1 /*
2 * Copyright (c) 1997, 2014, 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.
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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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "libadt/vectset.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/block.hpp"
29 #include "opto/c2compiler.hpp"
30 #include "opto/callnode.hpp"
31 #include "opto/cfgnode.hpp"
32 #include "opto/machnode.hpp"
33 #include "opto/opcodes.hpp"
34 #include "opto/phaseX.hpp"
35 #include "opto/rootnode.hpp"
36 #include "opto/runtime.hpp"
37 #include "runtime/deoptimization.hpp"
38
39 // Portions of code courtesy of Clifford Click
40
41 // Optimization - Graph Style
42
43 // To avoid float value underflow
44 #define MIN_BLOCK_FREQUENCY 1.e-35f
45
46 //----------------------------schedule_node_into_block-------------------------
47 // Insert node n into block b. Look for projections of n and make sure they
48 // are in b also.
49 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
50 // Set basic block of n, Add n to b,
51 map_node_to_block(n, b);
52 b->add_inst(n);
53
54 // After Matching, nearly any old Node may have projections trailing it.
55 // These are usually machine-dependent flags. In any case, they might
56 // float to another block below this one. Move them up.
57 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
58 Node* use = n->fast_out(i);
59 if (use->is_Proj()) {
60 Block* buse = get_block_for_node(use);
61 if (buse != b) { // In wrong block?
62 if (buse != NULL) {
63 buse->find_remove(use); // Remove from wrong block
64 }
65 map_node_to_block(use, b);
66 b->add_inst(use);
67 }
68 }
69 }
70 }
71
72 //----------------------------replace_block_proj_ctrl-------------------------
73 // Nodes that have is_block_proj() nodes as their control need to use
74 // the appropriate Region for their actual block as their control since
75 // the projection will be in a predecessor block.
76 void PhaseCFG::replace_block_proj_ctrl( Node *n ) {
77 const Node *in0 = n->in(0);
78 assert(in0 != NULL, "Only control-dependent");
79 const Node *p = in0->is_block_proj();
80 if (p != NULL && p != n) { // Control from a block projection?
81 assert(!n->pinned() || n->is_MachConstantBase(), "only pinned MachConstantBase node is expected here");
82 // Find trailing Region
83 Block *pb = get_block_for_node(in0); // Block-projection already has basic block
84 uint j = 0;
85 if (pb->_num_succs != 1) { // More then 1 successor?
86 // Search for successor
87 uint max = pb->number_of_nodes();
88 assert( max > 1, "" );
89 uint start = max - pb->_num_succs;
90 // Find which output path belongs to projection
91 for (j = start; j < max; j++) {
92 if( pb->get_node(j) == in0 )
93 break;
94 }
95 assert( j < max, "must find" );
96 // Change control to match head of successor basic block
97 j -= start;
98 }
99 n->set_req(0, pb->_succs[j]->head());
100 }
101 }
102
103 static bool is_dominator(Block* d, Block* n) {
104 return d->dom_lca(n) == d;
105 }
106
107 //------------------------------schedule_pinned_nodes--------------------------
108 // Set the basic block for Nodes pinned into blocks
109 void PhaseCFG::schedule_pinned_nodes(VectorSet &visited) {
110 // Allocate node stack of size C->unique()+8 to avoid frequent realloc
111 GrowableArray <Node *> spstack(C->unique() + 8);
112 spstack.push(_root);
113 while (spstack.is_nonempty()) {
114 Node* node = spstack.pop();
115 if (!visited.test_set(node->_idx)) { // Test node and flag it as visited
116 if (node->pinned() && !has_block(node)) { // Pinned? Nail it down!
117 assert(node->in(0), "pinned Node must have Control");
118 // Before setting block replace block_proj control edge
119 replace_block_proj_ctrl(node);
120 Node* input = node->in(0);
121 while (!input->is_block_start()) {
122 input = input->in(0);
123 }
124 Block* block = get_block_for_node(input); // Basic block of controlling input
125 schedule_node_into_block(node, block);
126 }
127
128 // If the node has precedence edges (added when CastPP nodes are
129 // removed in final_graph_reshaping), fix the control of the
130 // node to cover the precedence edges and remove the
131 // dependencies.
132 Node* n = NULL;
133 for (uint i = node->len()-1; i >= node->req(); i--) {
134 Node* m = node->in(i);
135 if (m == NULL) continue;
136 // See Compile::final_graph_reshaping_impl(): we expect a test
137 // or a Region here.
138 if (m->is_block_proj() || m->is_block_start()) {
139 node->rm_prec(i);
140 if (n == NULL) {
141 n = m;
142 } else {
143 Block* bn = get_block_for_node(n);
144 Block* bm = get_block_for_node(m);
145 n = is_dominator(bn, bm) ? m : n;
146 }
147 }
148 }
149 if (n != NULL) {
150 assert(node->in(0), "control should have been set");
151 Block* bn = get_block_for_node(n);
152 Block* bnode = get_block_for_node(node->in(0));
153 if (!is_dominator(bn, bnode)) {
154 node->set_req(0, n);
155 }
156 }
157
158 // process all inputs that are non NULL
159 for (int i = node->req() - 1; i >= 0; --i) {
160 if (node->in(i) != NULL) {
161 spstack.push(node->in(i));
162 }
163 }
164 }
165 }
166 }
167
168 #ifdef ASSERT
169 // Assert that new input b2 is dominated by all previous inputs.
170 // Check this by by seeing that it is dominated by b1, the deepest
171 // input observed until b2.
172 static void assert_dom(Block* b1, Block* b2, Node* n, const PhaseCFG* cfg) {
173 if (b1 == NULL) return;
174 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
175 Block* tmp = b2;
176 while (tmp != b1 && tmp != NULL) {
177 tmp = tmp->_idom;
178 }
179 if (tmp != b1) {
180 // Detected an unschedulable graph. Print some nice stuff and die.
181 tty->print_cr("!!! Unschedulable graph !!!");
182 for (uint j=0; j<n->len(); j++) { // For all inputs
183 Node* inn = n->in(j); // Get input
184 if (inn == NULL) continue; // Ignore NULL, missing inputs
185 Block* inb = cfg->get_block_for_node(inn);
186 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
187 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
188 inn->dump();
189 }
190 tty->print("Failing node: ");
191 n->dump();
192 assert(false, "unscheduable graph");
193 }
194 }
195 #endif
196
197 static Block* find_deepest_input(Node* n, const PhaseCFG* cfg) {
198 // Find the last input dominated by all other inputs.
199 Block* deepb = NULL; // Deepest block so far
200 int deepb_dom_depth = 0;
201 for (uint k = 0; k < n->len(); k++) { // For all inputs
202 Node* inn = n->in(k); // Get input
203 if (inn == NULL) continue; // Ignore NULL, missing inputs
204 Block* inb = cfg->get_block_for_node(inn);
205 assert(inb != NULL, "must already have scheduled this input");
206 if (deepb_dom_depth < (int) inb->_dom_depth) {
207 // The new inb must be dominated by the previous deepb.
208 // The various inputs must be linearly ordered in the dom
209 // tree, or else there will not be a unique deepest block.
210 DEBUG_ONLY(assert_dom(deepb, inb, n, cfg));
211 deepb = inb; // Save deepest block
212 deepb_dom_depth = deepb->_dom_depth;
213 }
214 }
215 assert(deepb != NULL, "must be at least one input to n");
216 return deepb;
217 }
218
219
220 //------------------------------schedule_early---------------------------------
221 // Find the earliest Block any instruction can be placed in. Some instructions
222 // are pinned into Blocks. Unpinned instructions can appear in last block in
223 // which all their inputs occur.
224 bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) {
225 // Allocate stack with enough space to avoid frequent realloc
226 Node_Stack nstack(roots.Size() + 8);
227 // _root will be processed among C->top() inputs
228 roots.push(C->top());
229 visited.set(C->top()->_idx);
230
231 while (roots.size() != 0) {
232 // Use local variables nstack_top_n & nstack_top_i to cache values
233 // on stack's top.
234 Node* parent_node = roots.pop();
235 uint input_index = 0;
236
237 while (true) {
238 if (input_index == 0) {
239 // Fixup some control. Constants without control get attached
240 // to root and nodes that use is_block_proj() nodes should be attached
241 // to the region that starts their block.
242 const Node* control_input = parent_node->in(0);
243 if (control_input != NULL) {
244 replace_block_proj_ctrl(parent_node);
245 } else {
246 // Is a constant with NO inputs?
247 if (parent_node->req() == 1) {
248 parent_node->set_req(0, _root);
249 }
250 }
251 }
252
253 // First, visit all inputs and force them to get a block. If an
254 // input is already in a block we quit following inputs (to avoid
255 // cycles). Instead we put that Node on a worklist to be handled
256 // later (since IT'S inputs may not have a block yet).
257
258 // Assume all n's inputs will be processed
259 bool done = true;
260
261 while (input_index < parent_node->len()) {
262 Node* in = parent_node->in(input_index++);
263 if (in == NULL) {
264 continue;
265 }
266
267 int is_visited = visited.test_set(in->_idx);
268 if (!has_block(in)) {
269 if (is_visited) {
270 return false;
271 }
272 // Save parent node and next input's index.
273 nstack.push(parent_node, input_index);
274 // Process current input now.
275 parent_node = in;
276 input_index = 0;
277 // Not all n's inputs processed.
278 done = false;
279 break;
280 } else if (!is_visited) {
281 // Visit this guy later, using worklist
282 roots.push(in);
283 }
284 }
285
286 if (done) {
287 // All of n's inputs have been processed, complete post-processing.
288
289 // Some instructions are pinned into a block. These include Region,
290 // Phi, Start, Return, and other control-dependent instructions and
291 // any projections which depend on them.
292 if (!parent_node->pinned()) {
293 // Set earliest legal block.
294 Block* earliest_block = find_deepest_input(parent_node, this);
295 map_node_to_block(parent_node, earliest_block);
296 } else {
297 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");
298 }
299
300 if (nstack.is_empty()) {
301 // Finished all nodes on stack.
302 // Process next node on the worklist 'roots'.
303 break;
304 }
305 // Get saved parent node and next input's index.
306 parent_node = nstack.node();
307 input_index = nstack.index();
308 nstack.pop();
309 }
310 }
311 }
312 return true;
313 }
314
315 //------------------------------dom_lca----------------------------------------
316 // Find least common ancestor in dominator tree
317 // LCA is a current notion of LCA, to be raised above 'this'.
318 // As a convenient boundary condition, return 'this' if LCA is NULL.
319 // Find the LCA of those two nodes.
320 Block* Block::dom_lca(Block* LCA) {
321 if (LCA == NULL || LCA == this) return this;
322
323 Block* anc = this;
324 while (anc->_dom_depth > LCA->_dom_depth)
325 anc = anc->_idom; // Walk up till anc is as high as LCA
326
327 while (LCA->_dom_depth > anc->_dom_depth)
328 LCA = LCA->_idom; // Walk up till LCA is as high as anc
329
330 while (LCA != anc) { // Walk both up till they are the same
331 LCA = LCA->_idom;
332 anc = anc->_idom;
333 }
334
335 return LCA;
336 }
337
338 //--------------------------raise_LCA_above_use--------------------------------
339 // We are placing a definition, and have been given a def->use edge.
340 // The definition must dominate the use, so move the LCA upward in the
341 // dominator tree to dominate the use. If the use is a phi, adjust
342 // the LCA only with the phi input paths which actually use this def.
343 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) {
344 Block* buse = cfg->get_block_for_node(use);
345 if (buse == NULL) return LCA; // Unused killing Projs have no use block
346 if (!use->is_Phi()) return buse->dom_lca(LCA);
347 uint pmax = use->req(); // Number of Phi inputs
348 // Why does not this loop just break after finding the matching input to
349 // the Phi? Well...it's like this. I do not have true def-use/use-def
350 // chains. Means I cannot distinguish, from the def-use direction, which
351 // of many use-defs lead from the same use to the same def. That is, this
352 // Phi might have several uses of the same def. Each use appears in a
353 // different predecessor block. But when I enter here, I cannot distinguish
354 // which use-def edge I should find the predecessor block for. So I find
355 // them all. Means I do a little extra work if a Phi uses the same value
356 // more than once.
357 for (uint j=1; j<pmax; j++) { // For all inputs
358 if (use->in(j) == def) { // Found matching input?
359 Block* pred = cfg->get_block_for_node(buse->pred(j));
360 LCA = pred->dom_lca(LCA);
361 }
362 }
363 return LCA;
364 }
365
366 //----------------------------raise_LCA_above_marks----------------------------
367 // Return a new LCA that dominates LCA and any of its marked predecessors.
368 // Search all my parents up to 'early' (exclusive), looking for predecessors
369 // which are marked with the given index. Return the LCA (in the dom tree)
370 // of all marked blocks. If there are none marked, return the original
371 // LCA.
372 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) {
373 Block_List worklist;
374 worklist.push(LCA);
375 while (worklist.size() > 0) {
376 Block* mid = worklist.pop();
377 if (mid == early) continue; // stop searching here
378
379 // Test and set the visited bit.
380 if (mid->raise_LCA_visited() == mark) continue; // already visited
381
382 // Don't process the current LCA, otherwise the search may terminate early
383 if (mid != LCA && mid->raise_LCA_mark() == mark) {
384 // Raise the LCA.
385 LCA = mid->dom_lca(LCA);
386 if (LCA == early) break; // stop searching everywhere
387 assert(early->dominates(LCA), "early is high enough");
388 // Resume searching at that point, skipping intermediate levels.
389 worklist.push(LCA);
390 if (LCA == mid)
391 continue; // Don't mark as visited to avoid early termination.
392 } else {
393 // Keep searching through this block's predecessors.
394 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
395 Block* mid_parent = cfg->get_block_for_node(mid->pred(j));
396 worklist.push(mid_parent);
397 }
398 }
399 mid->set_raise_LCA_visited(mark);
400 }
401 return LCA;
402 }
403
404 //--------------------------memory_early_block--------------------------------
405 // This is a variation of find_deepest_input, the heart of schedule_early.
406 // Find the "early" block for a load, if we considered only memory and
407 // address inputs, that is, if other data inputs were ignored.
408 //
409 // Because a subset of edges are considered, the resulting block will
410 // be earlier (at a shallower dom_depth) than the true schedule_early
411 // point of the node. We compute this earlier block as a more permissive
412 // site for anti-dependency insertion, but only if subsume_loads is enabled.
413 static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) {
414 Node* base;
415 Node* index;
416 Node* store = load->in(MemNode::Memory);
417 load->as_Mach()->memory_inputs(base, index);
418
419 assert(base != NodeSentinel && index != NodeSentinel,
420 "unexpected base/index inputs");
421
422 Node* mem_inputs[4];
423 int mem_inputs_length = 0;
424 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
425 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
426 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
427
428 // In the comparision below, add one to account for the control input,
429 // which may be null, but always takes up a spot in the in array.
430 if (mem_inputs_length + 1 < (int) load->req()) {
431 // This "load" has more inputs than just the memory, base and index inputs.
432 // For purposes of checking anti-dependences, we need to start
433 // from the early block of only the address portion of the instruction,
434 // and ignore other blocks that may have factored into the wider
435 // schedule_early calculation.
436 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
437
438 Block* deepb = NULL; // Deepest block so far
439 int deepb_dom_depth = 0;
440 for (int i = 0; i < mem_inputs_length; i++) {
441 Block* inb = cfg->get_block_for_node(mem_inputs[i]);
442 if (deepb_dom_depth < (int) inb->_dom_depth) {
443 // The new inb must be dominated by the previous deepb.
444 // The various inputs must be linearly ordered in the dom
445 // tree, or else there will not be a unique deepest block.
446 DEBUG_ONLY(assert_dom(deepb, inb, load, cfg));
447 deepb = inb; // Save deepest block
448 deepb_dom_depth = deepb->_dom_depth;
449 }
450 }
451 early = deepb;
452 }
453
454 return early;
455 }
456
457 //--------------------------insert_anti_dependences---------------------------
458 // A load may need to witness memory that nearby stores can overwrite.
459 // For each nearby store, either insert an "anti-dependence" edge
460 // from the load to the store, or else move LCA upward to force the
461 // load to (eventually) be scheduled in a block above the store.
462 //
463 // Do not add edges to stores on distinct control-flow paths;
464 // only add edges to stores which might interfere.
465 //
466 // Return the (updated) LCA. There will not be any possibly interfering
467 // store between the load's "early block" and the updated LCA.
468 // Any stores in the updated LCA will have new precedence edges
469 // back to the load. The caller is expected to schedule the load
470 // in the LCA, in which case the precedence edges will make LCM
471 // preserve anti-dependences. The caller may also hoist the load
472 // above the LCA, if it is not the early block.
473 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
474 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
475 assert(LCA != NULL, "");
476 DEBUG_ONLY(Block* LCA_orig = LCA);
477
478 // Compute the alias index. Loads and stores with different alias indices
479 // do not need anti-dependence edges.
480 uint load_alias_idx = C->get_alias_index(load->adr_type());
481 #ifdef ASSERT
482 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
483 (PrintOpto || VerifyAliases ||
484 PrintMiscellaneous && (WizardMode || Verbose))) {
485 // Load nodes should not consume all of memory.
486 // Reporting a bottom type indicates a bug in adlc.
487 // If some particular type of node validly consumes all of memory,
488 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
489 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
490 load->dump(2);
491 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
492 }
493 #endif
494 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
495 "String compare is only known 'load' that does not conflict with any stores");
496 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals),
497 "String equals is a 'load' that does not conflict with any stores");
498 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf),
499 "String indexOf is a 'load' that does not conflict with any stores");
500 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq),
501 "Arrays equals is a 'load' that do not conflict with any stores");
502
503 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
504 // It is impossible to spoil this load by putting stores before it,
505 // because we know that the stores will never update the value
506 // which 'load' must witness.
507 return LCA;
508 }
509
510 node_idx_t load_index = load->_idx;
511
512 // Note the earliest legal placement of 'load', as determined by
513 // by the unique point in the dom tree where all memory effects
514 // and other inputs are first available. (Computed by schedule_early.)
515 // For normal loads, 'early' is the shallowest place (dom graph wise)
516 // to look for anti-deps between this load and any store.
517 Block* early = get_block_for_node(load);
518
519 // If we are subsuming loads, compute an "early" block that only considers
520 // memory or address inputs. This block may be different than the
521 // schedule_early block in that it could be at an even shallower depth in the
522 // dominator tree, and allow for a broader discovery of anti-dependences.
523 if (C->subsume_loads()) {
524 early = memory_early_block(load, early, this);
525 }
526
527 ResourceArea *area = Thread::current()->resource_area();
528 Node_List worklist_mem(area); // prior memory state to store
529 Node_List worklist_store(area); // possible-def to explore
530 Node_List worklist_visited(area); // visited mergemem nodes
531 Node_List non_early_stores(area); // all relevant stores outside of early
532 bool must_raise_LCA = false;
533
534 #ifdef TRACK_PHI_INPUTS
535 // %%% This extra checking fails because MergeMem nodes are not GVNed.
536 // Provide "phi_inputs" to check if every input to a PhiNode is from the
537 // original memory state. This indicates a PhiNode for which should not
538 // prevent the load from sinking. For such a block, set_raise_LCA_mark
539 // may be overly conservative.
540 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
541 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
542 #endif
543
544 // 'load' uses some memory state; look for users of the same state.
545 // Recurse through MergeMem nodes to the stores that use them.
546
547 // Each of these stores is a possible definition of memory
548 // that 'load' needs to use. We need to force 'load'
549 // to occur before each such store. When the store is in
550 // the same block as 'load', we insert an anti-dependence
551 // edge load->store.
552
553 // The relevant stores "nearby" the load consist of a tree rooted
554 // at initial_mem, with internal nodes of type MergeMem.
555 // Therefore, the branches visited by the worklist are of this form:
556 // initial_mem -> (MergeMem ->)* store
557 // The anti-dependence constraints apply only to the fringe of this tree.
558
559 Node* initial_mem = load->in(MemNode::Memory);
560 worklist_store.push(initial_mem);
561 worklist_visited.push(initial_mem);
562 worklist_mem.push(NULL);
563 while (worklist_store.size() > 0) {
564 // Examine a nearby store to see if it might interfere with our load.
565 Node* mem = worklist_mem.pop();
566 Node* store = worklist_store.pop();
567 uint op = store->Opcode();
568
569 // MergeMems do not directly have anti-deps.
570 // Treat them as internal nodes in a forward tree of memory states,
571 // the leaves of which are each a 'possible-def'.
572 if (store == initial_mem // root (exclusive) of tree we are searching
573 || op == Op_MergeMem // internal node of tree we are searching
574 ) {
575 mem = store; // It's not a possibly interfering store.
576 if (store == initial_mem)
577 initial_mem = NULL; // only process initial memory once
578
579 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
580 store = mem->fast_out(i);
581 if (store->is_MergeMem()) {
582 // Be sure we don't get into combinatorial problems.
583 // (Allow phis to be repeated; they can merge two relevant states.)
584 uint j = worklist_visited.size();
585 for (; j > 0; j--) {
586 if (worklist_visited.at(j-1) == store) break;
587 }
588 if (j > 0) continue; // already on work list; do not repeat
589 worklist_visited.push(store);
590 }
591 worklist_mem.push(mem);
592 worklist_store.push(store);
593 }
594 continue;
595 }
596
597 if (op == Op_MachProj || op == Op_Catch) continue;
598 if (store->needs_anti_dependence_check()) continue; // not really a store
599
600 // Compute the alias index. Loads and stores with different alias
601 // indices do not need anti-dependence edges. Wide MemBar's are
602 // anti-dependent on everything (except immutable memories).
603 const TypePtr* adr_type = store->adr_type();
604 if (!C->can_alias(adr_type, load_alias_idx)) continue;
605
606 // Most slow-path runtime calls do NOT modify Java memory, but
607 // they can block and so write Raw memory.
608 if (store->is_Mach()) {
609 MachNode* mstore = store->as_Mach();
610 if (load_alias_idx != Compile::AliasIdxRaw) {
611 // Check for call into the runtime using the Java calling
612 // convention (and from there into a wrapper); it has no
613 // _method. Can't do this optimization for Native calls because
614 // they CAN write to Java memory.
615 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
616 assert(mstore->is_MachSafePoint(), "");
617 MachSafePointNode* ms = (MachSafePointNode*) mstore;
618 assert(ms->is_MachCallJava(), "");
619 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
620 if (mcj->_method == NULL) {
621 // These runtime calls do not write to Java visible memory
622 // (other than Raw) and so do not require anti-dependence edges.
623 continue;
624 }
625 }
626 // Same for SafePoints: they read/write Raw but only read otherwise.
627 // This is basically a workaround for SafePoints only defining control
628 // instead of control + memory.
629 if (mstore->ideal_Opcode() == Op_SafePoint)
630 continue;
631 } else {
632 // Some raw memory, such as the load of "top" at an allocation,
633 // can be control dependent on the previous safepoint. See
634 // comments in GraphKit::allocate_heap() about control input.
635 // Inserting an anti-dep between such a safepoint and a use
636 // creates a cycle, and will cause a subsequent failure in
637 // local scheduling. (BugId 4919904)
638 // (%%% How can a control input be a safepoint and not a projection??)
639 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
640 continue;
641 }
642 }
643
644 // Identify a block that the current load must be above,
645 // or else observe that 'store' is all the way up in the
646 // earliest legal block for 'load'. In the latter case,
647 // immediately insert an anti-dependence edge.
648 Block* store_block = get_block_for_node(store);
649 assert(store_block != NULL, "unused killing projections skipped above");
650
651 if (store->is_Phi()) {
652 // 'load' uses memory which is one (or more) of the Phi's inputs.
653 // It must be scheduled not before the Phi, but rather before
654 // each of the relevant Phi inputs.
655 //
656 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
657 // we mark each corresponding predecessor block and do a combined
658 // hoisting operation later (raise_LCA_above_marks).
659 //
660 // Do not assert(store_block != early, "Phi merging memory after access")
661 // PhiNode may be at start of block 'early' with backedge to 'early'
662 DEBUG_ONLY(bool found_match = false);
663 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
664 if (store->in(j) == mem) { // Found matching input?
665 DEBUG_ONLY(found_match = true);
666 Block* pred_block = get_block_for_node(store_block->pred(j));
667 if (pred_block != early) {
668 // If any predecessor of the Phi matches the load's "early block",
669 // we do not need a precedence edge between the Phi and 'load'
670 // since the load will be forced into a block preceding the Phi.
671 pred_block->set_raise_LCA_mark(load_index);
672 assert(!LCA_orig->dominates(pred_block) ||
673 early->dominates(pred_block), "early is high enough");
674 must_raise_LCA = true;
675 } else {
676 // anti-dependent upon PHI pinned below 'early', no edge needed
677 LCA = early; // but can not schedule below 'early'
678 }
679 }
680 }
681 assert(found_match, "no worklist bug");
682 #ifdef TRACK_PHI_INPUTS
683 #ifdef ASSERT
684 // This assert asks about correct handling of PhiNodes, which may not
685 // have all input edges directly from 'mem'. See BugId 4621264
686 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
687 // Increment by exactly one even if there are multiple copies of 'mem'
688 // coming into the phi, because we will run this block several times
689 // if there are several copies of 'mem'. (That's how DU iterators work.)
690 phi_inputs.at_put(store->_idx, num_mem_inputs);
691 assert(PhiNode::Input + num_mem_inputs < store->req(),
692 "Expect at least one phi input will not be from original memory state");
693 #endif //ASSERT
694 #endif //TRACK_PHI_INPUTS
695 } else if (store_block != early) {
696 // 'store' is between the current LCA and earliest possible block.
697 // Label its block, and decide later on how to raise the LCA
698 // to include the effect on LCA of this store.
699 // If this store's block gets chosen as the raised LCA, we
700 // will find him on the non_early_stores list and stick him
701 // with a precedence edge.
702 // (But, don't bother if LCA is already raised all the way.)
703 if (LCA != early) {
704 store_block->set_raise_LCA_mark(load_index);
705 must_raise_LCA = true;
706 non_early_stores.push(store);
707 }
708 } else {
709 // Found a possibly-interfering store in the load's 'early' block.
710 // This means 'load' cannot sink at all in the dominator tree.
711 // Add an anti-dep edge, and squeeze 'load' into the highest block.
712 assert(store != load->in(0), "dependence cycle found");
713 if (verify) {
714 assert(store->find_edge(load) != -1, "missing precedence edge");
715 } else {
716 store->add_prec(load);
717 }
718 LCA = early;
719 // This turns off the process of gathering non_early_stores.
720 }
721 }
722 // (Worklist is now empty; all nearby stores have been visited.)
723
724 // Finished if 'load' must be scheduled in its 'early' block.
725 // If we found any stores there, they have already been given
726 // precedence edges.
727 if (LCA == early) return LCA;
728
729 // We get here only if there are no possibly-interfering stores
730 // in the load's 'early' block. Move LCA up above all predecessors
731 // which contain stores we have noted.
732 //
733 // The raised LCA block can be a home to such interfering stores,
734 // but its predecessors must not contain any such stores.
735 //
736 // The raised LCA will be a lower bound for placing the load,
737 // preventing the load from sinking past any block containing
738 // a store that may invalidate the memory state required by 'load'.
739 if (must_raise_LCA)
740 LCA = raise_LCA_above_marks(LCA, load->_idx, early, this);
741 if (LCA == early) return LCA;
742
743 // Insert anti-dependence edges from 'load' to each store
744 // in the non-early LCA block.
745 // Mine the non_early_stores list for such stores.
746 if (LCA->raise_LCA_mark() == load_index) {
747 while (non_early_stores.size() > 0) {
748 Node* store = non_early_stores.pop();
749 Block* store_block = get_block_for_node(store);
750 if (store_block == LCA) {
751 // add anti_dependence from store to load in its own block
752 assert(store != load->in(0), "dependence cycle found");
753 if (verify) {
754 assert(store->find_edge(load) != -1, "missing precedence edge");
755 } else {
756 store->add_prec(load);
757 }
758 } else {
759 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
760 // Any other stores we found must be either inside the new LCA
761 // or else outside the original LCA. In the latter case, they
762 // did not interfere with any use of 'load'.
763 assert(LCA->dominates(store_block)
764 || !LCA_orig->dominates(store_block), "no stray stores");
765 }
766 }
767 }
768
769 // Return the highest block containing stores; any stores
770 // within that block have been given anti-dependence edges.
771 return LCA;
772 }
773
774 // This class is used to iterate backwards over the nodes in the graph.
775
776 class Node_Backward_Iterator {
777
778 private:
779 Node_Backward_Iterator();
780
781 public:
782 // Constructor for the iterator
783 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg);
784
785 // Postincrement operator to iterate over the nodes
786 Node *next();
787
788 private:
789 VectorSet &_visited;
790 Node_List &_stack;
791 PhaseCFG &_cfg;
792 };
793
794 // Constructor for the Node_Backward_Iterator
795 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg)
796 : _visited(visited), _stack(stack), _cfg(cfg) {
797 // The stack should contain exactly the root
798 stack.clear();
799 stack.push(root);
800
801 // Clear the visited bits
802 visited.Clear();
803 }
804
805 // Iterator for the Node_Backward_Iterator
806 Node *Node_Backward_Iterator::next() {
807
808 // If the _stack is empty, then just return NULL: finished.
809 if ( !_stack.size() )
810 return NULL;
811
812 // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been
813 // made stateless, so I do not need to record the index 'i' on my _stack.
814 // Instead I visit all users each time, scanning for unvisited users.
815 // I visit unvisited not-anti-dependence users first, then anti-dependent
816 // children next.
817 Node *self = _stack.pop();
818
819 // I cycle here when I am entering a deeper level of recursion.
820 // The key variable 'self' was set prior to jumping here.
821 while( 1 ) {
822
823 _visited.set(self->_idx);
824
825 // Now schedule all uses as late as possible.
826 const Node* src = self->is_Proj() ? self->in(0) : self;
827 uint src_rpo = _cfg.get_block_for_node(src)->_rpo;
828
829 // Schedule all nodes in a post-order visit
830 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
831
832 // Scan for unvisited nodes
833 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
834 // For all uses, schedule late
835 Node* n = self->fast_out(i); // Use
836
837 // Skip already visited children
838 if ( _visited.test(n->_idx) )
839 continue;
840
841 // do not traverse backward control edges
842 Node *use = n->is_Proj() ? n->in(0) : n;
843 uint use_rpo = _cfg.get_block_for_node(use)->_rpo;
844
845 if ( use_rpo < src_rpo )
846 continue;
847
848 // Phi nodes always precede uses in a basic block
849 if ( use_rpo == src_rpo && use->is_Phi() )
850 continue;
851
852 unvisited = n; // Found unvisited
853
854 // Check for possible-anti-dependent
855 if( !n->needs_anti_dependence_check() )
856 break; // Not visited, not anti-dep; schedule it NOW
857 }
858
859 // Did I find an unvisited not-anti-dependent Node?
860 if ( !unvisited )
861 break; // All done with children; post-visit 'self'
862
863 // Visit the unvisited Node. Contains the obvious push to
864 // indicate I'm entering a deeper level of recursion. I push the
865 // old state onto the _stack and set a new state and loop (recurse).
866 _stack.push(self);
867 self = unvisited;
868 } // End recursion loop
869
870 return self;
871 }
872
873 //------------------------------ComputeLatenciesBackwards----------------------
874 // Compute the latency of all the instructions.
875 void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_List &stack) {
876 #ifndef PRODUCT
877 if (trace_opto_pipelining())
878 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
879 #endif
880
881 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
882 Node *n;
883
884 // Walk over all the nodes from last to first
885 while (n = iter.next()) {
886 // Set the latency for the definitions of this instruction
887 partial_latency_of_defs(n);
888 }
889 } // end ComputeLatenciesBackwards
890
891 //------------------------------partial_latency_of_defs------------------------
892 // Compute the latency impact of this node on all defs. This computes
893 // a number that increases as we approach the beginning of the routine.
894 void PhaseCFG::partial_latency_of_defs(Node *n) {
895 // Set the latency for this instruction
896 #ifndef PRODUCT
897 if (trace_opto_pipelining()) {
898 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
899 dump();
900 }
901 #endif
902
903 if (n->is_Proj()) {
904 n = n->in(0);
905 }
906
907 if (n->is_Root()) {
908 return;
909 }
910
911 uint nlen = n->len();
912 uint use_latency = get_latency_for_node(n);
913 uint use_pre_order = get_block_for_node(n)->_pre_order;
914
915 for (uint j = 0; j < nlen; j++) {
916 Node *def = n->in(j);
917
918 if (!def || def == n) {
919 continue;
920 }
921
922 // Walk backwards thru projections
923 if (def->is_Proj()) {
924 def = def->in(0);
925 }
926
927 #ifndef PRODUCT
928 if (trace_opto_pipelining()) {
929 tty->print("# in(%2d): ", j);
930 def->dump();
931 }
932 #endif
933
934 // If the defining block is not known, assume it is ok
935 Block *def_block = get_block_for_node(def);
936 uint def_pre_order = def_block ? def_block->_pre_order : 0;
937
938 if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) {
939 continue;
940 }
941
942 uint delta_latency = n->latency(j);
943 uint current_latency = delta_latency + use_latency;
944
945 if (get_latency_for_node(def) < current_latency) {
946 set_latency_for_node(def, current_latency);
947 }
948
949 #ifndef PRODUCT
950 if (trace_opto_pipelining()) {
951 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));
952 }
953 #endif
954 }
955 }
956
957 //------------------------------latency_from_use-------------------------------
958 // Compute the latency of a specific use
959 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
960 // If self-reference, return no latency
961 if (use == n || use->is_Root()) {
962 return 0;
963 }
964
965 uint def_pre_order = get_block_for_node(def)->_pre_order;
966 uint latency = 0;
967
968 // If the use is not a projection, then it is simple...
969 if (!use->is_Proj()) {
970 #ifndef PRODUCT
971 if (trace_opto_pipelining()) {
972 tty->print("# out(): ");
973 use->dump();
974 }
975 #endif
976
977 uint use_pre_order = get_block_for_node(use)->_pre_order;
978
979 if (use_pre_order < def_pre_order)
980 return 0;
981
982 if (use_pre_order == def_pre_order && use->is_Phi())
983 return 0;
984
985 uint nlen = use->len();
986 uint nl = get_latency_for_node(use);
987
988 for ( uint j=0; j<nlen; j++ ) {
989 if (use->in(j) == n) {
990 // Change this if we want local latencies
991 uint ul = use->latency(j);
992 uint l = ul + nl;
993 if (latency < l) latency = l;
994 #ifndef PRODUCT
995 if (trace_opto_pipelining()) {
996 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
997 nl, j, ul, l, latency);
998 }
999 #endif
1000 }
1001 }
1002 } else {
1003 // This is a projection, just grab the latency of the use(s)
1004 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
1005 uint l = latency_from_use(use, def, use->fast_out(j));
1006 if (latency < l) latency = l;
1007 }
1008 }
1009
1010 return latency;
1011 }
1012
1013 //------------------------------latency_from_uses------------------------------
1014 // Compute the latency of this instruction relative to all of it's uses.
1015 // This computes a number that increases as we approach the beginning of the
1016 // routine.
1017 void PhaseCFG::latency_from_uses(Node *n) {
1018 // Set the latency for this instruction
1019 #ifndef PRODUCT
1020 if (trace_opto_pipelining()) {
1021 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1022 dump();
1023 }
1024 #endif
1025 uint latency=0;
1026 const Node *def = n->is_Proj() ? n->in(0): n;
1027
1028 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1029 uint l = latency_from_use(n, def, n->fast_out(i));
1030
1031 if (latency < l) latency = l;
1032 }
1033
1034 set_latency_for_node(n, latency);
1035 }
1036
1037 //------------------------------hoist_to_cheaper_block-------------------------
1038 // Pick a block for node self, between early and LCA, that is a cheaper
1039 // alternative to LCA.
1040 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1041 const double delta = 1+PROB_UNLIKELY_MAG(4);
1042 Block* least = LCA;
1043 double least_freq = least->_freq;
1044 uint target = get_latency_for_node(self);
1045 uint start_latency = get_latency_for_node(LCA->head());
1046 uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx()));
1047 bool in_latency = (target <= start_latency);
1048 const Block* root_block = get_block_for_node(_root);
1049
1050 // Turn off latency scheduling if scheduling is just plain off
1051 if (!C->do_scheduling())
1052 in_latency = true;
1053
1054 // Do not hoist (to cover latency) instructions which target a
1055 // single register. Hoisting stretches the live range of the
1056 // single register and may force spilling.
1057 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1058 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
1059 in_latency = true;
1060
1061 #ifndef PRODUCT
1062 if (trace_opto_pipelining()) {
1063 tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self));
1064 self->dump();
1065 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1066 LCA->_pre_order,
1067 LCA->head()->_idx,
1068 start_latency,
1069 LCA->get_node(LCA->end_idx())->_idx,
1070 end_latency,
1071 least_freq);
1072 }
1073 #endif
1074
1075 int cand_cnt = 0; // number of candidates tried
1076
1077 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1078 // the earliest legal location. Capture the least execution frequency.
1079 while (LCA != early) {
1080 LCA = LCA->_idom; // Follow up the dominator tree
1081
1082 if (LCA == NULL) {
1083 // Bailout without retry
1084 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1085 return least;
1086 }
1087
1088 // Don't hoist machine instructions to the root basic block
1089 if (mach && LCA == root_block)
1090 break;
1091
1092 uint start_lat = get_latency_for_node(LCA->head());
1093 uint end_idx = LCA->end_idx();
1094 uint end_lat = get_latency_for_node(LCA->get_node(end_idx));
1095 double LCA_freq = LCA->_freq;
1096 #ifndef PRODUCT
1097 if (trace_opto_pipelining()) {
1098 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1099 LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq);
1100 }
1101 #endif
1102 cand_cnt++;
1103 if (LCA_freq < least_freq || // Better Frequency
1104 (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
1105 (!StressGCM && // Otherwise, choose with latency
1106 !in_latency && // No block containing latency
1107 LCA_freq < least_freq * delta && // No worse frequency
1108 target >= end_lat && // within latency range
1109 !self->is_iteratively_computed() ) // But don't hoist IV increments
1110 // because they may end up above other uses of their phi forcing
1111 // their result register to be different from their input.
1112 ) {
1113 least = LCA; // Found cheaper block
1114 least_freq = LCA_freq;
1115 start_latency = start_lat;
1116 end_latency = end_lat;
1117 if (target <= start_lat)
1118 in_latency = true;
1119 }
1120 }
1121
1122 #ifndef PRODUCT
1123 if (trace_opto_pipelining()) {
1124 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1125 least->_pre_order, start_latency, least_freq);
1126 }
1127 #endif
1128
1129 // See if the latency needs to be updated
1130 if (target < end_latency) {
1131 #ifndef PRODUCT
1132 if (trace_opto_pipelining()) {
1133 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1134 }
1135 #endif
1136 set_latency_for_node(self, end_latency);
1137 partial_latency_of_defs(self);
1138 }
1139
1140 return least;
1141 }
1142
1143
1144 //------------------------------schedule_late-----------------------------------
1145 // Now schedule all codes as LATE as possible. This is the LCA in the
1146 // dominator tree of all USES of a value. Pick the block with the least
1147 // loop nesting depth that is lowest in the dominator tree.
1148 extern const char must_clone[];
1149 void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) {
1150 #ifndef PRODUCT
1151 if (trace_opto_pipelining())
1152 tty->print("\n#---- schedule_late ----\n");
1153 #endif
1154
1155 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1156 Node *self;
1157
1158 // Walk over all the nodes from last to first
1159 while (self = iter.next()) {
1160 Block* early = get_block_for_node(self); // Earliest legal placement
1161
1162 if (self->is_top()) {
1163 // Top node goes in bb #2 with other constants.
1164 // It must be special-cased, because it has no out edges.
1165 early->add_inst(self);
1166 continue;
1167 }
1168
1169 // No uses, just terminate
1170 if (self->outcnt() == 0) {
1171 assert(self->is_MachProj(), "sanity");
1172 continue; // Must be a dead machine projection
1173 }
1174
1175 // If node is pinned in the block, then no scheduling can be done.
1176 if( self->pinned() ) // Pinned in block?
1177 continue;
1178
1179 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1180 if (mach) {
1181 switch (mach->ideal_Opcode()) {
1182 case Op_CreateEx:
1183 // Don't move exception creation
1184 early->add_inst(self);
1185 continue;
1186 break;
1187 case Op_CheckCastPP:
1188 // Don't move CheckCastPP nodes away from their input, if the input
1189 // is a rawptr (5071820).
1190 Node *def = self->in(1);
1191 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1192 early->add_inst(self);
1193 #ifdef ASSERT
1194 _raw_oops.push(def);
1195 #endif
1196 continue;
1197 }
1198 break;
1199 }
1200 }
1201
1202 // Gather LCA of all uses
1203 Block *LCA = NULL;
1204 {
1205 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1206 // For all uses, find LCA
1207 Node* use = self->fast_out(i);
1208 LCA = raise_LCA_above_use(LCA, use, self, this);
1209 }
1210 } // (Hide defs of imax, i from rest of block.)
1211
1212 // Place temps in the block of their use. This isn't a
1213 // requirement for correctness but it reduces useless
1214 // interference between temps and other nodes.
1215 if (mach != NULL && mach->is_MachTemp()) {
1216 map_node_to_block(self, LCA);
1217 LCA->add_inst(self);
1218 continue;
1219 }
1220
1221 // Check if 'self' could be anti-dependent on memory
1222 if (self->needs_anti_dependence_check()) {
1223 // Hoist LCA above possible-defs and insert anti-dependences to
1224 // defs in new LCA block.
1225 LCA = insert_anti_dependences(LCA, self);
1226 }
1227
1228 if (early->_dom_depth > LCA->_dom_depth) {
1229 // Somehow the LCA has moved above the earliest legal point.
1230 // (One way this can happen is via memory_early_block.)
1231 if (C->subsume_loads() == true && !C->failing()) {
1232 // Retry with subsume_loads == false
1233 // If this is the first failure, the sentinel string will "stick"
1234 // to the Compile object, and the C2Compiler will see it and retry.
1235 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1236 } else {
1237 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1238 C->record_method_not_compilable("late schedule failed: incorrect graph");
1239 }
1240 return;
1241 }
1242
1243 // If there is no opportunity to hoist, then we're done.
1244 // In stress mode, try to hoist even the single operations.
1245 bool try_to_hoist = StressGCM || (LCA != early);
1246
1247 // Must clone guys stay next to use; no hoisting allowed.
1248 // Also cannot hoist guys that alter memory or are otherwise not
1249 // allocatable (hoisting can make a value live longer, leading to
1250 // anti and output dependency problems which are normally resolved
1251 // by the register allocator giving everyone a different register).
1252 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1253 try_to_hoist = false;
1254
1255 Block* late = NULL;
1256 if (try_to_hoist) {
1257 // Now find the block with the least execution frequency.
1258 // Start at the latest schedule and work up to the earliest schedule
1259 // in the dominator tree. Thus the Node will dominate all its uses.
1260 late = hoist_to_cheaper_block(LCA, early, self);
1261 } else {
1262 // Just use the LCA of the uses.
1263 late = LCA;
1264 }
1265
1266 // Put the node into target block
1267 schedule_node_into_block(self, late);
1268
1269 #ifdef ASSERT
1270 if (self->needs_anti_dependence_check()) {
1271 // since precedence edges are only inserted when we're sure they
1272 // are needed make sure that after placement in a block we don't
1273 // need any new precedence edges.
1274 verify_anti_dependences(late, self);
1275 }
1276 #endif
1277 } // Loop until all nodes have been visited
1278
1279 } // end ScheduleLate
1280
1281 //------------------------------GlobalCodeMotion-------------------------------
1282 void PhaseCFG::global_code_motion() {
1283 ResourceMark rm;
1284
1285 #ifndef PRODUCT
1286 if (trace_opto_pipelining()) {
1287 tty->print("\n---- Start GlobalCodeMotion ----\n");
1288 }
1289 #endif
1290
1291 // Initialize the node to block mapping for things on the proj_list
1292 for (uint i = 0; i < _matcher.number_of_projections(); i++) {
1293 unmap_node_from_block(_matcher.get_projection(i));
1294 }
1295
1296 // Set the basic block for Nodes pinned into blocks
1297 Arena* arena = Thread::current()->resource_area();
1298 VectorSet visited(arena);
1299 schedule_pinned_nodes(visited);
1300
1301 // Find the earliest Block any instruction can be placed in. Some
1302 // instructions are pinned into Blocks. Unpinned instructions can
1303 // appear in last block in which all their inputs occur.
1304 visited.Clear();
1305 Node_List stack(arena);
1306 // Pre-grow the list
1307 stack.map((C->unique() >> 1) + 16, NULL);
1308 if (!schedule_early(visited, stack)) {
1309 // Bailout without retry
1310 C->record_method_not_compilable("early schedule failed");
1311 return;
1312 }
1313
1314 // Build Def-Use edges.
1315 // Compute the latency information (via backwards walk) for all the
1316 // instructions in the graph
1317 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1318
1319 if (C->do_scheduling()) {
1320 compute_latencies_backwards(visited, stack);
1321 }
1322
1323 // Now schedule all codes as LATE as possible. This is the LCA in the
1324 // dominator tree of all USES of a value. Pick the block with the least
1325 // loop nesting depth that is lowest in the dominator tree.
1326 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1327 schedule_late(visited, stack);
1328 if (C->failing()) {
1329 // schedule_late fails only when graph is incorrect.
1330 assert(!VerifyGraphEdges, "verification should have failed");
1331 return;
1332 }
1333
1334 #ifndef PRODUCT
1335 if (trace_opto_pipelining()) {
1336 tty->print("\n---- Detect implicit null checks ----\n");
1337 }
1338 #endif
1339
1340 // Detect implicit-null-check opportunities. Basically, find NULL checks
1341 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1342 // I can generate a memory op if there is not one nearby.
1343 if (C->is_method_compilation()) {
1344 // By reversing the loop direction we get a very minor gain on mpegaudio.
1345 // Feel free to revert to a forward loop for clarity.
1346 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1347 for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) {
1348 Node* proj = _matcher._null_check_tests[i];
1349 Node* val = _matcher._null_check_tests[i + 1];
1350 Block* block = get_block_for_node(proj);
1351 implicit_null_check(block, proj, val, C->allowed_deopt_reasons());
1352 // The implicit_null_check will only perform the transformation
1353 // if the null branch is truly uncommon, *and* it leads to an
1354 // uncommon trap. Combined with the too_many_traps guards
1355 // above, this prevents SEGV storms reported in 6366351,
1356 // by recompiling offending methods without this optimization.
1357 }
1358 }
1359
1360 #ifndef PRODUCT
1361 if (trace_opto_pipelining()) {
1362 tty->print("\n---- Start Local Scheduling ----\n");
1363 }
1364 #endif
1365
1366 // Schedule locally. Right now a simple topological sort.
1367 // Later, do a real latency aware scheduler.
1368 GrowableArray<int> ready_cnt(C->unique(), C->unique(), -1);
1369 visited.Clear();
1370 for (uint i = 0; i < number_of_blocks(); i++) {
1371 Block* block = get_block(i);
1372 if (!schedule_local(block, ready_cnt, visited)) {
1373 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1374 C->record_method_not_compilable("local schedule failed");
1375 }
1376 return;
1377 }
1378 }
1379
1380 // If we inserted any instructions between a Call and his CatchNode,
1381 // clone the instructions on all paths below the Catch.
1382 for (uint i = 0; i < number_of_blocks(); i++) {
1383 Block* block = get_block(i);
1384 call_catch_cleanup(block);
1385 }
1386
1387 #ifndef PRODUCT
1388 if (trace_opto_pipelining()) {
1389 tty->print("\n---- After GlobalCodeMotion ----\n");
1390 for (uint i = 0; i < number_of_blocks(); i++) {
1391 Block* block = get_block(i);
1392 block->dump();
1393 }
1394 }
1395 #endif
1396 // Dead.
1397 _node_latency = (GrowableArray<uint> *)0xdeadbeef;
1398 }
1399
1400 bool PhaseCFG::do_global_code_motion() {
1401
1402 build_dominator_tree();
1403 if (C->failing()) {
1404 return false;
1405 }
1406
1407 NOT_PRODUCT( C->verify_graph_edges(); )
1408
1409 estimate_block_frequency();
1410
1411 global_code_motion();
1412
1413 if (C->failing()) {
1414 return false;
1415 }
1416
1417 return true;
1418 }
1419
1420 //------------------------------Estimate_Block_Frequency-----------------------
1421 // Estimate block frequencies based on IfNode probabilities.
1422 void PhaseCFG::estimate_block_frequency() {
1423
1424 // Force conditional branches leading to uncommon traps to be unlikely,
1425 // not because we get to the uncommon_trap with less relative frequency,
1426 // but because an uncommon_trap typically causes a deopt, so we only get
1427 // there once.
1428 if (C->do_freq_based_layout()) {
1429 Block_List worklist;
1430 Block* root_blk = get_block(0);
1431 for (uint i = 1; i < root_blk->num_preds(); i++) {
1432 Block *pb = get_block_for_node(root_blk->pred(i));
1433 if (pb->has_uncommon_code()) {
1434 worklist.push(pb);
1435 }
1436 }
1437 while (worklist.size() > 0) {
1438 Block* uct = worklist.pop();
1439 if (uct == get_root_block()) {
1440 continue;
1441 }
1442 for (uint i = 1; i < uct->num_preds(); i++) {
1443 Block *pb = get_block_for_node(uct->pred(i));
1444 if (pb->_num_succs == 1) {
1445 worklist.push(pb);
1446 } else if (pb->num_fall_throughs() == 2) {
1447 pb->update_uncommon_branch(uct);
1448 }
1449 }
1450 }
1451 }
1452
1453 // Create the loop tree and calculate loop depth.
1454 _root_loop = create_loop_tree();
1455 _root_loop->compute_loop_depth(0);
1456
1457 // Compute block frequency of each block, relative to a single loop entry.
1458 _root_loop->compute_freq();
1459
1460 // Adjust all frequencies to be relative to a single method entry
1461 _root_loop->_freq = 1.0;
1462 _root_loop->scale_freq();
1463
1464 // Save outmost loop frequency for LRG frequency threshold
1465 _outer_loop_frequency = _root_loop->outer_loop_freq();
1466
1467 // force paths ending at uncommon traps to be infrequent
1468 if (!C->do_freq_based_layout()) {
1469 Block_List worklist;
1470 Block* root_blk = get_block(0);
1471 for (uint i = 1; i < root_blk->num_preds(); i++) {
1472 Block *pb = get_block_for_node(root_blk->pred(i));
1473 if (pb->has_uncommon_code()) {
1474 worklist.push(pb);
1475 }
1476 }
1477 while (worklist.size() > 0) {
1478 Block* uct = worklist.pop();
1479 uct->_freq = PROB_MIN;
1480 for (uint i = 1; i < uct->num_preds(); i++) {
1481 Block *pb = get_block_for_node(uct->pred(i));
1482 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1483 worklist.push(pb);
1484 }
1485 }
1486 }
1487 }
1488
1489 #ifdef ASSERT
1490 for (uint i = 0; i < number_of_blocks(); i++) {
1491 Block* b = get_block(i);
1492 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
1493 }
1494 #endif
1495
1496 #ifndef PRODUCT
1497 if (PrintCFGBlockFreq) {
1498 tty->print_cr("CFG Block Frequencies");
1499 _root_loop->dump_tree();
1500 if (Verbose) {
1501 tty->print_cr("PhaseCFG dump");
1502 dump();
1503 tty->print_cr("Node dump");
1504 _root->dump(99999);
1505 }
1506 }
1507 #endif
1508 }
1509
1510 //----------------------------create_loop_tree--------------------------------
1511 // Create a loop tree from the CFG
1512 CFGLoop* PhaseCFG::create_loop_tree() {
1513
1514 #ifdef ASSERT
1515 assert(get_block(0) == get_root_block(), "first block should be root block");
1516 for (uint i = 0; i < number_of_blocks(); i++) {
1517 Block* block = get_block(i);
1518 // Check that _loop field are clear...we could clear them if not.
1519 assert(block->_loop == NULL, "clear _loop expected");
1520 // Sanity check that the RPO numbering is reflected in the _blocks array.
1521 // It doesn't have to be for the loop tree to be built, but if it is not,
1522 // then the blocks have been reordered since dom graph building...which
1523 // may question the RPO numbering
1524 assert(block->_rpo == i, "unexpected reverse post order number");
1525 }
1526 #endif
1527
1528 int idct = 0;
1529 CFGLoop* root_loop = new CFGLoop(idct++);
1530
1531 Block_List worklist;
1532
1533 // Assign blocks to loops
1534 for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block
1535 Block* block = get_block(i);
1536
1537 if (block->head()->is_Loop()) {
1538 Block* loop_head = block;
1539 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1540 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1541 Block* tail = get_block_for_node(tail_n);
1542
1543 // Defensively filter out Loop nodes for non-single-entry loops.
1544 // For all reasonable loops, the head occurs before the tail in RPO.
1545 if (i <= tail->_rpo) {
1546
1547 // The tail and (recursive) predecessors of the tail
1548 // are made members of a new loop.
1549
1550 assert(worklist.size() == 0, "nonempty worklist");
1551 CFGLoop* nloop = new CFGLoop(idct++);
1552 assert(loop_head->_loop == NULL, "just checking");
1553 loop_head->_loop = nloop;
1554 // Add to nloop so push_pred() will skip over inner loops
1555 nloop->add_member(loop_head);
1556 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this);
1557
1558 while (worklist.size() > 0) {
1559 Block* member = worklist.pop();
1560 if (member != loop_head) {
1561 for (uint j = 1; j < member->num_preds(); j++) {
1562 nloop->push_pred(member, j, worklist, this);
1563 }
1564 }
1565 }
1566 }
1567 }
1568 }
1569
1570 // Create a member list for each loop consisting
1571 // of both blocks and (immediate child) loops.
1572 for (uint i = 0; i < number_of_blocks(); i++) {
1573 Block* block = get_block(i);
1574 CFGLoop* lp = block->_loop;
1575 if (lp == NULL) {
1576 // Not assigned to a loop. Add it to the method's pseudo loop.
1577 block->_loop = root_loop;
1578 lp = root_loop;
1579 }
1580 if (lp == root_loop || block != lp->head()) { // loop heads are already members
1581 lp->add_member(block);
1582 }
1583 if (lp != root_loop) {
1584 if (lp->parent() == NULL) {
1585 // Not a nested loop. Make it a child of the method's pseudo loop.
1586 root_loop->add_nested_loop(lp);
1587 }
1588 if (block == lp->head()) {
1589 // Add nested loop to member list of parent loop.
1590 lp->parent()->add_member(lp);
1591 }
1592 }
1593 }
1594
1595 return root_loop;
1596 }
1597
1598 //------------------------------push_pred--------------------------------------
1599 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) {
1600 Node* pred_n = blk->pred(i);
1601 Block* pred = cfg->get_block_for_node(pred_n);
1602 CFGLoop *pred_loop = pred->_loop;
1603 if (pred_loop == NULL) {
1604 // Filter out blocks for non-single-entry loops.
1605 // For all reasonable loops, the head occurs before the tail in RPO.
1606 if (pred->_rpo > head()->_rpo) {
1607 pred->_loop = this;
1608 worklist.push(pred);
1609 }
1610 } else if (pred_loop != this) {
1611 // Nested loop.
1612 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1613 pred_loop = pred_loop->_parent;
1614 }
1615 // Make pred's loop be a child
1616 if (pred_loop->_parent == NULL) {
1617 add_nested_loop(pred_loop);
1618 // Continue with loop entry predecessor.
1619 Block* pred_head = pred_loop->head();
1620 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1621 assert(pred_head != head(), "loop head in only one loop");
1622 push_pred(pred_head, LoopNode::EntryControl, worklist, cfg);
1623 } else {
1624 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1625 }
1626 }
1627 }
1628
1629 //------------------------------add_nested_loop--------------------------------
1630 // Make cl a child of the current loop in the loop tree.
1631 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1632 assert(_parent == NULL, "no parent yet");
1633 assert(cl != this, "not my own parent");
1634 cl->_parent = this;
1635 CFGLoop* ch = _child;
1636 if (ch == NULL) {
1637 _child = cl;
1638 } else {
1639 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1640 ch->_sibling = cl;
1641 }
1642 }
1643
1644 //------------------------------compute_loop_depth-----------------------------
1645 // Store the loop depth in each CFGLoop object.
1646 // Recursively walk the children to do the same for them.
1647 void CFGLoop::compute_loop_depth(int depth) {
1648 _depth = depth;
1649 CFGLoop* ch = _child;
1650 while (ch != NULL) {
1651 ch->compute_loop_depth(depth + 1);
1652 ch = ch->_sibling;
1653 }
1654 }
1655
1656 //------------------------------compute_freq-----------------------------------
1657 // Compute the frequency of each block and loop, relative to a single entry
1658 // into the dominating loop head.
1659 void CFGLoop::compute_freq() {
1660 // Bottom up traversal of loop tree (visit inner loops first.)
1661 // Set loop head frequency to 1.0, then transitively
1662 // compute frequency for all successors in the loop,
1663 // as well as for each exit edge. Inner loops are
1664 // treated as single blocks with loop exit targets
1665 // as the successor blocks.
1666
1667 // Nested loops first
1668 CFGLoop* ch = _child;
1669 while (ch != NULL) {
1670 ch->compute_freq();
1671 ch = ch->_sibling;
1672 }
1673 assert (_members.length() > 0, "no empty loops");
1674 Block* hd = head();
1675 hd->_freq = 1.0;
1676 for (int i = 0; i < _members.length(); i++) {
1677 CFGElement* s = _members.at(i);
1678 double freq = s->_freq;
1679 if (s->is_block()) {
1680 Block* b = s->as_Block();
1681 for (uint j = 0; j < b->_num_succs; j++) {
1682 Block* sb = b->_succs[j];
1683 update_succ_freq(sb, freq * b->succ_prob(j));
1684 }
1685 } else {
1686 CFGLoop* lp = s->as_CFGLoop();
1687 assert(lp->_parent == this, "immediate child");
1688 for (int k = 0; k < lp->_exits.length(); k++) {
1689 Block* eb = lp->_exits.at(k).get_target();
1690 double prob = lp->_exits.at(k).get_prob();
1691 update_succ_freq(eb, freq * prob);
1692 }
1693 }
1694 }
1695
1696 // For all loops other than the outer, "method" loop,
1697 // sum and normalize the exit probability. The "method" loop
1698 // should keep the initial exit probability of 1, so that
1699 // inner blocks do not get erroneously scaled.
1700 if (_depth != 0) {
1701 // Total the exit probabilities for this loop.
1702 double exits_sum = 0.0f;
1703 for (int i = 0; i < _exits.length(); i++) {
1704 exits_sum += _exits.at(i).get_prob();
1705 }
1706
1707 // Normalize the exit probabilities. Until now, the
1708 // probabilities estimate the possibility of exit per
1709 // a single loop iteration; afterward, they estimate
1710 // the probability of exit per loop entry.
1711 for (int i = 0; i < _exits.length(); i++) {
1712 Block* et = _exits.at(i).get_target();
1713 float new_prob = 0.0f;
1714 if (_exits.at(i).get_prob() > 0.0f) {
1715 new_prob = _exits.at(i).get_prob() / exits_sum;
1716 }
1717 BlockProbPair bpp(et, new_prob);
1718 _exits.at_put(i, bpp);
1719 }
1720
1721 // Save the total, but guard against unreasonable probability,
1722 // as the value is used to estimate the loop trip count.
1723 // An infinite trip count would blur relative block
1724 // frequencies.
1725 if (exits_sum > 1.0f) exits_sum = 1.0;
1726 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1727 _exit_prob = exits_sum;
1728 }
1729 }
1730
1731 //------------------------------succ_prob-------------------------------------
1732 // Determine the probability of reaching successor 'i' from the receiver block.
1733 float Block::succ_prob(uint i) {
1734 int eidx = end_idx();
1735 Node *n = get_node(eidx); // Get ending Node
1736
1737 int op = n->Opcode();
1738 if (n->is_Mach()) {
1739 if (n->is_MachNullCheck()) {
1740 // Can only reach here if called after lcm. The original Op_If is gone,
1741 // so we attempt to infer the probability from one or both of the
1742 // successor blocks.
1743 assert(_num_succs == 2, "expecting 2 successors of a null check");
1744 // If either successor has only one predecessor, then the
1745 // probability estimate can be derived using the
1746 // relative frequency of the successor and this block.
1747 if (_succs[i]->num_preds() == 2) {
1748 return _succs[i]->_freq / _freq;
1749 } else if (_succs[1-i]->num_preds() == 2) {
1750 return 1 - (_succs[1-i]->_freq / _freq);
1751 } else {
1752 // Estimate using both successor frequencies
1753 float freq = _succs[i]->_freq;
1754 return freq / (freq + _succs[1-i]->_freq);
1755 }
1756 }
1757 op = n->as_Mach()->ideal_Opcode();
1758 }
1759
1760
1761 // Switch on branch type
1762 switch( op ) {
1763 case Op_CountedLoopEnd:
1764 case Op_If: {
1765 assert (i < 2, "just checking");
1766 // Conditionals pass on only part of their frequency
1767 float prob = n->as_MachIf()->_prob;
1768 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1769 // If succ[i] is the FALSE branch, invert path info
1770 if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) {
1771 return 1.0f - prob; // not taken
1772 } else {
1773 return prob; // taken
1774 }
1775 }
1776
1777 case Op_Jump:
1778 // Divide the frequency between all successors evenly
1779 return 1.0f/_num_succs;
1780
1781 case Op_Catch: {
1782 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1783 if (ci->_con == CatchProjNode::fall_through_index) {
1784 // Fall-thru path gets the lion's share.
1785 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1786 } else {
1787 // Presume exceptional paths are equally unlikely
1788 return PROB_UNLIKELY_MAG(5);
1789 }
1790 }
1791
1792 case Op_Root:
1793 case Op_Goto:
1794 // Pass frequency straight thru to target
1795 return 1.0f;
1796
1797 case Op_NeverBranch:
1798 return 0.0f;
1799
1800 case Op_TailCall:
1801 case Op_TailJump:
1802 case Op_Return:
1803 case Op_Halt:
1804 case Op_Rethrow:
1805 // Do not push out freq to root block
1806 return 0.0f;
1807
1808 default:
1809 ShouldNotReachHere();
1810 }
1811
1812 return 0.0f;
1813 }
1814
1815 //------------------------------num_fall_throughs-----------------------------
1816 // Return the number of fall-through candidates for a block
1817 int Block::num_fall_throughs() {
1818 int eidx = end_idx();
1819 Node *n = get_node(eidx); // Get ending Node
1820
1821 int op = n->Opcode();
1822 if (n->is_Mach()) {
1823 if (n->is_MachNullCheck()) {
1824 // In theory, either side can fall-thru, for simplicity sake,
1825 // let's say only the false branch can now.
1826 return 1;
1827 }
1828 op = n->as_Mach()->ideal_Opcode();
1829 }
1830
1831 // Switch on branch type
1832 switch( op ) {
1833 case Op_CountedLoopEnd:
1834 case Op_If:
1835 return 2;
1836
1837 case Op_Root:
1838 case Op_Goto:
1839 return 1;
1840
1841 case Op_Catch: {
1842 for (uint i = 0; i < _num_succs; i++) {
1843 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1844 if (ci->_con == CatchProjNode::fall_through_index) {
1845 return 1;
1846 }
1847 }
1848 return 0;
1849 }
1850
1851 case Op_Jump:
1852 case Op_NeverBranch:
1853 case Op_TailCall:
1854 case Op_TailJump:
1855 case Op_Return:
1856 case Op_Halt:
1857 case Op_Rethrow:
1858 return 0;
1859
1860 default:
1861 ShouldNotReachHere();
1862 }
1863
1864 return 0;
1865 }
1866
1867 //------------------------------succ_fall_through-----------------------------
1868 // Return true if a specific successor could be fall-through target.
1869 bool Block::succ_fall_through(uint i) {
1870 int eidx = end_idx();
1871 Node *n = get_node(eidx); // Get ending Node
1872
1873 int op = n->Opcode();
1874 if (n->is_Mach()) {
1875 if (n->is_MachNullCheck()) {
1876 // In theory, either side can fall-thru, for simplicity sake,
1877 // let's say only the false branch can now.
1878 return get_node(i + eidx + 1)->Opcode() == Op_IfFalse;
1879 }
1880 op = n->as_Mach()->ideal_Opcode();
1881 }
1882
1883 // Switch on branch type
1884 switch( op ) {
1885 case Op_CountedLoopEnd:
1886 case Op_If:
1887 case Op_Root:
1888 case Op_Goto:
1889 return true;
1890
1891 case Op_Catch: {
1892 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1893 return ci->_con == CatchProjNode::fall_through_index;
1894 }
1895
1896 case Op_Jump:
1897 case Op_NeverBranch:
1898 case Op_TailCall:
1899 case Op_TailJump:
1900 case Op_Return:
1901 case Op_Halt:
1902 case Op_Rethrow:
1903 return false;
1904
1905 default:
1906 ShouldNotReachHere();
1907 }
1908
1909 return false;
1910 }
1911
1912 //------------------------------update_uncommon_branch------------------------
1913 // Update the probability of a two-branch to be uncommon
1914 void Block::update_uncommon_branch(Block* ub) {
1915 int eidx = end_idx();
1916 Node *n = get_node(eidx); // Get ending Node
1917
1918 int op = n->as_Mach()->ideal_Opcode();
1919
1920 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
1921 assert(num_fall_throughs() == 2, "must be a two way branch block");
1922
1923 // Which successor is ub?
1924 uint s;
1925 for (s = 0; s <_num_succs; s++) {
1926 if (_succs[s] == ub) break;
1927 }
1928 assert(s < 2, "uncommon successor must be found");
1929
1930 // If ub is the true path, make the proability small, else
1931 // ub is the false path, and make the probability large
1932 bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse);
1933
1934 // Get existing probability
1935 float p = n->as_MachIf()->_prob;
1936
1937 if (invert) p = 1.0 - p;
1938 if (p > PROB_MIN) {
1939 p = PROB_MIN;
1940 }
1941 if (invert) p = 1.0 - p;
1942
1943 n->as_MachIf()->_prob = p;
1944 }
1945
1946 //------------------------------update_succ_freq-------------------------------
1947 // Update the appropriate frequency associated with block 'b', a successor of
1948 // a block in this loop.
1949 void CFGLoop::update_succ_freq(Block* b, double freq) {
1950 if (b->_loop == this) {
1951 if (b == head()) {
1952 // back branch within the loop
1953 // Do nothing now, the loop carried frequency will be
1954 // adjust later in scale_freq().
1955 } else {
1956 // simple branch within the loop
1957 b->_freq += freq;
1958 }
1959 } else if (!in_loop_nest(b)) {
1960 // branch is exit from this loop
1961 BlockProbPair bpp(b, freq);
1962 _exits.append(bpp);
1963 } else {
1964 // branch into nested loop
1965 CFGLoop* ch = b->_loop;
1966 ch->_freq += freq;
1967 }
1968 }
1969
1970 //------------------------------in_loop_nest-----------------------------------
1971 // Determine if block b is in the receiver's loop nest.
1972 bool CFGLoop::in_loop_nest(Block* b) {
1973 int depth = _depth;
1974 CFGLoop* b_loop = b->_loop;
1975 int b_depth = b_loop->_depth;
1976 if (depth == b_depth) {
1977 return true;
1978 }
1979 while (b_depth > depth) {
1980 b_loop = b_loop->_parent;
1981 b_depth = b_loop->_depth;
1982 }
1983 return b_loop == this;
1984 }
1985
1986 //------------------------------scale_freq-------------------------------------
1987 // Scale frequency of loops and blocks by trip counts from outer loops
1988 // Do a top down traversal of loop tree (visit outer loops first.)
1989 void CFGLoop::scale_freq() {
1990 double loop_freq = _freq * trip_count();
1991 _freq = loop_freq;
1992 for (int i = 0; i < _members.length(); i++) {
1993 CFGElement* s = _members.at(i);
1994 double block_freq = s->_freq * loop_freq;
1995 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
1996 block_freq = MIN_BLOCK_FREQUENCY;
1997 s->_freq = block_freq;
1998 }
1999 CFGLoop* ch = _child;
2000 while (ch != NULL) {
2001 ch->scale_freq();
2002 ch = ch->_sibling;
2003 }
2004 }
2005
2006 // Frequency of outer loop
2007 double CFGLoop::outer_loop_freq() const {
2008 if (_child != NULL) {
2009 return _child->_freq;
2010 }
2011 return _freq;
2012 }
2013
2014 #ifndef PRODUCT
2015 //------------------------------dump_tree--------------------------------------
2016 void CFGLoop::dump_tree() const {
2017 dump();
2018 if (_child != NULL) _child->dump_tree();
2019 if (_sibling != NULL) _sibling->dump_tree();
2020 }
2021
2022 //------------------------------dump-------------------------------------------
2023 void CFGLoop::dump() const {
2024 for (int i = 0; i < _depth; i++) tty->print(" ");
2025 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
2026 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
2027 for (int i = 0; i < _depth; i++) tty->print(" ");
2028 tty->print(" members:");
2029 int k = 0;
2030 for (int i = 0; i < _members.length(); i++) {
2031 if (k++ >= 6) {
2032 tty->print("\n ");
2033 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2034 k = 0;
2035 }
2036 CFGElement *s = _members.at(i);
2037 if (s->is_block()) {
2038 Block *b = s->as_Block();
2039 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
2040 } else {
2041 CFGLoop* lp = s->as_CFGLoop();
2042 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
2043 }
2044 }
2045 tty->print("\n");
2046 for (int i = 0; i < _depth; i++) tty->print(" ");
2047 tty->print(" exits: ");
2048 k = 0;
2049 for (int i = 0; i < _exits.length(); i++) {
2050 if (k++ >= 7) {
2051 tty->print("\n ");
2052 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2053 k = 0;
2054 }
2055 Block *blk = _exits.at(i).get_target();
2056 double prob = _exits.at(i).get_prob();
2057 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2058 }
2059 tty->print("\n");
2060 }
2061 #endif