1 /*
2 * Copyright (c) 1997, 2010, 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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "libadt/vectset.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/block.hpp"
29 #include "opto/c2compiler.hpp"
30 #include "opto/callnode.hpp"
31 #include "opto/cfgnode.hpp"
32 #include "opto/machnode.hpp"
33 #include "opto/opcodes.hpp"
34 #include "opto/phaseX.hpp"
35 #include "opto/rootnode.hpp"
36 #include "opto/runtime.hpp"
37 #include "runtime/deoptimization.hpp"
38 #ifdef TARGET_ARCH_MODEL_x86_32
39 # include "adfiles/ad_x86_32.hpp"
40 #endif
41 #ifdef TARGET_ARCH_MODEL_x86_64
42 # include "adfiles/ad_x86_64.hpp"
43 #endif
44 #ifdef TARGET_ARCH_MODEL_sparc
45 # include "adfiles/ad_sparc.hpp"
46 #endif
47 #ifdef TARGET_ARCH_MODEL_zero
48 # include "adfiles/ad_zero.hpp"
49 #endif
50
51 // Portions of code courtesy of Clifford Click
52
53 // Optimization - Graph Style
54
55 // To avoid float value underflow
56 #define MIN_BLOCK_FREQUENCY 1.e-35f
57
58 //----------------------------schedule_node_into_block-------------------------
59 // Insert node n into block b. Look for projections of n and make sure they
60 // are in b also.
61 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
62 // Set basic block of n, Add n to b,
63 _bbs.map(n->_idx, b);
64 b->add_inst(n);
65
66 // After Matching, nearly any old Node may have projections trailing it.
67 // These are usually machine-dependent flags. In any case, they might
68 // float to another block below this one. Move them up.
69 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
70 Node* use = n->fast_out(i);
71 if (use->is_Proj()) {
72 Block* buse = _bbs[use->_idx];
73 if (buse != b) { // In wrong block?
74 if (buse != NULL)
75 buse->find_remove(use); // Remove from wrong block
76 _bbs.map(use->_idx, b); // Re-insert in this block
77 b->add_inst(use);
78 }
79 }
80 }
81 }
82
83 //----------------------------replace_block_proj_ctrl-------------------------
84 // Nodes that have is_block_proj() nodes as their control need to use
85 // the appropriate Region for their actual block as their control since
86 // the projection will be in a predecessor block.
87 void PhaseCFG::replace_block_proj_ctrl( Node *n ) {
88 const Node *in0 = n->in(0);
89 assert(in0 != NULL, "Only control-dependent");
90 const Node *p = in0->is_block_proj();
91 if (p != NULL && p != n) { // Control from a block projection?
92 assert(!n->pinned() || n->is_SafePointScalarObject(), "only SafePointScalarObject pinned node is expected here");
93 // Find trailing Region
94 Block *pb = _bbs[in0->_idx]; // Block-projection already has basic block
95 uint j = 0;
96 if (pb->_num_succs != 1) { // More then 1 successor?
97 // Search for successor
98 uint max = pb->_nodes.size();
99 assert( max > 1, "" );
100 uint start = max - pb->_num_succs;
101 // Find which output path belongs to projection
102 for (j = start; j < max; j++) {
103 if( pb->_nodes[j] == in0 )
104 break;
105 }
106 assert( j < max, "must find" );
107 // Change control to match head of successor basic block
108 j -= start;
109 }
110 n->set_req(0, pb->_succs[j]->head());
111 }
112 }
113
114
115 //------------------------------schedule_pinned_nodes--------------------------
116 // Set the basic block for Nodes pinned into blocks
117 void PhaseCFG::schedule_pinned_nodes( VectorSet &visited ) {
118 // Allocate node stack of size C->unique()+8 to avoid frequent realloc
119 GrowableArray <Node *> spstack(C->unique()+8);
120 spstack.push(_root);
121 while ( spstack.is_nonempty() ) {
122 Node *n = spstack.pop();
123 if( !visited.test_set(n->_idx) ) { // Test node and flag it as visited
124 if( n->pinned() && !_bbs.lookup(n->_idx) ) { // Pinned? Nail it down!
125 assert( n->in(0), "pinned Node must have Control" );
126 // Before setting block replace block_proj control edge
127 replace_block_proj_ctrl(n);
128 Node *input = n->in(0);
129 while( !input->is_block_start() )
130 input = input->in(0);
131 Block *b = _bbs[input->_idx]; // Basic block of controlling input
132 schedule_node_into_block(n, b);
133 }
134 for( int i = n->req() - 1; i >= 0; --i ) { // For all inputs
135 if( n->in(i) != NULL )
136 spstack.push(n->in(i));
137 }
138 }
139 }
140 }
141
142 #ifdef ASSERT
143 // Assert that new input b2 is dominated by all previous inputs.
144 // Check this by by seeing that it is dominated by b1, the deepest
145 // input observed until b2.
146 static void assert_dom(Block* b1, Block* b2, Node* n, Block_Array &bbs) {
147 if (b1 == NULL) return;
148 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
149 Block* tmp = b2;
150 while (tmp != b1 && tmp != NULL) {
151 tmp = tmp->_idom;
152 }
153 if (tmp != b1) {
154 // Detected an unschedulable graph. Print some nice stuff and die.
155 tty->print_cr("!!! Unschedulable graph !!!");
156 for (uint j=0; j<n->len(); j++) { // For all inputs
157 Node* inn = n->in(j); // Get input
158 if (inn == NULL) continue; // Ignore NULL, missing inputs
159 Block* inb = bbs[inn->_idx];
160 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
161 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
162 inn->dump();
163 }
164 tty->print("Failing node: ");
165 n->dump();
166 assert(false, "unscheduable graph");
167 }
168 }
169 #endif
170
171 static Block* find_deepest_input(Node* n, Block_Array &bbs) {
172 // Find the last input dominated by all other inputs.
173 Block* deepb = NULL; // Deepest block so far
174 int deepb_dom_depth = 0;
175 for (uint k = 0; k < n->len(); k++) { // For all inputs
176 Node* inn = n->in(k); // Get input
177 if (inn == NULL) continue; // Ignore NULL, missing inputs
178 Block* inb = bbs[inn->_idx];
179 assert(inb != NULL, "must already have scheduled this input");
180 if (deepb_dom_depth < (int) inb->_dom_depth) {
181 // The new inb must be dominated by the previous deepb.
182 // The various inputs must be linearly ordered in the dom
183 // tree, or else there will not be a unique deepest block.
184 DEBUG_ONLY(assert_dom(deepb, inb, n, bbs));
185 deepb = inb; // Save deepest block
186 deepb_dom_depth = deepb->_dom_depth;
187 }
188 }
189 assert(deepb != NULL, "must be at least one input to n");
190 return deepb;
191 }
192
193
194 //------------------------------schedule_early---------------------------------
195 // Find the earliest Block any instruction can be placed in. Some instructions
196 // are pinned into Blocks. Unpinned instructions can appear in last block in
197 // which all their inputs occur.
198 bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) {
199 // Allocate stack with enough space to avoid frequent realloc
200 Node_Stack nstack(roots.Size() + 8); // (unique >> 1) + 24 from Java2D stats
201 // roots.push(_root); _root will be processed among C->top() inputs
202 roots.push(C->top());
203 visited.set(C->top()->_idx);
204
205 while (roots.size() != 0) {
206 // Use local variables nstack_top_n & nstack_top_i to cache values
207 // on stack's top.
208 Node *nstack_top_n = roots.pop();
209 uint nstack_top_i = 0;
210 //while_nstack_nonempty:
211 while (true) {
212 // Get parent node and next input's index from stack's top.
213 Node *n = nstack_top_n;
214 uint i = nstack_top_i;
215
216 if (i == 0) {
217 // Fixup some control. Constants without control get attached
218 // to root and nodes that use is_block_proj() nodes should be attached
219 // to the region that starts their block.
220 const Node *in0 = n->in(0);
221 if (in0 != NULL) { // Control-dependent?
222 replace_block_proj_ctrl(n);
223 } else { // n->in(0) == NULL
224 if (n->req() == 1) { // This guy is a constant with NO inputs?
225 n->set_req(0, _root);
226 }
227 }
228 }
229
230 // First, visit all inputs and force them to get a block. If an
231 // input is already in a block we quit following inputs (to avoid
232 // cycles). Instead we put that Node on a worklist to be handled
233 // later (since IT'S inputs may not have a block yet).
234 bool done = true; // Assume all n's inputs will be processed
235 while (i < n->len()) { // For all inputs
236 Node *in = n->in(i); // Get input
237 ++i;
238 if (in == NULL) continue; // Ignore NULL, missing inputs
239 int is_visited = visited.test_set(in->_idx);
240 if (!_bbs.lookup(in->_idx)) { // Missing block selection?
241 if (is_visited) {
242 // assert( !visited.test(in->_idx), "did not schedule early" );
243 return false;
244 }
245 nstack.push(n, i); // Save parent node and next input's index.
246 nstack_top_n = in; // Process current input now.
247 nstack_top_i = 0;
248 done = false; // Not all n's inputs processed.
249 break; // continue while_nstack_nonempty;
250 } else if (!is_visited) { // Input not yet visited?
251 roots.push(in); // Visit this guy later, using worklist
252 }
253 }
254 if (done) {
255 // All of n's inputs have been processed, complete post-processing.
256
257 // Some instructions are pinned into a block. These include Region,
258 // Phi, Start, Return, and other control-dependent instructions and
259 // any projections which depend on them.
260 if (!n->pinned()) {
261 // Set earliest legal block.
262 _bbs.map(n->_idx, find_deepest_input(n, _bbs));
263 } else {
264 assert(_bbs[n->_idx] == _bbs[n->in(0)->_idx], "Pinned Node should be at the same block as its control edge");
265 }
266
267 if (nstack.is_empty()) {
268 // Finished all nodes on stack.
269 // Process next node on the worklist 'roots'.
270 break;
271 }
272 // Get saved parent node and next input's index.
273 nstack_top_n = nstack.node();
274 nstack_top_i = nstack.index();
275 nstack.pop();
276 } // if (done)
277 } // while (true)
278 } // while (roots.size() != 0)
279 return true;
280 }
281
282 //------------------------------dom_lca----------------------------------------
283 // Find least common ancestor in dominator tree
284 // LCA is a current notion of LCA, to be raised above 'this'.
285 // As a convenient boundary condition, return 'this' if LCA is NULL.
286 // Find the LCA of those two nodes.
287 Block* Block::dom_lca(Block* LCA) {
288 if (LCA == NULL || LCA == this) return this;
289
290 Block* anc = this;
291 while (anc->_dom_depth > LCA->_dom_depth)
292 anc = anc->_idom; // Walk up till anc is as high as LCA
293
294 while (LCA->_dom_depth > anc->_dom_depth)
295 LCA = LCA->_idom; // Walk up till LCA is as high as anc
296
297 while (LCA != anc) { // Walk both up till they are the same
298 LCA = LCA->_idom;
299 anc = anc->_idom;
300 }
301
302 return LCA;
303 }
304
305 //--------------------------raise_LCA_above_use--------------------------------
306 // We are placing a definition, and have been given a def->use edge.
307 // The definition must dominate the use, so move the LCA upward in the
308 // dominator tree to dominate the use. If the use is a phi, adjust
309 // the LCA only with the phi input paths which actually use this def.
310 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, Block_Array &bbs) {
311 Block* buse = bbs[use->_idx];
312 if (buse == NULL) return LCA; // Unused killing Projs have no use block
313 if (!use->is_Phi()) return buse->dom_lca(LCA);
314 uint pmax = use->req(); // Number of Phi inputs
315 // Why does not this loop just break after finding the matching input to
316 // the Phi? Well...it's like this. I do not have true def-use/use-def
317 // chains. Means I cannot distinguish, from the def-use direction, which
318 // of many use-defs lead from the same use to the same def. That is, this
319 // Phi might have several uses of the same def. Each use appears in a
320 // different predecessor block. But when I enter here, I cannot distinguish
321 // which use-def edge I should find the predecessor block for. So I find
322 // them all. Means I do a little extra work if a Phi uses the same value
323 // more than once.
324 for (uint j=1; j<pmax; j++) { // For all inputs
325 if (use->in(j) == def) { // Found matching input?
326 Block* pred = bbs[buse->pred(j)->_idx];
327 LCA = pred->dom_lca(LCA);
328 }
329 }
330 return LCA;
331 }
332
333 //----------------------------raise_LCA_above_marks----------------------------
334 // Return a new LCA that dominates LCA and any of its marked predecessors.
335 // Search all my parents up to 'early' (exclusive), looking for predecessors
336 // which are marked with the given index. Return the LCA (in the dom tree)
337 // of all marked blocks. If there are none marked, return the original
338 // LCA.
339 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark,
340 Block* early, Block_Array &bbs) {
341 Block_List worklist;
342 worklist.push(LCA);
343 while (worklist.size() > 0) {
344 Block* mid = worklist.pop();
345 if (mid == early) continue; // stop searching here
346
347 // Test and set the visited bit.
348 if (mid->raise_LCA_visited() == mark) continue; // already visited
349
350 // Don't process the current LCA, otherwise the search may terminate early
351 if (mid != LCA && mid->raise_LCA_mark() == mark) {
352 // Raise the LCA.
353 LCA = mid->dom_lca(LCA);
354 if (LCA == early) break; // stop searching everywhere
355 assert(early->dominates(LCA), "early is high enough");
356 // Resume searching at that point, skipping intermediate levels.
357 worklist.push(LCA);
358 if (LCA == mid)
359 continue; // Don't mark as visited to avoid early termination.
360 } else {
361 // Keep searching through this block's predecessors.
362 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
363 Block* mid_parent = bbs[ mid->pred(j)->_idx ];
364 worklist.push(mid_parent);
365 }
366 }
367 mid->set_raise_LCA_visited(mark);
368 }
369 return LCA;
370 }
371
372 //--------------------------memory_early_block--------------------------------
373 // This is a variation of find_deepest_input, the heart of schedule_early.
374 // Find the "early" block for a load, if we considered only memory and
375 // address inputs, that is, if other data inputs were ignored.
376 //
377 // Because a subset of edges are considered, the resulting block will
378 // be earlier (at a shallower dom_depth) than the true schedule_early
379 // point of the node. We compute this earlier block as a more permissive
380 // site for anti-dependency insertion, but only if subsume_loads is enabled.
381 static Block* memory_early_block(Node* load, Block* early, Block_Array &bbs) {
382 Node* base;
383 Node* index;
384 Node* store = load->in(MemNode::Memory);
385 load->as_Mach()->memory_inputs(base, index);
386
387 assert(base != NodeSentinel && index != NodeSentinel,
388 "unexpected base/index inputs");
389
390 Node* mem_inputs[4];
391 int mem_inputs_length = 0;
392 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
393 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
394 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
395
396 // In the comparision below, add one to account for the control input,
397 // which may be null, but always takes up a spot in the in array.
398 if (mem_inputs_length + 1 < (int) load->req()) {
399 // This "load" has more inputs than just the memory, base and index inputs.
400 // For purposes of checking anti-dependences, we need to start
401 // from the early block of only the address portion of the instruction,
402 // and ignore other blocks that may have factored into the wider
403 // schedule_early calculation.
404 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
405
406 Block* deepb = NULL; // Deepest block so far
407 int deepb_dom_depth = 0;
408 for (int i = 0; i < mem_inputs_length; i++) {
409 Block* inb = bbs[mem_inputs[i]->_idx];
410 if (deepb_dom_depth < (int) inb->_dom_depth) {
411 // The new inb must be dominated by the previous deepb.
412 // The various inputs must be linearly ordered in the dom
413 // tree, or else there will not be a unique deepest block.
414 DEBUG_ONLY(assert_dom(deepb, inb, load, bbs));
415 deepb = inb; // Save deepest block
416 deepb_dom_depth = deepb->_dom_depth;
417 }
418 }
419 early = deepb;
420 }
421
422 return early;
423 }
424
425 //--------------------------insert_anti_dependences---------------------------
426 // A load may need to witness memory that nearby stores can overwrite.
427 // For each nearby store, either insert an "anti-dependence" edge
428 // from the load to the store, or else move LCA upward to force the
429 // load to (eventually) be scheduled in a block above the store.
430 //
431 // Do not add edges to stores on distinct control-flow paths;
432 // only add edges to stores which might interfere.
433 //
434 // Return the (updated) LCA. There will not be any possibly interfering
435 // store between the load's "early block" and the updated LCA.
436 // Any stores in the updated LCA will have new precedence edges
437 // back to the load. The caller is expected to schedule the load
438 // in the LCA, in which case the precedence edges will make LCM
439 // preserve anti-dependences. The caller may also hoist the load
440 // above the LCA, if it is not the early block.
441 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
442 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
443 assert(LCA != NULL, "");
444 DEBUG_ONLY(Block* LCA_orig = LCA);
445
446 // Compute the alias index. Loads and stores with different alias indices
447 // do not need anti-dependence edges.
448 uint load_alias_idx = C->get_alias_index(load->adr_type());
449 #ifdef ASSERT
450 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
451 (PrintOpto || VerifyAliases ||
452 PrintMiscellaneous && (WizardMode || Verbose))) {
453 // Load nodes should not consume all of memory.
454 // Reporting a bottom type indicates a bug in adlc.
455 // If some particular type of node validly consumes all of memory,
456 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
457 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
458 load->dump(2);
459 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
460 }
461 #endif
462 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
463 "String compare is only known 'load' that does not conflict with any stores");
464 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals),
465 "String equals is a 'load' that does not conflict with any stores");
466 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf),
467 "String indexOf is a 'load' that does not conflict with any stores");
468 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq),
469 "Arrays equals is a 'load' that do not conflict with any stores");
470
471 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
472 // It is impossible to spoil this load by putting stores before it,
473 // because we know that the stores will never update the value
474 // which 'load' must witness.
475 return LCA;
476 }
477
478 node_idx_t load_index = load->_idx;
479
480 // Note the earliest legal placement of 'load', as determined by
481 // by the unique point in the dom tree where all memory effects
482 // and other inputs are first available. (Computed by schedule_early.)
483 // For normal loads, 'early' is the shallowest place (dom graph wise)
484 // to look for anti-deps between this load and any store.
485 Block* early = _bbs[load_index];
486
487 // If we are subsuming loads, compute an "early" block that only considers
488 // memory or address inputs. This block may be different than the
489 // schedule_early block in that it could be at an even shallower depth in the
490 // dominator tree, and allow for a broader discovery of anti-dependences.
491 if (C->subsume_loads()) {
492 early = memory_early_block(load, early, _bbs);
493 }
494
495 ResourceArea *area = Thread::current()->resource_area();
496 Node_List worklist_mem(area); // prior memory state to store
497 Node_List worklist_store(area); // possible-def to explore
498 Node_List worklist_visited(area); // visited mergemem nodes
499 Node_List non_early_stores(area); // all relevant stores outside of early
500 bool must_raise_LCA = false;
501
502 #ifdef TRACK_PHI_INPUTS
503 // %%% This extra checking fails because MergeMem nodes are not GVNed.
504 // Provide "phi_inputs" to check if every input to a PhiNode is from the
505 // original memory state. This indicates a PhiNode for which should not
506 // prevent the load from sinking. For such a block, set_raise_LCA_mark
507 // may be overly conservative.
508 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
509 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
510 #endif
511
512 // 'load' uses some memory state; look for users of the same state.
513 // Recurse through MergeMem nodes to the stores that use them.
514
515 // Each of these stores is a possible definition of memory
516 // that 'load' needs to use. We need to force 'load'
517 // to occur before each such store. When the store is in
518 // the same block as 'load', we insert an anti-dependence
519 // edge load->store.
520
521 // The relevant stores "nearby" the load consist of a tree rooted
522 // at initial_mem, with internal nodes of type MergeMem.
523 // Therefore, the branches visited by the worklist are of this form:
524 // initial_mem -> (MergeMem ->)* store
525 // The anti-dependence constraints apply only to the fringe of this tree.
526
527 Node* initial_mem = load->in(MemNode::Memory);
528 worklist_store.push(initial_mem);
529 worklist_visited.push(initial_mem);
530 worklist_mem.push(NULL);
531 while (worklist_store.size() > 0) {
532 // Examine a nearby store to see if it might interfere with our load.
533 Node* mem = worklist_mem.pop();
534 Node* store = worklist_store.pop();
535 uint op = store->Opcode();
536
537 // MergeMems do not directly have anti-deps.
538 // Treat them as internal nodes in a forward tree of memory states,
539 // the leaves of which are each a 'possible-def'.
540 if (store == initial_mem // root (exclusive) of tree we are searching
541 || op == Op_MergeMem // internal node of tree we are searching
542 ) {
543 mem = store; // It's not a possibly interfering store.
544 if (store == initial_mem)
545 initial_mem = NULL; // only process initial memory once
546
547 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
548 store = mem->fast_out(i);
549 if (store->is_MergeMem()) {
550 // Be sure we don't get into combinatorial problems.
551 // (Allow phis to be repeated; they can merge two relevant states.)
552 uint j = worklist_visited.size();
553 for (; j > 0; j--) {
554 if (worklist_visited.at(j-1) == store) break;
555 }
556 if (j > 0) continue; // already on work list; do not repeat
557 worklist_visited.push(store);
558 }
559 worklist_mem.push(mem);
560 worklist_store.push(store);
561 }
562 continue;
563 }
564
565 if (op == Op_MachProj || op == Op_Catch) continue;
566 if (store->needs_anti_dependence_check()) continue; // not really a store
567
568 // Compute the alias index. Loads and stores with different alias
569 // indices do not need anti-dependence edges. Wide MemBar's are
570 // anti-dependent on everything (except immutable memories).
571 const TypePtr* adr_type = store->adr_type();
572 if (!C->can_alias(adr_type, load_alias_idx)) continue;
573
574 // Most slow-path runtime calls do NOT modify Java memory, but
575 // they can block and so write Raw memory.
576 if (store->is_Mach()) {
577 MachNode* mstore = store->as_Mach();
578 if (load_alias_idx != Compile::AliasIdxRaw) {
579 // Check for call into the runtime using the Java calling
580 // convention (and from there into a wrapper); it has no
581 // _method. Can't do this optimization for Native calls because
582 // they CAN write to Java memory.
583 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
584 assert(mstore->is_MachSafePoint(), "");
585 MachSafePointNode* ms = (MachSafePointNode*) mstore;
586 assert(ms->is_MachCallJava(), "");
587 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
588 if (mcj->_method == NULL) {
589 // These runtime calls do not write to Java visible memory
590 // (other than Raw) and so do not require anti-dependence edges.
591 continue;
592 }
593 }
594 // Same for SafePoints: they read/write Raw but only read otherwise.
595 // This is basically a workaround for SafePoints only defining control
596 // instead of control + memory.
597 if (mstore->ideal_Opcode() == Op_SafePoint)
598 continue;
599 } else {
600 // Some raw memory, such as the load of "top" at an allocation,
601 // can be control dependent on the previous safepoint. See
602 // comments in GraphKit::allocate_heap() about control input.
603 // Inserting an anti-dep between such a safepoint and a use
604 // creates a cycle, and will cause a subsequent failure in
605 // local scheduling. (BugId 4919904)
606 // (%%% How can a control input be a safepoint and not a projection??)
607 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
608 continue;
609 }
610 }
611
612 // Identify a block that the current load must be above,
613 // or else observe that 'store' is all the way up in the
614 // earliest legal block for 'load'. In the latter case,
615 // immediately insert an anti-dependence edge.
616 Block* store_block = _bbs[store->_idx];
617 assert(store_block != NULL, "unused killing projections skipped above");
618
619 if (store->is_Phi()) {
620 // 'load' uses memory which is one (or more) of the Phi's inputs.
621 // It must be scheduled not before the Phi, but rather before
622 // each of the relevant Phi inputs.
623 //
624 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
625 // we mark each corresponding predecessor block and do a combined
626 // hoisting operation later (raise_LCA_above_marks).
627 //
628 // Do not assert(store_block != early, "Phi merging memory after access")
629 // PhiNode may be at start of block 'early' with backedge to 'early'
630 DEBUG_ONLY(bool found_match = false);
631 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
632 if (store->in(j) == mem) { // Found matching input?
633 DEBUG_ONLY(found_match = true);
634 Block* pred_block = _bbs[store_block->pred(j)->_idx];
635 if (pred_block != early) {
636 // If any predecessor of the Phi matches the load's "early block",
637 // we do not need a precedence edge between the Phi and 'load'
638 // since the load will be forced into a block preceding the Phi.
639 pred_block->set_raise_LCA_mark(load_index);
640 assert(!LCA_orig->dominates(pred_block) ||
641 early->dominates(pred_block), "early is high enough");
642 must_raise_LCA = true;
643 } else {
644 // anti-dependent upon PHI pinned below 'early', no edge needed
645 LCA = early; // but can not schedule below 'early'
646 }
647 }
648 }
649 assert(found_match, "no worklist bug");
650 #ifdef TRACK_PHI_INPUTS
651 #ifdef ASSERT
652 // This assert asks about correct handling of PhiNodes, which may not
653 // have all input edges directly from 'mem'. See BugId 4621264
654 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
655 // Increment by exactly one even if there are multiple copies of 'mem'
656 // coming into the phi, because we will run this block several times
657 // if there are several copies of 'mem'. (That's how DU iterators work.)
658 phi_inputs.at_put(store->_idx, num_mem_inputs);
659 assert(PhiNode::Input + num_mem_inputs < store->req(),
660 "Expect at least one phi input will not be from original memory state");
661 #endif //ASSERT
662 #endif //TRACK_PHI_INPUTS
663 } else if (store_block != early) {
664 // 'store' is between the current LCA and earliest possible block.
665 // Label its block, and decide later on how to raise the LCA
666 // to include the effect on LCA of this store.
667 // If this store's block gets chosen as the raised LCA, we
668 // will find him on the non_early_stores list and stick him
669 // with a precedence edge.
670 // (But, don't bother if LCA is already raised all the way.)
671 if (LCA != early) {
672 store_block->set_raise_LCA_mark(load_index);
673 must_raise_LCA = true;
674 non_early_stores.push(store);
675 }
676 } else {
677 // Found a possibly-interfering store in the load's 'early' block.
678 // This means 'load' cannot sink at all in the dominator tree.
679 // Add an anti-dep edge, and squeeze 'load' into the highest block.
680 assert(store != load->in(0), "dependence cycle found");
681 if (verify) {
682 assert(store->find_edge(load) != -1, "missing precedence edge");
683 } else {
684 store->add_prec(load);
685 }
686 LCA = early;
687 // This turns off the process of gathering non_early_stores.
688 }
689 }
690 // (Worklist is now empty; all nearby stores have been visited.)
691
692 // Finished if 'load' must be scheduled in its 'early' block.
693 // If we found any stores there, they have already been given
694 // precedence edges.
695 if (LCA == early) return LCA;
696
697 // We get here only if there are no possibly-interfering stores
698 // in the load's 'early' block. Move LCA up above all predecessors
699 // which contain stores we have noted.
700 //
701 // The raised LCA block can be a home to such interfering stores,
702 // but its predecessors must not contain any such stores.
703 //
704 // The raised LCA will be a lower bound for placing the load,
705 // preventing the load from sinking past any block containing
706 // a store that may invalidate the memory state required by 'load'.
707 if (must_raise_LCA)
708 LCA = raise_LCA_above_marks(LCA, load->_idx, early, _bbs);
709 if (LCA == early) return LCA;
710
711 // Insert anti-dependence edges from 'load' to each store
712 // in the non-early LCA block.
713 // Mine the non_early_stores list for such stores.
714 if (LCA->raise_LCA_mark() == load_index) {
715 while (non_early_stores.size() > 0) {
716 Node* store = non_early_stores.pop();
717 Block* store_block = _bbs[store->_idx];
718 if (store_block == LCA) {
719 // add anti_dependence from store to load in its own block
720 assert(store != load->in(0), "dependence cycle found");
721 if (verify) {
722 assert(store->find_edge(load) != -1, "missing precedence edge");
723 } else {
724 store->add_prec(load);
725 }
726 } else {
727 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
728 // Any other stores we found must be either inside the new LCA
729 // or else outside the original LCA. In the latter case, they
730 // did not interfere with any use of 'load'.
731 assert(LCA->dominates(store_block)
732 || !LCA_orig->dominates(store_block), "no stray stores");
733 }
734 }
735 }
736
737 // Return the highest block containing stores; any stores
738 // within that block have been given anti-dependence edges.
739 return LCA;
740 }
741
742 // This class is used to iterate backwards over the nodes in the graph.
743
744 class Node_Backward_Iterator {
745
746 private:
747 Node_Backward_Iterator();
748
749 public:
750 // Constructor for the iterator
751 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs);
752
753 // Postincrement operator to iterate over the nodes
754 Node *next();
755
756 private:
757 VectorSet &_visited;
758 Node_List &_stack;
759 Block_Array &_bbs;
760 };
761
762 // Constructor for the Node_Backward_Iterator
763 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs )
764 : _visited(visited), _stack(stack), _bbs(bbs) {
765 // The stack should contain exactly the root
766 stack.clear();
767 stack.push(root);
768
769 // Clear the visited bits
770 visited.Clear();
771 }
772
773 // Iterator for the Node_Backward_Iterator
774 Node *Node_Backward_Iterator::next() {
775
776 // If the _stack is empty, then just return NULL: finished.
777 if ( !_stack.size() )
778 return NULL;
779
780 // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been
781 // made stateless, so I do not need to record the index 'i' on my _stack.
782 // Instead I visit all users each time, scanning for unvisited users.
783 // I visit unvisited not-anti-dependence users first, then anti-dependent
784 // children next.
785 Node *self = _stack.pop();
786
787 // I cycle here when I am entering a deeper level of recursion.
788 // The key variable 'self' was set prior to jumping here.
789 while( 1 ) {
790
791 _visited.set(self->_idx);
792
793 // Now schedule all uses as late as possible.
794 uint src = self->is_Proj() ? self->in(0)->_idx : self->_idx;
795 uint src_rpo = _bbs[src]->_rpo;
796
797 // Schedule all nodes in a post-order visit
798 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
799
800 // Scan for unvisited nodes
801 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
802 // For all uses, schedule late
803 Node* n = self->fast_out(i); // Use
804
805 // Skip already visited children
806 if ( _visited.test(n->_idx) )
807 continue;
808
809 // do not traverse backward control edges
810 Node *use = n->is_Proj() ? n->in(0) : n;
811 uint use_rpo = _bbs[use->_idx]->_rpo;
812
813 if ( use_rpo < src_rpo )
814 continue;
815
816 // Phi nodes always precede uses in a basic block
817 if ( use_rpo == src_rpo && use->is_Phi() )
818 continue;
819
820 unvisited = n; // Found unvisited
821
822 // Check for possible-anti-dependent
823 if( !n->needs_anti_dependence_check() )
824 break; // Not visited, not anti-dep; schedule it NOW
825 }
826
827 // Did I find an unvisited not-anti-dependent Node?
828 if ( !unvisited )
829 break; // All done with children; post-visit 'self'
830
831 // Visit the unvisited Node. Contains the obvious push to
832 // indicate I'm entering a deeper level of recursion. I push the
833 // old state onto the _stack and set a new state and loop (recurse).
834 _stack.push(self);
835 self = unvisited;
836 } // End recursion loop
837
838 return self;
839 }
840
841 //------------------------------ComputeLatenciesBackwards----------------------
842 // Compute the latency of all the instructions.
843 void PhaseCFG::ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack) {
844 #ifndef PRODUCT
845 if (trace_opto_pipelining())
846 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
847 #endif
848
849 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs);
850 Node *n;
851
852 // Walk over all the nodes from last to first
853 while (n = iter.next()) {
854 // Set the latency for the definitions of this instruction
855 partial_latency_of_defs(n);
856 }
857 } // end ComputeLatenciesBackwards
858
859 //------------------------------partial_latency_of_defs------------------------
860 // Compute the latency impact of this node on all defs. This computes
861 // a number that increases as we approach the beginning of the routine.
862 void PhaseCFG::partial_latency_of_defs(Node *n) {
863 // Set the latency for this instruction
864 #ifndef PRODUCT
865 if (trace_opto_pipelining()) {
866 tty->print("# latency_to_inputs: node_latency[%d] = %d for node",
867 n->_idx, _node_latency->at_grow(n->_idx));
868 dump();
869 }
870 #endif
871
872 if (n->is_Proj())
873 n = n->in(0);
874
875 if (n->is_Root())
876 return;
877
878 uint nlen = n->len();
879 uint use_latency = _node_latency->at_grow(n->_idx);
880 uint use_pre_order = _bbs[n->_idx]->_pre_order;
881
882 for ( uint j=0; j<nlen; j++ ) {
883 Node *def = n->in(j);
884
885 if (!def || def == n)
886 continue;
887
888 // Walk backwards thru projections
889 if (def->is_Proj())
890 def = def->in(0);
891
892 #ifndef PRODUCT
893 if (trace_opto_pipelining()) {
894 tty->print("# in(%2d): ", j);
895 def->dump();
896 }
897 #endif
898
899 // If the defining block is not known, assume it is ok
900 Block *def_block = _bbs[def->_idx];
901 uint def_pre_order = def_block ? def_block->_pre_order : 0;
902
903 if ( (use_pre_order < def_pre_order) ||
904 (use_pre_order == def_pre_order && n->is_Phi()) )
905 continue;
906
907 uint delta_latency = n->latency(j);
908 uint current_latency = delta_latency + use_latency;
909
910 if (_node_latency->at_grow(def->_idx) < current_latency) {
911 _node_latency->at_put_grow(def->_idx, current_latency);
912 }
913
914 #ifndef PRODUCT
915 if (trace_opto_pipelining()) {
916 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, node_latency[%d] = %d",
917 use_latency, j, delta_latency, current_latency, def->_idx,
918 _node_latency->at_grow(def->_idx));
919 }
920 #endif
921 }
922 }
923
924 //------------------------------latency_from_use-------------------------------
925 // Compute the latency of a specific use
926 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
927 // If self-reference, return no latency
928 if (use == n || use->is_Root())
929 return 0;
930
931 uint def_pre_order = _bbs[def->_idx]->_pre_order;
932 uint latency = 0;
933
934 // If the use is not a projection, then it is simple...
935 if (!use->is_Proj()) {
936 #ifndef PRODUCT
937 if (trace_opto_pipelining()) {
938 tty->print("# out(): ");
939 use->dump();
940 }
941 #endif
942
943 uint use_pre_order = _bbs[use->_idx]->_pre_order;
944
945 if (use_pre_order < def_pre_order)
946 return 0;
947
948 if (use_pre_order == def_pre_order && use->is_Phi())
949 return 0;
950
951 uint nlen = use->len();
952 uint nl = _node_latency->at_grow(use->_idx);
953
954 for ( uint j=0; j<nlen; j++ ) {
955 if (use->in(j) == n) {
956 // Change this if we want local latencies
957 uint ul = use->latency(j);
958 uint l = ul + nl;
959 if (latency < l) latency = l;
960 #ifndef PRODUCT
961 if (trace_opto_pipelining()) {
962 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
963 nl, j, ul, l, latency);
964 }
965 #endif
966 }
967 }
968 } else {
969 // This is a projection, just grab the latency of the use(s)
970 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
971 uint l = latency_from_use(use, def, use->fast_out(j));
972 if (latency < l) latency = l;
973 }
974 }
975
976 return latency;
977 }
978
979 //------------------------------latency_from_uses------------------------------
980 // Compute the latency of this instruction relative to all of it's uses.
981 // This computes a number that increases as we approach the beginning of the
982 // routine.
983 void PhaseCFG::latency_from_uses(Node *n) {
984 // Set the latency for this instruction
985 #ifndef PRODUCT
986 if (trace_opto_pipelining()) {
987 tty->print("# latency_from_outputs: node_latency[%d] = %d for node",
988 n->_idx, _node_latency->at_grow(n->_idx));
989 dump();
990 }
991 #endif
992 uint latency=0;
993 const Node *def = n->is_Proj() ? n->in(0): n;
994
995 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
996 uint l = latency_from_use(n, def, n->fast_out(i));
997
998 if (latency < l) latency = l;
999 }
1000
1001 _node_latency->at_put_grow(n->_idx, latency);
1002 }
1003
1004 //------------------------------hoist_to_cheaper_block-------------------------
1005 // Pick a block for node self, between early and LCA, that is a cheaper
1006 // alternative to LCA.
1007 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
1008 const double delta = 1+PROB_UNLIKELY_MAG(4);
1009 Block* least = LCA;
1010 double least_freq = least->_freq;
1011 uint target = _node_latency->at_grow(self->_idx);
1012 uint start_latency = _node_latency->at_grow(LCA->_nodes[0]->_idx);
1013 uint end_latency = _node_latency->at_grow(LCA->_nodes[LCA->end_idx()]->_idx);
1014 bool in_latency = (target <= start_latency);
1015 const Block* root_block = _bbs[_root->_idx];
1016
1017 // Turn off latency scheduling if scheduling is just plain off
1018 if (!C->do_scheduling())
1019 in_latency = true;
1020
1021 // Do not hoist (to cover latency) instructions which target a
1022 // single register. Hoisting stretches the live range of the
1023 // single register and may force spilling.
1024 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1025 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
1026 in_latency = true;
1027
1028 #ifndef PRODUCT
1029 if (trace_opto_pipelining()) {
1030 tty->print("# Find cheaper block for latency %d: ",
1031 _node_latency->at_grow(self->_idx));
1032 self->dump();
1033 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1034 LCA->_pre_order,
1035 LCA->_nodes[0]->_idx,
1036 start_latency,
1037 LCA->_nodes[LCA->end_idx()]->_idx,
1038 end_latency,
1039 least_freq);
1040 }
1041 #endif
1042
1043 // Walk up the dominator tree from LCA (Lowest common ancestor) to
1044 // the earliest legal location. Capture the least execution frequency.
1045 while (LCA != early) {
1046 LCA = LCA->_idom; // Follow up the dominator tree
1047
1048 if (LCA == NULL) {
1049 // Bailout without retry
1050 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1051 return least;
1052 }
1053
1054 // Don't hoist machine instructions to the root basic block
1055 if (mach && LCA == root_block)
1056 break;
1057
1058 uint start_lat = _node_latency->at_grow(LCA->_nodes[0]->_idx);
1059 uint end_idx = LCA->end_idx();
1060 uint end_lat = _node_latency->at_grow(LCA->_nodes[end_idx]->_idx);
1061 double LCA_freq = LCA->_freq;
1062 #ifndef PRODUCT
1063 if (trace_opto_pipelining()) {
1064 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1065 LCA->_pre_order, LCA->_nodes[0]->_idx, start_lat, end_idx, end_lat, LCA_freq);
1066 }
1067 #endif
1068 if (LCA_freq < least_freq || // Better Frequency
1069 ( !in_latency && // No block containing latency
1070 LCA_freq < least_freq * delta && // No worse frequency
1071 target >= end_lat && // within latency range
1072 !self->is_iteratively_computed() ) // But don't hoist IV increments
1073 // because they may end up above other uses of their phi forcing
1074 // their result register to be different from their input.
1075 ) {
1076 least = LCA; // Found cheaper block
1077 least_freq = LCA_freq;
1078 start_latency = start_lat;
1079 end_latency = end_lat;
1080 if (target <= start_lat)
1081 in_latency = true;
1082 }
1083 }
1084
1085 #ifndef PRODUCT
1086 if (trace_opto_pipelining()) {
1087 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1088 least->_pre_order, start_latency, least_freq);
1089 }
1090 #endif
1091
1092 // See if the latency needs to be updated
1093 if (target < end_latency) {
1094 #ifndef PRODUCT
1095 if (trace_opto_pipelining()) {
1096 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1097 }
1098 #endif
1099 _node_latency->at_put_grow(self->_idx, end_latency);
1100 partial_latency_of_defs(self);
1101 }
1102
1103 return least;
1104 }
1105
1106
1107 //------------------------------schedule_late-----------------------------------
1108 // Now schedule all codes as LATE as possible. This is the LCA in the
1109 // dominator tree of all USES of a value. Pick the block with the least
1110 // loop nesting depth that is lowest in the dominator tree.
1111 extern const char must_clone[];
1112 void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) {
1113 #ifndef PRODUCT
1114 if (trace_opto_pipelining())
1115 tty->print("\n#---- schedule_late ----\n");
1116 #endif
1117
1118 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs);
1119 Node *self;
1120
1121 // Walk over all the nodes from last to first
1122 while (self = iter.next()) {
1123 Block* early = _bbs[self->_idx]; // Earliest legal placement
1124
1125 if (self->is_top()) {
1126 // Top node goes in bb #2 with other constants.
1127 // It must be special-cased, because it has no out edges.
1128 early->add_inst(self);
1129 continue;
1130 }
1131
1132 // No uses, just terminate
1133 if (self->outcnt() == 0) {
1134 assert(self->Opcode() == Op_MachProj, "sanity");
1135 continue; // Must be a dead machine projection
1136 }
1137
1138 // If node is pinned in the block, then no scheduling can be done.
1139 if( self->pinned() ) // Pinned in block?
1140 continue;
1141
1142 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1143 if (mach) {
1144 switch (mach->ideal_Opcode()) {
1145 case Op_CreateEx:
1146 // Don't move exception creation
1147 early->add_inst(self);
1148 continue;
1149 break;
1150 case Op_CheckCastPP:
1151 // Don't move CheckCastPP nodes away from their input, if the input
1152 // is a rawptr (5071820).
1153 Node *def = self->in(1);
1154 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1155 early->add_inst(self);
1156 #ifdef ASSERT
1157 _raw_oops.push(def);
1158 #endif
1159 continue;
1160 }
1161 break;
1162 }
1163 }
1164
1165 // Gather LCA of all uses
1166 Block *LCA = NULL;
1167 {
1168 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1169 // For all uses, find LCA
1170 Node* use = self->fast_out(i);
1171 LCA = raise_LCA_above_use(LCA, use, self, _bbs);
1172 }
1173 } // (Hide defs of imax, i from rest of block.)
1174
1175 // Place temps in the block of their use. This isn't a
1176 // requirement for correctness but it reduces useless
1177 // interference between temps and other nodes.
1178 if (mach != NULL && mach->is_MachTemp()) {
1179 _bbs.map(self->_idx, LCA);
1180 LCA->add_inst(self);
1181 continue;
1182 }
1183
1184 // Check if 'self' could be anti-dependent on memory
1185 if (self->needs_anti_dependence_check()) {
1186 // Hoist LCA above possible-defs and insert anti-dependences to
1187 // defs in new LCA block.
1188 LCA = insert_anti_dependences(LCA, self);
1189 }
1190
1191 if (early->_dom_depth > LCA->_dom_depth) {
1192 // Somehow the LCA has moved above the earliest legal point.
1193 // (One way this can happen is via memory_early_block.)
1194 if (C->subsume_loads() == true && !C->failing()) {
1195 // Retry with subsume_loads == false
1196 // If this is the first failure, the sentinel string will "stick"
1197 // to the Compile object, and the C2Compiler will see it and retry.
1198 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1199 } else {
1200 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1201 C->record_method_not_compilable("late schedule failed: incorrect graph");
1202 }
1203 return;
1204 }
1205
1206 // If there is no opportunity to hoist, then we're done.
1207 bool try_to_hoist = (LCA != early);
1208
1209 // Must clone guys stay next to use; no hoisting allowed.
1210 // Also cannot hoist guys that alter memory or are otherwise not
1211 // allocatable (hoisting can make a value live longer, leading to
1212 // anti and output dependency problems which are normally resolved
1213 // by the register allocator giving everyone a different register).
1214 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1215 try_to_hoist = false;
1216
1217 Block* late = NULL;
1218 if (try_to_hoist) {
1219 // Now find the block with the least execution frequency.
1220 // Start at the latest schedule and work up to the earliest schedule
1221 // in the dominator tree. Thus the Node will dominate all its uses.
1222 late = hoist_to_cheaper_block(LCA, early, self);
1223 } else {
1224 // Just use the LCA of the uses.
1225 late = LCA;
1226 }
1227
1228 // Put the node into target block
1229 schedule_node_into_block(self, late);
1230
1231 #ifdef ASSERT
1232 if (self->needs_anti_dependence_check()) {
1233 // since precedence edges are only inserted when we're sure they
1234 // are needed make sure that after placement in a block we don't
1235 // need any new precedence edges.
1236 verify_anti_dependences(late, self);
1237 }
1238 #endif
1239 } // Loop until all nodes have been visited
1240
1241 } // end ScheduleLate
1242
1243 //------------------------------GlobalCodeMotion-------------------------------
1244 void PhaseCFG::GlobalCodeMotion( Matcher &matcher, uint unique, Node_List &proj_list ) {
1245 ResourceMark rm;
1246
1247 #ifndef PRODUCT
1248 if (trace_opto_pipelining()) {
1249 tty->print("\n---- Start GlobalCodeMotion ----\n");
1250 }
1251 #endif
1252
1253 // Initialize the bbs.map for things on the proj_list
1254 uint i;
1255 for( i=0; i < proj_list.size(); i++ )
1256 _bbs.map(proj_list[i]->_idx, NULL);
1257
1258 // Set the basic block for Nodes pinned into blocks
1259 Arena *a = Thread::current()->resource_area();
1260 VectorSet visited(a);
1261 schedule_pinned_nodes( visited );
1262
1263 // Find the earliest Block any instruction can be placed in. Some
1264 // instructions are pinned into Blocks. Unpinned instructions can
1265 // appear in last block in which all their inputs occur.
1266 visited.Clear();
1267 Node_List stack(a);
1268 stack.map( (unique >> 1) + 16, NULL); // Pre-grow the list
1269 if (!schedule_early(visited, stack)) {
1270 // Bailout without retry
1271 C->record_method_not_compilable("early schedule failed");
1272 return;
1273 }
1274
1275 // Build Def-Use edges.
1276 proj_list.push(_root); // Add real root as another root
1277 proj_list.pop();
1278
1279 // Compute the latency information (via backwards walk) for all the
1280 // instructions in the graph
1281 _node_latency = new GrowableArray<uint>(); // resource_area allocation
1282
1283 if( C->do_scheduling() )
1284 ComputeLatenciesBackwards(visited, stack);
1285
1286 // Now schedule all codes as LATE as possible. This is the LCA in the
1287 // dominator tree of all USES of a value. Pick the block with the least
1288 // loop nesting depth that is lowest in the dominator tree.
1289 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1290 schedule_late(visited, stack);
1291 if( C->failing() ) {
1292 // schedule_late fails only when graph is incorrect.
1293 assert(!VerifyGraphEdges, "verification should have failed");
1294 return;
1295 }
1296
1297 unique = C->unique();
1298
1299 #ifndef PRODUCT
1300 if (trace_opto_pipelining()) {
1301 tty->print("\n---- Detect implicit null checks ----\n");
1302 }
1303 #endif
1304
1305 // Detect implicit-null-check opportunities. Basically, find NULL checks
1306 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1307 // I can generate a memory op if there is not one nearby.
1308 if (C->is_method_compilation()) {
1309 // Don't do it for natives, adapters, or runtime stubs
1310 int allowed_reasons = 0;
1311 // ...and don't do it when there have been too many traps, globally.
1312 for (int reason = (int)Deoptimization::Reason_none+1;
1313 reason < Compile::trapHistLength; reason++) {
1314 assert(reason < BitsPerInt, "recode bit map");
1315 if (!C->too_many_traps((Deoptimization::DeoptReason) reason))
1316 allowed_reasons |= nth_bit(reason);
1317 }
1318 // By reversing the loop direction we get a very minor gain on mpegaudio.
1319 // Feel free to revert to a forward loop for clarity.
1320 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1321 for( int i= matcher._null_check_tests.size()-2; i>=0; i-=2 ) {
1322 Node *proj = matcher._null_check_tests[i ];
1323 Node *val = matcher._null_check_tests[i+1];
1324 _bbs[proj->_idx]->implicit_null_check(this, proj, val, allowed_reasons);
1325 // The implicit_null_check will only perform the transformation
1326 // if the null branch is truly uncommon, *and* it leads to an
1327 // uncommon trap. Combined with the too_many_traps guards
1328 // above, this prevents SEGV storms reported in 6366351,
1329 // by recompiling offending methods without this optimization.
1330 }
1331 }
1332
1333 #ifndef PRODUCT
1334 if (trace_opto_pipelining()) {
1335 tty->print("\n---- Start Local Scheduling ----\n");
1336 }
1337 #endif
1338
1339 // Schedule locally. Right now a simple topological sort.
1340 // Later, do a real latency aware scheduler.
1341 int *ready_cnt = NEW_RESOURCE_ARRAY(int,C->unique());
1342 memset( ready_cnt, -1, C->unique() * sizeof(int) );
1343 visited.Clear();
1344 for (i = 0; i < _num_blocks; i++) {
1345 if (!_blocks[i]->schedule_local(this, matcher, ready_cnt, visited)) {
1346 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1347 C->record_method_not_compilable("local schedule failed");
1348 }
1349 return;
1350 }
1351 }
1352
1353 // If we inserted any instructions between a Call and his CatchNode,
1354 // clone the instructions on all paths below the Catch.
1355 for( i=0; i < _num_blocks; i++ )
1356 _blocks[i]->call_catch_cleanup(_bbs);
1357
1358 #ifndef PRODUCT
1359 if (trace_opto_pipelining()) {
1360 tty->print("\n---- After GlobalCodeMotion ----\n");
1361 for (uint i = 0; i < _num_blocks; i++) {
1362 _blocks[i]->dump();
1363 }
1364 }
1365 #endif
1366 // Dead.
1367 _node_latency = (GrowableArray<uint> *)0xdeadbeef;
1368 }
1369
1370
1371 //------------------------------Estimate_Block_Frequency-----------------------
1372 // Estimate block frequencies based on IfNode probabilities.
1373 void PhaseCFG::Estimate_Block_Frequency() {
1374
1375 // Force conditional branches leading to uncommon traps to be unlikely,
1376 // not because we get to the uncommon_trap with less relative frequency,
1377 // but because an uncommon_trap typically causes a deopt, so we only get
1378 // there once.
1379 if (C->do_freq_based_layout()) {
1380 Block_List worklist;
1381 Block* root_blk = _blocks[0];
1382 for (uint i = 1; i < root_blk->num_preds(); i++) {
1383 Block *pb = _bbs[root_blk->pred(i)->_idx];
1384 if (pb->has_uncommon_code()) {
1385 worklist.push(pb);
1386 }
1387 }
1388 while (worklist.size() > 0) {
1389 Block* uct = worklist.pop();
1390 if (uct == _broot) continue;
1391 for (uint i = 1; i < uct->num_preds(); i++) {
1392 Block *pb = _bbs[uct->pred(i)->_idx];
1393 if (pb->_num_succs == 1) {
1394 worklist.push(pb);
1395 } else if (pb->num_fall_throughs() == 2) {
1396 pb->update_uncommon_branch(uct);
1397 }
1398 }
1399 }
1400 }
1401
1402 // Create the loop tree and calculate loop depth.
1403 _root_loop = create_loop_tree();
1404 _root_loop->compute_loop_depth(0);
1405
1406 // Compute block frequency of each block, relative to a single loop entry.
1407 _root_loop->compute_freq();
1408
1409 // Adjust all frequencies to be relative to a single method entry
1410 _root_loop->_freq = 1.0;
1411 _root_loop->scale_freq();
1412
1413 // Save outmost loop frequency for LRG frequency threshold
1414 _outer_loop_freq = _root_loop->outer_loop_freq();
1415
1416 // force paths ending at uncommon traps to be infrequent
1417 if (!C->do_freq_based_layout()) {
1418 Block_List worklist;
1419 Block* root_blk = _blocks[0];
1420 for (uint i = 1; i < root_blk->num_preds(); i++) {
1421 Block *pb = _bbs[root_blk->pred(i)->_idx];
1422 if (pb->has_uncommon_code()) {
1423 worklist.push(pb);
1424 }
1425 }
1426 while (worklist.size() > 0) {
1427 Block* uct = worklist.pop();
1428 uct->_freq = PROB_MIN;
1429 for (uint i = 1; i < uct->num_preds(); i++) {
1430 Block *pb = _bbs[uct->pred(i)->_idx];
1431 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1432 worklist.push(pb);
1433 }
1434 }
1435 }
1436 }
1437
1438 #ifdef ASSERT
1439 for (uint i = 0; i < _num_blocks; i++ ) {
1440 Block *b = _blocks[i];
1441 assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency");
1442 }
1443 #endif
1444
1445 #ifndef PRODUCT
1446 if (PrintCFGBlockFreq) {
1447 tty->print_cr("CFG Block Frequencies");
1448 _root_loop->dump_tree();
1449 if (Verbose) {
1450 tty->print_cr("PhaseCFG dump");
1451 dump();
1452 tty->print_cr("Node dump");
1453 _root->dump(99999);
1454 }
1455 }
1456 #endif
1457 }
1458
1459 //----------------------------create_loop_tree--------------------------------
1460 // Create a loop tree from the CFG
1461 CFGLoop* PhaseCFG::create_loop_tree() {
1462
1463 #ifdef ASSERT
1464 assert( _blocks[0] == _broot, "" );
1465 for (uint i = 0; i < _num_blocks; i++ ) {
1466 Block *b = _blocks[i];
1467 // Check that _loop field are clear...we could clear them if not.
1468 assert(b->_loop == NULL, "clear _loop expected");
1469 // Sanity check that the RPO numbering is reflected in the _blocks array.
1470 // It doesn't have to be for the loop tree to be built, but if it is not,
1471 // then the blocks have been reordered since dom graph building...which
1472 // may question the RPO numbering
1473 assert(b->_rpo == i, "unexpected reverse post order number");
1474 }
1475 #endif
1476
1477 int idct = 0;
1478 CFGLoop* root_loop = new CFGLoop(idct++);
1479
1480 Block_List worklist;
1481
1482 // Assign blocks to loops
1483 for(uint i = _num_blocks - 1; i > 0; i-- ) { // skip Root block
1484 Block *b = _blocks[i];
1485
1486 if (b->head()->is_Loop()) {
1487 Block* loop_head = b;
1488 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1489 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1490 Block* tail = _bbs[tail_n->_idx];
1491
1492 // Defensively filter out Loop nodes for non-single-entry loops.
1493 // For all reasonable loops, the head occurs before the tail in RPO.
1494 if (i <= tail->_rpo) {
1495
1496 // The tail and (recursive) predecessors of the tail
1497 // are made members of a new loop.
1498
1499 assert(worklist.size() == 0, "nonempty worklist");
1500 CFGLoop* nloop = new CFGLoop(idct++);
1501 assert(loop_head->_loop == NULL, "just checking");
1502 loop_head->_loop = nloop;
1503 // Add to nloop so push_pred() will skip over inner loops
1504 nloop->add_member(loop_head);
1505 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, _bbs);
1506
1507 while (worklist.size() > 0) {
1508 Block* member = worklist.pop();
1509 if (member != loop_head) {
1510 for (uint j = 1; j < member->num_preds(); j++) {
1511 nloop->push_pred(member, j, worklist, _bbs);
1512 }
1513 }
1514 }
1515 }
1516 }
1517 }
1518
1519 // Create a member list for each loop consisting
1520 // of both blocks and (immediate child) loops.
1521 for (uint i = 0; i < _num_blocks; i++) {
1522 Block *b = _blocks[i];
1523 CFGLoop* lp = b->_loop;
1524 if (lp == NULL) {
1525 // Not assigned to a loop. Add it to the method's pseudo loop.
1526 b->_loop = root_loop;
1527 lp = root_loop;
1528 }
1529 if (lp == root_loop || b != lp->head()) { // loop heads are already members
1530 lp->add_member(b);
1531 }
1532 if (lp != root_loop) {
1533 if (lp->parent() == NULL) {
1534 // Not a nested loop. Make it a child of the method's pseudo loop.
1535 root_loop->add_nested_loop(lp);
1536 }
1537 if (b == lp->head()) {
1538 // Add nested loop to member list of parent loop.
1539 lp->parent()->add_member(lp);
1540 }
1541 }
1542 }
1543
1544 return root_loop;
1545 }
1546
1547 //------------------------------push_pred--------------------------------------
1548 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk) {
1549 Node* pred_n = blk->pred(i);
1550 Block* pred = node_to_blk[pred_n->_idx];
1551 CFGLoop *pred_loop = pred->_loop;
1552 if (pred_loop == NULL) {
1553 // Filter out blocks for non-single-entry loops.
1554 // For all reasonable loops, the head occurs before the tail in RPO.
1555 if (pred->_rpo > head()->_rpo) {
1556 pred->_loop = this;
1557 worklist.push(pred);
1558 }
1559 } else if (pred_loop != this) {
1560 // Nested loop.
1561 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1562 pred_loop = pred_loop->_parent;
1563 }
1564 // Make pred's loop be a child
1565 if (pred_loop->_parent == NULL) {
1566 add_nested_loop(pred_loop);
1567 // Continue with loop entry predecessor.
1568 Block* pred_head = pred_loop->head();
1569 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1570 assert(pred_head != head(), "loop head in only one loop");
1571 push_pred(pred_head, LoopNode::EntryControl, worklist, node_to_blk);
1572 } else {
1573 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1574 }
1575 }
1576 }
1577
1578 //------------------------------add_nested_loop--------------------------------
1579 // Make cl a child of the current loop in the loop tree.
1580 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1581 assert(_parent == NULL, "no parent yet");
1582 assert(cl != this, "not my own parent");
1583 cl->_parent = this;
1584 CFGLoop* ch = _child;
1585 if (ch == NULL) {
1586 _child = cl;
1587 } else {
1588 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1589 ch->_sibling = cl;
1590 }
1591 }
1592
1593 //------------------------------compute_loop_depth-----------------------------
1594 // Store the loop depth in each CFGLoop object.
1595 // Recursively walk the children to do the same for them.
1596 void CFGLoop::compute_loop_depth(int depth) {
1597 _depth = depth;
1598 CFGLoop* ch = _child;
1599 while (ch != NULL) {
1600 ch->compute_loop_depth(depth + 1);
1601 ch = ch->_sibling;
1602 }
1603 }
1604
1605 //------------------------------compute_freq-----------------------------------
1606 // Compute the frequency of each block and loop, relative to a single entry
1607 // into the dominating loop head.
1608 void CFGLoop::compute_freq() {
1609 // Bottom up traversal of loop tree (visit inner loops first.)
1610 // Set loop head frequency to 1.0, then transitively
1611 // compute frequency for all successors in the loop,
1612 // as well as for each exit edge. Inner loops are
1613 // treated as single blocks with loop exit targets
1614 // as the successor blocks.
1615
1616 // Nested loops first
1617 CFGLoop* ch = _child;
1618 while (ch != NULL) {
1619 ch->compute_freq();
1620 ch = ch->_sibling;
1621 }
1622 assert (_members.length() > 0, "no empty loops");
1623 Block* hd = head();
1624 hd->_freq = 1.0f;
1625 for (int i = 0; i < _members.length(); i++) {
1626 CFGElement* s = _members.at(i);
1627 float freq = s->_freq;
1628 if (s->is_block()) {
1629 Block* b = s->as_Block();
1630 for (uint j = 0; j < b->_num_succs; j++) {
1631 Block* sb = b->_succs[j];
1632 update_succ_freq(sb, freq * b->succ_prob(j));
1633 }
1634 } else {
1635 CFGLoop* lp = s->as_CFGLoop();
1636 assert(lp->_parent == this, "immediate child");
1637 for (int k = 0; k < lp->_exits.length(); k++) {
1638 Block* eb = lp->_exits.at(k).get_target();
1639 float prob = lp->_exits.at(k).get_prob();
1640 update_succ_freq(eb, freq * prob);
1641 }
1642 }
1643 }
1644
1645 // For all loops other than the outer, "method" loop,
1646 // sum and normalize the exit probability. The "method" loop
1647 // should keep the initial exit probability of 1, so that
1648 // inner blocks do not get erroneously scaled.
1649 if (_depth != 0) {
1650 // Total the exit probabilities for this loop.
1651 float exits_sum = 0.0f;
1652 for (int i = 0; i < _exits.length(); i++) {
1653 exits_sum += _exits.at(i).get_prob();
1654 }
1655
1656 // Normalize the exit probabilities. Until now, the
1657 // probabilities estimate the possibility of exit per
1658 // a single loop iteration; afterward, they estimate
1659 // the probability of exit per loop entry.
1660 for (int i = 0; i < _exits.length(); i++) {
1661 Block* et = _exits.at(i).get_target();
1662 float new_prob = 0.0f;
1663 if (_exits.at(i).get_prob() > 0.0f) {
1664 new_prob = _exits.at(i).get_prob() / exits_sum;
1665 }
1666 BlockProbPair bpp(et, new_prob);
1667 _exits.at_put(i, bpp);
1668 }
1669
1670 // Save the total, but guard against unreasonable probability,
1671 // as the value is used to estimate the loop trip count.
1672 // An infinite trip count would blur relative block
1673 // frequencies.
1674 if (exits_sum > 1.0f) exits_sum = 1.0;
1675 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1676 _exit_prob = exits_sum;
1677 }
1678 }
1679
1680 //------------------------------succ_prob-------------------------------------
1681 // Determine the probability of reaching successor 'i' from the receiver block.
1682 float Block::succ_prob(uint i) {
1683 int eidx = end_idx();
1684 Node *n = _nodes[eidx]; // Get ending Node
1685
1686 int op = n->Opcode();
1687 if (n->is_Mach()) {
1688 if (n->is_MachNullCheck()) {
1689 // Can only reach here if called after lcm. The original Op_If is gone,
1690 // so we attempt to infer the probability from one or both of the
1691 // successor blocks.
1692 assert(_num_succs == 2, "expecting 2 successors of a null check");
1693 // If either successor has only one predecessor, then the
1694 // probability estimate can be derived using the
1695 // relative frequency of the successor and this block.
1696 if (_succs[i]->num_preds() == 2) {
1697 return _succs[i]->_freq / _freq;
1698 } else if (_succs[1-i]->num_preds() == 2) {
1699 return 1 - (_succs[1-i]->_freq / _freq);
1700 } else {
1701 // Estimate using both successor frequencies
1702 float freq = _succs[i]->_freq;
1703 return freq / (freq + _succs[1-i]->_freq);
1704 }
1705 }
1706 op = n->as_Mach()->ideal_Opcode();
1707 }
1708
1709
1710 // Switch on branch type
1711 switch( op ) {
1712 case Op_CountedLoopEnd:
1713 case Op_If: {
1714 assert (i < 2, "just checking");
1715 // Conditionals pass on only part of their frequency
1716 float prob = n->as_MachIf()->_prob;
1717 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1718 // If succ[i] is the FALSE branch, invert path info
1719 if( _nodes[i + eidx + 1]->Opcode() == Op_IfFalse ) {
1720 return 1.0f - prob; // not taken
1721 } else {
1722 return prob; // taken
1723 }
1724 }
1725
1726 case Op_Jump:
1727 // Divide the frequency between all successors evenly
1728 return 1.0f/_num_succs;
1729
1730 case Op_Catch: {
1731 const CatchProjNode *ci = _nodes[i + eidx + 1]->as_CatchProj();
1732 if (ci->_con == CatchProjNode::fall_through_index) {
1733 // Fall-thru path gets the lion's share.
1734 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1735 } else {
1736 // Presume exceptional paths are equally unlikely
1737 return PROB_UNLIKELY_MAG(5);
1738 }
1739 }
1740
1741 case Op_Root:
1742 case Op_Goto:
1743 // Pass frequency straight thru to target
1744 return 1.0f;
1745
1746 case Op_NeverBranch:
1747 return 0.0f;
1748
1749 case Op_TailCall:
1750 case Op_TailJump:
1751 case Op_Return:
1752 case Op_Halt:
1753 case Op_Rethrow:
1754 // Do not push out freq to root block
1755 return 0.0f;
1756
1757 default:
1758 ShouldNotReachHere();
1759 }
1760
1761 return 0.0f;
1762 }
1763
1764 //------------------------------num_fall_throughs-----------------------------
1765 // Return the number of fall-through candidates for a block
1766 int Block::num_fall_throughs() {
1767 int eidx = end_idx();
1768 Node *n = _nodes[eidx]; // Get ending Node
1769
1770 int op = n->Opcode();
1771 if (n->is_Mach()) {
1772 if (n->is_MachNullCheck()) {
1773 // In theory, either side can fall-thru, for simplicity sake,
1774 // let's say only the false branch can now.
1775 return 1;
1776 }
1777 op = n->as_Mach()->ideal_Opcode();
1778 }
1779
1780 // Switch on branch type
1781 switch( op ) {
1782 case Op_CountedLoopEnd:
1783 case Op_If:
1784 return 2;
1785
1786 case Op_Root:
1787 case Op_Goto:
1788 return 1;
1789
1790 case Op_Catch: {
1791 for (uint i = 0; i < _num_succs; i++) {
1792 const CatchProjNode *ci = _nodes[i + eidx + 1]->as_CatchProj();
1793 if (ci->_con == CatchProjNode::fall_through_index) {
1794 return 1;
1795 }
1796 }
1797 return 0;
1798 }
1799
1800 case Op_Jump:
1801 case Op_NeverBranch:
1802 case Op_TailCall:
1803 case Op_TailJump:
1804 case Op_Return:
1805 case Op_Halt:
1806 case Op_Rethrow:
1807 return 0;
1808
1809 default:
1810 ShouldNotReachHere();
1811 }
1812
1813 return 0;
1814 }
1815
1816 //------------------------------succ_fall_through-----------------------------
1817 // Return true if a specific successor could be fall-through target.
1818 bool Block::succ_fall_through(uint i) {
1819 int eidx = end_idx();
1820 Node *n = _nodes[eidx]; // Get ending Node
1821
1822 int op = n->Opcode();
1823 if (n->is_Mach()) {
1824 if (n->is_MachNullCheck()) {
1825 // In theory, either side can fall-thru, for simplicity sake,
1826 // let's say only the false branch can now.
1827 return _nodes[i + eidx + 1]->Opcode() == Op_IfFalse;
1828 }
1829 op = n->as_Mach()->ideal_Opcode();
1830 }
1831
1832 // Switch on branch type
1833 switch( op ) {
1834 case Op_CountedLoopEnd:
1835 case Op_If:
1836 case Op_Root:
1837 case Op_Goto:
1838 return true;
1839
1840 case Op_Catch: {
1841 const CatchProjNode *ci = _nodes[i + eidx + 1]->as_CatchProj();
1842 return ci->_con == CatchProjNode::fall_through_index;
1843 }
1844
1845 case Op_Jump:
1846 case Op_NeverBranch:
1847 case Op_TailCall:
1848 case Op_TailJump:
1849 case Op_Return:
1850 case Op_Halt:
1851 case Op_Rethrow:
1852 return false;
1853
1854 default:
1855 ShouldNotReachHere();
1856 }
1857
1858 return false;
1859 }
1860
1861 //------------------------------update_uncommon_branch------------------------
1862 // Update the probability of a two-branch to be uncommon
1863 void Block::update_uncommon_branch(Block* ub) {
1864 int eidx = end_idx();
1865 Node *n = _nodes[eidx]; // Get ending Node
1866
1867 int op = n->as_Mach()->ideal_Opcode();
1868
1869 assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If");
1870 assert(num_fall_throughs() == 2, "must be a two way branch block");
1871
1872 // Which successor is ub?
1873 uint s;
1874 for (s = 0; s <_num_succs; s++) {
1875 if (_succs[s] == ub) break;
1876 }
1877 assert(s < 2, "uncommon successor must be found");
1878
1879 // If ub is the true path, make the proability small, else
1880 // ub is the false path, and make the probability large
1881 bool invert = (_nodes[s + eidx + 1]->Opcode() == Op_IfFalse);
1882
1883 // Get existing probability
1884 float p = n->as_MachIf()->_prob;
1885
1886 if (invert) p = 1.0 - p;
1887 if (p > PROB_MIN) {
1888 p = PROB_MIN;
1889 }
1890 if (invert) p = 1.0 - p;
1891
1892 n->as_MachIf()->_prob = p;
1893 }
1894
1895 //------------------------------update_succ_freq-------------------------------
1896 // Update the appropriate frequency associated with block 'b', a successor of
1897 // a block in this loop.
1898 void CFGLoop::update_succ_freq(Block* b, float freq) {
1899 if (b->_loop == this) {
1900 if (b == head()) {
1901 // back branch within the loop
1902 // Do nothing now, the loop carried frequency will be
1903 // adjust later in scale_freq().
1904 } else {
1905 // simple branch within the loop
1906 b->_freq += freq;
1907 }
1908 } else if (!in_loop_nest(b)) {
1909 // branch is exit from this loop
1910 BlockProbPair bpp(b, freq);
1911 _exits.append(bpp);
1912 } else {
1913 // branch into nested loop
1914 CFGLoop* ch = b->_loop;
1915 ch->_freq += freq;
1916 }
1917 }
1918
1919 //------------------------------in_loop_nest-----------------------------------
1920 // Determine if block b is in the receiver's loop nest.
1921 bool CFGLoop::in_loop_nest(Block* b) {
1922 int depth = _depth;
1923 CFGLoop* b_loop = b->_loop;
1924 int b_depth = b_loop->_depth;
1925 if (depth == b_depth) {
1926 return true;
1927 }
1928 while (b_depth > depth) {
1929 b_loop = b_loop->_parent;
1930 b_depth = b_loop->_depth;
1931 }
1932 return b_loop == this;
1933 }
1934
1935 //------------------------------scale_freq-------------------------------------
1936 // Scale frequency of loops and blocks by trip counts from outer loops
1937 // Do a top down traversal of loop tree (visit outer loops first.)
1938 void CFGLoop::scale_freq() {
1939 float loop_freq = _freq * trip_count();
1940 _freq = loop_freq;
1941 for (int i = 0; i < _members.length(); i++) {
1942 CFGElement* s = _members.at(i);
1943 float block_freq = s->_freq * loop_freq;
1944 if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY)
1945 block_freq = MIN_BLOCK_FREQUENCY;
1946 s->_freq = block_freq;
1947 }
1948 CFGLoop* ch = _child;
1949 while (ch != NULL) {
1950 ch->scale_freq();
1951 ch = ch->_sibling;
1952 }
1953 }
1954
1955 // Frequency of outer loop
1956 float CFGLoop::outer_loop_freq() const {
1957 if (_child != NULL) {
1958 return _child->_freq;
1959 }
1960 return _freq;
1961 }
1962
1963 #ifndef PRODUCT
1964 //------------------------------dump_tree--------------------------------------
1965 void CFGLoop::dump_tree() const {
1966 dump();
1967 if (_child != NULL) _child->dump_tree();
1968 if (_sibling != NULL) _sibling->dump_tree();
1969 }
1970
1971 //------------------------------dump-------------------------------------------
1972 void CFGLoop::dump() const {
1973 for (int i = 0; i < _depth; i++) tty->print(" ");
1974 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
1975 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
1976 for (int i = 0; i < _depth; i++) tty->print(" ");
1977 tty->print(" members:", _id);
1978 int k = 0;
1979 for (int i = 0; i < _members.length(); i++) {
1980 if (k++ >= 6) {
1981 tty->print("\n ");
1982 for (int j = 0; j < _depth+1; j++) tty->print(" ");
1983 k = 0;
1984 }
1985 CFGElement *s = _members.at(i);
1986 if (s->is_block()) {
1987 Block *b = s->as_Block();
1988 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
1989 } else {
1990 CFGLoop* lp = s->as_CFGLoop();
1991 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
1992 }
1993 }
1994 tty->print("\n");
1995 for (int i = 0; i < _depth; i++) tty->print(" ");
1996 tty->print(" exits: ");
1997 k = 0;
1998 for (int i = 0; i < _exits.length(); i++) {
1999 if (k++ >= 7) {
2000 tty->print("\n ");
2001 for (int j = 0; j < _depth+1; j++) tty->print(" ");
2002 k = 0;
2003 }
2004 Block *blk = _exits.at(i).get_target();
2005 float prob = _exits.at(i).get_prob();
2006 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
2007 }
2008 tty->print("\n");
2009 }
2010 #endif