1 /*
2 * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "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 return false;
301 }
302 // Save parent node and next input's index.
303 nstack.push(parent_node, input_index);
304 // Process current input now.
305 parent_node = in;
306 input_index = 0;
307 // Not all n's inputs processed.
308 done = false;
309 break;
310 } else if (!is_visited) {
311 // Visit this guy later, using worklist
312 roots.push(in, 0);
313 }
314 }
315
316 if (done) {
317 // All of n's inputs have been processed, complete post-processing.
318
319 // Some instructions are pinned into a block. These include Region,
320 // Phi, Start, Return, and other control-dependent instructions and
321 // any projections which depend on them.
322 if (!parent_node->pinned()) {
323 // Set earliest legal block.
324 Block* earliest_block = find_deepest_input(parent_node, this);
325 map_node_to_block(parent_node, earliest_block);
326 } else {
327 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");
328 }
329
330 if (nstack.is_empty()) {
331 // Finished all nodes on stack.
332 // Process next node on the worklist 'roots'.
333 break;
334 }
335 // Get saved parent node and next input's index.
336 parent_node = nstack.node();
337 input_index = nstack.index();
338 nstack.pop();
339 }
340 }
341 }
342 return true;
343 }
344
345 //------------------------------dom_lca----------------------------------------
346 // Find least common ancestor in dominator tree
347 // LCA is a current notion of LCA, to be raised above 'this'.
348 // As a convenient boundary condition, return 'this' if LCA is NULL.
349 // Find the LCA of those two nodes.
350 Block* Block::dom_lca(Block* LCA) {
351 if (LCA == NULL || LCA == this) return this;
352
353 Block* anc = this;
354 while (anc->_dom_depth > LCA->_dom_depth)
355 anc = anc->_idom; // Walk up till anc is as high as LCA
356
357 while (LCA->_dom_depth > anc->_dom_depth)
358 LCA = LCA->_idom; // Walk up till LCA is as high as anc
359
360 while (LCA != anc) { // Walk both up till they are the same
361 LCA = LCA->_idom;
362 anc = anc->_idom;
363 }
364
365 return LCA;
366 }
367
368 //--------------------------raise_LCA_above_use--------------------------------
369 // We are placing a definition, and have been given a def->use edge.
370 // The definition must dominate the use, so move the LCA upward in the
371 // dominator tree to dominate the use. If the use is a phi, adjust
372 // the LCA only with the phi input paths which actually use this def.
373 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) {
374 Block* buse = cfg->get_block_for_node(use);
375 if (buse == NULL) return LCA; // Unused killing Projs have no use block
376 if (!use->is_Phi()) return buse->dom_lca(LCA);
377 uint pmax = use->req(); // Number of Phi inputs
378 // Why does not this loop just break after finding the matching input to
379 // the Phi? Well...it's like this. I do not have true def-use/use-def
380 // chains. Means I cannot distinguish, from the def-use direction, which
381 // of many use-defs lead from the same use to the same def. That is, this
382 // Phi might have several uses of the same def. Each use appears in a
383 // different predecessor block. But when I enter here, I cannot distinguish
384 // which use-def edge I should find the predecessor block for. So I find
385 // them all. Means I do a little extra work if a Phi uses the same value
386 // more than once.
387 for (uint j=1; j<pmax; j++) { // For all inputs
388 if (use->in(j) == def) { // Found matching input?
389 Block* pred = cfg->get_block_for_node(buse->pred(j));
390 LCA = pred->dom_lca(LCA);
391 }
392 }
393 return LCA;
394 }
395
396 //----------------------------raise_LCA_above_marks----------------------------
397 // Return a new LCA that dominates LCA and any of its marked predecessors.
398 // Search all my parents up to 'early' (exclusive), looking for predecessors
399 // which are marked with the given index. Return the LCA (in the dom tree)
400 // of all marked blocks. If there are none marked, return the original
401 // LCA.
402 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) {
403 Block_List worklist;
404 worklist.push(LCA);
405 while (worklist.size() > 0) {
406 Block* mid = worklist.pop();
407 if (mid == early) continue; // stop searching here
408
409 // Test and set the visited bit.
410 if (mid->raise_LCA_visited() == mark) continue; // already visited
411
412 // Don't process the current LCA, otherwise the search may terminate early
413 if (mid != LCA && mid->raise_LCA_mark() == mark) {
414 // Raise the LCA.
415 LCA = mid->dom_lca(LCA);
416 if (LCA == early) break; // stop searching everywhere
417 assert(early->dominates(LCA), "early is high enough");
418 // Resume searching at that point, skipping intermediate levels.
419 worklist.push(LCA);
420 if (LCA == mid)
421 continue; // Don't mark as visited to avoid early termination.
422 } else {
423 // Keep searching through this block's predecessors.
424 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
425 Block* mid_parent = cfg->get_block_for_node(mid->pred(j));
426 worklist.push(mid_parent);
427 }
428 }
429 mid->set_raise_LCA_visited(mark);
430 }
431 return LCA;
432 }
433
434 //--------------------------memory_early_block--------------------------------
435 // This is a variation of find_deepest_input, the heart of schedule_early.
436 // Find the "early" block for a load, if we considered only memory and
437 // address inputs, that is, if other data inputs were ignored.
438 //
439 // Because a subset of edges are considered, the resulting block will
440 // be earlier (at a shallower dom_depth) than the true schedule_early
441 // point of the node. We compute this earlier block as a more permissive
442 // site for anti-dependency insertion, but only if subsume_loads is enabled.
443 static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) {
444 Node* base;
445 Node* index;
446 Node* store = load->in(MemNode::Memory);
447 load->as_Mach()->memory_inputs(base, index);
448
449 assert(base != NodeSentinel && index != NodeSentinel,
450 "unexpected base/index inputs");
451
452 Node* mem_inputs[4];
453 int mem_inputs_length = 0;
454 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
455 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
456 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
457
458 // In the comparision below, add one to account for the control input,
459 // which may be null, but always takes up a spot in the in array.
460 if (mem_inputs_length + 1 < (int) load->req()) {
461 // This "load" has more inputs than just the memory, base and index inputs.
462 // For purposes of checking anti-dependences, we need to start
463 // from the early block of only the address portion of the instruction,
464 // and ignore other blocks that may have factored into the wider
465 // schedule_early calculation.
466 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
467
468 Block* deepb = NULL; // Deepest block so far
469 int deepb_dom_depth = 0;
470 for (int i = 0; i < mem_inputs_length; i++) {
471 Block* inb = cfg->get_block_for_node(mem_inputs[i]);
472 if (deepb_dom_depth < (int) inb->_dom_depth) {
473 // The new inb must be dominated by the previous deepb.
474 // The various inputs must be linearly ordered in the dom
475 // tree, or else there will not be a unique deepest block.
476 DEBUG_ONLY(assert_dom(deepb, inb, load, cfg));
477 deepb = inb; // Save deepest block
478 deepb_dom_depth = deepb->_dom_depth;
479 }
480 }
481 early = deepb;
482 }
483
484 return early;
485 }
486
487 //--------------------------insert_anti_dependences---------------------------
488 // A load may need to witness memory that nearby stores can overwrite.
489 // For each nearby store, either insert an "anti-dependence" edge
490 // from the load to the store, or else move LCA upward to force the
491 // load to (eventually) be scheduled in a block above the store.
492 //
493 // Do not add edges to stores on distinct control-flow paths;
494 // only add edges to stores which might interfere.
495 //
496 // Return the (updated) LCA. There will not be any possibly interfering
497 // store between the load's "early block" and the updated LCA.
498 // Any stores in the updated LCA will have new precedence edges
499 // back to the load. The caller is expected to schedule the load
500 // in the LCA, in which case the precedence edges will make LCM
501 // preserve anti-dependences. The caller may also hoist the load
502 // above the LCA, if it is not the early block.
503 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
504 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
505 assert(LCA != NULL, "");
506 DEBUG_ONLY(Block* LCA_orig = LCA);
507
508 // Compute the alias index. Loads and stores with different alias indices
509 // do not need anti-dependence edges.
510 int load_alias_idx = C->get_alias_index(load->adr_type());
511 #ifdef ASSERT
512 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
513 (PrintOpto || VerifyAliases ||
514 PrintMiscellaneous && (WizardMode || Verbose))) {
515 // Load nodes should not consume all of memory.
516 // Reporting a bottom type indicates a bug in adlc.
517 // If some particular type of node validly consumes all of memory,
518 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
519 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
520 load->dump(2);
521 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
522 }
523 #endif
524 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
525 "String compare is only known 'load' that does not conflict with any stores");
526 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals),
527 "String equals is a 'load' that does not conflict with any stores");
528 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf),
529 "String indexOf is a 'load' that does not conflict with any stores");
530 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOfChar),
531 "String indexOfChar is a 'load' that does not conflict with any stores");
532 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq),
533 "Arrays equals is a 'load' that does not conflict with any stores");
534 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_HasNegatives),
535 "HasNegatives is a 'load' that does not conflict with any stores");
536
537 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
538 // It is impossible to spoil this load by putting stores before it,
539 // because we know that the stores will never update the value
540 // which 'load' must witness.
541 return LCA;
542 }
543
544 node_idx_t load_index = load->_idx;
545
546 // Note the earliest legal placement of 'load', as determined by
547 // by the unique point in the dom tree where all memory effects
548 // and other inputs are first available. (Computed by schedule_early.)
549 // For normal loads, 'early' is the shallowest place (dom graph wise)
550 // to look for anti-deps between this load and any store.
551 Block* early = get_block_for_node(load);
552
553 // If we are subsuming loads, compute an "early" block that only considers
554 // memory or address inputs. This block may be different than the
555 // schedule_early block in that it could be at an even shallower depth in the
556 // dominator tree, and allow for a broader discovery of anti-dependences.
557 if (C->subsume_loads()) {
558 early = memory_early_block(load, early, this);
559 }
560
561 ResourceArea *area = Thread::current()->resource_area();
562 Node_List worklist_mem(area); // prior memory state to store
563 Node_List worklist_store(area); // possible-def to explore
564 Node_List worklist_visited(area); // visited mergemem nodes
565 Node_List non_early_stores(area); // all relevant stores outside of early
566 bool must_raise_LCA = false;
567
568 #ifdef TRACK_PHI_INPUTS
569 // %%% This extra checking fails because MergeMem nodes are not GVNed.
570 // Provide "phi_inputs" to check if every input to a PhiNode is from the
571 // original memory state. This indicates a PhiNode for which should not
572 // prevent the load from sinking. For such a block, set_raise_LCA_mark
573 // may be overly conservative.
574 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
575 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
576 #endif
577
578 // 'load' uses some memory state; look for users of the same state.
579 // Recurse through MergeMem nodes to the stores that use them.
580
581 // Each of these stores is a possible definition of memory
582 // that 'load' needs to use. We need to force 'load'
583 // to occur before each such store. When the store is in
584 // the same block as 'load', we insert an anti-dependence
585 // edge load->store.
586
587 // The relevant stores "nearby" the load consist of a tree rooted
588 // at initial_mem, with internal nodes of type MergeMem.
589 // Therefore, the branches visited by the worklist are of this form:
590 // initial_mem -> (MergeMem ->)* store
591 // The anti-dependence constraints apply only to the fringe of this tree.
592
593 Node* initial_mem = load->in(MemNode::Memory);
594 worklist_store.push(initial_mem);
595 worklist_visited.push(initial_mem);
596 worklist_mem.push(NULL);
597 while (worklist_store.size() > 0) {
598 // Examine a nearby store to see if it might interfere with our load.
599 Node* mem = worklist_mem.pop();
600 Node* store = worklist_store.pop();
601 uint op = store->Opcode();
602
603 // MergeMems do not directly have anti-deps.
604 // Treat them as internal nodes in a forward tree of memory states,
605 // the leaves of which are each a 'possible-def'.
606 if (store == initial_mem // root (exclusive) of tree we are searching
607 || op == Op_MergeMem // internal node of tree we are searching
608 ) {
609 mem = store; // It's not a possibly interfering store.
610 if (store == initial_mem)
611 initial_mem = NULL; // only process initial memory once
612
613 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
614 store = mem->fast_out(i);
615 if (store->is_MergeMem()) {
616 // Be sure we don't get into combinatorial problems.
617 // (Allow phis to be repeated; they can merge two relevant states.)
618 uint j = worklist_visited.size();
619 for (; j > 0; j--) {
620 if (worklist_visited.at(j-1) == store) break;
621 }
622 if (j > 0) continue; // already on work list; do not repeat
623 worklist_visited.push(store);
624 }
625 worklist_mem.push(mem);
626 worklist_store.push(store);
627 }
628 continue;
629 }
630
631 if (op == Op_MachProj || op == Op_Catch) continue;
632 if (store->needs_anti_dependence_check()) continue; // not really a store
633
634 // Compute the alias index. Loads and stores with different alias
635 // indices do not need anti-dependence edges. Wide MemBar's are
636 // anti-dependent on everything (except immutable memories).
637 const TypePtr* adr_type = store->adr_type();
638 if (!C->can_alias(adr_type, load_alias_idx)) continue;
639
640 // Most slow-path runtime calls do NOT modify Java memory, but
641 // they can block and so write Raw memory.
642 if (store->is_Mach()) {
643 MachNode* mstore = store->as_Mach();
644 if (load_alias_idx != Compile::AliasIdxRaw) {
645 // Check for call into the runtime using the Java calling
646 // convention (and from there into a wrapper); it has no
647 // _method. Can't do this optimization for Native calls because
648 // they CAN write to Java memory.
649 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
650 assert(mstore->is_MachSafePoint(), "");
651 MachSafePointNode* ms = (MachSafePointNode*) mstore;
652 assert(ms->is_MachCallJava(), "");
653 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
654 if (mcj->_method == NULL) {
655 // These runtime calls do not write to Java visible memory
656 // (other than Raw) and so do not require anti-dependence edges.
657 continue;
658 }
659 }
660 // Same for SafePoints: they read/write Raw but only read otherwise.
661 // This is basically a workaround for SafePoints only defining control
662 // instead of control + memory.
663 if (mstore->ideal_Opcode() == Op_SafePoint)
664 continue;
665 } else {
666 // Some raw memory, such as the load of "top" at an allocation,
667 // can be control dependent on the previous safepoint. See
668 // comments in GraphKit::allocate_heap() about control input.
669 // Inserting an anti-dep between such a safepoint and a use
670 // creates a cycle, and will cause a subsequent failure in
671 // local scheduling. (BugId 4919904)
672 // (%%% How can a control input be a safepoint and not a projection??)
673 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
674 continue;
675 }
676 }
677
678 // Identify a block that the current load must be above,
679 // or else observe that 'store' is all the way up in the
680 // earliest legal block for 'load'. In the latter case,
681 // immediately insert an anti-dependence edge.
682 Block* store_block = get_block_for_node(store);
683 assert(store_block != NULL, "unused killing projections skipped above");
684
685 if (store->is_Phi()) {
686 // 'load' uses memory which is one (or more) of the Phi's inputs.
687 // It must be scheduled not before the Phi, but rather before
688 // each of the relevant Phi inputs.
689 //
690 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
691 // we mark each corresponding predecessor block and do a combined
692 // hoisting operation later (raise_LCA_above_marks).
693 //
694 // Do not assert(store_block != early, "Phi merging memory after access")
695 // PhiNode may be at start of block 'early' with backedge to 'early'
696 DEBUG_ONLY(bool found_match = false);
697 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
698 if (store->in(j) == mem) { // Found matching input?
699 DEBUG_ONLY(found_match = true);
700 Block* pred_block = get_block_for_node(store_block->pred(j));
701 if (pred_block != early) {
702 // If any predecessor of the Phi matches the load's "early block",
703 // we do not need a precedence edge between the Phi and 'load'
704 // since the load will be forced into a block preceding the Phi.
705 pred_block->set_raise_LCA_mark(load_index);
706 assert(!LCA_orig->dominates(pred_block) ||
707 early->dominates(pred_block), "early is high enough");
708 must_raise_LCA = true;
709 } else {
710 // anti-dependent upon PHI pinned below 'early', no edge needed
711 LCA = early; // but can not schedule below 'early'
712 }
713 }
714 }
715 assert(found_match, "no worklist bug");
716 #ifdef TRACK_PHI_INPUTS
717 #ifdef ASSERT
718 // This assert asks about correct handling of PhiNodes, which may not
719 // have all input edges directly from 'mem'. See BugId 4621264
720 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
721 // Increment by exactly one even if there are multiple copies of 'mem'
722 // coming into the phi, because we will run this block several times
723 // if there are several copies of 'mem'. (That's how DU iterators work.)
724 phi_inputs.at_put(store->_idx, num_mem_inputs);
725 assert(PhiNode::Input + num_mem_inputs < store->req(),
726 "Expect at least one phi input will not be from original memory state");
727 #endif //ASSERT
728 #endif //TRACK_PHI_INPUTS
729 } else if (store_block != early) {
730 // 'store' is between the current LCA and earliest possible block.
731 // Label its block, and decide later on how to raise the LCA
732 // to include the effect on LCA of this store.
733 // If this store's block gets chosen as the raised LCA, we
734 // will find him on the non_early_stores list and stick him
735 // with a precedence edge.
736 // (But, don't bother if LCA is already raised all the way.)
737 if (LCA != early) {
738 store_block->set_raise_LCA_mark(load_index);
739 must_raise_LCA = true;
740 non_early_stores.push(store);
741 }
742 } else {
743 // Found a possibly-interfering store in the load's 'early' block.
744 // This means 'load' cannot sink at all in the dominator tree.
745 // Add an anti-dep edge, and squeeze 'load' into the highest block.
746 assert(store != load->in(0), "dependence cycle found");
747 if (verify) {
748 assert(store->find_edge(load) != -1, "missing precedence edge");
749 } else {
750 store->add_prec(load);
751 }
752 LCA = early;
753 // This turns off the process of gathering non_early_stores.
754 }
755 }
756 // (Worklist is now empty; all nearby stores have been visited.)
757
758 // Finished if 'load' must be scheduled in its 'early' block.
759 // If we found any stores there, they have already been given
760 // precedence edges.
761 if (LCA == early) return LCA;
762
763 // We get here only if there are no possibly-interfering stores
764 // in the load's 'early' block. Move LCA up above all predecessors
765 // which contain stores we have noted.
766 //
767 // The raised LCA block can be a home to such interfering stores,
768 // but its predecessors must not contain any such stores.
769 //
770 // The raised LCA will be a lower bound for placing the load,
771 // preventing the load from sinking past any block containing
772 // a store that may invalidate the memory state required by 'load'.
773 if (must_raise_LCA)
774 LCA = raise_LCA_above_marks(LCA, load->_idx, early, this);
775 if (LCA == early) return LCA;
776
777 // Insert anti-dependence edges from 'load' to each store
778 // in the non-early LCA block.
779 // Mine the non_early_stores list for such stores.
780 if (LCA->raise_LCA_mark() == load_index) {
781 while (non_early_stores.size() > 0) {
782 Node* store = non_early_stores.pop();
783 Block* store_block = get_block_for_node(store);
784 if (store_block == LCA) {
785 // add anti_dependence from store to load in its own block
786 assert(store != load->in(0), "dependence cycle found");
787 if (verify) {
788 assert(store->find_edge(load) != -1, "missing precedence edge");
789 } else {
790 store->add_prec(load);
791 }
792 } else {
793 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
794 // Any other stores we found must be either inside the new LCA
795 // or else outside the original LCA. In the latter case, they
796 // did not interfere with any use of 'load'.
797 assert(LCA->dominates(store_block)
798 || !LCA_orig->dominates(store_block), "no stray stores");
799 }
800 }
801 }
802
803 // Return the highest block containing stores; any stores
804 // within that block have been given anti-dependence edges.
805 return LCA;
806 }
807
808 // This class is used to iterate backwards over the nodes in the graph.
809
810 class Node_Backward_Iterator {
811
812 private:
813 Node_Backward_Iterator();
814
815 public:
816 // Constructor for the iterator
817 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg);
818
819 // Postincrement operator to iterate over the nodes
820 Node *next();
821
822 private:
823 VectorSet &_visited;
824 Node_Stack &_stack;
825 PhaseCFG &_cfg;
826 };
827
828 // Constructor for the Node_Backward_Iterator
829 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_Stack &stack, PhaseCFG &cfg)
830 : _visited(visited), _stack(stack), _cfg(cfg) {
831 // The stack should contain exactly the root
832 stack.clear();
833 stack.push(root, root->outcnt());
834
835 // Clear the visited bits
836 visited.Clear();
837 }
838
839 // Iterator for the Node_Backward_Iterator
840 Node *Node_Backward_Iterator::next() {
841
842 // If the _stack is empty, then just return NULL: finished.
843 if ( !_stack.size() )
844 return NULL;
845
846 // I visit unvisited not-anti-dependence users first, then anti-dependent
847 // children next. I iterate backwards to support removal of nodes.
848 // The stack holds states consisting of 3 values:
849 // current Def node, flag which indicates 1st/2nd pass, index of current out edge
850 Node *self = (Node*)(((uintptr_t)_stack.node()) & ~1);
851 bool iterate_anti_dep = (((uintptr_t)_stack.node()) & 1);
852 uint idx = MIN2(_stack.index(), self->outcnt()); // Support removal of nodes.
853 _stack.pop();
854
855 // I cycle here when I am entering a deeper level of recursion.
856 // The key variable 'self' was set prior to jumping here.
857 while( 1 ) {
858
859 _visited.set(self->_idx);
860
861 // Now schedule all uses as late as possible.
862 const Node* src = self->is_Proj() ? self->in(0) : self;
863 uint src_rpo = _cfg.get_block_for_node(src)->_rpo;
864
865 // Schedule all nodes in a post-order visit
866 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
867
868 // Scan for unvisited nodes
869 while (idx > 0) {
870 // For all uses, schedule late
871 Node* n = self->raw_out(--idx); // Use
872
873 // Skip already visited children
874 if ( _visited.test(n->_idx) )
875 continue;
876
877 // do not traverse backward control edges
878 Node *use = n->is_Proj() ? n->in(0) : n;
879 uint use_rpo = _cfg.get_block_for_node(use)->_rpo;
880
881 if ( use_rpo < src_rpo )
882 continue;
883
884 // Phi nodes always precede uses in a basic block
885 if ( use_rpo == src_rpo && use->is_Phi() )
886 continue;
887
888 unvisited = n; // Found unvisited
889
890 // Check for possible-anti-dependent
891 // 1st pass: No such nodes, 2nd pass: Only such nodes.
892 if (n->needs_anti_dependence_check() == iterate_anti_dep) {
893 unvisited = n; // Found unvisited
894 break;
895 }
896 }
897
898 // Did I find an unvisited not-anti-dependent Node?
899 if (!unvisited) {
900 if (!iterate_anti_dep) {
901 // 2nd pass: Iterate over nodes which needs_anti_dependence_check.
902 iterate_anti_dep = true;
903 idx = self->outcnt();
904 continue;
905 }
906 break; // All done with children; post-visit 'self'
907 }
908
909 // Visit the unvisited Node. Contains the obvious push to
910 // indicate I'm entering a deeper level of recursion. I push the
911 // old state onto the _stack and set a new state and loop (recurse).
912 _stack.push((Node*)((uintptr_t)self | (uintptr_t)iterate_anti_dep), idx);
913 self = unvisited;
914 iterate_anti_dep = false;
915 idx = self->outcnt();
916 } // End recursion loop
917
918 return self;
919 }
920
921 //------------------------------ComputeLatenciesBackwards----------------------
922 // Compute the latency of all the instructions.
923 void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_Stack &stack) {
924 #ifndef PRODUCT
925 if (trace_opto_pipelining())
926 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
927 #endif
928
929 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
930 Node *n;
931
932 // Walk over all the nodes from last to first
933 while (n = iter.next()) {
934 // Set the latency for the definitions of this instruction
935 partial_latency_of_defs(n);
936 }
937 } // end ComputeLatenciesBackwards
938
939 //------------------------------partial_latency_of_defs------------------------
940 // Compute the latency impact of this node on all defs. This computes
941 // a number that increases as we approach the beginning of the routine.
942 void PhaseCFG::partial_latency_of_defs(Node *n) {
943 // Set the latency for this instruction
944 #ifndef PRODUCT
945 if (trace_opto_pipelining()) {
946 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
947 dump();
948 }
949 #endif
950
951 if (n->is_Proj()) {
952 n = n->in(0);
953 }
954
955 if (n->is_Root()) {
956 return;
957 }
958
959 uint nlen = n->len();
960 uint use_latency = get_latency_for_node(n);
961 uint use_pre_order = get_block_for_node(n)->_pre_order;
962
963 for (uint j = 0; j < nlen; j++) {
964 Node *def = n->in(j);
965
966 if (!def || def == n) {
967 continue;
968 }
969
970 // Walk backwards thru projections
971 if (def->is_Proj()) {
972 def = def->in(0);
973 }
974
975 #ifndef PRODUCT
976 if (trace_opto_pipelining()) {
977 tty->print("# in(%2d): ", j);
978 def->dump();
979 }
980 #endif
981
982 // If the defining block is not known, assume it is ok
983 Block *def_block = get_block_for_node(def);
984 uint def_pre_order = def_block ? def_block->_pre_order : 0;
985
986 if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) {
987 continue;
988 }
989
990 uint delta_latency = n->latency(j);
991 uint current_latency = delta_latency + use_latency;
992
993 if (get_latency_for_node(def) < current_latency) {
994 set_latency_for_node(def, current_latency);
995 }
996
997 #ifndef PRODUCT
998 if (trace_opto_pipelining()) {
999 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));
1000 }
1001 #endif
1002 }
1003 }
1004
1005 //------------------------------latency_from_use-------------------------------
1006 // Compute the latency of a specific use
1007 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
1008 // If self-reference, return no latency
1009 if (use == n || use->is_Root()) {
1010 return 0;
1011 }
1012
1013 uint def_pre_order = get_block_for_node(def)->_pre_order;
1014 uint latency = 0;
1015
1016 // If the use is not a projection, then it is simple...
1017 if (!use->is_Proj()) {
1018 #ifndef PRODUCT
1019 if (trace_opto_pipelining()) {
1020 tty->print("# out(): ");
1021 use->dump();
1022 }
1023 #endif
1024
1025 uint use_pre_order = get_block_for_node(use)->_pre_order;
1026
1027 if (use_pre_order < def_pre_order)
1028 return 0;
1029
1030 if (use_pre_order == def_pre_order && use->is_Phi())
1031 return 0;
1032
1033 uint nlen = use->len();
1034 uint nl = get_latency_for_node(use);
1035
1036 for ( uint j=0; j<nlen; j++ ) {
1037 if (use->in(j) == n) {
1038 // Change this if we want local latencies
1039 uint ul = use->latency(j);
1040 uint l = ul + nl;
1041 if (latency < l) latency = l;
1042 #ifndef PRODUCT
1043 if (trace_opto_pipelining()) {
1044 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
1045 nl, j, ul, l, latency);
1046 }
1047 #endif
1048 }
1049 }
1050 } else {
1051 // This is a projection, just grab the latency of the use(s)
1052 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
1053 uint l = latency_from_use(use, def, use->fast_out(j));
1054 if (latency < l) latency = l;
1055 }
1056 }
1057
1058 return latency;
1059 }
1060
1061 //------------------------------latency_from_uses------------------------------
1062 // Compute the latency of this instruction relative to all of it's uses.
1063 // This computes a number that increases as we approach the beginning of the
1064 // routine.
1065 void PhaseCFG::latency_from_uses(Node *n) {
1066 // Set the latency for this instruction
1067 #ifndef PRODUCT
1068 if (trace_opto_pipelining()) {
1069 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1070 dump();
1071 }
1072 #endif
1073 uint latency=0;
1074 const Node *def = n->is_Proj() ? n->in(0): n;
1075
1076 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1077 uint l = latency_from_use(n, def, n->fast_out(i));
1078
1079 if (latency < l) latency = l;
1080 }
1081
1082 set_latency_for_node(n, latency);
1083 }
1084
1085 //------------------------------hoist_to_cheaper_block-------------------------
1086 // Pick a block for node self, between early and LCA, that is a cheaper
1087 // alternative to LCA.
1088 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1089 const double delta = 1+PROB_UNLIKELY_MAG(4);
1090 Block* least = LCA;
1091 double least_freq = least->_freq;
1092 uint target = get_latency_for_node(self);
1093 uint start_latency = get_latency_for_node(LCA->head());
1094 uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx()));
1095 bool in_latency = (target <= start_latency);
1096 const Block* root_block = get_block_for_node(_root);
1097
1098 // Turn off latency scheduling if scheduling is just plain off
1099 if (!C->do_scheduling())
1100 in_latency = true;
1101
1102 // Do not hoist (to cover latency) instructions which target a
1103 // single register. Hoisting stretches the live range of the
1104 // single register and may force spilling.
1105 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1106 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
1107 in_latency = true;
1108
1109 #ifndef PRODUCT
1110 if (trace_opto_pipelining()) {
1111 tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self));
1112 self->dump();
1113 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1114 LCA->_pre_order,
1115 LCA->head()->_idx,
1116 start_latency,
1117 LCA->get_node(LCA->end_idx())->_idx,
1118 end_latency,
1119 least_freq);
1120 }
1121 #endif
1122
1123 int cand_cnt = 0; // number of candidates tried
1124
1125 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1126 // the earliest legal location. Capture the least execution frequency.
1127 while (LCA != early) {
1128 LCA = LCA->_idom; // Follow up the dominator tree
1129
1130 if (LCA == NULL) {
1131 // Bailout without retry
1132 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1133 return least;
1134 }
1135
1136 // Don't hoist machine instructions to the root basic block
1137 if (mach && LCA == root_block)
1138 break;
1139
1140 uint start_lat = get_latency_for_node(LCA->head());
1141 uint end_idx = LCA->end_idx();
1142 uint end_lat = get_latency_for_node(LCA->get_node(end_idx));
1143 double LCA_freq = LCA->_freq;
1144 #ifndef PRODUCT
1145 if (trace_opto_pipelining()) {
1146 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1147 LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq);
1148 }
1149 #endif
1150 cand_cnt++;
1151 if (LCA_freq < least_freq || // Better Frequency
1152 (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
1153 (!StressGCM && // Otherwise, choose with latency
1154 !in_latency && // No block containing latency
1155 LCA_freq < least_freq * delta && // No worse frequency
1156 target >= end_lat && // within latency range
1157 !self->is_iteratively_computed() ) // But don't hoist IV increments
1158 // because they may end up above other uses of their phi forcing
1159 // their result register to be different from their input.
1160 ) {
1161 least = LCA; // Found cheaper block
1162 least_freq = LCA_freq;
1163 start_latency = start_lat;
1164 end_latency = end_lat;
1165 if (target <= start_lat)
1166 in_latency = true;
1167 }
1168 }
1169
1170 #ifndef PRODUCT
1171 if (trace_opto_pipelining()) {
1172 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1173 least->_pre_order, start_latency, least_freq);
1174 }
1175 #endif
1176
1177 // See if the latency needs to be updated
1178 if (target < end_latency) {
1179 #ifndef PRODUCT
1180 if (trace_opto_pipelining()) {
1181 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1182 }
1183 #endif
1184 set_latency_for_node(self, end_latency);
1185 partial_latency_of_defs(self);
1186 }
1187
1188 return least;
1189 }
1190
1191
1192 //------------------------------schedule_late-----------------------------------
1193 // Now schedule all codes as LATE as possible. This is the LCA in the
1194 // dominator tree of all USES of a value. Pick the block with the least
1195 // loop nesting depth that is lowest in the dominator tree.
1196 extern const char must_clone[];
1197 void PhaseCFG::schedule_late(VectorSet &visited, Node_Stack &stack) {
1198 #ifndef PRODUCT
1199 if (trace_opto_pipelining())
1200 tty->print("\n#---- schedule_late ----\n");
1201 #endif
1202
1203 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1204 Node *self;
1205
1206 // Walk over all the nodes from last to first
1207 while (self = iter.next()) {
1208 Block* early = get_block_for_node(self); // Earliest legal placement
1209
1210 if (self->is_top()) {
1211 // Top node goes in bb #2 with other constants.
1212 // It must be special-cased, because it has no out edges.
1213 early->add_inst(self);
1214 continue;
1215 }
1216
1217 // No uses, just terminate
1218 if (self->outcnt() == 0) {
1219 assert(self->is_MachProj(), "sanity");
1220 continue; // Must be a dead machine projection
1221 }
1222
1223 // If node is pinned in the block, then no scheduling can be done.
1224 if( self->pinned() ) // Pinned in block?
1225 continue;
1226
1227 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1228 if (mach) {
1229 switch (mach->ideal_Opcode()) {
1230 case Op_CreateEx:
1231 // Don't move exception creation
1232 early->add_inst(self);
1233 continue;
1234 break;
1235 case Op_CheckCastPP:
1236 // Don't move CheckCastPP nodes away from their input, if the input
1237 // is a rawptr (5071820).
1238 Node *def = self->in(1);
1239 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1240 early->add_inst(self);
1241 #ifdef ASSERT
1242 _raw_oops.push(def);
1243 #endif
1244 continue;
1245 }
1246 break;
1247 }
1248 }
1249
1250 // Gather LCA of all uses
1251 Block *LCA = NULL;
1252 {
1253 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1254 // For all uses, find LCA
1255 Node* use = self->fast_out(i);
1256 LCA = raise_LCA_above_use(LCA, use, self, this);
1257 }
1258 } // (Hide defs of imax, i from rest of block.)
1259
1260 // Place temps in the block of their use. This isn't a
1261 // requirement for correctness but it reduces useless
1262 // interference between temps and other nodes.
1263 if (mach != NULL && mach->is_MachTemp()) {
1264 map_node_to_block(self, LCA);
1265 LCA->add_inst(self);
1266 continue;
1267 }
1268
1269 // Check if 'self' could be anti-dependent on memory
1270 if (self->needs_anti_dependence_check()) {
1271 // Hoist LCA above possible-defs and insert anti-dependences to
1272 // defs in new LCA block.
1273 LCA = insert_anti_dependences(LCA, self);
1274 }
1275
1276 if (early->_dom_depth > LCA->_dom_depth) {
1277 // Somehow the LCA has moved above the earliest legal point.
1278 // (One way this can happen is via memory_early_block.)
1279 if (C->subsume_loads() == true && !C->failing()) {
1280 // Retry with subsume_loads == false
1281 // If this is the first failure, the sentinel string will "stick"
1282 // to the Compile object, and the C2Compiler will see it and retry.
1283 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1284 } else {
1285 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1286 C->record_method_not_compilable("late schedule failed: incorrect graph");
1287 }
1288 return;
1289 }
1290
1291 // If there is no opportunity to hoist, then we're done.
1292 // In stress mode, try to hoist even the single operations.
1293 bool try_to_hoist = StressGCM || (LCA != early);
1294
1295 // Must clone guys stay next to use; no hoisting allowed.
1296 // Also cannot hoist guys that alter memory or are otherwise not
1297 // allocatable (hoisting can make a value live longer, leading to
1298 // anti and output dependency problems which are normally resolved
1299 // by the register allocator giving everyone a different register).
1300 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1301 try_to_hoist = false;
1302
1303 Block* late = NULL;
1304 if (try_to_hoist) {
1305 // Now find the block with the least execution frequency.
1306 // Start at the latest schedule and work up to the earliest schedule
1307 // in the dominator tree. Thus the Node will dominate all its uses.
1308 late = hoist_to_cheaper_block(LCA, early, self);
1309 } else {
1310 // Just use the LCA of the uses.
1311 late = LCA;
1312 }
1313
1314 // Put the node into target block
1315 schedule_node_into_block(self, late);
1316
1317 #ifdef ASSERT
1318 if (self->needs_anti_dependence_check()) {
1319 // since precedence edges are only inserted when we're sure they
1320 // are needed make sure that after placement in a block we don't
1321 // need any new precedence edges.
1322 verify_anti_dependences(late, self);
1323 }
1324 #endif
1325 } // Loop until all nodes have been visited
1326
1327 } // end ScheduleLate
1328
1329 //------------------------------GlobalCodeMotion-------------------------------
1330 void PhaseCFG::global_code_motion() {
1331 ResourceMark rm;
1332
1333 #ifndef PRODUCT
1334 if (trace_opto_pipelining()) {
1335 tty->print("\n---- Start GlobalCodeMotion ----\n");
1336 }
1337 #endif
1338
1339 // Initialize the node to block mapping for things on the proj_list
1340 for (uint i = 0; i < _matcher.number_of_projections(); i++) {
1341 unmap_node_from_block(_matcher.get_projection(i));
1342 }
1343
1344 // Set the basic block for Nodes pinned into blocks
1345 Arena* arena = Thread::current()->resource_area();
1346 VectorSet visited(arena);
1347 schedule_pinned_nodes(visited);
1348
1349 // Find the earliest Block any instruction can be placed in. Some
1350 // instructions are pinned into Blocks. Unpinned instructions can
1351 // appear in last block in which all their inputs occur.
1352 visited.Clear();
1353 Node_Stack stack(arena, (C->live_nodes() >> 2) + 16); // pre-grow
1354 if (!schedule_early(visited, stack)) {
1355 // Bailout without retry
1356 C->record_method_not_compilable("early schedule failed");
1357 return;
1358 }
1359
1360 // Build Def-Use edges.
1361 // Compute the latency information (via backwards walk) for all the
1362 // instructions in the graph
1363 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1364
1365 if (C->do_scheduling()) {
1366 compute_latencies_backwards(visited, stack);
1367 }
1368
1369 // Now schedule all codes as LATE as possible. This is the LCA in the
1370 // dominator tree of all USES of a value. Pick the block with the least
1371 // loop nesting depth that is lowest in the dominator tree.
1372 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1373 schedule_late(visited, stack);
1374 if (C->failing()) {
1375 // schedule_late fails only when graph is incorrect.
1376 assert(!VerifyGraphEdges, "verification should have failed");
1377 return;
1378 }
1379
1380 #ifndef PRODUCT
1381 if (trace_opto_pipelining()) {
1382 tty->print("\n---- Detect implicit null checks ----\n");
1383 }
1384 #endif
1385
1386 // Detect implicit-null-check opportunities. Basically, find NULL checks
1387 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1388 // I can generate a memory op if there is not one nearby.
1389 if (C->is_method_compilation()) {
1390 // By reversing the loop direction we get a very minor gain on mpegaudio.
1391 // Feel free to revert to a forward loop for clarity.
1392 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1393 for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) {
1394 Node* proj = _matcher._null_check_tests[i];
1395 Node* val = _matcher._null_check_tests[i + 1];
1396 Block* block = get_block_for_node(proj);
1397 implicit_null_check(block, proj, val, C->allowed_deopt_reasons());
1398 // The implicit_null_check will only perform the transformation
1399 // if the null branch is truly uncommon, *and* it leads to an
1400 // uncommon trap. Combined with the too_many_traps guards
1401 // above, this prevents SEGV storms reported in 6366351,
1402 // by recompiling offending methods without this optimization.
1403 }
1404 }
1405
1406 bool block_size_threshold_ok = false;
1407 intptr_t *recalc_pressure_nodes = NULL;
1408 if (OptoRegScheduling) {
1409 for (uint i = 0; i < number_of_blocks(); i++) {
1410 Block* block = get_block(i);
1411 if (block->number_of_nodes() > 10) {
1412 block_size_threshold_ok = true;
1413 break;
1414 }
1415 }
1416 }
1417
1418 // Enabling the scheduler for register pressure plus finding blocks of size to schedule for it
1419 // is key to enabling this feature.
1420 PhaseChaitin regalloc(C->unique(), *this, _matcher, true);
1421 ResourceArea live_arena; // Arena for liveness
1422 ResourceMark rm_live(&live_arena);
1423 PhaseLive live(*this, regalloc._lrg_map.names(), &live_arena, true);
1424 PhaseIFG ifg(&live_arena);
1425 if (OptoRegScheduling && block_size_threshold_ok) {
1426 regalloc.mark_ssa();
1427 Compile::TracePhase tp("computeLive", &timers[_t_computeLive]);
1428 rm_live.reset_to_mark(); // Reclaim working storage
1429 IndexSet::reset_memory(C, &live_arena);
1430 uint node_size = regalloc._lrg_map.max_lrg_id();
1431 ifg.init(node_size); // Empty IFG
1432 regalloc.set_ifg(ifg);
1433 regalloc.set_live(live);
1434 regalloc.gather_lrg_masks(false); // Collect LRG masks
1435 live.compute(node_size); // Compute liveness
1436
1437 recalc_pressure_nodes = NEW_RESOURCE_ARRAY(intptr_t, node_size);
1438 for (uint i = 0; i < node_size; i++) {
1439 recalc_pressure_nodes[i] = 0;
1440 }
1441 }
1442 _regalloc = ®alloc;
1443
1444 #ifndef PRODUCT
1445 if (trace_opto_pipelining()) {
1446 tty->print("\n---- Start Local Scheduling ----\n");
1447 }
1448 #endif
1449
1450 // Schedule locally. Right now a simple topological sort.
1451 // Later, do a real latency aware scheduler.
1452 GrowableArray<int> ready_cnt(C->unique(), C->unique(), -1);
1453 visited.Clear();
1454 for (uint i = 0; i < number_of_blocks(); i++) {
1455 Block* block = get_block(i);
1456 if (!schedule_local(block, ready_cnt, visited, recalc_pressure_nodes)) {
1457 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1458 C->record_method_not_compilable("local schedule failed");
1459 }
1460 _regalloc = NULL;
1461 return;
1462 }
1463 }
1464 _regalloc = NULL;
1465
1466 // If we inserted any instructions between a Call and his CatchNode,
1467 // clone the instructions on all paths below the Catch.
1468 for (uint i = 0; i < number_of_blocks(); i++) {
1469 Block* block = get_block(i);
1470 call_catch_cleanup(block);
1471 }
1472
1473 #ifndef PRODUCT
1474 if (trace_opto_pipelining()) {
1475 tty->print("\n---- After GlobalCodeMotion ----\n");
1476 for (uint i = 0; i < number_of_blocks(); i++) {
1477 Block* block = get_block(i);
1478 block->dump();
1479 }
1480 }
1481 #endif
1482 // Dead.
1483 _node_latency = (GrowableArray<uint> *)0xdeadbeef;
1484 }
1485
1486 bool PhaseCFG::do_global_code_motion() {
1487
1488 build_dominator_tree();
1489 if (C->failing()) {
1490 return false;
1491 }
1492
1493 NOT_PRODUCT( C->verify_graph_edges(); )
1494
1495 estimate_block_frequency();
1496
1497 global_code_motion();
1498
1499 if (C->failing()) {
1500 return false;
1501 }
1502
1503 return true;
1504 }
1505
1506 //------------------------------Estimate_Block_Frequency-----------------------
1507 // Estimate block frequencies based on IfNode probabilities.
1508 void PhaseCFG::estimate_block_frequency() {
1509
1510 // Force conditional branches leading to uncommon traps to be unlikely,
1511 // not because we get to the uncommon_trap with less relative frequency,
1512 // but because an uncommon_trap typically causes a deopt, so we only get
1513 // there once.
1514 if (C->do_freq_based_layout()) {
1515 Block_List worklist;
1516 Block* root_blk = get_block(0);
1517 for (uint i = 1; i < root_blk->num_preds(); i++) {
1518 Block *pb = get_block_for_node(root_blk->pred(i));
1519 if (pb->has_uncommon_code()) {
1520 worklist.push(pb);
1521 }
1522 }
1523 while (worklist.size() > 0) {
1524 Block* uct = worklist.pop();
1525 if (uct == get_root_block()) {
1526 continue;
1527 }
1528 for (uint i = 1; i < uct->num_preds(); i++) {
1529 Block *pb = get_block_for_node(uct->pred(i));
1530 if (pb->_num_succs == 1) {
1531 worklist.push(pb);
1532 } else if (pb->num_fall_throughs() == 2) {
1533 pb->update_uncommon_branch(uct);
1534 }
1535 }
1536 }
1537 }
1538
1539 // Create the loop tree and calculate loop depth.
1540 _root_loop = create_loop_tree();
1541 _root_loop->compute_loop_depth(0);
1542
1543 // Compute block frequency of each block, relative to a single loop entry.
1544 _root_loop->compute_freq();
1545
1546 // Adjust all frequencies to be relative to a single method entry
1547 _root_loop->_freq = 1.0;
1548 _root_loop->scale_freq();
1549
1550 // Save outmost loop frequency for LRG frequency threshold
1551 _outer_loop_frequency = _root_loop->outer_loop_freq();
1552
1553 // force paths ending at uncommon traps to be infrequent
1554 if (!C->do_freq_based_layout()) {
1555 Block_List worklist;
1556 Block* root_blk = get_block(0);
1557 for (uint i = 1; i < root_blk->num_preds(); i++) {
1558 Block *pb = get_block_for_node(root_blk->pred(i));
1559 if (pb->has_uncommon_code()) {
1560 worklist.push(pb);
1561 }
1562 }
1563 while (worklist.size() > 0) {
1564 Block* uct = worklist.pop();
1565 uct->_freq = PROB_MIN;
1566 for (uint i = 1; i < uct->num_preds(); i++) {
1567 Block *pb = get_block_for_node(uct->pred(i));
1568 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1569 worklist.push(pb);
1570 }
1571 }
1572 }
1573 }
1574
1575 #ifdef ASSERT
1576 for (uint i = 0; i < number_of_blocks(); i++) {
1577 Block* b = get_block(i);
1578 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
1579 }
1580 #endif
1581
1582 #ifndef PRODUCT
1583 if (PrintCFGBlockFreq) {
1584 tty->print_cr("CFG Block Frequencies");
1585 _root_loop->dump_tree();
1586 if (Verbose) {
1587 tty->print_cr("PhaseCFG dump");
1588 dump();
1589 tty->print_cr("Node dump");
1590 _root->dump(99999);
1591 }
1592 }
1593 #endif
1594 }
1595
1596 //----------------------------create_loop_tree--------------------------------
1597 // Create a loop tree from the CFG
1598 CFGLoop* PhaseCFG::create_loop_tree() {
1599
1600 #ifdef ASSERT
1601 assert(get_block(0) == get_root_block(), "first block should be root block");
1602 for (uint i = 0; i < number_of_blocks(); i++) {
1603 Block* block = get_block(i);
1604 // Check that _loop field are clear...we could clear them if not.
1605 assert(block->_loop == NULL, "clear _loop expected");
1606 // Sanity check that the RPO numbering is reflected in the _blocks array.
1607 // It doesn't have to be for the loop tree to be built, but if it is not,
1608 // then the blocks have been reordered since dom graph building...which
1609 // may question the RPO numbering
1610 assert(block->_rpo == i, "unexpected reverse post order number");
1611 }
1612 #endif
1613
1614 int idct = 0;
1615 CFGLoop* root_loop = new CFGLoop(idct++);
1616
1617 Block_List worklist;
1618
1619 // Assign blocks to loops
1620 for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block
1621 Block* block = get_block(i);
1622
1623 if (block->head()->is_Loop()) {
1624 Block* loop_head = block;
1625 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1626 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1627 Block* tail = get_block_for_node(tail_n);
1628
1629 // Defensively filter out Loop nodes for non-single-entry loops.
1630 // For all reasonable loops, the head occurs before the tail in RPO.
1631 if (i <= tail->_rpo) {
1632
1633 // The tail and (recursive) predecessors of the tail
1634 // are made members of a new loop.
1635
1636 assert(worklist.size() == 0, "nonempty worklist");
1637 CFGLoop* nloop = new CFGLoop(idct++);
1638 assert(loop_head->_loop == NULL, "just checking");
1639 loop_head->_loop = nloop;
1640 // Add to nloop so push_pred() will skip over inner loops
1641 nloop->add_member(loop_head);
1642 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this);
1643
1644 while (worklist.size() > 0) {
1645 Block* member = worklist.pop();
1646 if (member != loop_head) {
1647 for (uint j = 1; j < member->num_preds(); j++) {
1648 nloop->push_pred(member, j, worklist, this);
1649 }
1650 }
1651 }
1652 }
1653 }
1654 }
1655
1656 // Create a member list for each loop consisting
1657 // of both blocks and (immediate child) loops.
1658 for (uint i = 0; i < number_of_blocks(); i++) {
1659 Block* block = get_block(i);
1660 CFGLoop* lp = block->_loop;
1661 if (lp == NULL) {
1662 // Not assigned to a loop. Add it to the method's pseudo loop.
1663 block->_loop = root_loop;
1664 lp = root_loop;
1665 }
1666 if (lp == root_loop || block != lp->head()) { // loop heads are already members
1667 lp->add_member(block);
1668 }
1669 if (lp != root_loop) {
1670 if (lp->parent() == NULL) {
1671 // Not a nested loop. Make it a child of the method's pseudo loop.
1672 root_loop->add_nested_loop(lp);
1673 }
1674 if (block == lp->head()) {
1675 // Add nested loop to member list of parent loop.
1676 lp->parent()->add_member(lp);
1677 }
1678 }
1679 }
1680
1681 return root_loop;
1682 }
1683
1684 //------------------------------push_pred--------------------------------------
1685 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) {
1686 Node* pred_n = blk->pred(i);
1687 Block* pred = cfg->get_block_for_node(pred_n);
1688 CFGLoop *pred_loop = pred->_loop;
1689 if (pred_loop == NULL) {
1690 // Filter out blocks for non-single-entry loops.
1691 // For all reasonable loops, the head occurs before the tail in RPO.
1692 if (pred->_rpo > head()->_rpo) {
1693 pred->_loop = this;
1694 worklist.push(pred);
1695 }
1696 } else if (pred_loop != this) {
1697 // Nested loop.
1698 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1699 pred_loop = pred_loop->_parent;
1700 }
1701 // Make pred's loop be a child
1702 if (pred_loop->_parent == NULL) {
1703 add_nested_loop(pred_loop);
1704 // Continue with loop entry predecessor.
1705 Block* pred_head = pred_loop->head();
1706 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1707 assert(pred_head != head(), "loop head in only one loop");
1708 push_pred(pred_head, LoopNode::EntryControl, worklist, cfg);
1709 } else {
1710 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1711 }
1712 }
1713 }
1714
1715 //------------------------------add_nested_loop--------------------------------
1716 // Make cl a child of the current loop in the loop tree.
1717 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1718 assert(_parent == NULL, "no parent yet");
1719 assert(cl != this, "not my own parent");
1720 cl->_parent = this;
1721 CFGLoop* ch = _child;
1722 if (ch == NULL) {
1723 _child = cl;
1724 } else {
1725 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1726 ch->_sibling = cl;
1727 }
1728 }
1729
1730 //------------------------------compute_loop_depth-----------------------------
1731 // Store the loop depth in each CFGLoop object.
1732 // Recursively walk the children to do the same for them.
1733 void CFGLoop::compute_loop_depth(int depth) {
1734 _depth = depth;
1735 CFGLoop* ch = _child;
1736 while (ch != NULL) {
1737 ch->compute_loop_depth(depth + 1);
1738 ch = ch->_sibling;
1739 }
1740 }
1741
1742 //------------------------------compute_freq-----------------------------------
1743 // Compute the frequency of each block and loop, relative to a single entry
1744 // into the dominating loop head.
1745 void CFGLoop::compute_freq() {
1746 // Bottom up traversal of loop tree (visit inner loops first.)
1747 // Set loop head frequency to 1.0, then transitively
1748 // compute frequency for all successors in the loop,
1749 // as well as for each exit edge. Inner loops are
1750 // treated as single blocks with loop exit targets
1751 // as the successor blocks.
1752
1753 // Nested loops first
1754 CFGLoop* ch = _child;
1755 while (ch != NULL) {
1756 ch->compute_freq();
1757 ch = ch->_sibling;
1758 }
1759 assert (_members.length() > 0, "no empty loops");
1760 Block* hd = head();
1761 hd->_freq = 1.0;
1762 for (int i = 0; i < _members.length(); i++) {
1763 CFGElement* s = _members.at(i);
1764 double freq = s->_freq;
1765 if (s->is_block()) {
1766 Block* b = s->as_Block();
1767 for (uint j = 0; j < b->_num_succs; j++) {
1768 Block* sb = b->_succs[j];
1769 update_succ_freq(sb, freq * b->succ_prob(j));
1770 }
1771 } else {
1772 CFGLoop* lp = s->as_CFGLoop();
1773 assert(lp->_parent == this, "immediate child");
1774 for (int k = 0; k < lp->_exits.length(); k++) {
1775 Block* eb = lp->_exits.at(k).get_target();
1776 double prob = lp->_exits.at(k).get_prob();
1777 update_succ_freq(eb, freq * prob);
1778 }
1779 }
1780 }
1781
1782 // For all loops other than the outer, "method" loop,
1783 // sum and normalize the exit probability. The "method" loop
1784 // should keep the initial exit probability of 1, so that
1785 // inner blocks do not get erroneously scaled.
1786 if (_depth != 0) {
1787 // Total the exit probabilities for this loop.
1788 double exits_sum = 0.0f;
1789 for (int i = 0; i < _exits.length(); i++) {
1790 exits_sum += _exits.at(i).get_prob();
1791 }
1792
1793 // Normalize the exit probabilities. Until now, the
1794 // probabilities estimate the possibility of exit per
1795 // a single loop iteration; afterward, they estimate
1796 // the probability of exit per loop entry.
1797 for (int i = 0; i < _exits.length(); i++) {
1798 Block* et = _exits.at(i).get_target();
1799 float new_prob = 0.0f;
1800 if (_exits.at(i).get_prob() > 0.0f) {
1801 new_prob = _exits.at(i).get_prob() / exits_sum;
1802 }
1803 BlockProbPair bpp(et, new_prob);
1804 _exits.at_put(i, bpp);
1805 }
1806
1807 // Save the total, but guard against unreasonable probability,
1808 // as the value is used to estimate the loop trip count.
1809 // An infinite trip count would blur relative block
1810 // frequencies.
1811 if (exits_sum > 1.0f) exits_sum = 1.0;
1812 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1813 _exit_prob = exits_sum;
1814 }
1815 }
1816
1817 //------------------------------succ_prob-------------------------------------
1818 // Determine the probability of reaching successor 'i' from the receiver block.
1819 float Block::succ_prob(uint i) {
1820 int eidx = end_idx();
1821 Node *n = get_node(eidx); // Get ending Node
1822
1823 int op = n->Opcode();
1824 if (n->is_Mach()) {
1825 if (n->is_MachNullCheck()) {
1826 // Can only reach here if called after lcm. The original Op_If is gone,
1827 // so we attempt to infer the probability from one or both of the
1828 // successor blocks.
1829 assert(_num_succs == 2, "expecting 2 successors of a null check");
1830 // If either successor has only one predecessor, then the
1831 // probability estimate can be derived using the
1832 // relative frequency of the successor and this block.
1833 if (_succs[i]->num_preds() == 2) {
1834 return _succs[i]->_freq / _freq;
1835 } else if (_succs[1-i]->num_preds() == 2) {
1836 return 1 - (_succs[1-i]->_freq / _freq);
1837 } else {
1838 // Estimate using both successor frequencies
1839 float freq = _succs[i]->_freq;
1840 return freq / (freq + _succs[1-i]->_freq);
1841 }
1842 }
1843 op = n->as_Mach()->ideal_Opcode();
1844 }
1845
1846
1847 // Switch on branch type
1848 switch( op ) {
1849 case Op_CountedLoopEnd:
1850 case Op_If: {
1851 assert (i < 2, "just checking");
1852 // Conditionals pass on only part of their frequency
1853 float prob = n->as_MachIf()->_prob;
1854 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1855 // If succ[i] is the FALSE branch, invert path info
1856 if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) {
1857 return 1.0f - prob; // not taken
1858 } else {
1859 return prob; // taken
1860 }
1861 }
1862
1863 case Op_Jump:
1864 // Divide the frequency between all successors evenly
1865 return 1.0f/_num_succs;
1866
1867 case Op_Catch: {
1868 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1869 if (ci->_con == CatchProjNode::fall_through_index) {
1870 // Fall-thru path gets the lion's share.
1871 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1872 } else {
1873 // Presume exceptional paths are equally unlikely
1874 return PROB_UNLIKELY_MAG(5);
1875 }
1876 }
1877
1878 case Op_Root:
1879 case Op_Goto:
1880 // Pass frequency straight thru to target
1881 return 1.0f;
1882
1883 case Op_NeverBranch:
1884 return 0.0f;
1885
1886 case Op_TailCall:
1887 case Op_TailJump:
1888 case Op_Return:
1889 case Op_Halt:
1890 case Op_Rethrow:
1891 // Do not push out freq to root block
1892 return 0.0f;
1893
1894 default:
1895 ShouldNotReachHere();
1896 }
1897
1898 return 0.0f;
1899 }
1900
1901 //------------------------------num_fall_throughs-----------------------------
1902 // Return the number of fall-through candidates for a block
1903 int Block::num_fall_throughs() {
1904 int eidx = end_idx();
1905 Node *n = get_node(eidx); // Get ending Node
1906
1907 int op = n->Opcode();
1908 if (n->is_Mach()) {
1909 if (n->is_MachNullCheck()) {
1910 // In theory, either side can fall-thru, for simplicity sake,
1911 // let's say only the false branch can now.
1912 return 1;
1913 }
1914 op = n->as_Mach()->ideal_Opcode();
1915 }
1916
1917 // Switch on branch type
1918 switch( op ) {
1919 case Op_CountedLoopEnd:
1920 case Op_If:
1921 return 2;
1922
1923 case Op_Root:
1924 case Op_Goto:
1925 return 1;
1926
1927 case Op_Catch: {
1928 for (uint i = 0; i < _num_succs; i++) {
1929 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1930 if (ci->_con == CatchProjNode::fall_through_index) {
1931 return 1;
1932 }
1933 }
1934 return 0;
1935 }
1936
1937 case Op_Jump:
1938 case Op_NeverBranch:
1939 case Op_TailCall:
1940 case Op_TailJump:
1941 case Op_Return:
1942 case Op_Halt:
1943 case Op_Rethrow:
1944 return 0;
1945
1946 default:
1947 ShouldNotReachHere();
1948 }
1949
1950 return 0;
1951 }
1952
1953 //------------------------------succ_fall_through-----------------------------
1954 // Return true if a specific successor could be fall-through target.
1955 bool Block::succ_fall_through(uint i) {
1956 int eidx = end_idx();
1957 Node *n = get_node(eidx); // Get ending Node
1958
1959 int op = n->Opcode();
1960 if (n->is_Mach()) {
1961 if (n->is_MachNullCheck()) {
1962 // In theory, either side can fall-thru, for simplicity sake,
1963 // let's say only the false branch can now.
1964 return get_node(i + eidx + 1)->Opcode() == Op_IfFalse;
1965 }
1966 op = n->as_Mach()->ideal_Opcode();
1967 }
1968
1969 // Switch on branch type
1970 switch( op ) {
1971 case Op_CountedLoopEnd:
1972 case Op_If:
1973 case Op_Root:
1974 case Op_Goto:
1975 return true;
1976
1977 case Op_Catch: {
1978 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1979 return ci->_con == CatchProjNode::fall_through_index;
1980 }
1981
1982 case Op_Jump:
1983 case Op_NeverBranch:
1984 case Op_TailCall:
1985 case Op_TailJump:
1986 case Op_Return:
1987 case Op_Halt:
1988 case Op_Rethrow:
1989 return false;
1990
1991 default:
1992 ShouldNotReachHere();
1993 }
1994
1995 return false;
1996 }
1997
1998 //------------------------------update_uncommon_branch------------------------
1999 // Update the probability of a two-branch to be uncommon
2000 void Block::update_uncommon_branch(Block* ub) {
2001 int eidx = end_idx();
2002 Node *n = get_node(eidx); // Get ending Node
2003
2004 int op = n->as_Mach()->ideal_Opcode();
2005
2006 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
2007 assert(num_fall_throughs() == 2, "must be a two way branch block");
2008
2009 // Which successor is ub?
2010 uint s;
2011 for (s = 0; s <_num_succs; s++) {
2012 if (_succs[s] == ub) break;
2013 }
2014 assert(s < 2, "uncommon successor must be found");
2015
2016 // If ub is the true path, make the proability small, else
2017 // ub is the false path, and make the probability large
2018 bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse);
2019
2020 // Get existing probability
2021 float p = n->as_MachIf()->_prob;
2022
2023 if (invert) p = 1.0 - p;
2024 if (p > PROB_MIN) {
2025 p = PROB_MIN;
2026 }
2027 if (invert) p = 1.0 - p;
2028
2029 n->as_MachIf()->_prob = p;
2030 }
2031
2032 //------------------------------update_succ_freq-------------------------------
2033 // Update the appropriate frequency associated with block 'b', a successor of
2034 // a block in this loop.
2035 void CFGLoop::update_succ_freq(Block* b, double freq) {
2036 if (b->_loop == this) {
2037 if (b == head()) {
2038 // back branch within the loop
2039 // Do nothing now, the loop carried frequency will be
2040 // adjust later in scale_freq().
2041 } else {
2042 // simple branch within the loop
2043 b->_freq += freq;
2044 }
2045 } else if (!in_loop_nest(b)) {
2046 // branch is exit from this loop
2047 BlockProbPair bpp(b, freq);
2048 _exits.append(bpp);
2049 } else {
2050 // branch into nested loop
2051 CFGLoop* ch = b->_loop;
2052 ch->_freq += freq;
2053 }
2054 }
2055
2056 //------------------------------in_loop_nest-----------------------------------
2057 // Determine if block b is in the receiver's loop nest.
2058 bool CFGLoop::in_loop_nest(Block* b) {
2059 int depth = _depth;
2060 CFGLoop* b_loop = b->_loop;
2061 int b_depth = b_loop->_depth;
2062 if (depth == b_depth) {
2063 return true;
2064 }
2065 while (b_depth > depth) {
2066 b_loop = b_loop->_parent;
2067 b_depth = b_loop->_depth;
2068 }
2069 return b_loop == this;
2070 }
2071
2072 //------------------------------scale_freq-------------------------------------
2073 // Scale frequency of loops and blocks by trip counts from outer loops
2074 // Do a top down traversal of loop tree (visit outer loops first.)
2075 void CFGLoop::scale_freq() {
2076 double loop_freq = _freq * trip_count();
2077 _freq = loop_freq;
2078 for (int i = 0; i < _members.length(); i++) {
2079 CFGElement* s = _members.at(i);
2080 double block_freq = s->_freq * loop_freq;
2081 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
2082 block_freq = MIN_BLOCK_FREQUENCY;
2083 s->_freq = block_freq;
2084 }
2085 CFGLoop* ch = _child;
2086 while (ch != NULL) {
2087 ch->scale_freq();
2088 ch = ch->_sibling;
2089 }
2090 }
2091
2092 // Frequency of outer loop
2093 double CFGLoop::outer_loop_freq() const {
2094 if (_child != NULL) {
2095 return _child->_freq;
2096 }
2097 return _freq;
2098 }
2099
2100 #ifndef PRODUCT
2101 //------------------------------dump_tree--------------------------------------
2102 void CFGLoop::dump_tree() const {
2103 dump();
2104 if (_child != NULL) _child->dump_tree();
2105 if (_sibling != NULL) _sibling->dump_tree();
2106 }
2107
2108 //------------------------------dump-------------------------------------------
2109 void CFGLoop::dump() const {
2110 for (int i = 0; i < _depth; i++) tty->print(" ");
2111 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
2112 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
2113 for (int i = 0; i < _depth; i++) tty->print(" ");
2114 tty->print(" members:");
2115 int k = 0;
2116 for (int i = 0; i < _members.length(); i++) {
2117 if (k++ >= 6) {
2118 tty->print("\n ");
2119 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2120 k = 0;
2121 }
2122 CFGElement *s = _members.at(i);
2123 if (s->is_block()) {
2124 Block *b = s->as_Block();
2125 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
2126 } else {
2127 CFGLoop* lp = s->as_CFGLoop();
2128 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
2129 }
2130 }
2131 tty->print("\n");
2132 for (int i = 0; i < _depth; i++) tty->print(" ");
2133 tty->print(" exits: ");
2134 k = 0;
2135 for (int i = 0; i < _exits.length(); i++) {
2136 if (k++ >= 7) {
2137 tty->print("\n ");
2138 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2139 k = 0;
2140 }
2141 Block *blk = _exits.at(i).get_target();
2142 double prob = _exits.at(i).get_prob();
2143 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2144 }
2145 tty->print("\n");
2146 }
2147 #endif