1453 #endif // ASSERT
1454
1455 void SubstitutionResolver::visit(Value* v) {
1456 Value v0 = *v;
1457 if (v0) {
1458 Value vs = v0->subst();
1459 if (vs != v0) {
1460 *v = v0->subst();
1461 }
1462 }
1463 }
1464
1465 #ifdef ASSERT
1466 class SubstitutionChecker: public ValueVisitor {
1467 void visit(Value* v) {
1468 Value v0 = *v;
1469 if (v0) {
1470 Value vs = v0->subst();
1471 assert(vs == v0, "missed substitution");
1472 }
1473 }
1474 };
1475 #endif
1476
1477
1478 void SubstitutionResolver::block_do(BlockBegin* block) {
1479 Instruction* last = nullptr;
1480 for (Instruction* n = block; n != nullptr;) {
1481 n->values_do(this);
1482 // need to remove this instruction from the instruction stream
1483 if (n->subst() != n) {
1484 guarantee(last != nullptr, "must have last");
1485 last->set_next(n->next());
1486 } else {
1487 last = n;
1488 }
1489 n = last->next();
1490 }
1491
1492 #ifdef ASSERT
1493 SubstitutionChecker check_substitute;
1494 if (block->state()) block->state()->values_do(&check_substitute);
1495 block->block_values_do(&check_substitute);
1496 if (block->end() && block->end()->state()) block->end()->state()->values_do(&check_substitute);
1497 #endif
1498 }