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