1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)gcm.cpp 1.259 08/07/10 14:40:09 JVM"
3 #endif
4 /*
5 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 // Portions of code courtesy of Clifford Click
29
30 // Optimization - Graph Style
31
32 #include "incls/_precompiled.incl"
33 #include "incls/_gcm.cpp.incl"
34
35 //----------------------------schedule_node_into_block-------------------------
36 // Insert node n into block b. Look for projections of n and make sure they
37 // are in b also.
38 void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
39 // Set basic block of n, Add n to b,
40 _bbs.map(n->_idx, b);
41 b->add_inst(n);
42
43 // After Matching, nearly any old Node may have projections trailing it.
44 // These are usually machine-dependent flags. In any case, they might
45 // float to another block below this one. Move them up.
46 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
47 Node* use = n->fast_out(i);
48 if (use->is_Proj()) {
49 Block* buse = _bbs[use->_idx];
50 if (buse != b) { // In wrong block?
51 if (buse != NULL)
52 buse->find_remove(use); // Remove from wrong block
53 _bbs.map(use->_idx, b); // Re-insert in this block
54 b->add_inst(use);
55 }
56 }
57 }
58 }
59
60
61 //------------------------------schedule_pinned_nodes--------------------------
62 // Set the basic block for Nodes pinned into blocks
63 void PhaseCFG::schedule_pinned_nodes( VectorSet &visited ) {
64 // Allocate node stack of size C->unique()+8 to avoid frequent realloc
65 GrowableArray <Node *> spstack(C->unique()+8);
66 spstack.push(_root);
67 while ( spstack.is_nonempty() ) {
68 Node *n = spstack.pop();
69 if( !visited.test_set(n->_idx) ) { // Test node and flag it as visited
70 if( n->pinned() && !_bbs.lookup(n->_idx) ) { // Pinned? Nail it down!
71 Node *input = n->in(0);
72 assert( input, "pinned Node must have Control" );
73 while( !input->is_block_start() )
74 input = input->in(0);
75 Block *b = _bbs[input->_idx]; // Basic block of controlling input
76 schedule_node_into_block(n, b);
77 }
78 for( int i = n->req() - 1; i >= 0; --i ) { // For all inputs
79 if( n->in(i) != NULL )
80 spstack.push(n->in(i));
81 }
82 }
83 }
84 }
85
86 #ifdef ASSERT
87 // Assert that new input b2 is dominated by all previous inputs.
88 // Check this by by seeing that it is dominated by b1, the deepest
89 // input observed until b2.
90 static void assert_dom(Block* b1, Block* b2, Node* n, Block_Array &bbs) {
91 if (b1 == NULL) return;
92 assert(b1->_dom_depth < b2->_dom_depth, "sanity");
93 Block* tmp = b2;
94 while (tmp != b1 && tmp != NULL) {
95 tmp = tmp->_idom;
96 }
97 if (tmp != b1) {
98 // Detected an unschedulable graph. Print some nice stuff and die.
99 tty->print_cr("!!! Unschedulable graph !!!");
100 for (uint j=0; j<n->len(); j++) { // For all inputs
101 Node* inn = n->in(j); // Get input
102 if (inn == NULL) continue; // Ignore NULL, missing inputs
103 Block* inb = bbs[inn->_idx];
104 tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order,
105 inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth);
106 inn->dump();
107 }
108 tty->print("Failing node: ");
109 n->dump();
110 assert(false, "unscheduable graph");
111 }
112 }
113 #endif
114
115 static Block* find_deepest_input(Node* n, Block_Array &bbs) {
116 // Find the last input dominated by all other inputs.
117 Block* deepb = NULL; // Deepest block so far
118 int deepb_dom_depth = 0;
119 for (uint k = 0; k < n->len(); k++) { // For all inputs
120 Node* inn = n->in(k); // Get input
121 if (inn == NULL) continue; // Ignore NULL, missing inputs
122 Block* inb = bbs[inn->_idx];
123 assert(inb != NULL, "must already have scheduled this input");
124 if (deepb_dom_depth < (int) inb->_dom_depth) {
125 // The new inb must be dominated by the previous deepb.
126 // The various inputs must be linearly ordered in the dom
127 // tree, or else there will not be a unique deepest block.
128 DEBUG_ONLY(assert_dom(deepb, inb, n, bbs));
129 deepb = inb; // Save deepest block
130 deepb_dom_depth = deepb->_dom_depth;
131 }
132 }
133 assert(deepb != NULL, "must be at least one input to n");
134 return deepb;
135 }
136
137
138 //------------------------------schedule_early---------------------------------
139 // Find the earliest Block any instruction can be placed in. Some instructions
140 // are pinned into Blocks. Unpinned instructions can appear in last block in
141 // which all their inputs occur.
142 bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) {
143 // Allocate stack with enough space to avoid frequent realloc
144 Node_Stack nstack(roots.Size() + 8); // (unique >> 1) + 24 from Java2D stats
145 // roots.push(_root); _root will be processed among C->top() inputs
146 roots.push(C->top());
147 visited.set(C->top()->_idx);
148
149 while (roots.size() != 0) {
150 // Use local variables nstack_top_n & nstack_top_i to cache values
151 // on stack's top.
152 Node *nstack_top_n = roots.pop();
153 uint nstack_top_i = 0;
154 //while_nstack_nonempty:
155 while (true) {
156 // Get parent node and next input's index from stack's top.
157 Node *n = nstack_top_n;
158 uint i = nstack_top_i;
159
160 if (i == 0) {
161 // Special control input processing.
162 // While I am here, go ahead and look for Nodes which are taking control
163 // from a is_block_proj Node. After I inserted RegionNodes to make proper
164 // blocks, the control at a is_block_proj more properly comes from the
165 // Region being controlled by the block_proj Node.
166 const Node *in0 = n->in(0);
167 if (in0 != NULL) { // Control-dependent?
168 const Node *p = in0->is_block_proj();
169 if (p != NULL && p != n) { // Control from a block projection?
170 // Find trailing Region
171 Block *pb = _bbs[in0->_idx]; // Block-projection already has basic block
172 uint j = 0;
173 if (pb->_num_succs != 1) { // More then 1 successor?
174 // Search for successor
175 uint max = pb->_nodes.size();
176 assert( max > 1, "" );
177 uint start = max - pb->_num_succs;
178 // Find which output path belongs to projection
179 for (j = start; j < max; j++) {
180 if( pb->_nodes[j] == in0 )
181 break;
182 }
183 assert( j < max, "must find" );
184 // Change control to match head of successor basic block
185 j -= start;
186 }
187 n->set_req(0, pb->_succs[j]->head());
188 }
189 } else { // n->in(0) == NULL
190 if (n->req() == 1) { // This guy is a constant with NO inputs?
191 n->set_req(0, _root);
192 }
193 }
194 }
195
196 // First, visit all inputs and force them to get a block. If an
197 // input is already in a block we quit following inputs (to avoid
198 // cycles). Instead we put that Node on a worklist to be handled
199 // later (since IT'S inputs may not have a block yet).
200 bool done = true; // Assume all n's inputs will be processed
201 while (i < n->len()) { // For all inputs
202 Node *in = n->in(i); // Get input
203 ++i;
204 if (in == NULL) continue; // Ignore NULL, missing inputs
205 int is_visited = visited.test_set(in->_idx);
206 if (!_bbs.lookup(in->_idx)) { // Missing block selection?
207 if (is_visited) {
208 // assert( !visited.test(in->_idx), "did not schedule early" );
209 return false;
210 }
211 nstack.push(n, i); // Save parent node and next input's index.
212 nstack_top_n = in; // Process current input now.
213 nstack_top_i = 0;
214 done = false; // Not all n's inputs processed.
215 break; // continue while_nstack_nonempty;
216 } else if (!is_visited) { // Input not yet visited?
217 roots.push(in); // Visit this guy later, using worklist
218 }
219 }
220 if (done) {
221 // All of n's inputs have been processed, complete post-processing.
222
223 // Some instructions are pinned into a block. These include Region,
224 // Phi, Start, Return, and other control-dependent instructions and
225 // any projections which depend on them.
226 if (!n->pinned()) {
227 // Set earliest legal block.
228 _bbs.map(n->_idx, find_deepest_input(n, _bbs));
229 }
230
231 if (nstack.is_empty()) {
232 // Finished all nodes on stack.
233 // Process next node on the worklist 'roots'.
234 break;
235 }
236 // Get saved parent node and next input's index.
237 nstack_top_n = nstack.node();
238 nstack_top_i = nstack.index();
239 nstack.pop();
240 } // if (done)
241 } // while (true)
242 } // while (roots.size() != 0)
243 return true;
244 }
245
246 //------------------------------dom_lca----------------------------------------
247 // Find least common ancestor in dominator tree
248 // LCA is a current notion of LCA, to be raised above 'this'.
249 // As a convenient boundary condition, return 'this' if LCA is NULL.
250 // Find the LCA of those two nodes.
251 Block* Block::dom_lca(Block* LCA) {
252 if (LCA == NULL || LCA == this) return this;
253
254 Block* anc = this;
255 while (anc->_dom_depth > LCA->_dom_depth)
256 anc = anc->_idom; // Walk up till anc is as high as LCA
257
258 while (LCA->_dom_depth > anc->_dom_depth)
259 LCA = LCA->_idom; // Walk up till LCA is as high as anc
260
261 while (LCA != anc) { // Walk both up till they are the same
262 LCA = LCA->_idom;
263 anc = anc->_idom;
264 }
265
266 return LCA;
267 }
268
269 //--------------------------raise_LCA_above_use--------------------------------
270 // We are placing a definition, and have been given a def->use edge.
271 // The definition must dominate the use, so move the LCA upward in the
272 // dominator tree to dominate the use. If the use is a phi, adjust
273 // the LCA only with the phi input paths which actually use this def.
274 static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, Block_Array &bbs) {
275 Block* buse = bbs[use->_idx];
276 if (buse == NULL) return LCA; // Unused killing Projs have no use block
277 if (!use->is_Phi()) return buse->dom_lca(LCA);
278 uint pmax = use->req(); // Number of Phi inputs
279 // Why does not this loop just break after finding the matching input to
280 // the Phi? Well...it's like this. I do not have true def-use/use-def
281 // chains. Means I cannot distinguish, from the def-use direction, which
282 // of many use-defs lead from the same use to the same def. That is, this
283 // Phi might have several uses of the same def. Each use appears in a
284 // different predecessor block. But when I enter here, I cannot distinguish
285 // which use-def edge I should find the predecessor block for. So I find
286 // them all. Means I do a little extra work if a Phi uses the same value
287 // more than once.
288 for (uint j=1; j<pmax; j++) { // For all inputs
289 if (use->in(j) == def) { // Found matching input?
290 Block* pred = bbs[buse->pred(j)->_idx];
291 LCA = pred->dom_lca(LCA);
292 }
293 }
294 return LCA;
295 }
296
297 //----------------------------raise_LCA_above_marks----------------------------
298 // Return a new LCA that dominates LCA and any of its marked predecessors.
299 // Search all my parents up to 'early' (exclusive), looking for predecessors
300 // which are marked with the given index. Return the LCA (in the dom tree)
301 // of all marked blocks. If there are none marked, return the original
302 // LCA.
303 static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark,
304 Block* early, Block_Array &bbs) {
305 Block_List worklist;
306 worklist.push(LCA);
307 while (worklist.size() > 0) {
308 Block* mid = worklist.pop();
309 if (mid == early) continue; // stop searching here
310
311 // Test and set the visited bit.
312 if (mid->raise_LCA_visited() == mark) continue; // already visited
313
314 // Don't process the current LCA, otherwise the search may terminate early
315 if (mid != LCA && mid->raise_LCA_mark() == mark) {
316 // Raise the LCA.
317 LCA = mid->dom_lca(LCA);
318 if (LCA == early) break; // stop searching everywhere
319 assert(early->dominates(LCA), "early is high enough");
320 // Resume searching at that point, skipping intermediate levels.
321 worklist.push(LCA);
322 if (LCA == mid)
323 continue; // Don't mark as visited to avoid early termination.
324 } else {
325 // Keep searching through this block's predecessors.
326 for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) {
327 Block* mid_parent = bbs[ mid->pred(j)->_idx ];
328 worklist.push(mid_parent);
329 }
330 }
331 mid->set_raise_LCA_visited(mark);
332 }
333 return LCA;
334 }
335
336 //--------------------------memory_early_block--------------------------------
337 // This is a variation of find_deepest_input, the heart of schedule_early.
338 // Find the "early" block for a load, if we considered only memory and
339 // address inputs, that is, if other data inputs were ignored.
340 //
341 // Because a subset of edges are considered, the resulting block will
342 // be earlier (at a shallower dom_depth) than the true schedule_early
343 // point of the node. We compute this earlier block as a more permissive
344 // site for anti-dependency insertion, but only if subsume_loads is enabled.
345 static Block* memory_early_block(Node* load, Block* early, Block_Array &bbs) {
346 Node* base;
347 Node* index;
348 Node* store = load->in(MemNode::Memory);
349 load->as_Mach()->memory_inputs(base, index);
350
351 assert(base != NodeSentinel && index != NodeSentinel,
352 "unexpected base/index inputs");
353
354 Node* mem_inputs[4];
355 int mem_inputs_length = 0;
356 if (base != NULL) mem_inputs[mem_inputs_length++] = base;
357 if (index != NULL) mem_inputs[mem_inputs_length++] = index;
358 if (store != NULL) mem_inputs[mem_inputs_length++] = store;
359
360 // In the comparision below, add one to account for the control input,
361 // which may be null, but always takes up a spot in the in array.
362 if (mem_inputs_length + 1 < (int) load->req()) {
363 // This "load" has more inputs than just the memory, base and index inputs.
364 // For purposes of checking anti-dependences, we need to start
365 // from the early block of only the address portion of the instruction,
366 // and ignore other blocks that may have factored into the wider
367 // schedule_early calculation.
368 if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0);
369
370 Block* deepb = NULL; // Deepest block so far
371 int deepb_dom_depth = 0;
372 for (int i = 0; i < mem_inputs_length; i++) {
373 Block* inb = bbs[mem_inputs[i]->_idx];
374 if (deepb_dom_depth < (int) inb->_dom_depth) {
375 // The new inb must be dominated by the previous deepb.
376 // The various inputs must be linearly ordered in the dom
377 // tree, or else there will not be a unique deepest block.
378 DEBUG_ONLY(assert_dom(deepb, inb, load, bbs));
379 deepb = inb; // Save deepest block
380 deepb_dom_depth = deepb->_dom_depth;
381 }
382 }
383 early = deepb;
384 }
385
386 return early;
387 }
388
389 //--------------------------insert_anti_dependences---------------------------
390 // A load may need to witness memory that nearby stores can overwrite.
391 // For each nearby store, either insert an "anti-dependence" edge
392 // from the load to the store, or else move LCA upward to force the
393 // load to (eventually) be scheduled in a block above the store.
394 //
395 // Do not add edges to stores on distinct control-flow paths;
396 // only add edges to stores which might interfere.
397 //
398 // Return the (updated) LCA. There will not be any possibly interfering
399 // store between the load's "early block" and the updated LCA.
400 // Any stores in the updated LCA will have new precedence edges
401 // back to the load. The caller is expected to schedule the load
402 // in the LCA, in which case the precedence edges will make LCM
403 // preserve anti-dependences. The caller may also hoist the load
404 // above the LCA, if it is not the early block.
405 Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) {
406 assert(load->needs_anti_dependence_check(), "must be a load of some sort");
407 assert(LCA != NULL, "");
408 DEBUG_ONLY(Block* LCA_orig = LCA);
409
410 // Compute the alias index. Loads and stores with different alias indices
411 // do not need anti-dependence edges.
412 uint load_alias_idx = C->get_alias_index(load->adr_type());
413 #ifdef ASSERT
414 if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 &&
415 (PrintOpto || VerifyAliases ||
416 PrintMiscellaneous && (WizardMode || Verbose))) {
417 // Load nodes should not consume all of memory.
418 // Reporting a bottom type indicates a bug in adlc.
419 // If some particular type of node validly consumes all of memory,
420 // sharpen the preceding "if" to exclude it, so we can catch bugs here.
421 tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory.");
422 load->dump(2);
423 if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, "");
424 }
425 #endif
426 assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp),
427 "String compare is only known 'load' that does not conflict with any stores");
428
429 if (!C->alias_type(load_alias_idx)->is_rewritable()) {
430 // It is impossible to spoil this load by putting stores before it,
431 // because we know that the stores will never update the value
432 // which 'load' must witness.
433 return LCA;
434 }
435
436 node_idx_t load_index = load->_idx;
437
438 // Note the earliest legal placement of 'load', as determined by
439 // by the unique point in the dom tree where all memory effects
440 // and other inputs are first available. (Computed by schedule_early.)
441 // For normal loads, 'early' is the shallowest place (dom graph wise)
442 // to look for anti-deps between this load and any store.
443 Block* early = _bbs[load_index];
444
445 // If we are subsuming loads, compute an "early" block that only considers
446 // memory or address inputs. This block may be different than the
447 // schedule_early block in that it could be at an even shallower depth in the
448 // dominator tree, and allow for a broader discovery of anti-dependences.
449 if (C->subsume_loads()) {
450 early = memory_early_block(load, early, _bbs);
451 }
452
453 ResourceArea *area = Thread::current()->resource_area();
454 Node_List worklist_mem(area); // prior memory state to store
455 Node_List worklist_store(area); // possible-def to explore
456 Node_List non_early_stores(area); // all relevant stores outside of early
457 bool must_raise_LCA = false;
458 DEBUG_ONLY(VectorSet should_not_repeat(area));
459
460 #ifdef TRACK_PHI_INPUTS
461 // %%% This extra checking fails because MergeMem nodes are not GVNed.
462 // Provide "phi_inputs" to check if every input to a PhiNode is from the
463 // original memory state. This indicates a PhiNode for which should not
464 // prevent the load from sinking. For such a block, set_raise_LCA_mark
465 // may be overly conservative.
466 // Mechanism: count inputs seen for each Phi encountered in worklist_store.
467 DEBUG_ONLY(GrowableArray<uint> phi_inputs(area, C->unique(),0,0));
468 #endif
469
470 // 'load' uses some memory state; look for users of the same state.
471 // Recurse through MergeMem nodes to the stores that use them.
472
473 // Each of these stores is a possible definition of memory
474 // that 'load' needs to use. We need to force 'load'
475 // to occur before each such store. When the store is in
476 // the same block as 'load', we insert an anti-dependence
477 // edge load->store.
478
479 // The relevant stores "nearby" the load consist of a tree rooted
480 // at initial_mem, with internal nodes of type MergeMem.
481 // Therefore, the branches visited by the worklist are of this form:
482 // initial_mem -> (MergeMem ->)* store
483 // The anti-dependence constraints apply only to the fringe of this tree.
484
485 Node* initial_mem = load->in(MemNode::Memory);
486 worklist_store.push(initial_mem);
487 worklist_mem.push(NULL);
488 DEBUG_ONLY(should_not_repeat.test_set(initial_mem->_idx));
489 while (worklist_store.size() > 0) {
490 // Examine a nearby store to see if it might interfere with our load.
491 Node* mem = worklist_mem.pop();
492 Node* store = worklist_store.pop();
493 uint op = store->Opcode();
494
495 // MergeMems do not directly have anti-deps.
496 // Treat them as internal nodes in a forward tree of memory states,
497 // the leaves of which are each a 'possible-def'.
498 if (store == initial_mem // root (exclusive) of tree we are searching
499 || op == Op_MergeMem // internal node of tree we are searching
500 ) {
501 mem = store; // It's not a possibly interfering store.
502 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
503 store = mem->fast_out(i);
504 if (store->is_MergeMem()) {
505 // Be sure we don't get into combinatorial problems.
506 // (Allow phis to be repeated; they can merge two relevant states.)
507 uint i = worklist_store.size();
508 for (; i > 0; i--) {
509 if (worklist_store.at(i-1) == store) break;
510 }
511 if (i > 0) continue; // already on work list; do not repeat
512 DEBUG_ONLY(int repeated = should_not_repeat.test_set(store->_idx));
513 assert(!repeated, "do not walk merges twice");
514 }
515 worklist_mem.push(mem);
516 worklist_store.push(store);
517 }
518 continue;
519 }
520
521 if (op == Op_MachProj || op == Op_Catch) continue;
522 if (store->needs_anti_dependence_check()) continue; // not really a store
523
524 // Compute the alias index. Loads and stores with different alias
525 // indices do not need anti-dependence edges. Wide MemBar's are
526 // anti-dependent on everything (except immutable memories).
527 const TypePtr* adr_type = store->adr_type();
528 if (!C->can_alias(adr_type, load_alias_idx)) continue;
529
530 // Most slow-path runtime calls do NOT modify Java memory, but
531 // they can block and so write Raw memory.
532 if (store->is_Mach()) {
533 MachNode* mstore = store->as_Mach();
534 if (load_alias_idx != Compile::AliasIdxRaw) {
535 // Check for call into the runtime using the Java calling
536 // convention (and from there into a wrapper); it has no
537 // _method. Can't do this optimization for Native calls because
538 // they CAN write to Java memory.
539 if (mstore->ideal_Opcode() == Op_CallStaticJava) {
540 assert(mstore->is_MachSafePoint(), "");
541 MachSafePointNode* ms = (MachSafePointNode*) mstore;
542 assert(ms->is_MachCallJava(), "");
543 MachCallJavaNode* mcj = (MachCallJavaNode*) ms;
544 if (mcj->_method == NULL) {
545 // These runtime calls do not write to Java visible memory
546 // (other than Raw) and so do not require anti-dependence edges.
547 continue;
548 }
549 }
550 // Same for SafePoints: they read/write Raw but only read otherwise.
551 // This is basically a workaround for SafePoints only defining control
552 // instead of control + memory.
553 if (mstore->ideal_Opcode() == Op_SafePoint)
554 continue;
555 } else {
556 // Some raw memory, such as the load of "top" at an allocation,
557 // can be control dependent on the previous safepoint. See
558 // comments in GraphKit::allocate_heap() about control input.
559 // Inserting an anti-dep between such a safepoint and a use
560 // creates a cycle, and will cause a subsequent failure in
561 // local scheduling. (BugId 4919904)
562 // (%%% How can a control input be a safepoint and not a projection??)
563 if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore)
564 continue;
565 }
566 }
567
568 // Identify a block that the current load must be above,
569 // or else observe that 'store' is all the way up in the
570 // earliest legal block for 'load'. In the latter case,
571 // immediately insert an anti-dependence edge.
572 Block* store_block = _bbs[store->_idx];
573 assert(store_block != NULL, "unused killing projections skipped above");
574
575 if (store->is_Phi()) {
576 // 'load' uses memory which is one (or more) of the Phi's inputs.
577 // It must be scheduled not before the Phi, but rather before
578 // each of the relevant Phi inputs.
579 //
580 // Instead of finding the LCA of all inputs to a Phi that match 'mem',
581 // we mark each corresponding predecessor block and do a combined
582 // hoisting operation later (raise_LCA_above_marks).
583 //
584 // Do not assert(store_block != early, "Phi merging memory after access")
585 // PhiNode may be at start of block 'early' with backedge to 'early'
586 DEBUG_ONLY(bool found_match = false);
587 for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) {
588 if (store->in(j) == mem) { // Found matching input?
589 DEBUG_ONLY(found_match = true);
590 Block* pred_block = _bbs[store_block->pred(j)->_idx];
591 if (pred_block != early) {
592 // If any predecessor of the Phi matches the load's "early block",
593 // we do not need a precedence edge between the Phi and 'load'
594 // since the load will be forced into a block preceeding the Phi.
595 pred_block->set_raise_LCA_mark(load_index);
596 assert(!LCA_orig->dominates(pred_block) ||
597 early->dominates(pred_block), "early is high enough");
598 must_raise_LCA = true;
599 }
600 }
601 }
602 assert(found_match, "no worklist bug");
603 #ifdef TRACK_PHI_INPUTS
604 #ifdef ASSERT
605 // This assert asks about correct handling of PhiNodes, which may not
606 // have all input edges directly from 'mem'. See BugId 4621264
607 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1;
608 // Increment by exactly one even if there are multiple copies of 'mem'
609 // coming into the phi, because we will run this block several times
610 // if there are several copies of 'mem'. (That's how DU iterators work.)
611 phi_inputs.at_put(store->_idx, num_mem_inputs);
612 assert(PhiNode::Input + num_mem_inputs < store->req(),
613 "Expect at least one phi input will not be from original memory state");
614 #endif //ASSERT
615 #endif //TRACK_PHI_INPUTS
616 } else if (store_block != early) {
617 // 'store' is between the current LCA and earliest possible block.
618 // Label its block, and decide later on how to raise the LCA
619 // to include the effect on LCA of this store.
620 // If this store's block gets chosen as the raised LCA, we
621 // will find him on the non_early_stores list and stick him
622 // with a precedence edge.
623 // (But, don't bother if LCA is already raised all the way.)
624 if (LCA != early) {
625 store_block->set_raise_LCA_mark(load_index);
626 must_raise_LCA = true;
627 non_early_stores.push(store);
628 }
629 } else {
630 // Found a possibly-interfering store in the load's 'early' block.
631 // This means 'load' cannot sink at all in the dominator tree.
632 // Add an anti-dep edge, and squeeze 'load' into the highest block.
633 assert(store != load->in(0), "dependence cycle found");
634 if (verify) {
635 assert(store->find_edge(load) != -1, "missing precedence edge");
636 } else {
637 store->add_prec(load);
638 }
639 LCA = early;
640 // This turns off the process of gathering non_early_stores.
641 }
642 }
643 // (Worklist is now empty; all nearby stores have been visited.)
644
645 // Finished if 'load' must be scheduled in its 'early' block.
646 // If we found any stores there, they have already been given
647 // precedence edges.
648 if (LCA == early) return LCA;
649
650 // We get here only if there are no possibly-interfering stores
651 // in the load's 'early' block. Move LCA up above all predecessors
652 // which contain stores we have noted.
653 //
654 // The raised LCA block can be a home to such interfering stores,
655 // but its predecessors must not contain any such stores.
656 //
657 // The raised LCA will be a lower bound for placing the load,
658 // preventing the load from sinking past any block containing
659 // a store that may invalidate the memory state required by 'load'.
660 if (must_raise_LCA)
661 LCA = raise_LCA_above_marks(LCA, load->_idx, early, _bbs);
662 if (LCA == early) return LCA;
663
664 // Insert anti-dependence edges from 'load' to each store
665 // in the non-early LCA block.
666 // Mine the non_early_stores list for such stores.
667 if (LCA->raise_LCA_mark() == load_index) {
668 while (non_early_stores.size() > 0) {
669 Node* store = non_early_stores.pop();
670 Block* store_block = _bbs[store->_idx];
671 if (store_block == LCA) {
672 // add anti_dependence from store to load in its own block
673 assert(store != load->in(0), "dependence cycle found");
674 if (verify) {
675 assert(store->find_edge(load) != -1, "missing precedence edge");
676 } else {
677 store->add_prec(load);
678 }
679 } else {
680 assert(store_block->raise_LCA_mark() == load_index, "block was marked");
681 // Any other stores we found must be either inside the new LCA
682 // or else outside the original LCA. In the latter case, they
683 // did not interfere with any use of 'load'.
684 assert(LCA->dominates(store_block)
685 || !LCA_orig->dominates(store_block), "no stray stores");
686 }
687 }
688 }
689
690 // Return the highest block containing stores; any stores
691 // within that block have been given anti-dependence edges.
692 return LCA;
693 }
694
695 // This class is used to iterate backwards over the nodes in the graph.
696
697 class Node_Backward_Iterator {
698
699 private:
700 Node_Backward_Iterator();
701
702 public:
703 // Constructor for the iterator
704 Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs);
705
706 // Postincrement operator to iterate over the nodes
707 Node *next();
708
709 private:
710 VectorSet &_visited;
711 Node_List &_stack;
712 Block_Array &_bbs;
713 };
714
715 // Constructor for the Node_Backward_Iterator
716 Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, Block_Array &bbs )
717 : _visited(visited), _stack(stack), _bbs(bbs) {
718 // The stack should contain exactly the root
719 stack.clear();
720 stack.push(root);
721
722 // Clear the visited bits
723 visited.Clear();
724 }
725
726 // Iterator for the Node_Backward_Iterator
727 Node *Node_Backward_Iterator::next() {
728
729 // If the _stack is empty, then just return NULL: finished.
730 if ( !_stack.size() )
731 return NULL;
732
733 // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been
734 // made stateless, so I do not need to record the index 'i' on my _stack.
735 // Instead I visit all users each time, scanning for unvisited users.
736 // I visit unvisited not-anti-dependence users first, then anti-dependent
737 // children next.
738 Node *self = _stack.pop();
739
740 // I cycle here when I am entering a deeper level of recursion.
741 // The key variable 'self' was set prior to jumping here.
742 while( 1 ) {
743
744 _visited.set(self->_idx);
745
746 // Now schedule all uses as late as possible.
747 uint src = self->is_Proj() ? self->in(0)->_idx : self->_idx;
748 uint src_rpo = _bbs[src]->_rpo;
749
750 // Schedule all nodes in a post-order visit
751 Node *unvisited = NULL; // Unvisited anti-dependent Node, if any
752
753 // Scan for unvisited nodes
754 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
755 // For all uses, schedule late
756 Node* n = self->fast_out(i); // Use
757
758 // Skip already visited children
759 if ( _visited.test(n->_idx) )
760 continue;
761
762 // do not traverse backward control edges
763 Node *use = n->is_Proj() ? n->in(0) : n;
764 uint use_rpo = _bbs[use->_idx]->_rpo;
765
766 if ( use_rpo < src_rpo )
767 continue;
768
769 // Phi nodes always precede uses in a basic block
770 if ( use_rpo == src_rpo && use->is_Phi() )
771 continue;
772
773 unvisited = n; // Found unvisited
774
775 // Check for possible-anti-dependent
776 if( !n->needs_anti_dependence_check() )
777 break; // Not visited, not anti-dep; schedule it NOW
778 }
779
780 // Did I find an unvisited not-anti-dependent Node?
781 if ( !unvisited )
782 break; // All done with children; post-visit 'self'
783
784 // Visit the unvisited Node. Contains the obvious push to
785 // indicate I'm entering a deeper level of recursion. I push the
786 // old state onto the _stack and set a new state and loop (recurse).
787 _stack.push(self);
788 self = unvisited;
789 } // End recursion loop
790
791 return self;
792 }
793
794 //------------------------------ComputeLatenciesBackwards----------------------
795 // Compute the latency of all the instructions.
796 void PhaseCFG::ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack) {
797 #ifndef PRODUCT
798 if (trace_opto_pipelining())
799 tty->print("\n#---- ComputeLatenciesBackwards ----\n");
800 #endif
801
802 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs);
803 Node *n;
804
805 // Walk over all the nodes from last to first
806 while (n = iter.next()) {
807 // Set the latency for the definitions of this instruction
808 partial_latency_of_defs(n);
809 }
810 } // end ComputeLatenciesBackwards
811
812 //------------------------------partial_latency_of_defs------------------------
813 // Compute the latency impact of this node on all defs. This computes
814 // a number that increases as we approach the beginning of the routine.
815 void PhaseCFG::partial_latency_of_defs(Node *n) {
816 // Set the latency for this instruction
817 #ifndef PRODUCT
818 if (trace_opto_pipelining()) {
819 tty->print("# latency_to_inputs: node_latency[%d] = %d for node",
820 n->_idx, _node_latency.at_grow(n->_idx));
821 dump();
822 }
823 #endif
824
825 if (n->is_Proj())
826 n = n->in(0);
827
828 if (n->is_Root())
829 return;
830
831 uint nlen = n->len();
832 uint use_latency = _node_latency.at_grow(n->_idx);
833 uint use_pre_order = _bbs[n->_idx]->_pre_order;
834
835 for ( uint j=0; j<nlen; j++ ) {
836 Node *def = n->in(j);
837
838 if (!def || def == n)
839 continue;
840
841 // Walk backwards thru projections
842 if (def->is_Proj())
843 def = def->in(0);
844
845 #ifndef PRODUCT
846 if (trace_opto_pipelining()) {
847 tty->print("# in(%2d): ", j);
848 def->dump();
849 }
850 #endif
851
852 // If the defining block is not known, assume it is ok
853 Block *def_block = _bbs[def->_idx];
854 uint def_pre_order = def_block ? def_block->_pre_order : 0;
855
856 if ( (use_pre_order < def_pre_order) ||
857 (use_pre_order == def_pre_order && n->is_Phi()) )
858 continue;
859
860 uint delta_latency = n->latency(j);
861 uint current_latency = delta_latency + use_latency;
862
863 if (_node_latency.at_grow(def->_idx) < current_latency) {
864 _node_latency.at_put_grow(def->_idx, current_latency);
865 }
866
867 #ifndef PRODUCT
868 if (trace_opto_pipelining()) {
869 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, node_latency[%d] = %d",
870 use_latency, j, delta_latency, current_latency, def->_idx,
871 _node_latency.at_grow(def->_idx));
872 }
873 #endif
874 }
875 }
876
877 //------------------------------latency_from_use-------------------------------
878 // Compute the latency of a specific use
879 int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) {
880 // If self-reference, return no latency
881 if (use == n || use->is_Root())
882 return 0;
883
884 uint def_pre_order = _bbs[def->_idx]->_pre_order;
885 uint latency = 0;
886
887 // If the use is not a projection, then it is simple...
888 if (!use->is_Proj()) {
889 #ifndef PRODUCT
890 if (trace_opto_pipelining()) {
891 tty->print("# out(): ");
892 use->dump();
893 }
894 #endif
895
896 uint use_pre_order = _bbs[use->_idx]->_pre_order;
897
898 if (use_pre_order < def_pre_order)
899 return 0;
900
901 if (use_pre_order == def_pre_order && use->is_Phi())
902 return 0;
903
904 uint nlen = use->len();
905 uint nl = _node_latency.at_grow(use->_idx);
906
907 for ( uint j=0; j<nlen; j++ ) {
908 if (use->in(j) == n) {
909 // Change this if we want local latencies
910 uint ul = use->latency(j);
911 uint l = ul + nl;
912 if (latency < l) latency = l;
913 #ifndef PRODUCT
914 if (trace_opto_pipelining()) {
915 tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d",
916 nl, j, ul, l, latency);
917 }
918 #endif
919 }
920 }
921 } else {
922 // This is a projection, just grab the latency of the use(s)
923 for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) {
924 uint l = latency_from_use(use, def, use->fast_out(j));
925 if (latency < l) latency = l;
926 }
927 }
928
929 return latency;
930 }
931
932 //------------------------------latency_from_uses------------------------------
933 // Compute the latency of this instruction relative to all of it's uses.
934 // This computes a number that increases as we approach the beginning of the
935 // routine.
936 void PhaseCFG::latency_from_uses(Node *n) {
937 // Set the latency for this instruction
938 #ifndef PRODUCT
939 if (trace_opto_pipelining()) {
940 tty->print("# latency_from_outputs: node_latency[%d] = %d for node",
941 n->_idx, _node_latency.at_grow(n->_idx));
942 dump();
943 }
944 #endif
945 uint latency=0;
946 const Node *def = n->is_Proj() ? n->in(0): n;
947
948 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
949 uint l = latency_from_use(n, def, n->fast_out(i));
950
951 if (latency < l) latency = l;
952 }
953
954 _node_latency.at_put_grow(n->_idx, latency);
955 }
956
957 //------------------------------hoist_to_cheaper_block-------------------------
958 // Pick a block for node self, between early and LCA, that is a cheaper
959 // alternative to LCA.
960 Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
961 const double delta = 1+PROB_UNLIKELY_MAG(4);
962 Block* least = LCA;
963 double least_freq = least->_freq;
964 uint target = _node_latency.at_grow(self->_idx);
965 uint start_latency = _node_latency.at_grow(LCA->_nodes[0]->_idx);
966 uint end_latency = _node_latency.at_grow(LCA->_nodes[LCA->end_idx()]->_idx);
967 bool in_latency = (target <= start_latency);
968 const Block* root_block = _bbs[_root->_idx];
969
970 // Turn off latency scheduling if scheduling is just plain off
971 if (!C->do_scheduling())
972 in_latency = true;
973
974 // Do not hoist (to cover latency) instructions which target a
975 // single register. Hoisting stretches the live range of the
976 // single register and may force spilling.
977 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
978 if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty())
979 in_latency = true;
980
981 #ifndef PRODUCT
982 if (trace_opto_pipelining()) {
983 tty->print("# Find cheaper block for latency %d: ",
984 _node_latency.at_grow(self->_idx));
985 self->dump();
986 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
987 LCA->_pre_order,
988 LCA->_nodes[0]->_idx,
989 start_latency,
990 LCA->_nodes[LCA->end_idx()]->_idx,
991 end_latency,
992 least_freq);
993 }
994 #endif
995
996 // Walk up the dominator tree from LCA (Lowest common ancestor) to
997 // the earliest legal location. Capture the least execution frequency.
998 while (LCA != early) {
999 LCA = LCA->_idom; // Follow up the dominator tree
1000
1001 if (LCA == NULL) {
1002 // Bailout without retry
1003 C->record_method_not_compilable("late schedule failed: LCA == NULL");
1004 return least;
1005 }
1006
1007 // Don't hoist machine instructions to the root basic block
1008 if (mach && LCA == root_block)
1009 break;
1010
1011 uint start_lat = _node_latency.at_grow(LCA->_nodes[0]->_idx);
1012 uint end_idx = LCA->end_idx();
1013 uint end_lat = _node_latency.at_grow(LCA->_nodes[end_idx]->_idx);
1014 double LCA_freq = LCA->_freq;
1015 #ifndef PRODUCT
1016 if (trace_opto_pipelining()) {
1017 tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g",
1018 LCA->_pre_order, LCA->_nodes[0]->_idx, start_lat, end_idx, end_lat, LCA_freq);
1019 }
1020 #endif
1021 if (LCA_freq < least_freq || // Better Frequency
1022 ( !in_latency && // No block containing latency
1023 LCA_freq < least_freq * delta && // No worse frequency
1024 target >= end_lat && // within latency range
1025 !self->is_iteratively_computed() ) // But don't hoist IV increments
1026 // because they may end up above other uses of their phi forcing
1027 // their result register to be different from their input.
1028 ) {
1029 least = LCA; // Found cheaper block
1030 least_freq = LCA_freq;
1031 start_latency = start_lat;
1032 end_latency = end_lat;
1033 if (target <= start_lat)
1034 in_latency = true;
1035 }
1036 }
1037
1038 #ifndef PRODUCT
1039 if (trace_opto_pipelining()) {
1040 tty->print_cr("# Choose block B%d with start latency=%d and freq=%g",
1041 least->_pre_order, start_latency, least_freq);
1042 }
1043 #endif
1044
1045 // See if the latency needs to be updated
1046 if (target < end_latency) {
1047 #ifndef PRODUCT
1048 if (trace_opto_pipelining()) {
1049 tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency);
1050 }
1051 #endif
1052 _node_latency.at_put_grow(self->_idx, end_latency);
1053 partial_latency_of_defs(self);
1054 }
1055
1056 return least;
1057 }
1058
1059
1060 //------------------------------schedule_late-----------------------------------
1061 // Now schedule all codes as LATE as possible. This is the LCA in the
1062 // dominator tree of all USES of a value. Pick the block with the least
1063 // loop nesting depth that is lowest in the dominator tree.
1064 extern const char must_clone[];
1065 void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) {
1066 #ifndef PRODUCT
1067 if (trace_opto_pipelining())
1068 tty->print("\n#---- schedule_late ----\n");
1069 #endif
1070
1071 Node_Backward_Iterator iter((Node *)_root, visited, stack, _bbs);
1072 Node *self;
1073
1074 // Walk over all the nodes from last to first
1075 while (self = iter.next()) {
1076 Block* early = _bbs[self->_idx]; // Earliest legal placement
1077
1078 if (self->is_top()) {
1079 // Top node goes in bb #2 with other constants.
1080 // It must be special-cased, because it has no out edges.
1081 early->add_inst(self);
1082 continue;
1083 }
1084
1085 // No uses, just terminate
1086 if (self->outcnt() == 0) {
1087 assert(self->Opcode() == Op_MachProj, "sanity");
1088 continue; // Must be a dead machine projection
1089 }
1090
1091 // If node is pinned in the block, then no scheduling can be done.
1092 if( self->pinned() ) // Pinned in block?
1093 continue;
1094
1095 MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL;
1096 if (mach) {
1097 switch (mach->ideal_Opcode()) {
1098 case Op_CreateEx:
1099 // Don't move exception creation
1100 early->add_inst(self);
1101 continue;
1102 break;
1103 case Op_CheckCastPP:
1104 // Don't move CheckCastPP nodes away from their input, if the input
1105 // is a rawptr (5071820).
1106 Node *def = self->in(1);
1107 if (def != NULL && def->bottom_type()->base() == Type::RawPtr) {
1108 early->add_inst(self);
1109 continue;
1110 }
1111 break;
1112 }
1113 }
1114
1115 // Gather LCA of all uses
1116 Block *LCA = NULL;
1117 {
1118 for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) {
1119 // For all uses, find LCA
1120 Node* use = self->fast_out(i);
1121 LCA = raise_LCA_above_use(LCA, use, self, _bbs);
1122 }
1123 } // (Hide defs of imax, i from rest of block.)
1124
1125 // Place temps in the block of their use. This isn't a
1126 // requirement for correctness but it reduces useless
1127 // interference between temps and other nodes.
1128 if (mach != NULL && mach->is_MachTemp()) {
1129 _bbs.map(self->_idx, LCA);
1130 LCA->add_inst(self);
1131 continue;
1132 }
1133
1134 // Check if 'self' could be anti-dependent on memory
1135 if (self->needs_anti_dependence_check()) {
1136 // Hoist LCA above possible-defs and insert anti-dependences to
1137 // defs in new LCA block.
1138 LCA = insert_anti_dependences(LCA, self);
1139 }
1140
1141 if (early->_dom_depth > LCA->_dom_depth) {
1142 // Somehow the LCA has moved above the earliest legal point.
1143 // (One way this can happen is via memory_early_block.)
1144 if (C->subsume_loads() == true && !C->failing()) {
1145 // Retry with subsume_loads == false
1146 // If this is the first failure, the sentinel string will "stick"
1147 // to the Compile object, and the C2Compiler will see it and retry.
1148 C->record_failure(C2Compiler::retry_no_subsuming_loads());
1149 } else {
1150 // Bailout without retry when (early->_dom_depth > LCA->_dom_depth)
1151 C->record_method_not_compilable("late schedule failed: incorrect graph");
1152 }
1153 return;
1154 }
1155
1156 // If there is no opportunity to hoist, then we're done.
1157 bool try_to_hoist = (LCA != early);
1158
1159 // Must clone guys stay next to use; no hoisting allowed.
1160 // Also cannot hoist guys that alter memory or are otherwise not
1161 // allocatable (hoisting can make a value live longer, leading to
1162 // anti and output dependency problems which are normally resolved
1163 // by the register allocator giving everyone a different register).
1164 if (mach != NULL && must_clone[mach->ideal_Opcode()])
1165 try_to_hoist = false;
1166
1167 Block* late = NULL;
1168 if (try_to_hoist) {
1169 // Now find the block with the least execution frequency.
1170 // Start at the latest schedule and work up to the earliest schedule
1171 // in the dominator tree. Thus the Node will dominate all its uses.
1172 late = hoist_to_cheaper_block(LCA, early, self);
1173 } else {
1174 // Just use the LCA of the uses.
1175 late = LCA;
1176 }
1177
1178 // Put the node into target block
1179 schedule_node_into_block(self, late);
1180
1181 #ifdef ASSERT
1182 if (self->needs_anti_dependence_check()) {
1183 // since precedence edges are only inserted when we're sure they
1184 // are needed make sure that after placement in a block we don't
1185 // need any new precedence edges.
1186 verify_anti_dependences(late, self);
1187 }
1188 #endif
1189 } // Loop until all nodes have been visited
1190
1191 } // end ScheduleLate
1192
1193 //------------------------------GlobalCodeMotion-------------------------------
1194 void PhaseCFG::GlobalCodeMotion( Matcher &matcher, uint unique, Node_List &proj_list ) {
1195 ResourceMark rm;
1196
1197 #ifndef PRODUCT
1198 if (trace_opto_pipelining()) {
1199 tty->print("\n---- Start GlobalCodeMotion ----\n");
1200 }
1201 #endif
1202
1203 // Initialize the bbs.map for things on the proj_list
1204 uint i;
1205 for( i=0; i < proj_list.size(); i++ )
1206 _bbs.map(proj_list[i]->_idx, NULL);
1207
1208 // Set the basic block for Nodes pinned into blocks
1209 Arena *a = Thread::current()->resource_area();
1210 VectorSet visited(a);
1211 schedule_pinned_nodes( visited );
1212
1213 // Find the earliest Block any instruction can be placed in. Some
1214 // instructions are pinned into Blocks. Unpinned instructions can
1215 // appear in last block in which all their inputs occur.
1216 visited.Clear();
1217 Node_List stack(a);
1218 stack.map( (unique >> 1) + 16, NULL); // Pre-grow the list
1219 if (!schedule_early(visited, stack)) {
1220 // Bailout without retry
1221 C->record_method_not_compilable("early schedule failed");
1222 return;
1223 }
1224
1225 // Build Def-Use edges.
1226 proj_list.push(_root); // Add real root as another root
1227 proj_list.pop();
1228
1229 // Compute the latency information (via backwards walk) for all the
1230 // instructions in the graph
1231 GrowableArray<uint> node_latency;
1232 _node_latency = node_latency;
1233
1234 if( C->do_scheduling() )
1235 ComputeLatenciesBackwards(visited, stack);
1236
1237 // Now schedule all codes as LATE as possible. This is the LCA in the
1238 // dominator tree of all USES of a value. Pick the block with the least
1239 // loop nesting depth that is lowest in the dominator tree.
1240 // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() )
1241 schedule_late(visited, stack);
1242 if( C->failing() ) {
1243 // schedule_late fails only when graph is incorrect.
1244 assert(!VerifyGraphEdges, "verification should have failed");
1245 return;
1246 }
1247
1248 unique = C->unique();
1249
1250 #ifndef PRODUCT
1251 if (trace_opto_pipelining()) {
1252 tty->print("\n---- Detect implicit null checks ----\n");
1253 }
1254 #endif
1255
1256 // Detect implicit-null-check opportunities. Basically, find NULL checks
1257 // with suitable memory ops nearby. Use the memory op to do the NULL check.
1258 // I can generate a memory op if there is not one nearby.
1259 if (C->is_method_compilation()) {
1260 // Don't do it for natives, adapters, or runtime stubs
1261 int allowed_reasons = 0;
1262 // ...and don't do it when there have been too many traps, globally.
1263 for (int reason = (int)Deoptimization::Reason_none+1;
1264 reason < Compile::trapHistLength; reason++) {
1265 assert(reason < BitsPerInt, "recode bit map");
1266 if (!C->too_many_traps((Deoptimization::DeoptReason) reason))
1267 allowed_reasons |= nth_bit(reason);
1268 }
1269 // By reversing the loop direction we get a very minor gain on mpegaudio.
1270 // Feel free to revert to a forward loop for clarity.
1271 // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) {
1272 for( int i= matcher._null_check_tests.size()-2; i>=0; i-=2 ) {
1273 Node *proj = matcher._null_check_tests[i ];
1274 Node *val = matcher._null_check_tests[i+1];
1275 _bbs[proj->_idx]->implicit_null_check(this, proj, val, allowed_reasons);
1276 // The implicit_null_check will only perform the transformation
1277 // if the null branch is truly uncommon, *and* it leads to an
1278 // uncommon trap. Combined with the too_many_traps guards
1279 // above, this prevents SEGV storms reported in 6366351,
1280 // by recompiling offending methods without this optimization.
1281 }
1282 }
1283
1284 #ifndef PRODUCT
1285 if (trace_opto_pipelining()) {
1286 tty->print("\n---- Start Local Scheduling ----\n");
1287 }
1288 #endif
1289
1290 // Schedule locally. Right now a simple topological sort.
1291 // Later, do a real latency aware scheduler.
1292 int *ready_cnt = NEW_RESOURCE_ARRAY(int,C->unique());
1293 memset( ready_cnt, -1, C->unique() * sizeof(int) );
1294 visited.Clear();
1295 for (i = 0; i < _num_blocks; i++) {
1296 if (!_blocks[i]->schedule_local(this, matcher, ready_cnt, visited)) {
1297 if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
1298 C->record_method_not_compilable("local schedule failed");
1299 }
1300 return;
1301 }
1302 }
1303
1304 // If we inserted any instructions between a Call and his CatchNode,
1305 // clone the instructions on all paths below the Catch.
1306 for( i=0; i < _num_blocks; i++ )
1307 _blocks[i]->call_catch_cleanup(_bbs);
1308
1309 #ifndef PRODUCT
1310 if (trace_opto_pipelining()) {
1311 tty->print("\n---- After GlobalCodeMotion ----\n");
1312 for (uint i = 0; i < _num_blocks; i++) {
1313 _blocks[i]->dump();
1314 }
1315 }
1316 #endif
1317 }
1318
1319
1320 //------------------------------Estimate_Block_Frequency-----------------------
1321 // Estimate block frequencies based on IfNode probabilities.
1322 void PhaseCFG::Estimate_Block_Frequency() {
1323 int cnts = C->method() ? C->method()->interpreter_invocation_count() : 1;
1324 // Most of our algorithms will die horribly if frequency can become
1325 // negative so make sure cnts is a sane value.
1326 if( cnts <= 0 ) cnts = 1;
1327 float f = (float)cnts/(float)FreqCountInvocations;
1328
1329 // Create the loop tree and calculate loop depth.
1330 _root_loop = create_loop_tree();
1331 _root_loop->compute_loop_depth(0);
1332
1333 // Compute block frequency of each block, relative to a single loop entry.
1334 _root_loop->compute_freq();
1335
1336 // Adjust all frequencies to be relative to a single method entry
1337 _root_loop->_freq = f * 1.0;
1338 _root_loop->scale_freq();
1339
1340 // force paths ending at uncommon traps to be infrequent
1341 Block_List worklist;
1342 Block* root_blk = _blocks[0];
1343 for (uint i = 0; i < root_blk->num_preds(); i++) {
1344 Block *pb = _bbs[root_blk->pred(i)->_idx];
1345 if (pb->has_uncommon_code()) {
1346 worklist.push(pb);
1347 }
1348 }
1349 while (worklist.size() > 0) {
1350 Block* uct = worklist.pop();
1351 uct->_freq = PROB_MIN;
1352 for (uint i = 0; i < uct->num_preds(); i++) {
1353 Block *pb = _bbs[uct->pred(i)->_idx];
1354 if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) {
1355 worklist.push(pb);
1356 }
1357 }
1358 }
1359
1360 #ifndef PRODUCT
1361 if (PrintCFGBlockFreq) {
1362 tty->print_cr("CFG Block Frequencies");
1363 _root_loop->dump_tree();
1364 if (Verbose) {
1365 tty->print_cr("PhaseCFG dump");
1366 dump();
1367 tty->print_cr("Node dump");
1368 _root->dump(99999);
1369 }
1370 }
1371 #endif
1372 }
1373
1374 //----------------------------create_loop_tree--------------------------------
1375 // Create a loop tree from the CFG
1376 CFGLoop* PhaseCFG::create_loop_tree() {
1377
1378 #ifdef ASSERT
1379 assert( _blocks[0] == _broot, "" );
1380 for (uint i = 0; i < _num_blocks; i++ ) {
1381 Block *b = _blocks[i];
1382 // Check that _loop field are clear...we could clear them if not.
1383 assert(b->_loop == NULL, "clear _loop expected");
1384 // Sanity check that the RPO numbering is reflected in the _blocks array.
1385 // It doesn't have to be for the loop tree to be built, but if it is not,
1386 // then the blocks have been reordered since dom graph building...which
1387 // may question the RPO numbering
1388 assert(b->_rpo == i, "unexpected reverse post order number");
1389 }
1390 #endif
1391
1392 int idct = 0;
1393 CFGLoop* root_loop = new CFGLoop(idct++);
1394
1395 Block_List worklist;
1396
1397 // Assign blocks to loops
1398 for(uint i = _num_blocks - 1; i > 0; i-- ) { // skip Root block
1399 Block *b = _blocks[i];
1400
1401 if (b->head()->is_Loop()) {
1402 Block* loop_head = b;
1403 assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1404 Node* tail_n = loop_head->pred(LoopNode::LoopBackControl);
1405 Block* tail = _bbs[tail_n->_idx];
1406
1407 // Defensively filter out Loop nodes for non-single-entry loops.
1408 // For all reasonable loops, the head occurs before the tail in RPO.
1409 if (i <= tail->_rpo) {
1410
1411 // The tail and (recursive) predecessors of the tail
1412 // are made members of a new loop.
1413
1414 assert(worklist.size() == 0, "nonempty worklist");
1415 CFGLoop* nloop = new CFGLoop(idct++);
1416 assert(loop_head->_loop == NULL, "just checking");
1417 loop_head->_loop = nloop;
1418 // Add to nloop so push_pred() will skip over inner loops
1419 nloop->add_member(loop_head);
1420 nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, _bbs);
1421
1422 while (worklist.size() > 0) {
1423 Block* member = worklist.pop();
1424 if (member != loop_head) {
1425 for (uint j = 1; j < member->num_preds(); j++) {
1426 nloop->push_pred(member, j, worklist, _bbs);
1427 }
1428 }
1429 }
1430 }
1431 }
1432 }
1433
1434 // Create a member list for each loop consisting
1435 // of both blocks and (immediate child) loops.
1436 for (uint i = 0; i < _num_blocks; i++) {
1437 Block *b = _blocks[i];
1438 CFGLoop* lp = b->_loop;
1439 if (lp == NULL) {
1440 // Not assigned to a loop. Add it to the method's pseudo loop.
1441 b->_loop = root_loop;
1442 lp = root_loop;
1443 }
1444 if (lp == root_loop || b != lp->head()) { // loop heads are already members
1445 lp->add_member(b);
1446 }
1447 if (lp != root_loop) {
1448 if (lp->parent() == NULL) {
1449 // Not a nested loop. Make it a child of the method's pseudo loop.
1450 root_loop->add_nested_loop(lp);
1451 }
1452 if (b == lp->head()) {
1453 // Add nested loop to member list of parent loop.
1454 lp->parent()->add_member(lp);
1455 }
1456 }
1457 }
1458
1459 return root_loop;
1460 }
1461
1462 //------------------------------push_pred--------------------------------------
1463 void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk) {
1464 Node* pred_n = blk->pred(i);
1465 Block* pred = node_to_blk[pred_n->_idx];
1466 CFGLoop *pred_loop = pred->_loop;
1467 if (pred_loop == NULL) {
1468 // Filter out blocks for non-single-entry loops.
1469 // For all reasonable loops, the head occurs before the tail in RPO.
1470 if (pred->_rpo > head()->_rpo) {
1471 pred->_loop = this;
1472 worklist.push(pred);
1473 }
1474 } else if (pred_loop != this) {
1475 // Nested loop.
1476 while (pred_loop->_parent != NULL && pred_loop->_parent != this) {
1477 pred_loop = pred_loop->_parent;
1478 }
1479 // Make pred's loop be a child
1480 if (pred_loop->_parent == NULL) {
1481 add_nested_loop(pred_loop);
1482 // Continue with loop entry predecessor.
1483 Block* pred_head = pred_loop->head();
1484 assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors");
1485 assert(pred_head != head(), "loop head in only one loop");
1486 push_pred(pred_head, LoopNode::EntryControl, worklist, node_to_blk);
1487 } else {
1488 assert(pred_loop->_parent == this && _parent == NULL, "just checking");
1489 }
1490 }
1491 }
1492
1493 //------------------------------add_nested_loop--------------------------------
1494 // Make cl a child of the current loop in the loop tree.
1495 void CFGLoop::add_nested_loop(CFGLoop* cl) {
1496 assert(_parent == NULL, "no parent yet");
1497 assert(cl != this, "not my own parent");
1498 cl->_parent = this;
1499 CFGLoop* ch = _child;
1500 if (ch == NULL) {
1501 _child = cl;
1502 } else {
1503 while (ch->_sibling != NULL) { ch = ch->_sibling; }
1504 ch->_sibling = cl;
1505 }
1506 }
1507
1508 //------------------------------compute_loop_depth-----------------------------
1509 // Store the loop depth in each CFGLoop object.
1510 // Recursively walk the children to do the same for them.
1511 void CFGLoop::compute_loop_depth(int depth) {
1512 _depth = depth;
1513 CFGLoop* ch = _child;
1514 while (ch != NULL) {
1515 ch->compute_loop_depth(depth + 1);
1516 ch = ch->_sibling;
1517 }
1518 }
1519
1520 //------------------------------compute_freq-----------------------------------
1521 // Compute the frequency of each block and loop, relative to a single entry
1522 // into the dominating loop head.
1523 void CFGLoop::compute_freq() {
1524 // Bottom up traversal of loop tree (visit inner loops first.)
1525 // Set loop head frequency to 1.0, then transitively
1526 // compute frequency for all successors in the loop,
1527 // as well as for each exit edge. Inner loops are
1528 // treated as single blocks with loop exit targets
1529 // as the successor blocks.
1530
1531 // Nested loops first
1532 CFGLoop* ch = _child;
1533 while (ch != NULL) {
1534 ch->compute_freq();
1535 ch = ch->_sibling;
1536 }
1537 assert (_members.length() > 0, "no empty loops");
1538 Block* hd = head();
1539 hd->_freq = 1.0f;
1540 for (int i = 0; i < _members.length(); i++) {
1541 CFGElement* s = _members.at(i);
1542 float freq = s->_freq;
1543 if (s->is_block()) {
1544 Block* b = s->as_Block();
1545 for (uint j = 0; j < b->_num_succs; j++) {
1546 Block* sb = b->_succs[j];
1547 update_succ_freq(sb, freq * b->succ_prob(j));
1548 }
1549 } else {
1550 CFGLoop* lp = s->as_CFGLoop();
1551 assert(lp->_parent == this, "immediate child");
1552 for (int k = 0; k < lp->_exits.length(); k++) {
1553 Block* eb = lp->_exits.at(k).get_target();
1554 float prob = lp->_exits.at(k).get_prob();
1555 update_succ_freq(eb, freq * prob);
1556 }
1557 }
1558 }
1559
1560 #if 0
1561 // Raise frequency of the loop backedge block, in an effort
1562 // to keep it empty. Skip the method level "loop".
1563 if (_parent != NULL) {
1564 CFGElement* s = _members.at(_members.length() - 1);
1565 if (s->is_block()) {
1566 Block* bk = s->as_Block();
1567 if (bk->_num_succs == 1 && bk->_succs[0] == hd) {
1568 // almost any value >= 1.0f works
1569 // FIXME: raw constant
1570 bk->_freq = 1.05f;
1571 }
1572 }
1573 }
1574 #endif
1575
1576 // For all loops other than the outer, "method" loop,
1577 // sum and normalize the exit probability. The "method" loop
1578 // should keep the initial exit probability of 1, so that
1579 // inner blocks do not get erroneously scaled.
1580 if (_depth != 0) {
1581 // Total the exit probabilities for this loop.
1582 float exits_sum = 0.0f;
1583 for (int i = 0; i < _exits.length(); i++) {
1584 exits_sum += _exits.at(i).get_prob();
1585 }
1586
1587 // Normalize the exit probabilities. Until now, the
1588 // probabilities estimate the possibility of exit per
1589 // a single loop iteration; afterward, they estimate
1590 // the probability of exit per loop entry.
1591 for (int i = 0; i < _exits.length(); i++) {
1592 Block* et = _exits.at(i).get_target();
1593 float new_prob = _exits.at(i).get_prob() / exits_sum;
1594 BlockProbPair bpp(et, new_prob);
1595 _exits.at_put(i, bpp);
1596 }
1597
1598 // Save the total, but guard against unreasoable probability,
1599 // as the value is used to estimate the loop trip count.
1600 // An infinite trip count would blur relative block
1601 // frequencies.
1602 if (exits_sum > 1.0f) exits_sum = 1.0;
1603 if (exits_sum < PROB_MIN) exits_sum = PROB_MIN;
1604 _exit_prob = exits_sum;
1605 }
1606 }
1607
1608 //------------------------------succ_prob-------------------------------------
1609 // Determine the probability of reaching successor 'i' from the receiver block.
1610 float Block::succ_prob(uint i) {
1611 int eidx = end_idx();
1612 Node *n = _nodes[eidx]; // Get ending Node
1613 int op = n->is_Mach() ? n->as_Mach()->ideal_Opcode() : n->Opcode();
1614
1615 // Switch on branch type
1616 switch( op ) {
1617 case Op_CountedLoopEnd:
1618 case Op_If: {
1619 assert (i < 2, "just checking");
1620 // Conditionals pass on only part of their frequency
1621 float prob = n->as_MachIf()->_prob;
1622 assert(prob >= 0.0 && prob <= 1.0, "out of range probability");
1623 // If succ[i] is the FALSE branch, invert path info
1624 if( _nodes[i + eidx + 1]->Opcode() == Op_IfFalse ) {
1625 return 1.0f - prob; // not taken
1626 } else {
1627 return prob; // taken
1628 }
1629 }
1630
1631 case Op_Jump:
1632 // Divide the frequency between all successors evenly
1633 return 1.0f/_num_succs;
1634
1635 case Op_Catch: {
1636 const CatchProjNode *ci = _nodes[i + eidx + 1]->as_CatchProj();
1637 if (ci->_con == CatchProjNode::fall_through_index) {
1638 // Fall-thru path gets the lion's share.
1639 return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs;
1640 } else {
1641 // Presume exceptional paths are equally unlikely
1642 return PROB_UNLIKELY_MAG(5);
1643 }
1644 }
1645
1646 case Op_Root:
1647 case Op_Goto:
1648 // Pass frequency straight thru to target
1649 return 1.0f;
1650
1651 case Op_NeverBranch:
1652 return 0.0f;
1653
1654 case Op_TailCall:
1655 case Op_TailJump:
1656 case Op_Return:
1657 case Op_Halt:
1658 case Op_Rethrow:
1659 // Do not push out freq to root block
1660 return 0.0f;
1661
1662 default:
1663 ShouldNotReachHere();
1664 }
1665
1666 return 0.0f;
1667 }
1668
1669 //------------------------------update_succ_freq-------------------------------
1670 // Update the appropriate frequency associated with block 'b', a succesor of
1671 // a block in this loop.
1672 void CFGLoop::update_succ_freq(Block* b, float freq) {
1673 if (b->_loop == this) {
1674 if (b == head()) {
1675 // back branch within the loop
1676 // Do nothing now, the loop carried frequency will be
1677 // adjust later in scale_freq().
1678 } else {
1679 // simple branch within the loop
1680 b->_freq += freq;
1681 }
1682 } else if (!in_loop_nest(b)) {
1683 // branch is exit from this loop
1684 BlockProbPair bpp(b, freq);
1685 _exits.append(bpp);
1686 } else {
1687 // branch into nested loop
1688 CFGLoop* ch = b->_loop;
1689 ch->_freq += freq;
1690 }
1691 }
1692
1693 //------------------------------in_loop_nest-----------------------------------
1694 // Determine if block b is in the receiver's loop nest.
1695 bool CFGLoop::in_loop_nest(Block* b) {
1696 int depth = _depth;
1697 CFGLoop* b_loop = b->_loop;
1698 int b_depth = b_loop->_depth;
1699 if (depth == b_depth) {
1700 return true;
1701 }
1702 while (b_depth > depth) {
1703 b_loop = b_loop->_parent;
1704 b_depth = b_loop->_depth;
1705 }
1706 return b_loop == this;
1707 }
1708
1709 //------------------------------scale_freq-------------------------------------
1710 // Scale frequency of loops and blocks by trip counts from outer loops
1711 // Do a top down traversal of loop tree (visit outer loops first.)
1712 void CFGLoop::scale_freq() {
1713 float loop_freq = _freq * trip_count();
1714 for (int i = 0; i < _members.length(); i++) {
1715 CFGElement* s = _members.at(i);
1716 s->_freq *= loop_freq;
1717 }
1718 CFGLoop* ch = _child;
1719 while (ch != NULL) {
1720 ch->scale_freq();
1721 ch = ch->_sibling;
1722 }
1723 }
1724
1725 #ifndef PRODUCT
1726 //------------------------------dump_tree--------------------------------------
1727 void CFGLoop::dump_tree() const {
1728 dump();
1729 if (_child != NULL) _child->dump_tree();
1730 if (_sibling != NULL) _sibling->dump_tree();
1731 }
1732
1733 //------------------------------dump-------------------------------------------
1734 void CFGLoop::dump() const {
1735 for (int i = 0; i < _depth; i++) tty->print(" ");
1736 tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n",
1737 _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq);
1738 for (int i = 0; i < _depth; i++) tty->print(" ");
1739 tty->print(" members:", _id);
1740 int k = 0;
1741 for (int i = 0; i < _members.length(); i++) {
1742 if (k++ >= 6) {
1743 tty->print("\n ");
1744 for (int j = 0; j < _depth+1; j++) tty->print(" ");
1745 k = 0;
1746 }
1747 CFGElement *s = _members.at(i);
1748 if (s->is_block()) {
1749 Block *b = s->as_Block();
1750 tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq);
1751 } else {
1752 CFGLoop* lp = s->as_CFGLoop();
1753 tty->print(" L%d(%6.3f)", lp->_id, lp->_freq);
1754 }
1755 }
1756 tty->print("\n");
1757 for (int i = 0; i < _depth; i++) tty->print(" ");
1758 tty->print(" exits: ");
1759 k = 0;
1760 for (int i = 0; i < _exits.length(); i++) {
1761 if (k++ >= 7) {
1762 tty->print("\n ");
1763 for (int j = 0; j < _depth+1; j++) tty->print(" ");
1764 k = 0;
1765 }
1766 Block *blk = _exits.at(i).get_target();
1767 float prob = _exits.at(i).get_prob();
1768 tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
1769 }
1770 tty->print("\n");
1771 }
1772 #endif