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