1 /*
2 * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/chaitin.hpp"
28 #include "opto/machnode.hpp"
29
30 // see if this register kind does not requires two registers
31 static bool is_single_register(uint x) {
32 #ifdef _LP64
33 return (x != Op_RegD && x != Op_RegL && x != Op_RegP);
34 #else
35 return (x != Op_RegD && x != Op_RegL);
36 #endif
37 }
38
39 //---------------------------may_be_copy_of_callee-----------------------------
40 // Check to see if we can possibly be a copy of a callee-save value.
41 bool PhaseChaitin::may_be_copy_of_callee( Node *def ) const {
42 // Short circuit if there are no callee save registers
43 if (_matcher.number_of_saved_registers() == 0) return false;
44
45 // Expect only a spill-down and reload on exit for callee-save spills.
46 // Chains of copies cannot be deep.
47 // 5008997 - This is wishful thinking. Register allocator seems to
48 // be splitting live ranges for callee save registers to such
49 // an extent that in large methods the chains can be very long
50 // (50+). The conservative answer is to return true if we don't
51 // know as this prevents optimizations from occurring.
52
53 const int limit = 60;
54 int i;
55 for( i=0; i < limit; i++ ) {
56 if( def->is_Proj() && def->in(0)->is_Start() &&
150 }
151
152 //------------------------------use_prior_register-----------------------------
153 // Use the prior value instead of the current value, in an effort to make
154 // the current value go dead. Return block iterator adjustment, in case
155 // we yank some instructions from this block.
156 int PhaseChaitin::use_prior_register( Node *n, uint idx, Node *def, Block *current_block, Node_List &value, Node_List ®nd ) {
157 // No effect?
158 if( def == n->in(idx) ) return 0;
159 // Def is currently dead and can be removed? Do not resurrect
160 if( def->outcnt() == 0 ) return 0;
161
162 // Not every pair of physical registers are assignment compatible,
163 // e.g. on sparc floating point registers are not assignable to integer
164 // registers.
165 const LRG &def_lrg = lrgs(n2lidx(def));
166 OptoReg::Name def_reg = def_lrg.reg();
167 const RegMask &use_mask = n->in_RegMask(idx);
168 bool can_use = ( RegMask::can_represent(def_reg) ? (use_mask.Member(def_reg) != 0)
169 : (use_mask.is_AllStack() != 0));
170 // Check for a copy to or from a misaligned pair.
171 can_use = can_use && !use_mask.is_misaligned_Pair() && !def_lrg.mask().is_misaligned_Pair();
172
173 if (!can_use)
174 return 0;
175
176 // Capture the old def in case it goes dead...
177 Node *old = n->in(idx);
178
179 // Save-on-call copies can only be elided if the entire copy chain can go
180 // away, lest we get the same callee-save value alive in 2 locations at
181 // once. We check for the obvious trivial case here. Although it can
182 // sometimes be elided with cooperation outside our scope, here we will just
183 // miss the opportunity. :-(
184 if( may_be_copy_of_callee(def) ) {
185 if( old->outcnt() > 1 ) return 0; // We're the not last user
186 int idx = old->is_Copy();
187 assert( idx, "chain of copies being removed" );
188 Node *old2 = old->in(idx); // Chain of copies
189 if( old2->outcnt() > 1 ) return 0; // old is not the last user
190 int idx2 = old2->is_Copy();
191 if( !idx2 ) return 0; // Not a chain of 2 copies
192 if( def != old2->in(idx2) ) return 0; // Chain of exactly 2 copies
246
247 // Skip through all copies to the _value_ being used. Do not change from
248 // int to pointer. This attempts to jump through a chain of copies, where
249 // intermediate copies might be illegal, i.e., value is stored down to stack
250 // then reloaded BUT survives in a register the whole way.
251 Node *val = skip_copies(n->in(k));
252
253 if (val == x && nk_idx != 0 &&
254 regnd[nk_reg] != NULL && regnd[nk_reg] != x &&
255 n2lidx(x) == n2lidx(regnd[nk_reg])) {
256 // When rematerialzing nodes and stretching lifetimes, the
257 // allocator will reuse the original def for multidef LRG instead
258 // of the current reaching def because it can't know it's safe to
259 // do so. After allocation completes if they are in the same LRG
260 // then it should use the current reaching def instead.
261 n->set_req(k, regnd[nk_reg]);
262 blk_adjust += yank_if_dead(val, current_block, &value, ®nd);
263 val = skip_copies(n->in(k));
264 }
265
266 if( val == x ) return blk_adjust; // No progress?
267
268 bool single = is_single_register(val->ideal_reg());
269 uint val_idx = n2lidx(val);
270 OptoReg::Name val_reg = lrgs(val_idx).reg();
271
272 // See if it happens to already be in the correct register!
273 // (either Phi's direct register, or the common case of the name
274 // never-clobbered original-def register)
275 if( value[val_reg] == val &&
276 // Doubles check both halves
277 ( single || value[val_reg-1] == val ) ) {
278 blk_adjust += use_prior_register(n,k,regnd[val_reg],current_block,value,regnd);
279 if( n->in(k) == regnd[val_reg] ) // Success! Quit trying
280 return blk_adjust;
281 }
282
283 // See if we can skip the copy by changing registers. Don't change from
284 // using a register to using the stack unless we know we can remove a
285 // copy-load. Otherwise we might end up making a pile of Intel cisc-spill
286 // ops reading from memory instead of just loading once and using the
287 // register.
288
289 // Also handle duplicate copies here.
290 const Type *t = val->is_Con() ? val->bottom_type() : NULL;
291
292 // Scan all registers to see if this value is around already
293 for( uint reg = 0; reg < (uint)_max_reg; reg++ ) {
294 if (reg == (uint)nk_reg) {
295 // Found ourselves so check if there is only one user of this
296 // copy and keep on searching for a better copy if so.
297 bool ignore_self = true;
298 x = n->in(k);
299 DUIterator_Fast imax, i = x->fast_outs(imax);
300 Node* first = x->fast_out(i); i++;
301 while (i < imax && ignore_self) {
302 Node* use = x->fast_out(i); i++;
303 if (use != first) ignore_self = false;
304 }
305 if (ignore_self) continue;
306 }
307
308 Node *vv = value[reg];
309 if( !single ) { // Doubles check for aligned-adjacent pair
310 if( (reg&1)==0 ) continue; // Wrong half of a pair
311 if( vv != value[reg-1] ) continue; // Not a complete pair
312 }
313 if( vv == val || // Got a direct hit?
314 (t && vv && vv->bottom_type() == t && vv->is_Mach() &&
315 vv->as_Mach()->rule() == val->as_Mach()->rule()) ) { // Or same constant?
316 assert( !n->is_Phi(), "cannot change registers at a Phi so easily" );
317 if( OptoReg::is_stack(nk_reg) || // CISC-loading from stack OR
318 OptoReg::is_reg(reg) || // turning into a register use OR
319 regnd[reg]->outcnt()==1 ) { // last use of a spill-load turns into a CISC use
320 blk_adjust += use_prior_register(n,k,regnd[reg],current_block,value,regnd);
321 if( n->in(k) == regnd[reg] ) // Success! Quit trying
322 return blk_adjust;
323 } // End of if not degrading to a stack
324 } // End of if found value in another register
325 } // End of scan all machine registers
326 return blk_adjust;
327 }
328
329
509 if( u != NodeSentinel ) { // Junk Phi. Remove
510 b->_nodes.remove(j--); phi_dex--;
511 _cfg._bbs.map(phi->_idx,NULL);
512 phi->replace_by(u);
513 phi->disconnect_inputs(NULL);
514 continue;
515 }
516 // Note that if value[pidx] exists, then we merged no new values here
517 // and the phi is useless. This can happen even with the above phi
518 // removal for complex flows. I cannot keep the better known value here
519 // because locally the phi appears to define a new merged value. If I
520 // keep the better value then a copy of the phi, being unable to use the
521 // global flow analysis, can't "peek through" the phi to the original
522 // reaching value and so will act like it's defining a new value. This
523 // can lead to situations where some uses are from the old and some from
524 // the new values. Not illegal by itself but throws the over-strong
525 // assert in scheduling.
526 if( pidx ) {
527 value.map(preg,phi);
528 regnd.map(preg,phi);
529 OptoReg::Name preg_lo = OptoReg::add(preg,-1);
530 if( !is_single_register(phi->ideal_reg()) ) {
531 value.map(preg_lo,phi);
532 regnd.map(preg_lo,phi);
533 }
534 }
535 }
536
537 // For all remaining instructions
538 for( j = phi_dex; j < b->_nodes.size(); j++ ) {
539 Node *n = b->_nodes[j];
540
541 if( n->outcnt() == 0 && // Dead?
542 n != C->top() && // (ignore TOP, it has no du info)
543 !n->is_Proj() ) { // fat-proj kills
544 j -= yank_if_dead(n,b,&value,®nd);
545 continue;
546 }
547
548 // Improve reaching-def info. Occasionally post-alloc's liveness gives
549 // up (at loop backedges, because we aren't doing a full flow pass).
550 // The presence of a live use essentially asserts that the use's def is
551 // alive and well at the use (or else the allocator fubar'd). Take
552 // advantage of this info to set a reaching def for the use-reg.
553 uint k;
554 for( k = 1; k < n->req(); k++ ) {
555 Node *def = n->in(k); // n->in(k) is a USE; def is the DEF for this USE
556 guarantee(def != NULL, "no disconnected nodes at this point");
557 uint useidx = n2lidx(def); // useidx is the live range index for this USE
558
559 if( useidx ) {
560 OptoReg::Name ureg = lrgs(useidx).reg();
561 if( !value[ureg] ) {
562 int idx; // Skip occasional useless copy
563 while( (idx=def->is_Copy()) != 0 &&
564 def->in(idx) != NULL && // NULL should not happen
565 ureg == lrgs(n2lidx(def->in(idx))).reg() )
566 def = def->in(idx);
567 Node *valdef = skip_copies(def); // tighten up val through non-useless copies
568 value.map(ureg,valdef); // record improved reaching-def info
569 regnd.map(ureg, def);
570 // Record other half of doubles
571 OptoReg::Name ureg_lo = OptoReg::add(ureg,-1);
572 if( !is_single_register(def->ideal_reg()) &&
573 ( !RegMask::can_represent(ureg_lo) ||
574 lrgs(useidx).mask().Member(ureg_lo) ) && // Nearly always adjacent
575 !value[ureg_lo] ) {
576 value.map(ureg_lo,valdef); // record improved reaching-def info
577 regnd.map(ureg_lo, def);
578 }
579 }
580 }
581 }
582
583 const uint two_adr = n->is_Mach() ? n->as_Mach()->two_adr() : 0;
584
585 // Remove copies along input edges
586 for( k = 1; k < n->req(); k++ )
587 j -= elide_copy( n, k, b, value, regnd, two_adr!=k );
588
589 // Unallocated Nodes define no registers
590 uint lidx = n2lidx(n);
591 if( !lidx ) continue;
592
593 // Update the register defined by this instruction
594 OptoReg::Name nreg = lrgs(lidx).reg();
595 // Skip through all copies to the _value_ being defined.
596 // Do not change from int to pointer
597 Node *val = skip_copies(n);
598
599 // Clear out a dead definition before starting so that the
600 // elimination code doesn't have to guard against it. The
601 // definition could in fact be a kill projection with a count of
602 // 0 which is safe but since those are uninteresting for copy
603 // elimination just delete them as well.
604 if (regnd[nreg] != NULL && regnd[nreg]->outcnt() == 0) {
605 regnd.map(nreg, NULL);
606 value.map(nreg, NULL);
607 }
608
609 uint n_ideal_reg = n->ideal_reg();
610 if( is_single_register(n_ideal_reg) ) {
611 // If Node 'n' does not change the value mapped by the register,
612 // then 'n' is a useless copy. Do not update the register->node
613 // mapping so 'n' will go dead.
614 if( value[nreg] != val ) {
615 if (eliminate_copy_of_constant(val, n, b, value, regnd, nreg, OptoReg::Bad)) {
616 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
617 } else {
618 // Update the mapping: record new Node defined by the register
619 regnd.map(nreg,n);
620 // Update mapping for defined *value*, which is the defined
621 // Node after skipping all copies.
622 value.map(nreg,val);
623 }
624 } else if( !may_be_copy_of_callee(n) ) {
625 assert( n->is_Copy(), "" );
626 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
627 }
628 } else {
629 // If the value occupies a register pair, record same info
630 // in both registers.
631 OptoReg::Name nreg_lo = OptoReg::add(nreg,-1);
632 if( RegMask::can_represent(nreg_lo) && // Either a spill slot, or
633 !lrgs(lidx).mask().Member(nreg_lo) ) { // Nearly always adjacent
634 // Sparc occasionally has non-adjacent pairs.
635 // Find the actual other value
636 RegMask tmp = lrgs(lidx).mask();
637 tmp.Remove(nreg);
638 nreg_lo = tmp.find_first_elem();
639 }
640 if( value[nreg] != val || value[nreg_lo] != val ) {
641 if (eliminate_copy_of_constant(val, n, b, value, regnd, nreg, nreg_lo)) {
642 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
643 } else {
644 regnd.map(nreg , n );
645 regnd.map(nreg_lo, n );
646 value.map(nreg ,val);
647 value.map(nreg_lo,val);
|
1 /*
2 * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/chaitin.hpp"
28 #include "opto/machnode.hpp"
29
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 }
40
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;
46
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.
54
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() &&
152 }
153
154 //------------------------------use_prior_register-----------------------------
155 // Use the prior value instead of the current value, in an effort to make
156 // the current value go dead. Return block iterator adjustment, in case
157 // we yank some instructions from this block.
158 int PhaseChaitin::use_prior_register( Node *n, uint idx, Node *def, Block *current_block, Node_List &value, Node_List ®nd ) {
159 // No effect?
160 if( def == n->in(idx) ) return 0;
161 // Def is currently dead and can be removed? Do not resurrect
162 if( def->outcnt() == 0 ) return 0;
163
164 // Not every pair of physical registers are assignment compatible,
165 // e.g. on sparc floating point registers are not assignable to integer
166 // registers.
167 const LRG &def_lrg = lrgs(n2lidx(def));
168 OptoReg::Name def_reg = def_lrg.reg();
169 const RegMask &use_mask = n->in_RegMask(idx);
170 bool can_use = ( RegMask::can_represent(def_reg) ? (use_mask.Member(def_reg) != 0)
171 : (use_mask.is_AllStack() != 0));
172 if (!RegMask::is_vector(def->ideal_reg())) {
173 // Check for a copy to or from a misaligned pair.
174 // It is workaround for a sparc with misaligned pairs.
175 can_use = can_use && !use_mask.is_misaligned_pair() && !def_lrg.mask().is_misaligned_pair();
176 }
177 if (!can_use)
178 return 0;
179
180 // Capture the old def in case it goes dead...
181 Node *old = n->in(idx);
182
183 // Save-on-call copies can only be elided if the entire copy chain can go
184 // away, lest we get the same callee-save value alive in 2 locations at
185 // once. We check for the obvious trivial case here. Although it can
186 // sometimes be elided with cooperation outside our scope, here we will just
187 // miss the opportunity. :-(
188 if( may_be_copy_of_callee(def) ) {
189 if( old->outcnt() > 1 ) return 0; // We're the not last user
190 int idx = old->is_Copy();
191 assert( idx, "chain of copies being removed" );
192 Node *old2 = old->in(idx); // Chain of copies
193 if( old2->outcnt() > 1 ) return 0; // old is not the last user
194 int idx2 = old2->is_Copy();
195 if( !idx2 ) return 0; // Not a chain of 2 copies
196 if( def != old2->in(idx2) ) return 0; // Chain of exactly 2 copies
250
251 // Skip through all copies to the _value_ being used. Do not change from
252 // int to pointer. This attempts to jump through a chain of copies, where
253 // intermediate copies might be illegal, i.e., value is stored down to stack
254 // then reloaded BUT survives in a register the whole way.
255 Node *val = skip_copies(n->in(k));
256
257 if (val == x && nk_idx != 0 &&
258 regnd[nk_reg] != NULL && regnd[nk_reg] != x &&
259 n2lidx(x) == n2lidx(regnd[nk_reg])) {
260 // When rematerialzing nodes and stretching lifetimes, the
261 // allocator will reuse the original def for multidef LRG instead
262 // of the current reaching def because it can't know it's safe to
263 // do so. After allocation completes if they are in the same LRG
264 // then it should use the current reaching def instead.
265 n->set_req(k, regnd[nk_reg]);
266 blk_adjust += yank_if_dead(val, current_block, &value, ®nd);
267 val = skip_copies(n->in(k));
268 }
269
270 if (val == x) return blk_adjust; // No progress?
271
272 int n_regs = RegMask::num_registers(val->ideal_reg());
273 uint val_idx = n2lidx(val);
274 OptoReg::Name val_reg = lrgs(val_idx).reg();
275
276 // See if it happens to already be in the correct register!
277 // (either Phi's direct register, or the common case of the name
278 // never-clobbered original-def register)
279 if (register_contains_value(val, val_reg, n_regs, value)) {
280 blk_adjust += use_prior_register(n,k,regnd[val_reg],current_block,value,regnd);
281 if( n->in(k) == regnd[val_reg] ) // Success! Quit trying
282 return blk_adjust;
283 }
284
285 // See if we can skip the copy by changing registers. Don't change from
286 // using a register to using the stack unless we know we can remove a
287 // copy-load. Otherwise we might end up making a pile of Intel cisc-spill
288 // ops reading from memory instead of just loading once and using the
289 // register.
290
291 // Also handle duplicate copies here.
292 const Type *t = val->is_Con() ? val->bottom_type() : NULL;
293
294 // Scan all registers to see if this value is around already
295 for( uint reg = 0; reg < (uint)_max_reg; reg++ ) {
296 if (reg == (uint)nk_reg) {
297 // Found ourselves so check if there is only one user of this
298 // copy and keep on searching for a better copy if so.
299 bool ignore_self = true;
300 x = n->in(k);
301 DUIterator_Fast imax, i = x->fast_outs(imax);
302 Node* first = x->fast_out(i); i++;
303 while (i < imax && ignore_self) {
304 Node* use = x->fast_out(i); i++;
305 if (use != first) ignore_self = false;
306 }
307 if (ignore_self) continue;
308 }
309
310 Node *vv = value[reg];
311 if (n_regs > 1) { // Doubles check for aligned-adjacent pair
312 if( (reg&1)==0 ) continue; // Wrong half of a pair
313 if( vv != value[reg-1] ) continue; // Not a complete pair
314 }
315 if( vv == val || // Got a direct hit?
316 (t && vv && vv->bottom_type() == t && vv->is_Mach() &&
317 vv->as_Mach()->rule() == val->as_Mach()->rule()) ) { // Or same constant?
318 assert( !n->is_Phi(), "cannot change registers at a Phi so easily" );
319 if( OptoReg::is_stack(nk_reg) || // CISC-loading from stack OR
320 OptoReg::is_reg(reg) || // turning into a register use OR
321 regnd[reg]->outcnt()==1 ) { // last use of a spill-load turns into a CISC use
322 blk_adjust += use_prior_register(n,k,regnd[reg],current_block,value,regnd);
323 if( n->in(k) == regnd[reg] ) // Success! Quit trying
324 return blk_adjust;
325 } // End of if not degrading to a stack
326 } // End of if found value in another register
327 } // End of scan all machine registers
328 return blk_adjust;
329 }
330
331
511 if( u != NodeSentinel ) { // Junk Phi. Remove
512 b->_nodes.remove(j--); phi_dex--;
513 _cfg._bbs.map(phi->_idx,NULL);
514 phi->replace_by(u);
515 phi->disconnect_inputs(NULL);
516 continue;
517 }
518 // Note that if value[pidx] exists, then we merged no new values here
519 // and the phi is useless. This can happen even with the above phi
520 // removal for complex flows. I cannot keep the better known value here
521 // because locally the phi appears to define a new merged value. If I
522 // keep the better value then a copy of the phi, being unable to use the
523 // global flow analysis, can't "peek through" the phi to the original
524 // reaching value and so will act like it's defining a new value. This
525 // can lead to situations where some uses are from the old and some from
526 // the new values. Not illegal by itself but throws the over-strong
527 // assert in scheduling.
528 if( pidx ) {
529 value.map(preg,phi);
530 regnd.map(preg,phi);
531 int n_regs = RegMask::num_registers(phi->ideal_reg());
532 for (int l = 1; l < n_regs; l++) {
533 OptoReg::Name preg_lo = OptoReg::add(preg,-l);
534 value.map(preg_lo,phi);
535 regnd.map(preg_lo,phi);
536 }
537 }
538 }
539
540 // For all remaining instructions
541 for( j = phi_dex; j < b->_nodes.size(); j++ ) {
542 Node *n = b->_nodes[j];
543
544 if( n->outcnt() == 0 && // Dead?
545 n != C->top() && // (ignore TOP, it has no du info)
546 !n->is_Proj() ) { // fat-proj kills
547 j -= yank_if_dead(n,b,&value,®nd);
548 continue;
549 }
550
551 // Improve reaching-def info. Occasionally post-alloc's liveness gives
552 // up (at loop backedges, because we aren't doing a full flow pass).
553 // The presence of a live use essentially asserts that the use's def is
554 // alive and well at the use (or else the allocator fubar'd). Take
555 // advantage of this info to set a reaching def for the use-reg.
556 uint k;
557 for( k = 1; k < n->req(); k++ ) {
558 Node *def = n->in(k); // n->in(k) is a USE; def is the DEF for this USE
559 guarantee(def != NULL, "no disconnected nodes at this point");
560 uint useidx = n2lidx(def); // useidx is the live range index for this USE
561
562 if( useidx ) {
563 OptoReg::Name ureg = lrgs(useidx).reg();
564 if( !value[ureg] ) {
565 int idx; // Skip occasional useless copy
566 while( (idx=def->is_Copy()) != 0 &&
567 def->in(idx) != NULL && // NULL should not happen
568 ureg == lrgs(n2lidx(def->in(idx))).reg() )
569 def = def->in(idx);
570 Node *valdef = skip_copies(def); // tighten up val through non-useless copies
571 value.map(ureg,valdef); // record improved reaching-def info
572 regnd.map(ureg, def);
573 // Record other half of doubles
574 uint def_ideal_reg = def->ideal_reg();
575 int n_regs = RegMask::num_registers(def_ideal_reg);
576 bool is_vec = RegMask::is_vector(def_ideal_reg);
577 for (int l = 1; l < n_regs; l++) {
578 OptoReg::Name ureg_lo = OptoReg::add(ureg,-l);
579 if (!value[ureg_lo] &&
580 (!RegMask::can_represent(ureg_lo) ||
581 lrgs(useidx).mask().Member(ureg_lo))) { // Nearly always adjacent
582 value.map(ureg_lo,valdef); // record improved reaching-def info
583 regnd.map(ureg_lo, def);
584 }
585 }
586 }
587 }
588 }
589
590 const uint two_adr = n->is_Mach() ? n->as_Mach()->two_adr() : 0;
591
592 // Remove copies along input edges
593 for( k = 1; k < n->req(); k++ )
594 j -= elide_copy( n, k, b, value, regnd, two_adr!=k );
595
596 // Unallocated Nodes define no registers
597 uint lidx = n2lidx(n);
598 if( !lidx ) continue;
599
600 // Update the register defined by this instruction
601 OptoReg::Name nreg = lrgs(lidx).reg();
602 // Skip through all copies to the _value_ being defined.
603 // Do not change from int to pointer
604 Node *val = skip_copies(n);
605
606 // Clear out a dead definition before starting so that the
607 // elimination code doesn't have to guard against it. The
608 // definition could in fact be a kill projection with a count of
609 // 0 which is safe but since those are uninteresting for copy
610 // elimination just delete them as well.
611 if (regnd[nreg] != NULL && regnd[nreg]->outcnt() == 0) {
612 regnd.map(nreg, NULL);
613 value.map(nreg, NULL);
614 }
615
616 uint n_ideal_reg = n->ideal_reg();
617 int n_regs = RegMask::num_registers(n_ideal_reg);
618 if (n_regs == 1) {
619 // If Node 'n' does not change the value mapped by the register,
620 // then 'n' is a useless copy. Do not update the register->node
621 // mapping so 'n' will go dead.
622 if( value[nreg] != val ) {
623 if (eliminate_copy_of_constant(val, n, b, value, regnd, nreg, OptoReg::Bad)) {
624 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
625 } else {
626 // Update the mapping: record new Node defined by the register
627 regnd.map(nreg,n);
628 // Update mapping for defined *value*, which is the defined
629 // Node after skipping all copies.
630 value.map(nreg,val);
631 }
632 } else if( !may_be_copy_of_callee(n) ) {
633 assert( n->is_Copy(), "" );
634 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
635 }
636 } else if (RegMask::is_vector(n_ideal_reg)) {
637 // If Node 'n' does not change the value mapped by the register,
638 // then 'n' is a useless copy. Do not update the register->node
639 // mapping so 'n' will go dead.
640 if (!register_contains_value(val, nreg, n_regs, value)) {
641 // Update the mapping: record new Node defined by the register
642 regnd.map(nreg,n);
643 // Update mapping for defined *value*, which is the defined
644 // Node after skipping all copies.
645 value.map(nreg,val);
646 for (int l = 1; l < n_regs; l++) {
647 OptoReg::Name nreg_lo = OptoReg::add(nreg,-l);
648 regnd.map(nreg_lo, n );
649 value.map(nreg_lo,val);
650 }
651 } else if (n->is_Copy()) {
652 // Note: vector can't be constant and can't be copy of calee.
653 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
654 }
655 } else {
656 // If the value occupies a register pair, record same info
657 // in both registers.
658 OptoReg::Name nreg_lo = OptoReg::add(nreg,-1);
659 if( RegMask::can_represent(nreg_lo) && // Either a spill slot, or
660 !lrgs(lidx).mask().Member(nreg_lo) ) { // Nearly always adjacent
661 // Sparc occasionally has non-adjacent pairs.
662 // Find the actual other value
663 RegMask tmp = lrgs(lidx).mask();
664 tmp.Remove(nreg);
665 nreg_lo = tmp.find_first_elem();
666 }
667 if( value[nreg] != val || value[nreg_lo] != val ) {
668 if (eliminate_copy_of_constant(val, n, b, value, regnd, nreg, nreg_lo)) {
669 j -= replace_and_yank_if_dead(n, nreg, b, value, regnd);
670 } else {
671 regnd.map(nreg , n );
672 regnd.map(nreg_lo, n );
673 value.map(nreg ,val);
674 value.map(nreg_lo,val);
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