1 /*
2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "libadt/vectset.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "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 #if defined AD_MD_HPP
39 # include AD_MD_HPP
40 #elif defined TARGET_ARCH_MODEL_x86_32
41 # include "adfiles/ad_x86_32.hpp"
42 #elif defined TARGET_ARCH_MODEL_x86_64
43 # include "adfiles/ad_x86_64.hpp"
44 #elif defined TARGET_ARCH_MODEL_aarch64
45 # include "adfiles/ad_aarch64.hpp"
46 #elif defined TARGET_ARCH_MODEL_sparc
47 # include "adfiles/ad_sparc.hpp"
48 #elif defined TARGET_ARCH_MODEL_zero
49 # include "adfiles/ad_zero.hpp"
50 #elif defined TARGET_ARCH_MODEL_ppc_64
51 # include "adfiles/ad_ppc_64.hpp"
52 #endif
53
54
55 // Portions of code courtesy of Clifford Click
56
57 // Optimization - Graph Style
58
59 // To avoid float value underflow
60 #define MIN_BLOCK_FREQUENCY 1.e-35f
61
62 //----------------------------schedule_node_into_block-------------------------
63 // Insert node n into block b. Look for projections of n and make sure they
64 // are in b also.
65 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
66 // Set basic block of n, Add n to b,
67 map_node_to_block(n, b);
68 b->add_inst(n);
69
70 // After Matching, nearly any old Node may have projections trailing it.
71 // These are usually machine-dependent flags. In any case, they might
72 // float to another block below this one. Move them up.
73 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
74 Node* use = n->fast_out(i);
75 if (use->is_Proj()) {
76 Block* buse = get_block_for_node(use);
77 if (buse != b) { // In wrong block?
78 if (buse != NULL) {
79 buse->find_remove(use); // Remove from wrong block
80 }
81 map_node_to_block(use, b);
82 b->add_inst(use);
83 }
84 }
85 }
86 }
87
88 //----------------------------replace_block_proj_ctrl-------------------------
89 // Nodes that have is_block_proj() nodes as their control need to use
90 // the appropriate Region for their actual block as their control since
91 // the projection will be in a predecessor block.
92 void PhaseCFG::replace_block_proj_ctrl( Node *n ) {
93 const Node *in0 = n->in(0);
94 assert(in0 != NULL, "Only control-dependent");
95 const Node *p = in0->is_block_proj();
96 if (p != NULL && p != n) { // Control from a block projection?
97 assert(!n->pinned() || n->is_MachConstantBase(), "only pinned MachConstantBase node is expected here");
98 // Find trailing Region
99 Block *pb = get_block_for_node(in0); // Block-projection already has basic block
100 uint j = 0;
101 if (pb->_num_succs != 1) { // More then 1 successor?
102 // Search for successor
103 uint max = pb->number_of_nodes();
104 assert( max > 1, "" );
105 uint start = max - pb->_num_succs;
106 // Find which output path belongs to projection
107 for (j = start; j < max; j++) {
108 if( pb->get_node(j) == in0 )
109 break;
110 }
111 assert( j < max, "must find" );
112 // Change control to match head of successor basic block
113 j -= start;
114 }
115 n->set_req(0, pb->_succs[j]->head());
116 }
117 }
118
119
120 static bool is_dominator(Block* d, Block* n) {
121 return d->dom_lca(n) == d;
122 }
123 //------------------------------schedule_pinned_nodes--------------------------
124 // Set the basic block for Nodes pinned into blocks
125 void PhaseCFG::schedule_pinned_nodes(VectorSet &visited) {
126 // Allocate node stack of size C->live_nodes()+8 to avoid frequent realloc
127 GrowableArray <Node *> spstack(C->live_nodes() + 8);
128 spstack.push(_root);
129 while (spstack.is_nonempty()) {
130 Node* node = spstack.pop();
131 if (!visited.test_set(node->_idx)) { // Test node and flag it as visited
132 if (node->pinned() && !has_block(node)) { // Pinned? Nail it down!
133 assert(node->in(0), "pinned Node must have Control");
134 // Before setting block replace block_proj control edge
135 replace_block_proj_ctrl(node);
136 Node* input = node->in(0);
137 while (!input->is_block_start()) {
138 input = input->in(0);
139 }
140 Block* block = get_block_for_node(input); // Basic block of controlling input
141 schedule_node_into_block(node, block);
142 }
143 // If the node has precedence edges (added when CastPP nodes are
144 // removed in final_graph_reshaping), fix the control of the
145 // node to cover the precedence edges and remove the
146 // dependencies.
147 Node* n = NULL;
148 for (uint i = node->len()-1; i >= node->req(); i--) {
149 Node* m = node->in(i);
150 if (m == NULL) continue;
151 // Skip the precedence edge if the test that guarded a CastPP:
152 // - was optimized out during escape analysis
153 // (OptimizePtrCompare): the CastPP's control isn't an end of
154 // block.
155 // - is moved in the branch of a dominating If: the control of
156 // the CastPP is then a Region.
157 if (m->is_block_proj() || m->is_block_start()) {
158 node->rm_prec(i);
159 if (n == NULL) {
160 n = m;
161 } else {
162 Block* bn = get_block_for_node(n);
163 Block* bm = get_block_for_node(m);
164 assert(is_dominator(bn, bm) || is_dominator(bm, bn), "one must dominate the other");
165 n = is_dominator(bn, bm) ? m : n;
166 }
167 }
168 }
169 if (n != NULL) {
170 assert(node->in(0), "control should have been set");
171 Block* bn = get_block_for_node(n);
172 Block* bnode = get_block_for_node(node->in(0));
173 assert(is_dominator(bn, bnode) || is_dominator(bnode, bn), "one must dominate the other");
174 if (!is_dominator(bn, bnode)) {
175 node->set_req(0, n);
176 }
177 }
178
179 // process all inputs that are non NULL
180 for (int i = node->req() - 1; i >= 0; --i) {
181 if (node->in(i) != NULL) {
182 spstack.push(node->in(i));
183 }
184 }
185 }
186 }
187 }
188
189 #ifdef ASSERT
190 // Assert that new input b2 is dominated by all previous inputs.
191 // Check this by by seeing that it is dominated by b1, the deepest
192 // input observed until b2.
193 static void assert_dom(Block* b1, Block* b2, Node* n, const PhaseCFG* cfg) {
194 if (b1 == NULL) return;
195 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
196 Block* tmp = b2;
197 while (tmp != b1 && tmp != NULL) {
198 tmp = tmp->_idom;
199 }
200 if (tmp != b1) {
201 // Detected an unschedulable graph. Print some nice stuff and die.
202 tty->print_cr("!!! Unschedulable graph !!!");
203 for (uint j=0; j<n->len(); j++) { // For all inputs
204 Node* inn = n->in(j); // Get input
205 if (inn == NULL) continue; // Ignore NULL, missing inputs
206 Block* inb = cfg->get_block_for_node(inn);
207 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
208 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
209 inn->dump();
210 }
211 tty->print("Failing node: ");
212 n->dump();
213 assert(false, "unscheduable graph");
214 }
215 }
216 #endif
217
218 static Block* find_deepest_input(Node* n, const PhaseCFG* cfg) {
219 // Find the last input dominated by all other inputs.
220 Block* deepb = NULL; // Deepest block so far
221 int deepb_dom_depth = 0;
222 for (uint k = 0; k < n->len(); k++) { // For all inputs
223 Node* inn = n->in(k); // Get input
224 if (inn == NULL) continue; // Ignore NULL, missing inputs
225 Block* inb = cfg->get_block_for_node(inn);
226 assert(inb != NULL, "must already have scheduled this input");
227 if (deepb_dom_depth < (int) inb->_dom_depth) {
228 // The new inb must be dominated by the previous deepb.
229 // The various inputs must be linearly ordered in the dom
230 // tree, or else there will not be a unique deepest block.
231 DEBUG_ONLY(assert_dom(deepb, inb, n, cfg));
232 deepb = inb; // Save deepest block
233 deepb_dom_depth = deepb->_dom_depth;
234 }
235 }
236 assert(deepb != NULL, "must be at least one input to n");
237 return deepb;
238 }
239
240
241 //------------------------------schedule_early---------------------------------
242 // Find the earliest Block any instruction can be placed in. Some instructions
243 // are pinned into Blocks. Unpinned instructions can appear in last block in
244 // which all their inputs occur.
245 bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) {
246 // Allocate stack with enough space to avoid frequent realloc
247 Node_Stack nstack(roots.Size() + 8);
248 // _root will be processed among C->top() inputs
249 roots.push(C->top());
250 visited.set(C->top()->_idx);
251
252 while (roots.size() != 0) {
253 // Use local variables nstack_top_n & nstack_top_i to cache values
254 // on stack's top.
255 Node* parent_node = roots.pop();
256 uint input_index = 0;
257
258 while (true) {
259 if (input_index == 0) {
260 // Fixup some control. Constants without control get attached
261 // to root and nodes that use is_block_proj() nodes should be attached
262 // to the region that starts their block.
263 const Node* control_input = parent_node->in(0);
264 if (control_input != NULL) {
265 replace_block_proj_ctrl(parent_node);
266 } else {
267 // Is a constant with NO inputs?
268 if (parent_node->req() == 1) {
269 parent_node->set_req(0, _root);
270 }
271 }
272 }
273
274 // First, visit all inputs and force them to get a block. If an
275 // input is already in a block we quit following inputs (to avoid
276 // cycles). Instead we put that Node on a worklist to be handled
277 // later (since IT'S inputs may not have a block yet).
278
279 // Assume all n's inputs will be processed
280 bool done = true;
281
282 while (input_index < parent_node->len()) {
283 Node* in = parent_node->in(input_index++);
284 if (in == NULL) {
285 continue;
286 }
287
288 int is_visited = visited.test_set(in->_idx);
289 if (!has_block(in)) {
290 if (is_visited) {
291 assert(false, "graph should be schedulable");
292 return false;
293 }
294 // Save parent node and next input's index.
295 nstack.push(parent_node, input_index);
296 // Process current input now.
297 parent_node = in;
298 input_index = 0;
299 // Not all n's inputs processed.
300 done = false;
301 break;
302 } else if (!is_visited) {
303 // Visit this guy later, using worklist
304 roots.push(in);
305 }
306 }
307
308 if (done) {
309 // All of n's inputs have been processed, complete post-processing.
310
311 // Some instructions are pinned into a block. These include Region,
312 // Phi, Start, Return, and other control-dependent instructions and
313 // any projections which depend on them.
314 if (!parent_node->pinned()) {
315 // Set earliest legal block.
316 Block* earliest_block = find_deepest_input(parent_node, this);
317 map_node_to_block(parent_node, earliest_block);
318 } else {
319 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");
320 }
321
322 if (nstack.is_empty()) {
323 // Finished all nodes on stack.
324 // Process next node on the worklist 'roots'.
325 break;
326 }
327 // Get saved parent node and next input's index.
328 parent_node = nstack.node();
329 input_index = nstack.index();
330 nstack.pop();
331 }
332 }
333 }
334 return true;
335 }
336
337 //------------------------------dom_lca----------------------------------------
338 // Find least common ancestor in dominator tree
339 // LCA is a current notion of LCA, to be raised above 'this'.
340 // As a convenient boundary condition, return 'this' if LCA is NULL.
341 // Find the LCA of those two nodes.
342 Block* Block::dom_lca(Block* LCA) {
343 if (LCA == NULL || LCA == this) return this;
344
345 Block* anc = this;
346 while (anc->_dom_depth > LCA->_dom_depth)
347 anc = anc->_idom; // Walk up till anc is as high as LCA
348
349 while (LCA->_dom_depth > anc->_dom_depth)
350 LCA = LCA->_idom; // Walk up till LCA is as high as anc
351
352 while (LCA != anc) { // Walk both up till they are the same
353 LCA = LCA->_idom;
354 anc = anc->_idom;
355 }
356
357 return LCA;
358 }
359
360 //--------------------------raise_LCA_above_use--------------------------------
361 // We are placing a definition, and have been given a def->use edge.
362 // The definition must dominate the use, so move the LCA upward in the
363 // dominator tree to dominate the use. If the use is a phi, adjust
364 // the LCA only with the phi input paths which actually use this def.
365 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) {
366 Block* buse = cfg->get_block_for_node(use);
367 if (buse == NULL) return LCA; // Unused killing Projs have no use block
368 if (!use->is_Phi()) return buse->dom_lca(LCA);
369 uint pmax = use->req(); // Number of Phi inputs
370 // Why does not this loop just break after finding the matching input to
371 // the Phi? Well...it's like this. I do not have true def-use/use-def
372 // chains. Means I cannot distinguish, from the def-use direction, which
373 // of many use-defs lead from the same use to the same def. That is, this
374 // Phi might have several uses of the same def. Each use appears in a
375 // different predecessor block. But when I enter here, I cannot distinguish
376 // which use-def edge I should find the predecessor block for. So I find
377 // them all. Means I do a little extra work if a Phi uses the same value
378 // more than once.
379 for (uint j=1; j<pmax; j++) { // For all inputs
380 if (use->in(j) == def) { // Found matching input?
381 Block* pred = cfg->get_block_for_node(buse->pred(j));
382 LCA = pred->dom_lca(LCA);
383 }
384 }
385 return LCA;
386 }
387
388 //----------------------------raise_LCA_above_marks----------------------------
389 // Return a new LCA that dominates LCA and any of its marked predecessors.
390 // Search all my parents up to 'early' (exclusive), looking for predecessors
391 // which are marked with the given index. Return the LCA (in the dom tree)
392 // of all marked blocks. If there are none marked, return the original
393 // LCA.
394 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) {
395 Block_List worklist;
396 worklist.push(LCA);
397 while (worklist.size() > 0) {
398 Block* mid = worklist.pop();
399 if (mid == early) continue; // stop searching here
400
401 // Test and set the visited bit.
402 if (mid->raise_LCA_visited() == mark) continue; // already visited
403
404 // Don't process the current LCA, otherwise the search may terminate early
405 if (mid != LCA && mid->raise_LCA_mark() == mark) {
406 // Raise the LCA.
407 LCA = mid->dom_lca(LCA);
408 if (LCA == early) break; // stop searching everywhere
409 assert(early->dominates(LCA), "early is high enough");
410 // Resume searching at that point, skipping intermediate levels.
411 worklist.push(LCA);
412 if (LCA == mid)
413 continue; // Don't mark as visited to avoid early termination.
414 } else {
415 // Keep searching through this block's predecessors.
416 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
417 Block* mid_parent = cfg->get_block_for_node(mid->pred(j));
418 worklist.push(mid_parent);
419 }
420 }
421 mid->set_raise_LCA_visited(mark);
422 }
423 return LCA;
424 }
425
426 //--------------------------memory_early_block--------------------------------
427 // This is a variation of find_deepest_input, the heart of schedule_early.
428 // Find the "early" block for a load, if we considered only memory and
429 // address inputs, that is, if other data inputs were ignored.
430 //
431 // Because a subset of edges are considered, the resulting block will
432 // be earlier (at a shallower dom_depth) than the true schedule_early
433 // point of the node. We compute this earlier block as a more permissive
434 // site for anti-dependency insertion, but only if subsume_loads is enabled.
435 static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) {
436 Node* base;
437 Node* index;
438 Node* store = load->in(MemNode::Memory);
439 load->as_Mach()->memory_inputs(base, index);
440
441 assert(base != NodeSentinel && index != NodeSentinel,
442 "unexpected base/index inputs");
443
444 Node* mem_inputs[4];
445 int mem_inputs_length = 0;
446 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
447 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
448 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
449
450 // In the comparision below, add one to account for the control input,
451 // which may be null, but always takes up a spot in the in array.
452 if (mem_inputs_length + 1 < (int) load->req()) {
453 // This "load" has more inputs than just the memory, base and index inputs.
454 // For purposes of checking anti-dependences, we need to start
455 // from the early block of only the address portion of the instruction,
456 // and ignore other blocks that may have factored into the wider
457 // schedule_early calculation.
458 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
459
460 Block* deepb = NULL; // Deepest block so far
461 int deepb_dom_depth = 0;
462 for (int i = 0; i < mem_inputs_length; i++) {
463 Block* inb = cfg->get_block_for_node(mem_inputs[i]);
464 if (deepb_dom_depth < (int) inb->_dom_depth) {
465 // The new inb must be dominated by the previous deepb.
466 // The various inputs must be linearly ordered in the dom
467 // tree, or else there will not be a unique deepest block.
468 DEBUG_ONLY(assert_dom(deepb, inb, load, cfg));
469 deepb = inb; // Save deepest block
470 deepb_dom_depth = deepb->_dom_depth;
471 }
472 }
473 early = deepb;
474 }
475
476 return early;
477 }
478
479 //--------------------------insert_anti_dependences---------------------------
480 // A load may need to witness memory that nearby stores can overwrite.
481 // For each nearby store, either insert an "anti-dependence" edge
482 // from the load to the store, or else move LCA upward to force the
483 // load to (eventually) be scheduled in a block above the store.
484 //
485 // Do not add edges to stores on distinct control-flow paths;
486 // only add edges to stores which might interfere.
487 //
488 // Return the (updated) LCA. There will not be any possibly interfering
489 // store between the load's "early block" and the updated LCA.
490 // Any stores in the updated LCA will have new precedence edges
491 // back to the load. The caller is expected to schedule the load
492 // in the LCA, in which case the precedence edges will make LCM
493 // preserve anti-dependences. The caller may also hoist the load
494 // above the LCA, if it is not the early block.
495 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
496 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
497 assert(LCA != NULL, "");
498 DEBUG_ONLY(Block* LCA_orig = LCA);
499
500 // Compute the alias index. Loads and stores with different alias indices
501 // do not need anti-dependence edges.
502 uint load_alias_idx = C->get_alias_index(load->adr_type());
503 #ifdef ASSERT
504 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
505 (PrintOpto || VerifyAliases ||
506 PrintMiscellaneous && (WizardMode || Verbose))) {
507 // Load nodes should not consume all of memory.
508 // Reporting a bottom type indicates a bug in adlc.
509 // If some particular type of node validly consumes all of memory,
510 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
511 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
512 load->dump(2);
513 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
514 }
515 #endif
516 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
517 "String compare is only known 'load' that does not conflict with any stores");
518 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals),
519 "String equals is a 'load' that does not conflict with any stores");
520 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf),
521 "String indexOf is a 'load' that does not conflict with any stores");
522 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq),
523 "Arrays equals is a 'load' that do not conflict with any stores");
524
525 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
526 // It is impossible to spoil this load by putting stores before it,
527 // because we know that the stores will never update the value
528 // which 'load' must witness.
529 return LCA;
530 }
531
532 node_idx_t load_index = load->_idx;
533
534 // Note the earliest legal placement of 'load', as determined by
535 // by the unique point in the dom tree where all memory effects
536 // and other inputs are first available. (Computed by schedule_early.)
537 // For normal loads, 'early' is the shallowest place (dom graph wise)
538 // to look for anti-deps between this load and any store.
539 Block* early = get_block_for_node(load);
540
541 // If we are subsuming loads, compute an "early" block that only considers
542 // memory or address inputs. This block may be different than the
543 // schedule_early block in that it could be at an even shallower depth in the
544 // dominator tree, and allow for a broader discovery of anti-dependences.
545 if (C->subsume_loads()) {
546 early = memory_early_block(load, early, this);
547 }
548
549 ResourceArea *area = Thread::current()->resource_area();
550 Node_List worklist_mem(area); // prior memory state to store
551 Node_List worklist_store(area); // possible-def to explore
552 Node_List worklist_visited(area); // visited mergemem nodes
553 Node_List non_early_stores(area); // all relevant stores outside of early
554 bool must_raise_LCA = false;
555
556 #ifdef TRACK_PHI_INPUTS
557 // %%% This extra checking fails because MergeMem nodes are not GVNed.
558 // Provide "phi_inputs" to check if every input to a PhiNode is from the
559 // original memory state. This indicates a PhiNode for which should not
560 // prevent the load from sinking. For such a block, set_raise_LCA_mark
561 // may be overly conservative.
562 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
563 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
564 #endif
565
566 // 'load' uses some memory state; look for users of the same state.
567 // Recurse through MergeMem nodes to the stores that use them.
568
569 // Each of these stores is a possible definition of memory
570 // that 'load' needs to use. We need to force 'load'
571 // to occur before each such store. When the store is in
572 // the same block as 'load', we insert an anti-dependence
573 // edge load->store.
574
575 // The relevant stores "nearby" the load consist of a tree rooted
576 // at initial_mem, with internal nodes of type MergeMem.
577 // Therefore, the branches visited by the worklist are of this form:
578 // initial_mem -> (MergeMem ->)* store
579 // The anti-dependence constraints apply only to the fringe of this tree.
580
581 Node* initial_mem = load->in(MemNode::Memory);
582 worklist_store.push(initial_mem);
583 worklist_visited.push(initial_mem);
584 worklist_mem.push(NULL);
585 while (worklist_store.size() > 0) {
586 // Examine a nearby store to see if it might interfere with our load.
587 Node* mem = worklist_mem.pop();
588 Node* store = worklist_store.pop();
589 uint op = store->Opcode();
590
591 // MergeMems do not directly have anti-deps.
592 // Treat them as internal nodes in a forward tree of memory states,
593 // the leaves of which are each a 'possible-def'.
594 if (store == initial_mem // root (exclusive) of tree we are searching
595 || op == Op_MergeMem // internal node of tree we are searching
596 ) {
597 mem = store; // It's not a possibly interfering store.
598 if (store == initial_mem)
599 initial_mem = NULL; // only process initial memory once
600
601 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
602 store = mem->fast_out(i);
603 if (store->is_MergeMem()) {
604 // Be sure we don't get into combinatorial problems.
605 // (Allow phis to be repeated; they can merge two relevant states.)
606 uint j = worklist_visited.size();
607 for (; j > 0; j--) {
608 if (worklist_visited.at(j-1) == store) break;
609 }
610 if (j > 0) continue; // already on work list; do not repeat
611 worklist_visited.push(store);
612 }
613 worklist_mem.push(mem);
614 worklist_store.push(store);
615 }
616 continue;
617 }
618
619 if (op == Op_MachProj || op == Op_Catch) continue;
620 if (store->needs_anti_dependence_check()) continue; // not really a store
621
622 // Compute the alias index. Loads and stores with different alias
623 // indices do not need anti-dependence edges. Wide MemBar's are
624 // anti-dependent on everything (except immutable memories).
625 const TypePtr* adr_type = store->adr_type();
626 if (!C->can_alias(adr_type, load_alias_idx)) continue;
627
628 // Most slow-path runtime calls do NOT modify Java memory, but
629 // they can block and so write Raw memory.
630 if (store->is_Mach()) {
631 MachNode* mstore = store->as_Mach();
632 if (load_alias_idx != Compile::AliasIdxRaw) {
633 // Check for call into the runtime using the Java calling
634 // convention (and from there into a wrapper); it has no
635 // _method. Can't do this optimization for Native calls because
636 // they CAN write to Java memory.
637 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
638 assert(mstore->is_MachSafePoint(), "");
639 MachSafePointNode* ms = (MachSafePointNode*) mstore;
640 assert(ms->is_MachCallJava(), "");
641 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
642 if (mcj->_method == NULL) {
643 // These runtime calls do not write to Java visible memory
644 // (other than Raw) and so do not require anti-dependence edges.
645 continue;
646 }
647 }
648 // Same for SafePoints: they read/write Raw but only read otherwise.
649 // This is basically a workaround for SafePoints only defining control
650 // instead of control + memory.
651 if (mstore->ideal_Opcode() == Op_SafePoint)
652 continue;
653 } else {
654 // Some raw memory, such as the load of "top" at an allocation,
655 // can be control dependent on the previous safepoint. See
656 // comments in GraphKit::allocate_heap() about control input.
657 // Inserting an anti-dep between such a safepoint and a use
658 // creates a cycle, and will cause a subsequent failure in
659 // local scheduling. (BugId 4919904)
660 // (%%% How can a control input be a safepoint and not a projection??)
661 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
662 continue;
663 }
664 }
665
666 // Identify a block that the current load must be above,
667 // or else observe that 'store' is all the way up in the
668 // earliest legal block for 'load'. In the latter case,
669 // immediately insert an anti-dependence edge.
670 Block* store_block = get_block_for_node(store);
671 assert(store_block != NULL, "unused killing projections skipped above");
672
673 if (store->is_Phi()) {
674 // 'load' uses memory which is one (or more) of the Phi's inputs.
675 // It must be scheduled not before the Phi, but rather before
676 // each of the relevant Phi inputs.
677 //
678 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
679 // we mark each corresponding predecessor block and do a combined
680 // hoisting operation later (raise_LCA_above_marks).
681 //
682 // Do not assert(store_block != early, "Phi merging memory after access")
683 // PhiNode may be at start of block 'early' with backedge to 'early'
684 DEBUG_ONLY(bool found_match = false);
685 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
686 if (store->in(j) == mem) { // Found matching input?
687 DEBUG_ONLY(found_match = true);
688 Block* pred_block = get_block_for_node(store_block->pred(j));
689 if (pred_block != early) {
690 // If any predecessor of the Phi matches the load's "early block",
691 // we do not need a precedence edge between the Phi and 'load'
692 // since the load will be forced into a block preceding the Phi.
693 pred_block->set_raise_LCA_mark(load_index);
694 assert(!LCA_orig->dominates(pred_block) ||
695 early->dominates(pred_block), "early is high enough");
696 must_raise_LCA = true;
697 } else {
698 // anti-dependent upon PHI pinned below 'early', no edge needed
699 LCA = early; // but can not schedule below 'early'
700 }
701 }
702 }
703 assert(found_match, "no worklist bug");
704 #ifdef TRACK_PHI_INPUTS
705 #ifdef ASSERT
706 // This assert asks about correct handling of PhiNodes, which may not
707 // have all input edges directly from 'mem'. See BugId 4621264
708 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
709 // Increment by exactly one even if there are multiple copies of 'mem'
710 // coming into the phi, because we will run this block several times
711 // if there are several copies of 'mem'. (That's how DU iterators work.)
712 phi_inputs.at_put(store->_idx, num_mem_inputs);
713 assert(PhiNode::Input + num_mem_inputs < store->req(),
714 "Expect at least one phi input will not be from original memory state");
715 #endif //ASSERT
716 #endif //TRACK_PHI_INPUTS
717 } else if (store_block != early) {
718 // 'store' is between the current LCA and earliest possible block.
719 // Label its block, and decide later on how to raise the LCA
720 // to include the effect on LCA of this store.
721 // If this store's block gets chosen as the raised LCA, we
722 // will find him on the non_early_stores list and stick him
723 // with a precedence edge.
724 // (But, don't bother if LCA is already raised all the way.)
725 if (LCA != early) {
726 store_block->set_raise_LCA_mark(load_index);
727 must_raise_LCA = true;
728 non_early_stores.push(store);
729 }
730 } else {
731 // Found a possibly-interfering store in the load's 'early' block.
732 // This means 'load' cannot sink at all in the dominator tree.
733 // Add an anti-dep edge, and squeeze 'load' into the highest block.
734 assert(store != load->in(0), "dependence cycle found");
735 if (verify) {
736 assert(store->find_edge(load) != -1, "missing precedence edge");
737 } else {
738 store->add_prec(load);
739 }
740 LCA = early;
741 // This turns off the process of gathering non_early_stores.
742 }
743 }
744 // (Worklist is now empty; all nearby stores have been visited.)
745
746 // Finished if 'load' must be scheduled in its 'early' block.
747 // If we found any stores there, they have already been given
748 // precedence edges.
749 if (LCA == early) return LCA;
750
751 // We get here only if there are no possibly-interfering stores
752 // in the load's 'early' block. Move LCA up above all predecessors
753 // which contain stores we have noted.
754 //
755 // The raised LCA block can be a home to such interfering stores,
756 // but its predecessors must not contain any such stores.
757 //
758 // The raised LCA will be a lower bound for placing the load,
759 // preventing the load from sinking past any block containing
760 // a store that may invalidate the memory state required by 'load'.
761 if (must_raise_LCA)
762 LCA = raise_LCA_above_marks(LCA, load->_idx, early, this);
763 if (LCA == early) return LCA;
764
765 // Insert anti-dependence edges from 'load' to each store
766 // in the non-early LCA block.
767 // Mine the non_early_stores list for such stores.
768 if (LCA->raise_LCA_mark() == load_index) {
769 while (non_early_stores.size() > 0) {
770 Node* store = non_early_stores.pop();
771 Block* store_block = get_block_for_node(store);
772 if (store_block == LCA) {
773 // add anti_dependence from store to load in its own block
774 assert(store != load->in(0), "dependence cycle found");
775 if (verify) {
776 assert(store->find_edge(load) != -1, "missing precedence edge");
777 } else {
778 store->add_prec(load);
779 }
780 } else {
781 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
782 // Any other stores we found must be either inside the new LCA
783 // or else outside the original LCA. In the latter case, they
784 // did not interfere with any use of 'load'.
785 assert(LCA->dominates(store_block)
786 || !LCA_orig->dominates(store_block), "no stray stores");
787 }
788 }
789 }
790
791 // Return the highest block containing stores; any stores
792 // within that block have been given anti-dependence edges.
793 return LCA;
794 }
795
796 // This class is used to iterate backwards over the nodes in the graph.
797
798 class Node_Backward_Iterator {
799
800 private:
801 Node_Backward_Iterator();
802
803 public:
804 // Constructor for the iterator
805 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg);
806
807 // Postincrement operator to iterate over the nodes
808 Node *next();
809
810 private:
811 VectorSet &_visited;
812 Node_List &_stack;
813 PhaseCFG &_cfg;
814 };
815
816 // Constructor for the Node_Backward_Iterator
817 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg)
818 : _visited(visited), _stack(stack), _cfg(cfg) {
819 // The stack should contain exactly the root
820 stack.clear();
821 stack.push(root);
822
823 // Clear the visited bits
824 visited.Clear();
825 }
826
827 // Iterator for the Node_Backward_Iterator
828 Node *Node_Backward_Iterator::next() {
829
830 // If the _stack is empty, then just return NULL: finished.
831 if ( !_stack.size() )
832 return NULL;
833
834 // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been
835 // made stateless, so I do not need to record the index 'i' on my _stack.
836 // Instead I visit all users each time, scanning for unvisited users.
837 // I visit unvisited not-anti-dependence users first, then anti-dependent
838 // children next.
839 Node *self = _stack.pop();
840
841 // I cycle here when I am entering a deeper level of recursion.
842 // The key variable 'self' was set prior to jumping here.
843 while( 1 ) {
844
845 _visited.set(self->_idx);
846
847 // Now schedule all uses as late as possible.
848 const Node* src = self->is_Proj() ? self->in(0) : self;
849 uint src_rpo = _cfg.get_block_for_node(src)->_rpo;
850
851 // Schedule all nodes in a post-order visit
852 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
853
854 // Scan for unvisited nodes
855 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
856 // For all uses, schedule late
857 Node* n = self->fast_out(i); // Use
858
859 // Skip already visited children
860 if ( _visited.test(n->_idx) )
861 continue;
862
863 // do not traverse backward control edges
864 Node *use = n->is_Proj() ? n->in(0) : n;
865 uint use_rpo = _cfg.get_block_for_node(use)->_rpo;
866
867 if ( use_rpo < src_rpo )
868 continue;
869
870 // Phi nodes always precede uses in a basic block
871 if ( use_rpo == src_rpo && use->is_Phi() )
872 continue;
873
874 unvisited = n; // Found unvisited
875
876 // Check for possible-anti-dependent
877 if( !n->needs_anti_dependence_check() )
878 break; // Not visited, not anti-dep; schedule it NOW
879 }
880
881 // Did I find an unvisited not-anti-dependent Node?
882 if ( !unvisited )
883 break; // All done with children; post-visit 'self'
884
885 // Visit the unvisited Node. Contains the obvious push to
886 // indicate I'm entering a deeper level of recursion. I push the
887 // old state onto the _stack and set a new state and loop (recurse).
888 _stack.push(self);
889 self = unvisited;
890 } // End recursion loop
891
892 return self;
893 }
894
895 //------------------------------ComputeLatenciesBackwards----------------------
896 // Compute the latency of all the instructions.
897 void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_List &stack) {
898 #ifndef PRODUCT
899 if (trace_opto_pipelining())
900 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
901 #endif
902
903 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
904 Node *n;
905
906 // Walk over all the nodes from last to first
907 while (n = iter.next()) {
908 // Set the latency for the definitions of this instruction
909 partial_latency_of_defs(n);
910 }
911 } // end ComputeLatenciesBackwards
912
913 //------------------------------partial_latency_of_defs------------------------
914 // Compute the latency impact of this node on all defs. This computes
915 // a number that increases as we approach the beginning of the routine.
916 void PhaseCFG::partial_latency_of_defs(Node *n) {
917 // Set the latency for this instruction
918 #ifndef PRODUCT
919 if (trace_opto_pipelining()) {
920 tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
921 dump();
922 }
923 #endif
924
925 if (n->is_Proj()) {
926 n = n->in(0);
927 }
928
929 if (n->is_Root()) {
930 return;
931 }
932
933 uint nlen = n->len();
934 uint use_latency = get_latency_for_node(n);
935 uint use_pre_order = get_block_for_node(n)->_pre_order;
936
937 for (uint j = 0; j < nlen; j++) {
938 Node *def = n->in(j);
939
940 if (!def || def == n) {
941 continue;
942 }
943
944 // Walk backwards thru projections
945 if (def->is_Proj()) {
946 def = def->in(0);
947 }
948
949 #ifndef PRODUCT
950 if (trace_opto_pipelining()) {
951 tty->print("# in(%2d): ", j);
952 def->dump();
953 }
954 #endif
955
956 // If the defining block is not known, assume it is ok
957 Block *def_block = get_block_for_node(def);
958 uint def_pre_order = def_block ? def_block->_pre_order : 0;
959
960 if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) {
961 continue;
962 }
963
964 uint delta_latency = n->latency(j);
965 uint current_latency = delta_latency + use_latency;
966
967 if (get_latency_for_node(def) < current_latency) {
968 set_latency_for_node(def, current_latency);
969 }
970
971 #ifndef PRODUCT
972 if (trace_opto_pipelining()) {
973 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));
974 }
975 #endif
976 }
977 }
978
979 //------------------------------latency_from_use-------------------------------
980 // Compute the latency of a specific use
981 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
982 // If self-reference, return no latency
983 if (use == n || use->is_Root()) {
984 return 0;
985 }
986
987 uint def_pre_order = get_block_for_node(def)->_pre_order;
988 uint latency = 0;
989
990 // If the use is not a projection, then it is simple...
991 if (!use->is_Proj()) {
992 #ifndef PRODUCT
993 if (trace_opto_pipelining()) {
994 tty->print("# out(): ");
995 use->dump();
996 }
997 #endif
998
999 uint use_pre_order = get_block_for_node(use)->_pre_order;
1000
1001 if (use_pre_order < def_pre_order)
1002 return 0;
1003
1004 if (use_pre_order == def_pre_order && use->is_Phi())
1005 return 0;
1006
1007 uint nlen = use->len();
1008 uint nl = get_latency_for_node(use);
1009
1010 for ( uint j=0; j<nlen; j++ ) {
1011 if (use->in(j) == n) {
1012 // Change this if we want local latencies
1013 uint ul = use->latency(j);
1014 uint l = ul + nl;
1015 if (latency < l) latency = l;
1016 #ifndef PRODUCT
1017 if (trace_opto_pipelining()) {
1018 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
1019 nl, j, ul, l, latency);
1020 }
1021 #endif
1022 }
1023 }
1024 } else {
1025 // This is a projection, just grab the latency of the use(s)
1026 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
1027 uint l = latency_from_use(use, def, use->fast_out(j));
1028 if (latency < l) latency = l;
1029 }
1030 }
1031
1032 return latency;
1033 }
1034
1035 //------------------------------latency_from_uses------------------------------
1036 // Compute the latency of this instruction relative to all of it's uses.
1037 // This computes a number that increases as we approach the beginning of the
1038 // routine.
1039 void PhaseCFG::latency_from_uses(Node *n) {
1040 // Set the latency for this instruction
1041 #ifndef PRODUCT
1042 if (trace_opto_pipelining()) {
1043 tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n));
1044 dump();
1045 }
1046 #endif
1047 uint latency=0;
1048 const Node *def = n->is_Proj() ? n->in(0): n;
1049
1050 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1051 uint l = latency_from_use(n, def, n->fast_out(i));
1052
1053 if (latency < l) latency = l;
1054 }
1055
1056 set_latency_for_node(n, latency);
1057 }
1058
1059 //------------------------------hoist_to_cheaper_block-------------------------
1060 // Pick a block for node self, between early and LCA, that is a cheaper
1061 // alternative to LCA.
1062 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1063 const double delta = 1+PROB_UNLIKELY_MAG(4);
1064 Block* least = LCA;
1065 double least_freq = least->_freq;
1066 uint target = get_latency_for_node(self);
1067 uint start_latency = get_latency_for_node(LCA->head());
1068 uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx()));
1069 bool in_latency = (target <= start_latency);
1070 const Block* root_block = get_block_for_node(_root);
1071
1072 // Turn off latency scheduling if scheduling is just plain off
1073 if (!C->do_scheduling())
1074 in_latency = true;
1075
1076 // Do not hoist (to cover latency) instructions which target a
1077 // single register. Hoisting stretches the live range of the
1078 // single register and may force spilling.
1079 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1080 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
1081 in_latency = true;
1082
1083 #ifndef PRODUCT
1084 if (trace_opto_pipelining()) {
1085 tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self));
1086 self->dump();
1087 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1088 LCA->_pre_order,
1089 LCA->head()->_idx,
1090 start_latency,
1091 LCA->get_node(LCA->end_idx())->_idx,
1092 end_latency,
1093 least_freq);
1094 }
1095 #endif
1096
1097 int cand_cnt = 0; // number of candidates tried
1098
1099 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1100 // the earliest legal location. Capture the least execution frequency.
1101 while (LCA != early) {
1102 LCA = LCA->_idom; // Follow up the dominator tree
1103
1104 if (LCA == NULL) {
1105 // Bailout without retry
1106 assert(false, "graph should be schedulable");
1107 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1108 return least;
1109 }
1110
1111 // Don't hoist machine instructions to the root basic block
1112 if (mach && LCA == root_block)
1113 break;
1114
1115 uint start_lat = get_latency_for_node(LCA->head());
1116 uint end_idx = LCA->end_idx();
1117 uint end_lat = get_latency_for_node(LCA->get_node(end_idx));
1118 double LCA_freq = LCA->_freq;
1119 #ifndef PRODUCT
1120 if (trace_opto_pipelining()) {
1121 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1122 LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq);
1123 }
1124 #endif
1125 cand_cnt++;
1126 if (LCA_freq < least_freq || // Better Frequency
1127 (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
1128 (!StressGCM && // Otherwise, choose with latency
1129 !in_latency && // No block containing latency
1130 LCA_freq < least_freq * delta && // No worse frequency
1131 target >= end_lat && // within latency range
1132 !self->is_iteratively_computed() ) // But don't hoist IV increments
1133 // because they may end up above other uses of their phi forcing
1134 // their result register to be different from their input.
1135 ) {
1136 least = LCA; // Found cheaper block
1137 least_freq = LCA_freq;
1138 start_latency = start_lat;
1139 end_latency = end_lat;
1140 if (target <= start_lat)
1141 in_latency = true;
1142 }
1143 }
1144
1145 #ifndef PRODUCT
1146 if (trace_opto_pipelining()) {
1147 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1148 least->_pre_order, start_latency, least_freq);
1149 }
1150 #endif
1151
1152 // See if the latency needs to be updated
1153 if (target < end_latency) {
1154 #ifndef PRODUCT
1155 if (trace_opto_pipelining()) {
1156 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1157 }
1158 #endif
1159 set_latency_for_node(self, end_latency);
1160 partial_latency_of_defs(self);
1161 }
1162
1163 return least;
1164 }
1165
1166
1167 //------------------------------schedule_late-----------------------------------
1168 // Now schedule all codes as LATE as possible. This is the LCA in the
1169 // dominator tree of all USES of a value. Pick the block with the least
1170 // loop nesting depth that is lowest in the dominator tree.
1171 extern const char must_clone[];
1172 void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) {
1173 #ifndef PRODUCT
1174 if (trace_opto_pipelining())
1175 tty->print("\n#---- schedule_late ----\n");
1176 #endif
1177
1178 Node_Backward_Iterator iter((Node *)_root, visited, stack, *this);
1179 Node *self;
1180
1181 // Walk over all the nodes from last to first
1182 while (self = iter.next()) {
1183 Block* early = get_block_for_node(self); // Earliest legal placement
1184
1185 if (self->is_top()) {
1186 // Top node goes in bb #2 with other constants.
1187 // It must be special-cased, because it has no out edges.
1188 early->add_inst(self);
1189 continue;
1190 }
1191
1192 // No uses, just terminate
1193 if (self->outcnt() == 0) {
1194 assert(self->is_MachProj(), "sanity");
1195 continue; // Must be a dead machine projection
1196 }
1197
1198 // If node is pinned in the block, then no scheduling can be done.
1199 if( self->pinned() ) // Pinned in block?
1200 continue;
1201
1202 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1203 if (mach) {
1204 switch (mach->ideal_Opcode()) {
1205 case Op_CreateEx:
1206 // Don't move exception creation
1207 early->add_inst(self);
1208 continue;
1209 break;
1210 case Op_CheckCastPP:
1211 // Don't move CheckCastPP nodes away from their input, if the input
1212 // is a rawptr (5071820).
1213 Node *def = self->in(1);
1214 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1215 early->add_inst(self);
1216 #ifdef ASSERT
1217 _raw_oops.push(def);
1218 #endif
1219 continue;
1220 }
1221 break;
1222 }
1223 }
1224
1225 // Gather LCA of all uses
1226 Block *LCA = NULL;
1227 {
1228 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1229 // For all uses, find LCA
1230 Node* use = self->fast_out(i);
1231 LCA = raise_LCA_above_use(LCA, use, self, this);
1232 }
1233 } // (Hide defs of imax, i from rest of block.)
1234
1235 // Place temps in the block of their use. This isn't a
1236 // requirement for correctness but it reduces useless
1237 // interference between temps and other nodes.
1238 if (mach != NULL && mach->is_MachTemp()) {
1239 map_node_to_block(self, LCA);
1240 LCA->add_inst(self);
1241 continue;
1242 }
1243
1244 // Check if 'self' could be anti-dependent on memory
1245 if (self->needs_anti_dependence_check()) {
1246 // Hoist LCA above possible-defs and insert anti-dependences to
1247 // defs in new LCA block.
1248 LCA = insert_anti_dependences(LCA, self);
1249 }
1250
1251 if (early->_dom_depth > LCA->_dom_depth) {
1252 // Somehow the LCA has moved above the earliest legal point.
1253 // (One way this can happen is via memory_early_block.)
1254 if (C->subsume_loads() == true && !C->failing()) {
1255 // Retry with subsume_loads == false
1256 // If this is the first failure, the sentinel string will "stick"
1257 // to the Compile object, and the C2Compiler will see it and retry.
1258 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1259 } else {
1260 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1261 assert(false, "graph should be schedulable");
1262 C->record_method_not_compilable("late schedule failed: incorrect graph");
1263 }
1264 return;
1265 }
1266
1267 // If there is no opportunity to hoist, then we're done.
1268 // In stress mode, try to hoist even the single operations.
1269 bool try_to_hoist = StressGCM || (LCA != early);
1270
1271 // Must clone guys stay next to use; no hoisting allowed.
1272 // Also cannot hoist guys that alter memory or are otherwise not
1273 // allocatable (hoisting can make a value live longer, leading to
1274 // anti and output dependency problems which are normally resolved
1275 // by the register allocator giving everyone a different register).
1276 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1277 try_to_hoist = false;
1278
1279 Block* late = NULL;
1280 if (try_to_hoist) {
1281 // Now find the block with the least execution frequency.
1282 // Start at the latest schedule and work up to the earliest schedule
1283 // in the dominator tree. Thus the Node will dominate all its uses.
1284 late = hoist_to_cheaper_block(LCA, early, self);
1285 } else {
1286 // Just use the LCA of the uses.
1287 late = LCA;
1288 }
1289
1290 // Put the node into target block
1291 schedule_node_into_block(self, late);
1292
1293 #ifdef ASSERT
1294 if (self->needs_anti_dependence_check()) {
1295 // since precedence edges are only inserted when we're sure they
1296 // are needed make sure that after placement in a block we don't
1297 // need any new precedence edges.
1298 verify_anti_dependences(late, self);
1299 }
1300 #endif
1301 } // Loop until all nodes have been visited
1302
1303 } // end ScheduleLate
1304
1305 //------------------------------GlobalCodeMotion-------------------------------
1306 void PhaseCFG::global_code_motion() {
1307 ResourceMark rm;
1308
1309 #ifndef PRODUCT
1310 if (trace_opto_pipelining()) {
1311 tty->print("\n---- Start GlobalCodeMotion ----\n");
1312 }
1313 #endif
1314
1315 // Initialize the node to block mapping for things on the proj_list
1316 for (uint i = 0; i < _matcher.number_of_projections(); i++) {
1317 unmap_node_from_block(_matcher.get_projection(i));
1318 }
1319
1320 // Set the basic block for Nodes pinned into blocks
1321 Arena* arena = Thread::current()->resource_area();
1322 VectorSet visited(arena);
1323 schedule_pinned_nodes(visited);
1324
1325 // Find the earliest Block any instruction can be placed in. Some
1326 // instructions are pinned into Blocks. Unpinned instructions can
1327 // appear in last block in which all their inputs occur.
1328 visited.Clear();
1329 Node_List stack(arena);
1330 // Pre-grow the list
1331 stack.map((C->live_nodes() >> 1) + 16, NULL);
1332 if (!schedule_early(visited, stack)) {
1333 // Bailout without retry
1334 C->record_method_not_compilable("early schedule failed");
1335 return;
1336 }
1337
1338 // Build Def-Use edges.
1339 // Compute the latency information (via backwards walk) for all the
1340 // instructions in the graph
1341 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1342
1343 if (C->do_scheduling()) {
1344 compute_latencies_backwards(visited, stack);
1345 }
1346
1347 // Now schedule all codes as LATE as possible. This is the LCA in the
1348 // dominator tree of all USES of a value. Pick the block with the least
1349 // loop nesting depth that is lowest in the dominator tree.
1350 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1351 schedule_late(visited, stack);
1352 if (C->failing()) {
1353 return;
1354 }
1355
1356 #ifndef PRODUCT
1357 if (trace_opto_pipelining()) {
1358 tty->print("\n---- Detect implicit null checks ----\n");
1359 }
1360 #endif
1361
1362 // Detect implicit-null-check opportunities. Basically, find NULL checks
1363 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1364 // I can generate a memory op if there is not one nearby.
1365 if (C->is_method_compilation()) {
1366 // By reversing the loop direction we get a very minor gain on mpegaudio.
1367 // Feel free to revert to a forward loop for clarity.
1368 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1369 for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) {
1370 Node* proj = _matcher._null_check_tests[i];
1371 Node* val = _matcher._null_check_tests[i + 1];
1372 Block* block = get_block_for_node(proj);
1373 implicit_null_check(block, proj, val, C->allowed_deopt_reasons());
1374 // The implicit_null_check will only perform the transformation
1375 // if the null branch is truly uncommon, *and* it leads to an
1376 // uncommon trap. Combined with the too_many_traps guards
1377 // above, this prevents SEGV storms reported in 6366351,
1378 // by recompiling offending methods without this optimization.
1379 }
1380 }
1381
1382 #ifndef PRODUCT
1383 if (trace_opto_pipelining()) {
1384 tty->print("\n---- Start Local Scheduling ----\n");
1385 }
1386 #endif
1387
1388 // Schedule locally. Right now a simple topological sort.
1389 // Later, do a real latency aware scheduler.
1390 GrowableArray<int> ready_cnt(C->unique(), C->unique(), -1);
1391 visited.Clear();
1392 for (uint i = 0; i < number_of_blocks(); i++) {
1393 Block* block = get_block(i);
1394 if (!schedule_local(block, ready_cnt, visited)) {
1395 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1396 C->record_method_not_compilable("local schedule failed");
1397 }
1398 return;
1399 }
1400 }
1401
1402 // If we inserted any instructions between a Call and his CatchNode,
1403 // clone the instructions on all paths below the Catch.
1404 for (uint i = 0; i < number_of_blocks(); i++) {
1405 Block* block = get_block(i);
1406 call_catch_cleanup(block);
1407 }
1408
1409 #ifndef PRODUCT
1410 if (trace_opto_pipelining()) {
1411 tty->print("\n---- After GlobalCodeMotion ----\n");
1412 for (uint i = 0; i < number_of_blocks(); i++) {
1413 Block* block = get_block(i);
1414 block->dump();
1415 }
1416 }
1417 #endif
1418 // Dead.
1419 _node_latency = (GrowableArray<uint> *)((intptr_t)0xdeadbeef);
1420 }
1421
1422 bool PhaseCFG::do_global_code_motion() {
1423
1424 build_dominator_tree();
1425 if (C->failing()) {
1426 return false;
1427 }
1428
1429 NOT_PRODUCT( C->verify_graph_edges(); )
1430
1431 estimate_block_frequency();
1432
1433 global_code_motion();
1434
1435 if (C->failing()) {
1436 return false;
1437 }
1438
1439 return true;
1440 }
1441
1442 //------------------------------Estimate_Block_Frequency-----------------------
1443 // Estimate block frequencies based on IfNode probabilities.
1444 void PhaseCFG::estimate_block_frequency() {
1445
1446 // Force conditional branches leading to uncommon traps to be unlikely,
1447 // not because we get to the uncommon_trap with less relative frequency,
1448 // but because an uncommon_trap typically causes a deopt, so we only get
1449 // there once.
1450 if (C->do_freq_based_layout()) {
1451 Block_List worklist;
1452 Block* root_blk = get_block(0);
1453 for (uint i = 1; i < root_blk->num_preds(); i++) {
1454 Block *pb = get_block_for_node(root_blk->pred(i));
1455 if (pb->has_uncommon_code()) {
1456 worklist.push(pb);
1457 }
1458 }
1459 while (worklist.size() > 0) {
1460 Block* uct = worklist.pop();
1461 if (uct == get_root_block()) {
1462 continue;
1463 }
1464 for (uint i = 1; i < uct->num_preds(); i++) {
1465 Block *pb = get_block_for_node(uct->pred(i));
1466 if (pb->_num_succs == 1) {
1467 worklist.push(pb);
1468 } else if (pb->num_fall_throughs() == 2) {
1469 pb->update_uncommon_branch(uct);
1470 }
1471 }
1472 }
1473 }
1474
1475 // Create the loop tree and calculate loop depth.
1476 _root_loop = create_loop_tree();
1477 _root_loop->compute_loop_depth(0);
1478
1479 // Compute block frequency of each block, relative to a single loop entry.
1480 _root_loop->compute_freq();
1481
1482 // Adjust all frequencies to be relative to a single method entry
1483 _root_loop->_freq = 1.0;
1484 _root_loop->scale_freq();
1485
1486 // Save outmost loop frequency for LRG frequency threshold
1487 _outer_loop_frequency = _root_loop->outer_loop_freq();
1488
1489 // force paths ending at uncommon traps to be infrequent
1490 if (!C->do_freq_based_layout()) {
1491 Block_List worklist;
1492 Block* root_blk = get_block(0);
1493 for (uint i = 1; i < root_blk->num_preds(); i++) {
1494 Block *pb = get_block_for_node(root_blk->pred(i));
1495 if (pb->has_uncommon_code()) {
1496 worklist.push(pb);
1497 }
1498 }
1499 while (worklist.size() > 0) {
1500 Block* uct = worklist.pop();
1501 uct->_freq = PROB_MIN;
1502 for (uint i = 1; i < uct->num_preds(); i++) {
1503 Block *pb = get_block_for_node(uct->pred(i));
1504 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1505 worklist.push(pb);
1506 }
1507 }
1508 }
1509 }
1510
1511 #ifdef ASSERT
1512 for (uint i = 0; i < number_of_blocks(); i++) {
1513 Block* b = get_block(i);
1514 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
1515 }
1516 #endif
1517
1518 #ifndef PRODUCT
1519 if (PrintCFGBlockFreq) {
1520 tty->print_cr("CFG Block Frequencies");
1521 _root_loop->dump_tree();
1522 if (Verbose) {
1523 tty->print_cr("PhaseCFG dump");
1524 dump();
1525 tty->print_cr("Node dump");
1526 _root->dump(99999);
1527 }
1528 }
1529 #endif
1530 }
1531
1532 //----------------------------create_loop_tree--------------------------------
1533 // Create a loop tree from the CFG
1534 CFGLoop* PhaseCFG::create_loop_tree() {
1535
1536 #ifdef ASSERT
1537 assert(get_block(0) == get_root_block(), "first block should be root block");
1538 for (uint i = 0; i < number_of_blocks(); i++) {
1539 Block* block = get_block(i);
1540 // Check that _loop field are clear...we could clear them if not.
1541 assert(block->_loop == NULL, "clear _loop expected");
1542 // Sanity check that the RPO numbering is reflected in the _blocks array.
1543 // It doesn't have to be for the loop tree to be built, but if it is not,
1544 // then the blocks have been reordered since dom graph building...which
1545 // may question the RPO numbering
1546 assert(block->_rpo == i, "unexpected reverse post order number");
1547 }
1548 #endif
1549
1550 int idct = 0;
1551 CFGLoop* root_loop = new CFGLoop(idct++);
1552
1553 Block_List worklist;
1554
1555 // Assign blocks to loops
1556 for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block
1557 Block* block = get_block(i);
1558
1559 if (block->head()->is_Loop()) {
1560 Block* loop_head = block;
1561 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1562 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1563 Block* tail = get_block_for_node(tail_n);
1564
1565 // Defensively filter out Loop nodes for non-single-entry loops.
1566 // For all reasonable loops, the head occurs before the tail in RPO.
1567 if (i <= tail->_rpo) {
1568
1569 // The tail and (recursive) predecessors of the tail
1570 // are made members of a new loop.
1571
1572 assert(worklist.size() == 0, "nonempty worklist");
1573 CFGLoop* nloop = new CFGLoop(idct++);
1574 assert(loop_head->_loop == NULL, "just checking");
1575 loop_head->_loop = nloop;
1576 // Add to nloop so push_pred() will skip over inner loops
1577 nloop->add_member(loop_head);
1578 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this);
1579
1580 while (worklist.size() > 0) {
1581 Block* member = worklist.pop();
1582 if (member != loop_head) {
1583 for (uint j = 1; j < member->num_preds(); j++) {
1584 nloop->push_pred(member, j, worklist, this);
1585 }
1586 }
1587 }
1588 }
1589 }
1590 }
1591
1592 // Create a member list for each loop consisting
1593 // of both blocks and (immediate child) loops.
1594 for (uint i = 0; i < number_of_blocks(); i++) {
1595 Block* block = get_block(i);
1596 CFGLoop* lp = block->_loop;
1597 if (lp == NULL) {
1598 // Not assigned to a loop. Add it to the method's pseudo loop.
1599 block->_loop = root_loop;
1600 lp = root_loop;
1601 }
1602 if (lp == root_loop || block != lp->head()) { // loop heads are already members
1603 lp->add_member(block);
1604 }
1605 if (lp != root_loop) {
1606 if (lp->parent() == NULL) {
1607 // Not a nested loop. Make it a child of the method's pseudo loop.
1608 root_loop->add_nested_loop(lp);
1609 }
1610 if (block == lp->head()) {
1611 // Add nested loop to member list of parent loop.
1612 lp->parent()->add_member(lp);
1613 }
1614 }
1615 }
1616
1617 return root_loop;
1618 }
1619
1620 //------------------------------push_pred--------------------------------------
1621 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) {
1622 Node* pred_n = blk->pred(i);
1623 Block* pred = cfg->get_block_for_node(pred_n);
1624 CFGLoop *pred_loop = pred->_loop;
1625 if (pred_loop == NULL) {
1626 // Filter out blocks for non-single-entry loops.
1627 // For all reasonable loops, the head occurs before the tail in RPO.
1628 if (pred->_rpo > head()->_rpo) {
1629 pred->_loop = this;
1630 worklist.push(pred);
1631 }
1632 } else if (pred_loop != this) {
1633 // Nested loop.
1634 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1635 pred_loop = pred_loop->_parent;
1636 }
1637 // Make pred's loop be a child
1638 if (pred_loop->_parent == NULL) {
1639 add_nested_loop(pred_loop);
1640 // Continue with loop entry predecessor.
1641 Block* pred_head = pred_loop->head();
1642 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1643 assert(pred_head != head(), "loop head in only one loop");
1644 push_pred(pred_head, LoopNode::EntryControl, worklist, cfg);
1645 } else {
1646 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1647 }
1648 }
1649 }
1650
1651 //------------------------------add_nested_loop--------------------------------
1652 // Make cl a child of the current loop in the loop tree.
1653 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1654 assert(_parent == NULL, "no parent yet");
1655 assert(cl != this, "not my own parent");
1656 cl->_parent = this;
1657 CFGLoop* ch = _child;
1658 if (ch == NULL) {
1659 _child = cl;
1660 } else {
1661 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1662 ch->_sibling = cl;
1663 }
1664 }
1665
1666 //------------------------------compute_loop_depth-----------------------------
1667 // Store the loop depth in each CFGLoop object.
1668 // Recursively walk the children to do the same for them.
1669 void CFGLoop::compute_loop_depth(int depth) {
1670 _depth = depth;
1671 CFGLoop* ch = _child;
1672 while (ch != NULL) {
1673 ch->compute_loop_depth(depth + 1);
1674 ch = ch->_sibling;
1675 }
1676 }
1677
1678 //------------------------------compute_freq-----------------------------------
1679 // Compute the frequency of each block and loop, relative to a single entry
1680 // into the dominating loop head.
1681 void CFGLoop::compute_freq() {
1682 // Bottom up traversal of loop tree (visit inner loops first.)
1683 // Set loop head frequency to 1.0, then transitively
1684 // compute frequency for all successors in the loop,
1685 // as well as for each exit edge. Inner loops are
1686 // treated as single blocks with loop exit targets
1687 // as the successor blocks.
1688
1689 // Nested loops first
1690 CFGLoop* ch = _child;
1691 while (ch != NULL) {
1692 ch->compute_freq();
1693 ch = ch->_sibling;
1694 }
1695 assert (_members.length() > 0, "no empty loops");
1696 Block* hd = head();
1697 hd->_freq = 1.0f;
1698 for (int i = 0; i < _members.length(); i++) {
1699 CFGElement* s = _members.at(i);
1700 float freq = s->_freq;
1701 if (s->is_block()) {
1702 Block* b = s->as_Block();
1703 for (uint j = 0; j < b->_num_succs; j++) {
1704 Block* sb = b->_succs[j];
1705 update_succ_freq(sb, freq * b->succ_prob(j));
1706 }
1707 } else {
1708 CFGLoop* lp = s->as_CFGLoop();
1709 assert(lp->_parent == this, "immediate child");
1710 for (int k = 0; k < lp->_exits.length(); k++) {
1711 Block* eb = lp->_exits.at(k).get_target();
1712 float prob = lp->_exits.at(k).get_prob();
1713 update_succ_freq(eb, freq * prob);
1714 }
1715 }
1716 }
1717
1718 // For all loops other than the outer, "method" loop,
1719 // sum and normalize the exit probability. The "method" loop
1720 // should keep the initial exit probability of 1, so that
1721 // inner blocks do not get erroneously scaled.
1722 if (_depth != 0) {
1723 // Total the exit probabilities for this loop.
1724 float exits_sum = 0.0f;
1725 for (int i = 0; i < _exits.length(); i++) {
1726 exits_sum += _exits.at(i).get_prob();
1727 }
1728
1729 // Normalize the exit probabilities. Until now, the
1730 // probabilities estimate the possibility of exit per
1731 // a single loop iteration; afterward, they estimate
1732 // the probability of exit per loop entry.
1733 for (int i = 0; i < _exits.length(); i++) {
1734 Block* et = _exits.at(i).get_target();
1735 float new_prob = 0.0f;
1736 if (_exits.at(i).get_prob() > 0.0f) {
1737 new_prob = _exits.at(i).get_prob() / exits_sum;
1738 }
1739 BlockProbPair bpp(et, new_prob);
1740 _exits.at_put(i, bpp);
1741 }
1742
1743 // Save the total, but guard against unreasonable probability,
1744 // as the value is used to estimate the loop trip count.
1745 // An infinite trip count would blur relative block
1746 // frequencies.
1747 if (exits_sum > 1.0f) exits_sum = 1.0;
1748 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1749 _exit_prob = exits_sum;
1750 }
1751 }
1752
1753 //------------------------------succ_prob-------------------------------------
1754 // Determine the probability of reaching successor 'i' from the receiver block.
1755 float Block::succ_prob(uint i) {
1756 int eidx = end_idx();
1757 Node *n = get_node(eidx); // Get ending Node
1758
1759 int op = n->Opcode();
1760 if (n->is_Mach()) {
1761 if (n->is_MachNullCheck()) {
1762 // Can only reach here if called after lcm. The original Op_If is gone,
1763 // so we attempt to infer the probability from one or both of the
1764 // successor blocks.
1765 assert(_num_succs == 2, "expecting 2 successors of a null check");
1766 // If either successor has only one predecessor, then the
1767 // probability estimate can be derived using the
1768 // relative frequency of the successor and this block.
1769 if (_succs[i]->num_preds() == 2) {
1770 return _succs[i]->_freq / _freq;
1771 } else if (_succs[1-i]->num_preds() == 2) {
1772 return 1 - (_succs[1-i]->_freq / _freq);
1773 } else {
1774 // Estimate using both successor frequencies
1775 float freq = _succs[i]->_freq;
1776 return freq / (freq + _succs[1-i]->_freq);
1777 }
1778 }
1779 op = n->as_Mach()->ideal_Opcode();
1780 }
1781
1782
1783 // Switch on branch type
1784 switch( op ) {
1785 case Op_CountedLoopEnd:
1786 case Op_If: {
1787 assert (i < 2, "just checking");
1788 // Conditionals pass on only part of their frequency
1789 float prob = n->as_MachIf()->_prob;
1790 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1791 // If succ[i] is the FALSE branch, invert path info
1792 if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) {
1793 return 1.0f - prob; // not taken
1794 } else {
1795 return prob; // taken
1796 }
1797 }
1798
1799 case Op_Jump:
1800 // Divide the frequency between all successors evenly
1801 return 1.0f/_num_succs;
1802
1803 case Op_Catch: {
1804 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1805 if (ci->_con == CatchProjNode::fall_through_index) {
1806 // Fall-thru path gets the lion's share.
1807 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1808 } else {
1809 // Presume exceptional paths are equally unlikely
1810 return PROB_UNLIKELY_MAG(5);
1811 }
1812 }
1813
1814 case Op_Root:
1815 case Op_Goto:
1816 // Pass frequency straight thru to target
1817 return 1.0f;
1818
1819 case Op_NeverBranch:
1820 return 0.0f;
1821
1822 case Op_TailCall:
1823 case Op_TailJump:
1824 case Op_Return:
1825 case Op_Halt:
1826 case Op_Rethrow:
1827 // Do not push out freq to root block
1828 return 0.0f;
1829
1830 default:
1831 ShouldNotReachHere();
1832 }
1833
1834 return 0.0f;
1835 }
1836
1837 //------------------------------num_fall_throughs-----------------------------
1838 // Return the number of fall-through candidates for a block
1839 int Block::num_fall_throughs() {
1840 int eidx = end_idx();
1841 Node *n = get_node(eidx); // Get ending Node
1842
1843 int op = n->Opcode();
1844 if (n->is_Mach()) {
1845 if (n->is_MachNullCheck()) {
1846 // In theory, either side can fall-thru, for simplicity sake,
1847 // let's say only the false branch can now.
1848 return 1;
1849 }
1850 op = n->as_Mach()->ideal_Opcode();
1851 }
1852
1853 // Switch on branch type
1854 switch( op ) {
1855 case Op_CountedLoopEnd:
1856 case Op_If:
1857 return 2;
1858
1859 case Op_Root:
1860 case Op_Goto:
1861 return 1;
1862
1863 case Op_Catch: {
1864 for (uint i = 0; i < _num_succs; i++) {
1865 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1866 if (ci->_con == CatchProjNode::fall_through_index) {
1867 return 1;
1868 }
1869 }
1870 return 0;
1871 }
1872
1873 case Op_Jump:
1874 case Op_NeverBranch:
1875 case Op_TailCall:
1876 case Op_TailJump:
1877 case Op_Return:
1878 case Op_Halt:
1879 case Op_Rethrow:
1880 return 0;
1881
1882 default:
1883 ShouldNotReachHere();
1884 }
1885
1886 return 0;
1887 }
1888
1889 //------------------------------succ_fall_through-----------------------------
1890 // Return true if a specific successor could be fall-through target.
1891 bool Block::succ_fall_through(uint i) {
1892 int eidx = end_idx();
1893 Node *n = get_node(eidx); // Get ending Node
1894
1895 int op = n->Opcode();
1896 if (n->is_Mach()) {
1897 if (n->is_MachNullCheck()) {
1898 // In theory, either side can fall-thru, for simplicity sake,
1899 // let's say only the false branch can now.
1900 return get_node(i + eidx + 1)->Opcode() == Op_IfFalse;
1901 }
1902 op = n->as_Mach()->ideal_Opcode();
1903 }
1904
1905 // Switch on branch type
1906 switch( op ) {
1907 case Op_CountedLoopEnd:
1908 case Op_If:
1909 case Op_Root:
1910 case Op_Goto:
1911 return true;
1912
1913 case Op_Catch: {
1914 const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj();
1915 return ci->_con == CatchProjNode::fall_through_index;
1916 }
1917
1918 case Op_Jump:
1919 case Op_NeverBranch:
1920 case Op_TailCall:
1921 case Op_TailJump:
1922 case Op_Return:
1923 case Op_Halt:
1924 case Op_Rethrow:
1925 return false;
1926
1927 default:
1928 ShouldNotReachHere();
1929 }
1930
1931 return false;
1932 }
1933
1934 //------------------------------update_uncommon_branch------------------------
1935 // Update the probability of a two-branch to be uncommon
1936 void Block::update_uncommon_branch(Block* ub) {
1937 int eidx = end_idx();
1938 Node *n = get_node(eidx); // Get ending Node
1939
1940 int op = n->as_Mach()->ideal_Opcode();
1941
1942 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
1943 assert(num_fall_throughs() == 2, "must be a two way branch block");
1944
1945 // Which successor is ub?
1946 uint s;
1947 for (s = 0; s <_num_succs; s++) {
1948 if (_succs[s] == ub) break;
1949 }
1950 assert(s < 2, "uncommon successor must be found");
1951
1952 // If ub is the true path, make the proability small, else
1953 // ub is the false path, and make the probability large
1954 bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse);
1955
1956 // Get existing probability
1957 float p = n->as_MachIf()->_prob;
1958
1959 if (invert) p = 1.0 - p;
1960 if (p > PROB_MIN) {
1961 p = PROB_MIN;
1962 }
1963 if (invert) p = 1.0 - p;
1964
1965 n->as_MachIf()->_prob = p;
1966 }
1967
1968 //------------------------------update_succ_freq-------------------------------
1969 // Update the appropriate frequency associated with block 'b', a successor of
1970 // a block in this loop.
1971 void CFGLoop::update_succ_freq(Block* b, float freq) {
1972 if (b->_loop == this) {
1973 if (b == head()) {
1974 // back branch within the loop
1975 // Do nothing now, the loop carried frequency will be
1976 // adjust later in scale_freq().
1977 } else {
1978 // simple branch within the loop
1979 b->_freq += freq;
1980 }
1981 } else if (!in_loop_nest(b)) {
1982 // branch is exit from this loop
1983 BlockProbPair bpp(b, freq);
1984 _exits.append(bpp);
1985 } else {
1986 // branch into nested loop
1987 CFGLoop* ch = b->_loop;
1988 ch->_freq += freq;
1989 }
1990 }
1991
1992 //------------------------------in_loop_nest-----------------------------------
1993 // Determine if block b is in the receiver's loop nest.
1994 bool CFGLoop::in_loop_nest(Block* b) {
1995 int depth = _depth;
1996 CFGLoop* b_loop = b->_loop;
1997 int b_depth = b_loop->_depth;
1998 if (depth == b_depth) {
1999 return true;
2000 }
2001 while (b_depth > depth) {
2002 b_loop = b_loop->_parent;
2003 b_depth = b_loop->_depth;
2004 }
2005 return b_loop == this;
2006 }
2007
2008 //------------------------------scale_freq-------------------------------------
2009 // Scale frequency of loops and blocks by trip counts from outer loops
2010 // Do a top down traversal of loop tree (visit outer loops first.)
2011 void CFGLoop::scale_freq() {
2012 float loop_freq = _freq * trip_count();
2013 _freq = loop_freq;
2014 for (int i = 0; i < _members.length(); i++) {
2015 CFGElement* s = _members.at(i);
2016 float block_freq = s->_freq * loop_freq;
2017 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
2018 block_freq = MIN_BLOCK_FREQUENCY;
2019 s->_freq = block_freq;
2020 }
2021 CFGLoop* ch = _child;
2022 while (ch != NULL) {
2023 ch->scale_freq();
2024 ch = ch->_sibling;
2025 }
2026 }
2027
2028 // Frequency of outer loop
2029 float CFGLoop::outer_loop_freq() const {
2030 if (_child != NULL) {
2031 return _child->_freq;
2032 }
2033 return _freq;
2034 }
2035
2036 #ifndef PRODUCT
2037 //------------------------------dump_tree--------------------------------------
2038 void CFGLoop::dump_tree() const {
2039 dump();
2040 if (_child != NULL) _child->dump_tree();
2041 if (_sibling != NULL) _sibling->dump_tree();
2042 }
2043
2044 //------------------------------dump-------------------------------------------
2045 void CFGLoop::dump() const {
2046 for (int i = 0; i < _depth; i++) tty->print(" ");
2047 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
2048 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
2049 for (int i = 0; i < _depth; i++) tty->print(" ");
2050 tty->print(" members:");
2051 int k = 0;
2052 for (int i = 0; i < _members.length(); i++) {
2053 if (k++ >= 6) {
2054 tty->print("\n ");
2055 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2056 k = 0;
2057 }
2058 CFGElement *s = _members.at(i);
2059 if (s->is_block()) {
2060 Block *b = s->as_Block();
2061 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
2062 } else {
2063 CFGLoop* lp = s->as_CFGLoop();
2064 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
2065 }
2066 }
2067 tty->print("\n");
2068 for (int i = 0; i < _depth; i++) tty->print(" ");
2069 tty->print(" exits: ");
2070 k = 0;
2071 for (int i = 0; i < _exits.length(); i++) {
2072 if (k++ >= 7) {
2073 tty->print("\n ");
2074 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2075 k = 0;
2076 }
2077 Block *blk = _exits.at(i).get_target();
2078 float prob = _exits.at(i).get_prob();
2079 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2080 }
2081 tty->print("\n");
2082 }
2083 #endif