Mon, 24 Nov 2014 07:29:03 -0800
8058148: MaxNodeLimit and LiveNodeCountInliningCutoff
Reviewed-by: kvn, roland
1 /*
2 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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23 */
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/chaitin.hpp"
28 #include "opto/machnode.hpp"
30 // See if this register (or pairs, or vector) already contains the value.
31 static bool register_contains_value(Node* val, OptoReg::Name reg, int n_regs,
32 Node_List& value) {
33 for (int i = 0; i < n_regs; i++) {
34 OptoReg::Name nreg = OptoReg::add(reg,-i);
35 if (value[nreg] != val)
36 return false;
37 }
38 return true;
39 }
41 //---------------------------may_be_copy_of_callee-----------------------------
42 // Check to see if we can possibly be a copy of a callee-save value.
43 bool PhaseChaitin::may_be_copy_of_callee( Node *def ) const {
44 // Short circuit if there are no callee save registers
45 if (_matcher.number_of_saved_registers() == 0) return false;
47 // Expect only a spill-down and reload on exit for callee-save spills.
48 // Chains of copies cannot be deep.
49 // 5008997 - This is wishful thinking. Register allocator seems to
50 // be splitting live ranges for callee save registers to such
51 // an extent that in large methods the chains can be very long
52 // (50+). The conservative answer is to return true if we don't
53 // know as this prevents optimizations from occurring.
55 const int limit = 60;
56 int i;
57 for( i=0; i < limit; i++ ) {
58 if( def->is_Proj() && def->in(0)->is_Start() &&
59 _matcher.is_save_on_entry(lrgs(_lrg_map.live_range_id(def)).reg()))
60 return true; // Direct use of callee-save proj
61 if( def->is_Copy() ) // Copies carry value through
62 def = def->in(def->is_Copy());
63 else if( def->is_Phi() ) // Phis can merge it from any direction
64 def = def->in(1);
65 else
66 break;
67 guarantee(def != NULL, "must not resurrect dead copy");
68 }
69 // If we reached the end and didn't find a callee save proj
70 // then this may be a callee save proj so we return true
71 // as the conservative answer. If we didn't reach then end
72 // we must have discovered that it was not a callee save
73 // else we would have returned.
74 return i == limit;
75 }
77 //------------------------------yank-----------------------------------
78 // Helper function for yank_if_dead
79 int PhaseChaitin::yank( Node *old, Block *current_block, Node_List *value, Node_List *regnd ) {
80 int blk_adjust=0;
81 Block *oldb = _cfg.get_block_for_node(old);
82 oldb->find_remove(old);
83 // Count 1 if deleting an instruction from the current block
84 if (oldb == current_block) {
85 blk_adjust++;
86 }
87 _cfg.unmap_node_from_block(old);
88 OptoReg::Name old_reg = lrgs(_lrg_map.live_range_id(old)).reg();
89 if( regnd && (*regnd)[old_reg]==old ) { // Instruction is currently available?
90 value->map(old_reg,NULL); // Yank from value/regnd maps
91 regnd->map(old_reg,NULL); // This register's value is now unknown
92 }
93 return blk_adjust;
94 }
96 #ifdef ASSERT
97 static bool expected_yanked_node(Node *old, Node *orig_old) {
98 // This code is expected only next original nodes:
99 // - load from constant table node which may have next data input nodes:
100 // MachConstantBase, MachTemp, MachSpillCopy
101 // - Phi nodes that are considered Junk
102 // - load constant node which may have next data input nodes:
103 // MachTemp, MachSpillCopy
104 // - MachSpillCopy
105 // - MachProj and Copy dead nodes
106 if (old->is_MachSpillCopy()) {
107 return true;
108 } else if (old->is_Con()) {
109 return true;
110 } else if (old->is_MachProj()) { // Dead kills projection of Con node
111 return (old == orig_old);
112 } else if (old->is_Copy()) { // Dead copy of a callee-save value
113 return (old == orig_old);
114 } else if (old->is_MachTemp()) {
115 return orig_old->is_Con();
116 } else if (old->is_Phi()) { // Junk phi's
117 return true;
118 } else if (old->is_MachConstantBase()) {
119 return (orig_old->is_Con() && orig_old->is_MachConstant());
120 }
121 return false;
122 }
123 #endif
125 //------------------------------yank_if_dead-----------------------------------
126 // Removed edges from 'old'. Yank if dead. Return adjustment counts to
127 // iterators in the current block.
128 int PhaseChaitin::yank_if_dead_recurse(Node *old, Node *orig_old, Block *current_block,
129 Node_List *value, Node_List *regnd) {
130 int blk_adjust=0;
131 if (old->outcnt() == 0 && old != C->top()) {
132 #ifdef ASSERT
133 if (!expected_yanked_node(old, orig_old)) {
134 tty->print_cr("==============================================");
135 tty->print_cr("orig_old:");
136 orig_old->dump();
137 tty->print_cr("old:");
138 old->dump();
139 assert(false, "unexpected yanked node");
140 }
141 if (old->is_Con())
142 orig_old = old; // Reset to satisfy expected nodes checks.
143 #endif
144 blk_adjust += yank(old, current_block, value, regnd);
146 for (uint i = 1; i < old->req(); i++) {
147 Node* n = old->in(i);
148 if (n != NULL) {
149 old->set_req(i, NULL);
150 blk_adjust += yank_if_dead_recurse(n, orig_old, current_block, value, regnd);
151 }
152 }
153 // Disconnect control and remove precedence edges if any exist
154 old->disconnect_inputs(NULL, C);
155 }
156 return blk_adjust;
157 }
159 //------------------------------use_prior_register-----------------------------
160 // Use the prior value instead of the current value, in an effort to make
161 // the current value go dead. Return block iterator adjustment, in case
162 // we yank some instructions from this block.
163 int PhaseChaitin::use_prior_register( Node *n, uint idx, Node *def, Block *current_block, Node_List &value, Node_List ®nd ) {
164 // No effect?
165 if( def == n->in(idx) ) return 0;
166 // Def is currently dead and can be removed? Do not resurrect
167 if( def->outcnt() == 0 ) return 0;
169 // Not every pair of physical registers are assignment compatible,
170 // e.g. on sparc floating point registers are not assignable to integer
171 // registers.
172 const LRG &def_lrg = lrgs(_lrg_map.live_range_id(def));
173 OptoReg::Name def_reg = def_lrg.reg();
174 const RegMask &use_mask = n->in_RegMask(idx);
175 bool can_use = ( RegMask::can_represent(def_reg) ? (use_mask.Member(def_reg) != 0)
176 : (use_mask.is_AllStack() != 0));
177 if (!RegMask::is_vector(def->ideal_reg())) {
178 // Check for a copy to or from a misaligned pair.
179 // It is workaround for a sparc with misaligned pairs.
180 can_use = can_use && !use_mask.is_misaligned_pair() && !def_lrg.mask().is_misaligned_pair();
181 }
182 if (!can_use)
183 return 0;
185 // Capture the old def in case it goes dead...
186 Node *old = n->in(idx);
188 // Save-on-call copies can only be elided if the entire copy chain can go
189 // away, lest we get the same callee-save value alive in 2 locations at
190 // once. We check for the obvious trivial case here. Although it can
191 // sometimes be elided with cooperation outside our scope, here we will just
192 // miss the opportunity. :-(
193 if( may_be_copy_of_callee(def) ) {
194 if( old->outcnt() > 1 ) return 0; // We're the not last user
195 int idx = old->is_Copy();
196 assert( idx, "chain of copies being removed" );
197 Node *old2 = old->in(idx); // Chain of copies
198 if( old2->outcnt() > 1 ) return 0; // old is not the last user
199 int idx2 = old2->is_Copy();
200 if( !idx2 ) return 0; // Not a chain of 2 copies
201 if( def != old2->in(idx2) ) return 0; // Chain of exactly 2 copies
202 }
204 // Use the new def
205 n->set_req(idx,def);
206 _post_alloc++;
208 // Is old def now dead? We successfully yanked a copy?
209 return yank_if_dead(old,current_block,&value,®nd);
210 }
213 //------------------------------skip_copies------------------------------------
214 // Skip through any number of copies (that don't mod oop-i-ness)
215 Node *PhaseChaitin::skip_copies( Node *c ) {
216 int idx = c->is_Copy();
217 uint is_oop = lrgs(_lrg_map.live_range_id(c))._is_oop;
218 while (idx != 0) {
219 guarantee(c->in(idx) != NULL, "must not resurrect dead copy");
220 if (lrgs(_lrg_map.live_range_id(c->in(idx)))._is_oop != is_oop) {
221 break; // casting copy, not the same value
222 }
223 c = c->in(idx);
224 idx = c->is_Copy();
225 }
226 return c;
227 }
229 //------------------------------elide_copy-------------------------------------
230 // Remove (bypass) copies along Node n, edge k.
231 int PhaseChaitin::elide_copy( Node *n, int k, Block *current_block, Node_List &value, Node_List ®nd, bool can_change_regs ) {
232 int blk_adjust = 0;
234 uint nk_idx = _lrg_map.live_range_id(n->in(k));
235 OptoReg::Name nk_reg = lrgs(nk_idx).reg();
237 // Remove obvious same-register copies
238 Node *x = n->in(k);
239 int idx;
240 while( (idx=x->is_Copy()) != 0 ) {
241 Node *copy = x->in(idx);
242 guarantee(copy != NULL, "must not resurrect dead copy");
243 if(lrgs(_lrg_map.live_range_id(copy)).reg() != nk_reg) {
244 break;
245 }
246 blk_adjust += use_prior_register(n,k,copy,current_block,value,regnd);
247 if (n->in(k) != copy) {
248 break; // Failed for some cutout?
249 }
250 x = copy; // Progress, try again
251 }
253 // Phis and 2-address instructions cannot change registers so easily - their
254 // outputs must match their input.
255 if( !can_change_regs )
256 return blk_adjust; // Only check stupid copies!
258 // Loop backedges won't have a value-mapping yet
259 if( &value == NULL ) return blk_adjust;
261 // Skip through all copies to the _value_ being used. Do not change from
262 // int to pointer. This attempts to jump through a chain of copies, where
263 // intermediate copies might be illegal, i.e., value is stored down to stack
264 // then reloaded BUT survives in a register the whole way.
265 Node *val = skip_copies(n->in(k));
267 if (val == x && nk_idx != 0 &&
268 regnd[nk_reg] != NULL && regnd[nk_reg] != x &&
269 _lrg_map.live_range_id(x) == _lrg_map.live_range_id(regnd[nk_reg])) {
270 // When rematerialzing nodes and stretching lifetimes, the
271 // allocator will reuse the original def for multidef LRG instead
272 // of the current reaching def because it can't know it's safe to
273 // do so. After allocation completes if they are in the same LRG
274 // then it should use the current reaching def instead.
275 n->set_req(k, regnd[nk_reg]);
276 blk_adjust += yank_if_dead(val, current_block, &value, ®nd);
277 val = skip_copies(n->in(k));
278 }
280 if (val == x) return blk_adjust; // No progress?
282 int n_regs = RegMask::num_registers(val->ideal_reg());
283 uint val_idx = _lrg_map.live_range_id(val);
284 OptoReg::Name val_reg = lrgs(val_idx).reg();
286 // See if it happens to already be in the correct register!
287 // (either Phi's direct register, or the common case of the name
288 // never-clobbered original-def register)
289 if (register_contains_value(val, val_reg, n_regs, value)) {
290 blk_adjust += use_prior_register(n,k,regnd[val_reg],current_block,value,regnd);
291 if( n->in(k) == regnd[val_reg] ) // Success! Quit trying
292 return blk_adjust;
293 }
295 // See if we can skip the copy by changing registers. Don't change from
296 // using a register to using the stack unless we know we can remove a
297 // copy-load. Otherwise we might end up making a pile of Intel cisc-spill
298 // ops reading from memory instead of just loading once and using the
299 // register.
301 // Also handle duplicate copies here.
302 const Type *t = val->is_Con() ? val->bottom_type() : NULL;
304 // Scan all registers to see if this value is around already
305 for( uint reg = 0; reg < (uint)_max_reg; reg++ ) {
306 if (reg == (uint)nk_reg) {
307 // Found ourselves so check if there is only one user of this
308 // copy and keep on searching for a better copy if so.
309 bool ignore_self = true;
310 x = n->in(k);
311 DUIterator_Fast imax, i = x->fast_outs(imax);
312 Node* first = x->fast_out(i); i++;
313 while (i < imax && ignore_self) {
314 Node* use = x->fast_out(i); i++;
315 if (use != first) ignore_self = false;
316 }
317 if (ignore_self) continue;
318 }
320 Node *vv = value[reg];
321 if (n_regs > 1) { // Doubles and vectors check for aligned-adjacent set
322 uint last = (n_regs-1); // Looking for the last part of a set
323 if ((reg&last) != last) continue; // Wrong part of a set
324 if (!register_contains_value(vv, reg, n_regs, value)) continue; // Different value
325 }
326 if( vv == val || // Got a direct hit?
327 (t && vv && vv->bottom_type() == t && vv->is_Mach() &&
328 vv->as_Mach()->rule() == val->as_Mach()->rule()) ) { // Or same constant?
329 assert( !n->is_Phi(), "cannot change registers at a Phi so easily" );
330 if( OptoReg::is_stack(nk_reg) || // CISC-loading from stack OR
331 OptoReg::is_reg(reg) || // turning into a register use OR
332 regnd[reg]->outcnt()==1 ) { // last use of a spill-load turns into a CISC use
333 blk_adjust += use_prior_register(n,k,regnd[reg],current_block,value,regnd);
334 if( n->in(k) == regnd[reg] ) // Success! Quit trying
335 return blk_adjust;
336 } // End of if not degrading to a stack
337 } // End of if found value in another register
338 } // End of scan all machine registers
339 return blk_adjust;
340 }
343 //
344 // Check if nreg already contains the constant value val. Normal copy
345 // elimination doesn't doesn't work on constants because multiple
346 // nodes can represent the same constant so the type and rule of the
347 // MachNode must be checked to ensure equivalence.
348 //
349 bool PhaseChaitin::eliminate_copy_of_constant(Node* val, Node* n,
350 Block *current_block,
351 Node_List& value, Node_List& regnd,
352 OptoReg::Name nreg, OptoReg::Name nreg2) {
353 if (value[nreg] != val && val->is_Con() &&
354 value[nreg] != NULL && value[nreg]->is_Con() &&
355 (nreg2 == OptoReg::Bad || value[nreg] == value[nreg2]) &&
356 value[nreg]->bottom_type() == val->bottom_type() &&
357 value[nreg]->as_Mach()->rule() == val->as_Mach()->rule()) {
358 // This code assumes that two MachNodes representing constants
359 // which have the same rule and the same bottom type will produce
360 // identical effects into a register. This seems like it must be
361 // objectively true unless there are hidden inputs to the nodes
362 // but if that were to change this code would need to updated.
363 // Since they are equivalent the second one if redundant and can
364 // be removed.
365 //
366 // n will be replaced with the old value but n might have
367 // kills projections associated with it so remove them now so that
368 // yank_if_dead will be able to eliminate the copy once the uses
369 // have been transferred to the old[value].
370 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
371 Node* use = n->fast_out(i);
372 if (use->is_Proj() && use->outcnt() == 0) {
373 // Kill projections have no users and one input
374 use->set_req(0, C->top());
375 yank_if_dead(use, current_block, &value, ®nd);
376 --i; --imax;
377 }
378 }
379 _post_alloc++;
380 return true;
381 }
382 return false;
383 }
386 //------------------------------post_allocate_copy_removal---------------------
387 // Post-Allocation peephole copy removal. We do this in 1 pass over the
388 // basic blocks. We maintain a mapping of registers to Nodes (an array of
389 // Nodes indexed by machine register or stack slot number). NULL means that a
390 // register is not mapped to any Node. We can (want to have!) have several
391 // registers map to the same Node. We walk forward over the instructions
392 // updating the mapping as we go. At merge points we force a NULL if we have
393 // to merge 2 different Nodes into the same register. Phi functions will give
394 // us a new Node if there is a proper value merging. Since the blocks are
395 // arranged in some RPO, we will visit all parent blocks before visiting any
396 // successor blocks (except at loops).
397 //
398 // If we find a Copy we look to see if the Copy's source register is a stack
399 // slot and that value has already been loaded into some machine register; if
400 // so we use machine register directly. This turns a Load into a reg-reg
401 // Move. We also look for reloads of identical constants.
402 //
403 // When we see a use from a reg-reg Copy, we will attempt to use the copy's
404 // source directly and make the copy go dead.
405 void PhaseChaitin::post_allocate_copy_removal() {
406 NOT_PRODUCT( Compile::TracePhase t3("postAllocCopyRemoval", &_t_postAllocCopyRemoval, TimeCompiler); )
407 ResourceMark rm;
409 // Need a mapping from basic block Node_Lists. We need a Node_List to
410 // map from register number to value-producing Node.
411 Node_List **blk2value = NEW_RESOURCE_ARRAY( Node_List *, _cfg.number_of_blocks() + 1);
412 memset(blk2value, 0, sizeof(Node_List*) * (_cfg.number_of_blocks() + 1));
413 // Need a mapping from basic block Node_Lists. We need a Node_List to
414 // map from register number to register-defining Node.
415 Node_List **blk2regnd = NEW_RESOURCE_ARRAY( Node_List *, _cfg.number_of_blocks() + 1);
416 memset(blk2regnd, 0, sizeof(Node_List*) * (_cfg.number_of_blocks() + 1));
418 // We keep unused Node_Lists on a free_list to avoid wasting
419 // memory.
420 GrowableArray<Node_List*> free_list = GrowableArray<Node_List*>(16);
422 // For all blocks
423 for (uint i = 0; i < _cfg.number_of_blocks(); i++) {
424 uint j;
425 Block* block = _cfg.get_block(i);
427 // Count of Phis in block
428 uint phi_dex;
429 for (phi_dex = 1; phi_dex < block->number_of_nodes(); phi_dex++) {
430 Node* phi = block->get_node(phi_dex);
431 if (!phi->is_Phi()) {
432 break;
433 }
434 }
436 // If any predecessor has not been visited, we do not know the state
437 // of registers at the start. Check for this, while updating copies
438 // along Phi input edges
439 bool missing_some_inputs = false;
440 Block *freed = NULL;
441 for (j = 1; j < block->num_preds(); j++) {
442 Block* pb = _cfg.get_block_for_node(block->pred(j));
443 // Remove copies along phi edges
444 for (uint k = 1; k < phi_dex; k++) {
445 elide_copy(block->get_node(k), j, block, *blk2value[pb->_pre_order], *blk2regnd[pb->_pre_order], false);
446 }
447 if (blk2value[pb->_pre_order]) { // Have a mapping on this edge?
448 // See if this predecessor's mappings have been used by everybody
449 // who wants them. If so, free 'em.
450 uint k;
451 for (k = 0; k < pb->_num_succs; k++) {
452 Block* pbsucc = pb->_succs[k];
453 if (!blk2value[pbsucc->_pre_order] && pbsucc != block) {
454 break; // Found a future user
455 }
456 }
457 if (k >= pb->_num_succs) { // No more uses, free!
458 freed = pb; // Record last block freed
459 free_list.push(blk2value[pb->_pre_order]);
460 free_list.push(blk2regnd[pb->_pre_order]);
461 }
462 } else { // This block has unvisited (loopback) inputs
463 missing_some_inputs = true;
464 }
465 }
468 // Extract Node_List mappings. If 'freed' is non-zero, we just popped
469 // 'freed's blocks off the list
470 Node_List ®nd = *(free_list.is_empty() ? new Node_List() : free_list.pop());
471 Node_List &value = *(free_list.is_empty() ? new Node_List() : free_list.pop());
472 assert( !freed || blk2value[freed->_pre_order] == &value, "" );
473 value.map(_max_reg,NULL);
474 regnd.map(_max_reg,NULL);
475 // Set mappings as OUR mappings
476 blk2value[block->_pre_order] = &value;
477 blk2regnd[block->_pre_order] = ®nd;
479 // Initialize value & regnd for this block
480 if (missing_some_inputs) {
481 // Some predecessor has not yet been visited; zap map to empty
482 for (uint k = 0; k < (uint)_max_reg; k++) {
483 value.map(k,NULL);
484 regnd.map(k,NULL);
485 }
486 } else {
487 if( !freed ) { // Didn't get a freebie prior block
488 // Must clone some data
489 freed = _cfg.get_block_for_node(block->pred(1));
490 Node_List &f_value = *blk2value[freed->_pre_order];
491 Node_List &f_regnd = *blk2regnd[freed->_pre_order];
492 for( uint k = 0; k < (uint)_max_reg; k++ ) {
493 value.map(k,f_value[k]);
494 regnd.map(k,f_regnd[k]);
495 }
496 }
497 // Merge all inputs together, setting to NULL any conflicts.
498 for (j = 1; j < block->num_preds(); j++) {
499 Block* pb = _cfg.get_block_for_node(block->pred(j));
500 if (pb == freed) {
501 continue; // Did self already via freelist
502 }
503 Node_List &p_regnd = *blk2regnd[pb->_pre_order];
504 for( uint k = 0; k < (uint)_max_reg; k++ ) {
505 if( regnd[k] != p_regnd[k] ) { // Conflict on reaching defs?
506 value.map(k,NULL); // Then no value handy
507 regnd.map(k,NULL);
508 }
509 }
510 }
511 }
513 // For all Phi's
514 for (j = 1; j < phi_dex; j++) {
515 uint k;
516 Node *phi = block->get_node(j);
517 uint pidx = _lrg_map.live_range_id(phi);
518 OptoReg::Name preg = lrgs(_lrg_map.live_range_id(phi)).reg();
520 // Remove copies remaining on edges. Check for junk phi.
521 Node *u = NULL;
522 for (k = 1; k < phi->req(); k++) {
523 Node *x = phi->in(k);
524 if( phi != x && u != x ) // Found a different input
525 u = u ? NodeSentinel : x; // Capture unique input, or NodeSentinel for 2nd input
526 }
527 if (u != NodeSentinel) { // Junk Phi. Remove
528 phi->replace_by(u);
529 j -= yank_if_dead(phi, block, &value, ®nd);
530 phi_dex--;
531 continue;
532 }
533 // Note that if value[pidx] exists, then we merged no new values here
534 // and the phi is useless. This can happen even with the above phi
535 // removal for complex flows. I cannot keep the better known value here
536 // because locally the phi appears to define a new merged value. If I
537 // keep the better value then a copy of the phi, being unable to use the
538 // global flow analysis, can't "peek through" the phi to the original
539 // reaching value and so will act like it's defining a new value. This
540 // can lead to situations where some uses are from the old and some from
541 // the new values. Not illegal by itself but throws the over-strong
542 // assert in scheduling.
543 if( pidx ) {
544 value.map(preg,phi);
545 regnd.map(preg,phi);
546 int n_regs = RegMask::num_registers(phi->ideal_reg());
547 for (int l = 1; l < n_regs; l++) {
548 OptoReg::Name preg_lo = OptoReg::add(preg,-l);
549 value.map(preg_lo,phi);
550 regnd.map(preg_lo,phi);
551 }
552 }
553 }
555 // For all remaining instructions
556 for (j = phi_dex; j < block->number_of_nodes(); j++) {
557 Node* n = block->get_node(j);
559 if(n->outcnt() == 0 && // Dead?
560 n != C->top() && // (ignore TOP, it has no du info)
561 !n->is_Proj() ) { // fat-proj kills
562 j -= yank_if_dead(n, block, &value, ®nd);
563 continue;
564 }
566 // Improve reaching-def info. Occasionally post-alloc's liveness gives
567 // up (at loop backedges, because we aren't doing a full flow pass).
568 // The presence of a live use essentially asserts that the use's def is
569 // alive and well at the use (or else the allocator fubar'd). Take
570 // advantage of this info to set a reaching def for the use-reg.
571 uint k;
572 for (k = 1; k < n->req(); k++) {
573 Node *def = n->in(k); // n->in(k) is a USE; def is the DEF for this USE
574 guarantee(def != NULL, "no disconnected nodes at this point");
575 uint useidx = _lrg_map.live_range_id(def); // useidx is the live range index for this USE
577 if( useidx ) {
578 OptoReg::Name ureg = lrgs(useidx).reg();
579 if( !value[ureg] ) {
580 int idx; // Skip occasional useless copy
581 while( (idx=def->is_Copy()) != 0 &&
582 def->in(idx) != NULL && // NULL should not happen
583 ureg == lrgs(_lrg_map.live_range_id(def->in(idx))).reg())
584 def = def->in(idx);
585 Node *valdef = skip_copies(def); // tighten up val through non-useless copies
586 value.map(ureg,valdef); // record improved reaching-def info
587 regnd.map(ureg, def);
588 // Record other half of doubles
589 uint def_ideal_reg = def->ideal_reg();
590 int n_regs = RegMask::num_registers(def_ideal_reg);
591 for (int l = 1; l < n_regs; l++) {
592 OptoReg::Name ureg_lo = OptoReg::add(ureg,-l);
593 if (!value[ureg_lo] &&
594 (!RegMask::can_represent(ureg_lo) ||
595 lrgs(useidx).mask().Member(ureg_lo))) { // Nearly always adjacent
596 value.map(ureg_lo,valdef); // record improved reaching-def info
597 regnd.map(ureg_lo, def);
598 }
599 }
600 }
601 }
602 }
604 const uint two_adr = n->is_Mach() ? n->as_Mach()->two_adr() : 0;
606 // Remove copies along input edges
607 for (k = 1; k < n->req(); k++) {
608 j -= elide_copy(n, k, block, value, regnd, two_adr != k);
609 }
611 // Unallocated Nodes define no registers
612 uint lidx = _lrg_map.live_range_id(n);
613 if (!lidx) {
614 continue;
615 }
617 // Update the register defined by this instruction
618 OptoReg::Name nreg = lrgs(lidx).reg();
619 // Skip through all copies to the _value_ being defined.
620 // Do not change from int to pointer
621 Node *val = skip_copies(n);
623 // Clear out a dead definition before starting so that the
624 // elimination code doesn't have to guard against it. The
625 // definition could in fact be a kill projection with a count of
626 // 0 which is safe but since those are uninteresting for copy
627 // elimination just delete them as well.
628 if (regnd[nreg] != NULL && regnd[nreg]->outcnt() == 0) {
629 regnd.map(nreg, NULL);
630 value.map(nreg, NULL);
631 }
633 uint n_ideal_reg = n->ideal_reg();
634 int n_regs = RegMask::num_registers(n_ideal_reg);
635 if (n_regs == 1) {
636 // If Node 'n' does not change the value mapped by the register,
637 // then 'n' is a useless copy. Do not update the register->node
638 // mapping so 'n' will go dead.
639 if( value[nreg] != val ) {
640 if (eliminate_copy_of_constant(val, n, block, value, regnd, nreg, OptoReg::Bad)) {
641 j -= replace_and_yank_if_dead(n, nreg, block, value, regnd);
642 } else {
643 // Update the mapping: record new Node defined by the register
644 regnd.map(nreg,n);
645 // Update mapping for defined *value*, which is the defined
646 // Node after skipping all copies.
647 value.map(nreg,val);
648 }
649 } else if( !may_be_copy_of_callee(n) ) {
650 assert(n->is_Copy(), "");
651 j -= replace_and_yank_if_dead(n, nreg, block, value, regnd);
652 }
653 } else if (RegMask::is_vector(n_ideal_reg)) {
654 // If Node 'n' does not change the value mapped by the register,
655 // then 'n' is a useless copy. Do not update the register->node
656 // mapping so 'n' will go dead.
657 if (!register_contains_value(val, nreg, n_regs, value)) {
658 // Update the mapping: record new Node defined by the register
659 regnd.map(nreg,n);
660 // Update mapping for defined *value*, which is the defined
661 // Node after skipping all copies.
662 value.map(nreg,val);
663 for (int l = 1; l < n_regs; l++) {
664 OptoReg::Name nreg_lo = OptoReg::add(nreg,-l);
665 regnd.map(nreg_lo, n );
666 value.map(nreg_lo,val);
667 }
668 } else if (n->is_Copy()) {
669 // Note: vector can't be constant and can't be copy of calee.
670 j -= replace_and_yank_if_dead(n, nreg, block, value, regnd);
671 }
672 } else {
673 // If the value occupies a register pair, record same info
674 // in both registers.
675 OptoReg::Name nreg_lo = OptoReg::add(nreg,-1);
676 if( RegMask::can_represent(nreg_lo) && // Either a spill slot, or
677 !lrgs(lidx).mask().Member(nreg_lo) ) { // Nearly always adjacent
678 // Sparc occasionally has non-adjacent pairs.
679 // Find the actual other value
680 RegMask tmp = lrgs(lidx).mask();
681 tmp.Remove(nreg);
682 nreg_lo = tmp.find_first_elem();
683 }
684 if (value[nreg] != val || value[nreg_lo] != val) {
685 if (eliminate_copy_of_constant(val, n, block, value, regnd, nreg, nreg_lo)) {
686 j -= replace_and_yank_if_dead(n, nreg, block, value, regnd);
687 } else {
688 regnd.map(nreg , n );
689 regnd.map(nreg_lo, n );
690 value.map(nreg ,val);
691 value.map(nreg_lo,val);
692 }
693 } else if (!may_be_copy_of_callee(n)) {
694 assert(n->is_Copy(), "");
695 j -= replace_and_yank_if_dead(n, nreg, block, value, regnd);
696 }
697 }
699 // Fat projections kill many registers
700 if( n_ideal_reg == MachProjNode::fat_proj ) {
701 RegMask rm = n->out_RegMask();
702 // wow, what an expensive iterator...
703 nreg = rm.find_first_elem();
704 while( OptoReg::is_valid(nreg)) {
705 rm.Remove(nreg);
706 value.map(nreg,n);
707 regnd.map(nreg,n);
708 nreg = rm.find_first_elem();
709 }
710 }
712 } // End of for all instructions in the block
714 } // End for all blocks
715 }