1 /*
2 * Copyright 1997-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // Portions of code courtesy of Clifford Click
26
27 // Optimization - Graph Style
28
29 #include "incls/_precompiled.incl"
30 #include "incls/_memnode.cpp.incl"
31
32 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
33
34 //=============================================================================
35 uint MemNode::size_of() const { return sizeof(*this); }
36
37 const TypePtr *MemNode::adr_type() const {
38 Node* adr = in(Address);
39 const TypePtr* cross_check = NULL;
40 DEBUG_ONLY(cross_check = _adr_type);
41 return calculate_adr_type(adr->bottom_type(), cross_check);
42 }
43
44 #ifndef PRODUCT
45 void MemNode::dump_spec(outputStream *st) const {
46 if (in(Address) == NULL) return; // node is dead
47 #ifndef ASSERT
48 // fake the missing field
49 const TypePtr* _adr_type = NULL;
50 if (in(Address) != NULL)
51 _adr_type = in(Address)->bottom_type()->isa_ptr();
52 #endif
53 dump_adr_type(this, _adr_type, st);
54
55 Compile* C = Compile::current();
56 if( C->alias_type(_adr_type)->is_volatile() )
57 st->print(" Volatile!");
58 }
59
60 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
61 st->print(" @");
62 if (adr_type == NULL) {
63 st->print("NULL");
64 } else {
65 adr_type->dump_on(st);
66 Compile* C = Compile::current();
67 Compile::AliasType* atp = NULL;
68 if (C->have_alias_type(adr_type)) atp = C->alias_type(adr_type);
69 if (atp == NULL)
70 st->print(", idx=?\?;");
71 else if (atp->index() == Compile::AliasIdxBot)
72 st->print(", idx=Bot;");
73 else if (atp->index() == Compile::AliasIdxTop)
74 st->print(", idx=Top;");
75 else if (atp->index() == Compile::AliasIdxRaw)
76 st->print(", idx=Raw;");
77 else {
78 ciField* field = atp->field();
79 if (field) {
80 st->print(", name=");
81 field->print_name_on(st);
82 }
83 st->print(", idx=%d;", atp->index());
84 }
85 }
86 }
87
88 extern void print_alias_types();
89
90 #endif
91
92 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
93 const TypeOopPtr *tinst = t_adr->isa_oopptr();
94 if (tinst == NULL || !tinst->is_known_instance_field())
95 return mchain; // don't try to optimize non-instance types
96 uint instance_id = tinst->instance_id();
97 Node *start_mem = phase->C->start()->proj_out(TypeFunc::Memory);
98 Node *prev = NULL;
99 Node *result = mchain;
100 while (prev != result) {
101 prev = result;
102 if (result == start_mem)
103 break; // hit one of our sentinels
104 // skip over a call which does not affect this memory slice
105 if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
106 Node *proj_in = result->in(0);
107 if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
108 break; // hit one of our sentinels
109 } else if (proj_in->is_Call()) {
110 CallNode *call = proj_in->as_Call();
111 if (!call->may_modify(t_adr, phase)) {
112 result = call->in(TypeFunc::Memory);
113 }
114 } else if (proj_in->is_Initialize()) {
115 AllocateNode* alloc = proj_in->as_Initialize()->allocation();
116 // Stop if this is the initialization for the object instance which
117 // which contains this memory slice, otherwise skip over it.
118 if (alloc != NULL && alloc->_idx != instance_id) {
119 result = proj_in->in(TypeFunc::Memory);
120 }
121 } else if (proj_in->is_MemBar()) {
122 result = proj_in->in(TypeFunc::Memory);
123 } else {
124 assert(false, "unexpected projection");
125 }
126 } else if (result->is_MergeMem()) {
127 result = step_through_mergemem(phase, result->as_MergeMem(), t_adr, NULL, tty);
128 }
129 }
130 return result;
131 }
132
133 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
134 const TypeOopPtr *t_oop = t_adr->isa_oopptr();
135 bool is_instance = (t_oop != NULL) && t_oop->is_known_instance_field();
136 PhaseIterGVN *igvn = phase->is_IterGVN();
137 Node *result = mchain;
138 result = optimize_simple_memory_chain(result, t_adr, phase);
139 if (is_instance && igvn != NULL && result->is_Phi()) {
140 PhiNode *mphi = result->as_Phi();
141 assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
142 const TypePtr *t = mphi->adr_type();
143 if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
144 t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
145 t->is_oopptr()->cast_to_exactness(true)
146 ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
147 ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop) {
148 // clone the Phi with our address type
149 result = mphi->split_out_instance(t_adr, igvn);
150 } else {
151 assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
152 }
153 }
154 return result;
155 }
156
157 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
158 uint alias_idx = phase->C->get_alias_index(tp);
159 Node *mem = mmem;
160 #ifdef ASSERT
161 {
162 // Check that current type is consistent with the alias index used during graph construction
163 assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
164 bool consistent = adr_check == NULL || adr_check->empty() ||
165 phase->C->must_alias(adr_check, alias_idx );
166 // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
167 if( !consistent && adr_check != NULL && !adr_check->empty() &&
168 tp->isa_aryptr() && tp->offset() == Type::OffsetBot &&
169 adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
170 ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
171 adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
172 adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
173 // don't assert if it is dead code.
174 consistent = true;
175 }
176 if( !consistent ) {
177 st->print("alias_idx==%d, adr_check==", alias_idx);
178 if( adr_check == NULL ) {
179 st->print("NULL");
180 } else {
181 adr_check->dump();
182 }
183 st->cr();
184 print_alias_types();
185 assert(consistent, "adr_check must match alias idx");
186 }
187 }
188 #endif
189 // TypeInstPtr::NOTNULL+any is an OOP with unknown offset - generally
190 // means an array I have not precisely typed yet. Do not do any
191 // alias stuff with it any time soon.
192 const TypeOopPtr *tinst = tp->isa_oopptr();
193 if( tp->base() != Type::AnyPtr &&
194 !(tinst &&
195 tinst->klass()->is_java_lang_Object() &&
196 tinst->offset() == Type::OffsetBot) ) {
197 // compress paths and change unreachable cycles to TOP
198 // If not, we can update the input infinitely along a MergeMem cycle
199 // Equivalent code in PhiNode::Ideal
200 Node* m = phase->transform(mmem);
201 // If transformed to a MergeMem, get the desired slice
202 // Otherwise the returned node represents memory for every slice
203 mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
204 // Update input if it is progress over what we have now
205 }
206 return mem;
207 }
208
209 //--------------------------Ideal_common---------------------------------------
210 // Look for degenerate control and memory inputs. Bypass MergeMem inputs.
211 // Unhook non-raw memories from complete (macro-expanded) initializations.
212 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
213 // If our control input is a dead region, kill all below the region
214 Node *ctl = in(MemNode::Control);
215 if (ctl && remove_dead_region(phase, can_reshape))
216 return this;
217 ctl = in(MemNode::Control);
218 // Don't bother trying to transform a dead node
219 if( ctl && ctl->is_top() ) return NodeSentinel;
220
221 PhaseIterGVN *igvn = phase->is_IterGVN();
222 // Wait if control on the worklist.
223 if (ctl && can_reshape && igvn != NULL) {
224 Node* bol = NULL;
225 Node* cmp = NULL;
226 if (ctl->in(0)->is_If()) {
227 assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
228 bol = ctl->in(0)->in(1);
229 if (bol->is_Bool())
230 cmp = ctl->in(0)->in(1)->in(1);
231 }
232 if (igvn->_worklist.member(ctl) ||
233 (bol != NULL && igvn->_worklist.member(bol)) ||
234 (cmp != NULL && igvn->_worklist.member(cmp)) ) {
235 // This control path may be dead.
236 // Delay this memory node transformation until the control is processed.
237 phase->is_IterGVN()->_worklist.push(this);
238 return NodeSentinel; // caller will return NULL
239 }
240 }
241 // Ignore if memory is dead, or self-loop
242 Node *mem = in(MemNode::Memory);
243 if( phase->type( mem ) == Type::TOP ) return NodeSentinel; // caller will return NULL
244 assert( mem != this, "dead loop in MemNode::Ideal" );
245
246 Node *address = in(MemNode::Address);
247 const Type *t_adr = phase->type( address );
248 if( t_adr == Type::TOP ) return NodeSentinel; // caller will return NULL
249
250 if( can_reshape && igvn != NULL &&
251 (igvn->_worklist.member(address) || phase->type(address) != adr_type()) ) {
252 // The address's base and type may change when the address is processed.
253 // Delay this mem node transformation until the address is processed.
254 phase->is_IterGVN()->_worklist.push(this);
255 return NodeSentinel; // caller will return NULL
256 }
257
258 #ifdef ASSERT
259 Node* base = NULL;
260 if (address->is_AddP())
261 base = address->in(AddPNode::Base);
262 assert(base == NULL || t_adr->isa_rawptr() ||
263 !phase->type(base)->higher_equal(TypePtr::NULL_PTR), "NULL+offs not RAW address?");
264 #endif
265
266 // Avoid independent memory operations
267 Node* old_mem = mem;
268
269 // The code which unhooks non-raw memories from complete (macro-expanded)
270 // initializations was removed. After macro-expansion all stores catched
271 // by Initialize node became raw stores and there is no information
272 // which memory slices they modify. So it is unsafe to move any memory
273 // operation above these stores. Also in most cases hooked non-raw memories
274 // were already unhooked by using information from detect_ptr_independence()
275 // and find_previous_store().
276
277 if (mem->is_MergeMem()) {
278 MergeMemNode* mmem = mem->as_MergeMem();
279 const TypePtr *tp = t_adr->is_ptr();
280
281 mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
282 }
283
284 if (mem != old_mem) {
285 set_req(MemNode::Memory, mem);
286 if (phase->type( mem ) == Type::TOP) return NodeSentinel;
287 return this;
288 }
289
290 // let the subclass continue analyzing...
291 return NULL;
292 }
293
294 // Helper function for proving some simple control dominations.
295 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
296 // Already assumes that 'dom' is available at 'sub', and that 'sub'
297 // is not a constant (dominated by the method's StartNode).
298 // Used by MemNode::find_previous_store to prove that the
299 // control input of a memory operation predates (dominates)
300 // an allocation it wants to look past.
301 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
302 if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
303 return false; // Conservative answer for dead code
304
305 // Check 'dom'. Skip Proj and CatchProj nodes.
306 dom = dom->find_exact_control(dom);
307 if (dom == NULL || dom->is_top())
308 return false; // Conservative answer for dead code
309
310 if (dom == sub) {
311 // For the case when, for example, 'sub' is Initialize and the original
312 // 'dom' is Proj node of the 'sub'.
313 return false;
314 }
315
316 if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
317 return true;
318
319 // 'dom' dominates 'sub' if its control edge and control edges
320 // of all its inputs dominate or equal to sub's control edge.
321
322 // Currently 'sub' is either Allocate, Initialize or Start nodes.
323 // Or Region for the check in LoadNode::Ideal();
324 // 'sub' should have sub->in(0) != NULL.
325 assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
326 sub->is_Region(), "expecting only these nodes");
327
328 // Get control edge of 'sub'.
329 Node* orig_sub = sub;
330 sub = sub->find_exact_control(sub->in(0));
331 if (sub == NULL || sub->is_top())
332 return false; // Conservative answer for dead code
333
334 assert(sub->is_CFG(), "expecting control");
335
336 if (sub == dom)
337 return true;
338
339 if (sub->is_Start() || sub->is_Root())
340 return false;
341
342 {
343 // Check all control edges of 'dom'.
344
345 ResourceMark rm;
346 Arena* arena = Thread::current()->resource_area();
347 Node_List nlist(arena);
348 Unique_Node_List dom_list(arena);
349
350 dom_list.push(dom);
351 bool only_dominating_controls = false;
352
353 for (uint next = 0; next < dom_list.size(); next++) {
354 Node* n = dom_list.at(next);
355 if (n == orig_sub)
356 return false; // One of dom's inputs dominated by sub.
357 if (!n->is_CFG() && n->pinned()) {
358 // Check only own control edge for pinned non-control nodes.
359 n = n->find_exact_control(n->in(0));
360 if (n == NULL || n->is_top())
361 return false; // Conservative answer for dead code
362 assert(n->is_CFG(), "expecting control");
363 dom_list.push(n);
364 } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
365 only_dominating_controls = true;
366 } else if (n->is_CFG()) {
367 if (n->dominates(sub, nlist))
368 only_dominating_controls = true;
369 else
370 return false;
371 } else {
372 // First, own control edge.
373 Node* m = n->find_exact_control(n->in(0));
374 if (m != NULL) {
375 if (m->is_top())
376 return false; // Conservative answer for dead code
377 dom_list.push(m);
378 }
379 // Now, the rest of edges.
380 uint cnt = n->req();
381 for (uint i = 1; i < cnt; i++) {
382 m = n->find_exact_control(n->in(i));
383 if (m == NULL || m->is_top())
384 continue;
385 dom_list.push(m);
386 }
387 }
388 }
389 return only_dominating_controls;
390 }
391 }
392
393 //---------------------detect_ptr_independence---------------------------------
394 // Used by MemNode::find_previous_store to prove that two base
395 // pointers are never equal.
396 // The pointers are accompanied by their associated allocations,
397 // if any, which have been previously discovered by the caller.
398 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
399 Node* p2, AllocateNode* a2,
400 PhaseTransform* phase) {
401 // Attempt to prove that these two pointers cannot be aliased.
402 // They may both manifestly be allocations, and they should differ.
403 // Or, if they are not both allocations, they can be distinct constants.
404 // Otherwise, one is an allocation and the other a pre-existing value.
405 if (a1 == NULL && a2 == NULL) { // neither an allocation
406 return (p1 != p2) && p1->is_Con() && p2->is_Con();
407 } else if (a1 != NULL && a2 != NULL) { // both allocations
408 return (a1 != a2);
409 } else if (a1 != NULL) { // one allocation a1
410 // (Note: p2->is_Con implies p2->in(0)->is_Root, which dominates.)
411 return all_controls_dominate(p2, a1);
412 } else { //(a2 != NULL) // one allocation a2
413 return all_controls_dominate(p1, a2);
414 }
415 return false;
416 }
417
418
419 // The logic for reordering loads and stores uses four steps:
420 // (a) Walk carefully past stores and initializations which we
421 // can prove are independent of this load.
422 // (b) Observe that the next memory state makes an exact match
423 // with self (load or store), and locate the relevant store.
424 // (c) Ensure that, if we were to wire self directly to the store,
425 // the optimizer would fold it up somehow.
426 // (d) Do the rewiring, and return, depending on some other part of
427 // the optimizer to fold up the load.
428 // This routine handles steps (a) and (b). Steps (c) and (d) are
429 // specific to loads and stores, so they are handled by the callers.
430 // (Currently, only LoadNode::Ideal has steps (c), (d). More later.)
431 //
432 Node* MemNode::find_previous_store(PhaseTransform* phase) {
433 Node* ctrl = in(MemNode::Control);
434 Node* adr = in(MemNode::Address);
435 intptr_t offset = 0;
436 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
437 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase);
438
439 if (offset == Type::OffsetBot)
440 return NULL; // cannot unalias unless there are precise offsets
441
442 const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
443
444 intptr_t size_in_bytes = memory_size();
445
446 Node* mem = in(MemNode::Memory); // start searching here...
447
448 int cnt = 50; // Cycle limiter
449 for (;;) { // While we can dance past unrelated stores...
450 if (--cnt < 0) break; // Caught in cycle or a complicated dance?
451
452 if (mem->is_Store()) {
453 Node* st_adr = mem->in(MemNode::Address);
454 intptr_t st_offset = 0;
455 Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
456 if (st_base == NULL)
457 break; // inscrutable pointer
458 if (st_offset != offset && st_offset != Type::OffsetBot) {
459 const int MAX_STORE = BytesPerLong;
460 if (st_offset >= offset + size_in_bytes ||
461 st_offset <= offset - MAX_STORE ||
462 st_offset <= offset - mem->as_Store()->memory_size()) {
463 // Success: The offsets are provably independent.
464 // (You may ask, why not just test st_offset != offset and be done?
465 // The answer is that stores of different sizes can co-exist
466 // in the same sequence of RawMem effects. We sometimes initialize
467 // a whole 'tile' of array elements with a single jint or jlong.)
468 mem = mem->in(MemNode::Memory);
469 continue; // (a) advance through independent store memory
470 }
471 }
472 if (st_base != base &&
473 detect_ptr_independence(base, alloc,
474 st_base,
475 AllocateNode::Ideal_allocation(st_base, phase),
476 phase)) {
477 // Success: The bases are provably independent.
478 mem = mem->in(MemNode::Memory);
479 continue; // (a) advance through independent store memory
480 }
481
482 // (b) At this point, if the bases or offsets do not agree, we lose,
483 // since we have not managed to prove 'this' and 'mem' independent.
484 if (st_base == base && st_offset == offset) {
485 return mem; // let caller handle steps (c), (d)
486 }
487
488 } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
489 InitializeNode* st_init = mem->in(0)->as_Initialize();
490 AllocateNode* st_alloc = st_init->allocation();
491 if (st_alloc == NULL)
492 break; // something degenerated
493 bool known_identical = false;
494 bool known_independent = false;
495 if (alloc == st_alloc)
496 known_identical = true;
497 else if (alloc != NULL)
498 known_independent = true;
499 else if (all_controls_dominate(this, st_alloc))
500 known_independent = true;
501
502 if (known_independent) {
503 // The bases are provably independent: Either they are
504 // manifestly distinct allocations, or else the control
505 // of this load dominates the store's allocation.
506 int alias_idx = phase->C->get_alias_index(adr_type());
507 if (alias_idx == Compile::AliasIdxRaw) {
508 mem = st_alloc->in(TypeFunc::Memory);
509 } else {
510 mem = st_init->memory(alias_idx);
511 }
512 continue; // (a) advance through independent store memory
513 }
514
515 // (b) at this point, if we are not looking at a store initializing
516 // the same allocation we are loading from, we lose.
517 if (known_identical) {
518 // From caller, can_see_stored_value will consult find_captured_store.
519 return mem; // let caller handle steps (c), (d)
520 }
521
522 } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
523 // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
524 if (mem->is_Proj() && mem->in(0)->is_Call()) {
525 CallNode *call = mem->in(0)->as_Call();
526 if (!call->may_modify(addr_t, phase)) {
527 mem = call->in(TypeFunc::Memory);
528 continue; // (a) advance through independent call memory
529 }
530 } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
531 mem = mem->in(0)->in(TypeFunc::Memory);
532 continue; // (a) advance through independent MemBar memory
533 } else if (mem->is_MergeMem()) {
534 int alias_idx = phase->C->get_alias_index(adr_type());
535 mem = mem->as_MergeMem()->memory_at(alias_idx);
536 continue; // (a) advance through independent MergeMem memory
537 }
538 }
539
540 // Unless there is an explicit 'continue', we must bail out here,
541 // because 'mem' is an inscrutable memory state (e.g., a call).
542 break;
543 }
544
545 return NULL; // bail out
546 }
547
548 //----------------------calculate_adr_type-------------------------------------
549 // Helper function. Notices when the given type of address hits top or bottom.
550 // Also, asserts a cross-check of the type against the expected address type.
551 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
552 if (t == Type::TOP) return NULL; // does not touch memory any more?
553 #ifdef PRODUCT
554 cross_check = NULL;
555 #else
556 if (!VerifyAliases || is_error_reported() || Node::in_dump()) cross_check = NULL;
557 #endif
558 const TypePtr* tp = t->isa_ptr();
559 if (tp == NULL) {
560 assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
561 return TypePtr::BOTTOM; // touches lots of memory
562 } else {
563 #ifdef ASSERT
564 // %%%% [phh] We don't check the alias index if cross_check is
565 // TypeRawPtr::BOTTOM. Needs to be investigated.
566 if (cross_check != NULL &&
567 cross_check != TypePtr::BOTTOM &&
568 cross_check != TypeRawPtr::BOTTOM) {
569 // Recheck the alias index, to see if it has changed (due to a bug).
570 Compile* C = Compile::current();
571 assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
572 "must stay in the original alias category");
573 // The type of the address must be contained in the adr_type,
574 // disregarding "null"-ness.
575 // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
576 const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
577 assert(cross_check->meet(tp_notnull) == cross_check,
578 "real address must not escape from expected memory type");
579 }
580 #endif
581 return tp;
582 }
583 }
584
585 //------------------------adr_phi_is_loop_invariant----------------------------
586 // A helper function for Ideal_DU_postCCP to check if a Phi in a counted
587 // loop is loop invariant. Make a quick traversal of Phi and associated
588 // CastPP nodes, looking to see if they are a closed group within the loop.
589 bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) {
590 // The idea is that the phi-nest must boil down to only CastPP nodes
591 // with the same data. This implies that any path into the loop already
592 // includes such a CastPP, and so the original cast, whatever its input,
593 // must be covered by an equivalent cast, with an earlier control input.
594 ResourceMark rm;
595
596 // The loop entry input of the phi should be the unique dominating
597 // node for every Phi/CastPP in the loop.
598 Unique_Node_List closure;
599 closure.push(adr_phi->in(LoopNode::EntryControl));
600
601 // Add the phi node and the cast to the worklist.
602 Unique_Node_List worklist;
603 worklist.push(adr_phi);
604 if( cast != NULL ){
605 if( !cast->is_ConstraintCast() ) return false;
606 worklist.push(cast);
607 }
608
609 // Begin recursive walk of phi nodes.
610 while( worklist.size() ){
611 // Take a node off the worklist
612 Node *n = worklist.pop();
613 if( !closure.member(n) ){
614 // Add it to the closure.
615 closure.push(n);
616 // Make a sanity check to ensure we don't waste too much time here.
617 if( closure.size() > 20) return false;
618 // This node is OK if:
619 // - it is a cast of an identical value
620 // - or it is a phi node (then we add its inputs to the worklist)
621 // Otherwise, the node is not OK, and we presume the cast is not invariant
622 if( n->is_ConstraintCast() ){
623 worklist.push(n->in(1));
624 } else if( n->is_Phi() ) {
625 for( uint i = 1; i < n->req(); i++ ) {
626 worklist.push(n->in(i));
627 }
628 } else {
629 return false;
630 }
631 }
632 }
633
634 // Quit when the worklist is empty, and we've found no offending nodes.
635 return true;
636 }
637
638 //------------------------------Ideal_DU_postCCP-------------------------------
639 // Find any cast-away of null-ness and keep its control. Null cast-aways are
640 // going away in this pass and we need to make this memory op depend on the
641 // gating null check.
642 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) {
643 return Ideal_common_DU_postCCP(ccp, this, in(MemNode::Address));
644 }
645
646 // I tried to leave the CastPP's in. This makes the graph more accurate in
647 // some sense; we get to keep around the knowledge that an oop is not-null
648 // after some test. Alas, the CastPP's interfere with GVN (some values are
649 // the regular oop, some are the CastPP of the oop, all merge at Phi's which
650 // cannot collapse, etc). This cost us 10% on SpecJVM, even when I removed
651 // some of the more trivial cases in the optimizer. Removing more useless
652 // Phi's started allowing Loads to illegally float above null checks. I gave
653 // up on this approach. CNC 10/20/2000
654 // This static method may be called not from MemNode (EncodePNode calls it).
655 // Only the control edge of the node 'n' might be updated.
656 Node *MemNode::Ideal_common_DU_postCCP( PhaseCCP *ccp, Node* n, Node* adr ) {
657 Node *skipped_cast = NULL;
658 // Need a null check? Regular static accesses do not because they are
659 // from constant addresses. Array ops are gated by the range check (which
660 // always includes a NULL check). Just check field ops.
661 if( n->in(MemNode::Control) == NULL ) {
662 // Scan upwards for the highest location we can place this memory op.
663 while( true ) {
664 switch( adr->Opcode() ) {
665
666 case Op_AddP: // No change to NULL-ness, so peek thru AddP's
667 adr = adr->in(AddPNode::Base);
668 continue;
669
670 case Op_DecodeN: // No change to NULL-ness, so peek thru
671 adr = adr->in(1);
672 continue;
673
674 case Op_CastPP:
675 // If the CastPP is useless, just peek on through it.
676 if( ccp->type(adr) == ccp->type(adr->in(1)) ) {
677 // Remember the cast that we've peeked though. If we peek
678 // through more than one, then we end up remembering the highest
679 // one, that is, if in a loop, the one closest to the top.
680 skipped_cast = adr;
681 adr = adr->in(1);
682 continue;
683 }
684 // CastPP is going away in this pass! We need this memory op to be
685 // control-dependent on the test that is guarding the CastPP.
686 ccp->hash_delete(n);
687 n->set_req(MemNode::Control, adr->in(0));
688 ccp->hash_insert(n);
689 return n;
690
691 case Op_Phi:
692 // Attempt to float above a Phi to some dominating point.
693 if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) {
694 // If we've already peeked through a Cast (which could have set the
695 // control), we can't float above a Phi, because the skipped Cast
696 // may not be loop invariant.
697 if (adr_phi_is_loop_invariant(adr, skipped_cast)) {
698 adr = adr->in(1);
699 continue;
700 }
701 }
702
703 // Intentional fallthrough!
704
705 // No obvious dominating point. The mem op is pinned below the Phi
706 // by the Phi itself. If the Phi goes away (no true value is merged)
707 // then the mem op can float, but not indefinitely. It must be pinned
708 // behind the controls leading to the Phi.
709 case Op_CheckCastPP:
710 // These usually stick around to change address type, however a
711 // useless one can be elided and we still need to pick up a control edge
712 if (adr->in(0) == NULL) {
713 // This CheckCastPP node has NO control and is likely useless. But we
714 // need check further up the ancestor chain for a control input to keep
715 // the node in place. 4959717.
716 skipped_cast = adr;
717 adr = adr->in(1);
718 continue;
719 }
720 ccp->hash_delete(n);
721 n->set_req(MemNode::Control, adr->in(0));
722 ccp->hash_insert(n);
723 return n;
724
725 // List of "safe" opcodes; those that implicitly block the memory
726 // op below any null check.
727 case Op_CastX2P: // no null checks on native pointers
728 case Op_Parm: // 'this' pointer is not null
729 case Op_LoadP: // Loading from within a klass
730 case Op_LoadN: // Loading from within a klass
731 case Op_LoadKlass: // Loading from within a klass
732 case Op_LoadNKlass: // Loading from within a klass
733 case Op_ConP: // Loading from a klass
734 case Op_ConN: // Loading from a klass
735 case Op_CreateEx: // Sucking up the guts of an exception oop
736 case Op_Con: // Reading from TLS
737 case Op_CMoveP: // CMoveP is pinned
738 case Op_CMoveN: // CMoveN is pinned
739 break; // No progress
740
741 case Op_Proj: // Direct call to an allocation routine
742 case Op_SCMemProj: // Memory state from store conditional ops
743 #ifdef ASSERT
744 {
745 assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value");
746 const Node* call = adr->in(0);
747 if (call->is_CallJava()) {
748 const CallJavaNode* call_java = call->as_CallJava();
749 const TypeTuple *r = call_java->tf()->range();
750 assert(r->cnt() > TypeFunc::Parms, "must return value");
751 const Type* ret_type = r->field_at(TypeFunc::Parms);
752 assert(ret_type && ret_type->isa_ptr(), "must return pointer");
753 // We further presume that this is one of
754 // new_instance_Java, new_array_Java, or
755 // the like, but do not assert for this.
756 } else if (call->is_Allocate()) {
757 // similar case to new_instance_Java, etc.
758 } else if (!call->is_CallLeaf()) {
759 // Projections from fetch_oop (OSR) are allowed as well.
760 ShouldNotReachHere();
761 }
762 }
763 #endif
764 break;
765 default:
766 ShouldNotReachHere();
767 }
768 break;
769 }
770 }
771
772 return NULL; // No progress
773 }
774
775
776 //=============================================================================
777 uint LoadNode::size_of() const { return sizeof(*this); }
778 uint LoadNode::cmp( const Node &n ) const
779 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
780 const Type *LoadNode::bottom_type() const { return _type; }
781 uint LoadNode::ideal_reg() const {
782 return Matcher::base2reg[_type->base()];
783 }
784
785 #ifndef PRODUCT
786 void LoadNode::dump_spec(outputStream *st) const {
787 MemNode::dump_spec(st);
788 if( !Verbose && !WizardMode ) {
789 // standard dump does this in Verbose and WizardMode
790 st->print(" #"); _type->dump_on(st);
791 }
792 }
793 #endif
794
795
796 //----------------------------LoadNode::make-----------------------------------
797 // Polymorphic factory method:
798 Node *LoadNode::make( PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt ) {
799 Compile* C = gvn.C;
800
801 // sanity check the alias category against the created node type
802 assert(!(adr_type->isa_oopptr() &&
803 adr_type->offset() == oopDesc::klass_offset_in_bytes()),
804 "use LoadKlassNode instead");
805 assert(!(adr_type->isa_aryptr() &&
806 adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
807 "use LoadRangeNode instead");
808 switch (bt) {
809 case T_BOOLEAN: return new (C, 3) LoadUBNode(ctl, mem, adr, adr_type, rt->is_int() );
810 case T_BYTE: return new (C, 3) LoadBNode (ctl, mem, adr, adr_type, rt->is_int() );
811 case T_INT: return new (C, 3) LoadINode (ctl, mem, adr, adr_type, rt->is_int() );
812 case T_CHAR: return new (C, 3) LoadUSNode(ctl, mem, adr, adr_type, rt->is_int() );
813 case T_SHORT: return new (C, 3) LoadSNode (ctl, mem, adr, adr_type, rt->is_int() );
814 case T_LONG: return new (C, 3) LoadLNode (ctl, mem, adr, adr_type, rt->is_long() );
815 case T_FLOAT: return new (C, 3) LoadFNode (ctl, mem, adr, adr_type, rt );
816 case T_DOUBLE: return new (C, 3) LoadDNode (ctl, mem, adr, adr_type, rt );
817 case T_ADDRESS: return new (C, 3) LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr() );
818 case T_OBJECT:
819 #ifdef _LP64
820 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
821 Node* load = gvn.transform(new (C, 3) LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop()));
822 return new (C, 2) DecodeNNode(load, load->bottom_type()->make_ptr());
823 } else
824 #endif
825 {
826 assert(!adr->bottom_type()->is_ptr_to_narrowoop(), "should have got back a narrow oop");
827 return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr());
828 }
829 }
830 ShouldNotReachHere();
831 return (LoadNode*)NULL;
832 }
833
834 LoadLNode* LoadLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt) {
835 bool require_atomic = true;
836 return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), require_atomic);
837 }
838
839
840
841
842 //------------------------------hash-------------------------------------------
843 uint LoadNode::hash() const {
844 // unroll addition of interesting fields
845 return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
846 }
847
848 //---------------------------can_see_stored_value------------------------------
849 // This routine exists to make sure this set of tests is done the same
850 // everywhere. We need to make a coordinated change: first LoadNode::Ideal
851 // will change the graph shape in a way which makes memory alive twice at the
852 // same time (uses the Oracle model of aliasing), then some
853 // LoadXNode::Identity will fold things back to the equivalence-class model
854 // of aliasing.
855 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
856 Node* ld_adr = in(MemNode::Address);
857
858 const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
859 Compile::AliasType* atp = tp != NULL ? phase->C->alias_type(tp) : NULL;
860 if (EliminateAutoBox && atp != NULL && atp->index() >= Compile::AliasIdxRaw &&
861 atp->field() != NULL && !atp->field()->is_volatile()) {
862 uint alias_idx = atp->index();
863 bool final = atp->field()->is_final();
864 Node* result = NULL;
865 Node* current = st;
866 // Skip through chains of MemBarNodes checking the MergeMems for
867 // new states for the slice of this load. Stop once any other
868 // kind of node is encountered. Loads from final memory can skip
869 // through any kind of MemBar but normal loads shouldn't skip
870 // through MemBarAcquire since the could allow them to move out of
871 // a synchronized region.
872 while (current->is_Proj()) {
873 int opc = current->in(0)->Opcode();
874 if ((final && opc == Op_MemBarAcquire) ||
875 opc == Op_MemBarRelease || opc == Op_MemBarCPUOrder) {
876 Node* mem = current->in(0)->in(TypeFunc::Memory);
877 if (mem->is_MergeMem()) {
878 MergeMemNode* merge = mem->as_MergeMem();
879 Node* new_st = merge->memory_at(alias_idx);
880 if (new_st == merge->base_memory()) {
881 // Keep searching
882 current = merge->base_memory();
883 continue;
884 }
885 // Save the new memory state for the slice and fall through
886 // to exit.
887 result = new_st;
888 }
889 }
890 break;
891 }
892 if (result != NULL) {
893 st = result;
894 }
895 }
896
897
898 // Loop around twice in the case Load -> Initialize -> Store.
899 // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
900 for (int trip = 0; trip <= 1; trip++) {
901
902 if (st->is_Store()) {
903 Node* st_adr = st->in(MemNode::Address);
904 if (!phase->eqv(st_adr, ld_adr)) {
905 // Try harder before giving up... Match raw and non-raw pointers.
906 intptr_t st_off = 0;
907 AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
908 if (alloc == NULL) return NULL;
909 intptr_t ld_off = 0;
910 AllocateNode* allo2 = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
911 if (alloc != allo2) return NULL;
912 if (ld_off != st_off) return NULL;
913 // At this point we have proven something like this setup:
914 // A = Allocate(...)
915 // L = LoadQ(, AddP(CastPP(, A.Parm),, #Off))
916 // S = StoreQ(, AddP(, A.Parm , #Off), V)
917 // (Actually, we haven't yet proven the Q's are the same.)
918 // In other words, we are loading from a casted version of
919 // the same pointer-and-offset that we stored to.
920 // Thus, we are able to replace L by V.
921 }
922 // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
923 if (store_Opcode() != st->Opcode())
924 return NULL;
925 return st->in(MemNode::ValueIn);
926 }
927
928 intptr_t offset = 0; // scratch
929
930 // A load from a freshly-created object always returns zero.
931 // (This can happen after LoadNode::Ideal resets the load's memory input
932 // to find_captured_store, which returned InitializeNode::zero_memory.)
933 if (st->is_Proj() && st->in(0)->is_Allocate() &&
934 st->in(0) == AllocateNode::Ideal_allocation(ld_adr, phase, offset) &&
935 offset >= st->in(0)->as_Allocate()->minimum_header_size()) {
936 // return a zero value for the load's basic type
937 // (This is one of the few places where a generic PhaseTransform
938 // can create new nodes. Think of it as lazily manifesting
939 // virtually pre-existing constants.)
940 return phase->zerocon(memory_type());
941 }
942
943 // A load from an initialization barrier can match a captured store.
944 if (st->is_Proj() && st->in(0)->is_Initialize()) {
945 InitializeNode* init = st->in(0)->as_Initialize();
946 AllocateNode* alloc = init->allocation();
947 if (alloc != NULL &&
948 alloc == AllocateNode::Ideal_allocation(ld_adr, phase, offset)) {
949 // examine a captured store value
950 st = init->find_captured_store(offset, memory_size(), phase);
951 if (st != NULL)
952 continue; // take one more trip around
953 }
954 }
955
956 break;
957 }
958
959 return NULL;
960 }
961
962 //----------------------is_instance_field_load_with_local_phi------------------
963 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
964 if( in(MemNode::Memory)->is_Phi() && in(MemNode::Memory)->in(0) == ctrl &&
965 in(MemNode::Address)->is_AddP() ) {
966 const TypeOopPtr* t_oop = in(MemNode::Address)->bottom_type()->isa_oopptr();
967 // Only instances.
968 if( t_oop != NULL && t_oop->is_known_instance_field() &&
969 t_oop->offset() != Type::OffsetBot &&
970 t_oop->offset() != Type::OffsetTop) {
971 return true;
972 }
973 }
974 return false;
975 }
976
977 //------------------------------Identity---------------------------------------
978 // Loads are identity if previous store is to same address
979 Node *LoadNode::Identity( PhaseTransform *phase ) {
980 // If the previous store-maker is the right kind of Store, and the store is
981 // to the same address, then we are equal to the value stored.
982 Node* mem = in(MemNode::Memory);
983 Node* value = can_see_stored_value(mem, phase);
984 if( value ) {
985 // byte, short & char stores truncate naturally.
986 // A load has to load the truncated value which requires
987 // some sort of masking operation and that requires an
988 // Ideal call instead of an Identity call.
989 if (memory_size() < BytesPerInt) {
990 // If the input to the store does not fit with the load's result type,
991 // it must be truncated via an Ideal call.
992 if (!phase->type(value)->higher_equal(phase->type(this)))
993 return this;
994 }
995 // (This works even when value is a Con, but LoadNode::Value
996 // usually runs first, producing the singleton type of the Con.)
997 return value;
998 }
999
1000 // Search for an existing data phi which was generated before for the same
1001 // instance's field to avoid infinite generation of phis in a loop.
1002 Node *region = mem->in(0);
1003 if (is_instance_field_load_with_local_phi(region)) {
1004 const TypePtr *addr_t = in(MemNode::Address)->bottom_type()->isa_ptr();
1005 int this_index = phase->C->get_alias_index(addr_t);
1006 int this_offset = addr_t->offset();
1007 int this_id = addr_t->is_oopptr()->instance_id();
1008 const Type* this_type = bottom_type();
1009 for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1010 Node* phi = region->fast_out(i);
1011 if (phi->is_Phi() && phi != mem &&
1012 phi->as_Phi()->is_same_inst_field(this_type, this_id, this_index, this_offset)) {
1013 return phi;
1014 }
1015 }
1016 }
1017
1018 return this;
1019 }
1020
1021
1022 // Returns true if the AliasType refers to the field that holds the
1023 // cached box array. Currently only handles the IntegerCache case.
1024 static bool is_autobox_cache(Compile::AliasType* atp) {
1025 if (atp != NULL && atp->field() != NULL) {
1026 ciField* field = atp->field();
1027 ciSymbol* klass = field->holder()->name();
1028 if (field->name() == ciSymbol::cache_field_name() &&
1029 field->holder()->uses_default_loader() &&
1030 klass == ciSymbol::java_lang_Integer_IntegerCache()) {
1031 return true;
1032 }
1033 }
1034 return false;
1035 }
1036
1037 // Fetch the base value in the autobox array
1038 static bool fetch_autobox_base(Compile::AliasType* atp, int& cache_offset) {
1039 if (atp != NULL && atp->field() != NULL) {
1040 ciField* field = atp->field();
1041 ciSymbol* klass = field->holder()->name();
1042 if (field->name() == ciSymbol::cache_field_name() &&
1043 field->holder()->uses_default_loader() &&
1044 klass == ciSymbol::java_lang_Integer_IntegerCache()) {
1045 assert(field->is_constant(), "what?");
1046 ciObjArray* array = field->constant_value().as_object()->as_obj_array();
1047 // Fetch the box object at the base of the array and get its value
1048 ciInstance* box = array->obj_at(0)->as_instance();
1049 ciInstanceKlass* ik = box->klass()->as_instance_klass();
1050 if (ik->nof_nonstatic_fields() == 1) {
1051 // This should be true nonstatic_field_at requires calling
1052 // nof_nonstatic_fields so check it anyway
1053 ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1054 cache_offset = c.as_int();
1055 }
1056 return true;
1057 }
1058 }
1059 return false;
1060 }
1061
1062 // Returns true if the AliasType refers to the value field of an
1063 // autobox object. Currently only handles Integer.
1064 static bool is_autobox_object(Compile::AliasType* atp) {
1065 if (atp != NULL && atp->field() != NULL) {
1066 ciField* field = atp->field();
1067 ciSymbol* klass = field->holder()->name();
1068 if (field->name() == ciSymbol::value_name() &&
1069 field->holder()->uses_default_loader() &&
1070 klass == ciSymbol::java_lang_Integer()) {
1071 return true;
1072 }
1073 }
1074 return false;
1075 }
1076
1077
1078 // We're loading from an object which has autobox behaviour.
1079 // If this object is result of a valueOf call we'll have a phi
1080 // merging a newly allocated object and a load from the cache.
1081 // We want to replace this load with the original incoming
1082 // argument to the valueOf call.
1083 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1084 Node* base = in(Address)->in(AddPNode::Base);
1085 if (base->is_Phi() && base->req() == 3) {
1086 AllocateNode* allocation = NULL;
1087 int allocation_index = -1;
1088 int load_index = -1;
1089 for (uint i = 1; i < base->req(); i++) {
1090 allocation = AllocateNode::Ideal_allocation(base->in(i), phase);
1091 if (allocation != NULL) {
1092 allocation_index = i;
1093 load_index = 3 - allocation_index;
1094 break;
1095 }
1096 }
1097 bool has_load = ( allocation != NULL &&
1098 (base->in(load_index)->is_Load() ||
1099 base->in(load_index)->is_DecodeN() &&
1100 base->in(load_index)->in(1)->is_Load()) );
1101 if (has_load && in(Memory)->is_Phi() && in(Memory)->in(0) == base->in(0)) {
1102 // Push the loads from the phi that comes from valueOf up
1103 // through it to allow elimination of the loads and the recovery
1104 // of the original value.
1105 Node* mem_phi = in(Memory);
1106 Node* offset = in(Address)->in(AddPNode::Offset);
1107 Node* region = base->in(0);
1108
1109 Node* in1 = clone();
1110 Node* in1_addr = in1->in(Address)->clone();
1111 in1_addr->set_req(AddPNode::Base, base->in(allocation_index));
1112 in1_addr->set_req(AddPNode::Address, base->in(allocation_index));
1113 in1_addr->set_req(AddPNode::Offset, offset);
1114 in1->set_req(0, region->in(allocation_index));
1115 in1->set_req(Address, in1_addr);
1116 in1->set_req(Memory, mem_phi->in(allocation_index));
1117
1118 Node* in2 = clone();
1119 Node* in2_addr = in2->in(Address)->clone();
1120 in2_addr->set_req(AddPNode::Base, base->in(load_index));
1121 in2_addr->set_req(AddPNode::Address, base->in(load_index));
1122 in2_addr->set_req(AddPNode::Offset, offset);
1123 in2->set_req(0, region->in(load_index));
1124 in2->set_req(Address, in2_addr);
1125 in2->set_req(Memory, mem_phi->in(load_index));
1126
1127 in1_addr = phase->transform(in1_addr);
1128 in1 = phase->transform(in1);
1129 in2_addr = phase->transform(in2_addr);
1130 in2 = phase->transform(in2);
1131
1132 PhiNode* result = PhiNode::make_blank(region, this);
1133 result->set_req(allocation_index, in1);
1134 result->set_req(load_index, in2);
1135 return result;
1136 }
1137 } else if (base->is_Load() ||
1138 base->is_DecodeN() && base->in(1)->is_Load()) {
1139 if (base->is_DecodeN()) {
1140 // Get LoadN node which loads cached Integer object
1141 base = base->in(1);
1142 }
1143 // Eliminate the load of Integer.value for integers from the cache
1144 // array by deriving the value from the index into the array.
1145 // Capture the offset of the load and then reverse the computation.
1146 Node* load_base = base->in(Address)->in(AddPNode::Base);
1147 if (load_base->is_DecodeN()) {
1148 // Get LoadN node which loads IntegerCache.cache field
1149 load_base = load_base->in(1);
1150 }
1151 if (load_base != NULL) {
1152 Compile::AliasType* atp = phase->C->alias_type(load_base->adr_type());
1153 intptr_t cache_offset;
1154 int shift = -1;
1155 Node* cache = NULL;
1156 if (is_autobox_cache(atp)) {
1157 shift = exact_log2(type2aelembytes(T_OBJECT));
1158 cache = AddPNode::Ideal_base_and_offset(load_base->in(Address), phase, cache_offset);
1159 }
1160 if (cache != NULL && base->in(Address)->is_AddP()) {
1161 Node* elements[4];
1162 int count = base->in(Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
1163 int cache_low;
1164 if (count > 0 && fetch_autobox_base(atp, cache_low)) {
1165 int offset = arrayOopDesc::base_offset_in_bytes(memory_type()) - (cache_low << shift);
1166 // Add up all the offsets making of the address of the load
1167 Node* result = elements[0];
1168 for (int i = 1; i < count; i++) {
1169 result = phase->transform(new (phase->C, 3) AddXNode(result, elements[i]));
1170 }
1171 // Remove the constant offset from the address and then
1172 // remove the scaling of the offset to recover the original index.
1173 result = phase->transform(new (phase->C, 3) AddXNode(result, phase->MakeConX(-offset)));
1174 if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1175 // Peel the shift off directly but wrap it in a dummy node
1176 // since Ideal can't return existing nodes
1177 result = new (phase->C, 3) RShiftXNode(result->in(1), phase->intcon(0));
1178 } else {
1179 result = new (phase->C, 3) RShiftXNode(result, phase->intcon(shift));
1180 }
1181 #ifdef _LP64
1182 result = new (phase->C, 2) ConvL2INode(phase->transform(result));
1183 #endif
1184 return result;
1185 }
1186 }
1187 }
1188 }
1189 return NULL;
1190 }
1191
1192 //------------------------------split_through_phi------------------------------
1193 // Split instance field load through Phi.
1194 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1195 Node* mem = in(MemNode::Memory);
1196 Node* address = in(MemNode::Address);
1197 const TypePtr *addr_t = phase->type(address)->isa_ptr();
1198 const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1199
1200 assert(mem->is_Phi() && (t_oop != NULL) &&
1201 t_oop->is_known_instance_field(), "invalide conditions");
1202
1203 Node *region = mem->in(0);
1204 if (region == NULL) {
1205 return NULL; // Wait stable graph
1206 }
1207 uint cnt = mem->req();
1208 for( uint i = 1; i < cnt; i++ ) {
1209 Node *in = mem->in(i);
1210 if( in == NULL ) {
1211 return NULL; // Wait stable graph
1212 }
1213 }
1214 // Check for loop invariant.
1215 if (cnt == 3) {
1216 for( uint i = 1; i < cnt; i++ ) {
1217 Node *in = mem->in(i);
1218 Node* m = MemNode::optimize_memory_chain(in, addr_t, phase);
1219 if (m == mem) {
1220 set_req(MemNode::Memory, mem->in(cnt - i)); // Skip this phi.
1221 return this;
1222 }
1223 }
1224 }
1225 // Split through Phi (see original code in loopopts.cpp).
1226 assert(phase->C->have_alias_type(addr_t), "instance should have alias type");
1227
1228 // Do nothing here if Identity will find a value
1229 // (to avoid infinite chain of value phis generation).
1230 if ( !phase->eqv(this, this->Identity(phase)) )
1231 return NULL;
1232
1233 // Skip the split if the region dominates some control edge of the address.
1234 if (cnt == 3 && !MemNode::all_controls_dominate(address, region))
1235 return NULL;
1236
1237 const Type* this_type = this->bottom_type();
1238 int this_index = phase->C->get_alias_index(addr_t);
1239 int this_offset = addr_t->offset();
1240 int this_iid = addr_t->is_oopptr()->instance_id();
1241 int wins = 0;
1242 PhaseIterGVN *igvn = phase->is_IterGVN();
1243 Node *phi = new (igvn->C, region->req()) PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
1244 for( uint i = 1; i < region->req(); i++ ) {
1245 Node *x;
1246 Node* the_clone = NULL;
1247 if( region->in(i) == phase->C->top() ) {
1248 x = phase->C->top(); // Dead path? Use a dead data op
1249 } else {
1250 x = this->clone(); // Else clone up the data op
1251 the_clone = x; // Remember for possible deletion.
1252 // Alter data node to use pre-phi inputs
1253 if( this->in(0) == region ) {
1254 x->set_req( 0, region->in(i) );
1255 } else {
1256 x->set_req( 0, NULL );
1257 }
1258 for( uint j = 1; j < this->req(); j++ ) {
1259 Node *in = this->in(j);
1260 if( in->is_Phi() && in->in(0) == region )
1261 x->set_req( j, in->in(i) ); // Use pre-Phi input for the clone
1262 }
1263 }
1264 // Check for a 'win' on some paths
1265 const Type *t = x->Value(igvn);
1266
1267 bool singleton = t->singleton();
1268
1269 // See comments in PhaseIdealLoop::split_thru_phi().
1270 if( singleton && t == Type::TOP ) {
1271 singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1272 }
1273
1274 if( singleton ) {
1275 wins++;
1276 x = igvn->makecon(t);
1277 } else {
1278 // We now call Identity to try to simplify the cloned node.
1279 // Note that some Identity methods call phase->type(this).
1280 // Make sure that the type array is big enough for
1281 // our new node, even though we may throw the node away.
1282 // (This tweaking with igvn only works because x is a new node.)
1283 igvn->set_type(x, t);
1284 // If x is a TypeNode, capture any more-precise type permanently into Node
1285 // otherwise it will be not updated during igvn->transform since
1286 // igvn->type(x) is set to x->Value() already.
1287 x->raise_bottom_type(t);
1288 Node *y = x->Identity(igvn);
1289 if( y != x ) {
1290 wins++;
1291 x = y;
1292 } else {
1293 y = igvn->hash_find(x);
1294 if( y ) {
1295 wins++;
1296 x = y;
1297 } else {
1298 // Else x is a new node we are keeping
1299 // We do not need register_new_node_with_optimizer
1300 // because set_type has already been called.
1301 igvn->_worklist.push(x);
1302 }
1303 }
1304 }
1305 if (x != the_clone && the_clone != NULL)
1306 igvn->remove_dead_node(the_clone);
1307 phi->set_req(i, x);
1308 }
1309 if( wins > 0 ) {
1310 // Record Phi
1311 igvn->register_new_node_with_optimizer(phi);
1312 return phi;
1313 }
1314 igvn->remove_dead_node(phi);
1315 return NULL;
1316 }
1317
1318 //------------------------------Ideal------------------------------------------
1319 // If the load is from Field memory and the pointer is non-null, we can
1320 // zero out the control input.
1321 // If the offset is constant and the base is an object allocation,
1322 // try to hook me up to the exact initializing store.
1323 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1324 Node* p = MemNode::Ideal_common(phase, can_reshape);
1325 if (p) return (p == NodeSentinel) ? NULL : p;
1326
1327 Node* ctrl = in(MemNode::Control);
1328 Node* address = in(MemNode::Address);
1329
1330 // Skip up past a SafePoint control. Cannot do this for Stores because
1331 // pointer stores & cardmarks must stay on the same side of a SafePoint.
1332 if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1333 phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1334 ctrl = ctrl->in(0);
1335 set_req(MemNode::Control,ctrl);
1336 }
1337
1338 intptr_t ignore = 0;
1339 Node* base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1340 if (base != NULL
1341 && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1342 // Check for useless control edge in some common special cases
1343 if (in(MemNode::Control) != NULL
1344 && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1345 && all_controls_dominate(base, phase->C->start())) {
1346 // A method-invariant, non-null address (constant or 'this' argument).
1347 set_req(MemNode::Control, NULL);
1348 }
1349
1350 if (EliminateAutoBox && can_reshape) {
1351 assert(!phase->type(base)->higher_equal(TypePtr::NULL_PTR), "the autobox pointer should be non-null");
1352 Compile::AliasType* atp = phase->C->alias_type(adr_type());
1353 if (is_autobox_object(atp)) {
1354 Node* result = eliminate_autobox(phase);
1355 if (result != NULL) return result;
1356 }
1357 }
1358 }
1359
1360 Node* mem = in(MemNode::Memory);
1361 const TypePtr *addr_t = phase->type(address)->isa_ptr();
1362
1363 if (addr_t != NULL) {
1364 // try to optimize our memory input
1365 Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, phase);
1366 if (opt_mem != mem) {
1367 set_req(MemNode::Memory, opt_mem);
1368 if (phase->type( opt_mem ) == Type::TOP) return NULL;
1369 return this;
1370 }
1371 const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1372 if (can_reshape && opt_mem->is_Phi() &&
1373 (t_oop != NULL) && t_oop->is_known_instance_field()) {
1374 // Split instance field load through Phi.
1375 Node* result = split_through_phi(phase);
1376 if (result != NULL) return result;
1377 }
1378 }
1379
1380 // Check for prior store with a different base or offset; make Load
1381 // independent. Skip through any number of them. Bail out if the stores
1382 // are in an endless dead cycle and report no progress. This is a key
1383 // transform for Reflection. However, if after skipping through the Stores
1384 // we can't then fold up against a prior store do NOT do the transform as
1385 // this amounts to using the 'Oracle' model of aliasing. It leaves the same
1386 // array memory alive twice: once for the hoisted Load and again after the
1387 // bypassed Store. This situation only works if EVERYBODY who does
1388 // anti-dependence work knows how to bypass. I.e. we need all
1389 // anti-dependence checks to ask the same Oracle. Right now, that Oracle is
1390 // the alias index stuff. So instead, peek through Stores and IFF we can
1391 // fold up, do so.
1392 Node* prev_mem = find_previous_store(phase);
1393 // Steps (a), (b): Walk past independent stores to find an exact match.
1394 if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1395 // (c) See if we can fold up on the spot, but don't fold up here.
1396 // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1397 // just return a prior value, which is done by Identity calls.
1398 if (can_see_stored_value(prev_mem, phase)) {
1399 // Make ready for step (d):
1400 set_req(MemNode::Memory, prev_mem);
1401 return this;
1402 }
1403 }
1404
1405 return NULL; // No further progress
1406 }
1407
1408 // Helper to recognize certain Klass fields which are invariant across
1409 // some group of array types (e.g., int[] or all T[] where T < Object).
1410 const Type*
1411 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1412 ciKlass* klass) const {
1413 if (tkls->offset() == Klass::modifier_flags_offset_in_bytes() + (int)sizeof(oopDesc)) {
1414 // The field is Klass::_modifier_flags. Return its (constant) value.
1415 // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1416 assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1417 return TypeInt::make(klass->modifier_flags());
1418 }
1419 if (tkls->offset() == Klass::access_flags_offset_in_bytes() + (int)sizeof(oopDesc)) {
1420 // The field is Klass::_access_flags. Return its (constant) value.
1421 // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1422 assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1423 return TypeInt::make(klass->access_flags());
1424 }
1425 if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc)) {
1426 // The field is Klass::_layout_helper. Return its constant value if known.
1427 assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1428 return TypeInt::make(klass->layout_helper());
1429 }
1430
1431 // No match.
1432 return NULL;
1433 }
1434
1435 //------------------------------Value-----------------------------------------
1436 const Type *LoadNode::Value( PhaseTransform *phase ) const {
1437 // Either input is TOP ==> the result is TOP
1438 Node* mem = in(MemNode::Memory);
1439 const Type *t1 = phase->type(mem);
1440 if (t1 == Type::TOP) return Type::TOP;
1441 Node* adr = in(MemNode::Address);
1442 const TypePtr* tp = phase->type(adr)->isa_ptr();
1443 if (tp == NULL || tp->empty()) return Type::TOP;
1444 int off = tp->offset();
1445 assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1446
1447 // Try to guess loaded type from pointer type
1448 if (tp->base() == Type::AryPtr) {
1449 const Type *t = tp->is_aryptr()->elem();
1450 // Don't do this for integer types. There is only potential profit if
1451 // the element type t is lower than _type; that is, for int types, if _type is
1452 // more restrictive than t. This only happens here if one is short and the other
1453 // char (both 16 bits), and in those cases we've made an intentional decision
1454 // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1455 // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1456 //
1457 // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1458 // where the _gvn.type of the AddP is wider than 8. This occurs when an earlier
1459 // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1460 // subsumed by p1. If p1 is on the worklist but has not yet been re-transformed,
1461 // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1462 // In fact, that could have been the original type of p1, and p1 could have
1463 // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1464 // expression (LShiftL quux 3) independently optimized to the constant 8.
1465 if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1466 && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1467 // t might actually be lower than _type, if _type is a unique
1468 // concrete subclass of abstract class t.
1469 // Make sure the reference is not into the header, by comparing
1470 // the offset against the offset of the start of the array's data.
1471 // Different array types begin at slightly different offsets (12 vs. 16).
1472 // We choose T_BYTE as an example base type that is least restrictive
1473 // as to alignment, which will therefore produce the smallest
1474 // possible base offset.
1475 const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1476 if ((uint)off >= (uint)min_base_off) { // is the offset beyond the header?
1477 const Type* jt = t->join(_type);
1478 // In any case, do not allow the join, per se, to empty out the type.
1479 if (jt->empty() && !t->empty()) {
1480 // This can happen if a interface-typed array narrows to a class type.
1481 jt = _type;
1482 }
1483
1484 if (EliminateAutoBox && adr->is_AddP()) {
1485 // The pointers in the autobox arrays are always non-null
1486 Node* base = adr->in(AddPNode::Base);
1487 if (base != NULL &&
1488 !phase->type(base)->higher_equal(TypePtr::NULL_PTR)) {
1489 Compile::AliasType* atp = phase->C->alias_type(base->adr_type());
1490 if (is_autobox_cache(atp)) {
1491 return jt->join(TypePtr::NOTNULL)->is_ptr();
1492 }
1493 }
1494 }
1495 return jt;
1496 }
1497 }
1498 } else if (tp->base() == Type::InstPtr) {
1499 assert( off != Type::OffsetBot ||
1500 // arrays can be cast to Objects
1501 tp->is_oopptr()->klass()->is_java_lang_Object() ||
1502 // unsafe field access may not have a constant offset
1503 phase->C->has_unsafe_access(),
1504 "Field accesses must be precise" );
1505 // For oop loads, we expect the _type to be precise
1506 } else if (tp->base() == Type::KlassPtr) {
1507 assert( off != Type::OffsetBot ||
1508 // arrays can be cast to Objects
1509 tp->is_klassptr()->klass()->is_java_lang_Object() ||
1510 // also allow array-loading from the primary supertype
1511 // array during subtype checks
1512 Opcode() == Op_LoadKlass,
1513 "Field accesses must be precise" );
1514 // For klass/static loads, we expect the _type to be precise
1515 }
1516
1517 const TypeKlassPtr *tkls = tp->isa_klassptr();
1518 if (tkls != NULL && !StressReflectiveCode) {
1519 ciKlass* klass = tkls->klass();
1520 if (klass->is_loaded() && tkls->klass_is_exact()) {
1521 // We are loading a field from a Klass metaobject whose identity
1522 // is known at compile time (the type is "exact" or "precise").
1523 // Check for fields we know are maintained as constants by the VM.
1524 if (tkls->offset() == Klass::super_check_offset_offset_in_bytes() + (int)sizeof(oopDesc)) {
1525 // The field is Klass::_super_check_offset. Return its (constant) value.
1526 // (Folds up type checking code.)
1527 assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1528 return TypeInt::make(klass->super_check_offset());
1529 }
1530 // Compute index into primary_supers array
1531 juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop);
1532 // Check for overflowing; use unsigned compare to handle the negative case.
1533 if( depth < ciKlass::primary_super_limit() ) {
1534 // The field is an element of Klass::_primary_supers. Return its (constant) value.
1535 // (Folds up type checking code.)
1536 assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1537 ciKlass *ss = klass->super_of_depth(depth);
1538 return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1539 }
1540 const Type* aift = load_array_final_field(tkls, klass);
1541 if (aift != NULL) return aift;
1542 if (tkls->offset() == in_bytes(arrayKlass::component_mirror_offset()) + (int)sizeof(oopDesc)
1543 && klass->is_array_klass()) {
1544 // The field is arrayKlass::_component_mirror. Return its (constant) value.
1545 // (Folds up aClassConstant.getComponentType, common in Arrays.copyOf.)
1546 assert(Opcode() == Op_LoadP, "must load an oop from _component_mirror");
1547 return TypeInstPtr::make(klass->as_array_klass()->component_mirror());
1548 }
1549 if (tkls->offset() == Klass::java_mirror_offset_in_bytes() + (int)sizeof(oopDesc)) {
1550 // The field is Klass::_java_mirror. Return its (constant) value.
1551 // (Folds up the 2nd indirection in anObjConstant.getClass().)
1552 assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1553 return TypeInstPtr::make(klass->java_mirror());
1554 }
1555 }
1556
1557 // We can still check if we are loading from the primary_supers array at a
1558 // shallow enough depth. Even though the klass is not exact, entries less
1559 // than or equal to its super depth are correct.
1560 if (klass->is_loaded() ) {
1561 ciType *inner = klass->klass();
1562 while( inner->is_obj_array_klass() )
1563 inner = inner->as_obj_array_klass()->base_element_type();
1564 if( inner->is_instance_klass() &&
1565 !inner->as_instance_klass()->flags().is_interface() ) {
1566 // Compute index into primary_supers array
1567 juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop);
1568 // Check for overflowing; use unsigned compare to handle the negative case.
1569 if( depth < ciKlass::primary_super_limit() &&
1570 depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1571 // The field is an element of Klass::_primary_supers. Return its (constant) value.
1572 // (Folds up type checking code.)
1573 assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1574 ciKlass *ss = klass->super_of_depth(depth);
1575 return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1576 }
1577 }
1578 }
1579
1580 // If the type is enough to determine that the thing is not an array,
1581 // we can give the layout_helper a positive interval type.
1582 // This will help short-circuit some reflective code.
1583 if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc)
1584 && !klass->is_array_klass() // not directly typed as an array
1585 && !klass->is_interface() // specifically not Serializable & Cloneable
1586 && !klass->is_java_lang_Object() // not the supertype of all T[]
1587 ) {
1588 // Note: When interfaces are reliable, we can narrow the interface
1589 // test to (klass != Serializable && klass != Cloneable).
1590 assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1591 jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1592 // The key property of this type is that it folds up tests
1593 // for array-ness, since it proves that the layout_helper is positive.
1594 // Thus, a generic value like the basic object layout helper works fine.
1595 return TypeInt::make(min_size, max_jint, Type::WidenMin);
1596 }
1597 }
1598
1599 // If we are loading from a freshly-allocated object, produce a zero,
1600 // if the load is provably beyond the header of the object.
1601 // (Also allow a variable load from a fresh array to produce zero.)
1602 if (ReduceFieldZeroing) {
1603 Node* value = can_see_stored_value(mem,phase);
1604 if (value != NULL && value->is_Con())
1605 return value->bottom_type();
1606 }
1607
1608 const TypeOopPtr *tinst = tp->isa_oopptr();
1609 if (tinst != NULL && tinst->is_known_instance_field()) {
1610 // If we have an instance type and our memory input is the
1611 // programs's initial memory state, there is no matching store,
1612 // so just return a zero of the appropriate type
1613 Node *mem = in(MemNode::Memory);
1614 if (mem->is_Parm() && mem->in(0)->is_Start()) {
1615 assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1616 return Type::get_zero_type(_type->basic_type());
1617 }
1618 }
1619 return _type;
1620 }
1621
1622 //------------------------------match_edge-------------------------------------
1623 // Do we Match on this edge index or not? Match only the address.
1624 uint LoadNode::match_edge(uint idx) const {
1625 return idx == MemNode::Address;
1626 }
1627
1628 //--------------------------LoadBNode::Ideal--------------------------------------
1629 //
1630 // If the previous store is to the same address as this load,
1631 // and the value stored was larger than a byte, replace this load
1632 // with the value stored truncated to a byte. If no truncation is
1633 // needed, the replacement is done in LoadNode::Identity().
1634 //
1635 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1636 Node* mem = in(MemNode::Memory);
1637 Node* value = can_see_stored_value(mem,phase);
1638 if( value && !phase->type(value)->higher_equal( _type ) ) {
1639 Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(24)) );
1640 return new (phase->C, 3) RShiftINode(result, phase->intcon(24));
1641 }
1642 // Identity call will handle the case where truncation is not needed.
1643 return LoadNode::Ideal(phase, can_reshape);
1644 }
1645
1646 //--------------------------LoadUBNode::Ideal-------------------------------------
1647 //
1648 // If the previous store is to the same address as this load,
1649 // and the value stored was larger than a byte, replace this load
1650 // with the value stored truncated to a byte. If no truncation is
1651 // needed, the replacement is done in LoadNode::Identity().
1652 //
1653 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1654 Node* mem = in(MemNode::Memory);
1655 Node* value = can_see_stored_value(mem, phase);
1656 if (value && !phase->type(value)->higher_equal(_type))
1657 return new (phase->C, 3) AndINode(value, phase->intcon(0xFF));
1658 // Identity call will handle the case where truncation is not needed.
1659 return LoadNode::Ideal(phase, can_reshape);
1660 }
1661
1662 //--------------------------LoadUSNode::Ideal-------------------------------------
1663 //
1664 // If the previous store is to the same address as this load,
1665 // and the value stored was larger than a char, replace this load
1666 // with the value stored truncated to a char. If no truncation is
1667 // needed, the replacement is done in LoadNode::Identity().
1668 //
1669 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1670 Node* mem = in(MemNode::Memory);
1671 Node* value = can_see_stored_value(mem,phase);
1672 if( value && !phase->type(value)->higher_equal( _type ) )
1673 return new (phase->C, 3) AndINode(value,phase->intcon(0xFFFF));
1674 // Identity call will handle the case where truncation is not needed.
1675 return LoadNode::Ideal(phase, can_reshape);
1676 }
1677
1678 //--------------------------LoadSNode::Ideal--------------------------------------
1679 //
1680 // If the previous store is to the same address as this load,
1681 // and the value stored was larger than a short, replace this load
1682 // with the value stored truncated to a short. If no truncation is
1683 // needed, the replacement is done in LoadNode::Identity().
1684 //
1685 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1686 Node* mem = in(MemNode::Memory);
1687 Node* value = can_see_stored_value(mem,phase);
1688 if( value && !phase->type(value)->higher_equal( _type ) ) {
1689 Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(16)) );
1690 return new (phase->C, 3) RShiftINode(result, phase->intcon(16));
1691 }
1692 // Identity call will handle the case where truncation is not needed.
1693 return LoadNode::Ideal(phase, can_reshape);
1694 }
1695
1696 //=============================================================================
1697 //----------------------------LoadKlassNode::make------------------------------
1698 // Polymorphic factory method:
1699 Node *LoadKlassNode::make( PhaseGVN& gvn, Node *mem, Node *adr, const TypePtr* at, const TypeKlassPtr *tk ) {
1700 Compile* C = gvn.C;
1701 Node *ctl = NULL;
1702 // sanity check the alias category against the created node type
1703 const TypeOopPtr *adr_type = adr->bottom_type()->isa_oopptr();
1704 assert(adr_type != NULL, "expecting TypeOopPtr");
1705 #ifdef _LP64
1706 if (adr_type->is_ptr_to_narrowoop()) {
1707 Node* load_klass = gvn.transform(new (C, 3) LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowoop()));
1708 return new (C, 2) DecodeNNode(load_klass, load_klass->bottom_type()->make_ptr());
1709 }
1710 #endif
1711 assert(!adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
1712 return new (C, 3) LoadKlassNode(ctl, mem, adr, at, tk);
1713 }
1714
1715 //------------------------------Value------------------------------------------
1716 const Type *LoadKlassNode::Value( PhaseTransform *phase ) const {
1717 return klass_value_common(phase);
1718 }
1719
1720 const Type *LoadNode::klass_value_common( PhaseTransform *phase ) const {
1721 // Either input is TOP ==> the result is TOP
1722 const Type *t1 = phase->type( in(MemNode::Memory) );
1723 if (t1 == Type::TOP) return Type::TOP;
1724 Node *adr = in(MemNode::Address);
1725 const Type *t2 = phase->type( adr );
1726 if (t2 == Type::TOP) return Type::TOP;
1727 const TypePtr *tp = t2->is_ptr();
1728 if (TypePtr::above_centerline(tp->ptr()) ||
1729 tp->ptr() == TypePtr::Null) return Type::TOP;
1730
1731 // Return a more precise klass, if possible
1732 const TypeInstPtr *tinst = tp->isa_instptr();
1733 if (tinst != NULL) {
1734 ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
1735 int offset = tinst->offset();
1736 if (ik == phase->C->env()->Class_klass()
1737 && (offset == java_lang_Class::klass_offset_in_bytes() ||
1738 offset == java_lang_Class::array_klass_offset_in_bytes())) {
1739 // We are loading a special hidden field from a Class mirror object,
1740 // the field which points to the VM's Klass metaobject.
1741 ciType* t = tinst->java_mirror_type();
1742 // java_mirror_type returns non-null for compile-time Class constants.
1743 if (t != NULL) {
1744 // constant oop => constant klass
1745 if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
1746 return TypeKlassPtr::make(ciArrayKlass::make(t));
1747 }
1748 if (!t->is_klass()) {
1749 // a primitive Class (e.g., int.class) has NULL for a klass field
1750 return TypePtr::NULL_PTR;
1751 }
1752 // (Folds up the 1st indirection in aClassConstant.getModifiers().)
1753 return TypeKlassPtr::make(t->as_klass());
1754 }
1755 // non-constant mirror, so we can't tell what's going on
1756 }
1757 if( !ik->is_loaded() )
1758 return _type; // Bail out if not loaded
1759 if (offset == oopDesc::klass_offset_in_bytes()) {
1760 if (tinst->klass_is_exact()) {
1761 return TypeKlassPtr::make(ik);
1762 }
1763 // See if we can become precise: no subklasses and no interface
1764 // (Note: We need to support verified interfaces.)
1765 if (!ik->is_interface() && !ik->has_subklass()) {
1766 //assert(!UseExactTypes, "this code should be useless with exact types");
1767 // Add a dependence; if any subclass added we need to recompile
1768 if (!ik->is_final()) {
1769 // %%% should use stronger assert_unique_concrete_subtype instead
1770 phase->C->dependencies()->assert_leaf_type(ik);
1771 }
1772 // Return precise klass
1773 return TypeKlassPtr::make(ik);
1774 }
1775
1776 // Return root of possible klass
1777 return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
1778 }
1779 }
1780
1781 // Check for loading klass from an array
1782 const TypeAryPtr *tary = tp->isa_aryptr();
1783 if( tary != NULL ) {
1784 ciKlass *tary_klass = tary->klass();
1785 if (tary_klass != NULL // can be NULL when at BOTTOM or TOP
1786 && tary->offset() == oopDesc::klass_offset_in_bytes()) {
1787 if (tary->klass_is_exact()) {
1788 return TypeKlassPtr::make(tary_klass);
1789 }
1790 ciArrayKlass *ak = tary->klass()->as_array_klass();
1791 // If the klass is an object array, we defer the question to the
1792 // array component klass.
1793 if( ak->is_obj_array_klass() ) {
1794 assert( ak->is_loaded(), "" );
1795 ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
1796 if( base_k->is_loaded() && base_k->is_instance_klass() ) {
1797 ciInstanceKlass* ik = base_k->as_instance_klass();
1798 // See if we can become precise: no subklasses and no interface
1799 if (!ik->is_interface() && !ik->has_subklass()) {
1800 //assert(!UseExactTypes, "this code should be useless with exact types");
1801 // Add a dependence; if any subclass added we need to recompile
1802 if (!ik->is_final()) {
1803 phase->C->dependencies()->assert_leaf_type(ik);
1804 }
1805 // Return precise array klass
1806 return TypeKlassPtr::make(ak);
1807 }
1808 }
1809 return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
1810 } else { // Found a type-array?
1811 //assert(!UseExactTypes, "this code should be useless with exact types");
1812 assert( ak->is_type_array_klass(), "" );
1813 return TypeKlassPtr::make(ak); // These are always precise
1814 }
1815 }
1816 }
1817
1818 // Check for loading klass from an array klass
1819 const TypeKlassPtr *tkls = tp->isa_klassptr();
1820 if (tkls != NULL && !StressReflectiveCode) {
1821 ciKlass* klass = tkls->klass();
1822 if( !klass->is_loaded() )
1823 return _type; // Bail out if not loaded
1824 if( klass->is_obj_array_klass() &&
1825 (uint)tkls->offset() == objArrayKlass::element_klass_offset_in_bytes() + sizeof(oopDesc)) {
1826 ciKlass* elem = klass->as_obj_array_klass()->element_klass();
1827 // // Always returning precise element type is incorrect,
1828 // // e.g., element type could be object and array may contain strings
1829 // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
1830
1831 // The array's TypeKlassPtr was declared 'precise' or 'not precise'
1832 // according to the element type's subclassing.
1833 return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
1834 }
1835 if( klass->is_instance_klass() && tkls->klass_is_exact() &&
1836 (uint)tkls->offset() == Klass::super_offset_in_bytes() + sizeof(oopDesc)) {
1837 ciKlass* sup = klass->as_instance_klass()->super();
1838 // The field is Klass::_super. Return its (constant) value.
1839 // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
1840 return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
1841 }
1842 }
1843
1844 // Bailout case
1845 return LoadNode::Value(phase);
1846 }
1847
1848 //------------------------------Identity---------------------------------------
1849 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
1850 // Also feed through the klass in Allocate(...klass...)._klass.
1851 Node* LoadKlassNode::Identity( PhaseTransform *phase ) {
1852 return klass_identity_common(phase);
1853 }
1854
1855 Node* LoadNode::klass_identity_common(PhaseTransform *phase ) {
1856 Node* x = LoadNode::Identity(phase);
1857 if (x != this) return x;
1858
1859 // Take apart the address into an oop and and offset.
1860 // Return 'this' if we cannot.
1861 Node* adr = in(MemNode::Address);
1862 intptr_t offset = 0;
1863 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
1864 if (base == NULL) return this;
1865 const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
1866 if (toop == NULL) return this;
1867
1868 // We can fetch the klass directly through an AllocateNode.
1869 // This works even if the klass is not constant (clone or newArray).
1870 if (offset == oopDesc::klass_offset_in_bytes()) {
1871 Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
1872 if (allocated_klass != NULL) {
1873 return allocated_klass;
1874 }
1875 }
1876
1877 // Simplify k.java_mirror.as_klass to plain k, where k is a klassOop.
1878 // Simplify ak.component_mirror.array_klass to plain ak, ak an arrayKlass.
1879 // See inline_native_Class_query for occurrences of these patterns.
1880 // Java Example: x.getClass().isAssignableFrom(y)
1881 // Java Example: Array.newInstance(x.getClass().getComponentType(), n)
1882 //
1883 // This improves reflective code, often making the Class
1884 // mirror go completely dead. (Current exception: Class
1885 // mirrors may appear in debug info, but we could clean them out by
1886 // introducing a new debug info operator for klassOop.java_mirror).
1887 if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
1888 && (offset == java_lang_Class::klass_offset_in_bytes() ||
1889 offset == java_lang_Class::array_klass_offset_in_bytes())) {
1890 // We are loading a special hidden field from a Class mirror,
1891 // the field which points to its Klass or arrayKlass metaobject.
1892 if (base->is_Load()) {
1893 Node* adr2 = base->in(MemNode::Address);
1894 const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1895 if (tkls != NULL && !tkls->empty()
1896 && (tkls->klass()->is_instance_klass() ||
1897 tkls->klass()->is_array_klass())
1898 && adr2->is_AddP()
1899 ) {
1900 int mirror_field = Klass::java_mirror_offset_in_bytes();
1901 if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
1902 mirror_field = in_bytes(arrayKlass::component_mirror_offset());
1903 }
1904 if (tkls->offset() == mirror_field + (int)sizeof(oopDesc)) {
1905 return adr2->in(AddPNode::Base);
1906 }
1907 }
1908 }
1909 }
1910
1911 return this;
1912 }
1913
1914
1915 //------------------------------Value------------------------------------------
1916 const Type *LoadNKlassNode::Value( PhaseTransform *phase ) const {
1917 const Type *t = klass_value_common(phase);
1918 if (t == Type::TOP)
1919 return t;
1920
1921 return t->make_narrowoop();
1922 }
1923
1924 //------------------------------Identity---------------------------------------
1925 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
1926 // Also feed through the klass in Allocate(...klass...)._klass.
1927 Node* LoadNKlassNode::Identity( PhaseTransform *phase ) {
1928 Node *x = klass_identity_common(phase);
1929
1930 const Type *t = phase->type( x );
1931 if( t == Type::TOP ) return x;
1932 if( t->isa_narrowoop()) return x;
1933
1934 return phase->transform(new (phase->C, 2) EncodePNode(x, t->make_narrowoop()));
1935 }
1936
1937 //------------------------------Value-----------------------------------------
1938 const Type *LoadRangeNode::Value( PhaseTransform *phase ) const {
1939 // Either input is TOP ==> the result is TOP
1940 const Type *t1 = phase->type( in(MemNode::Memory) );
1941 if( t1 == Type::TOP ) return Type::TOP;
1942 Node *adr = in(MemNode::Address);
1943 const Type *t2 = phase->type( adr );
1944 if( t2 == Type::TOP ) return Type::TOP;
1945 const TypePtr *tp = t2->is_ptr();
1946 if (TypePtr::above_centerline(tp->ptr())) return Type::TOP;
1947 const TypeAryPtr *tap = tp->isa_aryptr();
1948 if( !tap ) return _type;
1949 return tap->size();
1950 }
1951
1952 //-------------------------------Ideal---------------------------------------
1953 // Feed through the length in AllocateArray(...length...)._length.
1954 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1955 Node* p = MemNode::Ideal_common(phase, can_reshape);
1956 if (p) return (p == NodeSentinel) ? NULL : p;
1957
1958 // Take apart the address into an oop and and offset.
1959 // Return 'this' if we cannot.
1960 Node* adr = in(MemNode::Address);
1961 intptr_t offset = 0;
1962 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
1963 if (base == NULL) return NULL;
1964 const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
1965 if (tary == NULL) return NULL;
1966
1967 // We can fetch the length directly through an AllocateArrayNode.
1968 // This works even if the length is not constant (clone or newArray).
1969 if (offset == arrayOopDesc::length_offset_in_bytes()) {
1970 AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
1971 if (alloc != NULL) {
1972 Node* allocated_length = alloc->Ideal_length();
1973 Node* len = alloc->make_ideal_length(tary, phase);
1974 if (allocated_length != len) {
1975 // New CastII improves on this.
1976 return len;
1977 }
1978 }
1979 }
1980
1981 return NULL;
1982 }
1983
1984 //------------------------------Identity---------------------------------------
1985 // Feed through the length in AllocateArray(...length...)._length.
1986 Node* LoadRangeNode::Identity( PhaseTransform *phase ) {
1987 Node* x = LoadINode::Identity(phase);
1988 if (x != this) return x;
1989
1990 // Take apart the address into an oop and and offset.
1991 // Return 'this' if we cannot.
1992 Node* adr = in(MemNode::Address);
1993 intptr_t offset = 0;
1994 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
1995 if (base == NULL) return this;
1996 const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
1997 if (tary == NULL) return this;
1998
1999 // We can fetch the length directly through an AllocateArrayNode.
2000 // This works even if the length is not constant (clone or newArray).
2001 if (offset == arrayOopDesc::length_offset_in_bytes()) {
2002 AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2003 if (alloc != NULL) {
2004 Node* allocated_length = alloc->Ideal_length();
2005 // Do not allow make_ideal_length to allocate a CastII node.
2006 Node* len = alloc->make_ideal_length(tary, phase, false);
2007 if (allocated_length == len) {
2008 // Return allocated_length only if it would not be improved by a CastII.
2009 return allocated_length;
2010 }
2011 }
2012 }
2013
2014 return this;
2015
2016 }
2017
2018 //=============================================================================
2019 //---------------------------StoreNode::make-----------------------------------
2020 // Polymorphic factory method:
2021 StoreNode* StoreNode::make( PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt ) {
2022 Compile* C = gvn.C;
2023
2024 switch (bt) {
2025 case T_BOOLEAN:
2026 case T_BYTE: return new (C, 4) StoreBNode(ctl, mem, adr, adr_type, val);
2027 case T_INT: return new (C, 4) StoreINode(ctl, mem, adr, adr_type, val);
2028 case T_CHAR:
2029 case T_SHORT: return new (C, 4) StoreCNode(ctl, mem, adr, adr_type, val);
2030 case T_LONG: return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val);
2031 case T_FLOAT: return new (C, 4) StoreFNode(ctl, mem, adr, adr_type, val);
2032 case T_DOUBLE: return new (C, 4) StoreDNode(ctl, mem, adr, adr_type, val);
2033 case T_ADDRESS:
2034 case T_OBJECT:
2035 #ifdef _LP64
2036 if (adr->bottom_type()->is_ptr_to_narrowoop() ||
2037 (UseCompressedOops && val->bottom_type()->isa_klassptr() &&
2038 adr->bottom_type()->isa_rawptr())) {
2039 val = gvn.transform(new (C, 2) EncodePNode(val, val->bottom_type()->make_narrowoop()));
2040 return new (C, 4) StoreNNode(ctl, mem, adr, adr_type, val);
2041 } else
2042 #endif
2043 {
2044 return new (C, 4) StorePNode(ctl, mem, adr, adr_type, val);
2045 }
2046 }
2047 ShouldNotReachHere();
2048 return (StoreNode*)NULL;
2049 }
2050
2051 StoreLNode* StoreLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val) {
2052 bool require_atomic = true;
2053 return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val, require_atomic);
2054 }
2055
2056
2057 //--------------------------bottom_type----------------------------------------
2058 const Type *StoreNode::bottom_type() const {
2059 return Type::MEMORY;
2060 }
2061
2062 //------------------------------hash-------------------------------------------
2063 uint StoreNode::hash() const {
2064 // unroll addition of interesting fields
2065 //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2066
2067 // Since they are not commoned, do not hash them:
2068 return NO_HASH;
2069 }
2070
2071 //------------------------------Ideal------------------------------------------
2072 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2073 // When a store immediately follows a relevant allocation/initialization,
2074 // try to capture it into the initialization, or hoist it above.
2075 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2076 Node* p = MemNode::Ideal_common(phase, can_reshape);
2077 if (p) return (p == NodeSentinel) ? NULL : p;
2078
2079 Node* mem = in(MemNode::Memory);
2080 Node* address = in(MemNode::Address);
2081
2082 // Back-to-back stores to same address? Fold em up.
2083 // Generally unsafe if I have intervening uses...
2084 if (mem->is_Store() && phase->eqv_uncast(mem->in(MemNode::Address), address)) {
2085 // Looking at a dead closed cycle of memory?
2086 assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2087
2088 assert(Opcode() == mem->Opcode() ||
2089 phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw,
2090 "no mismatched stores, except on raw memory");
2091
2092 if (mem->outcnt() == 1 && // check for intervening uses
2093 mem->as_Store()->memory_size() <= this->memory_size()) {
2094 // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away.
2095 // For example, 'mem' might be the final state at a conditional return.
2096 // Or, 'mem' might be used by some node which is live at the same time
2097 // 'this' is live, which might be unschedulable. So, require exactly
2098 // ONE user, the 'this' store, until such time as we clone 'mem' for
2099 // each of 'mem's uses (thus making the exactly-1-user-rule hold true).
2100 if (can_reshape) { // (%%% is this an anachronism?)
2101 set_req_X(MemNode::Memory, mem->in(MemNode::Memory),
2102 phase->is_IterGVN());
2103 } else {
2104 // It's OK to do this in the parser, since DU info is always accurate,
2105 // and the parser always refers to nodes via SafePointNode maps.
2106 set_req(MemNode::Memory, mem->in(MemNode::Memory));
2107 }
2108 return this;
2109 }
2110 }
2111
2112 // Capture an unaliased, unconditional, simple store into an initializer.
2113 // Or, if it is independent of the allocation, hoist it above the allocation.
2114 if (ReduceFieldZeroing && /*can_reshape &&*/
2115 mem->is_Proj() && mem->in(0)->is_Initialize()) {
2116 InitializeNode* init = mem->in(0)->as_Initialize();
2117 intptr_t offset = init->can_capture_store(this, phase);
2118 if (offset > 0) {
2119 Node* moved = init->capture_store(this, offset, phase);
2120 // If the InitializeNode captured me, it made a raw copy of me,
2121 // and I need to disappear.
2122 if (moved != NULL) {
2123 // %%% hack to ensure that Ideal returns a new node:
2124 mem = MergeMemNode::make(phase->C, mem);
2125 return mem; // fold me away
2126 }
2127 }
2128 }
2129
2130 return NULL; // No further progress
2131 }
2132
2133 //------------------------------Value-----------------------------------------
2134 const Type *StoreNode::Value( PhaseTransform *phase ) const {
2135 // Either input is TOP ==> the result is TOP
2136 const Type *t1 = phase->type( in(MemNode::Memory) );
2137 if( t1 == Type::TOP ) return Type::TOP;
2138 const Type *t2 = phase->type( in(MemNode::Address) );
2139 if( t2 == Type::TOP ) return Type::TOP;
2140 const Type *t3 = phase->type( in(MemNode::ValueIn) );
2141 if( t3 == Type::TOP ) return Type::TOP;
2142 return Type::MEMORY;
2143 }
2144
2145 //------------------------------Identity---------------------------------------
2146 // Remove redundant stores:
2147 // Store(m, p, Load(m, p)) changes to m.
2148 // Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2149 Node *StoreNode::Identity( PhaseTransform *phase ) {
2150 Node* mem = in(MemNode::Memory);
2151 Node* adr = in(MemNode::Address);
2152 Node* val = in(MemNode::ValueIn);
2153
2154 // Load then Store? Then the Store is useless
2155 if (val->is_Load() &&
2156 phase->eqv_uncast( val->in(MemNode::Address), adr ) &&
2157 phase->eqv_uncast( val->in(MemNode::Memory ), mem ) &&
2158 val->as_Load()->store_Opcode() == Opcode()) {
2159 return mem;
2160 }
2161
2162 // Two stores in a row of the same value?
2163 if (mem->is_Store() &&
2164 phase->eqv_uncast( mem->in(MemNode::Address), adr ) &&
2165 phase->eqv_uncast( mem->in(MemNode::ValueIn), val ) &&
2166 mem->Opcode() == Opcode()) {
2167 return mem;
2168 }
2169
2170 // Store of zero anywhere into a freshly-allocated object?
2171 // Then the store is useless.
2172 // (It must already have been captured by the InitializeNode.)
2173 if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2174 // a newly allocated object is already all-zeroes everywhere
2175 if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2176 return mem;
2177 }
2178
2179 // the store may also apply to zero-bits in an earlier object
2180 Node* prev_mem = find_previous_store(phase);
2181 // Steps (a), (b): Walk past independent stores to find an exact match.
2182 if (prev_mem != NULL) {
2183 Node* prev_val = can_see_stored_value(prev_mem, phase);
2184 if (prev_val != NULL && phase->eqv(prev_val, val)) {
2185 // prev_val and val might differ by a cast; it would be good
2186 // to keep the more informative of the two.
2187 return mem;
2188 }
2189 }
2190 }
2191
2192 return this;
2193 }
2194
2195 //------------------------------match_edge-------------------------------------
2196 // Do we Match on this edge index or not? Match only memory & value
2197 uint StoreNode::match_edge(uint idx) const {
2198 return idx == MemNode::Address || idx == MemNode::ValueIn;
2199 }
2200
2201 //------------------------------cmp--------------------------------------------
2202 // Do not common stores up together. They generally have to be split
2203 // back up anyways, so do not bother.
2204 uint StoreNode::cmp( const Node &n ) const {
2205 return (&n == this); // Always fail except on self
2206 }
2207
2208 //------------------------------Ideal_masked_input-----------------------------
2209 // Check for a useless mask before a partial-word store
2210 // (StoreB ... (AndI valIn conIa) )
2211 // If (conIa & mask == mask) this simplifies to
2212 // (StoreB ... (valIn) )
2213 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2214 Node *val = in(MemNode::ValueIn);
2215 if( val->Opcode() == Op_AndI ) {
2216 const TypeInt *t = phase->type( val->in(2) )->isa_int();
2217 if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2218 set_req(MemNode::ValueIn, val->in(1));
2219 return this;
2220 }
2221 }
2222 return NULL;
2223 }
2224
2225
2226 //------------------------------Ideal_sign_extended_input----------------------
2227 // Check for useless sign-extension before a partial-word store
2228 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2229 // If (conIL == conIR && conIR <= num_bits) this simplifies to
2230 // (StoreB ... (valIn) )
2231 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2232 Node *val = in(MemNode::ValueIn);
2233 if( val->Opcode() == Op_RShiftI ) {
2234 const TypeInt *t = phase->type( val->in(2) )->isa_int();
2235 if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2236 Node *shl = val->in(1);
2237 if( shl->Opcode() == Op_LShiftI ) {
2238 const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2239 if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2240 set_req(MemNode::ValueIn, shl->in(1));
2241 return this;
2242 }
2243 }
2244 }
2245 }
2246 return NULL;
2247 }
2248
2249 //------------------------------value_never_loaded-----------------------------------
2250 // Determine whether there are any possible loads of the value stored.
2251 // For simplicity, we actually check if there are any loads from the
2252 // address stored to, not just for loads of the value stored by this node.
2253 //
2254 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2255 Node *adr = in(Address);
2256 const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2257 if (adr_oop == NULL)
2258 return false;
2259 if (!adr_oop->is_known_instance_field())
2260 return false; // if not a distinct instance, there may be aliases of the address
2261 for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2262 Node *use = adr->fast_out(i);
2263 int opc = use->Opcode();
2264 if (use->is_Load() || use->is_LoadStore()) {
2265 return false;
2266 }
2267 }
2268 return true;
2269 }
2270
2271 //=============================================================================
2272 //------------------------------Ideal------------------------------------------
2273 // If the store is from an AND mask that leaves the low bits untouched, then
2274 // we can skip the AND operation. If the store is from a sign-extension
2275 // (a left shift, then right shift) we can skip both.
2276 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2277 Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2278 if( progress != NULL ) return progress;
2279
2280 progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2281 if( progress != NULL ) return progress;
2282
2283 // Finally check the default case
2284 return StoreNode::Ideal(phase, can_reshape);
2285 }
2286
2287 //=============================================================================
2288 //------------------------------Ideal------------------------------------------
2289 // If the store is from an AND mask that leaves the low bits untouched, then
2290 // we can skip the AND operation
2291 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2292 Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2293 if( progress != NULL ) return progress;
2294
2295 progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2296 if( progress != NULL ) return progress;
2297
2298 // Finally check the default case
2299 return StoreNode::Ideal(phase, can_reshape);
2300 }
2301
2302 //=============================================================================
2303 //------------------------------Identity---------------------------------------
2304 Node *StoreCMNode::Identity( PhaseTransform *phase ) {
2305 // No need to card mark when storing a null ptr
2306 Node* my_store = in(MemNode::OopStore);
2307 if (my_store->is_Store()) {
2308 const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2309 if( t1 == TypePtr::NULL_PTR ) {
2310 return in(MemNode::Memory);
2311 }
2312 }
2313
2314 return this;
2315 }
2316
2317 //=============================================================================
2318 //------------------------------Ideal---------------------------------------
2319 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2320 Node* progress = StoreNode::Ideal(phase, can_reshape);
2321 if (progress != NULL) return progress;
2322
2323 Node* my_store = in(MemNode::OopStore);
2324 if (my_store->is_MergeMem()) {
2325 Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2326 if (mem != my_store) {
2327 set_req(MemNode::OopStore, mem);
2328 return this;
2329 }
2330 }
2331
2332 return NULL;
2333 }
2334
2335 //------------------------------Value-----------------------------------------
2336 const Type *StoreCMNode::Value( PhaseTransform *phase ) const {
2337 // Either input is TOP ==> the result is TOP
2338 const Type *t = phase->type( in(MemNode::Memory) );
2339 if( t == Type::TOP ) return Type::TOP;
2340 t = phase->type( in(MemNode::Address) );
2341 if( t == Type::TOP ) return Type::TOP;
2342 t = phase->type( in(MemNode::ValueIn) );
2343 if( t == Type::TOP ) return Type::TOP;
2344 // If extra input is TOP ==> the result is TOP
2345 t = phase->type( in(MemNode::OopStore) );
2346 if( t == Type::TOP ) return Type::TOP;
2347
2348 return StoreNode::Value( phase );
2349 }
2350
2351
2352 //=============================================================================
2353 //----------------------------------SCMemProjNode------------------------------
2354 const Type * SCMemProjNode::Value( PhaseTransform *phase ) const
2355 {
2356 return bottom_type();
2357 }
2358
2359 //=============================================================================
2360 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : Node(5) {
2361 init_req(MemNode::Control, c );
2362 init_req(MemNode::Memory , mem);
2363 init_req(MemNode::Address, adr);
2364 init_req(MemNode::ValueIn, val);
2365 init_req( ExpectedIn, ex );
2366 init_class_id(Class_LoadStore);
2367
2368 }
2369
2370 //=============================================================================
2371 //-------------------------------adr_type--------------------------------------
2372 // Do we Match on this edge index or not? Do not match memory
2373 const TypePtr* ClearArrayNode::adr_type() const {
2374 Node *adr = in(3);
2375 return MemNode::calculate_adr_type(adr->bottom_type());
2376 }
2377
2378 //------------------------------match_edge-------------------------------------
2379 // Do we Match on this edge index or not? Do not match memory
2380 uint ClearArrayNode::match_edge(uint idx) const {
2381 return idx > 1;
2382 }
2383
2384 //------------------------------Identity---------------------------------------
2385 // Clearing a zero length array does nothing
2386 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
2387 return phase->type(in(2))->higher_equal(TypeX::ZERO) ? in(1) : this;
2388 }
2389
2390 //------------------------------Idealize---------------------------------------
2391 // Clearing a short array is faster with stores
2392 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
2393 const int unit = BytesPerLong;
2394 const TypeX* t = phase->type(in(2))->isa_intptr_t();
2395 if (!t) return NULL;
2396 if (!t->is_con()) return NULL;
2397 intptr_t raw_count = t->get_con();
2398 intptr_t size = raw_count;
2399 if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2400 // Clearing nothing uses the Identity call.
2401 // Negative clears are possible on dead ClearArrays
2402 // (see jck test stmt114.stmt11402.val).
2403 if (size <= 0 || size % unit != 0) return NULL;
2404 intptr_t count = size / unit;
2405 // Length too long; use fast hardware clear
2406 if (size > Matcher::init_array_short_size) return NULL;
2407 Node *mem = in(1);
2408 if( phase->type(mem)==Type::TOP ) return NULL;
2409 Node *adr = in(3);
2410 const Type* at = phase->type(adr);
2411 if( at==Type::TOP ) return NULL;
2412 const TypePtr* atp = at->isa_ptr();
2413 // adjust atp to be the correct array element address type
2414 if (atp == NULL) atp = TypePtr::BOTTOM;
2415 else atp = atp->add_offset(Type::OffsetBot);
2416 // Get base for derived pointer purposes
2417 if( adr->Opcode() != Op_AddP ) Unimplemented();
2418 Node *base = adr->in(1);
2419
2420 Node *zero = phase->makecon(TypeLong::ZERO);
2421 Node *off = phase->MakeConX(BytesPerLong);
2422 mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
2423 count--;
2424 while( count-- ) {
2425 mem = phase->transform(mem);
2426 adr = phase->transform(new (phase->C, 4) AddPNode(base,adr,off));
2427 mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
2428 }
2429 return mem;
2430 }
2431
2432 //----------------------------clear_memory-------------------------------------
2433 // Generate code to initialize object storage to zero.
2434 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2435 intptr_t start_offset,
2436 Node* end_offset,
2437 PhaseGVN* phase) {
2438 Compile* C = phase->C;
2439 intptr_t offset = start_offset;
2440
2441 int unit = BytesPerLong;
2442 if ((offset % unit) != 0) {
2443 Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(offset));
2444 adr = phase->transform(adr);
2445 const TypePtr* atp = TypeRawPtr::BOTTOM;
2446 mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
2447 mem = phase->transform(mem);
2448 offset += BytesPerInt;
2449 }
2450 assert((offset % unit) == 0, "");
2451
2452 // Initialize the remaining stuff, if any, with a ClearArray.
2453 return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2454 }
2455
2456 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2457 Node* start_offset,
2458 Node* end_offset,
2459 PhaseGVN* phase) {
2460 if (start_offset == end_offset) {
2461 // nothing to do
2462 return mem;
2463 }
2464
2465 Compile* C = phase->C;
2466 int unit = BytesPerLong;
2467 Node* zbase = start_offset;
2468 Node* zend = end_offset;
2469
2470 // Scale to the unit required by the CPU:
2471 if (!Matcher::init_array_count_is_in_bytes) {
2472 Node* shift = phase->intcon(exact_log2(unit));
2473 zbase = phase->transform( new(C,3) URShiftXNode(zbase, shift) );
2474 zend = phase->transform( new(C,3) URShiftXNode(zend, shift) );
2475 }
2476
2477 Node* zsize = phase->transform( new(C,3) SubXNode(zend, zbase) );
2478 Node* zinit = phase->zerocon((unit == BytesPerLong) ? T_LONG : T_INT);
2479
2480 // Bulk clear double-words
2481 Node* adr = phase->transform( new(C,4) AddPNode(dest, dest, start_offset) );
2482 mem = new (C, 4) ClearArrayNode(ctl, mem, zsize, adr);
2483 return phase->transform(mem);
2484 }
2485
2486 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2487 intptr_t start_offset,
2488 intptr_t end_offset,
2489 PhaseGVN* phase) {
2490 if (start_offset == end_offset) {
2491 // nothing to do
2492 return mem;
2493 }
2494
2495 Compile* C = phase->C;
2496 assert((end_offset % BytesPerInt) == 0, "odd end offset");
2497 intptr_t done_offset = end_offset;
2498 if ((done_offset % BytesPerLong) != 0) {
2499 done_offset -= BytesPerInt;
2500 }
2501 if (done_offset > start_offset) {
2502 mem = clear_memory(ctl, mem, dest,
2503 start_offset, phase->MakeConX(done_offset), phase);
2504 }
2505 if (done_offset < end_offset) { // emit the final 32-bit store
2506 Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(done_offset));
2507 adr = phase->transform(adr);
2508 const TypePtr* atp = TypeRawPtr::BOTTOM;
2509 mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
2510 mem = phase->transform(mem);
2511 done_offset += BytesPerInt;
2512 }
2513 assert(done_offset == end_offset, "");
2514 return mem;
2515 }
2516
2517 //=============================================================================
2518 // Do we match on this edge? No memory edges
2519 uint StrCompNode::match_edge(uint idx) const {
2520 return idx == 5 || idx == 6;
2521 }
2522
2523 //------------------------------Ideal------------------------------------------
2524 // Return a node which is more "ideal" than the current node. Strip out
2525 // control copies
2526 Node *StrCompNode::Ideal(PhaseGVN *phase, bool can_reshape){
2527 return remove_dead_region(phase, can_reshape) ? this : NULL;
2528 }
2529
2530 // Do we match on this edge? No memory edges
2531 uint StrEqualsNode::match_edge(uint idx) const {
2532 return idx == 5 || idx == 6;
2533 }
2534
2535 //------------------------------Ideal------------------------------------------
2536 // Return a node which is more "ideal" than the current node. Strip out
2537 // control copies
2538 Node *StrEqualsNode::Ideal(PhaseGVN *phase, bool can_reshape){
2539 return remove_dead_region(phase, can_reshape) ? this : NULL;
2540 }
2541
2542 //=============================================================================
2543 // Do we match on this edge? No memory edges
2544 uint StrIndexOfNode::match_edge(uint idx) const {
2545 return idx == 5 || idx == 6;
2546 }
2547
2548 //------------------------------Ideal------------------------------------------
2549 // Return a node which is more "ideal" than the current node. Strip out
2550 // control copies
2551 Node *StrIndexOfNode::Ideal(PhaseGVN *phase, bool can_reshape){
2552 return remove_dead_region(phase, can_reshape) ? this : NULL;
2553 }
2554
2555 //------------------------------Ideal------------------------------------------
2556 // Return a node which is more "ideal" than the current node. Strip out
2557 // control copies
2558 Node *AryEqNode::Ideal(PhaseGVN *phase, bool can_reshape){
2559 return remove_dead_region(phase, can_reshape) ? this : NULL;
2560 }
2561
2562 //=============================================================================
2563 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
2564 : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
2565 _adr_type(C->get_adr_type(alias_idx))
2566 {
2567 init_class_id(Class_MemBar);
2568 Node* top = C->top();
2569 init_req(TypeFunc::I_O,top);
2570 init_req(TypeFunc::FramePtr,top);
2571 init_req(TypeFunc::ReturnAdr,top);
2572 if (precedent != NULL)
2573 init_req(TypeFunc::Parms, precedent);
2574 }
2575
2576 //------------------------------cmp--------------------------------------------
2577 uint MemBarNode::hash() const { return NO_HASH; }
2578 uint MemBarNode::cmp( const Node &n ) const {
2579 return (&n == this); // Always fail except on self
2580 }
2581
2582 //------------------------------make-------------------------------------------
2583 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
2584 int len = Precedent + (pn == NULL? 0: 1);
2585 switch (opcode) {
2586 case Op_MemBarAcquire: return new(C, len) MemBarAcquireNode(C, atp, pn);
2587 case Op_MemBarRelease: return new(C, len) MemBarReleaseNode(C, atp, pn);
2588 case Op_MemBarVolatile: return new(C, len) MemBarVolatileNode(C, atp, pn);
2589 case Op_MemBarCPUOrder: return new(C, len) MemBarCPUOrderNode(C, atp, pn);
2590 case Op_Initialize: return new(C, len) InitializeNode(C, atp, pn);
2591 default: ShouldNotReachHere(); return NULL;
2592 }
2593 }
2594
2595 //------------------------------Ideal------------------------------------------
2596 // Return a node which is more "ideal" than the current node. Strip out
2597 // control copies
2598 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2599 return remove_dead_region(phase, can_reshape) ? this : NULL;
2600 }
2601
2602 //------------------------------Value------------------------------------------
2603 const Type *MemBarNode::Value( PhaseTransform *phase ) const {
2604 if( !in(0) ) return Type::TOP;
2605 if( phase->type(in(0)) == Type::TOP )
2606 return Type::TOP;
2607 return TypeTuple::MEMBAR;
2608 }
2609
2610 //------------------------------match------------------------------------------
2611 // Construct projections for memory.
2612 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
2613 switch (proj->_con) {
2614 case TypeFunc::Control:
2615 case TypeFunc::Memory:
2616 return new (m->C, 1) MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
2617 }
2618 ShouldNotReachHere();
2619 return NULL;
2620 }
2621
2622 //===========================InitializeNode====================================
2623 // SUMMARY:
2624 // This node acts as a memory barrier on raw memory, after some raw stores.
2625 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
2626 // The Initialize can 'capture' suitably constrained stores as raw inits.
2627 // It can coalesce related raw stores into larger units (called 'tiles').
2628 // It can avoid zeroing new storage for memory units which have raw inits.
2629 // At macro-expansion, it is marked 'complete', and does not optimize further.
2630 //
2631 // EXAMPLE:
2632 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
2633 // ctl = incoming control; mem* = incoming memory
2634 // (Note: A star * on a memory edge denotes I/O and other standard edges.)
2635 // First allocate uninitialized memory and fill in the header:
2636 // alloc = (Allocate ctl mem* 16 #short[].klass ...)
2637 // ctl := alloc.Control; mem* := alloc.Memory*
2638 // rawmem = alloc.Memory; rawoop = alloc.RawAddress
2639 // Then initialize to zero the non-header parts of the raw memory block:
2640 // init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
2641 // ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
2642 // After the initialize node executes, the object is ready for service:
2643 // oop := (CheckCastPP init.Control alloc.RawAddress #short[])
2644 // Suppose its body is immediately initialized as {1,2}:
2645 // store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
2646 // store2 = (StoreC init.Control store1 (+ oop 14) 2)
2647 // mem.SLICE(#short[*]) := store2
2648 //
2649 // DETAILS:
2650 // An InitializeNode collects and isolates object initialization after
2651 // an AllocateNode and before the next possible safepoint. As a
2652 // memory barrier (MemBarNode), it keeps critical stores from drifting
2653 // down past any safepoint or any publication of the allocation.
2654 // Before this barrier, a newly-allocated object may have uninitialized bits.
2655 // After this barrier, it may be treated as a real oop, and GC is allowed.
2656 //
2657 // The semantics of the InitializeNode include an implicit zeroing of
2658 // the new object from object header to the end of the object.
2659 // (The object header and end are determined by the AllocateNode.)
2660 //
2661 // Certain stores may be added as direct inputs to the InitializeNode.
2662 // These stores must update raw memory, and they must be to addresses
2663 // derived from the raw address produced by AllocateNode, and with
2664 // a constant offset. They must be ordered by increasing offset.
2665 // The first one is at in(RawStores), the last at in(req()-1).
2666 // Unlike most memory operations, they are not linked in a chain,
2667 // but are displayed in parallel as users of the rawmem output of
2668 // the allocation.
2669 //
2670 // (See comments in InitializeNode::capture_store, which continue
2671 // the example given above.)
2672 //
2673 // When the associated Allocate is macro-expanded, the InitializeNode
2674 // may be rewritten to optimize collected stores. A ClearArrayNode
2675 // may also be created at that point to represent any required zeroing.
2676 // The InitializeNode is then marked 'complete', prohibiting further
2677 // capturing of nearby memory operations.
2678 //
2679 // During macro-expansion, all captured initializations which store
2680 // constant values of 32 bits or smaller are coalesced (if advantageous)
2681 // into larger 'tiles' 32 or 64 bits. This allows an object to be
2682 // initialized in fewer memory operations. Memory words which are
2683 // covered by neither tiles nor non-constant stores are pre-zeroed
2684 // by explicit stores of zero. (The code shape happens to do all
2685 // zeroing first, then all other stores, with both sequences occurring
2686 // in order of ascending offsets.)
2687 //
2688 // Alternatively, code may be inserted between an AllocateNode and its
2689 // InitializeNode, to perform arbitrary initialization of the new object.
2690 // E.g., the object copying intrinsics insert complex data transfers here.
2691 // The initialization must then be marked as 'complete' disable the
2692 // built-in zeroing semantics and the collection of initializing stores.
2693 //
2694 // While an InitializeNode is incomplete, reads from the memory state
2695 // produced by it are optimizable if they match the control edge and
2696 // new oop address associated with the allocation/initialization.
2697 // They return a stored value (if the offset matches) or else zero.
2698 // A write to the memory state, if it matches control and address,
2699 // and if it is to a constant offset, may be 'captured' by the
2700 // InitializeNode. It is cloned as a raw memory operation and rewired
2701 // inside the initialization, to the raw oop produced by the allocation.
2702 // Operations on addresses which are provably distinct (e.g., to
2703 // other AllocateNodes) are allowed to bypass the initialization.
2704 //
2705 // The effect of all this is to consolidate object initialization
2706 // (both arrays and non-arrays, both piecewise and bulk) into a
2707 // single location, where it can be optimized as a unit.
2708 //
2709 // Only stores with an offset less than TrackedInitializationLimit words
2710 // will be considered for capture by an InitializeNode. This puts a
2711 // reasonable limit on the complexity of optimized initializations.
2712
2713 //---------------------------InitializeNode------------------------------------
2714 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
2715 : _is_complete(false),
2716 MemBarNode(C, adr_type, rawoop)
2717 {
2718 init_class_id(Class_Initialize);
2719
2720 assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
2721 assert(in(RawAddress) == rawoop, "proper init");
2722 // Note: allocation() can be NULL, for secondary initialization barriers
2723 }
2724
2725 // Since this node is not matched, it will be processed by the
2726 // register allocator. Declare that there are no constraints
2727 // on the allocation of the RawAddress edge.
2728 const RegMask &InitializeNode::in_RegMask(uint idx) const {
2729 // This edge should be set to top, by the set_complete. But be conservative.
2730 if (idx == InitializeNode::RawAddress)
2731 return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
2732 return RegMask::Empty;
2733 }
2734
2735 Node* InitializeNode::memory(uint alias_idx) {
2736 Node* mem = in(Memory);
2737 if (mem->is_MergeMem()) {
2738 return mem->as_MergeMem()->memory_at(alias_idx);
2739 } else {
2740 // incoming raw memory is not split
2741 return mem;
2742 }
2743 }
2744
2745 bool InitializeNode::is_non_zero() {
2746 if (is_complete()) return false;
2747 remove_extra_zeroes();
2748 return (req() > RawStores);
2749 }
2750
2751 void InitializeNode::set_complete(PhaseGVN* phase) {
2752 assert(!is_complete(), "caller responsibility");
2753 _is_complete = true;
2754
2755 // After this node is complete, it contains a bunch of
2756 // raw-memory initializations. There is no need for
2757 // it to have anything to do with non-raw memory effects.
2758 // Therefore, tell all non-raw users to re-optimize themselves,
2759 // after skipping the memory effects of this initialization.
2760 PhaseIterGVN* igvn = phase->is_IterGVN();
2761 if (igvn) igvn->add_users_to_worklist(this);
2762 }
2763
2764 // convenience function
2765 // return false if the init contains any stores already
2766 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
2767 InitializeNode* init = initialization();
2768 if (init == NULL || init->is_complete()) return false;
2769 init->remove_extra_zeroes();
2770 // for now, if this allocation has already collected any inits, bail:
2771 if (init->is_non_zero()) return false;
2772 init->set_complete(phase);
2773 return true;
2774 }
2775
2776 void InitializeNode::remove_extra_zeroes() {
2777 if (req() == RawStores) return;
2778 Node* zmem = zero_memory();
2779 uint fill = RawStores;
2780 for (uint i = fill; i < req(); i++) {
2781 Node* n = in(i);
2782 if (n->is_top() || n == zmem) continue; // skip
2783 if (fill < i) set_req(fill, n); // compact
2784 ++fill;
2785 }
2786 // delete any empty spaces created:
2787 while (fill < req()) {
2788 del_req(fill);
2789 }
2790 }
2791
2792 // Helper for remembering which stores go with which offsets.
2793 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
2794 if (!st->is_Store()) return -1; // can happen to dead code via subsume_node
2795 intptr_t offset = -1;
2796 Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
2797 phase, offset);
2798 if (base == NULL) return -1; // something is dead,
2799 if (offset < 0) return -1; // dead, dead
2800 return offset;
2801 }
2802
2803 // Helper for proving that an initialization expression is
2804 // "simple enough" to be folded into an object initialization.
2805 // Attempts to prove that a store's initial value 'n' can be captured
2806 // within the initialization without creating a vicious cycle, such as:
2807 // { Foo p = new Foo(); p.next = p; }
2808 // True for constants and parameters and small combinations thereof.
2809 bool InitializeNode::detect_init_independence(Node* n,
2810 bool st_is_pinned,
2811 int& count) {
2812 if (n == NULL) return true; // (can this really happen?)
2813 if (n->is_Proj()) n = n->in(0);
2814 if (n == this) return false; // found a cycle
2815 if (n->is_Con()) return true;
2816 if (n->is_Start()) return true; // params, etc., are OK
2817 if (n->is_Root()) return true; // even better
2818
2819 Node* ctl = n->in(0);
2820 if (ctl != NULL && !ctl->is_top()) {
2821 if (ctl->is_Proj()) ctl = ctl->in(0);
2822 if (ctl == this) return false;
2823
2824 // If we already know that the enclosing memory op is pinned right after
2825 // the init, then any control flow that the store has picked up
2826 // must have preceded the init, or else be equal to the init.
2827 // Even after loop optimizations (which might change control edges)
2828 // a store is never pinned *before* the availability of its inputs.
2829 if (!MemNode::all_controls_dominate(n, this))
2830 return false; // failed to prove a good control
2831
2832 }
2833
2834 // Check data edges for possible dependencies on 'this'.
2835 if ((count += 1) > 20) return false; // complexity limit
2836 for (uint i = 1; i < n->req(); i++) {
2837 Node* m = n->in(i);
2838 if (m == NULL || m == n || m->is_top()) continue;
2839 uint first_i = n->find_edge(m);
2840 if (i != first_i) continue; // process duplicate edge just once
2841 if (!detect_init_independence(m, st_is_pinned, count)) {
2842 return false;
2843 }
2844 }
2845
2846 return true;
2847 }
2848
2849 // Here are all the checks a Store must pass before it can be moved into
2850 // an initialization. Returns zero if a check fails.
2851 // On success, returns the (constant) offset to which the store applies,
2852 // within the initialized memory.
2853 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase) {
2854 const int FAIL = 0;
2855 if (st->req() != MemNode::ValueIn + 1)
2856 return FAIL; // an inscrutable StoreNode (card mark?)
2857 Node* ctl = st->in(MemNode::Control);
2858 if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
2859 return FAIL; // must be unconditional after the initialization
2860 Node* mem = st->in(MemNode::Memory);
2861 if (!(mem->is_Proj() && mem->in(0) == this))
2862 return FAIL; // must not be preceded by other stores
2863 Node* adr = st->in(MemNode::Address);
2864 intptr_t offset;
2865 AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
2866 if (alloc == NULL)
2867 return FAIL; // inscrutable address
2868 if (alloc != allocation())
2869 return FAIL; // wrong allocation! (store needs to float up)
2870 Node* val = st->in(MemNode::ValueIn);
2871 int complexity_count = 0;
2872 if (!detect_init_independence(val, true, complexity_count))
2873 return FAIL; // stored value must be 'simple enough'
2874
2875 return offset; // success
2876 }
2877
2878 // Find the captured store in(i) which corresponds to the range
2879 // [start..start+size) in the initialized object.
2880 // If there is one, return its index i. If there isn't, return the
2881 // negative of the index where it should be inserted.
2882 // Return 0 if the queried range overlaps an initialization boundary
2883 // or if dead code is encountered.
2884 // If size_in_bytes is zero, do not bother with overlap checks.
2885 int InitializeNode::captured_store_insertion_point(intptr_t start,
2886 int size_in_bytes,
2887 PhaseTransform* phase) {
2888 const int FAIL = 0, MAX_STORE = BytesPerLong;
2889
2890 if (is_complete())
2891 return FAIL; // arraycopy got here first; punt
2892
2893 assert(allocation() != NULL, "must be present");
2894
2895 // no negatives, no header fields:
2896 if (start < (intptr_t) allocation()->minimum_header_size()) return FAIL;
2897
2898 // after a certain size, we bail out on tracking all the stores:
2899 intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
2900 if (start >= ti_limit) return FAIL;
2901
2902 for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
2903 if (i >= limit) return -(int)i; // not found; here is where to put it
2904
2905 Node* st = in(i);
2906 intptr_t st_off = get_store_offset(st, phase);
2907 if (st_off < 0) {
2908 if (st != zero_memory()) {
2909 return FAIL; // bail out if there is dead garbage
2910 }
2911 } else if (st_off > start) {
2912 // ...we are done, since stores are ordered
2913 if (st_off < start + size_in_bytes) {
2914 return FAIL; // the next store overlaps
2915 }
2916 return -(int)i; // not found; here is where to put it
2917 } else if (st_off < start) {
2918 if (size_in_bytes != 0 &&
2919 start < st_off + MAX_STORE &&
2920 start < st_off + st->as_Store()->memory_size()) {
2921 return FAIL; // the previous store overlaps
2922 }
2923 } else {
2924 if (size_in_bytes != 0 &&
2925 st->as_Store()->memory_size() != size_in_bytes) {
2926 return FAIL; // mismatched store size
2927 }
2928 return i;
2929 }
2930
2931 ++i;
2932 }
2933 }
2934
2935 // Look for a captured store which initializes at the offset 'start'
2936 // with the given size. If there is no such store, and no other
2937 // initialization interferes, then return zero_memory (the memory
2938 // projection of the AllocateNode).
2939 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
2940 PhaseTransform* phase) {
2941 assert(stores_are_sane(phase), "");
2942 int i = captured_store_insertion_point(start, size_in_bytes, phase);
2943 if (i == 0) {
2944 return NULL; // something is dead
2945 } else if (i < 0) {
2946 return zero_memory(); // just primordial zero bits here
2947 } else {
2948 Node* st = in(i); // here is the store at this position
2949 assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
2950 return st;
2951 }
2952 }
2953
2954 // Create, as a raw pointer, an address within my new object at 'offset'.
2955 Node* InitializeNode::make_raw_address(intptr_t offset,
2956 PhaseTransform* phase) {
2957 Node* addr = in(RawAddress);
2958 if (offset != 0) {
2959 Compile* C = phase->C;
2960 addr = phase->transform( new (C, 4) AddPNode(C->top(), addr,
2961 phase->MakeConX(offset)) );
2962 }
2963 return addr;
2964 }
2965
2966 // Clone the given store, converting it into a raw store
2967 // initializing a field or element of my new object.
2968 // Caller is responsible for retiring the original store,
2969 // with subsume_node or the like.
2970 //
2971 // From the example above InitializeNode::InitializeNode,
2972 // here are the old stores to be captured:
2973 // store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
2974 // store2 = (StoreC init.Control store1 (+ oop 14) 2)
2975 //
2976 // Here is the changed code; note the extra edges on init:
2977 // alloc = (Allocate ...)
2978 // rawoop = alloc.RawAddress
2979 // rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
2980 // rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
2981 // init = (Initialize alloc.Control alloc.Memory rawoop
2982 // rawstore1 rawstore2)
2983 //
2984 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
2985 PhaseTransform* phase) {
2986 assert(stores_are_sane(phase), "");
2987
2988 if (start < 0) return NULL;
2989 assert(can_capture_store(st, phase) == start, "sanity");
2990
2991 Compile* C = phase->C;
2992 int size_in_bytes = st->memory_size();
2993 int i = captured_store_insertion_point(start, size_in_bytes, phase);
2994 if (i == 0) return NULL; // bail out
2995 Node* prev_mem = NULL; // raw memory for the captured store
2996 if (i > 0) {
2997 prev_mem = in(i); // there is a pre-existing store under this one
2998 set_req(i, C->top()); // temporarily disconnect it
2999 // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3000 } else {
3001 i = -i; // no pre-existing store
3002 prev_mem = zero_memory(); // a slice of the newly allocated object
3003 if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3004 set_req(--i, C->top()); // reuse this edge; it has been folded away
3005 else
3006 ins_req(i, C->top()); // build a new edge
3007 }
3008 Node* new_st = st->clone();
3009 new_st->set_req(MemNode::Control, in(Control));
3010 new_st->set_req(MemNode::Memory, prev_mem);
3011 new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3012 new_st = phase->transform(new_st);
3013
3014 // At this point, new_st might have swallowed a pre-existing store
3015 // at the same offset, or perhaps new_st might have disappeared,
3016 // if it redundantly stored the same value (or zero to fresh memory).
3017
3018 // In any case, wire it in:
3019 set_req(i, new_st);
3020
3021 // The caller may now kill the old guy.
3022 DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3023 assert(check_st == new_st || check_st == NULL, "must be findable");
3024 assert(!is_complete(), "");
3025 return new_st;
3026 }
3027
3028 static bool store_constant(jlong* tiles, int num_tiles,
3029 intptr_t st_off, int st_size,
3030 jlong con) {
3031 if ((st_off & (st_size-1)) != 0)
3032 return false; // strange store offset (assume size==2**N)
3033 address addr = (address)tiles + st_off;
3034 assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3035 switch (st_size) {
3036 case sizeof(jbyte): *(jbyte*) addr = (jbyte) con; break;
3037 case sizeof(jchar): *(jchar*) addr = (jchar) con; break;
3038 case sizeof(jint): *(jint*) addr = (jint) con; break;
3039 case sizeof(jlong): *(jlong*) addr = (jlong) con; break;
3040 default: return false; // strange store size (detect size!=2**N here)
3041 }
3042 return true; // return success to caller
3043 }
3044
3045 // Coalesce subword constants into int constants and possibly
3046 // into long constants. The goal, if the CPU permits,
3047 // is to initialize the object with a small number of 64-bit tiles.
3048 // Also, convert floating-point constants to bit patterns.
3049 // Non-constants are not relevant to this pass.
3050 //
3051 // In terms of the running example on InitializeNode::InitializeNode
3052 // and InitializeNode::capture_store, here is the transformation
3053 // of rawstore1 and rawstore2 into rawstore12:
3054 // alloc = (Allocate ...)
3055 // rawoop = alloc.RawAddress
3056 // tile12 = 0x00010002
3057 // rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3058 // init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3059 //
3060 void
3061 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3062 Node* size_in_bytes,
3063 PhaseGVN* phase) {
3064 Compile* C = phase->C;
3065
3066 assert(stores_are_sane(phase), "");
3067 // Note: After this pass, they are not completely sane,
3068 // since there may be some overlaps.
3069
3070 int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3071
3072 intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3073 intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3074 size_limit = MIN2(size_limit, ti_limit);
3075 size_limit = align_size_up(size_limit, BytesPerLong);
3076 int num_tiles = size_limit / BytesPerLong;
3077
3078 // allocate space for the tile map:
3079 const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3080 jlong tiles_buf[small_len];
3081 Node* nodes_buf[small_len];
3082 jlong inits_buf[small_len];
3083 jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3084 : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3085 Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3086 : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3087 jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3088 : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3089 // tiles: exact bitwise model of all primitive constants
3090 // nodes: last constant-storing node subsumed into the tiles model
3091 // inits: which bytes (in each tile) are touched by any initializations
3092
3093 //// Pass A: Fill in the tile model with any relevant stores.
3094
3095 Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3096 Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3097 Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3098 Node* zmem = zero_memory(); // initially zero memory state
3099 for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3100 Node* st = in(i);
3101 intptr_t st_off = get_store_offset(st, phase);
3102
3103 // Figure out the store's offset and constant value:
3104 if (st_off < header_size) continue; //skip (ignore header)
3105 if (st->in(MemNode::Memory) != zmem) continue; //skip (odd store chain)
3106 int st_size = st->as_Store()->memory_size();
3107 if (st_off + st_size > size_limit) break;
3108
3109 // Record which bytes are touched, whether by constant or not.
3110 if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3111 continue; // skip (strange store size)
3112
3113 const Type* val = phase->type(st->in(MemNode::ValueIn));
3114 if (!val->singleton()) continue; //skip (non-con store)
3115 BasicType type = val->basic_type();
3116
3117 jlong con = 0;
3118 switch (type) {
3119 case T_INT: con = val->is_int()->get_con(); break;
3120 case T_LONG: con = val->is_long()->get_con(); break;
3121 case T_FLOAT: con = jint_cast(val->getf()); break;
3122 case T_DOUBLE: con = jlong_cast(val->getd()); break;
3123 default: continue; //skip (odd store type)
3124 }
3125
3126 if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3127 st->Opcode() == Op_StoreL) {
3128 continue; // This StoreL is already optimal.
3129 }
3130
3131 // Store down the constant.
3132 store_constant(tiles, num_tiles, st_off, st_size, con);
3133
3134 intptr_t j = st_off >> LogBytesPerLong;
3135
3136 if (type == T_INT && st_size == BytesPerInt
3137 && (st_off & BytesPerInt) == BytesPerInt) {
3138 jlong lcon = tiles[j];
3139 if (!Matcher::isSimpleConstant64(lcon) &&
3140 st->Opcode() == Op_StoreI) {
3141 // This StoreI is already optimal by itself.
3142 jint* intcon = (jint*) &tiles[j];
3143 intcon[1] = 0; // undo the store_constant()
3144
3145 // If the previous store is also optimal by itself, back up and
3146 // undo the action of the previous loop iteration... if we can.
3147 // But if we can't, just let the previous half take care of itself.
3148 st = nodes[j];
3149 st_off -= BytesPerInt;
3150 con = intcon[0];
3151 if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3152 assert(st_off >= header_size, "still ignoring header");
3153 assert(get_store_offset(st, phase) == st_off, "must be");
3154 assert(in(i-1) == zmem, "must be");
3155 DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3156 assert(con == tcon->is_int()->get_con(), "must be");
3157 // Undo the effects of the previous loop trip, which swallowed st:
3158 intcon[0] = 0; // undo store_constant()
3159 set_req(i-1, st); // undo set_req(i, zmem)
3160 nodes[j] = NULL; // undo nodes[j] = st
3161 --old_subword; // undo ++old_subword
3162 }
3163 continue; // This StoreI is already optimal.
3164 }
3165 }
3166
3167 // This store is not needed.
3168 set_req(i, zmem);
3169 nodes[j] = st; // record for the moment
3170 if (st_size < BytesPerLong) // something has changed
3171 ++old_subword; // includes int/float, but who's counting...
3172 else ++old_long;
3173 }
3174
3175 if ((old_subword + old_long) == 0)
3176 return; // nothing more to do
3177
3178 //// Pass B: Convert any non-zero tiles into optimal constant stores.
3179 // Be sure to insert them before overlapping non-constant stores.
3180 // (E.g., byte[] x = { 1,2,y,4 } => x[int 0] = 0x01020004, x[2]=y.)
3181 for (int j = 0; j < num_tiles; j++) {
3182 jlong con = tiles[j];
3183 jlong init = inits[j];
3184 if (con == 0) continue;
3185 jint con0, con1; // split the constant, address-wise
3186 jint init0, init1; // split the init map, address-wise
3187 { union { jlong con; jint intcon[2]; } u;
3188 u.con = con;
3189 con0 = u.intcon[0];
3190 con1 = u.intcon[1];
3191 u.con = init;
3192 init0 = u.intcon[0];
3193 init1 = u.intcon[1];
3194 }
3195
3196 Node* old = nodes[j];
3197 assert(old != NULL, "need the prior store");
3198 intptr_t offset = (j * BytesPerLong);
3199
3200 bool split = !Matcher::isSimpleConstant64(con);
3201
3202 if (offset < header_size) {
3203 assert(offset + BytesPerInt >= header_size, "second int counts");
3204 assert(*(jint*)&tiles[j] == 0, "junk in header");
3205 split = true; // only the second word counts
3206 // Example: int a[] = { 42 ... }
3207 } else if (con0 == 0 && init0 == -1) {
3208 split = true; // first word is covered by full inits
3209 // Example: int a[] = { ... foo(), 42 ... }
3210 } else if (con1 == 0 && init1 == -1) {
3211 split = true; // second word is covered by full inits
3212 // Example: int a[] = { ... 42, foo() ... }
3213 }
3214
3215 // Here's a case where init0 is neither 0 nor -1:
3216 // byte a[] = { ... 0,0,foo(),0, 0,0,0,42 ... }
3217 // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3218 // In this case the tile is not split; it is (jlong)42.
3219 // The big tile is stored down, and then the foo() value is inserted.
3220 // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3221
3222 Node* ctl = old->in(MemNode::Control);
3223 Node* adr = make_raw_address(offset, phase);
3224 const TypePtr* atp = TypeRawPtr::BOTTOM;
3225
3226 // One or two coalesced stores to plop down.
3227 Node* st[2];
3228 intptr_t off[2];
3229 int nst = 0;
3230 if (!split) {
3231 ++new_long;
3232 off[nst] = offset;
3233 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3234 phase->longcon(con), T_LONG);
3235 } else {
3236 // Omit either if it is a zero.
3237 if (con0 != 0) {
3238 ++new_int;
3239 off[nst] = offset;
3240 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3241 phase->intcon(con0), T_INT);
3242 }
3243 if (con1 != 0) {
3244 ++new_int;
3245 offset += BytesPerInt;
3246 adr = make_raw_address(offset, phase);
3247 off[nst] = offset;
3248 st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3249 phase->intcon(con1), T_INT);
3250 }
3251 }
3252
3253 // Insert second store first, then the first before the second.
3254 // Insert each one just before any overlapping non-constant stores.
3255 while (nst > 0) {
3256 Node* st1 = st[--nst];
3257 C->copy_node_notes_to(st1, old);
3258 st1 = phase->transform(st1);
3259 offset = off[nst];
3260 assert(offset >= header_size, "do not smash header");
3261 int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
3262 guarantee(ins_idx != 0, "must re-insert constant store");
3263 if (ins_idx < 0) ins_idx = -ins_idx; // never overlap
3264 if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
3265 set_req(--ins_idx, st1);
3266 else
3267 ins_req(ins_idx, st1);
3268 }
3269 }
3270
3271 if (PrintCompilation && WizardMode)
3272 tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
3273 old_subword, old_long, new_int, new_long);
3274 if (C->log() != NULL)
3275 C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
3276 old_subword, old_long, new_int, new_long);
3277
3278 // Clean up any remaining occurrences of zmem:
3279 remove_extra_zeroes();
3280 }
3281
3282 // Explore forward from in(start) to find the first fully initialized
3283 // word, and return its offset. Skip groups of subword stores which
3284 // together initialize full words. If in(start) is itself part of a
3285 // fully initialized word, return the offset of in(start). If there
3286 // are no following full-word stores, or if something is fishy, return
3287 // a negative value.
3288 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
3289 int int_map = 0;
3290 intptr_t int_map_off = 0;
3291 const int FULL_MAP = right_n_bits(BytesPerInt); // the int_map we hope for
3292
3293 for (uint i = start, limit = req(); i < limit; i++) {
3294 Node* st = in(i);
3295
3296 intptr_t st_off = get_store_offset(st, phase);
3297 if (st_off < 0) break; // return conservative answer
3298
3299 int st_size = st->as_Store()->memory_size();
3300 if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
3301 return st_off; // we found a complete word init
3302 }
3303
3304 // update the map:
3305
3306 intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
3307 if (this_int_off != int_map_off) {
3308 // reset the map:
3309 int_map = 0;
3310 int_map_off = this_int_off;
3311 }
3312
3313 int subword_off = st_off - this_int_off;
3314 int_map |= right_n_bits(st_size) << subword_off;
3315 if ((int_map & FULL_MAP) == FULL_MAP) {
3316 return this_int_off; // we found a complete word init
3317 }
3318
3319 // Did this store hit or cross the word boundary?
3320 intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
3321 if (next_int_off == this_int_off + BytesPerInt) {
3322 // We passed the current int, without fully initializing it.
3323 int_map_off = next_int_off;
3324 int_map >>= BytesPerInt;
3325 } else if (next_int_off > this_int_off + BytesPerInt) {
3326 // We passed the current and next int.
3327 return this_int_off + BytesPerInt;
3328 }
3329 }
3330
3331 return -1;
3332 }
3333
3334
3335 // Called when the associated AllocateNode is expanded into CFG.
3336 // At this point, we may perform additional optimizations.
3337 // Linearize the stores by ascending offset, to make memory
3338 // activity as coherent as possible.
3339 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
3340 intptr_t header_size,
3341 Node* size_in_bytes,
3342 PhaseGVN* phase) {
3343 assert(!is_complete(), "not already complete");
3344 assert(stores_are_sane(phase), "");
3345 assert(allocation() != NULL, "must be present");
3346
3347 remove_extra_zeroes();
3348
3349 if (ReduceFieldZeroing || ReduceBulkZeroing)
3350 // reduce instruction count for common initialization patterns
3351 coalesce_subword_stores(header_size, size_in_bytes, phase);
3352
3353 Node* zmem = zero_memory(); // initially zero memory state
3354 Node* inits = zmem; // accumulating a linearized chain of inits
3355 #ifdef ASSERT
3356 intptr_t first_offset = allocation()->minimum_header_size();
3357 intptr_t last_init_off = first_offset; // previous init offset
3358 intptr_t last_init_end = first_offset; // previous init offset+size
3359 intptr_t last_tile_end = first_offset; // previous tile offset+size
3360 #endif
3361 intptr_t zeroes_done = header_size;
3362
3363 bool do_zeroing = true; // we might give up if inits are very sparse
3364 int big_init_gaps = 0; // how many large gaps have we seen?
3365
3366 if (ZeroTLAB) do_zeroing = false;
3367 if (!ReduceFieldZeroing && !ReduceBulkZeroing) do_zeroing = false;
3368
3369 for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3370 Node* st = in(i);
3371 intptr_t st_off = get_store_offset(st, phase);
3372 if (st_off < 0)
3373 break; // unknown junk in the inits
3374 if (st->in(MemNode::Memory) != zmem)
3375 break; // complicated store chains somehow in list
3376
3377 int st_size = st->as_Store()->memory_size();
3378 intptr_t next_init_off = st_off + st_size;
3379
3380 if (do_zeroing && zeroes_done < next_init_off) {
3381 // See if this store needs a zero before it or under it.
3382 intptr_t zeroes_needed = st_off;
3383
3384 if (st_size < BytesPerInt) {
3385 // Look for subword stores which only partially initialize words.
3386 // If we find some, we must lay down some word-level zeroes first,
3387 // underneath the subword stores.
3388 //
3389 // Examples:
3390 // byte[] a = { p,q,r,s } => a[0]=p,a[1]=q,a[2]=r,a[3]=s
3391 // byte[] a = { x,y,0,0 } => a[0..3] = 0, a[0]=x,a[1]=y
3392 // byte[] a = { 0,0,z,0 } => a[0..3] = 0, a[2]=z
3393 //
3394 // Note: coalesce_subword_stores may have already done this,
3395 // if it was prompted by constant non-zero subword initializers.
3396 // But this case can still arise with non-constant stores.
3397
3398 intptr_t next_full_store = find_next_fullword_store(i, phase);
3399
3400 // In the examples above:
3401 // in(i) p q r s x y z
3402 // st_off 12 13 14 15 12 13 14
3403 // st_size 1 1 1 1 1 1 1
3404 // next_full_s. 12 16 16 16 16 16 16
3405 // z's_done 12 16 16 16 12 16 12
3406 // z's_needed 12 16 16 16 16 16 16
3407 // zsize 0 0 0 0 4 0 4
3408 if (next_full_store < 0) {
3409 // Conservative tack: Zero to end of current word.
3410 zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
3411 } else {
3412 // Zero to beginning of next fully initialized word.
3413 // Or, don't zero at all, if we are already in that word.
3414 assert(next_full_store >= zeroes_needed, "must go forward");
3415 assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
3416 zeroes_needed = next_full_store;
3417 }
3418 }
3419
3420 if (zeroes_needed > zeroes_done) {
3421 intptr_t zsize = zeroes_needed - zeroes_done;
3422 // Do some incremental zeroing on rawmem, in parallel with inits.
3423 zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3424 rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3425 zeroes_done, zeroes_needed,
3426 phase);
3427 zeroes_done = zeroes_needed;
3428 if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
3429 do_zeroing = false; // leave the hole, next time
3430 }
3431 }
3432
3433 // Collect the store and move on:
3434 st->set_req(MemNode::Memory, inits);
3435 inits = st; // put it on the linearized chain
3436 set_req(i, zmem); // unhook from previous position
3437
3438 if (zeroes_done == st_off)
3439 zeroes_done = next_init_off;
3440
3441 assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
3442
3443 #ifdef ASSERT
3444 // Various order invariants. Weaker than stores_are_sane because
3445 // a large constant tile can be filled in by smaller non-constant stores.
3446 assert(st_off >= last_init_off, "inits do not reverse");
3447 last_init_off = st_off;
3448 const Type* val = NULL;
3449 if (st_size >= BytesPerInt &&
3450 (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
3451 (int)val->basic_type() < (int)T_OBJECT) {
3452 assert(st_off >= last_tile_end, "tiles do not overlap");
3453 assert(st_off >= last_init_end, "tiles do not overwrite inits");
3454 last_tile_end = MAX2(last_tile_end, next_init_off);
3455 } else {
3456 intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
3457 assert(st_tile_end >= last_tile_end, "inits stay with tiles");
3458 assert(st_off >= last_init_end, "inits do not overlap");
3459 last_init_end = next_init_off; // it's a non-tile
3460 }
3461 #endif //ASSERT
3462 }
3463
3464 remove_extra_zeroes(); // clear out all the zmems left over
3465 add_req(inits);
3466
3467 if (!ZeroTLAB) {
3468 // If anything remains to be zeroed, zero it all now.
3469 zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3470 // if it is the last unused 4 bytes of an instance, forget about it
3471 intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
3472 if (zeroes_done + BytesPerLong >= size_limit) {
3473 assert(allocation() != NULL, "");
3474 Node* klass_node = allocation()->in(AllocateNode::KlassNode);
3475 ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
3476 if (zeroes_done == k->layout_helper())
3477 zeroes_done = size_limit;
3478 }
3479 if (zeroes_done < size_limit) {
3480 rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3481 zeroes_done, size_in_bytes, phase);
3482 }
3483 }
3484
3485 set_complete(phase);
3486 return rawmem;
3487 }
3488
3489
3490 #ifdef ASSERT
3491 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
3492 if (is_complete())
3493 return true; // stores could be anything at this point
3494 assert(allocation() != NULL, "must be present");
3495 intptr_t last_off = allocation()->minimum_header_size();
3496 for (uint i = InitializeNode::RawStores; i < req(); i++) {
3497 Node* st = in(i);
3498 intptr_t st_off = get_store_offset(st, phase);
3499 if (st_off < 0) continue; // ignore dead garbage
3500 if (last_off > st_off) {
3501 tty->print_cr("*** bad store offset at %d: %d > %d", i, last_off, st_off);
3502 this->dump(2);
3503 assert(false, "ascending store offsets");
3504 return false;
3505 }
3506 last_off = st_off + st->as_Store()->memory_size();
3507 }
3508 return true;
3509 }
3510 #endif //ASSERT
3511
3512
3513
3514
3515 //============================MergeMemNode=====================================
3516 //
3517 // SEMANTICS OF MEMORY MERGES: A MergeMem is a memory state assembled from several
3518 // contributing store or call operations. Each contributor provides the memory
3519 // state for a particular "alias type" (see Compile::alias_type). For example,
3520 // if a MergeMem has an input X for alias category #6, then any memory reference
3521 // to alias category #6 may use X as its memory state input, as an exact equivalent
3522 // to using the MergeMem as a whole.
3523 // Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
3524 //
3525 // (Here, the <N> notation gives the index of the relevant adr_type.)
3526 //
3527 // In one special case (and more cases in the future), alias categories overlap.
3528 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
3529 // states. Therefore, if a MergeMem has only one contributing input W for Bot,
3530 // it is exactly equivalent to that state W:
3531 // MergeMem(<Bot>: W) <==> W
3532 //
3533 // Usually, the merge has more than one input. In that case, where inputs
3534 // overlap (i.e., one is Bot), the narrower alias type determines the memory
3535 // state for that type, and the wider alias type (Bot) fills in everywhere else:
3536 // Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
3537 // Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
3538 //
3539 // A merge can take a "wide" memory state as one of its narrow inputs.
3540 // This simply means that the merge observes out only the relevant parts of
3541 // the wide input. That is, wide memory states arriving at narrow merge inputs
3542 // are implicitly "filtered" or "sliced" as necessary. (This is rare.)
3543 //
3544 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
3545 // and that memory slices "leak through":
3546 // MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
3547 //
3548 // But, in such a cascade, repeated memory slices can "block the leak":
3549 // MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
3550 //
3551 // In the last example, Y is not part of the combined memory state of the
3552 // outermost MergeMem. The system must, of course, prevent unschedulable
3553 // memory states from arising, so you can be sure that the state Y is somehow
3554 // a precursor to state Y'.
3555 //
3556 //
3557 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
3558 // of each MergeMemNode array are exactly the numerical alias indexes, including
3559 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw. The functions
3560 // Compile::alias_type (and kin) produce and manage these indexes.
3561 //
3562 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
3563 // (Note that this provides quick access to the top node inside MergeMem methods,
3564 // without the need to reach out via TLS to Compile::current.)
3565 //
3566 // As a consequence of what was just described, a MergeMem that represents a full
3567 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
3568 // containing all alias categories.
3569 //
3570 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
3571 //
3572 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
3573 // a memory state for the alias type <N>, or else the top node, meaning that
3574 // there is no particular input for that alias type. Note that the length of
3575 // a MergeMem is variable, and may be extended at any time to accommodate new
3576 // memory states at larger alias indexes. When merges grow, they are of course
3577 // filled with "top" in the unused in() positions.
3578 //
3579 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
3580 // (Top was chosen because it works smoothly with passes like GCM.)
3581 //
3582 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM. (It is
3583 // the type of random VM bits like TLS references.) Since it is always the
3584 // first non-Bot memory slice, some low-level loops use it to initialize an
3585 // index variable: for (i = AliasIdxRaw; i < req(); i++).
3586 //
3587 //
3588 // ACCESSORS: There is a special accessor MergeMemNode::base_memory which returns
3589 // the distinguished "wide" state. The accessor MergeMemNode::memory_at(N) returns
3590 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
3591 // it returns the base memory. To prevent bugs, memory_at does not accept <Top>
3592 // or <Bot> indexes. The iterator MergeMemStream provides robust iteration over
3593 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
3594 //
3595 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
3596 // really that different from the other memory inputs. An abbreviation called
3597 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
3598 //
3599 //
3600 // PARTIAL MEMORY STATES: During optimization, MergeMem nodes may arise that represent
3601 // partial memory states. When a Phi splits through a MergeMem, the copy of the Phi
3602 // that "emerges though" the base memory will be marked as excluding the alias types
3603 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
3604 //
3605 // Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
3606 // ==Ideal=> MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
3607 //
3608 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
3609 // (It is currently unimplemented.) As you can see, the resulting merge is
3610 // actually a disjoint union of memory states, rather than an overlay.
3611 //
3612
3613 //------------------------------MergeMemNode-----------------------------------
3614 Node* MergeMemNode::make_empty_memory() {
3615 Node* empty_memory = (Node*) Compile::current()->top();
3616 assert(empty_memory->is_top(), "correct sentinel identity");
3617 return empty_memory;
3618 }
3619
3620 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
3621 init_class_id(Class_MergeMem);
3622 // all inputs are nullified in Node::Node(int)
3623 // set_input(0, NULL); // no control input
3624
3625 // Initialize the edges uniformly to top, for starters.
3626 Node* empty_mem = make_empty_memory();
3627 for (uint i = Compile::AliasIdxTop; i < req(); i++) {
3628 init_req(i,empty_mem);
3629 }
3630 assert(empty_memory() == empty_mem, "");
3631
3632 if( new_base != NULL && new_base->is_MergeMem() ) {
3633 MergeMemNode* mdef = new_base->as_MergeMem();
3634 assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
3635 for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
3636 mms.set_memory(mms.memory2());
3637 }
3638 assert(base_memory() == mdef->base_memory(), "");
3639 } else {
3640 set_base_memory(new_base);
3641 }
3642 }
3643
3644 // Make a new, untransformed MergeMem with the same base as 'mem'.
3645 // If mem is itself a MergeMem, populate the result with the same edges.
3646 MergeMemNode* MergeMemNode::make(Compile* C, Node* mem) {
3647 return new(C, 1+Compile::AliasIdxRaw) MergeMemNode(mem);
3648 }
3649
3650 //------------------------------cmp--------------------------------------------
3651 uint MergeMemNode::hash() const { return NO_HASH; }
3652 uint MergeMemNode::cmp( const Node &n ) const {
3653 return (&n == this); // Always fail except on self
3654 }
3655
3656 //------------------------------Identity---------------------------------------
3657 Node* MergeMemNode::Identity(PhaseTransform *phase) {
3658 // Identity if this merge point does not record any interesting memory
3659 // disambiguations.
3660 Node* base_mem = base_memory();
3661 Node* empty_mem = empty_memory();
3662 if (base_mem != empty_mem) { // Memory path is not dead?
3663 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3664 Node* mem = in(i);
3665 if (mem != empty_mem && mem != base_mem) {
3666 return this; // Many memory splits; no change
3667 }
3668 }
3669 }
3670 return base_mem; // No memory splits; ID on the one true input
3671 }
3672
3673 //------------------------------Ideal------------------------------------------
3674 // This method is invoked recursively on chains of MergeMem nodes
3675 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3676 // Remove chain'd MergeMems
3677 //
3678 // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
3679 // relative to the "in(Bot)". Since we are patching both at the same time,
3680 // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
3681 // but rewrite each "in(i)" relative to the new "in(Bot)".
3682 Node *progress = NULL;
3683
3684
3685 Node* old_base = base_memory();
3686 Node* empty_mem = empty_memory();
3687 if (old_base == empty_mem)
3688 return NULL; // Dead memory path.
3689
3690 MergeMemNode* old_mbase;
3691 if (old_base != NULL && old_base->is_MergeMem())
3692 old_mbase = old_base->as_MergeMem();
3693 else
3694 old_mbase = NULL;
3695 Node* new_base = old_base;
3696
3697 // simplify stacked MergeMems in base memory
3698 if (old_mbase) new_base = old_mbase->base_memory();
3699
3700 // the base memory might contribute new slices beyond my req()
3701 if (old_mbase) grow_to_match(old_mbase);
3702
3703 // Look carefully at the base node if it is a phi.
3704 PhiNode* phi_base;
3705 if (new_base != NULL && new_base->is_Phi())
3706 phi_base = new_base->as_Phi();
3707 else
3708 phi_base = NULL;
3709
3710 Node* phi_reg = NULL;
3711 uint phi_len = (uint)-1;
3712 if (phi_base != NULL && !phi_base->is_copy()) {
3713 // do not examine phi if degraded to a copy
3714 phi_reg = phi_base->region();
3715 phi_len = phi_base->req();
3716 // see if the phi is unfinished
3717 for (uint i = 1; i < phi_len; i++) {
3718 if (phi_base->in(i) == NULL) {
3719 // incomplete phi; do not look at it yet!
3720 phi_reg = NULL;
3721 phi_len = (uint)-1;
3722 break;
3723 }
3724 }
3725 }
3726
3727 // Note: We do not call verify_sparse on entry, because inputs
3728 // can normalize to the base_memory via subsume_node or similar
3729 // mechanisms. This method repairs that damage.
3730
3731 assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
3732
3733 // Look at each slice.
3734 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3735 Node* old_in = in(i);
3736 // calculate the old memory value
3737 Node* old_mem = old_in;
3738 if (old_mem == empty_mem) old_mem = old_base;
3739 assert(old_mem == memory_at(i), "");
3740
3741 // maybe update (reslice) the old memory value
3742
3743 // simplify stacked MergeMems
3744 Node* new_mem = old_mem;
3745 MergeMemNode* old_mmem;
3746 if (old_mem != NULL && old_mem->is_MergeMem())
3747 old_mmem = old_mem->as_MergeMem();
3748 else
3749 old_mmem = NULL;
3750 if (old_mmem == this) {
3751 // This can happen if loops break up and safepoints disappear.
3752 // A merge of BotPtr (default) with a RawPtr memory derived from a
3753 // safepoint can be rewritten to a merge of the same BotPtr with
3754 // the BotPtr phi coming into the loop. If that phi disappears
3755 // also, we can end up with a self-loop of the mergemem.
3756 // In general, if loops degenerate and memory effects disappear,
3757 // a mergemem can be left looking at itself. This simply means
3758 // that the mergemem's default should be used, since there is
3759 // no longer any apparent effect on this slice.
3760 // Note: If a memory slice is a MergeMem cycle, it is unreachable
3761 // from start. Update the input to TOP.
3762 new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
3763 }
3764 else if (old_mmem != NULL) {
3765 new_mem = old_mmem->memory_at(i);
3766 }
3767 // else preceding memory was not a MergeMem
3768
3769 // replace equivalent phis (unfortunately, they do not GVN together)
3770 if (new_mem != NULL && new_mem != new_base &&
3771 new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
3772 if (new_mem->is_Phi()) {
3773 PhiNode* phi_mem = new_mem->as_Phi();
3774 for (uint i = 1; i < phi_len; i++) {
3775 if (phi_base->in(i) != phi_mem->in(i)) {
3776 phi_mem = NULL;
3777 break;
3778 }
3779 }
3780 if (phi_mem != NULL) {
3781 // equivalent phi nodes; revert to the def
3782 new_mem = new_base;
3783 }
3784 }
3785 }
3786
3787 // maybe store down a new value
3788 Node* new_in = new_mem;
3789 if (new_in == new_base) new_in = empty_mem;
3790
3791 if (new_in != old_in) {
3792 // Warning: Do not combine this "if" with the previous "if"
3793 // A memory slice might have be be rewritten even if it is semantically
3794 // unchanged, if the base_memory value has changed.
3795 set_req(i, new_in);
3796 progress = this; // Report progress
3797 }
3798 }
3799
3800 if (new_base != old_base) {
3801 set_req(Compile::AliasIdxBot, new_base);
3802 // Don't use set_base_memory(new_base), because we need to update du.
3803 assert(base_memory() == new_base, "");
3804 progress = this;
3805 }
3806
3807 if( base_memory() == this ) {
3808 // a self cycle indicates this memory path is dead
3809 set_req(Compile::AliasIdxBot, empty_mem);
3810 }
3811
3812 // Resolve external cycles by calling Ideal on a MergeMem base_memory
3813 // Recursion must occur after the self cycle check above
3814 if( base_memory()->is_MergeMem() ) {
3815 MergeMemNode *new_mbase = base_memory()->as_MergeMem();
3816 Node *m = phase->transform(new_mbase); // Rollup any cycles
3817 if( m != NULL && (m->is_top() ||
3818 m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
3819 // propagate rollup of dead cycle to self
3820 set_req(Compile::AliasIdxBot, empty_mem);
3821 }
3822 }
3823
3824 if( base_memory() == empty_mem ) {
3825 progress = this;
3826 // Cut inputs during Parse phase only.
3827 // During Optimize phase a dead MergeMem node will be subsumed by Top.
3828 if( !can_reshape ) {
3829 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3830 if( in(i) != empty_mem ) { set_req(i, empty_mem); }
3831 }
3832 }
3833 }
3834
3835 if( !progress && base_memory()->is_Phi() && can_reshape ) {
3836 // Check if PhiNode::Ideal's "Split phis through memory merges"
3837 // transform should be attempted. Look for this->phi->this cycle.
3838 uint merge_width = req();
3839 if (merge_width > Compile::AliasIdxRaw) {
3840 PhiNode* phi = base_memory()->as_Phi();
3841 for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
3842 if (phi->in(i) == this) {
3843 phase->is_IterGVN()->_worklist.push(phi);
3844 break;
3845 }
3846 }
3847 }
3848 }
3849
3850 assert(progress || verify_sparse(), "please, no dups of base");
3851 return progress;
3852 }
3853
3854 //-------------------------set_base_memory-------------------------------------
3855 void MergeMemNode::set_base_memory(Node *new_base) {
3856 Node* empty_mem = empty_memory();
3857 set_req(Compile::AliasIdxBot, new_base);
3858 assert(memory_at(req()) == new_base, "must set default memory");
3859 // Clear out other occurrences of new_base:
3860 if (new_base != empty_mem) {
3861 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3862 if (in(i) == new_base) set_req(i, empty_mem);
3863 }
3864 }
3865 }
3866
3867 //------------------------------out_RegMask------------------------------------
3868 const RegMask &MergeMemNode::out_RegMask() const {
3869 return RegMask::Empty;
3870 }
3871
3872 //------------------------------dump_spec--------------------------------------
3873 #ifndef PRODUCT
3874 void MergeMemNode::dump_spec(outputStream *st) const {
3875 st->print(" {");
3876 Node* base_mem = base_memory();
3877 for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
3878 Node* mem = memory_at(i);
3879 if (mem == base_mem) { st->print(" -"); continue; }
3880 st->print( " N%d:", mem->_idx );
3881 Compile::current()->get_adr_type(i)->dump_on(st);
3882 }
3883 st->print(" }");
3884 }
3885 #endif // !PRODUCT
3886
3887
3888 #ifdef ASSERT
3889 static bool might_be_same(Node* a, Node* b) {
3890 if (a == b) return true;
3891 if (!(a->is_Phi() || b->is_Phi())) return false;
3892 // phis shift around during optimization
3893 return true; // pretty stupid...
3894 }
3895
3896 // verify a narrow slice (either incoming or outgoing)
3897 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
3898 if (!VerifyAliases) return; // don't bother to verify unless requested
3899 if (is_error_reported()) return; // muzzle asserts when debugging an error
3900 if (Node::in_dump()) return; // muzzle asserts when printing
3901 assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
3902 assert(n != NULL, "");
3903 // Elide intervening MergeMem's
3904 while (n->is_MergeMem()) {
3905 n = n->as_MergeMem()->memory_at(alias_idx);
3906 }
3907 Compile* C = Compile::current();
3908 const TypePtr* n_adr_type = n->adr_type();
3909 if (n == m->empty_memory()) {
3910 // Implicit copy of base_memory()
3911 } else if (n_adr_type != TypePtr::BOTTOM) {
3912 assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
3913 assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
3914 } else {
3915 // A few places like make_runtime_call "know" that VM calls are narrow,
3916 // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
3917 bool expected_wide_mem = false;
3918 if (n == m->base_memory()) {
3919 expected_wide_mem = true;
3920 } else if (alias_idx == Compile::AliasIdxRaw ||
3921 n == m->memory_at(Compile::AliasIdxRaw)) {
3922 expected_wide_mem = true;
3923 } else if (!C->alias_type(alias_idx)->is_rewritable()) {
3924 // memory can "leak through" calls on channels that
3925 // are write-once. Allow this also.
3926 expected_wide_mem = true;
3927 }
3928 assert(expected_wide_mem, "expected narrow slice replacement");
3929 }
3930 }
3931 #else // !ASSERT
3932 #define verify_memory_slice(m,i,n) (0) // PRODUCT version is no-op
3933 #endif
3934
3935
3936 //-----------------------------memory_at---------------------------------------
3937 Node* MergeMemNode::memory_at(uint alias_idx) const {
3938 assert(alias_idx >= Compile::AliasIdxRaw ||
3939 alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
3940 "must avoid base_memory and AliasIdxTop");
3941
3942 // Otherwise, it is a narrow slice.
3943 Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
3944 Compile *C = Compile::current();
3945 if (is_empty_memory(n)) {
3946 // the array is sparse; empty slots are the "top" node
3947 n = base_memory();
3948 assert(Node::in_dump()
3949 || n == NULL || n->bottom_type() == Type::TOP
3950 || n->adr_type() == TypePtr::BOTTOM
3951 || n->adr_type() == TypeRawPtr::BOTTOM
3952 || Compile::current()->AliasLevel() == 0,
3953 "must be a wide memory");
3954 // AliasLevel == 0 if we are organizing the memory states manually.
3955 // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
3956 } else {
3957 // make sure the stored slice is sane
3958 #ifdef ASSERT
3959 if (is_error_reported() || Node::in_dump()) {
3960 } else if (might_be_same(n, base_memory())) {
3961 // Give it a pass: It is a mostly harmless repetition of the base.
3962 // This can arise normally from node subsumption during optimization.
3963 } else {
3964 verify_memory_slice(this, alias_idx, n);
3965 }
3966 #endif
3967 }
3968 return n;
3969 }
3970
3971 //---------------------------set_memory_at-------------------------------------
3972 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
3973 verify_memory_slice(this, alias_idx, n);
3974 Node* empty_mem = empty_memory();
3975 if (n == base_memory()) n = empty_mem; // collapse default
3976 uint need_req = alias_idx+1;
3977 if (req() < need_req) {
3978 if (n == empty_mem) return; // already the default, so do not grow me
3979 // grow the sparse array
3980 do {
3981 add_req(empty_mem);
3982 } while (req() < need_req);
3983 }
3984 set_req( alias_idx, n );
3985 }
3986
3987
3988
3989 //--------------------------iteration_setup------------------------------------
3990 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
3991 if (other != NULL) {
3992 grow_to_match(other);
3993 // invariant: the finite support of mm2 is within mm->req()
3994 #ifdef ASSERT
3995 for (uint i = req(); i < other->req(); i++) {
3996 assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
3997 }
3998 #endif
3999 }
4000 // Replace spurious copies of base_memory by top.
4001 Node* base_mem = base_memory();
4002 if (base_mem != NULL && !base_mem->is_top()) {
4003 for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4004 if (in(i) == base_mem)
4005 set_req(i, empty_memory());
4006 }
4007 }
4008 }
4009
4010 //---------------------------grow_to_match-------------------------------------
4011 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4012 Node* empty_mem = empty_memory();
4013 assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4014 // look for the finite support of the other memory
4015 for (uint i = other->req(); --i >= req(); ) {
4016 if (other->in(i) != empty_mem) {
4017 uint new_len = i+1;
4018 while (req() < new_len) add_req(empty_mem);
4019 break;
4020 }
4021 }
4022 }
4023
4024 //---------------------------verify_sparse-------------------------------------
4025 #ifndef PRODUCT
4026 bool MergeMemNode::verify_sparse() const {
4027 assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4028 Node* base_mem = base_memory();
4029 // The following can happen in degenerate cases, since empty==top.
4030 if (is_empty_memory(base_mem)) return true;
4031 for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4032 assert(in(i) != NULL, "sane slice");
4033 if (in(i) == base_mem) return false; // should have been the sentinel value!
4034 }
4035 return true;
4036 }
4037
4038 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4039 Node* n;
4040 n = mm->in(idx);
4041 if (mem == n) return true; // might be empty_memory()
4042 n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4043 if (mem == n) return true;
4044 while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4045 if (mem == n) return true;
4046 if (n == NULL) break;
4047 }
4048 return false;
4049 }
4050 #endif // !PRODUCT