1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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23 */
24
25 #include "precompiled.hpp"
26 #include "libadt/vectset.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "opto/block.hpp"
30 #include "opto/c2compiler.hpp"
31 #include "opto/callnode.hpp"
32 #include "opto/cfgnode.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 "opto/chaitin.hpp"
39 #include "runtime/deoptimization.hpp"
40
41 // Portions of code courtesy of Clifford Click
42
43 // Optimization - Graph Style
44
45 // To avoid float value underflow
46 #define MIN_BLOCK_FREQUENCY 1.e-35f
47
48 //----------------------------schedule_node_into_block-------------------------
49 // Insert node n into block b. Look for projections of n and make sure they
50 // are in b also.
51 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
52 // Set basic block of n, Add n to b,
53 map_node_to_block(n, b);
54 b->add_inst(n);
55
56 // After Matching, nearly any old Node may have projections trailing it.
57 // These are usually machine-dependent flags. In any case, they might
58 // float to another block below this one. Move them up.
59 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
60 Node* use = n->fast_out(i);
61 if (use->is_Proj()) {
62 Block* buse = get_block_for_node(use);
63 if (buse != b) { // In wrong block?
64 if (buse != NULL) {
65 buse->find_remove(use); // Remove from wrong block
66 }
67 map_node_to_block(use, b);
68 b->add_inst(use);
69 }
70 }
71 }
72 }
73
74 //----------------------------replace_block_proj_ctrl-------------------------
75 // Nodes that have is_block_proj() nodes as their control need to use
76 // the appropriate Region for their actual block as their control since
77 // the projection will be in a predecessor block.
78 void PhaseCFG::replace_block_proj_ctrl( Node *n ) {
79 const Node *in0 = n->in(0);
80 assert(in0 != NULL, "Only control-dependent");
81 const Node *p = in0->is_block_proj();
82 if (p != NULL && p != n) { // Control from a block projection?
83 assert(!n->pinned() || n->is_MachConstantBase(), "only pinned MachConstantBase node is expected here");
84 // Find trailing Region
85 Block *pb = get_block_for_node(in0); // Block-projection already has basic block
86 uint j = 0;
87 if (pb->_num_succs != 1) { // More then 1 successor?
88 // Search for successor
89 uint max = pb->number_of_nodes();
90 assert( max > 1, "" );
91 uint start = max - pb->_num_succs;
92 // Find which output path belongs to projection
93 for (j = start; j < max; j++) {
94 if( pb->get_node(j) == in0 )
95 break;
96 }
97 assert( j < max, "must find" );
98 // Change control to match head of successor basic block
99 j -= start;
100 }
101 n->set_req(0, pb->_succs[j]->head());
102 }
103 }
104
105 bool PhaseCFG::is_dominator(Node* dom_node, Node* node) {
106 if (dom_node == node) {
107 return true;
108 }
109 Block* d = get_block_for_node(dom_node);
110 Block* n = get_block_for_node(node);
111 if (d == n) {
112 if (dom_node->is_block_start()) {
113 return true;
114 }
115 if (node->is_block_start()) {
116 return false;
117 }
118 if (dom_node->is_block_proj()) {
119 return false;
120 }
121 if (node->is_block_proj()) {
122 return true;
123 }
124 #ifdef ASSERT
125 node->dump();
126 dom_node->dump();
127 #endif
128 fatal("unhandled");
129 return false;
130 }
131 return d->dom_lca(n) == d;
132 }
133
134 //------------------------------schedule_pinned_nodes--------------------------
135 // Set the basic block for Nodes pinned into blocks
136 void PhaseCFG::schedule_pinned_nodes(VectorSet &visited) {
137 // Allocate node stack of size C->live_nodes()+8 to avoid frequent realloc
138 GrowableArray <Node *> spstack(C->live_nodes() + 8);
139 spstack.push(_root);
140 while (spstack.is_nonempty()) {
141 Node* node = spstack.pop();
142 if (!visited.test_set(node->_idx)) { // Test node and flag it as visited
143 if (node->pinned() && !has_block(node)) { // Pinned? Nail it down!
144 assert(node->in(0), "pinned Node must have Control");
145 // Before setting block replace block_proj control edge
146 replace_block_proj_ctrl(node);
147 Node* input = node->in(0);
148 while (!input->is_block_start()) {
149 input = input->in(0);
150 }
151 Block* block = get_block_for_node(input); // Basic block of controlling input
152 schedule_node_into_block(node, block);
153 }
154
155 // If the node has precedence edges (added when CastPP nodes are
156 // removed in final_graph_reshaping), fix the control of the
157 // node to cover the precedence edges and remove the
158 // dependencies.
159 Node* n = NULL;
160 for (uint i = node->len()-1; i >= node->req(); i--) {
161 Node* m = node->in(i);
162 if (m == NULL) continue;
163 // Skip the precedence edge if the test that guarded a CastPP:
164 // - was optimized out during escape analysis
165 // (OptimizePtrCompare): the CastPP's control isn't an end of
166 // block.
167 // - is moved in the branch of a dominating If: the control of
168 // the CastPP is then a Region.
169 if (m->is_block_proj() || m->is_block_start()) {
170 node->rm_prec(i);
171 if (n == NULL) {
172 n = m;
173 } else {
174 assert(is_dominator(n, m) || is_dominator(m, n), "one must dominate the other");
175 n = is_dominator(n, m) ? m : n;
176 }
177 }
178 }
179 if (n != NULL) {
180 assert(node->in(0), "control should have been set");
181 assert(is_dominator(n, node->in(0)) || is_dominator(node->in(0), n), "one must dominate the other");
182 if (!is_dominator(n, node->in(0))) {
183 node->set_req(0, n);
184 }
185 }
186
187 // process all inputs that are non NULL
188 for (int i = node->req() - 1; i >= 0; --i) {
189 if (node->in(i) != NULL) {
190 spstack.push(node->in(i));
191 }
192 }
193 }
194 }
195 }
196
197 #ifdef ASSERT
198 // Assert that new input b2 is dominated by all previous inputs.
199 // Check this by by seeing that it is dominated by b1, the deepest
200 // input observed until b2.
201 static void assert_dom(Block* b1, Block* b2, Node* n, const PhaseCFG* cfg) {
202 if (b1 == NULL) return;
203 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
204 Block* tmp = b2;
205 while (tmp != b1 && tmp != NULL) {
206 tmp = tmp->_idom;
207 }
208 if (tmp != b1) {
209 // Detected an unschedulable graph. Print some nice stuff and die.
210 tty->print_cr("!!! Unschedulable graph !!!");
211 for (uint j=0; j<n->len(); j++) { // For all inputs
212 Node* inn = n->in(j); // Get input
213 if (inn == NULL) continue; // Ignore NULL, missing inputs
214 Block* inb = cfg->get_block_for_node(inn);
215 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
216 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
217 inn->dump();
218 }
219 tty->print("Failing node: ");
220 n->dump();
221 assert(false, "unscheduable graph");
222 }
223 }
224 #endif
225
226 static Block* find_deepest_input(Node* n, const PhaseCFG* cfg) {
227 // Find the last input dominated by all other inputs.
228 Block* deepb = NULL; // Deepest block so far
229 int deepb_dom_depth = 0;
230 for (uint k = 0; k < n->len(); k++) { // For all inputs
231 Node* inn = n->in(k); // Get input
232 if (inn == NULL) continue; // Ignore NULL, missing inputs
233 Block* inb = cfg->get_block_for_node(inn);
234 assert(inb != NULL, "must already have scheduled this input");
235 if (deepb_dom_depth < (int) inb->_dom_depth) {
236 // The new inb must be dominated by the previous deepb.
237 // The various inputs must be linearly ordered in the dom
238 // tree, or else there will not be a unique deepest block.
239 DEBUG_ONLY(assert_dom(deepb, inb, n, cfg));
240 deepb = inb; // Save deepest block
241 deepb_dom_depth = deepb->_dom_depth;
242 }
243 }
244 assert(deepb != NULL, "must be at least one input to n");
245 return deepb;
246 }
247
248
249 //------------------------------schedule_early---------------------------------
250 // Find the earliest Block any instruction can be placed in. Some instructions
251 // are pinned into Blocks. Unpinned instructions can appear in last block in
252 // which all their inputs occur.
253 bool PhaseCFG::schedule_early(VectorSet &visited, Node_Stack &roots) {
254 // Allocate stack with enough space to avoid frequent realloc
255 Node_Stack nstack(roots.size() + 8);
256 // _root will be processed among C->top() inputs
257 roots.push(C->top(), 0);
258 visited.set(C->top()->_idx);
259
260 while (roots.size() != 0) {
261 // Use local variables nstack_top_n & nstack_top_i to cache values
262 // on stack's top.
263 Node* parent_node = roots.node();
264 uint input_index = 0;
265 roots.pop();
266
267 while (true) {
268 if (input_index == 0) {
269 // Fixup some control. Constants without control get attached
270 // to root and nodes that use is_block_proj() nodes should be attached
271 // to the region that starts their block.
272 const Node* control_input = parent_node->in(0);
273 if (control_input != NULL) {
274 replace_block_proj_ctrl(parent_node);
275 } else {
276 // Is a constant with NO inputs?
277 if (parent_node->req() == 1) {
278 parent_node->set_req(0, _root);
279 }
280 }
281 }
282
283 // First, visit all inputs and force them to get a block. If an
284 // input is already in a block we quit following inputs (to avoid
285 // cycles). Instead we put that Node on a worklist to be handled
286 // later (since IT'S inputs may not have a block yet).
287
288 // Assume all n's inputs will be processed
289 bool done = true;
290
291 while (input_index < parent_node->len()) {
292 Node* in = parent_node->in(input_index++);
293 if (in == NULL) {
294 continue;
295 }
296
297 int is_visited = visited.test_set(in->_idx);
298 if (!has_block(in)) {
299 if (is_visited) {
300 assert(false, "graph should be schedulable");
301 return false;
302 }
303 // Save parent node and next input's index.
304 nstack.push(parent_node, input_index);
305 // Process current input now.
306 parent_node = in;
307 input_index = 0;
308 // Not all n's inputs processed.
309 done = false;
310 break;
311 } else if (!is_visited) {
312 // Visit this guy later, using worklist
313 roots.push(in, 0);
314 }
315 }
316
317 if (done) {
318 // All of n's inputs have been processed, complete post-processing.
319
320 // Some instructions are pinned into a block. These include Region,
321 // Phi, Start, Return, and other control-dependent instructions and
322 // any projections which depend on them.
323 if (!parent_node->pinned()) {
324 // Set earliest legal block.
325 Block* earliest_block = find_deepest_input(parent_node, this);
326 map_node_to_block(parent_node, earliest_block);
327 } else {
328 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");
329 }
330
331 if (nstack.is_empty()) {
332 // Finished all nodes on stack.
333 // Process next node on the worklist 'roots'.
334 break;
335 }
336 // Get saved parent node and next input's index.
337 parent_node = nstack.node();
338 input_index = nstack.index();
339 nstack.pop();
340 }
341 }
342 }
343 return true;
344 }
345
346 //------------------------------dom_lca----------------------------------------
347 // Find least common ancestor in dominator tree
348 // LCA is a current notion of LCA, to be raised above 'this'.
349 // As a convenient boundary condition, return 'this' if LCA is NULL.
350 // Find the LCA of those two nodes.
351 Block* Block::dom_lca(Block* LCA) {
352 if (LCA == NULL || LCA == this) return this;
353
354 Block* anc = this;
355 while (anc->_dom_depth > LCA->_dom_depth)
356 anc = anc->_idom; // Walk up till anc is as high as LCA
357
358 while (LCA->_dom_depth > anc->_dom_depth)
359 LCA = LCA->_idom; // Walk up till LCA is as high as anc
360
361 while (LCA != anc) { // Walk both up till they are the same
362 LCA = LCA->_idom;
363 anc = anc->_idom;
364 }
365
366 return LCA;
367 }
368
369 //--------------------------raise_LCA_above_use--------------------------------
370 // We are placing a definition, and have been given a def->use edge.
371 // The definition must dominate the use, so move the LCA upward in the
372 // dominator tree to dominate the use. If the use is a phi, adjust
373 // the LCA only with the phi input paths which actually use this def.
374 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) {
375 Block* buse = cfg->get_block_for_node(use);
376 if (buse == NULL) return LCA; // Unused killing Projs have no use block
377 if (!use->is_Phi()) return buse->dom_lca(LCA);
378 uint pmax = use->req(); // Number of Phi inputs
379 // Why does not this loop just break after finding the matching input to
380 // the Phi? Well...it's like this. I do not have true def-use/use-def
381 // chains. Means I cannot distinguish, from the def-use direction, which
382 // of many use-defs lead from the same use to the same def. That is, this
383 // Phi might have several uses of the same def. Each use appears in a
384 // different predecessor block. But when I enter here, I cannot distinguish
385 // which use-def edge I should find the predecessor block for. So I find
386 // them all. Means I do a little extra work if a Phi uses the same value
387 // more than once.
388 for (uint j=1; j<pmax; j++) { // For all inputs
389 if (use->in(j) == def) { // Found matching input?
390 Block* pred = cfg->get_block_for_node(buse->pred(j));
391 LCA = pred->dom_lca(LCA);
392 }
393 }
394 return LCA;
395 }
396
397 //----------------------------raise_LCA_above_marks----------------------------
398 // Return a new LCA that dominates LCA and any of its marked predecessors.
399 // Search all my parents up to 'early' (exclusive), looking for predecessors
400 // which are marked with the given index. Return the LCA (in the dom tree)
401 // of all marked blocks. If there are none marked, return the original
402 // LCA.
403 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) {
404 Block_List worklist;
405 worklist.push(LCA);
406 while (worklist.size() > 0) {
407 Block* mid = worklist.pop();
408 if (mid == early) continue; // stop searching here
409
410 // Test and set the visited bit.
411 if (mid->raise_LCA_visited() == mark) continue; // already visited
412
413 // Don't process the current LCA, otherwise the search may terminate early
414 if (mid != LCA && mid->raise_LCA_mark() == mark) {
415 // Raise the LCA.
416 LCA = mid->dom_lca(LCA);
417 if (LCA == early) break; // stop searching everywhere
418 assert(early->dominates(LCA), "early is high enough");
419 // Resume searching at that point, skipping intermediate levels.
420 worklist.push(LCA);
421 if (LCA == mid)
422 continue; // Don't mark as visited to avoid early termination.
423 } else {
424 // Keep searching through this block's predecessors.
425 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
426 Block* mid_parent = cfg->get_block_for_node(mid->pred(j));
427 worklist.push(mid_parent);
428 }
429 }
430 mid->set_raise_LCA_visited(mark);
431 }
432 return LCA;
433 }
434
435 //--------------------------memory_early_block--------------------------------
436 // This is a variation of find_deepest_input, the heart of schedule_early.
437 // Find the "early" block for a load, if we considered only memory and
438 // address inputs, that is, if other data inputs were ignored.
439 //
440 // Because a subset of edges are considered, the resulting block will
441 // be earlier (at a shallower dom_depth) than the true schedule_early
442 // point of the node. We compute this earlier block as a more permissive
443 // site for anti-dependency insertion, but only if subsume_loads is enabled.
444 static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) {
445 Node* base;
446 Node* index;
447 Node* store = load->in(MemNode::Memory);
448 load->as_Mach()->memory_inputs(base, index);
449
450 assert(base != NodeSentinel && index != NodeSentinel,
451 "unexpected base/index inputs");
452
453 Node* mem_inputs[4];
454 int mem_inputs_length = 0;
455 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
456 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
457 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
458
459 // In the comparision below, add one to account for the control input,
460 // which may be null, but always takes up a spot in the in array.
461 if (mem_inputs_length + 1 < (int) load->req()) {
462 // This "load" has more inputs than just the memory, base and index inputs.
463 // For purposes of checking anti-dependences, we need to start
464 // from the early block of only the address portion of the instruction,
465 // and ignore other blocks that may have factored into the wider
466 // schedule_early calculation.
467 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
468
469 Block* deepb = NULL; // Deepest block so far
470 int deepb_dom_depth = 0;
471 for (int i = 0; i < mem_inputs_length; i++) {
472 Block* inb = cfg->get_block_for_node(mem_inputs[i]);
473 if (deepb_dom_depth < (int) inb->_dom_depth) {
474 // The new inb must be dominated by the previous deepb.
475 // The various inputs must be linearly ordered in the dom
476 // tree, or else there will not be a unique deepest block.
477 DEBUG_ONLY(assert_dom(deepb, inb, load, cfg));
478 deepb = inb; // Save deepest block
479 deepb_dom_depth = deepb->_dom_depth;
480 }
481 }
482 early = deepb;
483 }
484
485 return early;
486 }
487
488 //--------------------------insert_anti_dependences---------------------------
489 // A load may need to witness memory that nearby stores can overwrite.
490 // For each nearby store, either insert an "anti-dependence" edge
491 // from the load to the store, or else move LCA upward to force the
492 // load to (eventually) be scheduled in a block above the store.
493 //
494 // Do not add edges to stores on distinct control-flow paths;
495 // only add edges to stores which might interfere.
496 //
497 // Return the (updated) LCA. There will not be any possibly interfering
498 // store between the load's "early block" and the updated LCA.
499 // Any stores in the updated LCA will have new precedence edges
500 // back to the load. The caller is expected to schedule the load
501 // in the LCA, in which case the precedence edges will make LCM
502 // preserve anti-dependences. The caller may also hoist the load
503 // above the LCA, if it is not the early block.
504 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
505 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
506 assert(LCA != NULL, "");
507 DEBUG_ONLY(Block* LCA_orig = LCA);
508
509 // Compute the alias index. Loads and stores with different alias indices
510 // do not need anti-dependence edges.
511 int load_alias_idx = C->get_alias_index(load->adr_type());
512 #ifdef ASSERT
513 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
514 (PrintOpto || VerifyAliases ||
515 (PrintMiscellaneous && (WizardMode || Verbose)))) {
516 // Load nodes should not consume all of memory.
517 // Reporting a bottom type indicates a bug in adlc.
518 // If some particular type of node validly consumes all of memory,
519 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
520 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
521 load->dump(2);
522 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
523 }
524 #endif
525 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
526 "String compare is only known 'load' that does not conflict with any stores");
527 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals),
528 "String equals is a 'load' that does not conflict with any stores");
529 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf),
530 "String indexOf is a 'load' that does not conflict with any stores");
531 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOfChar),
532 "String indexOfChar is a 'load' that does not conflict with any stores");
533 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq),
534 "Arrays equals is a 'load' that does not conflict with any stores");
535 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_HasNegatives),
536 "HasNegatives is a 'load' that does not conflict with any stores");
537
538 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
539 // It is impossible to spoil this load by putting stores before it,
540 // because we know that the stores will never update the value
541 // which 'load' must witness.
542 return LCA;
543 }
544
545 node_idx_t load_index = load->_idx;
546
547 // Note the earliest legal placement of 'load', as determined by
548 // by the unique point in the dom tree where all memory effects
549 // and other inputs are first available. (Computed by schedule_early.)
550 // For normal loads, 'early' is the shallowest place (dom graph wise)
551 // to look for anti-deps between this load and any store.
552 Block* early = get_block_for_node(load);
553
554 // If we are subsuming loads, compute an "early" block that only considers
555 // memory or address inputs. This block may be different than the
556 // schedule_early block in that it could be at an even shallower depth in the
557 // dominator tree, and allow for a broader discovery of anti-dependences.
558 if (C->subsume_loads()) {
559 early = memory_early_block(load, early, this);
560 }
561
562 ResourceArea *area = Thread::current()->resource_area();
563 Node_List worklist_mem(area); // prior memory state to store
564 Node_List worklist_store(area); // possible-def to explore
565 Node_List worklist_visited(area); // visited mergemem nodes
566 Node_List non_early_stores(area); // all relevant stores outside of early
567 bool must_raise_LCA = false;
568
569 #ifdef TRACK_PHI_INPUTS
570 // %%% This extra checking fails because MergeMem nodes are not GVNed.
571 // Provide "phi_inputs" to check if every input to a PhiNode is from the
572 // original memory state. This indicates a PhiNode for which should not
573 // prevent the load from sinking. For such a block, set_raise_LCA_mark
574 // may be overly conservative.
575 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
576 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
577 #endif
578
579 // 'load' uses some memory state; look for users of the same state.
580 // Recurse through MergeMem nodes to the stores that use them.
581
582 // Each of these stores is a possible definition of memory
583 // that 'load' needs to use. We need to force 'load'
584 // to occur before each such store. When the store is in
585 // the same block as 'load', we insert an anti-dependence
586 // edge load->store.
587
588 // The relevant stores "nearby" the load consist of a tree rooted
589 // at initial_mem, with internal nodes of type MergeMem.
590 // Therefore, the branches visited by the worklist are of this form:
591 // initial_mem -> (MergeMem ->)* store
592 // The anti-dependence constraints apply only to the fringe of this tree.
593
594 Node* initial_mem = load->in(MemNode::Memory);
595 worklist_store.push(initial_mem);
596 worklist_visited.push(initial_mem);
597 worklist_mem.push(NULL);
598 while (worklist_store.size() > 0) {
599 // Examine a nearby store to see if it might interfere with our load.
600 Node* mem = worklist_mem.pop();
601 Node* store = worklist_store.pop();
602 uint op = store->Opcode();
603
604 // MergeMems do not directly have anti-deps.
605 // Treat them as internal nodes in a forward tree of memory states,
606 // the leaves of which are each a 'possible-def'.
607 if (store == initial_mem // root (exclusive) of tree we are searching
608 || op == Op_MergeMem // internal node of tree we are searching
609 ) {
610 mem = store; // It's not a possibly interfering store.
611 if (store == initial_mem)
612 initial_mem = NULL; // only process initial memory once
613
614 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
615 store = mem->fast_out(i);
616 if (store->is_MergeMem()) {
617 // Be sure we don't get into combinatorial problems.
618 // (Allow phis to be repeated; they can merge two relevant states.)
619 uint j = worklist_visited.size();
620 for (; j > 0; j--) {
621 if (worklist_visited.at(j-1) == store) break;
622 }
623 if (j > 0) continue; // already on work list; do not repeat
624 worklist_visited.push(store);
625 }
626 worklist_mem.push(mem);
627 worklist_store.push(store);
628 }
629 continue;
630 }
631
632 if (op == Op_MachProj || op == Op_Catch) continue;
633 if (store->needs_anti_dependence_check()) continue; // not really a store
634
635 // Compute the alias index. Loads and stores with different alias
636 // indices do not need anti-dependence edges. Wide MemBar's are
637 // anti-dependent on everything (except immutable memories).
638 const TypePtr* adr_type = store->adr_type();
639 if (!C->can_alias(adr_type, load_alias_idx)) continue;
640
641 // Most slow-path runtime calls do NOT modify Java memory, but
642 // they can block and so write Raw memory.
643 if (store->is_Mach()) {
644 MachNode* mstore = store->as_Mach();
645 if (load_alias_idx != Compile::AliasIdxRaw) {
646 // Check for call into the runtime using the Java calling
647 // convention (and from there into a wrapper); it has no
648 // _method. Can't do this optimization for Native calls because
649 // they CAN write to Java memory.
650 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
651 assert(mstore->is_MachSafePoint(), "");
652 MachSafePointNode* ms = (MachSafePointNode*) mstore;
653 assert(ms->is_MachCallJava(), "");
654 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
655 if (mcj->_method == NULL) {
656 // These runtime calls do not write to Java visible memory
657 // (other than Raw) and so do not require anti-dependence edges.
658 continue;
659 }
660 }
661 // Same for SafePoints: they read/write Raw but only read otherwise.
662 // This is basically a workaround for SafePoints only defining control
663 // instead of control + memory.
664 if (mstore->ideal_Opcode() == Op_SafePoint)
665 continue;
666 } else {
667 // Some raw memory, such as the load of "top" at an allocation,
668 // can be control dependent on the previous safepoint. See
669 // comments in GraphKit::allocate_heap() about control input.
670 // Inserting an anti-dep between such a safepoint and a use
671 // creates a cycle, and will cause a subsequent failure in
672 // local scheduling. (BugId 4919904)
673 // (%%% How can a control input be a safepoint and not a projection??)
674 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
675 continue;
676 }
677 }
678
679 // Identify a block that the current load must be above,
680 // or else observe that 'store' is all the way up in the
681 // earliest legal block for 'load'. In the latter case,
682 // immediately insert an anti-dependence edge.
683 Block* store_block = get_block_for_node(store);
684 assert(store_block != NULL, "unused killing projections skipped above");
685
686 if (store->is_Phi()) {
687 // 'load' uses memory which is one (or more) of the Phi's inputs.
688 // It must be scheduled not before the Phi, but rather before
689 // each of the relevant Phi inputs.
690 //
691 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
692 // we mark each corresponding predecessor block and do a combined
693 // hoisting operation later (raise_LCA_above_marks).
694 //
695 // Do not assert(store_block != early, "Phi merging memory after access")
696 // PhiNode may be at start of block 'early' with backedge to 'early'
697 DEBUG_ONLY(bool found_match = false);
698 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
699 if (store->in(j) == mem) { // Found matching input?
700 DEBUG_ONLY(found_match = true);
701 Block* pred_block = get_block_for_node(store_block->pred(j));
702 if (pred_block != early) {
703 // If any predecessor of the Phi matches the load's "early block",
704 // we do not need a precedence edge between the Phi and 'load'
705 // since the load will be forced into a block preceding the Phi.
706 pred_block->set_raise_LCA_mark(load_index);
707 assert(!LCA_orig->dominates(pred_block) ||
708 early->dominates(pred_block), "early is high enough");
709 must_raise_LCA = true;
710 } else {
711 // anti-dependent upon PHI pinned below 'early', no edge needed
712 LCA = early; // but can not schedule below 'early'
713 }
714 }
715 }
716 assert(found_match, "no worklist bug");
717 #ifdef TRACK_PHI_INPUTS
718 #ifdef ASSERT
719 // This assert asks about correct handling of PhiNodes, which may not
720 // have all input edges directly from 'mem'. See BugId 4621264
721 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
722 // Increment by exactly one even if there are multiple copies of 'mem'
723 // coming into the phi, because we will run this block several times
724 // if there are several copies of 'mem'. (That's how DU iterators work.)
725 phi_inputs.at_put(store->_idx, num_mem_inputs);
726 assert(PhiNode::Input + num_mem_inputs < store->req(),
727 "Expect at least one phi input will not be from original memory state");
728 #endif //ASSERT
729 #endif //TRACK_PHI_INPUTS
730 } else if (store_block != early) {
731 // 'store' is between the current LCA and earliest possible block.
732 // Label its block, and decide later on how to raise the LCA
733 // to include the effect on LCA of this store.
734 // If this store's block gets chosen as the raised LCA, we
735 // will find him on the non_early_stores list and stick him
736 // with a precedence edge.
737 // (But, don't bother if LCA is already raised all the way.)
738 if (LCA != early) {
739 store_block->set_raise_LCA_mark(load_index);
740 must_raise_LCA = true;
741 non_early_stores.push(store);
742 }
743 } else {
744 // Found a possibly-interfering store in the load's 'early' block.
745 // This means 'load' cannot sink at all in the dominator tree.
746 // Add an anti-dep edge, and squeeze 'load' into the highest block.
747 assert(store != load->in(0), "dependence cycle found");
748 if (verify) {
749 assert(store->find_edge(load) != -1, "missing precedence edge");
750 } else {
751 store->add_prec(load); // FYI: anti-dep added here
752 }
753 LCA = early;
754 // This turns off the process of gathering non_early_stores.
755 }
756 }
757 // (Worklist is now empty; all nearby stores have been visited.)
758
759 // Finished if 'load' must be scheduled in its 'early' block.
760 // If we found any stores there, they have already been given
761 // precedence edges.
762 if (LCA == early) return LCA;
763
764 // We get here only if there are no possibly-interfering stores
765 // in the load's 'early' block. Move LCA up above all predecessors
766 // which contain stores we have noted.
767 //
768 // The raised LCA block can be a home to such interfering stores,
769 // but its predecessors must not contain any such stores.
770 //
771 // The raised LCA will be a lower bound for placing the load,
772 // preventing the load from sinking past any block containing
773 // a store that may invalidate the memory state required by 'load'.
774 if (must_raise_LCA)
775 LCA = raise_LCA_above_marks(LCA, load->_idx, early, this);
776 if (LCA == early) return LCA;
777
778 // Insert anti-dependence edges from 'load' to each store
779 // in the non-early LCA block.
780 // Mine the non_early_stores list for such stores.
781 if (LCA->raise_LCA_mark() == load_index) {
782 while (non_early_stores.size() > 0) {
783 Node* store = non_early_stores.pop();
784 Block* store_block = get_block_for_node(store);
785 if (store_block == LCA) {
786 // add anti_dependence from store to load in its own block
787 assert(store != load->in(0), "dependence cycle found");
788 if (verify) {
789 assert(store->find_edge(load) != -1, "missing precedence edge");
790 } else {
791 store->add_prec(load);
792 }
793 } else {
794 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
795 // Any other stores we found must be either inside the new LCA
796 // or else outside the original LCA. In the latter case, they
797 // did not interfere with any use of 'load'.
798 assert(LCA->dominates(store_block)
799 || !LCA_orig->dominates(store_block), "no stray stores");
800 }
801 }
802 }
803
804 // Return the highest block containing stores; any stores
805 // within that block have been given anti-dependence edges.
806 return LCA;
807 }
808
809 // This class is used to iterate backwards over the nodes in the graph.
810
811 class Node_Backward_Iterator {
812
813 private:
814 Node_Backward_Iterator();
815
816 public:
817 // Constructor for the iterator
818 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg);
819
820 // Postincrement operator to iterate over the nodes
821 Node *next();
822
823 private:
824 VectorSet &_visited;
825 Node_Stack &_stack;
826 PhaseCFG &_cfg;
827 };
828
829 // Constructor for the Node_Backward_Iterator
830 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg)
831 : _visited(visited), _stack(stack), _cfg(cfg) {
832 // The stack should contain exactly the root
833 stack.clear();
834 stack.push(root, root->outcnt());
835
836 // Clear the visited bits
837 visited.Clear();
838 }
839
840 // Iterator for the Node_Backward_Iterator
841 Node *Node_Backward_Iterator::next() {
842
843 // If the _stack is empty, then just return NULL: finished.
844 if ( !_stack.size() )
845 return NULL;
846
847 // I visit unvisited not-anti-dependence users first, then anti-dependent
848 // children next. I iterate backwards to support removal of nodes.
849 // The stack holds states consisting of 3 values:
850 // current Def node, flag which indicates 1st/2nd pass, index of current out edge
851 Node *self = (Node*)(((uintptr_t)_stack.node()) & ~1);
852 bool iterate_anti_dep = (((uintptr_t)_stack.node()) & 1);
853 uint idx = MIN2(_stack.index(), self->outcnt()); // Support removal of nodes.
854 _stack.pop();
855
856 // I cycle here when I am entering a deeper level of recursion.
857 // The key variable 'self' was set prior to jumping here.
858 while( 1 ) {
859
860 _visited.set(self->_idx);
861
862 // Now schedule all uses as late as possible.
863 const Node* src = self->is_Proj() ? self->in(0) : self;
864 uint src_rpo = _cfg.get_block_for_node(src)->_rpo;
865
866 // Schedule all nodes in a post-order visit
867 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
868
869 // Scan for unvisited nodes
870 while (idx > 0) {
871 // For all uses, schedule late
872 Node* n = self->raw_out(--idx); // Use
873
874 // Skip already visited children
875 if ( _visited.test(n->_idx) )
876 continue;
877
878 // do not traverse backward control edges
879 Node *use = n->is_Proj() ? n->in(0) : n;
880 uint use_rpo = _cfg.get_block_for_node(use)->_rpo;
881
882 if ( use_rpo < src_rpo )
883 continue;
884
885 // Phi nodes always precede uses in a basic block
886 if ( use_rpo == src_rpo && use->is_Phi() )
887 continue;
888
889 unvisited = n; // Found unvisited
890
891 // Check for possible-anti-dependent
892 // 1st pass: No such nodes, 2nd pass: Only such nodes.
893 if (n->needs_anti_dependence_check() == iterate_anti_dep) {
894 unvisited = n; // Found unvisited
895 break;
896 }
897 }
898
899 // Did I find an unvisited not-anti-dependent Node?
900 if (!unvisited) {
901 if (!iterate_anti_dep) {
902 // 2nd pass: Iterate over nodes which needs_anti_dependence_check.
903 iterate_anti_dep = true;
904 idx = self->outcnt();
905 continue;
906 }
907 break; // All done with children; post-visit 'self'
908 }
909
910 // Visit the unvisited Node. Contains the obvious push to
911 // indicate I'm entering a deeper level of recursion. I push the
912 // old state onto the _stack and set a new state and loop (recurse).
913 _stack.push((Node*)((uintptr_t)self | (uintptr_t)iterate_anti_dep), idx);
914 self = unvisited;
915 iterate_anti_dep = false;
916 idx = self->outcnt();
917 } // End recursion loop
918
919 return self;
920 }
921
922 //------------------------------ComputeLatenciesBackwards----------------------
923 // Compute the latency of all the instructions.
924 void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_Stack &stack) {
925 #ifndef PRODUCT
926 if (trace_opto_pipelining())
927 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
928 #endif
929
930 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
931 Node *n;
932
933 // Walk over all the nodes from last to first
934 while ((n = iter.next())) {
935 // Set the latency for the definitions of this instruction
936 partial_latency_of_defs(n);
937 }
938 } // end ComputeLatenciesBackwards
939
940 //------------------------------partial_latency_of_defs------------------------
941 // Compute the latency impact of this node on all defs. This computes
942 // a number that increases as we approach the beginning of the routine.
943 void PhaseCFG::partial_latency_of_defs(Node *n) {
944 // Set the latency for this instruction
945 #ifndef PRODUCT
946 if (trace_opto_pipelining()) {
947 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
948 dump();
949 }
950 #endif
951
952 if (n->is_Proj()) {
953 n = n->in(0);
954 }
955
956 if (n->is_Root()) {
957 return;
958 }
959
960 uint nlen = n->len();
961 uint use_latency = get_latency_for_node(n);
962 uint use_pre_order = get_block_for_node(n)->_pre_order;
963
964 for (uint j = 0; j < nlen; j++) {
965 Node *def = n->in(j);
966
967 if (!def || def == n) {
968 continue;
969 }
970
971 // Walk backwards thru projections
972 if (def->is_Proj()) {
973 def = def->in(0);
974 }
975
976 #ifndef PRODUCT
977 if (trace_opto_pipelining()) {
978 tty->print("# in(%2d): ", j);
979 def->dump();
980 }
981 #endif
982
983 // If the defining block is not known, assume it is ok
984 Block *def_block = get_block_for_node(def);
985 uint def_pre_order = def_block ? def_block->_pre_order : 0;
986
987 if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) {
988 continue;
989 }
990
991 uint delta_latency = n->latency(j);
992 uint current_latency = delta_latency + use_latency;
993
994 if (get_latency_for_node(def) < current_latency) {
995 set_latency_for_node(def, current_latency);
996 }
997
998 #ifndef PRODUCT
999 if (trace_opto_pipelining()) {
1000 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));
1001 }
1002 #endif
1003 }
1004 }
1005
1006 //------------------------------latency_from_use-------------------------------
1007 // Compute the latency of a specific use
1008 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
1009 // If self-reference, return no latency
1010 if (use == n || use->is_Root()) {
1011 return 0;
1012 }
1013
1014 uint def_pre_order = get_block_for_node(def)->_pre_order;
1015 uint latency = 0;
1016
1017 // If the use is not a projection, then it is simple...
1018 if (!use->is_Proj()) {
1019 #ifndef PRODUCT
1020 if (trace_opto_pipelining()) {
1021 tty->print("# out(): ");
1022 use->dump();
1023 }
1024 #endif
1025
1026 uint use_pre_order = get_block_for_node(use)->_pre_order;
1027
1028 if (use_pre_order < def_pre_order)
1029 return 0;
1030
1031 if (use_pre_order == def_pre_order && use->is_Phi())
1032 return 0;
1033
1034 uint nlen = use->len();
1035 uint nl = get_latency_for_node(use);
1036
1037 for ( uint j=0; j<nlen; j++ ) {
1038 if (use->in(j) == n) {
1039 // Change this if we want local latencies
1040 uint ul = use->latency(j);
1041 uint l = ul + nl;
1042 if (latency < l) latency = l;
1043 #ifndef PRODUCT
1044 if (trace_opto_pipelining()) {
1045 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
1046 nl, j, ul, l, latency);
1047 }
1048 #endif
1049 }
1050 }
1051 } else {
1052 // This is a projection, just grab the latency of the use(s)
1053 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
1054 uint l = latency_from_use(use, def, use->fast_out(j));
1055 if (latency < l) latency = l;
1056 }
1057 }
1058
1059 return latency;
1060 }
1061
1062 //------------------------------latency_from_uses------------------------------
1063 // Compute the latency of this instruction relative to all of it's uses.
1064 // This computes a number that increases as we approach the beginning of the
1065 // routine.
1066 void PhaseCFG::latency_from_uses(Node *n) {
1067 // Set the latency for this instruction
1068 #ifndef PRODUCT
1069 if (trace_opto_pipelining()) {
1070 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1071 dump();
1072 }
1073 #endif
1074 uint latency=0;
1075 const Node *def = n->is_Proj() ? n->in(0): n;
1076
1077 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1078 uint l = latency_from_use(n, def, n->fast_out(i));
1079
1080 if (latency < l) latency = l;
1081 }
1082
1083 set_latency_for_node(n, latency);
1084 }
1085
1086 //------------------------------hoist_to_cheaper_block-------------------------
1087 // Pick a block for node self, between early and LCA, that is a cheaper
1088 // alternative to LCA.
1089 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1090 const double delta = 1+PROB_UNLIKELY_MAG(4);
1091 Block* least = LCA;
1092 double least_freq = least->_freq;
1093 uint target = get_latency_for_node(self);
1094 uint start_latency = get_latency_for_node(LCA->head());
1095 uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx()));
1096 bool in_latency = (target <= start_latency);
1097 const Block* root_block = get_block_for_node(_root);
1098
1099 // Turn off latency scheduling if scheduling is just plain off
1100 if (!C->do_scheduling())
1101 in_latency = true;
1102
1103 // Do not hoist (to cover latency) instructions which target a
1104 // single register. Hoisting stretches the live range of the
1105 // single register and may force spilling.
1106 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1107 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
1108 in_latency = true;
1109
1110 #ifndef PRODUCT
1111 if (trace_opto_pipelining()) {
1112 tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self));
1113 self->dump();
1114 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1115 LCA->_pre_order,
1116 LCA->head()->_idx,
1117 start_latency,
1118 LCA->get_node(LCA->end_idx())->_idx,
1119 end_latency,
1120 least_freq);
1121 }
1122 #endif
1123
1124 int cand_cnt = 0; // number of candidates tried
1125
1126 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1127 // the earliest legal location. Capture the least execution frequency.
1128 while (LCA != early) {
1129 LCA = LCA->_idom; // Follow up the dominator tree
1130
1131 if (LCA == NULL) {
1132 // Bailout without retry
1133 assert(false, "graph should be schedulable");
1134 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1135 return least;
1136 }
1137
1138 // Don't hoist machine instructions to the root basic block
1139 if (mach && LCA == root_block)
1140 break;
1141
1142 uint start_lat = get_latency_for_node(LCA->head());
1143 uint end_idx = LCA->end_idx();
1144 uint end_lat = get_latency_for_node(LCA->get_node(end_idx));
1145 double LCA_freq = LCA->_freq;
1146 #ifndef PRODUCT
1147 if (trace_opto_pipelining()) {
1148 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1149 LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq);
1150 }
1151 #endif
1152 cand_cnt++;
1153 if (LCA_freq < least_freq || // Better Frequency
1154 (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
1155 (!StressGCM && // Otherwise, choose with latency
1156 !in_latency && // No block containing latency
1157 LCA_freq < least_freq * delta && // No worse frequency
1158 target >= end_lat && // within latency range
1159 !self->is_iteratively_computed() ) // But don't hoist IV increments
1160 // because they may end up above other uses of their phi forcing
1161 // their result register to be different from their input.
1162 ) {
1163 least = LCA; // Found cheaper block
1164 least_freq = LCA_freq;
1165 start_latency = start_lat;
1166 end_latency = end_lat;
1167 if (target <= start_lat)
1168 in_latency = true;
1169 }
1170 }
1171
1172 #ifndef PRODUCT
1173 if (trace_opto_pipelining()) {
1174 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1175 least->_pre_order, start_latency, least_freq);
1176 }
1177 #endif
1178
1179 // See if the latency needs to be updated
1180 if (target < end_latency) {
1181 #ifndef PRODUCT
1182 if (trace_opto_pipelining()) {
1183 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1184 }
1185 #endif
1186 set_latency_for_node(self, end_latency);
1187 partial_latency_of_defs(self);
1188 }
1189
1190 return least;
1191 }
1192
1193
1194 //------------------------------schedule_late-----------------------------------
1195 // Now schedule all codes as LATE as possible. This is the LCA in the
1196 // dominator tree of all USES of a value. Pick the block with the least
1197 // loop nesting depth that is lowest in the dominator tree.
1198 extern const char must_clone[];
1199 void PhaseCFG::schedule_late(VectorSet &visited, Node_Stack &stack) {
1200 #ifndef PRODUCT
1201 if (trace_opto_pipelining())
1202 tty->print("\n#---- schedule_late ----\n");
1203 #endif
1204
1205 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1206 Node *self;
1207
1208 // Walk over all the nodes from last to first
1209 while ((self = iter.next())) {
1210 Block* early = get_block_for_node(self); // Earliest legal placement
1211
1212 if (self->is_top()) {
1213 // Top node goes in bb #2 with other constants.
1214 // It must be special-cased, because it has no out edges.
1215 early->add_inst(self);
1216 continue;
1217 }
1218
1219 // No uses, just terminate
1220 if (self->outcnt() == 0) {
1221 assert(self->is_MachProj(), "sanity");
1222 continue; // Must be a dead machine projection
1223 }
1224
1225 // If node is pinned in the block, then no scheduling can be done.
1226 if( self->pinned() ) // Pinned in block?
1227 continue;
1228
1229 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1230 if (mach) {
1231 switch (mach->ideal_Opcode()) {
1232 case Op_CreateEx:
1233 // Don't move exception creation
1234 early->add_inst(self);
1235 continue;
1236 break;
1237 case Op_CheckCastPP: {
1238 // Don't move CheckCastPP nodes away from their input, if the input
1239 // is a rawptr (5071820).
1240 Node *def = self->in(1);
1241 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1242 early->add_inst(self);
1243 #ifdef ASSERT
1244 _raw_oops.push(def);
1245 #endif
1246 continue;
1247 }
1248 break;
1249 }
1250 default:
1251 break;
1252 }
1253 }
1254
1255 // Gather LCA of all uses
1256 Block *LCA = NULL;
1257 {
1258 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1259 // For all uses, find LCA
1260 Node* use = self->fast_out(i);
1261 LCA = raise_LCA_above_use(LCA, use, self, this);
1262 }
1263 } // (Hide defs of imax, i from rest of block.)
1264
1265 // Place temps in the block of their use. This isn't a
1266 // requirement for correctness but it reduces useless
1267 // interference between temps and other nodes.
1268 if (mach != NULL && mach->is_MachTemp()) {
1269 map_node_to_block(self, LCA);
1270 LCA->add_inst(self);
1271 continue;
1272 }
1273
1274 // Check if 'self' could be anti-dependent on memory
1275 if (self->needs_anti_dependence_check()) {
1276 // Hoist LCA above possible-defs and insert anti-dependences to
1277 // defs in new LCA block.
1278 LCA = insert_anti_dependences(LCA, self);
1279 }
1280
1281 if (early->_dom_depth > LCA->_dom_depth) {
1282 // Somehow the LCA has moved above the earliest legal point.
1283 // (One way this can happen is via memory_early_block.)
1284 if (C->subsume_loads() == true && !C->failing()) {
1285 // Retry with subsume_loads == false
1286 // If this is the first failure, the sentinel string will "stick"
1287 // to the Compile object, and the C2Compiler will see it and retry.
1288 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1289 } else {
1290 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1291 assert(false, "graph should be schedulable");
1292 C->record_method_not_compilable("late schedule failed: incorrect graph");
1293 }
1294 return;
1295 }
1296
1297 // If there is no opportunity to hoist, then we're done.
1298 // In stress mode, try to hoist even the single operations.
1299 bool try_to_hoist = StressGCM || (LCA != early);
1300
1301 // Must clone guys stay next to use; no hoisting allowed.
1302 // Also cannot hoist guys that alter memory or are otherwise not
1303 // allocatable (hoisting can make a value live longer, leading to
1304 // anti and output dependency problems which are normally resolved
1305 // by the register allocator giving everyone a different register).
1306 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1307 try_to_hoist = false;
1308
1309 Block* late = NULL;
1310 if (try_to_hoist) {
1311 // Now find the block with the least execution frequency.
1312 // Start at the latest schedule and work up to the earliest schedule
1313 // in the dominator tree. Thus the Node will dominate all its uses.
1314 late = hoist_to_cheaper_block(LCA, early, self);
1315 } else {
1316 // Just use the LCA of the uses.
1317 late = LCA;
1318 }
1319
1320 // Put the node into target block
1321 schedule_node_into_block(self, late);
1322
1323 #ifdef ASSERT
1324 if (self->needs_anti_dependence_check()) {
1325 // since precedence edges are only inserted when we're sure they
1326 // are needed make sure that after placement in a block we don't
1327 // need any new precedence edges.
1328 verify_anti_dependences(late, self);
1329 }
1330 #endif
1331 } // Loop until all nodes have been visited
1332
1333 } // end ScheduleLate
1334
1335 //------------------------------GlobalCodeMotion-------------------------------
1336 void PhaseCFG::global_code_motion() {
1337 ResourceMark rm;
1338
1339 #ifndef PRODUCT
1340 if (trace_opto_pipelining()) {
1341 tty->print("\n---- Start GlobalCodeMotion ----\n");
1342 }
1343 #endif
1344
1345 // Initialize the node to block mapping for things on the proj_list
1346 for (uint i = 0; i < _matcher.number_of_projections(); i++) {
1347 unmap_node_from_block(_matcher.get_projection(i));
1348 }
1349
1350 // Set the basic block for Nodes pinned into blocks
1351 Arena* arena = Thread::current()->resource_area();
1352 VectorSet visited(arena);
1353 schedule_pinned_nodes(visited);
1354
1355 // Find the earliest Block any instruction can be placed in. Some
1356 // instructions are pinned into Blocks. Unpinned instructions can
1357 // appear in last block in which all their inputs occur.
1358 visited.Clear();
1359 Node_Stack stack(arena, (C->live_nodes() >> 2) + 16); // pre-grow
1360 if (!schedule_early(visited, stack)) {
1361 // Bailout without retry
1362 C->record_method_not_compilable("early schedule failed");
1363 return;
1364 }
1365
1366 // Build Def-Use edges.
1367 // Compute the latency information (via backwards walk) for all the
1368 // instructions in the graph
1369 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1370
1371 if (C->do_scheduling()) {
1372 compute_latencies_backwards(visited, stack);
1373 }
1374
1375 // Now schedule all codes as LATE as possible. This is the LCA in the
1376 // dominator tree of all USES of a value. Pick the block with the least
1377 // loop nesting depth that is lowest in the dominator tree.
1378 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1379 schedule_late(visited, stack);
1380 if (C->failing()) {
1381 // schedule_late fails only when graph is incorrect.
1382 assert(!VerifyGraphEdges, "verification should have failed");
1383 return;
1384 }
1385
1386 #ifndef PRODUCT
1387 if (trace_opto_pipelining()) {
1388 tty->print("\n---- Detect implicit null checks ----\n");
1389 }
1390 #endif
1391
1392 // Detect implicit-null-check opportunities. Basically, find NULL checks
1393 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1394 // I can generate a memory op if there is not one nearby.
1395 if (C->is_method_compilation()) {
1396 // By reversing the loop direction we get a very minor gain on mpegaudio.
1397 // Feel free to revert to a forward loop for clarity.
1398 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1399 for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) {
1400 Node* proj = _matcher._null_check_tests[i];
1401 Node* val = _matcher._null_check_tests[i + 1];
1402 Block* block = get_block_for_node(proj);
1403 implicit_null_check(block, proj, val, C->allowed_deopt_reasons());
1404 // The implicit_null_check will only perform the transformation
1405 // if the null branch is truly uncommon, *and* it leads to an
1406 // uncommon trap. Combined with the too_many_traps guards
1407 // above, this prevents SEGV storms reported in 6366351,
1408 // by recompiling offending methods without this optimization.
1409 }
1410 }
1411
1412 bool block_size_threshold_ok = false;
1413 intptr_t *recalc_pressure_nodes = NULL;
1414 if (OptoRegScheduling) {
1415 for (uint i = 0; i < number_of_blocks(); i++) {
1416 Block* block = get_block(i);
1417 if (block->number_of_nodes() > 10) {
1418 block_size_threshold_ok = true;
1419 break;
1420 }
1421 }
1422 }
1423
1424 // Enabling the scheduler for register pressure plus finding blocks of size to schedule for it
1425 // is key to enabling this feature.
1426 PhaseChaitin regalloc(C->unique(), *this, _matcher, true);
1427 ResourceArea live_arena(mtCompiler); // Arena for liveness
1428 ResourceMark rm_live(&live_arena);
1429 PhaseLive live(*this, regalloc._lrg_map.names(), &live_arena, true);
1430 PhaseIFG ifg(&live_arena);
1431 if (OptoRegScheduling && block_size_threshold_ok) {
1432 regalloc.mark_ssa();
1433 Compile::TracePhase tp("computeLive", &timers[_t_computeLive]);
1434 rm_live.reset_to_mark(); // Reclaim working storage
1435 IndexSet::reset_memory(C, &live_arena);
1436 uint node_size = regalloc._lrg_map.max_lrg_id();
1437 ifg.init(node_size); // Empty IFG
1438 regalloc.set_ifg(ifg);
1439 regalloc.set_live(live);
1440 regalloc.gather_lrg_masks(false); // Collect LRG masks
1441 live.compute(node_size); // Compute liveness
1442
1443 recalc_pressure_nodes = NEW_RESOURCE_ARRAY(intptr_t, node_size);
1444 for (uint i = 0; i < node_size; i++) {
1445 recalc_pressure_nodes[i] = 0;
1446 }
1447 }
1448 _regalloc = ®alloc;
1449
1450 #ifndef PRODUCT
1451 if (trace_opto_pipelining()) {
1452 tty->print("\n---- Start Local Scheduling ----\n");
1453 }
1454 #endif
1455
1456 // Schedule locally. Right now a simple topological sort.
1457 // Later, do a real latency aware scheduler.
1458 GrowableArray<int> ready_cnt(C->unique(), C->unique(), -1);
1459 visited.Clear();
1460 for (uint i = 0; i < number_of_blocks(); i++) {
1461 Block* block = get_block(i);
1462 if (!schedule_local(block, ready_cnt, visited, recalc_pressure_nodes)) {
1463 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1464 C->record_method_not_compilable("local schedule failed");
1465 }
1466 _regalloc = NULL;
1467 return;
1468 }
1469 }
1470 _regalloc = NULL;
1471
1472 // If we inserted any instructions between a Call and his CatchNode,
1473 // clone the instructions on all paths below the Catch.
1474 for (uint i = 0; i < number_of_blocks(); i++) {
1475 Block* block = get_block(i);
1476 call_catch_cleanup(block);
1477 }
1478
1479 #ifndef PRODUCT
1480 if (trace_opto_pipelining()) {
1481 tty->print("\n---- After GlobalCodeMotion ----\n");
1482 for (uint i = 0; i < number_of_blocks(); i++) {
1483 Block* block = get_block(i);
1484 block->dump();
1485 }
1486 }
1487 #endif
1488 // Dead.
1489 _node_latency = (GrowableArray<uint> *)0xdeadbeef;
1490 }
1491
1492 bool PhaseCFG::do_global_code_motion() {
1493
1494 build_dominator_tree();
1495 if (C->failing()) {
1496 return false;
1497 }
1498
1499 NOT_PRODUCT( C->verify_graph_edges(); )
1500
1501 estimate_block_frequency();
1502
1503 global_code_motion();
1504
1505 if (C->failing()) {
1506 return false;
1507 }
1508
1509 return true;
1510 }
1511
1512 //------------------------------Estimate_Block_Frequency-----------------------
1513 // Estimate block frequencies based on IfNode probabilities.
1514 void PhaseCFG::estimate_block_frequency() {
1515
1516 // Force conditional branches leading to uncommon traps to be unlikely,
1517 // not because we get to the uncommon_trap with less relative frequency,
1518 // but because an uncommon_trap typically causes a deopt, so we only get
1519 // there once.
1520 if (C->do_freq_based_layout()) {
1521 Block_List worklist;
1522 Block* root_blk = get_block(0);
1523 for (uint i = 1; i < root_blk->num_preds(); i++) {
1524 Block *pb = get_block_for_node(root_blk->pred(i));
1525 if (pb->has_uncommon_code()) {
1526 worklist.push(pb);
1527 }
1528 }
1529 while (worklist.size() > 0) {
1530 Block* uct = worklist.pop();
1531 if (uct == get_root_block()) {
1532 continue;
1533 }
1534 for (uint i = 1; i < uct->num_preds(); i++) {
1535 Block *pb = get_block_for_node(uct->pred(i));
1536 if (pb->_num_succs == 1) {
1537 worklist.push(pb);
1538 } else if (pb->num_fall_throughs() == 2) {
1539 pb->update_uncommon_branch(uct);
1540 }
1541 }
1542 }
1543 }
1544
1545 // Create the loop tree and calculate loop depth.
1546 _root_loop = create_loop_tree();
1547 _root_loop->compute_loop_depth(0);
1548
1549 // Compute block frequency of each block, relative to a single loop entry.
1550 _root_loop->compute_freq();
1551
1552 // Adjust all frequencies to be relative to a single method entry
1553 _root_loop->_freq = 1.0;
1554 _root_loop->scale_freq();
1555
1556 // Save outmost loop frequency for LRG frequency threshold
1557 _outer_loop_frequency = _root_loop->outer_loop_freq();
1558
1559 // force paths ending at uncommon traps to be infrequent
1560 if (!C->do_freq_based_layout()) {
1561 Block_List worklist;
1562 Block* root_blk = get_block(0);
1563 for (uint i = 1; i < root_blk->num_preds(); i++) {
1564 Block *pb = get_block_for_node(root_blk->pred(i));
1565 if (pb->has_uncommon_code()) {
1566 worklist.push(pb);
1567 }
1568 }
1569 while (worklist.size() > 0) {
1570 Block* uct = worklist.pop();
1571 uct->_freq = PROB_MIN;
1572 for (uint i = 1; i < uct->num_preds(); i++) {
1573 Block *pb = get_block_for_node(uct->pred(i));
1574 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1575 worklist.push(pb);
1576 }
1577 }
1578 }
1579 }
1580
1581 #ifdef ASSERT
1582 for (uint i = 0; i < number_of_blocks(); i++) {
1583 Block* b = get_block(i);
1584 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
1585 }
1586 #endif
1587
1588 #ifndef PRODUCT
1589 if (PrintCFGBlockFreq) {
1590 tty->print_cr("CFG Block Frequencies");
1591 _root_loop->dump_tree();
1592 if (Verbose) {
1593 tty->print_cr("PhaseCFG dump");
1594 dump();
1595 tty->print_cr("Node dump");
1596 _root->dump(99999);
1597 }
1598 }
1599 #endif
1600 }
1601
1602 //----------------------------create_loop_tree--------------------------------
1603 // Create a loop tree from the CFG
1604 CFGLoop* PhaseCFG::create_loop_tree() {
1605
1606 #ifdef ASSERT
1607 assert(get_block(0) == get_root_block(), "first block should be root block");
1608 for (uint i = 0; i < number_of_blocks(); i++) {
1609 Block* block = get_block(i);
1610 // Check that _loop field are clear...we could clear them if not.
1611 assert(block->_loop == NULL, "clear _loop expected");
1612 // Sanity check that the RPO numbering is reflected in the _blocks array.
1613 // It doesn't have to be for the loop tree to be built, but if it is not,
1614 // then the blocks have been reordered since dom graph building...which
1615 // may question the RPO numbering
1616 assert(block->_rpo == i, "unexpected reverse post order number");
1617 }
1618 #endif
1619
1620 int idct = 0;
1621 CFGLoop* root_loop = new CFGLoop(idct++);
1622
1623 Block_List worklist;
1624
1625 // Assign blocks to loops
1626 for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block
1627 Block* block = get_block(i);
1628
1629 if (block->head()->is_Loop()) {
1630 Block* loop_head = block;
1631 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1632 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1633 Block* tail = get_block_for_node(tail_n);
1634
1635 // Defensively filter out Loop nodes for non-single-entry loops.
1636 // For all reasonable loops, the head occurs before the tail in RPO.
1637 if (i <= tail->_rpo) {
1638
1639 // The tail and (recursive) predecessors of the tail
1640 // are made members of a new loop.
1641
1642 assert(worklist.size() == 0, "nonempty worklist");
1643 CFGLoop* nloop = new CFGLoop(idct++);
1644 assert(loop_head->_loop == NULL, "just checking");
1645 loop_head->_loop = nloop;
1646 // Add to nloop so push_pred() will skip over inner loops
1647 nloop->add_member(loop_head);
1648 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this);
1649
1650 while (worklist.size() > 0) {
1651 Block* member = worklist.pop();
1652 if (member != loop_head) {
1653 for (uint j = 1; j < member->num_preds(); j++) {
1654 nloop->push_pred(member, j, worklist, this);
1655 }
1656 }
1657 }
1658 }
1659 }
1660 }
1661
1662 // Create a member list for each loop consisting
1663 // of both blocks and (immediate child) loops.
1664 for (uint i = 0; i < number_of_blocks(); i++) {
1665 Block* block = get_block(i);
1666 CFGLoop* lp = block->_loop;
1667 if (lp == NULL) {
1668 // Not assigned to a loop. Add it to the method's pseudo loop.
1669 block->_loop = root_loop;
1670 lp = root_loop;
1671 }
1672 if (lp == root_loop || block != lp->head()) { // loop heads are already members
1673 lp->add_member(block);
1674 }
1675 if (lp != root_loop) {
1676 if (lp->parent() == NULL) {
1677 // Not a nested loop. Make it a child of the method's pseudo loop.
1678 root_loop->add_nested_loop(lp);
1679 }
1680 if (block == lp->head()) {
1681 // Add nested loop to member list of parent loop.
1682 lp->parent()->add_member(lp);
1683 }
1684 }
1685 }
1686
1687 return root_loop;
1688 }
1689
1690 //------------------------------push_pred--------------------------------------
1691 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) {
1692 Node* pred_n = blk->pred(i);
1693 Block* pred = cfg->get_block_for_node(pred_n);
1694 CFGLoop *pred_loop = pred->_loop;
1695 if (pred_loop == NULL) {
1696 // Filter out blocks for non-single-entry loops.
1697 // For all reasonable loops, the head occurs before the tail in RPO.
1698 if (pred->_rpo > head()->_rpo) {
1699 pred->_loop = this;
1700 worklist.push(pred);
1701 }
1702 } else if (pred_loop != this) {
1703 // Nested loop.
1704 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1705 pred_loop = pred_loop->_parent;
1706 }
1707 // Make pred's loop be a child
1708 if (pred_loop->_parent == NULL) {
1709 add_nested_loop(pred_loop);
1710 // Continue with loop entry predecessor.
1711 Block* pred_head = pred_loop->head();
1712 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1713 assert(pred_head != head(), "loop head in only one loop");
1714 push_pred(pred_head, LoopNode::EntryControl, worklist, cfg);
1715 } else {
1716 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1717 }
1718 }
1719 }
1720
1721 //------------------------------add_nested_loop--------------------------------
1722 // Make cl a child of the current loop in the loop tree.
1723 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1724 assert(_parent == NULL, "no parent yet");
1725 assert(cl != this, "not my own parent");
1726 cl->_parent = this;
1727 CFGLoop* ch = _child;
1728 if (ch == NULL) {
1729 _child = cl;
1730 } else {
1731 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1732 ch->_sibling = cl;
1733 }
1734 }
1735
1736 //------------------------------compute_loop_depth-----------------------------
1737 // Store the loop depth in each CFGLoop object.
1738 // Recursively walk the children to do the same for them.
1739 void CFGLoop::compute_loop_depth(int depth) {
1740 _depth = depth;
1741 CFGLoop* ch = _child;
1742 while (ch != NULL) {
1743 ch->compute_loop_depth(depth + 1);
1744 ch = ch->_sibling;
1745 }
1746 }
1747
1748 //------------------------------compute_freq-----------------------------------
1749 // Compute the frequency of each block and loop, relative to a single entry
1750 // into the dominating loop head.
1751 void CFGLoop::compute_freq() {
1752 // Bottom up traversal of loop tree (visit inner loops first.)
1753 // Set loop head frequency to 1.0, then transitively
1754 // compute frequency for all successors in the loop,
1755 // as well as for each exit edge. Inner loops are
1756 // treated as single blocks with loop exit targets
1757 // as the successor blocks.
1758
1759 // Nested loops first
1760 CFGLoop* ch = _child;
1761 while (ch != NULL) {
1762 ch->compute_freq();
1763 ch = ch->_sibling;
1764 }
1765 assert (_members.length() > 0, "no empty loops");
1766 Block* hd = head();
1767 hd->_freq = 1.0;
1768 for (int i = 0; i < _members.length(); i++) {
1769 CFGElement* s = _members.at(i);
1770 double freq = s->_freq;
1771 if (s->is_block()) {
1772 Block* b = s->as_Block();
1773 for (uint j = 0; j < b->_num_succs; j++) {
1774 Block* sb = b->_succs[j];
1775 update_succ_freq(sb, freq * b->succ_prob(j));
1776 }
1777 } else {
1778 CFGLoop* lp = s->as_CFGLoop();
1779 assert(lp->_parent == this, "immediate child");
1780 for (int k = 0; k < lp->_exits.length(); k++) {
1781 Block* eb = lp->_exits.at(k).get_target();
1782 double prob = lp->_exits.at(k).get_prob();
1783 update_succ_freq(eb, freq * prob);
1784 }
1785 }
1786 }
1787
1788 // For all loops other than the outer, "method" loop,
1789 // sum and normalize the exit probability. The "method" loop
1790 // should keep the initial exit probability of 1, so that
1791 // inner blocks do not get erroneously scaled.
1792 if (_depth != 0) {
1793 // Total the exit probabilities for this loop.
1794 double exits_sum = 0.0f;
1795 for (int i = 0; i < _exits.length(); i++) {
1796 exits_sum += _exits.at(i).get_prob();
1797 }
1798
1799 // Normalize the exit probabilities. Until now, the
1800 // probabilities estimate the possibility of exit per
1801 // a single loop iteration; afterward, they estimate
1802 // the probability of exit per loop entry.
1803 for (int i = 0; i < _exits.length(); i++) {
1804 Block* et = _exits.at(i).get_target();
1805 float new_prob = 0.0f;
1806 if (_exits.at(i).get_prob() > 0.0f) {
1807 new_prob = _exits.at(i).get_prob() / exits_sum;
1808 }
1809 BlockProbPair bpp(et, new_prob);
1810 _exits.at_put(i, bpp);
1811 }
1812
1813 // Save the total, but guard against unreasonable probability,
1814 // as the value is used to estimate the loop trip count.
1815 // An infinite trip count would blur relative block
1816 // frequencies.
1817 if (exits_sum > 1.0f) exits_sum = 1.0;
1818 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1819 _exit_prob = exits_sum;
1820 }
1821 }
1822
1823 //------------------------------succ_prob-------------------------------------
1824 // Determine the probability of reaching successor 'i' from the receiver block.
1825 float Block::succ_prob(uint i) {
1826 int eidx = end_idx();
1827 Node *n = get_node(eidx); // Get ending Node
1828
1829 int op = n->Opcode();
1830 if (n->is_Mach()) {
1831 if (n->is_MachNullCheck()) {
1832 // Can only reach here if called after lcm. The original Op_If is gone,
1833 // so we attempt to infer the probability from one or both of the
1834 // successor blocks.
1835 assert(_num_succs == 2, "expecting 2 successors of a null check");
1836 // If either successor has only one predecessor, then the
1837 // probability estimate can be derived using the
1838 // relative frequency of the successor and this block.
1839 if (_succs[i]->num_preds() == 2) {
1840 return _succs[i]->_freq / _freq;
1841 } else if (_succs[1-i]->num_preds() == 2) {
1842 return 1 - (_succs[1-i]->_freq / _freq);
1843 } else {
1844 // Estimate using both successor frequencies
1845 float freq = _succs[i]->_freq;
1846 return freq / (freq + _succs[1-i]->_freq);
1847 }
1848 }
1849 op = n->as_Mach()->ideal_Opcode();
1850 }
1851
1852
1853 // Switch on branch type
1854 switch( op ) {
1855 case Op_CountedLoopEnd:
1856 case Op_If: {
1857 assert (i < 2, "just checking");
1858 // Conditionals pass on only part of their frequency
1859 float prob = n->as_MachIf()->_prob;
1860 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1861 // If succ[i] is the FALSE branch, invert path info
1862 if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) {
1863 return 1.0f - prob; // not taken
1864 } else {
1865 return prob; // taken
1866 }
1867 }
1868
1869 case Op_Jump:
1870 // Divide the frequency between all successors evenly
1871 return 1.0f/_num_succs;
1872
1873 case Op_Catch: {
1874 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1875 if (ci->_con == CatchProjNode::fall_through_index) {
1876 // Fall-thru path gets the lion's share.
1877 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1878 } else {
1879 // Presume exceptional paths are equally unlikely
1880 return PROB_UNLIKELY_MAG(5);
1881 }
1882 }
1883
1884 case Op_Root:
1885 case Op_Goto:
1886 // Pass frequency straight thru to target
1887 return 1.0f;
1888
1889 case Op_NeverBranch:
1890 return 0.0f;
1891
1892 case Op_TailCall:
1893 case Op_TailJump:
1894 case Op_Return:
1895 case Op_Halt:
1896 case Op_Rethrow:
1897 // Do not push out freq to root block
1898 return 0.0f;
1899
1900 default:
1901 ShouldNotReachHere();
1902 }
1903
1904 return 0.0f;
1905 }
1906
1907 //------------------------------num_fall_throughs-----------------------------
1908 // Return the number of fall-through candidates for a block
1909 int Block::num_fall_throughs() {
1910 int eidx = end_idx();
1911 Node *n = get_node(eidx); // Get ending Node
1912
1913 int op = n->Opcode();
1914 if (n->is_Mach()) {
1915 if (n->is_MachNullCheck()) {
1916 // In theory, either side can fall-thru, for simplicity sake,
1917 // let's say only the false branch can now.
1918 return 1;
1919 }
1920 op = n->as_Mach()->ideal_Opcode();
1921 }
1922
1923 // Switch on branch type
1924 switch( op ) {
1925 case Op_CountedLoopEnd:
1926 case Op_If:
1927 return 2;
1928
1929 case Op_Root:
1930 case Op_Goto:
1931 return 1;
1932
1933 case Op_Catch: {
1934 for (uint i = 0; i < _num_succs; i++) {
1935 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1936 if (ci->_con == CatchProjNode::fall_through_index) {
1937 return 1;
1938 }
1939 }
1940 return 0;
1941 }
1942
1943 case Op_Jump:
1944 case Op_NeverBranch:
1945 case Op_TailCall:
1946 case Op_TailJump:
1947 case Op_Return:
1948 case Op_Halt:
1949 case Op_Rethrow:
1950 return 0;
1951
1952 default:
1953 ShouldNotReachHere();
1954 }
1955
1956 return 0;
1957 }
1958
1959 //------------------------------succ_fall_through-----------------------------
1960 // Return true if a specific successor could be fall-through target.
1961 bool Block::succ_fall_through(uint i) {
1962 int eidx = end_idx();
1963 Node *n = get_node(eidx); // Get ending Node
1964
1965 int op = n->Opcode();
1966 if (n->is_Mach()) {
1967 if (n->is_MachNullCheck()) {
1968 // In theory, either side can fall-thru, for simplicity sake,
1969 // let's say only the false branch can now.
1970 return get_node(i + eidx + 1)->Opcode() == Op_IfFalse;
1971 }
1972 op = n->as_Mach()->ideal_Opcode();
1973 }
1974
1975 // Switch on branch type
1976 switch( op ) {
1977 case Op_CountedLoopEnd:
1978 case Op_If:
1979 case Op_Root:
1980 case Op_Goto:
1981 return true;
1982
1983 case Op_Catch: {
1984 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1985 return ci->_con == CatchProjNode::fall_through_index;
1986 }
1987
1988 case Op_Jump:
1989 case Op_NeverBranch:
1990 case Op_TailCall:
1991 case Op_TailJump:
1992 case Op_Return:
1993 case Op_Halt:
1994 case Op_Rethrow:
1995 return false;
1996
1997 default:
1998 ShouldNotReachHere();
1999 }
2000
2001 return false;
2002 }
2003
2004 //------------------------------update_uncommon_branch------------------------
2005 // Update the probability of a two-branch to be uncommon
2006 void Block::update_uncommon_branch(Block* ub) {
2007 int eidx = end_idx();
2008 Node *n = get_node(eidx); // Get ending Node
2009
2010 int op = n->as_Mach()->ideal_Opcode();
2011
2012 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
2013 assert(num_fall_throughs() == 2, "must be a two way branch block");
2014
2015 // Which successor is ub?
2016 uint s;
2017 for (s = 0; s <_num_succs; s++) {
2018 if (_succs[s] == ub) break;
2019 }
2020 assert(s < 2, "uncommon successor must be found");
2021
2022 // If ub is the true path, make the proability small, else
2023 // ub is the false path, and make the probability large
2024 bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse);
2025
2026 // Get existing probability
2027 float p = n->as_MachIf()->_prob;
2028
2029 if (invert) p = 1.0 - p;
2030 if (p > PROB_MIN) {
2031 p = PROB_MIN;
2032 }
2033 if (invert) p = 1.0 - p;
2034
2035 n->as_MachIf()->_prob = p;
2036 }
2037
2038 //------------------------------update_succ_freq-------------------------------
2039 // Update the appropriate frequency associated with block 'b', a successor of
2040 // a block in this loop.
2041 void CFGLoop::update_succ_freq(Block* b, double freq) {
2042 if (b->_loop == this) {
2043 if (b == head()) {
2044 // back branch within the loop
2045 // Do nothing now, the loop carried frequency will be
2046 // adjust later in scale_freq().
2047 } else {
2048 // simple branch within the loop
2049 b->_freq += freq;
2050 }
2051 } else if (!in_loop_nest(b)) {
2052 // branch is exit from this loop
2053 BlockProbPair bpp(b, freq);
2054 _exits.append(bpp);
2055 } else {
2056 // branch into nested loop
2057 CFGLoop* ch = b->_loop;
2058 ch->_freq += freq;
2059 }
2060 }
2061
2062 //------------------------------in_loop_nest-----------------------------------
2063 // Determine if block b is in the receiver's loop nest.
2064 bool CFGLoop::in_loop_nest(Block* b) {
2065 int depth = _depth;
2066 CFGLoop* b_loop = b->_loop;
2067 int b_depth = b_loop->_depth;
2068 if (depth == b_depth) {
2069 return true;
2070 }
2071 while (b_depth > depth) {
2072 b_loop = b_loop->_parent;
2073 b_depth = b_loop->_depth;
2074 }
2075 return b_loop == this;
2076 }
2077
2078 //------------------------------scale_freq-------------------------------------
2079 // Scale frequency of loops and blocks by trip counts from outer loops
2080 // Do a top down traversal of loop tree (visit outer loops first.)
2081 void CFGLoop::scale_freq() {
2082 double loop_freq = _freq * trip_count();
2083 _freq = loop_freq;
2084 for (int i = 0; i < _members.length(); i++) {
2085 CFGElement* s = _members.at(i);
2086 double block_freq = s->_freq * loop_freq;
2087 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
2088 block_freq = MIN_BLOCK_FREQUENCY;
2089 s->_freq = block_freq;
2090 }
2091 CFGLoop* ch = _child;
2092 while (ch != NULL) {
2093 ch->scale_freq();
2094 ch = ch->_sibling;
2095 }
2096 }
2097
2098 // Frequency of outer loop
2099 double CFGLoop::outer_loop_freq() const {
2100 if (_child != NULL) {
2101 return _child->_freq;
2102 }
2103 return _freq;
2104 }
2105
2106 #ifndef PRODUCT
2107 //------------------------------dump_tree--------------------------------------
2108 void CFGLoop::dump_tree() const {
2109 dump();
2110 if (_child != NULL) _child->dump_tree();
2111 if (_sibling != NULL) _sibling->dump_tree();
2112 }
2113
2114 //------------------------------dump-------------------------------------------
2115 void CFGLoop::dump() const {
2116 for (int i = 0; i < _depth; i++) tty->print(" ");
2117 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
2118 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
2119 for (int i = 0; i < _depth; i++) tty->print(" ");
2120 tty->print(" members:");
2121 int k = 0;
2122 for (int i = 0; i < _members.length(); i++) {
2123 if (k++ >= 6) {
2124 tty->print("\n ");
2125 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2126 k = 0;
2127 }
2128 CFGElement *s = _members.at(i);
2129 if (s->is_block()) {
2130 Block *b = s->as_Block();
2131 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
2132 } else {
2133 CFGLoop* lp = s->as_CFGLoop();
2134 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
2135 }
2136 }
2137 tty->print("\n");
2138 for (int i = 0; i < _depth; i++) tty->print(" ");
2139 tty->print(" exits: ");
2140 k = 0;
2141 for (int i = 0; i < _exits.length(); i++) {
2142 if (k++ >= 7) {
2143 tty->print("\n ");
2144 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2145 k = 0;
2146 }
2147 Block *blk = _exits.at(i).get_target();
2148 double prob = _exits.at(i).get_prob();
2149 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2150 }
2151 tty->print("\n");
2152 }
2153 #endif