1 /*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "compiler/compileLog.hpp"
28 #include "gc/shared/barrierSet.hpp"
29 #include "gc/shared/c2/barrierSetC2.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "oops/objArrayKlass.hpp"
33 #include "opto/addnode.hpp"
34 #include "opto/arraycopynode.hpp"
35 #include "opto/cfgnode.hpp"
36 #include "opto/compile.hpp"
37 #include "opto/connode.hpp"
38 #include "opto/convertnode.hpp"
39 #include "opto/loopnode.hpp"
40 #include "opto/machnode.hpp"
41 #include "opto/matcher.hpp"
42 #include "opto/memnode.hpp"
43 #include "opto/mulnode.hpp"
44 #include "opto/narrowptrnode.hpp"
45 #include "opto/phaseX.hpp"
46 #include "opto/regmask.hpp"
47 #include "opto/rootnode.hpp"
48 #include "utilities/align.hpp"
49 #include "utilities/copy.hpp"
50 #include "utilities/macros.hpp"
51 #include "utilities/vmError.hpp"
52 #if INCLUDE_ZGC
53 #include "gc/z/c2/zBarrierSetC2.hpp"
54 #endif
55
56 // Portions of code courtesy of Clifford Click
57
58 // Optimization - Graph Style
59
60 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
61
62 //=============================================================================
63 uint MemNode::size_of() const { return sizeof(*this); }
64
65 const TypePtr *MemNode::adr_type() const {
66 Node* adr = in(Address);
67 if (adr == NULL) return NULL; // node is dead
68 const TypePtr* cross_check = NULL;
69 DEBUG_ONLY(cross_check = _adr_type);
70 return calculate_adr_type(adr->bottom_type(), cross_check);
71 }
72
73 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
74 if (adr != NULL) {
75 if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
76 return true;
77 }
78 }
79 return false;
80 }
81
82 #ifndef PRODUCT
83 void MemNode::dump_spec(outputStream *st) const {
84 if (in(Address) == NULL) return; // node is dead
85 #ifndef ASSERT
86 // fake the missing field
87 const TypePtr* _adr_type = NULL;
88 if (in(Address) != NULL)
89 _adr_type = in(Address)->bottom_type()->isa_ptr();
90 #endif
91 dump_adr_type(this, _adr_type, st);
92
93 Compile* C = Compile::current();
94 if (C->alias_type(_adr_type)->is_volatile()) {
95 st->print(" Volatile!");
96 }
97 if (_unaligned_access) {
98 st->print(" unaligned");
99 }
100 if (_mismatched_access) {
101 st->print(" mismatched");
102 }
103 if (_unsafe_access) {
104 st->print(" unsafe");
105 }
106 }
107
108 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
109 st->print(" @");
110 if (adr_type == NULL) {
111 st->print("NULL");
112 } else {
113 adr_type->dump_on(st);
114 Compile* C = Compile::current();
115 Compile::AliasType* atp = NULL;
116 if (C->have_alias_type(adr_type)) atp = C->alias_type(adr_type);
117 if (atp == NULL)
118 st->print(", idx=?\?;");
119 else if (atp->index() == Compile::AliasIdxBot)
120 st->print(", idx=Bot;");
121 else if (atp->index() == Compile::AliasIdxTop)
122 st->print(", idx=Top;");
123 else if (atp->index() == Compile::AliasIdxRaw)
124 st->print(", idx=Raw;");
125 else {
126 ciField* field = atp->field();
127 if (field) {
128 st->print(", name=");
129 field->print_name_on(st);
130 }
131 st->print(", idx=%d;", atp->index());
132 }
133 }
134 }
135
136 extern void print_alias_types();
137
138 #endif
139
140 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
141 assert((t_oop != NULL), "sanity");
142 bool is_instance = t_oop->is_known_instance_field();
143 bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
144 (load != NULL) && load->is_Load() &&
145 (phase->is_IterGVN() != NULL);
146 if (!(is_instance || is_boxed_value_load))
147 return mchain; // don't try to optimize non-instance types
148 uint instance_id = t_oop->instance_id();
149 Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
150 Node *prev = NULL;
151 Node *result = mchain;
152 while (prev != result) {
153 prev = result;
154 if (result == start_mem)
155 break; // hit one of our sentinels
156 // skip over a call which does not affect this memory slice
157 if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
158 Node *proj_in = result->in(0);
159 if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
160 break; // hit one of our sentinels
161 } else if (proj_in->is_Call()) {
162 // ArrayCopyNodes processed here as well
163 CallNode *call = proj_in->as_Call();
164 if (!call->may_modify(t_oop, phase)) { // returns false for instances
165 result = call->in(TypeFunc::Memory);
166 }
167 } else if (proj_in->is_Initialize()) {
168 AllocateNode* alloc = proj_in->as_Initialize()->allocation();
169 // Stop if this is the initialization for the object instance which
170 // contains this memory slice, otherwise skip over it.
171 if ((alloc == NULL) || (alloc->_idx == instance_id)) {
172 break;
173 }
174 if (is_instance) {
175 result = proj_in->in(TypeFunc::Memory);
176 } else if (is_boxed_value_load) {
177 Node* klass = alloc->in(AllocateNode::KlassNode);
178 const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
179 if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
180 result = proj_in->in(TypeFunc::Memory); // not related allocation
181 }
182 }
183 } else if (proj_in->is_MemBar()) {
184 ArrayCopyNode* ac = NULL;
185 if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
186 break;
187 }
188 result = proj_in->in(TypeFunc::Memory);
189 } else {
190 assert(false, "unexpected projection");
191 }
192 } else if (result->is_ClearArray()) {
193 if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
194 // Can not bypass initialization of the instance
195 // we are looking for.
196 break;
197 }
198 // Otherwise skip it (the call updated 'result' value).
199 } else if (result->is_MergeMem()) {
200 result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
201 }
202 }
203 return result;
204 }
205
206 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
207 const TypeOopPtr* t_oop = t_adr->isa_oopptr();
208 if (t_oop == NULL)
209 return mchain; // don't try to optimize non-oop types
210 Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
211 bool is_instance = t_oop->is_known_instance_field();
212 PhaseIterGVN *igvn = phase->is_IterGVN();
213 if (is_instance && igvn != NULL && result->is_Phi()) {
214 PhiNode *mphi = result->as_Phi();
215 assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
216 const TypePtr *t = mphi->adr_type();
217 if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
218 (t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
219 t->is_oopptr()->cast_to_exactness(true)
220 ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
221 ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop)) {
222 // clone the Phi with our address type
223 result = mphi->split_out_instance(t_adr, igvn);
224 } else {
225 assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
226 }
227 }
228 return result;
229 }
230
231 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
232 uint alias_idx = phase->C->get_alias_index(tp);
233 Node *mem = mmem;
234 #ifdef ASSERT
235 {
236 // Check that current type is consistent with the alias index used during graph construction
237 assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
238 bool consistent = adr_check == NULL || adr_check->empty() ||
239 phase->C->must_alias(adr_check, alias_idx );
240 // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
241 if( !consistent && adr_check != NULL && !adr_check->empty() &&
242 tp->isa_aryptr() && tp->offset() == Type::OffsetBot &&
243 adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
244 ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
245 adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
246 adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
247 // don't assert if it is dead code.
248 consistent = true;
249 }
250 if( !consistent ) {
251 st->print("alias_idx==%d, adr_check==", alias_idx);
252 if( adr_check == NULL ) {
253 st->print("NULL");
254 } else {
255 adr_check->dump();
256 }
257 st->cr();
258 print_alias_types();
259 assert(consistent, "adr_check must match alias idx");
260 }
261 }
262 #endif
263 // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
264 // means an array I have not precisely typed yet. Do not do any
265 // alias stuff with it any time soon.
266 const TypeOopPtr *toop = tp->isa_oopptr();
267 if( tp->base() != Type::AnyPtr &&
268 !(toop &&
269 toop->klass() != NULL &&
270 toop->klass()->is_java_lang_Object() &&
271 toop->offset() == Type::OffsetBot) ) {
272 // compress paths and change unreachable cycles to TOP
273 // If not, we can update the input infinitely along a MergeMem cycle
274 // Equivalent code in PhiNode::Ideal
275 Node* m = phase->transform(mmem);
276 // If transformed to a MergeMem, get the desired slice
277 // Otherwise the returned node represents memory for every slice
278 mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
279 // Update input if it is progress over what we have now
280 }
281 return mem;
282 }
283
284 //--------------------------Ideal_common---------------------------------------
285 // Look for degenerate control and memory inputs. Bypass MergeMem inputs.
286 // Unhook non-raw memories from complete (macro-expanded) initializations.
287 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
288 // If our control input is a dead region, kill all below the region
289 Node *ctl = in(MemNode::Control);
290 if (ctl && remove_dead_region(phase, can_reshape))
291 return this;
292 ctl = in(MemNode::Control);
293 // Don't bother trying to transform a dead node
294 if (ctl && ctl->is_top()) return NodeSentinel;
295
296 PhaseIterGVN *igvn = phase->is_IterGVN();
297 // Wait if control on the worklist.
298 if (ctl && can_reshape && igvn != NULL) {
299 Node* bol = NULL;
300 Node* cmp = NULL;
301 if (ctl->in(0)->is_If()) {
302 assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
303 bol = ctl->in(0)->in(1);
304 if (bol->is_Bool())
305 cmp = ctl->in(0)->in(1)->in(1);
306 }
307 if (igvn->_worklist.member(ctl) ||
308 (bol != NULL && igvn->_worklist.member(bol)) ||
309 (cmp != NULL && igvn->_worklist.member(cmp)) ) {
310 // This control path may be dead.
311 // Delay this memory node transformation until the control is processed.
312 phase->is_IterGVN()->_worklist.push(this);
313 return NodeSentinel; // caller will return NULL
314 }
315 }
316 // Ignore if memory is dead, or self-loop
317 Node *mem = in(MemNode::Memory);
318 if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
319 assert(mem != this, "dead loop in MemNode::Ideal");
320
321 if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
322 // This memory slice may be dead.
323 // Delay this mem node transformation until the memory is processed.
324 phase->is_IterGVN()->_worklist.push(this);
325 return NodeSentinel; // caller will return NULL
326 }
327
328 Node *address = in(MemNode::Address);
329 const Type *t_adr = phase->type(address);
330 if (t_adr == Type::TOP) return NodeSentinel; // caller will return NULL
331
332 if (can_reshape && is_unsafe_access() && (t_adr == TypePtr::NULL_PTR)) {
333 // Unsafe off-heap access with zero address. Remove access and other control users
334 // to not confuse optimizations and add a HaltNode to fail if this is ever executed.
335 assert(ctl != NULL, "unsafe accesses should be control dependent");
336 for (DUIterator_Fast imax, i = ctl->fast_outs(imax); i < imax; i++) {
337 Node* u = ctl->fast_out(i);
338 if (u != ctl) {
339 igvn->rehash_node_delayed(u);
340 int nb = u->replace_edge(ctl, phase->C->top());
341 --i, imax -= nb;
342 }
343 }
344 Node* frame = igvn->transform(new ParmNode(phase->C->start(), TypeFunc::FramePtr));
345 Node* halt = igvn->transform(new HaltNode(ctl, frame));
346 phase->C->root()->add_req(halt);
347 return this;
348 }
349
350 if (can_reshape && igvn != NULL &&
351 (igvn->_worklist.member(address) ||
352 (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
353 // The address's base and type may change when the address is processed.
354 // Delay this mem node transformation until the address is processed.
355 phase->is_IterGVN()->_worklist.push(this);
356 return NodeSentinel; // caller will return NULL
357 }
358
359 // Do NOT remove or optimize the next lines: ensure a new alias index
360 // is allocated for an oop pointer type before Escape Analysis.
361 // Note: C++ will not remove it since the call has side effect.
362 if (t_adr->isa_oopptr()) {
363 int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
364 }
365
366 Node* base = NULL;
367 if (address->is_AddP()) {
368 base = address->in(AddPNode::Base);
369 }
370 if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
371 !t_adr->isa_rawptr()) {
372 // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
373 // Skip this node optimization if its address has TOP base.
374 return NodeSentinel; // caller will return NULL
375 }
376
377 // Avoid independent memory operations
378 Node* old_mem = mem;
379
380 // The code which unhooks non-raw memories from complete (macro-expanded)
381 // initializations was removed. After macro-expansion all stores catched
382 // by Initialize node became raw stores and there is no information
383 // which memory slices they modify. So it is unsafe to move any memory
384 // operation above these stores. Also in most cases hooked non-raw memories
385 // were already unhooked by using information from detect_ptr_independence()
386 // and find_previous_store().
387
388 if (mem->is_MergeMem()) {
389 MergeMemNode* mmem = mem->as_MergeMem();
390 const TypePtr *tp = t_adr->is_ptr();
391
392 mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
393 }
394
395 if (mem != old_mem) {
396 set_req(MemNode::Memory, mem);
397 if (can_reshape && old_mem->outcnt() == 0 && igvn != NULL) {
398 igvn->_worklist.push(old_mem);
399 }
400 if (phase->type(mem) == Type::TOP) return NodeSentinel;
401 return this;
402 }
403
404 // let the subclass continue analyzing...
405 return NULL;
406 }
407
408 // Helper function for proving some simple control dominations.
409 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
410 // Already assumes that 'dom' is available at 'sub', and that 'sub'
411 // is not a constant (dominated by the method's StartNode).
412 // Used by MemNode::find_previous_store to prove that the
413 // control input of a memory operation predates (dominates)
414 // an allocation it wants to look past.
415 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
416 if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
417 return false; // Conservative answer for dead code
418
419 // Check 'dom'. Skip Proj and CatchProj nodes.
420 dom = dom->find_exact_control(dom);
421 if (dom == NULL || dom->is_top())
422 return false; // Conservative answer for dead code
423
424 if (dom == sub) {
425 // For the case when, for example, 'sub' is Initialize and the original
426 // 'dom' is Proj node of the 'sub'.
427 return false;
428 }
429
430 if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
431 return true;
432
433 // 'dom' dominates 'sub' if its control edge and control edges
434 // of all its inputs dominate or equal to sub's control edge.
435
436 // Currently 'sub' is either Allocate, Initialize or Start nodes.
437 // Or Region for the check in LoadNode::Ideal();
438 // 'sub' should have sub->in(0) != NULL.
439 assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
440 sub->is_Region() || sub->is_Call(), "expecting only these nodes");
441
442 // Get control edge of 'sub'.
443 Node* orig_sub = sub;
444 sub = sub->find_exact_control(sub->in(0));
445 if (sub == NULL || sub->is_top())
446 return false; // Conservative answer for dead code
447
448 assert(sub->is_CFG(), "expecting control");
449
450 if (sub == dom)
451 return true;
452
453 if (sub->is_Start() || sub->is_Root())
454 return false;
455
456 {
457 // Check all control edges of 'dom'.
458
459 ResourceMark rm;
460 Arena* arena = Thread::current()->resource_area();
461 Node_List nlist(arena);
462 Unique_Node_List dom_list(arena);
463
464 dom_list.push(dom);
465 bool only_dominating_controls = false;
466
467 for (uint next = 0; next < dom_list.size(); next++) {
468 Node* n = dom_list.at(next);
469 if (n == orig_sub)
470 return false; // One of dom's inputs dominated by sub.
471 if (!n->is_CFG() && n->pinned()) {
472 // Check only own control edge for pinned non-control nodes.
473 n = n->find_exact_control(n->in(0));
474 if (n == NULL || n->is_top())
475 return false; // Conservative answer for dead code
476 assert(n->is_CFG(), "expecting control");
477 dom_list.push(n);
478 } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
479 only_dominating_controls = true;
480 } else if (n->is_CFG()) {
481 if (n->dominates(sub, nlist))
482 only_dominating_controls = true;
483 else
484 return false;
485 } else {
486 // First, own control edge.
487 Node* m = n->find_exact_control(n->in(0));
488 if (m != NULL) {
489 if (m->is_top())
490 return false; // Conservative answer for dead code
491 dom_list.push(m);
492 }
493 // Now, the rest of edges.
494 uint cnt = n->req();
495 for (uint i = 1; i < cnt; i++) {
496 m = n->find_exact_control(n->in(i));
497 if (m == NULL || m->is_top())
498 continue;
499 dom_list.push(m);
500 }
501 }
502 }
503 return only_dominating_controls;
504 }
505 }
506
507 //---------------------detect_ptr_independence---------------------------------
508 // Used by MemNode::find_previous_store to prove that two base
509 // pointers are never equal.
510 // The pointers are accompanied by their associated allocations,
511 // if any, which have been previously discovered by the caller.
512 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
513 Node* p2, AllocateNode* a2,
514 PhaseTransform* phase) {
515 // Attempt to prove that these two pointers cannot be aliased.
516 // They may both manifestly be allocations, and they should differ.
517 // Or, if they are not both allocations, they can be distinct constants.
518 // Otherwise, one is an allocation and the other a pre-existing value.
519 if (a1 == NULL && a2 == NULL) { // neither an allocation
520 return (p1 != p2) && p1->is_Con() && p2->is_Con();
521 } else if (a1 != NULL && a2 != NULL) { // both allocations
522 return (a1 != a2);
523 } else if (a1 != NULL) { // one allocation a1
524 // (Note: p2->is_Con implies p2->in(0)->is_Root, which dominates.)
525 return all_controls_dominate(p2, a1);
526 } else { //(a2 != NULL) // one allocation a2
527 return all_controls_dominate(p1, a2);
528 }
529 return false;
530 }
531
532
533 // Find an arraycopy that must have set (can_see_stored_value=true) or
534 // could have set (can_see_stored_value=false) the value for this load
535 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
536 if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
537 mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
538 Node* mb = mem->in(0);
539 if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
540 mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
541 ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
542 if (ac->is_clonebasic()) {
543 intptr_t offset;
544 AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
545 if (alloc != NULL && alloc == ld_alloc) {
546 return ac;
547 }
548 }
549 }
550 } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
551 ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
552
553 if (ac->is_arraycopy_validated() ||
554 ac->is_copyof_validated() ||
555 ac->is_copyofrange_validated()) {
556 Node* ld_addp = in(MemNode::Address);
557 if (ld_addp->is_AddP()) {
558 Node* ld_base = ld_addp->in(AddPNode::Address);
559 Node* ld_offs = ld_addp->in(AddPNode::Offset);
560
561 Node* dest = ac->in(ArrayCopyNode::Dest);
562
563 if (dest == ld_base) {
564 const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
565 if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
566 return ac;
567 }
568 if (!can_see_stored_value) {
569 mem = ac->in(TypeFunc::Memory);
570 }
571 }
572 }
573 }
574 }
575 return NULL;
576 }
577
578 // The logic for reordering loads and stores uses four steps:
579 // (a) Walk carefully past stores and initializations which we
580 // can prove are independent of this load.
581 // (b) Observe that the next memory state makes an exact match
582 // with self (load or store), and locate the relevant store.
583 // (c) Ensure that, if we were to wire self directly to the store,
584 // the optimizer would fold it up somehow.
585 // (d) Do the rewiring, and return, depending on some other part of
586 // the optimizer to fold up the load.
587 // This routine handles steps (a) and (b). Steps (c) and (d) are
588 // specific to loads and stores, so they are handled by the callers.
589 // (Currently, only LoadNode::Ideal has steps (c), (d). More later.)
590 //
591 Node* MemNode::find_previous_store(PhaseTransform* phase) {
592 Node* ctrl = in(MemNode::Control);
593 Node* adr = in(MemNode::Address);
594 intptr_t offset = 0;
595 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
596 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase);
597
598 if (offset == Type::OffsetBot)
599 return NULL; // cannot unalias unless there are precise offsets
600
601 const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
602 const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
603
604 intptr_t size_in_bytes = memory_size();
605
606 Node* mem = in(MemNode::Memory); // start searching here...
607
608 int cnt = 50; // Cycle limiter
609 for (;;) { // While we can dance past unrelated stores...
610 if (--cnt < 0) break; // Caught in cycle or a complicated dance?
611
612 Node* prev = mem;
613 if (mem->is_Store()) {
614 Node* st_adr = mem->in(MemNode::Address);
615 intptr_t st_offset = 0;
616 Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
617 if (st_base == NULL)
618 break; // inscrutable pointer
619
620 // For raw accesses it's not enough to prove that constant offsets don't intersect.
621 // We need the bases to be the equal in order for the offset check to make sense.
622 if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
623 break;
624 }
625
626 if (st_offset != offset && st_offset != Type::OffsetBot) {
627 const int MAX_STORE = BytesPerLong;
628 if (st_offset >= offset + size_in_bytes ||
629 st_offset <= offset - MAX_STORE ||
630 st_offset <= offset - mem->as_Store()->memory_size()) {
631 // Success: The offsets are provably independent.
632 // (You may ask, why not just test st_offset != offset and be done?
633 // The answer is that stores of different sizes can co-exist
634 // in the same sequence of RawMem effects. We sometimes initialize
635 // a whole 'tile' of array elements with a single jint or jlong.)
636 mem = mem->in(MemNode::Memory);
637 continue; // (a) advance through independent store memory
638 }
639 }
640 if (st_base != base &&
641 detect_ptr_independence(base, alloc,
642 st_base,
643 AllocateNode::Ideal_allocation(st_base, phase),
644 phase)) {
645 // Success: The bases are provably independent.
646 mem = mem->in(MemNode::Memory);
647 continue; // (a) advance through independent store memory
648 }
649
650 // (b) At this point, if the bases or offsets do not agree, we lose,
651 // since we have not managed to prove 'this' and 'mem' independent.
652 if (st_base == base && st_offset == offset) {
653 return mem; // let caller handle steps (c), (d)
654 }
655
656 } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
657 InitializeNode* st_init = mem->in(0)->as_Initialize();
658 AllocateNode* st_alloc = st_init->allocation();
659 if (st_alloc == NULL)
660 break; // something degenerated
661 bool known_identical = false;
662 bool known_independent = false;
663 if (alloc == st_alloc)
664 known_identical = true;
665 else if (alloc != NULL)
666 known_independent = true;
667 else if (all_controls_dominate(this, st_alloc))
668 known_independent = true;
669
670 if (known_independent) {
671 // The bases are provably independent: Either they are
672 // manifestly distinct allocations, or else the control
673 // of this load dominates the store's allocation.
674 int alias_idx = phase->C->get_alias_index(adr_type());
675 if (alias_idx == Compile::AliasIdxRaw) {
676 mem = st_alloc->in(TypeFunc::Memory);
677 } else {
678 mem = st_init->memory(alias_idx);
679 }
680 continue; // (a) advance through independent store memory
681 }
682
683 // (b) at this point, if we are not looking at a store initializing
684 // the same allocation we are loading from, we lose.
685 if (known_identical) {
686 // From caller, can_see_stored_value will consult find_captured_store.
687 return mem; // let caller handle steps (c), (d)
688 }
689
690 } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
691 if (prev != mem) {
692 // Found an arraycopy but it doesn't affect that load
693 continue;
694 }
695 // Found an arraycopy that may affect that load
696 return mem;
697 } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
698 // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
699 if (mem->is_Proj() && mem->in(0)->is_Call()) {
700 // ArrayCopyNodes processed here as well.
701 CallNode *call = mem->in(0)->as_Call();
702 if (!call->may_modify(addr_t, phase)) {
703 mem = call->in(TypeFunc::Memory);
704 continue; // (a) advance through independent call memory
705 }
706 } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
707 ArrayCopyNode* ac = NULL;
708 if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
709 break;
710 }
711 mem = mem->in(0)->in(TypeFunc::Memory);
712 continue; // (a) advance through independent MemBar memory
713 } else if (mem->is_ClearArray()) {
714 if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
715 // (the call updated 'mem' value)
716 continue; // (a) advance through independent allocation memory
717 } else {
718 // Can not bypass initialization of the instance
719 // we are looking for.
720 return mem;
721 }
722 } else if (mem->is_MergeMem()) {
723 int alias_idx = phase->C->get_alias_index(adr_type());
724 mem = mem->as_MergeMem()->memory_at(alias_idx);
725 continue; // (a) advance through independent MergeMem memory
726 }
727 }
728
729 // Unless there is an explicit 'continue', we must bail out here,
730 // because 'mem' is an inscrutable memory state (e.g., a call).
731 break;
732 }
733
734 return NULL; // bail out
735 }
736
737 //----------------------calculate_adr_type-------------------------------------
738 // Helper function. Notices when the given type of address hits top or bottom.
739 // Also, asserts a cross-check of the type against the expected address type.
740 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
741 if (t == Type::TOP) return NULL; // does not touch memory any more?
742 #ifdef PRODUCT
743 cross_check = NULL;
744 #else
745 if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump()) cross_check = NULL;
746 #endif
747 const TypePtr* tp = t->isa_ptr();
748 if (tp == NULL) {
749 assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
750 return TypePtr::BOTTOM; // touches lots of memory
751 } else {
752 #ifdef ASSERT
753 // %%%% [phh] We don't check the alias index if cross_check is
754 // TypeRawPtr::BOTTOM. Needs to be investigated.
755 if (cross_check != NULL &&
756 cross_check != TypePtr::BOTTOM &&
757 cross_check != TypeRawPtr::BOTTOM) {
758 // Recheck the alias index, to see if it has changed (due to a bug).
759 Compile* C = Compile::current();
760 assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
761 "must stay in the original alias category");
762 // The type of the address must be contained in the adr_type,
763 // disregarding "null"-ness.
764 // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
765 const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
766 assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
767 "real address must not escape from expected memory type");
768 }
769 #endif
770 return tp;
771 }
772 }
773
774 //=============================================================================
775 // Should LoadNode::Ideal() attempt to remove control edges?
776 bool LoadNode::can_remove_control() const {
777 return true;
778 }
779 uint LoadNode::size_of() const { return sizeof(*this); }
780 bool LoadNode::cmp( const Node &n ) const
781 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
782 const Type *LoadNode::bottom_type() const { return _type; }
783 uint LoadNode::ideal_reg() const {
784 return _type->ideal_reg();
785 }
786
787 #ifndef PRODUCT
788 void LoadNode::dump_spec(outputStream *st) const {
789 MemNode::dump_spec(st);
790 if( !Verbose && !WizardMode ) {
791 // standard dump does this in Verbose and WizardMode
792 st->print(" #"); _type->dump_on(st);
793 }
794 if (!depends_only_on_test()) {
795 st->print(" (does not depend only on test)");
796 }
797 }
798 #endif
799
800 #ifdef ASSERT
801 //----------------------------is_immutable_value-------------------------------
802 // Helper function to allow a raw load without control edge for some cases
803 bool LoadNode::is_immutable_value(Node* adr) {
804 return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
805 adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
806 (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
807 in_bytes(JavaThread::osthread_offset())));
808 }
809 #endif
810
811 //----------------------------LoadNode::make-----------------------------------
812 // Polymorphic factory method:
813 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
814 ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
815 Compile* C = gvn.C;
816
817 // sanity check the alias category against the created node type
818 assert(!(adr_type->isa_oopptr() &&
819 adr_type->offset() == oopDesc::klass_offset_in_bytes()),
820 "use LoadKlassNode instead");
821 assert(!(adr_type->isa_aryptr() &&
822 adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
823 "use LoadRangeNode instead");
824 // Check control edge of raw loads
825 assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
826 // oop will be recorded in oop map if load crosses safepoint
827 rt->isa_oopptr() || is_immutable_value(adr),
828 "raw memory operations should have control edge");
829 LoadNode* load = NULL;
830 switch (bt) {
831 case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(), mo, control_dependency); break;
832 case T_BYTE: load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(), mo, control_dependency); break;
833 case T_INT: load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(), mo, control_dependency); break;
834 case T_CHAR: load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(), mo, control_dependency); break;
835 case T_SHORT: load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(), mo, control_dependency); break;
836 case T_LONG: load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
837 case T_FLOAT: load = new LoadFNode (ctl, mem, adr, adr_type, rt, mo, control_dependency); break;
838 case T_DOUBLE: load = new LoadDNode (ctl, mem, adr, adr_type, rt, mo, control_dependency); break;
839 case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency); break;
840 case T_OBJECT:
841 #ifdef _LP64
842 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
843 load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
844 } else
845 #endif
846 {
847 assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
848 load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
849 }
850 break;
851 default:
852 ShouldNotReachHere();
853 break;
854 }
855 assert(load != NULL, "LoadNode should have been created");
856 if (unaligned) {
857 load->set_unaligned_access();
858 }
859 if (mismatched) {
860 load->set_mismatched_access();
861 }
862 if (unsafe) {
863 load->set_unsafe_access();
864 }
865 if (load->Opcode() == Op_LoadN) {
866 Node* ld = gvn.transform(load);
867 return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
868 }
869
870 return load;
871 }
872
873 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
874 ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
875 bool require_atomic = true;
876 LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
877 if (unaligned) {
878 load->set_unaligned_access();
879 }
880 if (mismatched) {
881 load->set_mismatched_access();
882 }
883 if (unsafe) {
884 load->set_unsafe_access();
885 }
886 return load;
887 }
888
889 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
890 ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
891 bool require_atomic = true;
892 LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, mo, control_dependency, require_atomic);
893 if (unaligned) {
894 load->set_unaligned_access();
895 }
896 if (mismatched) {
897 load->set_mismatched_access();
898 }
899 if (unsafe) {
900 load->set_unsafe_access();
901 }
902 return load;
903 }
904
905
906
907 //------------------------------hash-------------------------------------------
908 uint LoadNode::hash() const {
909 // unroll addition of interesting fields
910 return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
911 }
912
913 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
914 if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
915 bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
916 bool is_stable_ary = FoldStableValues &&
917 (tp != NULL) && (tp->isa_aryptr() != NULL) &&
918 tp->isa_aryptr()->is_stable();
919
920 return (eliminate_boxing && non_volatile) || is_stable_ary;
921 }
922
923 return false;
924 }
925
926 // Is the value loaded previously stored by an arraycopy? If so return
927 // a load node that reads from the source array so we may be able to
928 // optimize out the ArrayCopy node later.
929 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
930 Node* ld_adr = in(MemNode::Address);
931 intptr_t ld_off = 0;
932 AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
933 Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
934 if (ac != NULL) {
935 assert(ac->is_ArrayCopy(), "what kind of node can this be?");
936
937 Node* mem = ac->in(TypeFunc::Memory);
938 Node* ctl = ac->in(0);
939 Node* src = ac->in(ArrayCopyNode::Src);
940
941 if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
942 return NULL;
943 }
944
945 LoadNode* ld = clone()->as_Load();
946 Node* addp = in(MemNode::Address)->clone();
947 if (ac->as_ArrayCopy()->is_clonebasic()) {
948 assert(ld_alloc != NULL, "need an alloc");
949 assert(addp->is_AddP(), "address must be addp");
950 assert(ac->in(ArrayCopyNode::Dest)->is_AddP(), "dest must be an address");
951 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
952 assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base)), "strange pattern");
953 assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address)), "strange pattern");
954 addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
955 addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
956 } else {
957 assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
958 ac->as_ArrayCopy()->is_copyof_validated() ||
959 ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
960 assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
961 addp->set_req(AddPNode::Base, src);
962 addp->set_req(AddPNode::Address, src);
963
964 const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
965 BasicType ary_elem = ary_t->klass()->as_array_klass()->element_type()->basic_type();
966 uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
967 uint shift = exact_log2(type2aelembytes(ary_elem));
968
969 Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
970 #ifdef _LP64
971 diff = phase->transform(new ConvI2LNode(diff));
972 #endif
973 diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
974
975 Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
976 addp->set_req(AddPNode::Offset, offset);
977 }
978 addp = phase->transform(addp);
979 #ifdef ASSERT
980 const TypePtr* adr_type = phase->type(addp)->is_ptr();
981 ld->_adr_type = adr_type;
982 #endif
983 ld->set_req(MemNode::Address, addp);
984 ld->set_req(0, ctl);
985 ld->set_req(MemNode::Memory, mem);
986 // load depends on the tests that validate the arraycopy
987 ld->_control_dependency = UnknownControl;
988 return ld;
989 }
990 return NULL;
991 }
992
993
994 //---------------------------can_see_stored_value------------------------------
995 // This routine exists to make sure this set of tests is done the same
996 // everywhere. We need to make a coordinated change: first LoadNode::Ideal
997 // will change the graph shape in a way which makes memory alive twice at the
998 // same time (uses the Oracle model of aliasing), then some
999 // LoadXNode::Identity will fold things back to the equivalence-class model
1000 // of aliasing.
1001 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
1002 Node* ld_adr = in(MemNode::Address);
1003 intptr_t ld_off = 0;
1004 Node* ld_base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ld_off);
1005 Node* ld_alloc = AllocateNode::Ideal_allocation(ld_base, phase);
1006 const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
1007 Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
1008 // This is more general than load from boxing objects.
1009 if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
1010 uint alias_idx = atp->index();
1011 bool final = !atp->is_rewritable();
1012 Node* result = NULL;
1013 Node* current = st;
1014 // Skip through chains of MemBarNodes checking the MergeMems for
1015 // new states for the slice of this load. Stop once any other
1016 // kind of node is encountered. Loads from final memory can skip
1017 // through any kind of MemBar but normal loads shouldn't skip
1018 // through MemBarAcquire since the could allow them to move out of
1019 // a synchronized region.
1020 while (current->is_Proj()) {
1021 int opc = current->in(0)->Opcode();
1022 if ((final && (opc == Op_MemBarAcquire ||
1023 opc == Op_MemBarAcquireLock ||
1024 opc == Op_LoadFence)) ||
1025 opc == Op_MemBarRelease ||
1026 opc == Op_StoreFence ||
1027 opc == Op_MemBarReleaseLock ||
1028 opc == Op_MemBarStoreStore ||
1029 opc == Op_MemBarCPUOrder) {
1030 Node* mem = current->in(0)->in(TypeFunc::Memory);
1031 if (mem->is_MergeMem()) {
1032 MergeMemNode* merge = mem->as_MergeMem();
1033 Node* new_st = merge->memory_at(alias_idx);
1034 if (new_st == merge->base_memory()) {
1035 // Keep searching
1036 current = new_st;
1037 continue;
1038 }
1039 // Save the new memory state for the slice and fall through
1040 // to exit.
1041 result = new_st;
1042 }
1043 }
1044 break;
1045 }
1046 if (result != NULL) {
1047 st = result;
1048 }
1049 }
1050
1051 // Loop around twice in the case Load -> Initialize -> Store.
1052 // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1053 for (int trip = 0; trip <= 1; trip++) {
1054
1055 if (st->is_Store()) {
1056 Node* st_adr = st->in(MemNode::Address);
1057 if (!phase->eqv(st_adr, ld_adr)) {
1058 // Try harder before giving up. Unify base pointers with casts (e.g., raw/non-raw pointers).
1059 intptr_t st_off = 0;
1060 Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_off);
1061 if (ld_base == NULL) return NULL;
1062 if (st_base == NULL) return NULL;
1063 if (!ld_base->eqv_uncast(st_base, /*keep_deps=*/true)) return NULL;
1064 if (ld_off != st_off) return NULL;
1065 if (ld_off == Type::OffsetBot) return NULL;
1066 // Same base, same offset.
1067 // Possible improvement for arrays: check index value instead of absolute offset.
1068
1069 // At this point we have proven something like this setup:
1070 // B = << base >>
1071 // L = LoadQ(AddP(Check/CastPP(B), #Off))
1072 // S = StoreQ(AddP( B , #Off), V)
1073 // (Actually, we haven't yet proven the Q's are the same.)
1074 // In other words, we are loading from a casted version of
1075 // the same pointer-and-offset that we stored to.
1076 // Casted version may carry a dependency and it is respected.
1077 // Thus, we are able to replace L by V.
1078 }
1079 // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1080 if (store_Opcode() != st->Opcode())
1081 return NULL;
1082 return st->in(MemNode::ValueIn);
1083 }
1084
1085 // A load from a freshly-created object always returns zero.
1086 // (This can happen after LoadNode::Ideal resets the load's memory input
1087 // to find_captured_store, which returned InitializeNode::zero_memory.)
1088 if (st->is_Proj() && st->in(0)->is_Allocate() &&
1089 (st->in(0) == ld_alloc) &&
1090 (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1091 // return a zero value for the load's basic type
1092 // (This is one of the few places where a generic PhaseTransform
1093 // can create new nodes. Think of it as lazily manifesting
1094 // virtually pre-existing constants.)
1095 return phase->zerocon(memory_type());
1096 }
1097
1098 // A load from an initialization barrier can match a captured store.
1099 if (st->is_Proj() && st->in(0)->is_Initialize()) {
1100 InitializeNode* init = st->in(0)->as_Initialize();
1101 AllocateNode* alloc = init->allocation();
1102 if ((alloc != NULL) && (alloc == ld_alloc)) {
1103 // examine a captured store value
1104 st = init->find_captured_store(ld_off, memory_size(), phase);
1105 if (st != NULL) {
1106 continue; // take one more trip around
1107 }
1108 }
1109 }
1110
1111 // Load boxed value from result of valueOf() call is input parameter.
1112 if (this->is_Load() && ld_adr->is_AddP() &&
1113 (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1114 intptr_t ignore = 0;
1115 Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1116 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1117 base = bs->step_over_gc_barrier(base);
1118 if (base != NULL && base->is_Proj() &&
1119 base->as_Proj()->_con == TypeFunc::Parms &&
1120 base->in(0)->is_CallStaticJava() &&
1121 base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1122 return base->in(0)->in(TypeFunc::Parms);
1123 }
1124 }
1125
1126 break;
1127 }
1128
1129 return NULL;
1130 }
1131
1132 //----------------------is_instance_field_load_with_local_phi------------------
1133 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1134 if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1135 in(Address)->is_AddP() ) {
1136 const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1137 // Only instances and boxed values.
1138 if( t_oop != NULL &&
1139 (t_oop->is_ptr_to_boxed_value() ||
1140 t_oop->is_known_instance_field()) &&
1141 t_oop->offset() != Type::OffsetBot &&
1142 t_oop->offset() != Type::OffsetTop) {
1143 return true;
1144 }
1145 }
1146 return false;
1147 }
1148
1149 //------------------------------Identity---------------------------------------
1150 // Loads are identity if previous store is to same address
1151 Node* LoadNode::Identity(PhaseGVN* phase) {
1152 // If the previous store-maker is the right kind of Store, and the store is
1153 // to the same address, then we are equal to the value stored.
1154 Node* mem = in(Memory);
1155 Node* value = can_see_stored_value(mem, phase);
1156 if( value ) {
1157 // byte, short & char stores truncate naturally.
1158 // A load has to load the truncated value which requires
1159 // some sort of masking operation and that requires an
1160 // Ideal call instead of an Identity call.
1161 if (memory_size() < BytesPerInt) {
1162 // If the input to the store does not fit with the load's result type,
1163 // it must be truncated via an Ideal call.
1164 if (!phase->type(value)->higher_equal(phase->type(this)))
1165 return this;
1166 }
1167 // (This works even when value is a Con, but LoadNode::Value
1168 // usually runs first, producing the singleton type of the Con.)
1169 return value;
1170 }
1171
1172 // Search for an existing data phi which was generated before for the same
1173 // instance's field to avoid infinite generation of phis in a loop.
1174 Node *region = mem->in(0);
1175 if (is_instance_field_load_with_local_phi(region)) {
1176 const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1177 int this_index = phase->C->get_alias_index(addr_t);
1178 int this_offset = addr_t->offset();
1179 int this_iid = addr_t->instance_id();
1180 if (!addr_t->is_known_instance() &&
1181 addr_t->is_ptr_to_boxed_value()) {
1182 // Use _idx of address base (could be Phi node) for boxed values.
1183 intptr_t ignore = 0;
1184 Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1185 if (base == NULL) {
1186 return this;
1187 }
1188 this_iid = base->_idx;
1189 }
1190 const Type* this_type = bottom_type();
1191 for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1192 Node* phi = region->fast_out(i);
1193 if (phi->is_Phi() && phi != mem &&
1194 phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1195 return phi;
1196 }
1197 }
1198 }
1199
1200 return this;
1201 }
1202
1203 // Construct an equivalent unsigned load.
1204 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1205 BasicType bt = T_ILLEGAL;
1206 const Type* rt = NULL;
1207 switch (Opcode()) {
1208 case Op_LoadUB: return this;
1209 case Op_LoadUS: return this;
1210 case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1211 case Op_LoadS: bt = T_CHAR; rt = TypeInt::CHAR; break;
1212 default:
1213 assert(false, "no unsigned variant: %s", Name());
1214 return NULL;
1215 }
1216 return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1217 raw_adr_type(), rt, bt, _mo, _control_dependency,
1218 is_unaligned_access(), is_mismatched_access());
1219 }
1220
1221 // Construct an equivalent signed load.
1222 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1223 BasicType bt = T_ILLEGAL;
1224 const Type* rt = NULL;
1225 switch (Opcode()) {
1226 case Op_LoadUB: bt = T_BYTE; rt = TypeInt::BYTE; break;
1227 case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1228 case Op_LoadB: // fall through
1229 case Op_LoadS: // fall through
1230 case Op_LoadI: // fall through
1231 case Op_LoadL: return this;
1232 default:
1233 assert(false, "no signed variant: %s", Name());
1234 return NULL;
1235 }
1236 return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1237 raw_adr_type(), rt, bt, _mo, _control_dependency,
1238 is_unaligned_access(), is_mismatched_access());
1239 }
1240
1241 // We're loading from an object which has autobox behaviour.
1242 // If this object is result of a valueOf call we'll have a phi
1243 // merging a newly allocated object and a load from the cache.
1244 // We want to replace this load with the original incoming
1245 // argument to the valueOf call.
1246 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1247 assert(phase->C->eliminate_boxing(), "sanity");
1248 intptr_t ignore = 0;
1249 Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1250 if ((base == NULL) || base->is_Phi()) {
1251 // Push the loads from the phi that comes from valueOf up
1252 // through it to allow elimination of the loads and the recovery
1253 // of the original value. It is done in split_through_phi().
1254 return NULL;
1255 } else if (base->is_Load() ||
1256 (base->is_DecodeN() && base->in(1)->is_Load())) {
1257 // Eliminate the load of boxed value for integer types from the cache
1258 // array by deriving the value from the index into the array.
1259 // Capture the offset of the load and then reverse the computation.
1260
1261 // Get LoadN node which loads a boxing object from 'cache' array.
1262 if (base->is_DecodeN()) {
1263 base = base->in(1);
1264 }
1265 if (!base->in(Address)->is_AddP()) {
1266 return NULL; // Complex address
1267 }
1268 AddPNode* address = base->in(Address)->as_AddP();
1269 Node* cache_base = address->in(AddPNode::Base);
1270 if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1271 // Get ConP node which is static 'cache' field.
1272 cache_base = cache_base->in(1);
1273 }
1274 if ((cache_base != NULL) && cache_base->is_Con()) {
1275 const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1276 if ((base_type != NULL) && base_type->is_autobox_cache()) {
1277 Node* elements[4];
1278 int shift = exact_log2(type2aelembytes(T_OBJECT));
1279 int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1280 if (count > 0 && elements[0]->is_Con() &&
1281 (count == 1 ||
1282 (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1283 elements[1]->in(2) == phase->intcon(shift)))) {
1284 ciObjArray* array = base_type->const_oop()->as_obj_array();
1285 // Fetch the box object cache[0] at the base of the array and get its value
1286 ciInstance* box = array->obj_at(0)->as_instance();
1287 ciInstanceKlass* ik = box->klass()->as_instance_klass();
1288 assert(ik->is_box_klass(), "sanity");
1289 assert(ik->nof_nonstatic_fields() == 1, "change following code");
1290 if (ik->nof_nonstatic_fields() == 1) {
1291 // This should be true nonstatic_field_at requires calling
1292 // nof_nonstatic_fields so check it anyway
1293 ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1294 BasicType bt = c.basic_type();
1295 // Only integer types have boxing cache.
1296 assert(bt == T_BOOLEAN || bt == T_CHAR ||
1297 bt == T_BYTE || bt == T_SHORT ||
1298 bt == T_INT || bt == T_LONG, "wrong type = %s", type2name(bt));
1299 jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1300 if (cache_low != (int)cache_low) {
1301 return NULL; // should not happen since cache is array indexed by value
1302 }
1303 jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1304 if (offset != (int)offset) {
1305 return NULL; // should not happen since cache is array indexed by value
1306 }
1307 // Add up all the offsets making of the address of the load
1308 Node* result = elements[0];
1309 for (int i = 1; i < count; i++) {
1310 result = phase->transform(new AddXNode(result, elements[i]));
1311 }
1312 // Remove the constant offset from the address and then
1313 result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1314 // remove the scaling of the offset to recover the original index.
1315 if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1316 // Peel the shift off directly but wrap it in a dummy node
1317 // since Ideal can't return existing nodes
1318 result = new RShiftXNode(result->in(1), phase->intcon(0));
1319 } else if (result->is_Add() && result->in(2)->is_Con() &&
1320 result->in(1)->Opcode() == Op_LShiftX &&
1321 result->in(1)->in(2) == phase->intcon(shift)) {
1322 // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1323 // but for boxing cache access we know that X<<Z will not overflow
1324 // (there is range check) so we do this optimizatrion by hand here.
1325 Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1326 result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1327 } else {
1328 result = new RShiftXNode(result, phase->intcon(shift));
1329 }
1330 #ifdef _LP64
1331 if (bt != T_LONG) {
1332 result = new ConvL2INode(phase->transform(result));
1333 }
1334 #else
1335 if (bt == T_LONG) {
1336 result = new ConvI2LNode(phase->transform(result));
1337 }
1338 #endif
1339 // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1340 // Need to preserve unboxing load type if it is unsigned.
1341 switch(this->Opcode()) {
1342 case Op_LoadUB:
1343 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1344 break;
1345 case Op_LoadUS:
1346 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1347 break;
1348 }
1349 return result;
1350 }
1351 }
1352 }
1353 }
1354 }
1355 return NULL;
1356 }
1357
1358 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1359 Node* region = phi->in(0);
1360 if (region == NULL) {
1361 return false; // Wait stable graph
1362 }
1363 uint cnt = phi->req();
1364 for (uint i = 1; i < cnt; i++) {
1365 Node* rc = region->in(i);
1366 if (rc == NULL || phase->type(rc) == Type::TOP)
1367 return false; // Wait stable graph
1368 Node* in = phi->in(i);
1369 if (in == NULL || phase->type(in) == Type::TOP)
1370 return false; // Wait stable graph
1371 }
1372 return true;
1373 }
1374 //------------------------------split_through_phi------------------------------
1375 // Split instance or boxed field load through Phi.
1376 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1377 Node* mem = in(Memory);
1378 Node* address = in(Address);
1379 const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1380
1381 assert((t_oop != NULL) &&
1382 (t_oop->is_known_instance_field() ||
1383 t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1384
1385 Compile* C = phase->C;
1386 intptr_t ignore = 0;
1387 Node* base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1388 bool base_is_phi = (base != NULL) && base->is_Phi();
1389 bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1390 (base != NULL) && (base == address->in(AddPNode::Base)) &&
1391 phase->type(base)->higher_equal(TypePtr::NOTNULL);
1392
1393 if (!((mem->is_Phi() || base_is_phi) &&
1394 (load_boxed_values || t_oop->is_known_instance_field()))) {
1395 return NULL; // memory is not Phi
1396 }
1397
1398 if (mem->is_Phi()) {
1399 if (!stable_phi(mem->as_Phi(), phase)) {
1400 return NULL; // Wait stable graph
1401 }
1402 uint cnt = mem->req();
1403 // Check for loop invariant memory.
1404 if (cnt == 3) {
1405 for (uint i = 1; i < cnt; i++) {
1406 Node* in = mem->in(i);
1407 Node* m = optimize_memory_chain(in, t_oop, this, phase);
1408 if (m == mem) {
1409 if (i == 1) {
1410 // if the first edge was a loop, check second edge too.
1411 // If both are replaceable - we are in an infinite loop
1412 Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1413 if (n == mem) {
1414 break;
1415 }
1416 }
1417 set_req(Memory, mem->in(cnt - i));
1418 return this; // made change
1419 }
1420 }
1421 }
1422 }
1423 if (base_is_phi) {
1424 if (!stable_phi(base->as_Phi(), phase)) {
1425 return NULL; // Wait stable graph
1426 }
1427 uint cnt = base->req();
1428 // Check for loop invariant memory.
1429 if (cnt == 3) {
1430 for (uint i = 1; i < cnt; i++) {
1431 if (base->in(i) == base) {
1432 return NULL; // Wait stable graph
1433 }
1434 }
1435 }
1436 }
1437
1438 bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1439
1440 // Split through Phi (see original code in loopopts.cpp).
1441 assert(C->have_alias_type(t_oop), "instance should have alias type");
1442
1443 // Do nothing here if Identity will find a value
1444 // (to avoid infinite chain of value phis generation).
1445 if (!phase->eqv(this, phase->apply_identity(this)))
1446 return NULL;
1447
1448 // Select Region to split through.
1449 Node* region;
1450 if (!base_is_phi) {
1451 assert(mem->is_Phi(), "sanity");
1452 region = mem->in(0);
1453 // Skip if the region dominates some control edge of the address.
1454 if (!MemNode::all_controls_dominate(address, region))
1455 return NULL;
1456 } else if (!mem->is_Phi()) {
1457 assert(base_is_phi, "sanity");
1458 region = base->in(0);
1459 // Skip if the region dominates some control edge of the memory.
1460 if (!MemNode::all_controls_dominate(mem, region))
1461 return NULL;
1462 } else if (base->in(0) != mem->in(0)) {
1463 assert(base_is_phi && mem->is_Phi(), "sanity");
1464 if (MemNode::all_controls_dominate(mem, base->in(0))) {
1465 region = base->in(0);
1466 } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1467 region = mem->in(0);
1468 } else {
1469 return NULL; // complex graph
1470 }
1471 } else {
1472 assert(base->in(0) == mem->in(0), "sanity");
1473 region = mem->in(0);
1474 }
1475
1476 const Type* this_type = this->bottom_type();
1477 int this_index = C->get_alias_index(t_oop);
1478 int this_offset = t_oop->offset();
1479 int this_iid = t_oop->instance_id();
1480 if (!t_oop->is_known_instance() && load_boxed_values) {
1481 // Use _idx of address base for boxed values.
1482 this_iid = base->_idx;
1483 }
1484 PhaseIterGVN* igvn = phase->is_IterGVN();
1485 Node* phi = new PhiNode(region, this_type, NULL, mem->_idx, this_iid, this_index, this_offset);
1486 for (uint i = 1; i < region->req(); i++) {
1487 Node* x;
1488 Node* the_clone = NULL;
1489 if (region->in(i) == C->top()) {
1490 x = C->top(); // Dead path? Use a dead data op
1491 } else {
1492 x = this->clone(); // Else clone up the data op
1493 the_clone = x; // Remember for possible deletion.
1494 // Alter data node to use pre-phi inputs
1495 if (this->in(0) == region) {
1496 x->set_req(0, region->in(i));
1497 } else {
1498 x->set_req(0, NULL);
1499 }
1500 if (mem->is_Phi() && (mem->in(0) == region)) {
1501 x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1502 }
1503 if (address->is_Phi() && address->in(0) == region) {
1504 x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1505 }
1506 if (base_is_phi && (base->in(0) == region)) {
1507 Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1508 Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1509 x->set_req(Address, adr_x);
1510 }
1511 }
1512 // Check for a 'win' on some paths
1513 const Type *t = x->Value(igvn);
1514
1515 bool singleton = t->singleton();
1516
1517 // See comments in PhaseIdealLoop::split_thru_phi().
1518 if (singleton && t == Type::TOP) {
1519 singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1520 }
1521
1522 if (singleton) {
1523 x = igvn->makecon(t);
1524 } else {
1525 // We now call Identity to try to simplify the cloned node.
1526 // Note that some Identity methods call phase->type(this).
1527 // Make sure that the type array is big enough for
1528 // our new node, even though we may throw the node away.
1529 // (This tweaking with igvn only works because x is a new node.)
1530 igvn->set_type(x, t);
1531 // If x is a TypeNode, capture any more-precise type permanently into Node
1532 // otherwise it will be not updated during igvn->transform since
1533 // igvn->type(x) is set to x->Value() already.
1534 x->raise_bottom_type(t);
1535 Node *y = igvn->apply_identity(x);
1536 if (y != x) {
1537 x = y;
1538 } else {
1539 y = igvn->hash_find_insert(x);
1540 if (y) {
1541 x = y;
1542 } else {
1543 // Else x is a new node we are keeping
1544 // We do not need register_new_node_with_optimizer
1545 // because set_type has already been called.
1546 igvn->_worklist.push(x);
1547 }
1548 }
1549 }
1550 if (x != the_clone && the_clone != NULL) {
1551 igvn->remove_dead_node(the_clone);
1552 }
1553 phi->set_req(i, x);
1554 }
1555 // Record Phi
1556 igvn->register_new_node_with_optimizer(phi);
1557 return phi;
1558 }
1559
1560 //------------------------------Ideal------------------------------------------
1561 // If the load is from Field memory and the pointer is non-null, it might be possible to
1562 // zero out the control input.
1563 // If the offset is constant and the base is an object allocation,
1564 // try to hook me up to the exact initializing store.
1565 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1566 Node* p = MemNode::Ideal_common(phase, can_reshape);
1567 if (p) return (p == NodeSentinel) ? NULL : p;
1568
1569 Node* ctrl = in(MemNode::Control);
1570 Node* address = in(MemNode::Address);
1571 bool progress = false;
1572
1573 bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1574 phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1575
1576 // Skip up past a SafePoint control. Cannot do this for Stores because
1577 // pointer stores & cardmarks must stay on the same side of a SafePoint.
1578 if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1579 phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw &&
1580 !addr_mark &&
1581 (depends_only_on_test() || has_unknown_control_dependency())) {
1582 ctrl = ctrl->in(0);
1583 set_req(MemNode::Control,ctrl);
1584 progress = true;
1585 }
1586
1587 intptr_t ignore = 0;
1588 Node* base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1589 if (base != NULL
1590 && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1591 // Check for useless control edge in some common special cases
1592 if (in(MemNode::Control) != NULL
1593 && can_remove_control()
1594 && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1595 && all_controls_dominate(base, phase->C->start())) {
1596 // A method-invariant, non-null address (constant or 'this' argument).
1597 set_req(MemNode::Control, NULL);
1598 progress = true;
1599 }
1600 }
1601
1602 Node* mem = in(MemNode::Memory);
1603 const TypePtr *addr_t = phase->type(address)->isa_ptr();
1604
1605 if (can_reshape && (addr_t != NULL)) {
1606 // try to optimize our memory input
1607 Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1608 if (opt_mem != mem) {
1609 set_req(MemNode::Memory, opt_mem);
1610 if (phase->type( opt_mem ) == Type::TOP) return NULL;
1611 return this;
1612 }
1613 const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1614 if ((t_oop != NULL) &&
1615 (t_oop->is_known_instance_field() ||
1616 t_oop->is_ptr_to_boxed_value())) {
1617 PhaseIterGVN *igvn = phase->is_IterGVN();
1618 if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1619 // Delay this transformation until memory Phi is processed.
1620 phase->is_IterGVN()->_worklist.push(this);
1621 return NULL;
1622 }
1623 // Split instance field load through Phi.
1624 Node* result = split_through_phi(phase);
1625 if (result != NULL) return result;
1626
1627 if (t_oop->is_ptr_to_boxed_value()) {
1628 Node* result = eliminate_autobox(phase);
1629 if (result != NULL) return result;
1630 }
1631 }
1632 }
1633
1634 // Is there a dominating load that loads the same value? Leave
1635 // anything that is not a load of a field/array element (like
1636 // barriers etc.) alone
1637 if (in(0) != NULL && !adr_type()->isa_rawptr() && can_reshape) {
1638 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1639 Node *use = mem->fast_out(i);
1640 if (use != this &&
1641 use->Opcode() == Opcode() &&
1642 use->in(0) != NULL &&
1643 use->in(0) != in(0) &&
1644 use->in(Address) == in(Address)) {
1645 Node* ctl = in(0);
1646 for (int i = 0; i < 10 && ctl != NULL; i++) {
1647 ctl = IfNode::up_one_dom(ctl);
1648 if (ctl == use->in(0)) {
1649 set_req(0, use->in(0));
1650 return this;
1651 }
1652 }
1653 }
1654 }
1655 }
1656
1657 // Check for prior store with a different base or offset; make Load
1658 // independent. Skip through any number of them. Bail out if the stores
1659 // are in an endless dead cycle and report no progress. This is a key
1660 // transform for Reflection. However, if after skipping through the Stores
1661 // we can't then fold up against a prior store do NOT do the transform as
1662 // this amounts to using the 'Oracle' model of aliasing. It leaves the same
1663 // array memory alive twice: once for the hoisted Load and again after the
1664 // bypassed Store. This situation only works if EVERYBODY who does
1665 // anti-dependence work knows how to bypass. I.e. we need all
1666 // anti-dependence checks to ask the same Oracle. Right now, that Oracle is
1667 // the alias index stuff. So instead, peek through Stores and IFF we can
1668 // fold up, do so.
1669 Node* prev_mem = find_previous_store(phase);
1670 if (prev_mem != NULL) {
1671 Node* value = can_see_arraycopy_value(prev_mem, phase);
1672 if (value != NULL) {
1673 return value;
1674 }
1675 }
1676 // Steps (a), (b): Walk past independent stores to find an exact match.
1677 if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1678 // (c) See if we can fold up on the spot, but don't fold up here.
1679 // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1680 // just return a prior value, which is done by Identity calls.
1681 if (can_see_stored_value(prev_mem, phase)) {
1682 // Make ready for step (d):
1683 set_req(MemNode::Memory, prev_mem);
1684 return this;
1685 }
1686 }
1687
1688 return progress ? this : NULL;
1689 }
1690
1691 // Helper to recognize certain Klass fields which are invariant across
1692 // some group of array types (e.g., int[] or all T[] where T < Object).
1693 const Type*
1694 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1695 ciKlass* klass) const {
1696 if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1697 // The field is Klass::_modifier_flags. Return its (constant) value.
1698 // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1699 assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1700 return TypeInt::make(klass->modifier_flags());
1701 }
1702 if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1703 // The field is Klass::_access_flags. Return its (constant) value.
1704 // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1705 assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1706 return TypeInt::make(klass->access_flags());
1707 }
1708 if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1709 // The field is Klass::_layout_helper. Return its constant value if known.
1710 assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1711 return TypeInt::make(klass->layout_helper());
1712 }
1713
1714 // No match.
1715 return NULL;
1716 }
1717
1718 //------------------------------Value-----------------------------------------
1719 const Type* LoadNode::Value(PhaseGVN* phase) const {
1720 // Either input is TOP ==> the result is TOP
1721 Node* mem = in(MemNode::Memory);
1722 const Type *t1 = phase->type(mem);
1723 if (t1 == Type::TOP) return Type::TOP;
1724 Node* adr = in(MemNode::Address);
1725 const TypePtr* tp = phase->type(adr)->isa_ptr();
1726 if (tp == NULL || tp->empty()) return Type::TOP;
1727 int off = tp->offset();
1728 assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1729 Compile* C = phase->C;
1730
1731 // Try to guess loaded type from pointer type
1732 if (tp->isa_aryptr()) {
1733 const TypeAryPtr* ary = tp->is_aryptr();
1734 const Type* t = ary->elem();
1735
1736 // Determine whether the reference is beyond the header or not, by comparing
1737 // the offset against the offset of the start of the array's data.
1738 // Different array types begin at slightly different offsets (12 vs. 16).
1739 // We choose T_BYTE as an example base type that is least restrictive
1740 // as to alignment, which will therefore produce the smallest
1741 // possible base offset.
1742 const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1743 const bool off_beyond_header = (off >= min_base_off);
1744
1745 // Try to constant-fold a stable array element.
1746 if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1747 // Make sure the reference is not into the header and the offset is constant
1748 ciObject* aobj = ary->const_oop();
1749 if (aobj != NULL && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1750 int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1751 const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1752 stable_dimension,
1753 memory_type(), is_unsigned());
1754 if (con_type != NULL) {
1755 return con_type;
1756 }
1757 }
1758 }
1759
1760 // Don't do this for integer types. There is only potential profit if
1761 // the element type t is lower than _type; that is, for int types, if _type is
1762 // more restrictive than t. This only happens here if one is short and the other
1763 // char (both 16 bits), and in those cases we've made an intentional decision
1764 // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1765 // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1766 //
1767 // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1768 // where the _gvn.type of the AddP is wider than 8. This occurs when an earlier
1769 // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1770 // subsumed by p1. If p1 is on the worklist but has not yet been re-transformed,
1771 // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1772 // In fact, that could have been the original type of p1, and p1 could have
1773 // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1774 // expression (LShiftL quux 3) independently optimized to the constant 8.
1775 if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1776 && (_type->isa_vect() == NULL)
1777 && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1778 // t might actually be lower than _type, if _type is a unique
1779 // concrete subclass of abstract class t.
1780 if (off_beyond_header || off == Type::OffsetBot) { // is the offset beyond the header?
1781 const Type* jt = t->join_speculative(_type);
1782 // In any case, do not allow the join, per se, to empty out the type.
1783 if (jt->empty() && !t->empty()) {
1784 // This can happen if a interface-typed array narrows to a class type.
1785 jt = _type;
1786 }
1787 #ifdef ASSERT
1788 if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1789 // The pointers in the autobox arrays are always non-null
1790 Node* base = adr->in(AddPNode::Base);
1791 if ((base != NULL) && base->is_DecodeN()) {
1792 // Get LoadN node which loads IntegerCache.cache field
1793 base = base->in(1);
1794 }
1795 if ((base != NULL) && base->is_Con()) {
1796 const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1797 if ((base_type != NULL) && base_type->is_autobox_cache()) {
1798 // It could be narrow oop
1799 assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1800 }
1801 }
1802 }
1803 #endif
1804 return jt;
1805 }
1806 }
1807 } else if (tp->base() == Type::InstPtr) {
1808 assert( off != Type::OffsetBot ||
1809 // arrays can be cast to Objects
1810 tp->is_oopptr()->klass()->is_java_lang_Object() ||
1811 // unsafe field access may not have a constant offset
1812 C->has_unsafe_access(),
1813 "Field accesses must be precise" );
1814 // For oop loads, we expect the _type to be precise.
1815
1816 // Optimize loads from constant fields.
1817 const TypeInstPtr* tinst = tp->is_instptr();
1818 ciObject* const_oop = tinst->const_oop();
1819 if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
1820 const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
1821 if (con_type != NULL) {
1822 return con_type;
1823 }
1824 }
1825 } else if (tp->base() == Type::KlassPtr) {
1826 assert( off != Type::OffsetBot ||
1827 // arrays can be cast to Objects
1828 tp->is_klassptr()->klass()->is_java_lang_Object() ||
1829 // also allow array-loading from the primary supertype
1830 // array during subtype checks
1831 Opcode() == Op_LoadKlass,
1832 "Field accesses must be precise" );
1833 // For klass/static loads, we expect the _type to be precise
1834 } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
1835 /* With mirrors being an indirect in the Klass*
1836 * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
1837 * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
1838 *
1839 * So check the type and klass of the node before the LoadP.
1840 */
1841 Node* adr2 = adr->in(MemNode::Address);
1842 const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1843 if (tkls != NULL && !StressReflectiveCode) {
1844 ciKlass* klass = tkls->klass();
1845 if (klass->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1846 assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1847 assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1848 return TypeInstPtr::make(klass->java_mirror());
1849 }
1850 }
1851 }
1852
1853 const TypeKlassPtr *tkls = tp->isa_klassptr();
1854 if (tkls != NULL && !StressReflectiveCode) {
1855 ciKlass* klass = tkls->klass();
1856 if (klass->is_loaded() && tkls->klass_is_exact()) {
1857 // We are loading a field from a Klass metaobject whose identity
1858 // is known at compile time (the type is "exact" or "precise").
1859 // Check for fields we know are maintained as constants by the VM.
1860 if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1861 // The field is Klass::_super_check_offset. Return its (constant) value.
1862 // (Folds up type checking code.)
1863 assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1864 return TypeInt::make(klass->super_check_offset());
1865 }
1866 // Compute index into primary_supers array
1867 juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1868 // Check for overflowing; use unsigned compare to handle the negative case.
1869 if( depth < ciKlass::primary_super_limit() ) {
1870 // The field is an element of Klass::_primary_supers. Return its (constant) value.
1871 // (Folds up type checking code.)
1872 assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1873 ciKlass *ss = klass->super_of_depth(depth);
1874 return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1875 }
1876 const Type* aift = load_array_final_field(tkls, klass);
1877 if (aift != NULL) return aift;
1878 }
1879
1880 // We can still check if we are loading from the primary_supers array at a
1881 // shallow enough depth. Even though the klass is not exact, entries less
1882 // than or equal to its super depth are correct.
1883 if (klass->is_loaded() ) {
1884 ciType *inner = klass;
1885 while( inner->is_obj_array_klass() )
1886 inner = inner->as_obj_array_klass()->base_element_type();
1887 if( inner->is_instance_klass() &&
1888 !inner->as_instance_klass()->flags().is_interface() ) {
1889 // Compute index into primary_supers array
1890 juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1891 // Check for overflowing; use unsigned compare to handle the negative case.
1892 if( depth < ciKlass::primary_super_limit() &&
1893 depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1894 // The field is an element of Klass::_primary_supers. Return its (constant) value.
1895 // (Folds up type checking code.)
1896 assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1897 ciKlass *ss = klass->super_of_depth(depth);
1898 return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1899 }
1900 }
1901 }
1902
1903 // If the type is enough to determine that the thing is not an array,
1904 // we can give the layout_helper a positive interval type.
1905 // This will help short-circuit some reflective code.
1906 if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1907 && !klass->is_array_klass() // not directly typed as an array
1908 && !klass->is_interface() // specifically not Serializable & Cloneable
1909 && !klass->is_java_lang_Object() // not the supertype of all T[]
1910 ) {
1911 // Note: When interfaces are reliable, we can narrow the interface
1912 // test to (klass != Serializable && klass != Cloneable).
1913 assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1914 jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1915 // The key property of this type is that it folds up tests
1916 // for array-ness, since it proves that the layout_helper is positive.
1917 // Thus, a generic value like the basic object layout helper works fine.
1918 return TypeInt::make(min_size, max_jint, Type::WidenMin);
1919 }
1920 }
1921
1922 // If we are loading from a freshly-allocated object, produce a zero,
1923 // if the load is provably beyond the header of the object.
1924 // (Also allow a variable load from a fresh array to produce zero.)
1925 const TypeOopPtr *tinst = tp->isa_oopptr();
1926 bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1927 bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1928 if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1929 Node* value = can_see_stored_value(mem,phase);
1930 if (value != NULL && value->is_Con()) {
1931 assert(value->bottom_type()->higher_equal(_type),"sanity");
1932 return value->bottom_type();
1933 }
1934 }
1935
1936 if (is_instance) {
1937 // If we have an instance type and our memory input is the
1938 // programs's initial memory state, there is no matching store,
1939 // so just return a zero of the appropriate type
1940 Node *mem = in(MemNode::Memory);
1941 if (mem->is_Parm() && mem->in(0)->is_Start()) {
1942 assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1943 return Type::get_zero_type(_type->basic_type());
1944 }
1945 }
1946 return _type;
1947 }
1948
1949 //------------------------------match_edge-------------------------------------
1950 // Do we Match on this edge index or not? Match only the address.
1951 uint LoadNode::match_edge(uint idx) const {
1952 return idx == MemNode::Address;
1953 }
1954
1955 //--------------------------LoadBNode::Ideal--------------------------------------
1956 //
1957 // If the previous store is to the same address as this load,
1958 // and the value stored was larger than a byte, replace this load
1959 // with the value stored truncated to a byte. If no truncation is
1960 // needed, the replacement is done in LoadNode::Identity().
1961 //
1962 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1963 Node* mem = in(MemNode::Memory);
1964 Node* value = can_see_stored_value(mem,phase);
1965 if( value && !phase->type(value)->higher_equal( _type ) ) {
1966 Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1967 return new RShiftINode(result, phase->intcon(24));
1968 }
1969 // Identity call will handle the case where truncation is not needed.
1970 return LoadNode::Ideal(phase, can_reshape);
1971 }
1972
1973 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1974 Node* mem = in(MemNode::Memory);
1975 Node* value = can_see_stored_value(mem,phase);
1976 if (value != NULL && value->is_Con() &&
1977 !value->bottom_type()->higher_equal(_type)) {
1978 // If the input to the store does not fit with the load's result type,
1979 // it must be truncated. We can't delay until Ideal call since
1980 // a singleton Value is needed for split_thru_phi optimization.
1981 int con = value->get_int();
1982 return TypeInt::make((con << 24) >> 24);
1983 }
1984 return LoadNode::Value(phase);
1985 }
1986
1987 //--------------------------LoadUBNode::Ideal-------------------------------------
1988 //
1989 // If the previous store is to the same address as this load,
1990 // and the value stored was larger than a byte, replace this load
1991 // with the value stored truncated to a byte. If no truncation is
1992 // needed, the replacement is done in LoadNode::Identity().
1993 //
1994 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1995 Node* mem = in(MemNode::Memory);
1996 Node* value = can_see_stored_value(mem, phase);
1997 if (value && !phase->type(value)->higher_equal(_type))
1998 return new AndINode(value, phase->intcon(0xFF));
1999 // Identity call will handle the case where truncation is not needed.
2000 return LoadNode::Ideal(phase, can_reshape);
2001 }
2002
2003 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
2004 Node* mem = in(MemNode::Memory);
2005 Node* value = can_see_stored_value(mem,phase);
2006 if (value != NULL && value->is_Con() &&
2007 !value->bottom_type()->higher_equal(_type)) {
2008 // If the input to the store does not fit with the load's result type,
2009 // it must be truncated. We can't delay until Ideal call since
2010 // a singleton Value is needed for split_thru_phi optimization.
2011 int con = value->get_int();
2012 return TypeInt::make(con & 0xFF);
2013 }
2014 return LoadNode::Value(phase);
2015 }
2016
2017 //--------------------------LoadUSNode::Ideal-------------------------------------
2018 //
2019 // If the previous store is to the same address as this load,
2020 // and the value stored was larger than a char, replace this load
2021 // with the value stored truncated to a char. If no truncation is
2022 // needed, the replacement is done in LoadNode::Identity().
2023 //
2024 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2025 Node* mem = in(MemNode::Memory);
2026 Node* value = can_see_stored_value(mem,phase);
2027 if( value && !phase->type(value)->higher_equal( _type ) )
2028 return new AndINode(value,phase->intcon(0xFFFF));
2029 // Identity call will handle the case where truncation is not needed.
2030 return LoadNode::Ideal(phase, can_reshape);
2031 }
2032
2033 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2034 Node* mem = in(MemNode::Memory);
2035 Node* value = can_see_stored_value(mem,phase);
2036 if (value != NULL && value->is_Con() &&
2037 !value->bottom_type()->higher_equal(_type)) {
2038 // If the input to the store does not fit with the load's result type,
2039 // it must be truncated. We can't delay until Ideal call since
2040 // a singleton Value is needed for split_thru_phi optimization.
2041 int con = value->get_int();
2042 return TypeInt::make(con & 0xFFFF);
2043 }
2044 return LoadNode::Value(phase);
2045 }
2046
2047 //--------------------------LoadSNode::Ideal--------------------------------------
2048 //
2049 // If the previous store is to the same address as this load,
2050 // and the value stored was larger than a short, replace this load
2051 // with the value stored truncated to a short. If no truncation is
2052 // needed, the replacement is done in LoadNode::Identity().
2053 //
2054 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2055 Node* mem = in(MemNode::Memory);
2056 Node* value = can_see_stored_value(mem,phase);
2057 if( value && !phase->type(value)->higher_equal( _type ) ) {
2058 Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
2059 return new RShiftINode(result, phase->intcon(16));
2060 }
2061 // Identity call will handle the case where truncation is not needed.
2062 return LoadNode::Ideal(phase, can_reshape);
2063 }
2064
2065 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2066 Node* mem = in(MemNode::Memory);
2067 Node* value = can_see_stored_value(mem,phase);
2068 if (value != NULL && value->is_Con() &&
2069 !value->bottom_type()->higher_equal(_type)) {
2070 // If the input to the store does not fit with the load's result type,
2071 // it must be truncated. We can't delay until Ideal call since
2072 // a singleton Value is needed for split_thru_phi optimization.
2073 int con = value->get_int();
2074 return TypeInt::make((con << 16) >> 16);
2075 }
2076 return LoadNode::Value(phase);
2077 }
2078
2079 //=============================================================================
2080 //----------------------------LoadKlassNode::make------------------------------
2081 // Polymorphic factory method:
2082 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2083 // sanity check the alias category against the created node type
2084 const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2085 assert(adr_type != NULL, "expecting TypeKlassPtr");
2086 #ifdef _LP64
2087 if (adr_type->is_ptr_to_narrowklass()) {
2088 assert(UseCompressedClassPointers, "no compressed klasses");
2089 Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2090 return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2091 }
2092 #endif
2093 assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2094 return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2095 }
2096
2097 //------------------------------Value------------------------------------------
2098 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2099 return klass_value_common(phase);
2100 }
2101
2102 // In most cases, LoadKlassNode does not have the control input set. If the control
2103 // input is set, it must not be removed (by LoadNode::Ideal()).
2104 bool LoadKlassNode::can_remove_control() const {
2105 return false;
2106 }
2107
2108 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2109 // Either input is TOP ==> the result is TOP
2110 const Type *t1 = phase->type( in(MemNode::Memory) );
2111 if (t1 == Type::TOP) return Type::TOP;
2112 Node *adr = in(MemNode::Address);
2113 const Type *t2 = phase->type( adr );
2114 if (t2 == Type::TOP) return Type::TOP;
2115 const TypePtr *tp = t2->is_ptr();
2116 if (TypePtr::above_centerline(tp->ptr()) ||
2117 tp->ptr() == TypePtr::Null) return Type::TOP;
2118
2119 // Return a more precise klass, if possible
2120 const TypeInstPtr *tinst = tp->isa_instptr();
2121 if (tinst != NULL) {
2122 ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2123 int offset = tinst->offset();
2124 if (ik == phase->C->env()->Class_klass()
2125 && (offset == java_lang_Class::klass_offset_in_bytes() ||
2126 offset == java_lang_Class::array_klass_offset_in_bytes())) {
2127 // We are loading a special hidden field from a Class mirror object,
2128 // the field which points to the VM's Klass metaobject.
2129 ciType* t = tinst->java_mirror_type();
2130 // java_mirror_type returns non-null for compile-time Class constants.
2131 if (t != NULL) {
2132 // constant oop => constant klass
2133 if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2134 if (t->is_void()) {
2135 // We cannot create a void array. Since void is a primitive type return null
2136 // klass. Users of this result need to do a null check on the returned klass.
2137 return TypePtr::NULL_PTR;
2138 }
2139 return TypeKlassPtr::make(ciArrayKlass::make(t));
2140 }
2141 if (!t->is_klass()) {
2142 // a primitive Class (e.g., int.class) has NULL for a klass field
2143 return TypePtr::NULL_PTR;
2144 }
2145 // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2146 return TypeKlassPtr::make(t->as_klass());
2147 }
2148 // non-constant mirror, so we can't tell what's going on
2149 }
2150 if( !ik->is_loaded() )
2151 return _type; // Bail out if not loaded
2152 if (offset == oopDesc::klass_offset_in_bytes()) {
2153 if (tinst->klass_is_exact()) {
2154 return TypeKlassPtr::make(ik);
2155 }
2156 // See if we can become precise: no subklasses and no interface
2157 // (Note: We need to support verified interfaces.)
2158 if (!ik->is_interface() && !ik->has_subklass()) {
2159 //assert(!UseExactTypes, "this code should be useless with exact types");
2160 // Add a dependence; if any subclass added we need to recompile
2161 if (!ik->is_final()) {
2162 // %%% should use stronger assert_unique_concrete_subtype instead
2163 phase->C->dependencies()->assert_leaf_type(ik);
2164 }
2165 // Return precise klass
2166 return TypeKlassPtr::make(ik);
2167 }
2168
2169 // Return root of possible klass
2170 return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2171 }
2172 }
2173
2174 // Check for loading klass from an array
2175 const TypeAryPtr *tary = tp->isa_aryptr();
2176 if( tary != NULL ) {
2177 ciKlass *tary_klass = tary->klass();
2178 if (tary_klass != NULL // can be NULL when at BOTTOM or TOP
2179 && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2180 if (tary->klass_is_exact()) {
2181 return TypeKlassPtr::make(tary_klass);
2182 }
2183 ciArrayKlass *ak = tary->klass()->as_array_klass();
2184 // If the klass is an object array, we defer the question to the
2185 // array component klass.
2186 if( ak->is_obj_array_klass() ) {
2187 assert( ak->is_loaded(), "" );
2188 ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2189 if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2190 ciInstanceKlass* ik = base_k->as_instance_klass();
2191 // See if we can become precise: no subklasses and no interface
2192 if (!ik->is_interface() && !ik->has_subklass()) {
2193 //assert(!UseExactTypes, "this code should be useless with exact types");
2194 // Add a dependence; if any subclass added we need to recompile
2195 if (!ik->is_final()) {
2196 phase->C->dependencies()->assert_leaf_type(ik);
2197 }
2198 // Return precise array klass
2199 return TypeKlassPtr::make(ak);
2200 }
2201 }
2202 return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2203 } else { // Found a type-array?
2204 //assert(!UseExactTypes, "this code should be useless with exact types");
2205 assert( ak->is_type_array_klass(), "" );
2206 return TypeKlassPtr::make(ak); // These are always precise
2207 }
2208 }
2209 }
2210
2211 // Check for loading klass from an array klass
2212 const TypeKlassPtr *tkls = tp->isa_klassptr();
2213 if (tkls != NULL && !StressReflectiveCode) {
2214 ciKlass* klass = tkls->klass();
2215 if( !klass->is_loaded() )
2216 return _type; // Bail out if not loaded
2217 if( klass->is_obj_array_klass() &&
2218 tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2219 ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2220 // // Always returning precise element type is incorrect,
2221 // // e.g., element type could be object and array may contain strings
2222 // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2223
2224 // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2225 // according to the element type's subclassing.
2226 return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2227 }
2228 if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2229 tkls->offset() == in_bytes(Klass::super_offset())) {
2230 ciKlass* sup = klass->as_instance_klass()->super();
2231 // The field is Klass::_super. Return its (constant) value.
2232 // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2233 return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2234 }
2235 }
2236
2237 // Bailout case
2238 return LoadNode::Value(phase);
2239 }
2240
2241 //------------------------------Identity---------------------------------------
2242 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2243 // Also feed through the klass in Allocate(...klass...)._klass.
2244 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2245 return klass_identity_common(phase);
2246 }
2247
2248 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2249 Node* x = LoadNode::Identity(phase);
2250 if (x != this) return x;
2251
2252 // Take apart the address into an oop and and offset.
2253 // Return 'this' if we cannot.
2254 Node* adr = in(MemNode::Address);
2255 intptr_t offset = 0;
2256 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2257 if (base == NULL) return this;
2258 const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2259 if (toop == NULL) return this;
2260
2261 // Step over potential GC barrier for OopHandle resolve
2262 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2263 if (bs->is_gc_barrier_node(base)) {
2264 base = bs->step_over_gc_barrier(base);
2265 }
2266
2267 // We can fetch the klass directly through an AllocateNode.
2268 // This works even if the klass is not constant (clone or newArray).
2269 if (offset == oopDesc::klass_offset_in_bytes()) {
2270 Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2271 if (allocated_klass != NULL) {
2272 return allocated_klass;
2273 }
2274 }
2275
2276 // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2277 // See inline_native_Class_query for occurrences of these patterns.
2278 // Java Example: x.getClass().isAssignableFrom(y)
2279 //
2280 // This improves reflective code, often making the Class
2281 // mirror go completely dead. (Current exception: Class
2282 // mirrors may appear in debug info, but we could clean them out by
2283 // introducing a new debug info operator for Klass.java_mirror).
2284
2285 if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2286 && offset == java_lang_Class::klass_offset_in_bytes()) {
2287 if (base->is_Load()) {
2288 Node* base2 = base->in(MemNode::Address);
2289 if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2290 Node* adr2 = base2->in(MemNode::Address);
2291 const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2292 if (tkls != NULL && !tkls->empty()
2293 && (tkls->klass()->is_instance_klass() ||
2294 tkls->klass()->is_array_klass())
2295 && adr2->is_AddP()
2296 ) {
2297 int mirror_field = in_bytes(Klass::java_mirror_offset());
2298 if (tkls->offset() == mirror_field) {
2299 return adr2->in(AddPNode::Base);
2300 }
2301 }
2302 }
2303 }
2304 }
2305
2306 return this;
2307 }
2308
2309
2310 //------------------------------Value------------------------------------------
2311 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2312 const Type *t = klass_value_common(phase);
2313 if (t == Type::TOP)
2314 return t;
2315
2316 return t->make_narrowklass();
2317 }
2318
2319 //------------------------------Identity---------------------------------------
2320 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2321 // Also feed through the klass in Allocate(...klass...)._klass.
2322 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2323 Node *x = klass_identity_common(phase);
2324
2325 const Type *t = phase->type( x );
2326 if( t == Type::TOP ) return x;
2327 if( t->isa_narrowklass()) return x;
2328 assert (!t->isa_narrowoop(), "no narrow oop here");
2329
2330 return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2331 }
2332
2333 //------------------------------Value-----------------------------------------
2334 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2335 // Either input is TOP ==> the result is TOP
2336 const Type *t1 = phase->type( in(MemNode::Memory) );
2337 if( t1 == Type::TOP ) return Type::TOP;
2338 Node *adr = in(MemNode::Address);
2339 const Type *t2 = phase->type( adr );
2340 if( t2 == Type::TOP ) return Type::TOP;
2341 const TypePtr *tp = t2->is_ptr();
2342 if (TypePtr::above_centerline(tp->ptr())) return Type::TOP;
2343 const TypeAryPtr *tap = tp->isa_aryptr();
2344 if( !tap ) return _type;
2345 return tap->size();
2346 }
2347
2348 //-------------------------------Ideal---------------------------------------
2349 // Feed through the length in AllocateArray(...length...)._length.
2350 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2351 Node* p = MemNode::Ideal_common(phase, can_reshape);
2352 if (p) return (p == NodeSentinel) ? NULL : p;
2353
2354 // Take apart the address into an oop and and offset.
2355 // Return 'this' if we cannot.
2356 Node* adr = in(MemNode::Address);
2357 intptr_t offset = 0;
2358 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2359 if (base == NULL) return NULL;
2360 const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2361 if (tary == NULL) return NULL;
2362
2363 // We can fetch the length directly through an AllocateArrayNode.
2364 // This works even if the length is not constant (clone or newArray).
2365 if (offset == arrayOopDesc::length_offset_in_bytes()) {
2366 AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2367 if (alloc != NULL) {
2368 Node* allocated_length = alloc->Ideal_length();
2369 Node* len = alloc->make_ideal_length(tary, phase);
2370 if (allocated_length != len) {
2371 // New CastII improves on this.
2372 return len;
2373 }
2374 }
2375 }
2376
2377 return NULL;
2378 }
2379
2380 //------------------------------Identity---------------------------------------
2381 // Feed through the length in AllocateArray(...length...)._length.
2382 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2383 Node* x = LoadINode::Identity(phase);
2384 if (x != this) return x;
2385
2386 // Take apart the address into an oop and and offset.
2387 // Return 'this' if we cannot.
2388 Node* adr = in(MemNode::Address);
2389 intptr_t offset = 0;
2390 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2391 if (base == NULL) return this;
2392 const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2393 if (tary == NULL) return this;
2394
2395 // We can fetch the length directly through an AllocateArrayNode.
2396 // This works even if the length is not constant (clone or newArray).
2397 if (offset == arrayOopDesc::length_offset_in_bytes()) {
2398 AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2399 if (alloc != NULL) {
2400 Node* allocated_length = alloc->Ideal_length();
2401 // Do not allow make_ideal_length to allocate a CastII node.
2402 Node* len = alloc->make_ideal_length(tary, phase, false);
2403 if (allocated_length == len) {
2404 // Return allocated_length only if it would not be improved by a CastII.
2405 return allocated_length;
2406 }
2407 }
2408 }
2409
2410 return this;
2411
2412 }
2413
2414 //=============================================================================
2415 //---------------------------StoreNode::make-----------------------------------
2416 // Polymorphic factory method:
2417 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2418 assert((mo == unordered || mo == release), "unexpected");
2419 Compile* C = gvn.C;
2420 assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2421 ctl != NULL, "raw memory operations should have control edge");
2422
2423 switch (bt) {
2424 case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2425 case T_BYTE: return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2426 case T_INT: return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2427 case T_CHAR:
2428 case T_SHORT: return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2429 case T_LONG: return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2430 case T_FLOAT: return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2431 case T_DOUBLE: return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2432 case T_METADATA:
2433 case T_ADDRESS:
2434 case T_OBJECT:
2435 #ifdef _LP64
2436 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2437 val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2438 return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2439 } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2440 (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2441 adr->bottom_type()->isa_rawptr())) {
2442 val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2443 return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2444 }
2445 #endif
2446 {
2447 return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2448 }
2449 default:
2450 ShouldNotReachHere();
2451 return (StoreNode*)NULL;
2452 }
2453 }
2454
2455 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2456 bool require_atomic = true;
2457 return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2458 }
2459
2460 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2461 bool require_atomic = true;
2462 return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2463 }
2464
2465
2466 //--------------------------bottom_type----------------------------------------
2467 const Type *StoreNode::bottom_type() const {
2468 return Type::MEMORY;
2469 }
2470
2471 //------------------------------hash-------------------------------------------
2472 uint StoreNode::hash() const {
2473 // unroll addition of interesting fields
2474 //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2475
2476 // Since they are not commoned, do not hash them:
2477 return NO_HASH;
2478 }
2479
2480 //------------------------------Ideal------------------------------------------
2481 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2482 // When a store immediately follows a relevant allocation/initialization,
2483 // try to capture it into the initialization, or hoist it above.
2484 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2485 Node* p = MemNode::Ideal_common(phase, can_reshape);
2486 if (p) return (p == NodeSentinel) ? NULL : p;
2487
2488 Node* mem = in(MemNode::Memory);
2489 Node* address = in(MemNode::Address);
2490 // Back-to-back stores to same address? Fold em up. Generally
2491 // unsafe if I have intervening uses... Also disallowed for StoreCM
2492 // since they must follow each StoreP operation. Redundant StoreCMs
2493 // are eliminated just before matching in final_graph_reshape.
2494 {
2495 Node* st = mem;
2496 // If Store 'st' has more than one use, we cannot fold 'st' away.
2497 // For example, 'st' might be the final state at a conditional
2498 // return. Or, 'st' might be used by some node which is live at
2499 // the same time 'st' is live, which might be unschedulable. So,
2500 // require exactly ONE user until such time as we clone 'mem' for
2501 // each of 'mem's uses (thus making the exactly-1-user-rule hold
2502 // true).
2503 while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2504 // Looking at a dead closed cycle of memory?
2505 assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2506 assert(Opcode() == st->Opcode() ||
2507 st->Opcode() == Op_StoreVector ||
2508 Opcode() == Op_StoreVector ||
2509 phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2510 (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2511 (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2512 (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2513 "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2514
2515 if (st->in(MemNode::Address)->eqv_uncast(address) &&
2516 st->as_Store()->memory_size() <= this->memory_size()) {
2517 Node* use = st->raw_out(0);
2518 phase->igvn_rehash_node_delayed(use);
2519 if (can_reshape) {
2520 use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2521 } else {
2522 // It's OK to do this in the parser, since DU info is always accurate,
2523 // and the parser always refers to nodes via SafePointNode maps.
2524 use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2525 }
2526 return this;
2527 }
2528 st = st->in(MemNode::Memory);
2529 }
2530 }
2531
2532
2533 // Capture an unaliased, unconditional, simple store into an initializer.
2534 // Or, if it is independent of the allocation, hoist it above the allocation.
2535 if (ReduceFieldZeroing && /*can_reshape &&*/
2536 mem->is_Proj() && mem->in(0)->is_Initialize()) {
2537 InitializeNode* init = mem->in(0)->as_Initialize();
2538 intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2539 if (offset > 0) {
2540 Node* moved = init->capture_store(this, offset, phase, can_reshape);
2541 // If the InitializeNode captured me, it made a raw copy of me,
2542 // and I need to disappear.
2543 if (moved != NULL) {
2544 // %%% hack to ensure that Ideal returns a new node:
2545 mem = MergeMemNode::make(mem);
2546 return mem; // fold me away
2547 }
2548 }
2549 }
2550
2551 return NULL; // No further progress
2552 }
2553
2554 //------------------------------Value-----------------------------------------
2555 const Type* StoreNode::Value(PhaseGVN* phase) const {
2556 // Either input is TOP ==> the result is TOP
2557 const Type *t1 = phase->type( in(MemNode::Memory) );
2558 if( t1 == Type::TOP ) return Type::TOP;
2559 const Type *t2 = phase->type( in(MemNode::Address) );
2560 if( t2 == Type::TOP ) return Type::TOP;
2561 const Type *t3 = phase->type( in(MemNode::ValueIn) );
2562 if( t3 == Type::TOP ) return Type::TOP;
2563 return Type::MEMORY;
2564 }
2565
2566 //------------------------------Identity---------------------------------------
2567 // Remove redundant stores:
2568 // Store(m, p, Load(m, p)) changes to m.
2569 // Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2570 Node* StoreNode::Identity(PhaseGVN* phase) {
2571 Node* mem = in(MemNode::Memory);
2572 Node* adr = in(MemNode::Address);
2573 Node* val = in(MemNode::ValueIn);
2574
2575 Node* result = this;
2576
2577 // Load then Store? Then the Store is useless
2578 if (val->is_Load() &&
2579 val->in(MemNode::Address)->eqv_uncast(adr) &&
2580 val->in(MemNode::Memory )->eqv_uncast(mem) &&
2581 val->as_Load()->store_Opcode() == Opcode()) {
2582 result = mem;
2583 }
2584
2585 // Two stores in a row of the same value?
2586 if (result == this &&
2587 mem->is_Store() &&
2588 mem->in(MemNode::Address)->eqv_uncast(adr) &&
2589 mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2590 mem->Opcode() == Opcode()) {
2591 result = mem;
2592 }
2593
2594 // Store of zero anywhere into a freshly-allocated object?
2595 // Then the store is useless.
2596 // (It must already have been captured by the InitializeNode.)
2597 if (result == this &&
2598 ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2599 // a newly allocated object is already all-zeroes everywhere
2600 if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2601 result = mem;
2602 }
2603
2604 if (result == this) {
2605 // the store may also apply to zero-bits in an earlier object
2606 Node* prev_mem = find_previous_store(phase);
2607 // Steps (a), (b): Walk past independent stores to find an exact match.
2608 if (prev_mem != NULL) {
2609 Node* prev_val = can_see_stored_value(prev_mem, phase);
2610 if (prev_val != NULL && phase->eqv(prev_val, val)) {
2611 // prev_val and val might differ by a cast; it would be good
2612 // to keep the more informative of the two.
2613 result = mem;
2614 }
2615 }
2616 }
2617 }
2618
2619 if (result != this && phase->is_IterGVN() != NULL) {
2620 MemBarNode* trailing = trailing_membar();
2621 if (trailing != NULL) {
2622 #ifdef ASSERT
2623 const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2624 assert(t_oop == NULL || t_oop->is_known_instance_field(), "only for non escaping objects");
2625 #endif
2626 PhaseIterGVN* igvn = phase->is_IterGVN();
2627 trailing->remove(igvn);
2628 }
2629 }
2630
2631 return result;
2632 }
2633
2634 //------------------------------match_edge-------------------------------------
2635 // Do we Match on this edge index or not? Match only memory & value
2636 uint StoreNode::match_edge(uint idx) const {
2637 return idx == MemNode::Address || idx == MemNode::ValueIn;
2638 }
2639
2640 //------------------------------cmp--------------------------------------------
2641 // Do not common stores up together. They generally have to be split
2642 // back up anyways, so do not bother.
2643 bool StoreNode::cmp( const Node &n ) const {
2644 return (&n == this); // Always fail except on self
2645 }
2646
2647 //------------------------------Ideal_masked_input-----------------------------
2648 // Check for a useless mask before a partial-word store
2649 // (StoreB ... (AndI valIn conIa) )
2650 // If (conIa & mask == mask) this simplifies to
2651 // (StoreB ... (valIn) )
2652 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2653 Node *val = in(MemNode::ValueIn);
2654 if( val->Opcode() == Op_AndI ) {
2655 const TypeInt *t = phase->type( val->in(2) )->isa_int();
2656 if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2657 set_req(MemNode::ValueIn, val->in(1));
2658 return this;
2659 }
2660 }
2661 return NULL;
2662 }
2663
2664
2665 //------------------------------Ideal_sign_extended_input----------------------
2666 // Check for useless sign-extension before a partial-word store
2667 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2668 // If (conIL == conIR && conIR <= num_bits) this simplifies to
2669 // (StoreB ... (valIn) )
2670 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2671 Node *val = in(MemNode::ValueIn);
2672 if( val->Opcode() == Op_RShiftI ) {
2673 const TypeInt *t = phase->type( val->in(2) )->isa_int();
2674 if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2675 Node *shl = val->in(1);
2676 if( shl->Opcode() == Op_LShiftI ) {
2677 const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2678 if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2679 set_req(MemNode::ValueIn, shl->in(1));
2680 return this;
2681 }
2682 }
2683 }
2684 }
2685 return NULL;
2686 }
2687
2688 //------------------------------value_never_loaded-----------------------------------
2689 // Determine whether there are any possible loads of the value stored.
2690 // For simplicity, we actually check if there are any loads from the
2691 // address stored to, not just for loads of the value stored by this node.
2692 //
2693 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2694 Node *adr = in(Address);
2695 const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2696 if (adr_oop == NULL)
2697 return false;
2698 if (!adr_oop->is_known_instance_field())
2699 return false; // if not a distinct instance, there may be aliases of the address
2700 for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2701 Node *use = adr->fast_out(i);
2702 if (use->is_Load() || use->is_LoadStore()) {
2703 return false;
2704 }
2705 }
2706 return true;
2707 }
2708
2709 MemBarNode* StoreNode::trailing_membar() const {
2710 if (is_release()) {
2711 MemBarNode* trailing_mb = NULL;
2712 for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2713 Node* u = fast_out(i);
2714 if (u->is_MemBar()) {
2715 if (u->as_MemBar()->trailing_store()) {
2716 assert(u->Opcode() == Op_MemBarVolatile, "");
2717 assert(trailing_mb == NULL, "only one");
2718 trailing_mb = u->as_MemBar();
2719 #ifdef ASSERT
2720 Node* leading = u->as_MemBar()->leading_membar();
2721 assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2722 assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2723 assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2724 #endif
2725 } else {
2726 assert(u->as_MemBar()->standalone(), "");
2727 }
2728 }
2729 }
2730 return trailing_mb;
2731 }
2732 return NULL;
2733 }
2734
2735
2736 //=============================================================================
2737 //------------------------------Ideal------------------------------------------
2738 // If the store is from an AND mask that leaves the low bits untouched, then
2739 // we can skip the AND operation. If the store is from a sign-extension
2740 // (a left shift, then right shift) we can skip both.
2741 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2742 Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2743 if( progress != NULL ) return progress;
2744
2745 progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2746 if( progress != NULL ) return progress;
2747
2748 // Finally check the default case
2749 return StoreNode::Ideal(phase, can_reshape);
2750 }
2751
2752 //=============================================================================
2753 //------------------------------Ideal------------------------------------------
2754 // If the store is from an AND mask that leaves the low bits untouched, then
2755 // we can skip the AND operation
2756 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2757 Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2758 if( progress != NULL ) return progress;
2759
2760 progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2761 if( progress != NULL ) return progress;
2762
2763 // Finally check the default case
2764 return StoreNode::Ideal(phase, can_reshape);
2765 }
2766
2767 //=============================================================================
2768 //------------------------------Identity---------------------------------------
2769 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2770 // No need to card mark when storing a null ptr
2771 Node* my_store = in(MemNode::OopStore);
2772 if (my_store->is_Store()) {
2773 const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2774 if( t1 == TypePtr::NULL_PTR ) {
2775 return in(MemNode::Memory);
2776 }
2777 }
2778 return this;
2779 }
2780
2781 //=============================================================================
2782 //------------------------------Ideal---------------------------------------
2783 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2784 Node* progress = StoreNode::Ideal(phase, can_reshape);
2785 if (progress != NULL) return progress;
2786
2787 Node* my_store = in(MemNode::OopStore);
2788 if (my_store->is_MergeMem()) {
2789 Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2790 set_req(MemNode::OopStore, mem);
2791 return this;
2792 }
2793
2794 return NULL;
2795 }
2796
2797 //------------------------------Value-----------------------------------------
2798 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2799 // Either input is TOP ==> the result is TOP
2800 const Type *t = phase->type( in(MemNode::Memory) );
2801 if( t == Type::TOP ) return Type::TOP;
2802 t = phase->type( in(MemNode::Address) );
2803 if( t == Type::TOP ) return Type::TOP;
2804 t = phase->type( in(MemNode::ValueIn) );
2805 if( t == Type::TOP ) return Type::TOP;
2806 // If extra input is TOP ==> the result is TOP
2807 t = phase->type( in(MemNode::OopStore) );
2808 if( t == Type::TOP ) return Type::TOP;
2809
2810 return StoreNode::Value( phase );
2811 }
2812
2813
2814 //=============================================================================
2815 //----------------------------------SCMemProjNode------------------------------
2816 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2817 {
2818 return bottom_type();
2819 }
2820
2821 //=============================================================================
2822 //----------------------------------LoadStoreNode------------------------------
2823 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2824 : Node(required),
2825 _type(rt),
2826 _adr_type(at),
2827 _has_barrier(false)
2828 {
2829 init_req(MemNode::Control, c );
2830 init_req(MemNode::Memory , mem);
2831 init_req(MemNode::Address, adr);
2832 init_req(MemNode::ValueIn, val);
2833 init_class_id(Class_LoadStore);
2834 }
2835
2836 uint LoadStoreNode::ideal_reg() const {
2837 return _type->ideal_reg();
2838 }
2839
2840 bool LoadStoreNode::result_not_used() const {
2841 for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2842 Node *x = fast_out(i);
2843 if (x->Opcode() == Op_SCMemProj) continue;
2844 return false;
2845 }
2846 return true;
2847 }
2848
2849 MemBarNode* LoadStoreNode::trailing_membar() const {
2850 MemBarNode* trailing = NULL;
2851 for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2852 Node* u = fast_out(i);
2853 if (u->is_MemBar()) {
2854 if (u->as_MemBar()->trailing_load_store()) {
2855 assert(u->Opcode() == Op_MemBarAcquire, "");
2856 assert(trailing == NULL, "only one");
2857 trailing = u->as_MemBar();
2858 #ifdef ASSERT
2859 Node* leading = trailing->leading_membar();
2860 assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2861 assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
2862 assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
2863 #endif
2864 } else {
2865 assert(u->as_MemBar()->standalone(), "wrong barrier kind");
2866 }
2867 }
2868 }
2869
2870 return trailing;
2871 }
2872
2873 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2874
2875 //=============================================================================
2876 //----------------------------------LoadStoreConditionalNode--------------------
2877 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2878 init_req(ExpectedIn, ex );
2879 }
2880
2881 //=============================================================================
2882 //-------------------------------adr_type--------------------------------------
2883 const TypePtr* ClearArrayNode::adr_type() const {
2884 Node *adr = in(3);
2885 if (adr == NULL) return NULL; // node is dead
2886 return MemNode::calculate_adr_type(adr->bottom_type());
2887 }
2888
2889 //------------------------------match_edge-------------------------------------
2890 // Do we Match on this edge index or not? Do not match memory
2891 uint ClearArrayNode::match_edge(uint idx) const {
2892 return idx > 1;
2893 }
2894
2895 //------------------------------Identity---------------------------------------
2896 // Clearing a zero length array does nothing
2897 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2898 return phase->type(in(2))->higher_equal(TypeX::ZERO) ? in(1) : this;
2899 }
2900
2901 //------------------------------Idealize---------------------------------------
2902 // Clearing a short array is faster with stores
2903 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2904 // Already know this is a large node, do not try to ideal it
2905 if (!IdealizeClearArrayNode || _is_large) return NULL;
2906
2907 const int unit = BytesPerLong;
2908 const TypeX* t = phase->type(in(2))->isa_intptr_t();
2909 if (!t) return NULL;
2910 if (!t->is_con()) return NULL;
2911 intptr_t raw_count = t->get_con();
2912 intptr_t size = raw_count;
2913 if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2914 // Clearing nothing uses the Identity call.
2915 // Negative clears are possible on dead ClearArrays
2916 // (see jck test stmt114.stmt11402.val).
2917 if (size <= 0 || size % unit != 0) return NULL;
2918 intptr_t count = size / unit;
2919 // Length too long; communicate this to matchers and assemblers.
2920 // Assemblers are responsible to produce fast hardware clears for it.
2921 if (size > InitArrayShortSize) {
2922 return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
2923 }
2924 Node *mem = in(1);
2925 if( phase->type(mem)==Type::TOP ) return NULL;
2926 Node *adr = in(3);
2927 const Type* at = phase->type(adr);
2928 if( at==Type::TOP ) return NULL;
2929 const TypePtr* atp = at->isa_ptr();
2930 // adjust atp to be the correct array element address type
2931 if (atp == NULL) atp = TypePtr::BOTTOM;
2932 else atp = atp->add_offset(Type::OffsetBot);
2933 // Get base for derived pointer purposes
2934 if( adr->Opcode() != Op_AddP ) Unimplemented();
2935 Node *base = adr->in(1);
2936
2937 Node *zero = phase->makecon(TypeLong::ZERO);
2938 Node *off = phase->MakeConX(BytesPerLong);
2939 mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2940 count--;
2941 while( count-- ) {
2942 mem = phase->transform(mem);
2943 adr = phase->transform(new AddPNode(base,adr,off));
2944 mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2945 }
2946 return mem;
2947 }
2948
2949 //----------------------------step_through----------------------------------
2950 // Return allocation input memory edge if it is different instance
2951 // or itself if it is the one we are looking for.
2952 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2953 Node* n = *np;
2954 assert(n->is_ClearArray(), "sanity");
2955 intptr_t offset;
2956 AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2957 // This method is called only before Allocate nodes are expanded
2958 // during macro nodes expansion. Before that ClearArray nodes are
2959 // only generated in PhaseMacroExpand::generate_arraycopy() (before
2960 // Allocate nodes are expanded) which follows allocations.
2961 assert(alloc != NULL, "should have allocation");
2962 if (alloc->_idx == instance_id) {
2963 // Can not bypass initialization of the instance we are looking for.
2964 return false;
2965 }
2966 // Otherwise skip it.
2967 InitializeNode* init = alloc->initialization();
2968 if (init != NULL)
2969 *np = init->in(TypeFunc::Memory);
2970 else
2971 *np = alloc->in(TypeFunc::Memory);
2972 return true;
2973 }
2974
2975 //----------------------------clear_memory-------------------------------------
2976 // Generate code to initialize object storage to zero.
2977 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2978 intptr_t start_offset,
2979 Node* end_offset,
2980 PhaseGVN* phase) {
2981 intptr_t offset = start_offset;
2982
2983 int unit = BytesPerLong;
2984 if ((offset % unit) != 0) {
2985 Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2986 adr = phase->transform(adr);
2987 const TypePtr* atp = TypeRawPtr::BOTTOM;
2988 mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2989 mem = phase->transform(mem);
2990 offset += BytesPerInt;
2991 }
2992 assert((offset % unit) == 0, "");
2993
2994 // Initialize the remaining stuff, if any, with a ClearArray.
2995 return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2996 }
2997
2998 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2999 Node* start_offset,
3000 Node* end_offset,
3001 PhaseGVN* phase) {
3002 if (start_offset == end_offset) {
3003 // nothing to do
3004 return mem;
3005 }
3006
3007 int unit = BytesPerLong;
3008 Node* zbase = start_offset;
3009 Node* zend = end_offset;
3010
3011 // Scale to the unit required by the CPU:
3012 if (!Matcher::init_array_count_is_in_bytes) {
3013 Node* shift = phase->intcon(exact_log2(unit));
3014 zbase = phase->transform(new URShiftXNode(zbase, shift) );
3015 zend = phase->transform(new URShiftXNode(zend, shift) );
3016 }
3017
3018 // Bulk clear double-words
3019 Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3020 Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3021 mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3022 return phase->transform(mem);
3023 }
3024
3025 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3026 intptr_t start_offset,
3027 intptr_t end_offset,
3028 PhaseGVN* phase) {
3029 if (start_offset == end_offset) {
3030 // nothing to do
3031 return mem;
3032 }
3033
3034 assert((end_offset % BytesPerInt) == 0, "odd end offset");
3035 intptr_t done_offset = end_offset;
3036 if ((done_offset % BytesPerLong) != 0) {
3037 done_offset -= BytesPerInt;
3038 }
3039 if (done_offset > start_offset) {
3040 mem = clear_memory(ctl, mem, dest,
3041 start_offset, phase->MakeConX(done_offset), phase);
3042 }
3043 if (done_offset < end_offset) { // emit the final 32-bit store
3044 Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3045 adr = phase->transform(adr);
3046 const TypePtr* atp = TypeRawPtr::BOTTOM;
3047 mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3048 mem = phase->transform(mem);
3049 done_offset += BytesPerInt;
3050 }
3051 assert(done_offset == end_offset, "");
3052 return mem;
3053 }
3054
3055 //=============================================================================
3056 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3057 : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
3058 _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3059 #ifdef ASSERT
3060 , _pair_idx(0)
3061 #endif
3062 {
3063 init_class_id(Class_MemBar);
3064 Node* top = C->top();
3065 init_req(TypeFunc::I_O,top);
3066 init_req(TypeFunc::FramePtr,top);
3067 init_req(TypeFunc::ReturnAdr,top);
3068 if (precedent != NULL)
3069 init_req(TypeFunc::Parms, precedent);
3070 }
3071
3072 //------------------------------cmp--------------------------------------------
3073 uint MemBarNode::hash() const { return NO_HASH; }
3074 bool MemBarNode::cmp( const Node &n ) const {
3075 return (&n == this); // Always fail except on self
3076 }
3077
3078 //------------------------------make-------------------------------------------
3079 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3080 switch (opcode) {
3081 case Op_MemBarAcquire: return new MemBarAcquireNode(C, atp, pn);
3082 case Op_LoadFence: return new LoadFenceNode(C, atp, pn);
3083 case Op_MemBarRelease: return new MemBarReleaseNode(C, atp, pn);
3084 case Op_StoreFence: return new StoreFenceNode(C, atp, pn);
3085 case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3086 case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3087 case Op_MemBarVolatile: return new MemBarVolatileNode(C, atp, pn);
3088 case Op_MemBarCPUOrder: return new MemBarCPUOrderNode(C, atp, pn);
3089 case Op_OnSpinWait: return new OnSpinWaitNode(C, atp, pn);
3090 case Op_Initialize: return new InitializeNode(C, atp, pn);
3091 case Op_MemBarStoreStore: return new MemBarStoreStoreNode(C, atp, pn);
3092 default: ShouldNotReachHere(); return NULL;
3093 }
3094 }
3095
3096 void MemBarNode::remove(PhaseIterGVN *igvn) {
3097 if (outcnt() != 2) {
3098 return;
3099 }
3100 if (trailing_store() || trailing_load_store()) {
3101 MemBarNode* leading = leading_membar();
3102 if (leading != NULL) {
3103 assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3104 leading->remove(igvn);
3105 }
3106 }
3107 igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3108 igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3109 }
3110
3111 //------------------------------Ideal------------------------------------------
3112 // Return a node which is more "ideal" than the current node. Strip out
3113 // control copies
3114 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3115 if (remove_dead_region(phase, can_reshape)) return this;
3116 // Don't bother trying to transform a dead node
3117 if (in(0) && in(0)->is_top()) {
3118 return NULL;
3119 }
3120
3121 bool progress = false;
3122 // Eliminate volatile MemBars for scalar replaced objects.
3123 if (can_reshape && req() == (Precedent+1)) {
3124 bool eliminate = false;
3125 int opc = Opcode();
3126 if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3127 // Volatile field loads and stores.
3128 Node* my_mem = in(MemBarNode::Precedent);
3129 // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3130 if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3131 // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3132 // replace this Precedent (decodeN) with the Load instead.
3133 if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1)) {
3134 Node* load_node = my_mem->in(1);
3135 set_req(MemBarNode::Precedent, load_node);
3136 phase->is_IterGVN()->_worklist.push(my_mem);
3137 my_mem = load_node;
3138 } else {
3139 assert(my_mem->unique_out() == this, "sanity");
3140 del_req(Precedent);
3141 phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3142 my_mem = NULL;
3143 }
3144 progress = true;
3145 }
3146 if (my_mem != NULL && my_mem->is_Mem()) {
3147 const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3148 // Check for scalar replaced object reference.
3149 if( t_oop != NULL && t_oop->is_known_instance_field() &&
3150 t_oop->offset() != Type::OffsetBot &&
3151 t_oop->offset() != Type::OffsetTop) {
3152 eliminate = true;
3153 }
3154 }
3155 } else if (opc == Op_MemBarRelease) {
3156 // Final field stores.
3157 Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3158 if ((alloc != NULL) && alloc->is_Allocate() &&
3159 alloc->as_Allocate()->does_not_escape_thread()) {
3160 // The allocated object does not escape.
3161 eliminate = true;
3162 }
3163 }
3164 if (eliminate) {
3165 // Replace MemBar projections by its inputs.
3166 PhaseIterGVN* igvn = phase->is_IterGVN();
3167 remove(igvn);
3168 // Must return either the original node (now dead) or a new node
3169 // (Do not return a top here, since that would break the uniqueness of top.)
3170 return new ConINode(TypeInt::ZERO);
3171 }
3172 }
3173 return progress ? this : NULL;
3174 }
3175
3176 //------------------------------Value------------------------------------------
3177 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3178 if( !in(0) ) return Type::TOP;
3179 if( phase->type(in(0)) == Type::TOP )
3180 return Type::TOP;
3181 return TypeTuple::MEMBAR;
3182 }
3183
3184 //------------------------------match------------------------------------------
3185 // Construct projections for memory.
3186 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3187 switch (proj->_con) {
3188 case TypeFunc::Control:
3189 case TypeFunc::Memory:
3190 return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3191 }
3192 ShouldNotReachHere();
3193 return NULL;
3194 }
3195
3196 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3197 trailing->_kind = TrailingStore;
3198 leading->_kind = LeadingStore;
3199 #ifdef ASSERT
3200 trailing->_pair_idx = leading->_idx;
3201 leading->_pair_idx = leading->_idx;
3202 #endif
3203 }
3204
3205 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3206 trailing->_kind = TrailingLoadStore;
3207 leading->_kind = LeadingLoadStore;
3208 #ifdef ASSERT
3209 trailing->_pair_idx = leading->_idx;
3210 leading->_pair_idx = leading->_idx;
3211 #endif
3212 }
3213
3214 MemBarNode* MemBarNode::trailing_membar() const {
3215 ResourceMark rm;
3216 Node* trailing = (Node*)this;
3217 VectorSet seen(Thread::current()->resource_area());
3218 Node_Stack multis(0);
3219 do {
3220 Node* c = trailing;
3221 uint i = 0;
3222 do {
3223 trailing = NULL;
3224 for (; i < c->outcnt(); i++) {
3225 Node* next = c->raw_out(i);
3226 if (next != c && next->is_CFG()) {
3227 if (c->is_MultiBranch()) {
3228 if (multis.node() == c) {
3229 multis.set_index(i+1);
3230 } else {
3231 multis.push(c, i+1);
3232 }
3233 }
3234 trailing = next;
3235 break;
3236 }
3237 }
3238 if (trailing != NULL && !seen.test_set(trailing->_idx)) {
3239 break;
3240 }
3241 while (multis.size() > 0) {
3242 c = multis.node();
3243 i = multis.index();
3244 if (i < c->req()) {
3245 break;
3246 }
3247 multis.pop();
3248 }
3249 } while (multis.size() > 0);
3250 } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3251
3252 MemBarNode* mb = trailing->as_MemBar();
3253 assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3254 (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3255 assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3256 return mb;
3257 }
3258
3259 MemBarNode* MemBarNode::leading_membar() const {
3260 ResourceMark rm;
3261 VectorSet seen(Thread::current()->resource_area());
3262 Node_Stack regions(0);
3263 Node* leading = in(0);
3264 while (leading != NULL && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3265 while (leading == NULL || leading->is_top() || seen.test_set(leading->_idx)) {
3266 leading = NULL;
3267 while (regions.size() > 0 && leading == NULL) {
3268 Node* r = regions.node();
3269 uint i = regions.index();
3270 if (i < r->req()) {
3271 leading = r->in(i);
3272 regions.set_index(i+1);
3273 } else {
3274 regions.pop();
3275 }
3276 }
3277 if (leading == NULL) {
3278 assert(regions.size() == 0, "all paths should have been tried");
3279 return NULL;
3280 }
3281 }
3282 if (leading->is_Region()) {
3283 regions.push(leading, 2);
3284 leading = leading->in(1);
3285 } else {
3286 leading = leading->in(0);
3287 }
3288 }
3289 #ifdef ASSERT
3290 Unique_Node_List wq;
3291 wq.push((Node*)this);
3292 uint found = 0;
3293 for (uint i = 0; i < wq.size(); i++) {
3294 Node* n = wq.at(i);
3295 if (n->is_Region()) {
3296 for (uint j = 1; j < n->req(); j++) {
3297 Node* in = n->in(j);
3298 if (in != NULL && !in->is_top()) {
3299 wq.push(in);
3300 }
3301 }
3302 } else {
3303 if (n->is_MemBar() && n->as_MemBar()->leading()) {
3304 assert(n == leading, "consistency check failed");
3305 found++;
3306 } else {
3307 Node* in = n->in(0);
3308 if (in != NULL && !in->is_top()) {
3309 wq.push(in);
3310 }
3311 }
3312 }
3313 }
3314 assert(found == 1 || (found == 0 && leading == NULL), "consistency check failed");
3315 #endif
3316 if (leading == NULL) {
3317 return NULL;
3318 }
3319 MemBarNode* mb = leading->as_MemBar();
3320 assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3321 (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3322 assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3323 return mb;
3324 }
3325
3326 //===========================InitializeNode====================================
3327 // SUMMARY:
3328 // This node acts as a memory barrier on raw memory, after some raw stores.
3329 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3330 // The Initialize can 'capture' suitably constrained stores as raw inits.
3331 // It can coalesce related raw stores into larger units (called 'tiles').
3332 // It can avoid zeroing new storage for memory units which have raw inits.
3333 // At macro-expansion, it is marked 'complete', and does not optimize further.
3334 //
3335 // EXAMPLE:
3336 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3337 // ctl = incoming control; mem* = incoming memory
3338 // (Note: A star * on a memory edge denotes I/O and other standard edges.)
3339 // First allocate uninitialized memory and fill in the header:
3340 // alloc = (Allocate ctl mem* 16 #short[].klass ...)
3341 // ctl := alloc.Control; mem* := alloc.Memory*
3342 // rawmem = alloc.Memory; rawoop = alloc.RawAddress
3343 // Then initialize to zero the non-header parts of the raw memory block:
3344 // init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3345 // ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3346 // After the initialize node executes, the object is ready for service:
3347 // oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3348 // Suppose its body is immediately initialized as {1,2}:
3349 // store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3350 // store2 = (StoreC init.Control store1 (+ oop 14) 2)
3351 // mem.SLICE(#short[*]) := store2
3352 //
3353 // DETAILS:
3354 // An InitializeNode collects and isolates object initialization after
3355 // an AllocateNode and before the next possible safepoint. As a
3356 // memory barrier (MemBarNode), it keeps critical stores from drifting
3357 // down past any safepoint or any publication of the allocation.
3358 // Before this barrier, a newly-allocated object may have uninitialized bits.
3359 // After this barrier, it may be treated as a real oop, and GC is allowed.
3360 //
3361 // The semantics of the InitializeNode include an implicit zeroing of
3362 // the new object from object header to the end of the object.
3363 // (The object header and end are determined by the AllocateNode.)
3364 //
3365 // Certain stores may be added as direct inputs to the InitializeNode.
3366 // These stores must update raw memory, and they must be to addresses
3367 // derived from the raw address produced by AllocateNode, and with
3368 // a constant offset. They must be ordered by increasing offset.
3369 // The first one is at in(RawStores), the last at in(req()-1).
3370 // Unlike most memory operations, they are not linked in a chain,
3371 // but are displayed in parallel as users of the rawmem output of
3372 // the allocation.
3373 //
3374 // (See comments in InitializeNode::capture_store, which continue
3375 // the example given above.)
3376 //
3377 // When the associated Allocate is macro-expanded, the InitializeNode
3378 // may be rewritten to optimize collected stores. A ClearArrayNode
3379 // may also be created at that point to represent any required zeroing.
3380 // The InitializeNode is then marked 'complete', prohibiting further
3381 // capturing of nearby memory operations.
3382 //
3383 // During macro-expansion, all captured initializations which store
3384 // constant values of 32 bits or smaller are coalesced (if advantageous)
3385 // into larger 'tiles' 32 or 64 bits. This allows an object to be
3386 // initialized in fewer memory operations. Memory words which are
3387 // covered by neither tiles nor non-constant stores are pre-zeroed
3388 // by explicit stores of zero. (The code shape happens to do all
3389 // zeroing first, then all other stores, with both sequences occurring
3390 // in order of ascending offsets.)
3391 //
3392 // Alternatively, code may be inserted between an AllocateNode and its
3393 // InitializeNode, to perform arbitrary initialization of the new object.
3394 // E.g., the object copying intrinsics insert complex data transfers here.
3395 // The initialization must then be marked as 'complete' disable the
3396 // built-in zeroing semantics and the collection of initializing stores.
3397 //
3398 // While an InitializeNode is incomplete, reads from the memory state
3399 // produced by it are optimizable if they match the control edge and
3400 // new oop address associated with the allocation/initialization.
3401 // They return a stored value (if the offset matches) or else zero.
3402 // A write to the memory state, if it matches control and address,
3403 // and if it is to a constant offset, may be 'captured' by the
3404 // InitializeNode. It is cloned as a raw memory operation and rewired
3405 // inside the initialization, to the raw oop produced by the allocation.
3406 // Operations on addresses which are provably distinct (e.g., to
3407 // other AllocateNodes) are allowed to bypass the initialization.
3408 //
3409 // The effect of all this is to consolidate object initialization
3410 // (both arrays and non-arrays, both piecewise and bulk) into a
3411 // single location, where it can be optimized as a unit.
3412 //
3413 // Only stores with an offset less than TrackedInitializationLimit words
3414 // will be considered for capture by an InitializeNode. This puts a
3415 // reasonable limit on the complexity of optimized initializations.
3416
3417 //---------------------------InitializeNode------------------------------------
3418 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3419 : MemBarNode(C, adr_type, rawoop),
3420 _is_complete(Incomplete), _does_not_escape(false)
3421 {
3422 init_class_id(Class_Initialize);
3423
3424 assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3425 assert(in(RawAddress) == rawoop, "proper init");
3426 // Note: allocation() can be NULL, for secondary initialization barriers
3427 }
3428
3429 // Since this node is not matched, it will be processed by the
3430 // register allocator. Declare that there are no constraints
3431 // on the allocation of the RawAddress edge.
3432 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3433 // This edge should be set to top, by the set_complete. But be conservative.
3434 if (idx == InitializeNode::RawAddress)
3435 return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3436 return RegMask::Empty;
3437 }
3438
3439 Node* InitializeNode::memory(uint alias_idx) {
3440 Node* mem = in(Memory);
3441 if (mem->is_MergeMem()) {
3442 return mem->as_MergeMem()->memory_at(alias_idx);
3443 } else {
3444 // incoming raw memory is not split
3445 return mem;
3446 }
3447 }
3448
3449 bool InitializeNode::is_non_zero() {
3450 if (is_complete()) return false;
3451 remove_extra_zeroes();
3452 return (req() > RawStores);
3453 }
3454
3455 void InitializeNode::set_complete(PhaseGVN* phase) {
3456 assert(!is_complete(), "caller responsibility");
3457 _is_complete = Complete;
3458
3459 // After this node is complete, it contains a bunch of
3460 // raw-memory initializations. There is no need for
3461 // it to have anything to do with non-raw memory effects.
3462 // Therefore, tell all non-raw users to re-optimize themselves,
3463 // after skipping the memory effects of this initialization.
3464 PhaseIterGVN* igvn = phase->is_IterGVN();
3465 if (igvn) igvn->add_users_to_worklist(this);
3466 }
3467
3468 // convenience function
3469 // return false if the init contains any stores already
3470 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3471 InitializeNode* init = initialization();
3472 if (init == NULL || init->is_complete()) return false;
3473 init->remove_extra_zeroes();
3474 // for now, if this allocation has already collected any inits, bail:
3475 if (init->is_non_zero()) return false;
3476 init->set_complete(phase);
3477 return true;
3478 }
3479
3480 void InitializeNode::remove_extra_zeroes() {
3481 if (req() == RawStores) return;
3482 Node* zmem = zero_memory();
3483 uint fill = RawStores;
3484 for (uint i = fill; i < req(); i++) {
3485 Node* n = in(i);
3486 if (n->is_top() || n == zmem) continue; // skip
3487 if (fill < i) set_req(fill, n); // compact
3488 ++fill;
3489 }
3490 // delete any empty spaces created:
3491 while (fill < req()) {
3492 del_req(fill);
3493 }
3494 }
3495
3496 // Helper for remembering which stores go with which offsets.
3497 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3498 if (!st->is_Store()) return -1; // can happen to dead code via subsume_node
3499 intptr_t offset = -1;
3500 Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3501 phase, offset);
3502 if (base == NULL) return -1; // something is dead,
3503 if (offset < 0) return -1; // dead, dead
3504 return offset;
3505 }
3506
3507 // Helper for proving that an initialization expression is
3508 // "simple enough" to be folded into an object initialization.
3509 // Attempts to prove that a store's initial value 'n' can be captured
3510 // within the initialization without creating a vicious cycle, such as:
3511 // { Foo p = new Foo(); p.next = p; }
3512 // True for constants and parameters and small combinations thereof.
3513 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3514 if (n == NULL) return true; // (can this really happen?)
3515 if (n->is_Proj()) n = n->in(0);
3516 if (n == this) return false; // found a cycle
3517 if (n->is_Con()) return true;
3518 if (n->is_Start()) return true; // params, etc., are OK
3519 if (n->is_Root()) return true; // even better
3520
3521 Node* ctl = n->in(0);
3522 if (ctl != NULL && !ctl->is_top()) {
3523 if (ctl->is_Proj()) ctl = ctl->in(0);
3524 if (ctl == this) return false;
3525
3526 // If we already know that the enclosing memory op is pinned right after
3527 // the init, then any control flow that the store has picked up
3528 // must have preceded the init, or else be equal to the init.
3529 // Even after loop optimizations (which might change control edges)
3530 // a store is never pinned *before* the availability of its inputs.
3531 if (!MemNode::all_controls_dominate(n, this))
3532 return false; // failed to prove a good control
3533 }
3534
3535 // Check data edges for possible dependencies on 'this'.
3536 if ((count += 1) > 20) return false; // complexity limit
3537 for (uint i = 1; i < n->req(); i++) {
3538 Node* m = n->in(i);
3539 if (m == NULL || m == n || m->is_top()) continue;
3540 uint first_i = n->find_edge(m);
3541 if (i != first_i) continue; // process duplicate edge just once
3542 if (!detect_init_independence(m, count)) {
3543 return false;
3544 }
3545 }
3546
3547 return true;
3548 }
3549
3550 // Here are all the checks a Store must pass before it can be moved into
3551 // an initialization. Returns zero if a check fails.
3552 // On success, returns the (constant) offset to which the store applies,
3553 // within the initialized memory.
3554 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3555 const int FAIL = 0;
3556 if (st->req() != MemNode::ValueIn + 1)
3557 return FAIL; // an inscrutable StoreNode (card mark?)
3558 Node* ctl = st->in(MemNode::Control);
3559 if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3560 return FAIL; // must be unconditional after the initialization
3561 Node* mem = st->in(MemNode::Memory);
3562 if (!(mem->is_Proj() && mem->in(0) == this))
3563 return FAIL; // must not be preceded by other stores
3564 Node* adr = st->in(MemNode::Address);
3565 intptr_t offset;
3566 AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3567 if (alloc == NULL)
3568 return FAIL; // inscrutable address
3569 if (alloc != allocation())
3570 return FAIL; // wrong allocation! (store needs to float up)
3571 int size_in_bytes = st->memory_size();
3572 if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3573 return FAIL; // mismatched access
3574 }
3575 Node* val = st->in(MemNode::ValueIn);
3576 int complexity_count = 0;
3577 if (!detect_init_independence(val, complexity_count))
3578 return FAIL; // stored value must be 'simple enough'
3579
3580 // The Store can be captured only if nothing after the allocation
3581 // and before the Store is using the memory location that the store
3582 // overwrites.
3583 bool failed = false;
3584 // If is_complete_with_arraycopy() is true the shape of the graph is
3585 // well defined and is safe so no need for extra checks.
3586 if (!is_complete_with_arraycopy()) {
3587 // We are going to look at each use of the memory state following
3588 // the allocation to make sure nothing reads the memory that the
3589 // Store writes.
3590 const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3591 int alias_idx = phase->C->get_alias_index(t_adr);
3592 ResourceMark rm;
3593 Unique_Node_List mems;
3594 mems.push(mem);
3595 Node* unique_merge = NULL;
3596 for (uint next = 0; next < mems.size(); ++next) {
3597 Node *m = mems.at(next);
3598 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3599 Node *n = m->fast_out(j);
3600 if (n->outcnt() == 0) {
3601 continue;
3602 }
3603 if (n == st) {
3604 continue;
3605 } else if (n->in(0) != NULL && n->in(0) != ctl) {
3606 // If the control of this use is different from the control
3607 // of the Store which is right after the InitializeNode then
3608 // this node cannot be between the InitializeNode and the
3609 // Store.
3610 continue;
3611 } else if (n->is_MergeMem()) {
3612 if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3613 // We can hit a MergeMemNode (that will likely go away
3614 // later) that is a direct use of the memory state
3615 // following the InitializeNode on the same slice as the
3616 // store node that we'd like to capture. We need to check
3617 // the uses of the MergeMemNode.
3618 mems.push(n);
3619 }
3620 } else if (n->is_Mem()) {
3621 Node* other_adr = n->in(MemNode::Address);
3622 if (other_adr == adr) {
3623 failed = true;
3624 break;
3625 } else {
3626 const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3627 if (other_t_adr != NULL) {
3628 int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3629 if (other_alias_idx == alias_idx) {
3630 // A load from the same memory slice as the store right
3631 // after the InitializeNode. We check the control of the
3632 // object/array that is loaded from. If it's the same as
3633 // the store control then we cannot capture the store.
3634 assert(!n->is_Store(), "2 stores to same slice on same control?");
3635 Node* base = other_adr;
3636 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3637 base = base->in(AddPNode::Base);
3638 if (base != NULL) {
3639 base = base->uncast();
3640 if (base->is_Proj() && base->in(0) == alloc) {
3641 failed = true;
3642 break;
3643 }
3644 }
3645 }
3646 }
3647 }
3648 } else {
3649 failed = true;
3650 break;
3651 }
3652 }
3653 }
3654 }
3655 if (failed) {
3656 if (!can_reshape) {
3657 // We decided we couldn't capture the store during parsing. We
3658 // should try again during the next IGVN once the graph is
3659 // cleaner.
3660 phase->C->record_for_igvn(st);
3661 }
3662 return FAIL;
3663 }
3664
3665 return offset; // success
3666 }
3667
3668 // Find the captured store in(i) which corresponds to the range
3669 // [start..start+size) in the initialized object.
3670 // If there is one, return its index i. If there isn't, return the
3671 // negative of the index where it should be inserted.
3672 // Return 0 if the queried range overlaps an initialization boundary
3673 // or if dead code is encountered.
3674 // If size_in_bytes is zero, do not bother with overlap checks.
3675 int InitializeNode::captured_store_insertion_point(intptr_t start,
3676 int size_in_bytes,
3677 PhaseTransform* phase) {
3678 const int FAIL = 0, MAX_STORE = BytesPerLong;
3679
3680 if (is_complete())
3681 return FAIL; // arraycopy got here first; punt
3682
3683 assert(allocation() != NULL, "must be present");
3684
3685 // no negatives, no header fields:
3686 if (start < (intptr_t) allocation()->minimum_header_size()) return FAIL;
3687
3688 // after a certain size, we bail out on tracking all the stores:
3689 intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3690 if (start >= ti_limit) return FAIL;
3691
3692 for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3693 if (i >= limit) return -(int)i; // not found; here is where to put it
3694
3695 Node* st = in(i);
3696 intptr_t st_off = get_store_offset(st, phase);
3697 if (st_off < 0) {
3698 if (st != zero_memory()) {
3699 return FAIL; // bail out if there is dead garbage
3700 }
3701 } else if (st_off > start) {
3702 // ...we are done, since stores are ordered
3703 if (st_off < start + size_in_bytes) {
3704 return FAIL; // the next store overlaps
3705 }
3706 return -(int)i; // not found; here is where to put it
3707 } else if (st_off < start) {
3708 if (size_in_bytes != 0 &&
3709 start < st_off + MAX_STORE &&
3710 start < st_off + st->as_Store()->memory_size()) {
3711 return FAIL; // the previous store overlaps
3712 }
3713 } else {
3714 if (size_in_bytes != 0 &&
3715 st->as_Store()->memory_size() != size_in_bytes) {
3716 return FAIL; // mismatched store size
3717 }
3718 return i;
3719 }
3720
3721 ++i;
3722 }
3723 }
3724
3725 // Look for a captured store which initializes at the offset 'start'
3726 // with the given size. If there is no such store, and no other
3727 // initialization interferes, then return zero_memory (the memory
3728 // projection of the AllocateNode).
3729 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3730 PhaseTransform* phase) {
3731 assert(stores_are_sane(phase), "");
3732 int i = captured_store_insertion_point(start, size_in_bytes, phase);
3733 if (i == 0) {
3734 return NULL; // something is dead
3735 } else if (i < 0) {
3736 return zero_memory(); // just primordial zero bits here
3737 } else {
3738 Node* st = in(i); // here is the store at this position
3739 assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3740 return st;
3741 }
3742 }
3743
3744 // Create, as a raw pointer, an address within my new object at 'offset'.
3745 Node* InitializeNode::make_raw_address(intptr_t offset,
3746 PhaseTransform* phase) {
3747 Node* addr = in(RawAddress);
3748 if (offset != 0) {
3749 Compile* C = phase->C;
3750 addr = phase->transform( new AddPNode(C->top(), addr,
3751 phase->MakeConX(offset)) );
3752 }
3753 return addr;
3754 }
3755
3756 // Clone the given store, converting it into a raw store
3757 // initializing a field or element of my new object.
3758 // Caller is responsible for retiring the original store,
3759 // with subsume_node or the like.
3760 //
3761 // From the example above InitializeNode::InitializeNode,
3762 // here are the old stores to be captured:
3763 // store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3764 // store2 = (StoreC init.Control store1 (+ oop 14) 2)
3765 //
3766 // Here is the changed code; note the extra edges on init:
3767 // alloc = (Allocate ...)
3768 // rawoop = alloc.RawAddress
3769 // rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3770 // rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3771 // init = (Initialize alloc.Control alloc.Memory rawoop
3772 // rawstore1 rawstore2)
3773 //
3774 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3775 PhaseTransform* phase, bool can_reshape) {
3776 assert(stores_are_sane(phase), "");
3777
3778 if (start < 0) return NULL;
3779 assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3780
3781 Compile* C = phase->C;
3782 int size_in_bytes = st->memory_size();
3783 int i = captured_store_insertion_point(start, size_in_bytes, phase);
3784 if (i == 0) return NULL; // bail out
3785 Node* prev_mem = NULL; // raw memory for the captured store
3786 if (i > 0) {
3787 prev_mem = in(i); // there is a pre-existing store under this one
3788 set_req(i, C->top()); // temporarily disconnect it
3789 // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3790 } else {
3791 i = -i; // no pre-existing store
3792 prev_mem = zero_memory(); // a slice of the newly allocated object
3793 if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3794 set_req(--i, C->top()); // reuse this edge; it has been folded away
3795 else
3796 ins_req(i, C->top()); // build a new edge
3797 }
3798 Node* new_st = st->clone();
3799 new_st->set_req(MemNode::Control, in(Control));
3800 new_st->set_req(MemNode::Memory, prev_mem);
3801 new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3802 new_st = phase->transform(new_st);
3803
3804 // At this point, new_st might have swallowed a pre-existing store
3805 // at the same offset, or perhaps new_st might have disappeared,
3806 // if it redundantly stored the same value (or zero to fresh memory).
3807
3808 // In any case, wire it in:
3809 phase->igvn_rehash_node_delayed(this);
3810 set_req(i, new_st);
3811
3812 // The caller may now kill the old guy.
3813 DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3814 assert(check_st == new_st || check_st == NULL, "must be findable");
3815 assert(!is_complete(), "");
3816 return new_st;
3817 }
3818
3819 static bool store_constant(jlong* tiles, int num_tiles,
3820 intptr_t st_off, int st_size,
3821 jlong con) {
3822 if ((st_off & (st_size-1)) != 0)
3823 return false; // strange store offset (assume size==2**N)
3824 address addr = (address)tiles + st_off;
3825 assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3826 switch (st_size) {
3827 case sizeof(jbyte): *(jbyte*) addr = (jbyte) con; break;
3828 case sizeof(jchar): *(jchar*) addr = (jchar) con; break;
3829 case sizeof(jint): *(jint*) addr = (jint) con; break;
3830 case sizeof(jlong): *(jlong*) addr = (jlong) con; break;
3831 default: return false; // strange store size (detect size!=2**N here)
3832 }
3833 return true; // return success to caller
3834 }
3835
3836 // Coalesce subword constants into int constants and possibly
3837 // into long constants. The goal, if the CPU permits,
3838 // is to initialize the object with a small number of 64-bit tiles.
3839 // Also, convert floating-point constants to bit patterns.
3840 // Non-constants are not relevant to this pass.
3841 //
3842 // In terms of the running example on InitializeNode::InitializeNode
3843 // and InitializeNode::capture_store, here is the transformation
3844 // of rawstore1 and rawstore2 into rawstore12:
3845 // alloc = (Allocate ...)
3846 // rawoop = alloc.RawAddress
3847 // tile12 = 0x00010002
3848 // rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3849 // init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3850 //
3851 void
3852 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3853 Node* size_in_bytes,
3854 PhaseGVN* phase) {
3855 Compile* C = phase->C;
3856
3857 assert(stores_are_sane(phase), "");
3858 // Note: After this pass, they are not completely sane,
3859 // since there may be some overlaps.
3860
3861 int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3862
3863 intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3864 intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3865 size_limit = MIN2(size_limit, ti_limit);
3866 size_limit = align_up(size_limit, BytesPerLong);
3867 int num_tiles = size_limit / BytesPerLong;
3868
3869 // allocate space for the tile map:
3870 const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3871 jlong tiles_buf[small_len];
3872 Node* nodes_buf[small_len];
3873 jlong inits_buf[small_len];
3874 jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3875 : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3876 Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3877 : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3878 jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3879 : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3880 // tiles: exact bitwise model of all primitive constants
3881 // nodes: last constant-storing node subsumed into the tiles model
3882 // inits: which bytes (in each tile) are touched by any initializations
3883
3884 //// Pass A: Fill in the tile model with any relevant stores.
3885
3886 Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3887 Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3888 Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3889 Node* zmem = zero_memory(); // initially zero memory state
3890 for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3891 Node* st = in(i);
3892 intptr_t st_off = get_store_offset(st, phase);
3893
3894 // Figure out the store's offset and constant value:
3895 if (st_off < header_size) continue; //skip (ignore header)
3896 if (st->in(MemNode::Memory) != zmem) continue; //skip (odd store chain)
3897 int st_size = st->as_Store()->memory_size();
3898 if (st_off + st_size > size_limit) break;
3899
3900 // Record which bytes are touched, whether by constant or not.
3901 if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3902 continue; // skip (strange store size)
3903
3904 const Type* val = phase->type(st->in(MemNode::ValueIn));
3905 if (!val->singleton()) continue; //skip (non-con store)
3906 BasicType type = val->basic_type();
3907
3908 jlong con = 0;
3909 switch (type) {
3910 case T_INT: con = val->is_int()->get_con(); break;
3911 case T_LONG: con = val->is_long()->get_con(); break;
3912 case T_FLOAT: con = jint_cast(val->getf()); break;
3913 case T_DOUBLE: con = jlong_cast(val->getd()); break;
3914 default: continue; //skip (odd store type)
3915 }
3916
3917 if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3918 st->Opcode() == Op_StoreL) {
3919 continue; // This StoreL is already optimal.
3920 }
3921
3922 // Store down the constant.
3923 store_constant(tiles, num_tiles, st_off, st_size, con);
3924
3925 intptr_t j = st_off >> LogBytesPerLong;
3926
3927 if (type == T_INT && st_size == BytesPerInt
3928 && (st_off & BytesPerInt) == BytesPerInt) {
3929 jlong lcon = tiles[j];
3930 if (!Matcher::isSimpleConstant64(lcon) &&
3931 st->Opcode() == Op_StoreI) {
3932 // This StoreI is already optimal by itself.
3933 jint* intcon = (jint*) &tiles[j];
3934 intcon[1] = 0; // undo the store_constant()
3935
3936 // If the previous store is also optimal by itself, back up and
3937 // undo the action of the previous loop iteration... if we can.
3938 // But if we can't, just let the previous half take care of itself.
3939 st = nodes[j];
3940 st_off -= BytesPerInt;
3941 con = intcon[0];
3942 if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3943 assert(st_off >= header_size, "still ignoring header");
3944 assert(get_store_offset(st, phase) == st_off, "must be");
3945 assert(in(i-1) == zmem, "must be");
3946 DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3947 assert(con == tcon->is_int()->get_con(), "must be");
3948 // Undo the effects of the previous loop trip, which swallowed st:
3949 intcon[0] = 0; // undo store_constant()
3950 set_req(i-1, st); // undo set_req(i, zmem)
3951 nodes[j] = NULL; // undo nodes[j] = st
3952 --old_subword; // undo ++old_subword
3953 }
3954 continue; // This StoreI is already optimal.
3955 }
3956 }
3957
3958 // This store is not needed.
3959 set_req(i, zmem);
3960 nodes[j] = st; // record for the moment
3961 if (st_size < BytesPerLong) // something has changed
3962 ++old_subword; // includes int/float, but who's counting...
3963 else ++old_long;
3964 }
3965
3966 if ((old_subword + old_long) == 0)
3967 return; // nothing more to do
3968
3969 //// Pass B: Convert any non-zero tiles into optimal constant stores.
3970 // Be sure to insert them before overlapping non-constant stores.
3971 // (E.g., byte[] x = { 1,2,y,4 } => x[int 0] = 0x01020004, x[2]=y.)
3972 for (int j = 0; j < num_tiles; j++) {
3973 jlong con = tiles[j];
3974 jlong init = inits[j];
3975 if (con == 0) continue;
3976 jint con0, con1; // split the constant, address-wise
3977 jint init0, init1; // split the init map, address-wise
3978 { union { jlong con; jint intcon[2]; } u;
3979 u.con = con;
3980 con0 = u.intcon[0];
3981 con1 = u.intcon[1];
3982 u.con = init;
3983 init0 = u.intcon[0];
3984 init1 = u.intcon[1];
3985 }
3986
3987 Node* old = nodes[j];
3988 assert(old != NULL, "need the prior store");
3989 intptr_t offset = (j * BytesPerLong);
3990
3991 bool split = !Matcher::isSimpleConstant64(con);
3992
3993 if (offset < header_size) {
3994 assert(offset + BytesPerInt >= header_size, "second int counts");
3995 assert(*(jint*)&tiles[j] == 0, "junk in header");
3996 split = true; // only the second word counts
3997 // Example: int a[] = { 42 ... }
3998 } else if (con0 == 0 && init0 == -1) {
3999 split = true; // first word is covered by full inits
4000 // Example: int a[] = { ... foo(), 42 ... }
4001 } else if (con1 == 0 && init1 == -1) {
4002 split = true; // second word is covered by full inits
4003 // Example: int a[] = { ... 42, foo() ... }
4004 }
4005
4006 // Here's a case where init0 is neither 0 nor -1:
4007 // byte a[] = { ... 0,0,foo(),0, 0,0,0,42 ... }
4008 // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
4009 // In this case the tile is not split; it is (jlong)42.
4010 // The big tile is stored down, and then the foo() value is inserted.
4011 // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
4012
4013 Node* ctl = old->in(MemNode::Control);
4014 Node* adr = make_raw_address(offset, phase);
4015 const TypePtr* atp = TypeRawPtr::BOTTOM;
4016
4017 // One or two coalesced stores to plop down.
4018 Node* st[2];
4019 intptr_t off[2];
4020 int nst = 0;
4021 if (!split) {
4022 ++new_long;
4023 off[nst] = offset;
4024 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4025 phase->longcon(con), T_LONG, MemNode::unordered);
4026 } else {
4027 // Omit either if it is a zero.
4028 if (con0 != 0) {
4029 ++new_int;
4030 off[nst] = offset;
4031 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4032 phase->intcon(con0), T_INT, MemNode::unordered);
4033 }
4034 if (con1 != 0) {
4035 ++new_int;
4036 offset += BytesPerInt;
4037 adr = make_raw_address(offset, phase);
4038 off[nst] = offset;
4039 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4040 phase->intcon(con1), T_INT, MemNode::unordered);
4041 }
4042 }
4043
4044 // Insert second store first, then the first before the second.
4045 // Insert each one just before any overlapping non-constant stores.
4046 while (nst > 0) {
4047 Node* st1 = st[--nst];
4048 C->copy_node_notes_to(st1, old);
4049 st1 = phase->transform(st1);
4050 offset = off[nst];
4051 assert(offset >= header_size, "do not smash header");
4052 int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4053 guarantee(ins_idx != 0, "must re-insert constant store");
4054 if (ins_idx < 0) ins_idx = -ins_idx; // never overlap
4055 if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4056 set_req(--ins_idx, st1);
4057 else
4058 ins_req(ins_idx, st1);
4059 }
4060 }
4061
4062 if (PrintCompilation && WizardMode)
4063 tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4064 old_subword, old_long, new_int, new_long);
4065 if (C->log() != NULL)
4066 C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4067 old_subword, old_long, new_int, new_long);
4068
4069 // Clean up any remaining occurrences of zmem:
4070 remove_extra_zeroes();
4071 }
4072
4073 // Explore forward from in(start) to find the first fully initialized
4074 // word, and return its offset. Skip groups of subword stores which
4075 // together initialize full words. If in(start) is itself part of a
4076 // fully initialized word, return the offset of in(start). If there
4077 // are no following full-word stores, or if something is fishy, return
4078 // a negative value.
4079 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4080 int int_map = 0;
4081 intptr_t int_map_off = 0;
4082 const int FULL_MAP = right_n_bits(BytesPerInt); // the int_map we hope for
4083
4084 for (uint i = start, limit = req(); i < limit; i++) {
4085 Node* st = in(i);
4086
4087 intptr_t st_off = get_store_offset(st, phase);
4088 if (st_off < 0) break; // return conservative answer
4089
4090 int st_size = st->as_Store()->memory_size();
4091 if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4092 return st_off; // we found a complete word init
4093 }
4094
4095 // update the map:
4096
4097 intptr_t this_int_off = align_down(st_off, BytesPerInt);
4098 if (this_int_off != int_map_off) {
4099 // reset the map:
4100 int_map = 0;
4101 int_map_off = this_int_off;
4102 }
4103
4104 int subword_off = st_off - this_int_off;
4105 int_map |= right_n_bits(st_size) << subword_off;
4106 if ((int_map & FULL_MAP) == FULL_MAP) {
4107 return this_int_off; // we found a complete word init
4108 }
4109
4110 // Did this store hit or cross the word boundary?
4111 intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4112 if (next_int_off == this_int_off + BytesPerInt) {
4113 // We passed the current int, without fully initializing it.
4114 int_map_off = next_int_off;
4115 int_map >>= BytesPerInt;
4116 } else if (next_int_off > this_int_off + BytesPerInt) {
4117 // We passed the current and next int.
4118 return this_int_off + BytesPerInt;
4119 }
4120 }
4121
4122 return -1;
4123 }
4124
4125
4126 // Called when the associated AllocateNode is expanded into CFG.
4127 // At this point, we may perform additional optimizations.
4128 // Linearize the stores by ascending offset, to make memory
4129 // activity as coherent as possible.
4130 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4131 intptr_t header_size,
4132 Node* size_in_bytes,
4133 PhaseGVN* phase) {
4134 assert(!is_complete(), "not already complete");
4135 assert(stores_are_sane(phase), "");
4136 assert(allocation() != NULL, "must be present");
4137
4138 remove_extra_zeroes();
4139
4140 if (ReduceFieldZeroing || ReduceBulkZeroing)
4141 // reduce instruction count for common initialization patterns
4142 coalesce_subword_stores(header_size, size_in_bytes, phase);
4143
4144 Node* zmem = zero_memory(); // initially zero memory state
4145 Node* inits = zmem; // accumulating a linearized chain of inits
4146 #ifdef ASSERT
4147 intptr_t first_offset = allocation()->minimum_header_size();
4148 intptr_t last_init_off = first_offset; // previous init offset
4149 intptr_t last_init_end = first_offset; // previous init offset+size
4150 intptr_t last_tile_end = first_offset; // previous tile offset+size
4151 #endif
4152 intptr_t zeroes_done = header_size;
4153
4154 bool do_zeroing = true; // we might give up if inits are very sparse
4155 int big_init_gaps = 0; // how many large gaps have we seen?
4156
4157 if (UseTLAB && ZeroTLAB) do_zeroing = false;
4158 if (!ReduceFieldZeroing && !ReduceBulkZeroing) do_zeroing = false;
4159
4160 for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4161 Node* st = in(i);
4162 intptr_t st_off = get_store_offset(st, phase);
4163 if (st_off < 0)
4164 break; // unknown junk in the inits
4165 if (st->in(MemNode::Memory) != zmem)
4166 break; // complicated store chains somehow in list
4167
4168 int st_size = st->as_Store()->memory_size();
4169 intptr_t next_init_off = st_off + st_size;
4170
4171 if (do_zeroing && zeroes_done < next_init_off) {
4172 // See if this store needs a zero before it or under it.
4173 intptr_t zeroes_needed = st_off;
4174
4175 if (st_size < BytesPerInt) {
4176 // Look for subword stores which only partially initialize words.
4177 // If we find some, we must lay down some word-level zeroes first,
4178 // underneath the subword stores.
4179 //
4180 // Examples:
4181 // byte[] a = { p,q,r,s } => a[0]=p,a[1]=q,a[2]=r,a[3]=s
4182 // byte[] a = { x,y,0,0 } => a[0..3] = 0, a[0]=x,a[1]=y
4183 // byte[] a = { 0,0,z,0 } => a[0..3] = 0, a[2]=z
4184 //
4185 // Note: coalesce_subword_stores may have already done this,
4186 // if it was prompted by constant non-zero subword initializers.
4187 // But this case can still arise with non-constant stores.
4188
4189 intptr_t next_full_store = find_next_fullword_store(i, phase);
4190
4191 // In the examples above:
4192 // in(i) p q r s x y z
4193 // st_off 12 13 14 15 12 13 14
4194 // st_size 1 1 1 1 1 1 1
4195 // next_full_s. 12 16 16 16 16 16 16
4196 // z's_done 12 16 16 16 12 16 12
4197 // z's_needed 12 16 16 16 16 16 16
4198 // zsize 0 0 0 0 4 0 4
4199 if (next_full_store < 0) {
4200 // Conservative tack: Zero to end of current word.
4201 zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4202 } else {
4203 // Zero to beginning of next fully initialized word.
4204 // Or, don't zero at all, if we are already in that word.
4205 assert(next_full_store >= zeroes_needed, "must go forward");
4206 assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4207 zeroes_needed = next_full_store;
4208 }
4209 }
4210
4211 if (zeroes_needed > zeroes_done) {
4212 intptr_t zsize = zeroes_needed - zeroes_done;
4213 // Do some incremental zeroing on rawmem, in parallel with inits.
4214 zeroes_done = align_down(zeroes_done, BytesPerInt);
4215 rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4216 zeroes_done, zeroes_needed,
4217 phase);
4218 zeroes_done = zeroes_needed;
4219 if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4220 do_zeroing = false; // leave the hole, next time
4221 }
4222 }
4223
4224 // Collect the store and move on:
4225 st->set_req(MemNode::Memory, inits);
4226 inits = st; // put it on the linearized chain
4227 set_req(i, zmem); // unhook from previous position
4228
4229 if (zeroes_done == st_off)
4230 zeroes_done = next_init_off;
4231
4232 assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4233
4234 #ifdef ASSERT
4235 // Various order invariants. Weaker than stores_are_sane because
4236 // a large constant tile can be filled in by smaller non-constant stores.
4237 assert(st_off >= last_init_off, "inits do not reverse");
4238 last_init_off = st_off;
4239 const Type* val = NULL;
4240 if (st_size >= BytesPerInt &&
4241 (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4242 (int)val->basic_type() < (int)T_OBJECT) {
4243 assert(st_off >= last_tile_end, "tiles do not overlap");
4244 assert(st_off >= last_init_end, "tiles do not overwrite inits");
4245 last_tile_end = MAX2(last_tile_end, next_init_off);
4246 } else {
4247 intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4248 assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4249 assert(st_off >= last_init_end, "inits do not overlap");
4250 last_init_end = next_init_off; // it's a non-tile
4251 }
4252 #endif //ASSERT
4253 }
4254
4255 remove_extra_zeroes(); // clear out all the zmems left over
4256 add_req(inits);
4257
4258 if (!(UseTLAB && ZeroTLAB)) {
4259 // If anything remains to be zeroed, zero it all now.
4260 zeroes_done = align_down(zeroes_done, BytesPerInt);
4261 // if it is the last unused 4 bytes of an instance, forget about it
4262 intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4263 if (zeroes_done + BytesPerLong >= size_limit) {
4264 AllocateNode* alloc = allocation();
4265 assert(alloc != NULL, "must be present");
4266 if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
4267 Node* klass_node = alloc->in(AllocateNode::KlassNode);
4268 ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
4269 if (zeroes_done == k->layout_helper())
4270 zeroes_done = size_limit;
4271 }
4272 }
4273 if (zeroes_done < size_limit) {
4274 rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4275 zeroes_done, size_in_bytes, phase);
4276 }
4277 }
4278
4279 set_complete(phase);
4280 return rawmem;
4281 }
4282
4283
4284 #ifdef ASSERT
4285 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
4286 if (is_complete())
4287 return true; // stores could be anything at this point
4288 assert(allocation() != NULL, "must be present");
4289 intptr_t last_off = allocation()->minimum_header_size();
4290 for (uint i = InitializeNode::RawStores; i < req(); i++) {
4291 Node* st = in(i);
4292 intptr_t st_off = get_store_offset(st, phase);
4293 if (st_off < 0) continue; // ignore dead garbage
4294 if (last_off > st_off) {
4295 tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4296 this->dump(2);
4297 assert(false, "ascending store offsets");
4298 return false;
4299 }
4300 last_off = st_off + st->as_Store()->memory_size();
4301 }
4302 return true;
4303 }
4304 #endif //ASSERT
4305
4306
4307
4308
4309 //============================MergeMemNode=====================================
4310 //
4311 // SEMANTICS OF MEMORY MERGES: A MergeMem is a memory state assembled from several
4312 // contributing store or call operations. Each contributor provides the memory
4313 // state for a particular "alias type" (see Compile::alias_type). For example,
4314 // if a MergeMem has an input X for alias category #6, then any memory reference
4315 // to alias category #6 may use X as its memory state input, as an exact equivalent
4316 // to using the MergeMem as a whole.
4317 // Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4318 //
4319 // (Here, the <N> notation gives the index of the relevant adr_type.)
4320 //
4321 // In one special case (and more cases in the future), alias categories overlap.
4322 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4323 // states. Therefore, if a MergeMem has only one contributing input W for Bot,
4324 // it is exactly equivalent to that state W:
4325 // MergeMem(<Bot>: W) <==> W
4326 //
4327 // Usually, the merge has more than one input. In that case, where inputs
4328 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4329 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4330 // Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4331 // Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4332 //
4333 // A merge can take a "wide" memory state as one of its narrow inputs.
4334 // This simply means that the merge observes out only the relevant parts of
4335 // the wide input. That is, wide memory states arriving at narrow merge inputs
4336 // are implicitly "filtered" or "sliced" as necessary. (This is rare.)
4337 //
4338 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4339 // and that memory slices "leak through":
4340 // MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4341 //
4342 // But, in such a cascade, repeated memory slices can "block the leak":
4343 // MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4344 //
4345 // In the last example, Y is not part of the combined memory state of the
4346 // outermost MergeMem. The system must, of course, prevent unschedulable
4347 // memory states from arising, so you can be sure that the state Y is somehow
4348 // a precursor to state Y'.
4349 //
4350 //
4351 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4352 // of each MergeMemNode array are exactly the numerical alias indexes, including
4353 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw. The functions
4354 // Compile::alias_type (and kin) produce and manage these indexes.
4355 //
4356 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4357 // (Note that this provides quick access to the top node inside MergeMem methods,
4358 // without the need to reach out via TLS to Compile::current.)
4359 //
4360 // As a consequence of what was just described, a MergeMem that represents a full
4361 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4362 // containing all alias categories.
4363 //
4364 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4365 //
4366 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4367 // a memory state for the alias type <N>, or else the top node, meaning that
4368 // there is no particular input for that alias type. Note that the length of
4369 // a MergeMem is variable, and may be extended at any time to accommodate new
4370 // memory states at larger alias indexes. When merges grow, they are of course
4371 // filled with "top" in the unused in() positions.
4372 //
4373 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4374 // (Top was chosen because it works smoothly with passes like GCM.)
4375 //
4376 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM. (It is
4377 // the type of random VM bits like TLS references.) Since it is always the
4378 // first non-Bot memory slice, some low-level loops use it to initialize an
4379 // index variable: for (i = AliasIdxRaw; i < req(); i++).
4380 //
4381 //
4382 // ACCESSORS: There is a special accessor MergeMemNode::base_memory which returns
4383 // the distinguished "wide" state. The accessor MergeMemNode::memory_at(N) returns
4384 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4385 // it returns the base memory. To prevent bugs, memory_at does not accept <Top>
4386 // or <Bot> indexes. The iterator MergeMemStream provides robust iteration over
4387 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4388 //
4389 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4390 // really that different from the other memory inputs. An abbreviation called
4391 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4392 //
4393 //
4394 // PARTIAL MEMORY STATES: During optimization, MergeMem nodes may arise that represent
4395 // partial memory states. When a Phi splits through a MergeMem, the copy of the Phi
4396 // that "emerges though" the base memory will be marked as excluding the alias types
4397 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4398 //
4399 // Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4400 // ==Ideal=> MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4401 //
4402 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4403 // (It is currently unimplemented.) As you can see, the resulting merge is
4404 // actually a disjoint union of memory states, rather than an overlay.
4405 //
4406
4407 //------------------------------MergeMemNode-----------------------------------
4408 Node* MergeMemNode::make_empty_memory() {
4409 Node* empty_memory = (Node*) Compile::current()->top();
4410 assert(empty_memory->is_top(), "correct sentinel identity");
4411 return empty_memory;
4412 }
4413
4414 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4415 init_class_id(Class_MergeMem);
4416 // all inputs are nullified in Node::Node(int)
4417 // set_input(0, NULL); // no control input
4418
4419 // Initialize the edges uniformly to top, for starters.
4420 Node* empty_mem = make_empty_memory();
4421 for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4422 init_req(i,empty_mem);
4423 }
4424 assert(empty_memory() == empty_mem, "");
4425
4426 if( new_base != NULL && new_base->is_MergeMem() ) {
4427 MergeMemNode* mdef = new_base->as_MergeMem();
4428 assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4429 for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4430 mms.set_memory(mms.memory2());
4431 }
4432 assert(base_memory() == mdef->base_memory(), "");
4433 } else {
4434 set_base_memory(new_base);
4435 }
4436 }
4437
4438 // Make a new, untransformed MergeMem with the same base as 'mem'.
4439 // If mem is itself a MergeMem, populate the result with the same edges.
4440 MergeMemNode* MergeMemNode::make(Node* mem) {
4441 return new MergeMemNode(mem);
4442 }
4443
4444 //------------------------------cmp--------------------------------------------
4445 uint MergeMemNode::hash() const { return NO_HASH; }
4446 bool MergeMemNode::cmp( const Node &n ) const {
4447 return (&n == this); // Always fail except on self
4448 }
4449
4450 //------------------------------Identity---------------------------------------
4451 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4452 // Identity if this merge point does not record any interesting memory
4453 // disambiguations.
4454 Node* base_mem = base_memory();
4455 Node* empty_mem = empty_memory();
4456 if (base_mem != empty_mem) { // Memory path is not dead?
4457 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4458 Node* mem = in(i);
4459 if (mem != empty_mem && mem != base_mem) {
4460 return this; // Many memory splits; no change
4461 }
4462 }
4463 }
4464 return base_mem; // No memory splits; ID on the one true input
4465 }
4466
4467 //------------------------------Ideal------------------------------------------
4468 // This method is invoked recursively on chains of MergeMem nodes
4469 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4470 // Remove chain'd MergeMems
4471 //
4472 // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4473 // relative to the "in(Bot)". Since we are patching both at the same time,
4474 // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4475 // but rewrite each "in(i)" relative to the new "in(Bot)".
4476 Node *progress = NULL;
4477
4478
4479 Node* old_base = base_memory();
4480 Node* empty_mem = empty_memory();
4481 if (old_base == empty_mem)
4482 return NULL; // Dead memory path.
4483
4484 MergeMemNode* old_mbase;
4485 if (old_base != NULL && old_base->is_MergeMem())
4486 old_mbase = old_base->as_MergeMem();
4487 else
4488 old_mbase = NULL;
4489 Node* new_base = old_base;
4490
4491 // simplify stacked MergeMems in base memory
4492 if (old_mbase) new_base = old_mbase->base_memory();
4493
4494 // the base memory might contribute new slices beyond my req()
4495 if (old_mbase) grow_to_match(old_mbase);
4496
4497 // Look carefully at the base node if it is a phi.
4498 PhiNode* phi_base;
4499 if (new_base != NULL && new_base->is_Phi())
4500 phi_base = new_base->as_Phi();
4501 else
4502 phi_base = NULL;
4503
4504 Node* phi_reg = NULL;
4505 uint phi_len = (uint)-1;
4506 if (phi_base != NULL && !phi_base->is_copy()) {
4507 // do not examine phi if degraded to a copy
4508 phi_reg = phi_base->region();
4509 phi_len = phi_base->req();
4510 // see if the phi is unfinished
4511 for (uint i = 1; i < phi_len; i++) {
4512 if (phi_base->in(i) == NULL) {
4513 // incomplete phi; do not look at it yet!
4514 phi_reg = NULL;
4515 phi_len = (uint)-1;
4516 break;
4517 }
4518 }
4519 }
4520
4521 // Note: We do not call verify_sparse on entry, because inputs
4522 // can normalize to the base_memory via subsume_node or similar
4523 // mechanisms. This method repairs that damage.
4524
4525 assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4526
4527 // Look at each slice.
4528 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4529 Node* old_in = in(i);
4530 // calculate the old memory value
4531 Node* old_mem = old_in;
4532 if (old_mem == empty_mem) old_mem = old_base;
4533 assert(old_mem == memory_at(i), "");
4534
4535 // maybe update (reslice) the old memory value
4536
4537 // simplify stacked MergeMems
4538 Node* new_mem = old_mem;
4539 MergeMemNode* old_mmem;
4540 if (old_mem != NULL && old_mem->is_MergeMem())
4541 old_mmem = old_mem->as_MergeMem();
4542 else
4543 old_mmem = NULL;
4544 if (old_mmem == this) {
4545 // This can happen if loops break up and safepoints disappear.
4546 // A merge of BotPtr (default) with a RawPtr memory derived from a
4547 // safepoint can be rewritten to a merge of the same BotPtr with
4548 // the BotPtr phi coming into the loop. If that phi disappears
4549 // also, we can end up with a self-loop of the mergemem.
4550 // In general, if loops degenerate and memory effects disappear,
4551 // a mergemem can be left looking at itself. This simply means
4552 // that the mergemem's default should be used, since there is
4553 // no longer any apparent effect on this slice.
4554 // Note: If a memory slice is a MergeMem cycle, it is unreachable
4555 // from start. Update the input to TOP.
4556 new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4557 }
4558 else if (old_mmem != NULL) {
4559 new_mem = old_mmem->memory_at(i);
4560 }
4561 // else preceding memory was not a MergeMem
4562
4563 // replace equivalent phis (unfortunately, they do not GVN together)
4564 if (new_mem != NULL && new_mem != new_base &&
4565 new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4566 if (new_mem->is_Phi()) {
4567 PhiNode* phi_mem = new_mem->as_Phi();
4568 for (uint i = 1; i < phi_len; i++) {
4569 if (phi_base->in(i) != phi_mem->in(i)) {
4570 phi_mem = NULL;
4571 break;
4572 }
4573 }
4574 if (phi_mem != NULL) {
4575 // equivalent phi nodes; revert to the def
4576 new_mem = new_base;
4577 }
4578 }
4579 }
4580
4581 // maybe store down a new value
4582 Node* new_in = new_mem;
4583 if (new_in == new_base) new_in = empty_mem;
4584
4585 if (new_in != old_in) {
4586 // Warning: Do not combine this "if" with the previous "if"
4587 // A memory slice might have be be rewritten even if it is semantically
4588 // unchanged, if the base_memory value has changed.
4589 set_req(i, new_in);
4590 progress = this; // Report progress
4591 }
4592 }
4593
4594 if (new_base != old_base) {
4595 set_req(Compile::AliasIdxBot, new_base);
4596 // Don't use set_base_memory(new_base), because we need to update du.
4597 assert(base_memory() == new_base, "");
4598 progress = this;
4599 }
4600
4601 if( base_memory() == this ) {
4602 // a self cycle indicates this memory path is dead
4603 set_req(Compile::AliasIdxBot, empty_mem);
4604 }
4605
4606 // Resolve external cycles by calling Ideal on a MergeMem base_memory
4607 // Recursion must occur after the self cycle check above
4608 if( base_memory()->is_MergeMem() ) {
4609 MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4610 Node *m = phase->transform(new_mbase); // Rollup any cycles
4611 if( m != NULL &&
4612 (m->is_top() ||
4613 (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4614 // propagate rollup of dead cycle to self
4615 set_req(Compile::AliasIdxBot, empty_mem);
4616 }
4617 }
4618
4619 if( base_memory() == empty_mem ) {
4620 progress = this;
4621 // Cut inputs during Parse phase only.
4622 // During Optimize phase a dead MergeMem node will be subsumed by Top.
4623 if( !can_reshape ) {
4624 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4625 if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4626 }
4627 }
4628 }
4629
4630 if( !progress && base_memory()->is_Phi() && can_reshape ) {
4631 // Check if PhiNode::Ideal's "Split phis through memory merges"
4632 // transform should be attempted. Look for this->phi->this cycle.
4633 uint merge_width = req();
4634 if (merge_width > Compile::AliasIdxRaw) {
4635 PhiNode* phi = base_memory()->as_Phi();
4636 for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4637 if (phi->in(i) == this) {
4638 phase->is_IterGVN()->_worklist.push(phi);
4639 break;
4640 }
4641 }
4642 }
4643 }
4644
4645 assert(progress || verify_sparse(), "please, no dups of base");
4646 return progress;
4647 }
4648
4649 //-------------------------set_base_memory-------------------------------------
4650 void MergeMemNode::set_base_memory(Node *new_base) {
4651 Node* empty_mem = empty_memory();
4652 set_req(Compile::AliasIdxBot, new_base);
4653 assert(memory_at(req()) == new_base, "must set default memory");
4654 // Clear out other occurrences of new_base:
4655 if (new_base != empty_mem) {
4656 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4657 if (in(i) == new_base) set_req(i, empty_mem);
4658 }
4659 }
4660 }
4661
4662 //------------------------------out_RegMask------------------------------------
4663 const RegMask &MergeMemNode::out_RegMask() const {
4664 return RegMask::Empty;
4665 }
4666
4667 //------------------------------dump_spec--------------------------------------
4668 #ifndef PRODUCT
4669 void MergeMemNode::dump_spec(outputStream *st) const {
4670 st->print(" {");
4671 Node* base_mem = base_memory();
4672 for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4673 Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4674 if (mem == base_mem) { st->print(" -"); continue; }
4675 st->print( " N%d:", mem->_idx );
4676 Compile::current()->get_adr_type(i)->dump_on(st);
4677 }
4678 st->print(" }");
4679 }
4680 #endif // !PRODUCT
4681
4682
4683 #ifdef ASSERT
4684 static bool might_be_same(Node* a, Node* b) {
4685 if (a == b) return true;
4686 if (!(a->is_Phi() || b->is_Phi())) return false;
4687 // phis shift around during optimization
4688 return true; // pretty stupid...
4689 }
4690
4691 // verify a narrow slice (either incoming or outgoing)
4692 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4693 if (!VerifyAliases) return; // don't bother to verify unless requested
4694 if (VMError::is_error_reported()) return; // muzzle asserts when debugging an error
4695 if (Node::in_dump()) return; // muzzle asserts when printing
4696 assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4697 assert(n != NULL, "");
4698 // Elide intervening MergeMem's
4699 while (n->is_MergeMem()) {
4700 n = n->as_MergeMem()->memory_at(alias_idx);
4701 }
4702 Compile* C = Compile::current();
4703 const TypePtr* n_adr_type = n->adr_type();
4704 if (n == m->empty_memory()) {
4705 // Implicit copy of base_memory()
4706 } else if (n_adr_type != TypePtr::BOTTOM) {
4707 assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4708 assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4709 } else {
4710 // A few places like make_runtime_call "know" that VM calls are narrow,
4711 // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4712 bool expected_wide_mem = false;
4713 if (n == m->base_memory()) {
4714 expected_wide_mem = true;
4715 } else if (alias_idx == Compile::AliasIdxRaw ||
4716 n == m->memory_at(Compile::AliasIdxRaw)) {
4717 expected_wide_mem = true;
4718 } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4719 // memory can "leak through" calls on channels that
4720 // are write-once. Allow this also.
4721 expected_wide_mem = true;
4722 }
4723 assert(expected_wide_mem, "expected narrow slice replacement");
4724 }
4725 }
4726 #else // !ASSERT
4727 #define verify_memory_slice(m,i,n) (void)(0) // PRODUCT version is no-op
4728 #endif
4729
4730
4731 //-----------------------------memory_at---------------------------------------
4732 Node* MergeMemNode::memory_at(uint alias_idx) const {
4733 assert(alias_idx >= Compile::AliasIdxRaw ||
4734 alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4735 "must avoid base_memory and AliasIdxTop");
4736
4737 // Otherwise, it is a narrow slice.
4738 Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4739 Compile *C = Compile::current();
4740 if (is_empty_memory(n)) {
4741 // the array is sparse; empty slots are the "top" node
4742 n = base_memory();
4743 assert(Node::in_dump()
4744 || n == NULL || n->bottom_type() == Type::TOP
4745 || n->adr_type() == NULL // address is TOP
4746 || n->adr_type() == TypePtr::BOTTOM
4747 || n->adr_type() == TypeRawPtr::BOTTOM
4748 || Compile::current()->AliasLevel() == 0,
4749 "must be a wide memory");
4750 // AliasLevel == 0 if we are organizing the memory states manually.
4751 // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4752 } else {
4753 // make sure the stored slice is sane
4754 #ifdef ASSERT
4755 if (VMError::is_error_reported() || Node::in_dump()) {
4756 } else if (might_be_same(n, base_memory())) {
4757 // Give it a pass: It is a mostly harmless repetition of the base.
4758 // This can arise normally from node subsumption during optimization.
4759 } else {
4760 verify_memory_slice(this, alias_idx, n);
4761 }
4762 #endif
4763 }
4764 return n;
4765 }
4766
4767 //---------------------------set_memory_at-------------------------------------
4768 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4769 verify_memory_slice(this, alias_idx, n);
4770 Node* empty_mem = empty_memory();
4771 if (n == base_memory()) n = empty_mem; // collapse default
4772 uint need_req = alias_idx+1;
4773 if (req() < need_req) {
4774 if (n == empty_mem) return; // already the default, so do not grow me
4775 // grow the sparse array
4776 do {
4777 add_req(empty_mem);
4778 } while (req() < need_req);
4779 }
4780 set_req( alias_idx, n );
4781 }
4782
4783
4784
4785 //--------------------------iteration_setup------------------------------------
4786 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4787 if (other != NULL) {
4788 grow_to_match(other);
4789 // invariant: the finite support of mm2 is within mm->req()
4790 #ifdef ASSERT
4791 for (uint i = req(); i < other->req(); i++) {
4792 assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4793 }
4794 #endif
4795 }
4796 // Replace spurious copies of base_memory by top.
4797 Node* base_mem = base_memory();
4798 if (base_mem != NULL && !base_mem->is_top()) {
4799 for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4800 if (in(i) == base_mem)
4801 set_req(i, empty_memory());
4802 }
4803 }
4804 }
4805
4806 //---------------------------grow_to_match-------------------------------------
4807 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4808 Node* empty_mem = empty_memory();
4809 assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4810 // look for the finite support of the other memory
4811 for (uint i = other->req(); --i >= req(); ) {
4812 if (other->in(i) != empty_mem) {
4813 uint new_len = i+1;
4814 while (req() < new_len) add_req(empty_mem);
4815 break;
4816 }
4817 }
4818 }
4819
4820 //---------------------------verify_sparse-------------------------------------
4821 #ifndef PRODUCT
4822 bool MergeMemNode::verify_sparse() const {
4823 assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4824 Node* base_mem = base_memory();
4825 // The following can happen in degenerate cases, since empty==top.
4826 if (is_empty_memory(base_mem)) return true;
4827 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4828 assert(in(i) != NULL, "sane slice");
4829 if (in(i) == base_mem) return false; // should have been the sentinel value!
4830 }
4831 return true;
4832 }
4833
4834 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4835 Node* n;
4836 n = mm->in(idx);
4837 if (mem == n) return true; // might be empty_memory()
4838 n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4839 if (mem == n) return true;
4840 while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4841 if (mem == n) return true;
4842 if (n == NULL) break;
4843 }
4844 return false;
4845 }
4846 #endif // !PRODUCT