1 /*
2 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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23 */
24
25 #include "libadt/vectset.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "memory/resourceArea.hpp"
28 #include "opto/block.hpp"
29 #include "opto/c2compiler.hpp"
30 #include "opto/callnode.hpp"
31 #include "opto/cfgnode.hpp"
32 #include "opto/chaitin.hpp"
33 #include "opto/machnode.hpp"
34 #include "opto/opcodes.hpp"
35 #include "opto/phaseX.hpp"
36 #include "opto/rootnode.hpp"
37 #include "opto/runtime.hpp"
38 #include "runtime/deoptimization.hpp"
39
40 // Portions of code courtesy of Clifford Click
41
42 // Optimization - Graph Style
43
44 // To avoid float value underflow
45 #define MIN_BLOCK_FREQUENCY 1.e-35f
46
47 //----------------------------schedule_node_into_block-------------------------
48 // Insert node n into block b. Look for projections of n and make sure they
49 // are in b also.
50 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
51 // Set basic block of n, Add n to b,
52 map_node_to_block(n, b);
53 b->add_inst(n);
54
55 // After Matching, nearly any old Node may have projections trailing it.
56 // These are usually machine-dependent flags. In any case, they might
57 // float to another block below this one. Move them up.
58 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
59 Node* use = n->fast_out(i);
60 if (use->is_Proj()) {
61 Block* buse = get_block_for_node(use);
62 if (buse != b) { // In wrong block?
63 if (buse != nullptr) {
64 buse->find_remove(use); // Remove from wrong block
65 }
66 map_node_to_block(use, b);
67 b->add_inst(use);
68 }
69 }
70 }
71 }
72
73 //----------------------------replace_block_proj_ctrl-------------------------
74 // Nodes that have is_block_proj() nodes as their control need to use
75 // the appropriate Region for their actual block as their control since
76 // the projection will be in a predecessor block.
77 void PhaseCFG::replace_block_proj_ctrl( Node *n ) {
78 const Node *in0 = n->in(0);
79 assert(in0 != nullptr, "Only control-dependent");
80 const Node *p = in0->is_block_proj();
81 if (p != nullptr && p != n) { // Control from a block projection?
82 assert(!n->pinned() || n->is_MachConstantBase(), "only pinned MachConstantBase node is expected here");
83 // Find trailing Region
84 Block *pb = get_block_for_node(in0); // Block-projection already has basic block
85 uint j = 0;
86 if (pb->_num_succs != 1) { // More then 1 successor?
87 // Search for successor
88 uint max = pb->number_of_nodes();
89 assert( max > 1, "" );
90 uint start = max - pb->_num_succs;
91 // Find which output path belongs to projection
92 for (j = start; j < max; j++) {
93 if( pb->get_node(j) == in0 )
94 break;
95 }
96 assert( j < max, "must find" );
97 // Change control to match head of successor basic block
98 j -= start;
99 }
100 n->set_req(0, pb->_succs[j]->head());
101 }
102 }
103
104 bool PhaseCFG::is_dominator(Node* dom_node, Node* node) {
105 assert(is_CFG(node) && is_CFG(dom_node), "node and dom_node must be CFG nodes");
106 if (dom_node == node) {
107 return true;
108 }
109 Block* d = find_block_for_node(dom_node);
110 Block* n = find_block_for_node(node);
111 assert(n != nullptr && d != nullptr, "blocks must exist");
112
113 if (d == n) {
114 if (dom_node->is_block_start()) {
115 return true;
116 }
117 if (node->is_block_start()) {
118 return false;
119 }
120 if (dom_node->is_block_proj()) {
121 return false;
122 }
123 if (node->is_block_proj()) {
124 return true;
125 }
126
127 assert(is_control_proj_or_safepoint(node), "node must be control projection or safepoint");
128 assert(is_control_proj_or_safepoint(dom_node), "dom_node must be control projection or safepoint");
129
130 // Neither 'node' nor 'dom_node' is a block start or block projection.
131 // Check if 'dom_node' is above 'node' in the control graph.
132 if (is_dominating_control(dom_node, node)) {
133 return true;
134 }
135
136 #ifdef ASSERT
137 // If 'dom_node' does not dominate 'node' then 'node' has to dominate 'dom_node'
138 if (!is_dominating_control(node, dom_node)) {
139 node->dump();
140 dom_node->dump();
141 assert(false, "neither dom_node nor node dominates the other");
142 }
143 #endif
144
145 return false;
146 }
147 return d->dom_lca(n) == d;
148 }
149
150 bool PhaseCFG::is_CFG(Node* n) {
151 return n->is_block_proj() || n->is_block_start() || is_control_proj_or_safepoint(n);
152 }
153
154 bool PhaseCFG::is_control_proj_or_safepoint(Node* n) const {
155 bool result = n->is_ReachabilityFence() ||
156 (n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_SafePoint) ||
157 (n->is_Proj() && n->as_Proj()->bottom_type() == Type::CONTROL);
158 assert(!n->is_Proj() ||
159 n->as_Proj()->bottom_type() != Type::CONTROL ||
160 n->as_Proj()->_con == 0, "If control projection, it must be projection 0");
161 return result;
162 }
163
164 Block* PhaseCFG::find_block_for_node(Node* n) const {
165 if (n->is_block_start() || n->is_block_proj()) {
166 return get_block_for_node(n);
167 } else {
168 // Walk the control graph up if 'n' is not a block start nor a block projection. In this case 'n' must be
169 // an unmatched control projection or a not yet matched safepoint precedence edge in the middle of a block.
170 assert(is_control_proj_or_safepoint(n), "must be control projection or safepoint");
171 Node* ctrl = n->in(0);
172 while (!ctrl->is_block_start()) {
173 ctrl = ctrl->in(0);
174 }
175 return get_block_for_node(ctrl);
176 }
177 }
178
179 // Walk up the control graph from 'n' and check if 'dom_ctrl' is found.
180 bool PhaseCFG::is_dominating_control(Node* dom_ctrl, Node* n) {
181 Node* ctrl = n->in(0);
182 while (!ctrl->is_block_start()) {
183 if (ctrl == dom_ctrl) {
184 return true;
185 }
186 ctrl = ctrl->in(0);
187 }
188 return false;
189 }
190
191
192 //------------------------------schedule_pinned_nodes--------------------------
193 // Set the basic block for Nodes pinned into blocks
194 void PhaseCFG::schedule_pinned_nodes(VectorSet &visited) {
195 // Allocate node stack of size C->live_nodes()+8 to avoid frequent realloc
196 GrowableArray <Node*> spstack(C->live_nodes() + 8);
197 spstack.push(_root);
198 while (spstack.is_nonempty()) {
199 Node* node = spstack.pop();
200 if (!visited.test_set(node->_idx)) { // Test node and flag it as visited
201 if (node->pinned() && !has_block(node)) { // Pinned? Nail it down!
202 assert(node->in(0), "pinned Node must have Control");
203 // Before setting block replace block_proj control edge
204 replace_block_proj_ctrl(node);
205 Node* input = node->in(0);
206 while (!input->is_block_start()) {
207 input = input->in(0);
208 }
209 Block* block = get_block_for_node(input); // Basic block of controlling input
210 schedule_node_into_block(node, block);
211 }
212
213 // If the node has precedence edges (added when CastPP nodes are
214 // removed in final_graph_reshaping), fix the control of the
215 // node to cover the precedence edges and remove the
216 // dependencies.
217 Node* n = nullptr;
218 for (uint i = node->len()-1; i >= node->req(); i--) {
219 Node* m = node->in(i);
220 if (m == nullptr) continue;
221 assert(is_CFG(m), "must be a CFG node");
222 node->rm_prec(i);
223 if (n == nullptr) {
224 n = m;
225 } else {
226 assert(is_dominator(n, m) || is_dominator(m, n), "one must dominate the other");
227 n = is_dominator(n, m) ? m : n;
228 }
229 }
230 if (n != nullptr) {
231 assert(node->in(0), "control should have been set");
232 assert(is_dominator(n, node->in(0)) || is_dominator(node->in(0), n), "one must dominate the other");
233 if (!is_dominator(n, node->in(0))) {
234 node->set_req(0, n);
235 }
236 }
237
238 // process all inputs that are non null
239 for (int i = node->len()-1; i >= 0; --i) {
240 if (node->in(i) != nullptr) {
241 spstack.push(node->in(i));
242 }
243 }
244 }
245 }
246 }
247
248 // Assert that new input b2 is dominated by all previous inputs.
249 // Check this by by seeing that it is dominated by b1, the deepest
250 // input observed until b2.
251 static void assert_dom(Block* b1, Block* b2, Node* n, const PhaseCFG* cfg) {
252 if (b1 == nullptr) return;
253 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
254 Block* tmp = b2;
255 while (tmp != b1 && tmp != nullptr) {
256 tmp = tmp->_idom;
257 }
258 if (tmp != b1) {
259 #ifdef ASSERT
260 // Detected an unschedulable graph. Print some nice stuff and die.
261 tty->print_cr("!!! Unschedulable graph !!!");
262 for (uint j=0; j<n->len(); j++) { // For all inputs
263 Node* inn = n->in(j); // Get input
264 if (inn == nullptr) continue; // Ignore null, missing inputs
265 Block* inb = cfg->get_block_for_node(inn);
266 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
267 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
268 inn->dump();
269 }
270 tty->print("Failing node: ");
271 n->dump();
272 assert(false, "unschedulable graph");
273 #endif
274 cfg->C->record_failure("unschedulable graph");
275 }
276 }
277
278 static Block* find_deepest_input(Node* n, const PhaseCFG* cfg) {
279 // Find the last input dominated by all other inputs.
280 Block* deepb = nullptr; // Deepest block so far
281 int deepb_dom_depth = 0;
282 for (uint k = 0; k < n->len(); k++) { // For all inputs
283 Node* inn = n->in(k); // Get input
284 if (inn == nullptr) continue; // Ignore null, missing inputs
285 Block* inb = cfg->get_block_for_node(inn);
286 assert(inb != nullptr, "must already have scheduled this input");
287 if (deepb_dom_depth < (int) inb->_dom_depth) {
288 // The new inb must be dominated by the previous deepb.
289 // The various inputs must be linearly ordered in the dom
290 // tree, or else there will not be a unique deepest block.
291 assert_dom(deepb, inb, n, cfg);
292 if (cfg->C->failing()) {
293 return nullptr;
294 }
295 deepb = inb; // Save deepest block
296 deepb_dom_depth = deepb->_dom_depth;
297 }
298 }
299 assert(deepb != nullptr, "must be at least one input to n");
300 return deepb;
301 }
302
303
304 //------------------------------schedule_early---------------------------------
305 // Find the earliest Block any instruction can be placed in. Some instructions
306 // are pinned into Blocks. Unpinned instructions can appear in last block in
307 // which all their inputs occur.
308 bool PhaseCFG::schedule_early(VectorSet &visited, Node_Stack &roots) {
309 // Allocate stack with enough space to avoid frequent realloc
310 Node_Stack nstack(roots.size() + 8);
311 // _root will be processed among C->top() inputs
312 roots.push(C->top(), 0);
313 visited.set(C->top()->_idx);
314
315 while (roots.size() != 0) {
316 // Use local variables nstack_top_n & nstack_top_i to cache values
317 // on stack's top.
318 Node* parent_node = roots.node();
319 uint input_index = 0;
320 roots.pop();
321
322 while (true) {
323 if (input_index == 0) {
324 // Fixup some control. Constants without control get attached
325 // to root and nodes that use is_block_proj() nodes should be attached
326 // to the region that starts their block.
327 const Node* control_input = parent_node->in(0);
328 if (control_input != nullptr) {
329 replace_block_proj_ctrl(parent_node);
330 } else {
331 // Is a constant with NO inputs?
332 if (parent_node->req() == 1) {
333 parent_node->set_req(0, _root);
334 }
335 }
336 }
337
338 // First, visit all inputs and force them to get a block. If an
339 // input is already in a block we quit following inputs (to avoid
340 // cycles). Instead we put that Node on a worklist to be handled
341 // later (since IT'S inputs may not have a block yet).
342
343 // Assume all n's inputs will be processed
344 bool done = true;
345
346 while (input_index < parent_node->len()) {
347 Node* in = parent_node->in(input_index++);
348 if (in == nullptr) {
349 continue;
350 }
351
352 int is_visited = visited.test_set(in->_idx);
353 if (!has_block(in)) {
354 if (is_visited) {
355 assert(false, "graph should be schedulable");
356 return false;
357 }
358 // Save parent node and next input's index.
359 nstack.push(parent_node, input_index);
360 // Process current input now.
361 parent_node = in;
362 input_index = 0;
363 // Not all n's inputs processed.
364 done = false;
365 break;
366 } else if (!is_visited) {
367 // Visit this guy later, using worklist
368 roots.push(in, 0);
369 }
370 }
371
372 if (done) {
373 // All of n's inputs have been processed, complete post-processing.
374
375 // Some instructions are pinned into a block. These include Region,
376 // Phi, Start, Return, and other control-dependent instructions and
377 // any projections which depend on them.
378 if (!parent_node->pinned()) {
379 // Set earliest legal block.
380 Block* earliest_block = find_deepest_input(parent_node, this);
381 if (C->failing()) {
382 return false;
383 }
384 map_node_to_block(parent_node, earliest_block);
385 } else {
386 assert(get_block_for_node(parent_node) == get_block_for_node(parent_node->in(0)), "Pinned Node should be at the same block as its control edge");
387 }
388
389 if (nstack.is_empty()) {
390 // Finished all nodes on stack.
391 // Process next node on the worklist 'roots'.
392 break;
393 }
394 // Get saved parent node and next input's index.
395 parent_node = nstack.node();
396 input_index = nstack.index();
397 nstack.pop();
398 }
399 }
400 }
401 return true;
402 }
403
404 //------------------------------dom_lca----------------------------------------
405 // Find least common ancestor in dominator tree
406 // LCA is a current notion of LCA, to be raised above 'this'.
407 // As a convenient boundary condition, return 'this' if LCA is null.
408 // Find the LCA of those two nodes.
409 Block* Block::dom_lca(Block* LCA) {
410 if (LCA == nullptr || LCA == this) return this;
411
412 Block* anc = this;
413 while (anc->_dom_depth > LCA->_dom_depth)
414 anc = anc->_idom; // Walk up till anc is as high as LCA
415
416 while (LCA->_dom_depth > anc->_dom_depth)
417 LCA = LCA->_idom; // Walk up till LCA is as high as anc
418
419 while (LCA != anc) { // Walk both up till they are the same
420 LCA = LCA->_idom;
421 anc = anc->_idom;
422 }
423
424 return LCA;
425 }
426
427 //--------------------------raise_LCA_above_use--------------------------------
428 // We are placing a definition, and have been given a def->use edge.
429 // The definition must dominate the use, so move the LCA upward in the
430 // dominator tree to dominate the use. If the use is a phi, adjust
431 // the LCA only with the phi input paths which actually use this def.
432 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) {
433 Block* buse = cfg->get_block_for_node(use);
434 if (buse == nullptr) return LCA; // Unused killing Projs have no use block
435 if (!use->is_Phi()) return buse->dom_lca(LCA);
436 uint pmax = use->req(); // Number of Phi inputs
437 // Why does not this loop just break after finding the matching input to
438 // the Phi? Well...it's like this. I do not have true def-use/use-def
439 // chains. Means I cannot distinguish, from the def-use direction, which
440 // of many use-defs lead from the same use to the same def. That is, this
441 // Phi might have several uses of the same def. Each use appears in a
442 // different predecessor block. But when I enter here, I cannot distinguish
443 // which use-def edge I should find the predecessor block for. So I find
444 // them all. Means I do a little extra work if a Phi uses the same value
445 // more than once.
446 for (uint j=1; j<pmax; j++) { // For all inputs
447 if (use->in(j) == def) { // Found matching input?
448 Block* pred = cfg->get_block_for_node(buse->pred(j));
449 LCA = pred->dom_lca(LCA);
450 }
451 }
452 return LCA;
453 }
454
455 //----------------------------raise_LCA_above_marks----------------------------
456 // Return a new LCA that dominates LCA and any of its marked predecessors.
457 // Search all my parents up to 'early' (exclusive), looking for predecessors
458 // which are marked with the given index. Return the LCA (in the dom tree)
459 // of all marked blocks. If there are none marked, return the original
460 // LCA.
461 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) {
462 assert(early->dominates(LCA), "precondition failed");
463 Block_List worklist;
464 worklist.push(LCA);
465 while (worklist.size() > 0) {
466 Block* mid = worklist.pop();
467 if (mid == early) continue; // stop searching here
468
469 // Test and set the visited bit.
470 if (mid->raise_LCA_visited() == mark) continue; // already visited
471
472 // Don't process the current LCA, otherwise the search may terminate early
473 if (mid != LCA && mid->raise_LCA_mark() == mark) {
474 // Raise the LCA.
475 LCA = mid->dom_lca(LCA);
476 if (LCA == early) break; // stop searching everywhere
477 assert(early->dominates(LCA), "unsound LCA update");
478 // Resume searching at that point, skipping intermediate levels.
479 worklist.push(LCA);
480 if (LCA == mid)
481 continue; // Don't mark as visited to avoid early termination.
482 } else {
483 // Keep searching through this block's predecessors.
484 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
485 Block* mid_parent = cfg->get_block_for_node(mid->pred(j));
486 worklist.push(mid_parent);
487 }
488 }
489 mid->set_raise_LCA_visited(mark);
490 }
491 return LCA;
492 }
493
494 //--------------------------memory_early_block--------------------------------
495 // This is a variation of find_deepest_input, the heart of schedule_early.
496 // Find the "early" block for a load, if we considered only memory and
497 // address inputs, that is, if other data inputs were ignored.
498 //
499 // Because a subset of edges are considered, the resulting block will
500 // be earlier (at a shallower dom_depth) than the true schedule_early
501 // point of the node. We compute this earlier block as a more permissive
502 // site for anti-dependency insertion, but only if subsume_loads is enabled.
503 static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) {
504 Node* base;
505 Node* index;
506 Node* store = load->in(MemNode::Memory);
507 load->as_Mach()->memory_inputs(base, index);
508
509 assert(base != NodeSentinel && index != NodeSentinel,
510 "unexpected base/index inputs");
511
512 Node* mem_inputs[4];
513 int mem_inputs_length = 0;
514 if (base != nullptr) mem_inputs[mem_inputs_length++] = base;
515 if (index != nullptr) mem_inputs[mem_inputs_length++] = index;
516 if (store != nullptr) mem_inputs[mem_inputs_length++] = store;
517
518 // In the comparison below, add one to account for the control input,
519 // which may be null, but always takes up a spot in the in array.
520 if (mem_inputs_length + 1 < (int) load->req()) {
521 // This "load" has more inputs than just the memory, base and index inputs.
522 // For purposes of checking anti-dependences, we need to start
523 // from the early block of only the address portion of the instruction,
524 // and ignore other blocks that may have factored into the wider
525 // schedule_early calculation.
526 if (load->in(0) != nullptr) mem_inputs[mem_inputs_length++] = load->in(0);
527
528 Block* deepb = nullptr; // Deepest block so far
529 int deepb_dom_depth = 0;
530 for (int i = 0; i < mem_inputs_length; i++) {
531 Block* inb = cfg->get_block_for_node(mem_inputs[i]);
532 if (deepb_dom_depth < (int) inb->_dom_depth) {
533 // The new inb must be dominated by the previous deepb.
534 // The various inputs must be linearly ordered in the dom
535 // tree, or else there will not be a unique deepest block.
536 assert_dom(deepb, inb, load, cfg);
537 if (cfg->C->failing()) {
538 return nullptr;
539 }
540 deepb = inb; // Save deepest block
541 deepb_dom_depth = deepb->_dom_depth;
542 }
543 }
544 early = deepb;
545 }
546
547 return early;
548 }
549
550 // This function is used by raise_above_anti_dependences to find unrelated loads for stores in implicit null checks.
551 bool PhaseCFG::unrelated_load_in_store_null_block(Node* store, Node* load) {
552 // We expect an anti-dependence edge from 'load' to 'store', except when
553 // implicit_null_check() has hoisted 'store' above its early block to
554 // perform an implicit null check, and 'load' is placed in the null
555 // block. In this case it is safe to ignore the anti-dependence, as the
556 // null block is only reached if 'store' tries to write to null object and
557 // 'load' read from non-null object (there is preceding check for that)
558 // These objects can't be the same.
559 Block* store_block = get_block_for_node(store);
560 Block* load_block = get_block_for_node(load);
561 Node* end = store_block->end();
562 if (end->is_MachNullCheck() && (end->in(1) == store) && store_block->dominates(load_block)) {
563 Node* if_true = end->find_out_with(Op_IfTrue);
564 assert(if_true != nullptr, "null check without null projection");
565 Node* null_block_region = if_true->find_out_with(Op_Region);
566 assert(null_block_region != nullptr, "null check without null region");
567 return get_block_for_node(null_block_region) == load_block;
568 }
569 return false;
570 }
571
572 class DefUseMemStatesQueue : public StackObj {
573 private:
574 class DefUsePair : public StackObj {
575 private:
576 Node* _def; // memory state
577 Node* _use; // use of the memory state that also modifies the memory state
578
579 public:
580 DefUsePair(Node* def, Node* use) :
581 _def(def), _use(use) {
582 }
583
584 DefUsePair() :
585 _def(nullptr), _use(nullptr) {
586 }
587
588 Node* def() const {
589 return _def;
590 }
591
592 Node* use() const {
593 return _use;
594 }
595 };
596
597 GrowableArray<DefUsePair> _queue;
598 Unique_Node_List _worklist_visited; // visited mergemem nodes
599
600 bool already_enqueued(Node* def_mem, PhiNode* use_phi) const {
601 // def_mem is one of the inputs of use_phi and at least one input of use_phi is
602 // not def_mem. It's however possible that use_phi has def_mem as input multiple
603 // times. If that happens, use_phi is recorded as a use of def_mem multiple
604 // times as well. When PhaseCFG::raise_above_anti_dependences() goes over
605 // uses of def_mem and enqueues them for processing, use_phi would then be
606 // enqueued for processing multiple times when it only needs to be
607 // processed once. The code below checks if use_phi as a use of def_mem was
608 // already enqueued to avoid redundant processing of use_phi.
609 int j = _queue.length()-1;
610 // If there are any use of def_mem already enqueued, they were enqueued
611 // last (all use of def_mem are processed in one go).
612 for (; j >= 0; j--) {
613 const DefUsePair& def_use_pair = _queue.at(j);
614 if (def_use_pair.def() != def_mem) {
615 // We're done with the uses of def_mem
616 break;
617 }
618 if (def_use_pair.use() == use_phi) {
619 return true;
620 }
621 }
622 #ifdef ASSERT
623 for (; j >= 0; j--) {
624 const DefUsePair& def_use_pair = _queue.at(j);
625 assert(def_use_pair.def() != def_mem, "Should be done with the uses of def_mem");
626 }
627 #endif
628 return false;
629 }
630
631 public:
632 DefUseMemStatesQueue(ResourceArea* area) {
633 }
634
635 void push(Node* def_mem_state, Node* use_mem_state) {
636 if (use_mem_state->is_MergeMem()) {
637 // Be sure we don't get into combinatorial problems.
638 if (_worklist_visited.member(use_mem_state)) {
639 // already on work list; do not repeat
640 return;
641 }
642 _worklist_visited.push(use_mem_state);
643 } else if (use_mem_state->is_Phi()) {
644 // A Phi could have the same mem as input multiple times. If that's the case, we don't need to enqueue it
645 // more than once. We otherwise allow phis to be repeated; they can merge two relevant states.
646 if (already_enqueued(def_mem_state, use_mem_state->as_Phi())) {
647 return;
648 }
649 }
650
651 _queue.push(DefUsePair(def_mem_state, use_mem_state));
652 }
653
654 bool is_nonempty() const {
655 return _queue.is_nonempty();
656 }
657
658 Node* top_def() const {
659 return _queue.top().def();
660 }
661
662 Node* top_use() const {
663 return _queue.top().use();
664 }
665
666 void pop() {
667 _queue.pop();
668 }
669 };
670
671 // Enforce a scheduling of the given 'load' that ensures anti-dependent stores
672 // do not overwrite the load's input memory state before the load executes.
673 //
674 // The given 'load' has a current scheduling range in the dominator tree that
675 // starts at the load's early block (computed in schedule_early) and ends at
676 // the given 'LCA' block for the load. However, there may still exist
677 // anti-dependent stores between the early block and the LCA that overwrite
678 // memory that the load must witness. For such stores, we must
679 //
680 // 1. raise the load's LCA to force the load to (eventually) be scheduled at
681 // latest in the store's block, and
682 // 2. if the load may get scheduled in the store's block, additionally insert
683 // an anti-dependence edge (i.e., precedence edge) from the load to the
684 // store to ensure LCM schedules the load before the store within the
685 // block.
686 //
687 // For a given store, we say that the store is on a _distinct_ control-flow
688 // path relative to the load if there are no paths from early to LCA that go
689 // through the store's block. Such stores are not anti-dependent, and there is
690 // no need to update the LCA nor to add anti-dependence edges.
691 //
692 // Due to the presence of loops, we must also raise the LCA above
693 // anti-dependent memory Phis. We defer the details (see later comments in the
694 // method) and for now look at an example without loops.
695 //
696 // CFG DOMINATOR TREE
697 //
698 // B1 (early,L) B1
699 // |\________ /\\___
700 // | \ / \ \
701 // B2 (L,S) \ B2 B7 B6
702 // / \ \ /\\___
703 // B3 B4 (S) B7 (S) / \ \
704 // \ / / B3 B4 B5
705 // B5 (LCA,L) /
706 // \ ____/
707 // \ /
708 // B6
709 //
710 // Here, the load's scheduling range when calling raise_above_anti_dependences
711 // is between early and LCA in the dominator tree, i.e., in block B1, B2, or B5
712 // (indicated with "L"). However, there are a number of stores (indicated with
713 // "S") that overwrite the memory which the load must witness. First, consider
714 // the store in B4. We cannot legally schedule the load in B4, so an
715 // anti-dependence edge is redundant. However, we must raise the LCA above
716 // B4, which means that the updated LCA is B2. Now, consider the store in B2.
717 // The LCA is already B2, so we do not need to raise it any further.
718 // If we, eventually, decide to schedule the load in B2, it could happen that
719 // LCM decides to place the load after the anti-dependent store in B2.
720 // Therefore, we now need to add an anti-dependence edge between the load and
721 // the B2 store, ensuring that the load is scheduled before the store. Finally,
722 // the store in B7 is on a distinct control-flow path. Therefore, B7 requires
723 // no action.
724 //
725 // The raise_above_anti_dependences method returns the updated LCA and ensures
726 // there are no anti-dependent stores in any block between the load's early
727 // block and the updated LCA. Any stores in the updated LCA will have new
728 // anti-dependence edges back to the load. The caller may schedule the load in
729 // the updated LCA, or it may hoist the load above the updated LCA, if the
730 // updated LCA is not the early block.
731 Block* PhaseCFG::raise_above_anti_dependences(Block* LCA, Node* load, const bool verify) {
732 ResourceMark rm;
733 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
734 assert(LCA != nullptr, "");
735 DEBUG_ONLY(Block* LCA_orig = LCA);
736
737 // Compute the alias index. Loads and stores with different alias indices
738 // do not need anti-dependence edges.
739 int load_alias_idx = C->get_alias_index(load->adr_type());
740 #ifdef ASSERT
741 assert(Compile::AliasIdxTop <= load_alias_idx && load_alias_idx < C->num_alias_types(), "Invalid alias index");
742 if (load_alias_idx == Compile::AliasIdxBot && C->do_aliasing() &&
743 (PrintOpto || VerifyAliases ||
744 (PrintMiscellaneous && (WizardMode || Verbose)))) {
745 // Load nodes should not consume all of memory.
746 // Reporting a bottom type indicates a bug in adlc.
747 // If some particular type of node validly consumes all of memory,
748 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
749 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
750 load->dump(2);
751 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
752 }
753 #endif
754
755 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
756 // It is impossible to spoil this load by putting stores before it,
757 // because we know that the stores will never update the value
758 // which 'load' must witness.
759 return LCA;
760 }
761
762 node_idx_t load_index = load->_idx;
763
764 // Record the earliest legal placement of 'load', as determined by the unique
765 // point in the dominator tree where all memory effects and other inputs are
766 // first available (computed by schedule_early). For normal loads, 'early' is
767 // the shallowest place (dominator-tree wise) to look for anti-dependences
768 // between this load and any store.
769 Block* early = get_block_for_node(load);
770
771 // If we are subsuming loads, compute an "early" block that only considers
772 // memory or address inputs. This block may be different from the
773 // schedule_early block when it is at an even shallower depth in the
774 // dominator tree, and allow for a broader discovery of anti-dependences.
775 if (C->subsume_loads()) {
776 early = memory_early_block(load, early, this);
777 if (C->failing()) {
778 return nullptr;
779 }
780 }
781
782 assert(early->dominates(LCA_orig), "precondition failed");
783
784 ResourceArea* area = Thread::current()->resource_area();
785
786 // Bookkeeping of possibly anti-dependent stores that we find outside the
787 // early block and that may need anti-dependence edges. Note that stores in
788 // non_early_stores are not necessarily dominated by early. The search starts
789 // from initial_mem, which can reside in a block that dominates early, and
790 // therefore, stores we find may be in blocks that are on completely distinct
791 // control-flow paths compared to early. However, in the end, only stores in
792 // blocks dominated by early matter. The reason for bookkeeping not only
793 // relevant stores is efficiency: we lazily record all possible
794 // anti-dependent stores and add anti-dependence edges only to the relevant
795 // ones at the very end of this method when we know the final updated LCA.
796 Node_List non_early_stores(area);
797
798 // Whether we must raise the LCA after the main worklist loop below.
799 bool must_raise_LCA_above_marks = false;
800
801 // The input load uses some memory state (initial_mem).
802 Node* initial_mem = load->in(MemNode::Memory);
803 // To find anti-dependences we must look for users of the same memory state.
804 // To do this, we search the memory graph downwards from initial_mem. During
805 // this search, we encounter different types of nodes that we handle
806 // according to the following three categories:
807 //
808 // - MergeMems
809 // - Memory-state-modifying nodes (informally referred to as "stores" above
810 // and below)
811 // - Memory Phis
812 //
813 // MergeMems do not modify the memory state. Anti-dependent stores or memory
814 // Phis may, however, exist downstream of MergeMems. Therefore, we must
815 // permit the search to continue through MergeMems. Stores may raise the LCA
816 // and may potentially also require an anti-dependence edge. Memory Phis may
817 // raise the LCA but never require anti-dependence edges. See the comments
818 // throughout the worklist loop below for further details.
819 //
820 // It may be useful to think of the anti-dependence search as traversing a
821 // tree rooted at initial_mem, with internal nodes of type MergeMem and
822 // memory Phis and stores as (potentially repeated) leaves.
823
824 // We don't optimize the memory graph for pinned loads, so we may need to raise the
825 // root of our search tree through the corresponding slices of MergeMem nodes to
826 // get to the node that really creates the memory state for this slice.
827 if (load_alias_idx >= Compile::AliasIdxRaw) {
828 while (initial_mem->is_MergeMem()) {
829 MergeMemNode* mm = initial_mem->as_MergeMem();
830 Node* p = mm->memory_at(load_alias_idx);
831 if (p != mm->base_memory()) {
832 initial_mem = p;
833 } else {
834 break;
835 }
836 }
837 }
838 // To administer the search, we use a worklist consisting of (def,use)-pairs
839 // of memory states, corresponding to edges in the search tree (and edges
840 // in the memory graph). We need to keep track of search tree edges in the
841 // worklist rather than individual nodes due to memory Phis (see details
842 // below).
843 DefUseMemStatesQueue worklist(area);
844 // We start the search at initial_mem and indicate the search root with the
845 // edge (nullptr, initial_mem).
846 worklist.push(nullptr, initial_mem);
847
848 // The worklist loop
849 while (worklist.is_nonempty()) {
850 // Pop the next edge from the worklist
851 Node* def_mem_state = worklist.top_def();
852 Node* use_mem_state = worklist.top_use();
853 worklist.pop();
854
855 // We are either
856 // - at the root of the search with the edge (nullptr, initial_mem),
857 // - just past initial_mem with the edge (initial_mem, use_mem_state), or
858 // - just past a MergeMem with the edge (MergeMem, use_mem_state).
859 assert(def_mem_state == nullptr || def_mem_state == initial_mem ||
860 def_mem_state->is_MergeMem(),
861 "unexpected memory state");
862
863 const uint op = use_mem_state->Opcode();
864
865 #ifdef ASSERT
866 // CacheWB nodes are peculiar in a sense that they both are anti-dependent and produce memory.
867 // Allow them to be treated as a store.
868 bool is_cache_wb = false;
869 if (use_mem_state->is_Mach()) {
870 int ideal_op = use_mem_state->as_Mach()->ideal_Opcode();
871 is_cache_wb = (ideal_op == Op_CacheWB);
872 }
873 assert(!use_mem_state->needs_anti_dependence_check() || is_cache_wb, "no loads");
874 #endif
875
876 // If we are either at the search root or have found a MergeMem, we step
877 // past use_mem_state and populate the search worklist with edges
878 // (use_mem_state, child) for use_mem_state's children.
879 if (def_mem_state == nullptr // root (exclusive) of tree we are searching
880 || op == Op_MergeMem // internal node of tree we are searching
881 ) {
882 def_mem_state = use_mem_state;
883
884 for (DUIterator_Fast imax, i = def_mem_state->fast_outs(imax); i < imax; i++) {
885 use_mem_state = def_mem_state->fast_out(i);
886 if (use_mem_state->needs_anti_dependence_check()) {
887 // use_mem_state is also a kind of load (i.e.,
888 // needs_anti_dependence_check), and it is not a store nor a memory
889 // Phi. Hence, it is not anti-dependent on the load.
890 continue;
891 }
892 worklist.push(def_mem_state, use_mem_state);
893 }
894 // Nothing more to do for the current (nullptr, initial_mem) or
895 // (initial_mem/MergeMem, MergeMem) edge, move on.
896 continue;
897 }
898
899 assert(!use_mem_state->is_MergeMem(),
900 "use_mem_state should be either a store or a memory Phi");
901
902 if (op == Op_MachProj || op == Op_Catch) continue;
903
904 // Compute the alias index. If the use_mem_state has an alias index
905 // different from the load's, it is not anti-dependent. Wide MemBar's
906 // are anti-dependent with everything (except immutable memories).
907 const TypePtr* adr_type = use_mem_state->adr_type();
908 if (!C->can_alias(adr_type, load_alias_idx)) continue;
909
910 // Most slow-path runtime calls do NOT modify Java memory, but
911 // they can block and so write Raw memory.
912 if (use_mem_state->is_Mach()) {
913 MachNode* muse = use_mem_state->as_Mach();
914 if (load_alias_idx != Compile::AliasIdxRaw) {
915 // Check for call into the runtime using the Java calling
916 // convention (and from there into a wrapper); it has no
917 // _method. Can't do this optimization for Native calls because
918 // they CAN write to Java memory.
919 if (muse->ideal_Opcode() == Op_CallStaticJava) {
920 assert(muse->is_MachSafePoint(), "");
921 MachSafePointNode* ms = (MachSafePointNode*)muse;
922 assert(ms->is_MachCallJava(), "");
923 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
924 if (mcj->_method == nullptr) {
925 // These runtime calls do not write to Java visible memory
926 // (other than Raw) and so are not anti-dependent.
927 continue;
928 }
929 }
930 // Same for SafePoints: they read/write Raw but only read otherwise.
931 // This is basically a workaround for SafePoints only defining control
932 // instead of control + memory.
933 if (muse->ideal_Opcode() == Op_SafePoint) {
934 continue;
935 }
936 } else {
937 // Some raw memory, such as the load of "top" at an allocation,
938 // can be control dependent on the previous safepoint. See
939 // comments in GraphKit::allocate_heap() about control input.
940 // Inserting an anti-dependence edge between such a safepoint and a use
941 // creates a cycle, and will cause a subsequent failure in
942 // local scheduling. (BugId 4919904)
943 // (%%% How can a control input be a safepoint and not a projection??)
944 if (muse->ideal_Opcode() == Op_SafePoint && load->in(0) == muse) {
945 continue;
946 }
947 }
948 }
949
950 // Determine the block of the use_mem_state.
951 Block* use_mem_state_block = get_block_for_node(use_mem_state);
952 assert(use_mem_state_block != nullptr,
953 "unused killing projections skipped above");
954
955 // For efficiency, we take a lazy approach to both raising the LCA and
956 // adding anti-dependence edges. In this worklist loop, we only mark blocks
957 // which we must raise the LCA above (set_raise_LCA_mark), and keep
958 // track of nodes that potentially need anti-dependence edges
959 // (non_early_stores). The only exceptions to this are if we
960 // immediately see that we have to raise the LCA all the way to the early
961 // block, and if we find stores in the early block (which always need
962 // anti-dependence edges).
963 //
964 // After the worklist loop, we perform an efficient combined LCA-raising
965 // operation over all marks and only then add anti-dependence edges where
966 // strictly necessary according to the new raised LCA.
967
968 if (use_mem_state->is_Phi()) {
969 // We have reached a memory Phi node. On our search from initial_mem to
970 // the Phi, we have found no anti-dependences (otherwise, we would have
971 // already terminated the search along this branch). Consider the example
972 // below, indicating a Phi node and its node inputs (we omit the control
973 // input).
974 //
975 // def_mem_state
976 // |
977 // | ? ?
978 // \ | /
979 // Phi
980 //
981 // We reached the Phi from def_mem_state and know that, on this
982 // particular input, the memory that the load must witness is not
983 // overwritten. However, for the Phi's other inputs (? in the
984 // illustration), we have no information and must thus conservatively
985 // assume that the load's memory is overwritten at and below the Phi.
986 //
987 // It is impossible to schedule the load before the Phi in
988 // the same block as the Phi (use_mem_state_block), and anti-dependence
989 // edges are, therefore, redundant. We must, however, find the
990 // predecessor block of use_mem_state_block that corresponds to
991 // def_mem_state, and raise the LCA above that block. Note that this block
992 // is not necessarily def_mem_state's block! See the continuation of our
993 // previous example below (now illustrating blocks instead of nodes)
994 //
995 // def_mem_state's block
996 // |
997 // |
998 // pred_block
999 // |
1000 // | ? ?
1001 // | | |
1002 // use_mem_state_block
1003 //
1004 // Here, we must raise the LCA above pred_block rather than
1005 // def_mem_state's block.
1006 //
1007 // Do not assert(use_mem_state_block != early, "Phi merging memory after access")
1008 // PhiNode may be at start of block 'early' with backedge to 'early'
1009 if (LCA == early) {
1010 // Don't bother if LCA is already raised all the way
1011 continue;
1012 }
1013 DEBUG_ONLY(bool found_match = false);
1014 for (uint j = PhiNode::Input, jmax = use_mem_state->req(); j < jmax; j++) {
1015 if (use_mem_state->in(j) == def_mem_state) { // Found matching input?
1016 DEBUG_ONLY(found_match = true);
1017 Block* pred_block = get_block_for_node(use_mem_state_block->pred(j));
1018 if (pred_block != early) {
1019 // Lazily set the LCA mark
1020 pred_block->set_raise_LCA_mark(load_index);
1021 must_raise_LCA_above_marks = true;
1022 } else /* if (pred_block == early) */ {
1023 // We know already now that we must raise LCA all the way to early.
1024 LCA = early;
1025 // This turns off the process of gathering non_early_stores.
1026 }
1027 }
1028 }
1029 assert(found_match, "no worklist bug");
1030 } else if (use_mem_state_block != early) {
1031 // We found an anti-dependent store outside the load's 'early' block. The
1032 // store may be between the current LCA and the earliest possible block
1033 // (but it could very well also be on a distinct control-flow path).
1034 // Lazily set the LCA mark and push to non_early_stores.
1035 if (LCA == early) {
1036 // Don't bother if LCA is already raised all the way
1037 continue;
1038 }
1039 if (unrelated_load_in_store_null_block(use_mem_state, load)) {
1040 continue;
1041 }
1042 use_mem_state_block->set_raise_LCA_mark(load_index);
1043 must_raise_LCA_above_marks = true;
1044 non_early_stores.push(use_mem_state);
1045 } else /* if (use_mem_state_block == early) */ {
1046 // We found an anti-dependent store in the load's 'early' block.
1047 // Therefore, we know already now that we must raise LCA all the way to
1048 // early and that we need to add an anti-dependence edge to the store.
1049 assert(use_mem_state != load->find_exact_control(load->in(0)), "dependence cycle found");
1050 if (verify) {
1051 assert(use_mem_state->find_edge(load) != -1 || unrelated_load_in_store_null_block(use_mem_state, load),
1052 "missing precedence edge");
1053 } else {
1054 use_mem_state->add_prec(load);
1055 }
1056 LCA = early;
1057 // This turns off the process of gathering non_early_stores.
1058 }
1059 }
1060 // Worklist is now empty; we have visited all possible anti-dependences.
1061
1062 // Finished if 'load' must be scheduled in its 'early' block.
1063 // If we found any stores there, they have already been given
1064 // anti-dependence edges.
1065 if (LCA == early) {
1066 return LCA;
1067 }
1068
1069 // We get here only if there are no anti-dependent stores in the load's
1070 // 'early' block and if no memory Phi has forced LCA to the early block. Now
1071 // we must raise the LCA above the blocks for all the anti-dependent stores
1072 // and above the predecessor blocks of anti-dependent memory Phis we reached
1073 // during the search.
1074 if (must_raise_LCA_above_marks) {
1075 LCA = raise_LCA_above_marks(LCA, load->_idx, early, this);
1076 }
1077
1078 // If LCA == early at this point, there were no stores that required
1079 // anti-dependence edges in the early block. Otherwise, we would have eagerly
1080 // raised the LCA to early already in the worklist loop.
1081 if (LCA == early) {
1082 return LCA;
1083 }
1084
1085 // The raised LCA block can now be a home to anti-dependent stores for which
1086 // we still need to add anti-dependence edges, but no LCA predecessor block
1087 // contains any such stores (otherwise, we would have raised the LCA even
1088 // higher).
1089 //
1090 // The raised LCA will be a lower bound for placing the load, preventing the
1091 // load from sinking past any block containing a store that may overwrite
1092 // memory that the load must witness.
1093 //
1094 // Now we need to insert the necessary anti-dependence edges from 'load' to
1095 // each store in the non-early LCA block. We have recorded all such potential
1096 // stores in non_early_stores.
1097 //
1098 // If LCA->raise_LCA_mark() != load_index, it means that we raised the LCA to
1099 // a block in which we did not find any anti-dependent stores. So, no need to
1100 // search for any such stores.
1101 if (LCA->raise_LCA_mark() == load_index) {
1102 while (non_early_stores.size() > 0) {
1103 Node* store = non_early_stores.pop();
1104 Block* store_block = get_block_for_node(store);
1105 if (store_block == LCA) {
1106 // Add anti-dependence edge from the load to the store in the non-early
1107 // LCA.
1108 assert(store != load->find_exact_control(load->in(0)), "dependence cycle found");
1109 if (verify) {
1110 assert(store->find_edge(load) != -1, "missing precedence edge");
1111 } else {
1112 store->add_prec(load);
1113 }
1114 } else {
1115 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
1116 }
1117 }
1118 }
1119
1120 assert(LCA->dominates(LCA_orig), "unsound updated LCA");
1121
1122 // Return the highest block containing stores; any stores
1123 // within that block have been given anti-dependence edges.
1124 return LCA;
1125 }
1126
1127 // This class is used to iterate backwards over the nodes in the graph.
1128
1129 class Node_Backward_Iterator {
1130
1131 private:
1132 Node_Backward_Iterator();
1133
1134 public:
1135 // Constructor for the iterator
1136 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg);
1137
1138 // Postincrement operator to iterate over the nodes
1139 Node *next();
1140
1141 private:
1142 VectorSet &_visited;
1143 Node_Stack &_stack;
1144 PhaseCFG &_cfg;
1145 };
1146
1147 // Constructor for the Node_Backward_Iterator
1148 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg)
1149 : _visited(visited), _stack(stack), _cfg(cfg) {
1150 // The stack should contain exactly the root
1151 stack.clear();
1152 stack.push(root, root->outcnt());
1153
1154 // Clear the visited bits
1155 visited.clear();
1156 }
1157
1158 // Iterator for the Node_Backward_Iterator
1159 Node *Node_Backward_Iterator::next() {
1160
1161 // If the _stack is empty, then just return null: finished.
1162 if ( !_stack.size() )
1163 return nullptr;
1164
1165 // I visit unvisited not-anti-dependence users first, then anti-dependent
1166 // children next. I iterate backwards to support removal of nodes.
1167 // The stack holds states consisting of 3 values:
1168 // current Def node, flag which indicates 1st/2nd pass, index of current out edge
1169 Node *self = (Node*)(((uintptr_t)_stack.node()) & ~1);
1170 bool iterate_anti_dep = (((uintptr_t)_stack.node()) & 1);
1171 uint idx = MIN2(_stack.index(), self->outcnt()); // Support removal of nodes.
1172 _stack.pop();
1173
1174 // I cycle here when I am entering a deeper level of recursion.
1175 // The key variable 'self' was set prior to jumping here.
1176 while( 1 ) {
1177
1178 _visited.set(self->_idx);
1179
1180 // Now schedule all uses as late as possible.
1181 const Node* src = self->is_Proj() ? self->in(0) : self;
1182 uint src_rpo = _cfg.get_block_for_node(src)->_rpo;
1183
1184 // Schedule all nodes in a post-order visit
1185 Node *unvisited = nullptr; // Unvisited anti-dependent Node, if any
1186
1187 // Scan for unvisited nodes
1188 while (idx > 0) {
1189 // For all uses, schedule late
1190 Node* n = self->raw_out(--idx); // Use
1191
1192 // Skip already visited children
1193 if ( _visited.test(n->_idx) )
1194 continue;
1195
1196 // do not traverse backward control edges
1197 Node *use = n->is_Proj() ? n->in(0) : n;
1198 uint use_rpo = _cfg.get_block_for_node(use)->_rpo;
1199
1200 if ( use_rpo < src_rpo )
1201 continue;
1202
1203 // Phi nodes always precede uses in a basic block
1204 if ( use_rpo == src_rpo && use->is_Phi() )
1205 continue;
1206
1207 unvisited = n; // Found unvisited
1208
1209 // Check for possible-anti-dependent
1210 // 1st pass: No such nodes, 2nd pass: Only such nodes.
1211 if (n->needs_anti_dependence_check() == iterate_anti_dep) {
1212 unvisited = n; // Found unvisited
1213 break;
1214 }
1215 }
1216
1217 // Did I find an unvisited not-anti-dependent Node?
1218 if (!unvisited) {
1219 if (!iterate_anti_dep) {
1220 // 2nd pass: Iterate over nodes which needs_anti_dependence_check.
1221 iterate_anti_dep = true;
1222 idx = self->outcnt();
1223 continue;
1224 }
1225 break; // All done with children; post-visit 'self'
1226 }
1227
1228 // Visit the unvisited Node. Contains the obvious push to
1229 // indicate I'm entering a deeper level of recursion. I push the
1230 // old state onto the _stack and set a new state and loop (recurse).
1231 _stack.push((Node*)((uintptr_t)self | (uintptr_t)iterate_anti_dep), idx);
1232 self = unvisited;
1233 iterate_anti_dep = false;
1234 idx = self->outcnt();
1235 } // End recursion loop
1236
1237 return self;
1238 }
1239
1240 //------------------------------ComputeLatenciesBackwards----------------------
1241 // Compute the latency of all the instructions.
1242 void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_Stack &stack) {
1243 #ifndef PRODUCT
1244 if (trace_opto_pipelining())
1245 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
1246 #endif
1247
1248 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1249 Node *n;
1250
1251 // Walk over all the nodes from last to first
1252 while ((n = iter.next())) {
1253 // Set the latency for the definitions of this instruction
1254 partial_latency_of_defs(n);
1255 }
1256 } // end ComputeLatenciesBackwards
1257
1258 //------------------------------partial_latency_of_defs------------------------
1259 // Compute the latency impact of this node on all defs. This computes
1260 // a number that increases as we approach the beginning of the routine.
1261 void PhaseCFG::partial_latency_of_defs(Node *n) {
1262 // Set the latency for this instruction
1263 #ifndef PRODUCT
1264 if (trace_opto_pipelining()) {
1265 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1266 dump();
1267 }
1268 #endif
1269
1270 if (n->is_Proj()) {
1271 n = n->in(0);
1272 }
1273
1274 if (n->is_Root()) {
1275 return;
1276 }
1277
1278 uint nlen = n->len();
1279 uint use_latency = get_latency_for_node(n);
1280 uint use_pre_order = get_block_for_node(n)->_pre_order;
1281
1282 for (uint j = 0; j < nlen; j++) {
1283 Node *def = n->in(j);
1284
1285 if (!def || def == n) {
1286 continue;
1287 }
1288
1289 // Walk backwards thru projections
1290 if (def->is_Proj()) {
1291 def = def->in(0);
1292 }
1293
1294 #ifndef PRODUCT
1295 if (trace_opto_pipelining()) {
1296 tty->print("# in(%2d): ", j);
1297 def->dump();
1298 }
1299 #endif
1300
1301 // If the defining block is not known, assume it is ok
1302 Block *def_block = get_block_for_node(def);
1303 uint def_pre_order = def_block ? def_block->_pre_order : 0;
1304
1305 if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) {
1306 continue;
1307 }
1308
1309 uint delta_latency = n->latency(j);
1310 uint current_latency = delta_latency + use_latency;
1311
1312 if (get_latency_for_node(def) < current_latency) {
1313 set_latency_for_node(def, current_latency);
1314 }
1315
1316 #ifndef PRODUCT
1317 if (trace_opto_pipelining()) {
1318 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, node_latency[%d] = %d", use_latency, j, delta_latency, current_latency, def->_idx, get_latency_for_node(def));
1319 }
1320 #endif
1321 }
1322 }
1323
1324 //------------------------------latency_from_use-------------------------------
1325 // Compute the latency of a specific use
1326 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
1327 // If self-reference, return no latency
1328 if (use == n || use->is_Root()) {
1329 return 0;
1330 }
1331
1332 uint def_pre_order = get_block_for_node(def)->_pre_order;
1333 uint latency = 0;
1334
1335 // If the use is not a projection, then it is simple...
1336 if (!use->is_Proj()) {
1337 #ifndef PRODUCT
1338 if (trace_opto_pipelining()) {
1339 tty->print("# out(): ");
1340 use->dump();
1341 }
1342 #endif
1343
1344 uint use_pre_order = get_block_for_node(use)->_pre_order;
1345
1346 if (use_pre_order < def_pre_order)
1347 return 0;
1348
1349 if (use_pre_order == def_pre_order && use->is_Phi())
1350 return 0;
1351
1352 uint nlen = use->len();
1353 uint nl = get_latency_for_node(use);
1354
1355 for ( uint j=0; j<nlen; j++ ) {
1356 if (use->in(j) == n) {
1357 // Change this if we want local latencies
1358 uint ul = use->latency(j);
1359 uint l = ul + nl;
1360 if (latency < l) latency = l;
1361 #ifndef PRODUCT
1362 if (trace_opto_pipelining()) {
1363 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
1364 nl, j, ul, l, latency);
1365 }
1366 #endif
1367 }
1368 }
1369 } else {
1370 // This is a projection, just grab the latency of the use(s)
1371 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
1372 uint l = latency_from_use(use, def, use->fast_out(j));
1373 if (latency < l) latency = l;
1374 }
1375 }
1376
1377 return latency;
1378 }
1379
1380 //------------------------------latency_from_uses------------------------------
1381 // Compute the latency of this instruction relative to all of it's uses.
1382 // This computes a number that increases as we approach the beginning of the
1383 // routine.
1384 void PhaseCFG::latency_from_uses(Node *n) {
1385 // Set the latency for this instruction
1386 #ifndef PRODUCT
1387 if (trace_opto_pipelining()) {
1388 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1389 dump();
1390 }
1391 #endif
1392 uint latency=0;
1393 const Node *def = n->is_Proj() ? n->in(0): n;
1394
1395 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1396 uint l = latency_from_use(n, def, n->fast_out(i));
1397
1398 if (latency < l) latency = l;
1399 }
1400
1401 set_latency_for_node(n, latency);
1402 }
1403
1404 //------------------------------is_cheaper_block-------------------------
1405 // Check if a block between early and LCA block of uses is cheaper by
1406 // frequency-based policy, latency-based policy and random-based policy
1407 bool PhaseCFG::is_cheaper_block(Block* LCA, Node* self, uint target_latency,
1408 uint end_latency, double least_freq,
1409 int cand_cnt, bool in_latency) {
1410 if (StressGCM) {
1411 // Should be randomly accepted in stress mode
1412 return C->randomized_select(cand_cnt);
1413 }
1414
1415 const double delta = 1 + PROB_UNLIKELY_MAG(4);
1416
1417 // Better Frequency. Add a small delta to the comparison to not needlessly
1418 // hoist because of, e.g., small numerical inaccuracies.
1419 if (LCA->_freq * delta < least_freq) {
1420 return true;
1421 }
1422
1423 // Otherwise, choose with latency
1424 if (!in_latency && // No block containing latency
1425 LCA->_freq < least_freq * delta && // No worse frequency
1426 target_latency >= end_latency && // within latency range
1427 !self->is_iteratively_computed() // But don't hoist IV increments
1428 // because they may end up above other uses of their phi forcing
1429 // their result register to be different from their input.
1430 ) {
1431 return true;
1432 }
1433
1434 return false;
1435 }
1436
1437 //------------------------------hoist_to_cheaper_block-------------------------
1438 // Pick a block for node self, between early and LCA block of uses, that is a
1439 // cheaper alternative to LCA.
1440 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1441 Block* least = LCA;
1442 double least_freq = least->_freq;
1443 uint target = get_latency_for_node(self);
1444 uint start_latency = get_latency_for_node(LCA->head());
1445 uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx()));
1446 bool in_latency = (target <= start_latency);
1447 const Block* root_block = get_block_for_node(_root);
1448
1449 // Turn off latency scheduling if scheduling is just plain off
1450 if (!C->do_scheduling())
1451 in_latency = true;
1452
1453 // Do not hoist (to cover latency) instructions which target a
1454 // single register. Hoisting stretches the live range of the
1455 // single register and may force spilling.
1456 MachNode* mach = self->is_Mach() ? self->as_Mach() : nullptr;
1457 if (mach != nullptr && mach->out_RegMask().is_bound1() && !mach->out_RegMask().is_empty()) {
1458 in_latency = true;
1459 }
1460
1461 #ifndef PRODUCT
1462 if (trace_opto_pipelining()) {
1463 tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self));
1464 self->dump();
1465 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1466 LCA->_pre_order,
1467 LCA->head()->_idx,
1468 start_latency,
1469 LCA->get_node(LCA->end_idx())->_idx,
1470 end_latency,
1471 least_freq);
1472 }
1473 #endif
1474
1475 int cand_cnt = 0; // number of candidates tried
1476
1477 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1478 // the earliest legal location. Capture the least execution frequency,
1479 // or choose a random block if -XX:+StressGCM, or using latency-based policy
1480 while (LCA != early) {
1481 LCA = LCA->_idom; // Follow up the dominator tree
1482
1483 if (LCA == nullptr) {
1484 // Bailout without retry
1485 assert(false, "graph should be schedulable");
1486 C->record_method_not_compilable("late schedule failed: LCA is null");
1487 return least;
1488 }
1489
1490 // Don't hoist machine instructions to the root basic block
1491 if (mach != nullptr && LCA == root_block)
1492 break;
1493
1494 if (self->is_memory_writer() &&
1495 (LCA->_loop->depth() > early->_loop->depth())) {
1496 // LCA is an invalid placement for a memory writer: choosing it would
1497 // cause memory interference, as illustrated in schedule_late().
1498 continue;
1499 }
1500 verify_memory_writer_placement(LCA, self);
1501
1502 uint start_lat = get_latency_for_node(LCA->head());
1503 uint end_idx = LCA->end_idx();
1504 uint end_lat = get_latency_for_node(LCA->get_node(end_idx));
1505 double LCA_freq = LCA->_freq;
1506 #ifndef PRODUCT
1507 if (trace_opto_pipelining()) {
1508 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1509 LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq);
1510 }
1511 #endif
1512 cand_cnt++;
1513 if (is_cheaper_block(LCA, self, target, end_lat, least_freq, cand_cnt, in_latency)) {
1514 least = LCA; // Found cheaper block
1515 least_freq = LCA_freq;
1516 start_latency = start_lat;
1517 end_latency = end_lat;
1518 if (target <= start_lat)
1519 in_latency = true;
1520 }
1521 }
1522
1523 #ifndef PRODUCT
1524 if (trace_opto_pipelining()) {
1525 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1526 least->_pre_order, start_latency, least_freq);
1527 }
1528 #endif
1529
1530 // See if the latency needs to be updated
1531 if (target < end_latency) {
1532 #ifndef PRODUCT
1533 if (trace_opto_pipelining()) {
1534 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1535 }
1536 #endif
1537 set_latency_for_node(self, end_latency);
1538 partial_latency_of_defs(self);
1539 }
1540
1541 return least;
1542 }
1543
1544
1545 //------------------------------schedule_late-----------------------------------
1546 // Now schedule all codes as LATE as possible. This is the LCA in the
1547 // dominator tree of all USES of a value. Pick the block with the least
1548 // loop nesting depth that is lowest in the dominator tree.
1549 extern const char must_clone[];
1550 void PhaseCFG::schedule_late(VectorSet &visited, Node_Stack &stack) {
1551 #ifndef PRODUCT
1552 if (trace_opto_pipelining())
1553 tty->print("\n#---- schedule_late ----\n");
1554 #endif
1555
1556 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1557 Node *self;
1558
1559 // Walk over all the nodes from last to first
1560 while ((self = iter.next())) {
1561 Block* early = get_block_for_node(self); // Earliest legal placement
1562
1563 if (self->is_top()) {
1564 // Top node goes in bb #2 with other constants.
1565 // It must be special-cased, because it has no out edges.
1566 early->add_inst(self);
1567 continue;
1568 }
1569
1570 // No uses, just terminate
1571 if (self->outcnt() == 0) {
1572 assert(self->is_MachProj(), "sanity");
1573 continue; // Must be a dead machine projection
1574 }
1575
1576 // If node is pinned in the block, then no scheduling can be done.
1577 if( self->pinned() ) // Pinned in block?
1578 continue;
1579
1580 #ifdef ASSERT
1581 // Assert that memory writers (e.g. stores) have a "home" block (the block
1582 // given by their control input), and that this block corresponds to their
1583 // earliest possible placement. This guarantees that
1584 // hoist_to_cheaper_block() will always have at least one valid choice.
1585 if (self->is_memory_writer()) {
1586 assert(find_block_for_node(self->in(0)) == early,
1587 "The home of a memory writer must also be its earliest placement");
1588 }
1589 #endif
1590
1591 MachNode* mach = self->is_Mach() ? self->as_Mach() : nullptr;
1592 if (mach) {
1593 switch (mach->ideal_Opcode()) {
1594 case Op_CreateEx:
1595 // Don't move exception creation
1596 early->add_inst(self);
1597 continue;
1598 break;
1599 case Op_CastI2N:
1600 early->add_inst(self);
1601 continue;
1602 case Op_CheckCastPP: {
1603 // Don't move CheckCastPP nodes away from their input, if the input
1604 // is a rawptr (5071820).
1605 Node *def = self->in(1);
1606 if (def != nullptr && def->bottom_type()->base() == Type::RawPtr) {
1607 early->add_inst(self);
1608 #ifdef ASSERT
1609 _raw_oops.push(def);
1610 #endif
1611 continue;
1612 }
1613 break;
1614 }
1615 default:
1616 break;
1617 }
1618 if (C->has_irreducible_loop() && self->is_memory_writer()) {
1619 // If the CFG is irreducible, place memory writers in their home block.
1620 // This prevents hoist_to_cheaper_block() from accidentally placing such
1621 // nodes into deeper loops, as in the following example:
1622 //
1623 // Home placement of store in B1 (loop L1):
1624 //
1625 // B1 (L1):
1626 // m1 <- ..
1627 // m2 <- store m1, ..
1628 // B2 (L2):
1629 // jump B2
1630 // B3 (L1):
1631 // .. <- .. m2, ..
1632 //
1633 // Wrong "hoisting" of store to B2 (in loop L2, child of L1):
1634 //
1635 // B1 (L1):
1636 // m1 <- ..
1637 // B2 (L2):
1638 // m2 <- store m1, ..
1639 // # Wrong: m1 and m2 interfere at this point.
1640 // jump B2
1641 // B3 (L1):
1642 // .. <- .. m2, ..
1643 //
1644 // This "hoist inversion" can happen due to different factors such as
1645 // inaccurate estimation of frequencies for irreducible CFGs, and loops
1646 // with always-taken exits in reducible CFGs. In the reducible case,
1647 // hoist inversion is prevented by discarding invalid blocks (those in
1648 // deeper loops than the home block). In the irreducible case, the
1649 // invalid blocks cannot be identified due to incomplete loop nesting
1650 // information, hence a conservative solution is taken.
1651 #ifndef PRODUCT
1652 if (trace_opto_pipelining()) {
1653 tty->print_cr("# Irreducible loops: schedule in home block B%d:",
1654 early->_pre_order);
1655 self->dump();
1656 }
1657 #endif
1658 schedule_node_into_block(self, early);
1659 continue;
1660 }
1661 }
1662
1663 // Gather LCA of all uses
1664 Block *LCA = nullptr;
1665 {
1666 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1667 // For all uses, find LCA
1668 Node* use = self->fast_out(i);
1669 LCA = raise_LCA_above_use(LCA, use, self, this);
1670 }
1671 guarantee(LCA != nullptr, "There must be a LCA");
1672 } // (Hide defs of imax, i from rest of block.)
1673
1674 // Place temps in the block of their use. This isn't a
1675 // requirement for correctness but it reduces useless
1676 // interference between temps and other nodes.
1677 if (mach != nullptr && mach->is_MachTemp()) {
1678 map_node_to_block(self, LCA);
1679 LCA->add_inst(self);
1680 continue;
1681 }
1682
1683 // Check if 'self' could be anti-dependent on memory
1684 if (self->needs_anti_dependence_check()) {
1685 // Hoist LCA above possible-defs and insert anti-dependences to
1686 // defs in new LCA block.
1687 LCA = raise_above_anti_dependences(LCA, self);
1688 if (C->failing()) {
1689 return;
1690 }
1691 }
1692
1693 if (early->_dom_depth > LCA->_dom_depth) {
1694 // Somehow the LCA has moved above the earliest legal point.
1695 // (One way this can happen is via memory_early_block.)
1696 if (C->subsume_loads() == true && !C->failing()) {
1697 // Retry with subsume_loads == false
1698 // If this is the first failure, the sentinel string will "stick"
1699 // to the Compile object, and the C2Compiler will see it and retry.
1700 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1701 } else {
1702 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1703 assert(C->failure_is_artificial(), "graph should be schedulable");
1704 C->record_method_not_compilable("late schedule failed: incorrect graph" DEBUG_ONLY(COMMA true));
1705 }
1706 return;
1707 }
1708
1709 if (self->is_memory_writer()) {
1710 // If the LCA of a memory writer is a descendant of its home loop, hoist
1711 // it into a valid placement.
1712 while (LCA->_loop->depth() > early->_loop->depth()) {
1713 LCA = LCA->_idom;
1714 }
1715 assert(LCA != nullptr, "a valid LCA must exist");
1716 verify_memory_writer_placement(LCA, self);
1717 }
1718
1719 // If there is no opportunity to hoist, then we're done.
1720 // In stress mode, try to hoist even the single operations.
1721 bool try_to_hoist = StressGCM || (LCA != early);
1722
1723 // Must clone guys stay next to use; no hoisting allowed.
1724 // Also cannot hoist guys that alter memory or are otherwise not
1725 // allocatable (hoisting can make a value live longer, leading to
1726 // anti and output dependency problems which are normally resolved
1727 // by the register allocator giving everyone a different register).
1728 if (mach != nullptr && must_clone[mach->ideal_Opcode()])
1729 try_to_hoist = false;
1730
1731 Block* late = nullptr;
1732 if (try_to_hoist) {
1733 // Now find the block with the least execution frequency.
1734 // Start at the latest schedule and work up to the earliest schedule
1735 // in the dominator tree. Thus the Node will dominate all its uses.
1736 late = hoist_to_cheaper_block(LCA, early, self);
1737 } else {
1738 // Just use the LCA of the uses.
1739 late = LCA;
1740 }
1741
1742 // Put the node into target block
1743 schedule_node_into_block(self, late);
1744
1745 #ifdef ASSERT
1746 if (self->needs_anti_dependence_check()) {
1747 // since precedence edges are only inserted when we're sure they
1748 // are needed make sure that after placement in a block we don't
1749 // need any new precedence edges.
1750 verify_anti_dependences(late, self);
1751 if (C->failing()) {
1752 return;
1753 }
1754 }
1755 #endif
1756 } // Loop until all nodes have been visited
1757
1758 } // end ScheduleLate
1759
1760 //------------------------------GlobalCodeMotion-------------------------------
1761 void PhaseCFG::global_code_motion() {
1762 ResourceMark rm;
1763
1764 #ifndef PRODUCT
1765 if (trace_opto_pipelining()) {
1766 tty->print("\n---- Start GlobalCodeMotion ----\n");
1767 }
1768 #endif
1769
1770 // Initialize the node to block mapping for things on the proj_list
1771 for (uint i = 0; i < _matcher.number_of_projections(); i++) {
1772 unmap_node_from_block(_matcher.get_projection(i));
1773 }
1774
1775 // Set the basic block for Nodes pinned into blocks
1776 VectorSet visited;
1777 schedule_pinned_nodes(visited);
1778
1779 // Find the earliest Block any instruction can be placed in. Some
1780 // instructions are pinned into Blocks. Unpinned instructions can
1781 // appear in last block in which all their inputs occur.
1782 visited.clear();
1783 Node_Stack stack((C->live_nodes() >> 2) + 16); // pre-grow
1784 if (!schedule_early(visited, stack)) {
1785 // Bailout without retry
1786 assert(C->failure_is_artificial(), "early schedule failed");
1787 C->record_method_not_compilable("early schedule failed" DEBUG_ONLY(COMMA true));
1788 return;
1789 }
1790
1791 // Build Def-Use edges.
1792 // Compute the latency information (via backwards walk) for all the
1793 // instructions in the graph
1794 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1795
1796 if (C->do_scheduling()) {
1797 compute_latencies_backwards(visited, stack);
1798 }
1799
1800 // Now schedule all codes as LATE as possible. This is the LCA in the
1801 // dominator tree of all USES of a value. Pick the block with the least
1802 // loop nesting depth that is lowest in the dominator tree.
1803 // ( visited.clear() called in schedule_late()->Node_Backward_Iterator() )
1804 schedule_late(visited, stack);
1805 if (C->failing()) {
1806 return;
1807 }
1808
1809 #ifndef PRODUCT
1810 if (trace_opto_pipelining()) {
1811 tty->print("\n---- Detect implicit null checks ----\n");
1812 }
1813 #endif
1814
1815 // Detect implicit-null-check opportunities. Basically, find null checks
1816 // with suitable memory ops nearby. Use the memory op to do the null check.
1817 // I can generate a memory op if there is not one nearby.
1818 if (C->is_method_compilation()) {
1819 // By reversing the loop direction we get a very minor gain on mpegaudio.
1820 // Feel free to revert to a forward loop for clarity.
1821 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1822 for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) {
1823 Node* proj = _matcher._null_check_tests[i];
1824 Node* val = _matcher._null_check_tests[i + 1];
1825 Block* block = get_block_for_node(proj);
1826 implicit_null_check(block, proj, val, C->allowed_deopt_reasons());
1827 // The implicit_null_check will only perform the transformation
1828 // if the null branch is truly uncommon, *and* it leads to an
1829 // uncommon trap. Combined with the too_many_traps guards
1830 // above, this prevents SEGV storms reported in 6366351,
1831 // by recompiling offending methods without this optimization.
1832 if (C->failing()) {
1833 return;
1834 }
1835 }
1836 }
1837
1838 bool block_size_threshold_ok = false;
1839 intptr_t *recalc_pressure_nodes = nullptr;
1840 if (OptoRegScheduling) {
1841 for (uint i = 0; i < number_of_blocks(); i++) {
1842 Block* block = get_block(i);
1843 if (block->number_of_nodes() > 10) {
1844 block_size_threshold_ok = true;
1845 break;
1846 }
1847 }
1848 }
1849
1850 // Enabling the scheduler for register pressure plus finding blocks of size to schedule for it
1851 // is key to enabling this feature.
1852 PhaseChaitin regalloc(C->unique(), *this, _matcher, true);
1853 ResourceArea live_arena(mtCompiler, Arena::Tag::tag_reglive); // Arena for liveness
1854 ResourceMark rm_live(&live_arena);
1855 PhaseLive live(*this, regalloc._lrg_map.names(), &live_arena, true);
1856 PhaseIFG ifg(&live_arena);
1857 if (OptoRegScheduling && block_size_threshold_ok) {
1858 regalloc.mark_ssa();
1859 Compile::TracePhase tp(_t_computeLive);
1860 rm_live.reset_to_mark(); // Reclaim working storage
1861 IndexSet::reset_memory(C, &live_arena);
1862 uint node_size = regalloc._lrg_map.max_lrg_id();
1863 ifg.init(node_size); // Empty IFG
1864 regalloc.set_ifg(ifg);
1865 regalloc.set_live(live);
1866 regalloc.gather_lrg_masks(false); // Collect LRG masks
1867 live.compute(node_size); // Compute liveness
1868
1869 recalc_pressure_nodes = NEW_RESOURCE_ARRAY(intptr_t, node_size);
1870 for (uint i = 0; i < node_size; i++) {
1871 recalc_pressure_nodes[i] = 0;
1872 }
1873 }
1874 _regalloc = ®alloc;
1875
1876 #ifndef PRODUCT
1877 if (trace_opto_pipelining()) {
1878 tty->print("\n---- Start Local Scheduling ----\n");
1879 }
1880 #endif
1881
1882 // Schedule locally. Right now a simple topological sort.
1883 // Later, do a real latency aware scheduler.
1884 GrowableArray<int> ready_cnt(C->unique(), C->unique(), -1);
1885 visited.reset();
1886 for (uint i = 0; i < number_of_blocks(); i++) {
1887 Block* block = get_block(i);
1888 if (!schedule_local(block, ready_cnt, visited, recalc_pressure_nodes)) {
1889 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1890 assert(C->failure_is_artificial(), "local schedule failed");
1891 C->record_method_not_compilable("local schedule failed" DEBUG_ONLY(COMMA true));
1892 }
1893 _regalloc = nullptr;
1894 return;
1895 }
1896 }
1897 _regalloc = nullptr;
1898
1899 // If we inserted any instructions between a Call and his CatchNode,
1900 // clone the instructions on all paths below the Catch.
1901 for (uint i = 0; i < number_of_blocks(); i++) {
1902 Block* block = get_block(i);
1903 call_catch_cleanup(block);
1904 if (C->failing()) {
1905 return;
1906 }
1907 }
1908
1909 #ifndef PRODUCT
1910 if (trace_opto_pipelining()) {
1911 tty->print("\n---- After GlobalCodeMotion ----\n");
1912 for (uint i = 0; i < number_of_blocks(); i++) {
1913 Block* block = get_block(i);
1914 block->dump();
1915 }
1916 }
1917 #endif
1918 // Dead.
1919 _node_latency = (GrowableArray<uint> *)((intptr_t)0xdeadbeef);
1920 }
1921
1922 bool PhaseCFG::do_global_code_motion() {
1923
1924 build_dominator_tree();
1925 if (C->failing()) {
1926 return false;
1927 }
1928
1929 NOT_PRODUCT( C->verify_graph_edges(); )
1930
1931 estimate_block_frequency();
1932
1933 global_code_motion();
1934
1935 if (C->failing()) {
1936 return false;
1937 }
1938
1939 return true;
1940 }
1941
1942 //------------------------------Estimate_Block_Frequency-----------------------
1943 // Estimate block frequencies based on IfNode probabilities.
1944 void PhaseCFG::estimate_block_frequency() {
1945
1946 // Force conditional branches leading to uncommon traps to be unlikely,
1947 // not because we get to the uncommon_trap with less relative frequency,
1948 // but because an uncommon_trap typically causes a deopt, so we only get
1949 // there once.
1950 if (C->do_freq_based_layout()) {
1951 Block_List worklist;
1952 Block* root_blk = get_block(0);
1953 for (uint i = 1; i < root_blk->num_preds(); i++) {
1954 Block *pb = get_block_for_node(root_blk->pred(i));
1955 if (pb->has_uncommon_code()) {
1956 worklist.push(pb);
1957 }
1958 }
1959 while (worklist.size() > 0) {
1960 Block* uct = worklist.pop();
1961 if (uct == get_root_block()) {
1962 continue;
1963 }
1964 for (uint i = 1; i < uct->num_preds(); i++) {
1965 Block *pb = get_block_for_node(uct->pred(i));
1966 if (pb->_num_succs == 1) {
1967 worklist.push(pb);
1968 } else if (pb->num_fall_throughs() == 2) {
1969 pb->update_uncommon_branch(uct);
1970 }
1971 }
1972 }
1973 }
1974
1975 // Create the loop tree and calculate loop depth.
1976 _root_loop = create_loop_tree();
1977 _root_loop->compute_loop_depth(0);
1978
1979 // Compute block frequency of each block, relative to a single loop entry.
1980 _root_loop->compute_freq();
1981
1982 // Adjust all frequencies to be relative to a single method entry
1983 _root_loop->_freq = 1.0;
1984 _root_loop->scale_freq();
1985
1986 // Save outmost loop frequency for LRG frequency threshold
1987 _outer_loop_frequency = _root_loop->outer_loop_freq();
1988
1989 // force paths ending at uncommon traps to be infrequent
1990 if (!C->do_freq_based_layout()) {
1991 Block_List worklist;
1992 Block* root_blk = get_block(0);
1993 for (uint i = 1; i < root_blk->num_preds(); i++) {
1994 Block *pb = get_block_for_node(root_blk->pred(i));
1995 if (pb->has_uncommon_code()) {
1996 worklist.push(pb);
1997 }
1998 }
1999 while (worklist.size() > 0) {
2000 Block* uct = worklist.pop();
2001 uct->_freq = PROB_MIN;
2002 for (uint i = 1; i < uct->num_preds(); i++) {
2003 Block *pb = get_block_for_node(uct->pred(i));
2004 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
2005 worklist.push(pb);
2006 }
2007 }
2008 }
2009 }
2010
2011 #ifdef ASSERT
2012 for (uint i = 0; i < number_of_blocks(); i++) {
2013 Block* b = get_block(i);
2014 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
2015 }
2016 #endif
2017
2018 #ifndef PRODUCT
2019 if (PrintCFGBlockFreq) {
2020 tty->print_cr("CFG Block Frequencies");
2021 _root_loop->dump_tree();
2022 if (Verbose) {
2023 tty->print_cr("PhaseCFG dump");
2024 dump();
2025 tty->print_cr("Node dump");
2026 _root->dump(99999);
2027 }
2028 }
2029 #endif
2030 }
2031
2032 //----------------------------create_loop_tree--------------------------------
2033 // Create a loop tree from the CFG
2034 CFGLoop* PhaseCFG::create_loop_tree() {
2035
2036 #ifdef ASSERT
2037 assert(get_block(0) == get_root_block(), "first block should be root block");
2038 for (uint i = 0; i < number_of_blocks(); i++) {
2039 Block* block = get_block(i);
2040 // Check that _loop field are clear...we could clear them if not.
2041 assert(block->_loop == nullptr, "clear _loop expected");
2042 // Sanity check that the RPO numbering is reflected in the _blocks array.
2043 // It doesn't have to be for the loop tree to be built, but if it is not,
2044 // then the blocks have been reordered since dom graph building...which
2045 // may question the RPO numbering
2046 assert(block->_rpo == i, "unexpected reverse post order number");
2047 }
2048 #endif
2049
2050 int idct = 0;
2051 CFGLoop* root_loop = new CFGLoop(idct++);
2052
2053 Block_List worklist;
2054
2055 // Assign blocks to loops
2056 for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block
2057 Block* block = get_block(i);
2058
2059 if (block->head()->is_Loop()) {
2060 Block* loop_head = block;
2061 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
2062 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
2063 Block* tail = get_block_for_node(tail_n);
2064
2065 // Defensively filter out Loop nodes for non-single-entry loops.
2066 // For all reasonable loops, the head occurs before the tail in RPO.
2067 if (i <= tail->_rpo) {
2068
2069 // The tail and (recursive) predecessors of the tail
2070 // are made members of a new loop.
2071
2072 assert(worklist.size() == 0, "nonempty worklist");
2073 CFGLoop* nloop = new CFGLoop(idct++);
2074 assert(loop_head->_loop == nullptr, "just checking");
2075 loop_head->_loop = nloop;
2076 // Add to nloop so push_pred() will skip over inner loops
2077 nloop->add_member(loop_head);
2078 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this);
2079
2080 while (worklist.size() > 0) {
2081 Block* member = worklist.pop();
2082 if (member != loop_head) {
2083 for (uint j = 1; j < member->num_preds(); j++) {
2084 nloop->push_pred(member, j, worklist, this);
2085 }
2086 }
2087 }
2088 }
2089 }
2090 }
2091
2092 // Create a member list for each loop consisting
2093 // of both blocks and (immediate child) loops.
2094 for (uint i = 0; i < number_of_blocks(); i++) {
2095 Block* block = get_block(i);
2096 CFGLoop* lp = block->_loop;
2097 if (lp == nullptr) {
2098 // Not assigned to a loop. Add it to the method's pseudo loop.
2099 block->_loop = root_loop;
2100 lp = root_loop;
2101 }
2102 if (lp == root_loop || block != lp->head()) { // loop heads are already members
2103 lp->add_member(block);
2104 }
2105 if (lp != root_loop) {
2106 if (lp->parent() == nullptr) {
2107 // Not a nested loop. Make it a child of the method's pseudo loop.
2108 root_loop->add_nested_loop(lp);
2109 }
2110 if (block == lp->head()) {
2111 // Add nested loop to member list of parent loop.
2112 lp->parent()->add_member(lp);
2113 }
2114 }
2115 }
2116
2117 return root_loop;
2118 }
2119
2120 //------------------------------push_pred--------------------------------------
2121 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) {
2122 Node* pred_n = blk->pred(i);
2123 Block* pred = cfg->get_block_for_node(pred_n);
2124 CFGLoop *pred_loop = pred->_loop;
2125 if (pred_loop == nullptr) {
2126 // Filter out blocks for non-single-entry loops.
2127 // For all reasonable loops, the head occurs before the tail in RPO.
2128 if (pred->_rpo > head()->_rpo) {
2129 pred->_loop = this;
2130 worklist.push(pred);
2131 }
2132 } else if (pred_loop != this) {
2133 // Nested loop.
2134 while (pred_loop->_parent != nullptr && pred_loop->_parent != this) {
2135 pred_loop = pred_loop->_parent;
2136 }
2137 // Make pred's loop be a child
2138 if (pred_loop->_parent == nullptr) {
2139 add_nested_loop(pred_loop);
2140 // Continue with loop entry predecessor.
2141 Block* pred_head = pred_loop->head();
2142 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
2143 assert(pred_head != head(), "loop head in only one loop");
2144 push_pred(pred_head, LoopNode::EntryControl, worklist, cfg);
2145 } else {
2146 assert(pred_loop->_parent == this && _parent == nullptr, "just checking");
2147 }
2148 }
2149 }
2150
2151 //------------------------------add_nested_loop--------------------------------
2152 // Make cl a child of the current loop in the loop tree.
2153 void CFGLoop::add_nested_loop(CFGLoop* cl) {
2154 assert(_parent == nullptr, "no parent yet");
2155 assert(cl != this, "not my own parent");
2156 cl->_parent = this;
2157 CFGLoop* ch = _child;
2158 if (ch == nullptr) {
2159 _child = cl;
2160 } else {
2161 while (ch->_sibling != nullptr) { ch = ch->_sibling; }
2162 ch->_sibling = cl;
2163 }
2164 }
2165
2166 //------------------------------compute_loop_depth-----------------------------
2167 // Store the loop depth in each CFGLoop object.
2168 // Recursively walk the children to do the same for them.
2169 void CFGLoop::compute_loop_depth(int depth) {
2170 _depth = depth;
2171 CFGLoop* ch = _child;
2172 while (ch != nullptr) {
2173 ch->compute_loop_depth(depth + 1);
2174 ch = ch->_sibling;
2175 }
2176 }
2177
2178 //------------------------------compute_freq-----------------------------------
2179 // Compute the frequency of each block and loop, relative to a single entry
2180 // into the dominating loop head.
2181 void CFGLoop::compute_freq() {
2182 // Bottom up traversal of loop tree (visit inner loops first.)
2183 // Set loop head frequency to 1.0, then transitively
2184 // compute frequency for all successors in the loop,
2185 // as well as for each exit edge. Inner loops are
2186 // treated as single blocks with loop exit targets
2187 // as the successor blocks.
2188
2189 // Nested loops first
2190 CFGLoop* ch = _child;
2191 while (ch != nullptr) {
2192 ch->compute_freq();
2193 ch = ch->_sibling;
2194 }
2195 assert (_members.length() > 0, "no empty loops");
2196 Block* hd = head();
2197 hd->_freq = 1.0;
2198 for (int i = 0; i < _members.length(); i++) {
2199 CFGElement* s = _members.at(i);
2200 double freq = s->_freq;
2201 if (s->is_block()) {
2202 Block* b = s->as_Block();
2203 for (uint j = 0; j < b->_num_succs; j++) {
2204 Block* sb = b->_succs[j];
2205 update_succ_freq(sb, freq * b->succ_prob(j));
2206 }
2207 } else {
2208 CFGLoop* lp = s->as_CFGLoop();
2209 assert(lp->_parent == this, "immediate child");
2210 for (int k = 0; k < lp->_exits.length(); k++) {
2211 Block* eb = lp->_exits.at(k).get_target();
2212 double prob = lp->_exits.at(k).get_prob();
2213 update_succ_freq(eb, freq * prob);
2214 }
2215 }
2216 }
2217
2218 // For all loops other than the outer, "method" loop,
2219 // sum and normalize the exit probability. The "method" loop
2220 // should keep the initial exit probability of 1, so that
2221 // inner blocks do not get erroneously scaled.
2222 if (_depth != 0) {
2223 // Total the exit probabilities for this loop.
2224 double exits_sum = 0.0f;
2225 for (int i = 0; i < _exits.length(); i++) {
2226 exits_sum += _exits.at(i).get_prob();
2227 }
2228
2229 // Normalize the exit probabilities. Until now, the
2230 // probabilities estimate the possibility of exit per
2231 // a single loop iteration; afterward, they estimate
2232 // the probability of exit per loop entry.
2233 for (int i = 0; i < _exits.length(); i++) {
2234 Block* et = _exits.at(i).get_target();
2235 float new_prob = 0.0f;
2236 if (_exits.at(i).get_prob() > 0.0f) {
2237 new_prob = _exits.at(i).get_prob() / exits_sum;
2238 }
2239 BlockProbPair bpp(et, new_prob);
2240 _exits.at_put(i, bpp);
2241 }
2242
2243 // Save the total, but guard against unreasonable probability,
2244 // as the value is used to estimate the loop trip count.
2245 // An infinite trip count would blur relative block
2246 // frequencies.
2247 if (exits_sum > 1.0f) exits_sum = 1.0;
2248 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
2249 _exit_prob = exits_sum;
2250 }
2251 }
2252
2253 //------------------------------succ_prob-------------------------------------
2254 // Determine the probability of reaching successor 'i' from the receiver block.
2255 float Block::succ_prob(uint i) {
2256 int eidx = end_idx();
2257 Node *n = get_node(eidx); // Get ending Node
2258
2259 int op = n->Opcode();
2260 if (n->is_Mach()) {
2261 if (n->is_MachNullCheck()) {
2262 // Can only reach here if called after lcm. The original Op_If is gone,
2263 // so we attempt to infer the probability from one or both of the
2264 // successor blocks.
2265 assert(_num_succs == 2, "expecting 2 successors of a null check");
2266 // If either successor has only one predecessor, then the
2267 // probability estimate can be derived using the
2268 // relative frequency of the successor and this block.
2269 if (_succs[i]->num_preds() == 2) {
2270 return _succs[i]->_freq / _freq;
2271 } else if (_succs[1-i]->num_preds() == 2) {
2272 return 1 - (_succs[1-i]->_freq / _freq);
2273 } else {
2274 // Estimate using both successor frequencies
2275 float freq = _succs[i]->_freq;
2276 return freq / (freq + _succs[1-i]->_freq);
2277 }
2278 }
2279 op = n->as_Mach()->ideal_Opcode();
2280 }
2281
2282
2283 // Switch on branch type
2284 switch( op ) {
2285 case Op_CountedLoopEnd:
2286 case Op_If: {
2287 assert (i < 2, "just checking");
2288 // Conditionals pass on only part of their frequency
2289 float prob = n->as_MachIf()->_prob;
2290 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
2291 // If succ[i] is the FALSE branch, invert path info
2292 if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) {
2293 return 1.0f - prob; // not taken
2294 } else {
2295 return prob; // taken
2296 }
2297 }
2298
2299 case Op_Jump:
2300 return n->as_MachJump()->_probs[get_node(i + eidx + 1)->as_JumpProj()->_con];
2301
2302 case Op_Catch: {
2303 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
2304 if (ci->_con == CatchProjNode::fall_through_index) {
2305 // Fall-thru path gets the lion's share.
2306 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
2307 } else {
2308 // Presume exceptional paths are equally unlikely
2309 return PROB_UNLIKELY_MAG(5);
2310 }
2311 }
2312
2313 case Op_Root:
2314 case Op_Goto:
2315 // Pass frequency straight thru to target
2316 return 1.0f;
2317
2318 case Op_NeverBranch: {
2319 Node* succ = n->as_NeverBranch()->proj_out(0)->unique_ctrl_out();
2320 if (_succs[i]->head() == succ) {
2321 return 1.0f;
2322 }
2323 return 0.0f;
2324 }
2325
2326 case Op_TailCall:
2327 case Op_TailJump:
2328 case Op_ForwardException:
2329 case Op_Return:
2330 case Op_Halt:
2331 case Op_Rethrow:
2332 // Do not push out freq to root block
2333 return 0.0f;
2334
2335 default:
2336 ShouldNotReachHere();
2337 }
2338
2339 return 0.0f;
2340 }
2341
2342 //------------------------------num_fall_throughs-----------------------------
2343 // Return the number of fall-through candidates for a block
2344 int Block::num_fall_throughs() {
2345 int eidx = end_idx();
2346 Node *n = get_node(eidx); // Get ending Node
2347
2348 int op = n->Opcode();
2349 if (n->is_Mach()) {
2350 if (n->is_MachNullCheck()) {
2351 // In theory, either side can fall-thru, for simplicity sake,
2352 // let's say only the false branch can now.
2353 return 1;
2354 }
2355 op = n->as_Mach()->ideal_Opcode();
2356 }
2357
2358 // Switch on branch type
2359 switch( op ) {
2360 case Op_CountedLoopEnd:
2361 case Op_If:
2362 return 2;
2363
2364 case Op_Root:
2365 case Op_Goto:
2366 return 1;
2367
2368 case Op_Catch: {
2369 for (uint i = 0; i < _num_succs; i++) {
2370 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
2371 if (ci->_con == CatchProjNode::fall_through_index) {
2372 return 1;
2373 }
2374 }
2375 return 0;
2376 }
2377
2378 case Op_Jump:
2379 case Op_NeverBranch:
2380 case Op_TailCall:
2381 case Op_TailJump:
2382 case Op_ForwardException:
2383 case Op_Return:
2384 case Op_Halt:
2385 case Op_Rethrow:
2386 return 0;
2387
2388 default:
2389 ShouldNotReachHere();
2390 }
2391
2392 return 0;
2393 }
2394
2395 //------------------------------succ_fall_through-----------------------------
2396 // Return true if a specific successor could be fall-through target.
2397 bool Block::succ_fall_through(uint i) {
2398 int eidx = end_idx();
2399 Node *n = get_node(eidx); // Get ending Node
2400
2401 int op = n->Opcode();
2402 if (n->is_Mach()) {
2403 if (n->is_MachNullCheck()) {
2404 // In theory, either side can fall-thru, for simplicity sake,
2405 // let's say only the false branch can now.
2406 return get_node(i + eidx + 1)->Opcode() == Op_IfFalse;
2407 }
2408 op = n->as_Mach()->ideal_Opcode();
2409 }
2410
2411 // Switch on branch type
2412 switch( op ) {
2413 case Op_CountedLoopEnd:
2414 case Op_If:
2415 case Op_Root:
2416 case Op_Goto:
2417 return true;
2418
2419 case Op_Catch: {
2420 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
2421 return ci->_con == CatchProjNode::fall_through_index;
2422 }
2423
2424 case Op_Jump:
2425 case Op_NeverBranch:
2426 case Op_TailCall:
2427 case Op_TailJump:
2428 case Op_ForwardException:
2429 case Op_Return:
2430 case Op_Halt:
2431 case Op_Rethrow:
2432 return false;
2433
2434 default:
2435 ShouldNotReachHere();
2436 }
2437
2438 return false;
2439 }
2440
2441 //------------------------------update_uncommon_branch------------------------
2442 // Update the probability of a two-branch to be uncommon
2443 void Block::update_uncommon_branch(Block* ub) {
2444 int eidx = end_idx();
2445 Node *n = get_node(eidx); // Get ending Node
2446
2447 int op = n->as_Mach()->ideal_Opcode();
2448
2449 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
2450 assert(num_fall_throughs() == 2, "must be a two way branch block");
2451
2452 // Which successor is ub?
2453 uint s;
2454 for (s = 0; s <_num_succs; s++) {
2455 if (_succs[s] == ub) break;
2456 }
2457 assert(s < 2, "uncommon successor must be found");
2458
2459 // If ub is the true path, make the proability small, else
2460 // ub is the false path, and make the probability large
2461 bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse);
2462
2463 // Get existing probability
2464 float p = n->as_MachIf()->_prob;
2465
2466 if (invert) p = 1.0 - p;
2467 if (p > PROB_MIN) {
2468 p = PROB_MIN;
2469 }
2470 if (invert) p = 1.0 - p;
2471
2472 n->as_MachIf()->_prob = p;
2473 }
2474
2475 //------------------------------update_succ_freq-------------------------------
2476 // Update the appropriate frequency associated with block 'b', a successor of
2477 // a block in this loop.
2478 void CFGLoop::update_succ_freq(Block* b, double freq) {
2479 if (b->_loop == this) {
2480 if (b == head()) {
2481 // back branch within the loop
2482 // Do nothing now, the loop carried frequency will be
2483 // adjust later in scale_freq().
2484 } else {
2485 // simple branch within the loop
2486 b->_freq += freq;
2487 }
2488 } else if (!in_loop_nest(b)) {
2489 // branch is exit from this loop
2490 BlockProbPair bpp(b, freq);
2491 _exits.append(bpp);
2492 } else {
2493 // branch into nested loop
2494 CFGLoop* ch = b->_loop;
2495 ch->_freq += freq;
2496 }
2497 }
2498
2499 //------------------------------in_loop_nest-----------------------------------
2500 // Determine if block b is in the receiver's loop nest.
2501 bool CFGLoop::in_loop_nest(Block* b) {
2502 int depth = _depth;
2503 CFGLoop* b_loop = b->_loop;
2504 int b_depth = b_loop->_depth;
2505 if (depth == b_depth) {
2506 return true;
2507 }
2508 while (b_depth > depth) {
2509 b_loop = b_loop->_parent;
2510 b_depth = b_loop->_depth;
2511 }
2512 return b_loop == this;
2513 }
2514
2515 //------------------------------scale_freq-------------------------------------
2516 // Scale frequency of loops and blocks by trip counts from outer loops
2517 // Do a top down traversal of loop tree (visit outer loops first.)
2518 void CFGLoop::scale_freq() {
2519 double loop_freq = _freq * trip_count();
2520 _freq = loop_freq;
2521 for (int i = 0; i < _members.length(); i++) {
2522 CFGElement* s = _members.at(i);
2523 double block_freq = s->_freq * loop_freq;
2524 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
2525 block_freq = MIN_BLOCK_FREQUENCY;
2526 s->_freq = block_freq;
2527 }
2528 CFGLoop* ch = _child;
2529 while (ch != nullptr) {
2530 ch->scale_freq();
2531 ch = ch->_sibling;
2532 }
2533 }
2534
2535 // Frequency of outer loop
2536 double CFGLoop::outer_loop_freq() const {
2537 if (_child != nullptr) {
2538 return _child->_freq;
2539 }
2540 return _freq;
2541 }
2542
2543 #ifndef PRODUCT
2544 //------------------------------dump_tree--------------------------------------
2545 void CFGLoop::dump_tree() const {
2546 dump();
2547 if (_child != nullptr) _child->dump_tree();
2548 if (_sibling != nullptr) _sibling->dump_tree();
2549 }
2550
2551 //------------------------------dump-------------------------------------------
2552 void CFGLoop::dump() const {
2553 for (int i = 0; i < _depth; i++) tty->print(" ");
2554 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
2555 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
2556 for (int i = 0; i < _depth; i++) tty->print(" ");
2557 tty->print(" members:");
2558 int k = 0;
2559 for (int i = 0; i < _members.length(); i++) {
2560 if (k++ >= 6) {
2561 tty->print("\n ");
2562 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2563 k = 0;
2564 }
2565 CFGElement *s = _members.at(i);
2566 if (s->is_block()) {
2567 Block *b = s->as_Block();
2568 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
2569 } else {
2570 CFGLoop* lp = s->as_CFGLoop();
2571 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
2572 }
2573 }
2574 tty->print("\n");
2575 for (int i = 0; i < _depth; i++) tty->print(" ");
2576 tty->print(" exits: ");
2577 k = 0;
2578 for (int i = 0; i < _exits.length(); i++) {
2579 if (k++ >= 7) {
2580 tty->print("\n ");
2581 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2582 k = 0;
2583 }
2584 Block *blk = _exits.at(i).get_target();
2585 double prob = _exits.at(i).get_prob();
2586 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2587 }
2588 tty->print("\n");
2589 }
2590 #endif